// SPDX-License-Identifier: GPL-2.0
/*
 *  kernel/cpuset.c
 *
 *  Processor and Memory placement constraints for sets of tasks.
 *
 *  Copyright (C) 2003 BULL SA.
 *  Copyright (C) 2004-2007 Silicon Graphics, Inc.
 *  Copyright (C) 2006 Google, Inc
 *
 *  Portions derived from Patrick Mochel's sysfs code.
 *  sysfs is Copyright (c) 2001-3 Patrick Mochel
 *
 *  2003-10-10 Written by Simon Derr.
 *  2003-10-22 Updates by Stephen Hemminger.
 *  2004 May-July Rework by Paul Jackson.
 *  2006 Rework by Paul Menage to use generic cgroups
 *  2008 Rework of the scheduler domains and CPU hotplug handling
 *       by Max Krasnyansky
 */
#include "cpuset-internal.h"

#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/mempolicy.h>
#include <linux/mm.h>
#include <linux/memory.h>
#include <linux/rcupdate.h>
#include <linux/sched.h>
#include <linux/sched/deadline.h>
#include <linux/sched/mm.h>
#include <linux/sched/task.h>
#include <linux/security.h>
#include <linux/oom.h>
#include <linux/sched/isolation.h>
#include <linux/wait.h>
#include <linux/workqueue.h>
#include <linux/task_work.h>

DEFINE_STATIC_KEY_FALSE(cpusets_pre_enable_key);
DEFINE_STATIC_KEY_FALSE(cpusets_enabled_key);

/*
 * There could be abnormal cpuset configurations for cpu or memory
 * node binding, add this key to provide a quick low-cost judgment
 * of the situation.
 */
DEFINE_STATIC_KEY_FALSE(cpusets_insane_config_key);

static const char * const perr_strings[] = {
        [PERR_INVCPUS]   = "Invalid cpu list in cpuset.cpus.exclusive",
        [PERR_INVPARENT] = "Parent is an invalid partition root",
        [PERR_NOTPART]   = "Parent is not a partition root",
        [PERR_NOTEXCL]   = "Cpu list in cpuset.cpus not exclusive",
        [PERR_NOCPUS]    = "Parent unable to distribute cpu downstream",
        [PERR_HOTPLUG]   = "No cpu available due to hotplug",
        [PERR_CPUSEMPTY] = "cpuset.cpus and cpuset.cpus.exclusive are empty",
        [PERR_HKEEPING]  = "partition config conflicts with housekeeping setup",
        [PERR_ACCESS]    = "Enable partition not permitted",
        [PERR_REMOTE]    = "Have remote partition underneath",
};

/*
 * CPUSET Locking Convention
 * -------------------------
 *
 * Below are the four global/local locks guarding cpuset structures in lock
 * acquisition order:
 *  - cpuset_top_mutex
 *  - cpu_hotplug_lock (cpus_read_lock/cpus_write_lock)
 *  - cpuset_mutex
 *  - callback_lock (raw spinlock)
 *
 * As cpuset will now indirectly flush a number of different workqueues in
 * housekeeping_update() to update housekeeping cpumasks when the set of
 * isolated CPUs is going to be changed, it may be vulnerable to deadlock
 * if we hold cpus_read_lock while calling into housekeeping_update().
 *
 * The first cpuset_top_mutex will be held except when calling into
 * cpuset_handle_hotplug() from the CPU hotplug code where cpus_write_lock
 * and cpuset_mutex will be held instead. The main purpose of this mutex
 * is to prevent regular cpuset control file write actions from interfering
 * with the call to housekeeping_update(), though CPU hotplug operation can
 * still happen in parallel. This mutex also provides protection for some
 * internal variables.
 *
 * A task must hold all the remaining three locks to modify externally visible
 * or used fields of cpusets, though some of the internally used cpuset fields
 * and internal variables can be modified without holding callback_lock. If only
 * reliable read access of the externally used fields are needed, a task can
 * hold either cpuset_mutex or callback_lock which are exposed to other
 * external subsystems.
 *
 * If a task holds cpu_hotplug_lock and cpuset_mutex, it blocks others,
 * ensuring that it is the only task able to also acquire callback_lock and
 * be able to modify cpusets.  It can perform various checks on the cpuset
 * structure first, knowing nothing will change. It can also allocate memory
 * without holding callback_lock. While it is performing these checks, various
 * callback routines can briefly acquire callback_lock to query cpusets.  Once
 * it is ready to make the changes, it takes callback_lock, blocking everyone
 * else.
 *
 * Calls to the kernel memory allocator cannot be made while holding
 * callback_lock which is a spinlock, as the memory allocator may sleep or
 * call back into cpuset code and acquire callback_lock.
 *
 * Now, the task_struct fields mems_allowed and mempolicy may be changed
 * by other task, we use alloc_lock in the task_struct fields to protect
 * them.
 *
 * The cpuset_common_seq_show() handlers only hold callback_lock across
 * small pieces of code, such as when reading out possibly multi-word
 * cpumasks and nodemasks.
 */

static DEFINE_MUTEX(cpuset_top_mutex);
static DEFINE_MUTEX(cpuset_mutex);

/*
 * File level internal variables below follow one of the following exclusion
 * rules.
 *
 * RWCS: Read/write-able by holding either cpus_write_lock (and optionally
 *       cpuset_mutex) or both cpus_read_lock and cpuset_mutex.
 *
 * CSCB: Readable by holding either cpuset_mutex or callback_lock. Writable
 *       by holding both cpuset_mutex and callback_lock.
 *
 * T:    Read/write-able by holding the cpuset_top_mutex.
 */

/*
 * For local partitions, update to subpartitions_cpus & isolated_cpus is done
 * in update_parent_effective_cpumask(). For remote partitions, it is done in
 * the remote_partition_*() and remote_cpus_update() helpers.
 */
/*
 * Exclusive CPUs distributed out to local or remote sub-partitions of
 * top_cpuset
 */
static cpumask_var_t    subpartitions_cpus;     /* RWCS */

/*
 * Exclusive CPUs in isolated partitions (shown in cpuset.cpus.isolated)
 */
static cpumask_var_t    isolated_cpus;          /* CSCB */

/*
 * Set if housekeeping cpumasks are to be updated.
 */
static bool             update_housekeeping;    /* RWCS */

/*
 * Copy of isolated_cpus to be passed to housekeeping_update()
 */
static cpumask_var_t    isolated_hk_cpus;       /* T */

/*
 * A flag to force sched domain rebuild at the end of an operation.
 * It can be set in
 *  - update_partition_sd_lb()
 *  - update_cpumasks_hier()
 *  - cpuset_update_flag()
 *  - cpuset_hotplug_update_tasks()
 *  - cpuset_handle_hotplug()
 *
 * Protected by cpuset_mutex (with cpus_read_lock held) or cpus_write_lock.
 *
 * Note that update_relax_domain_level() in cpuset-v1.c can still call
 * rebuild_sched_domains_locked() directly without using this flag.
 */
static bool force_sd_rebuild;                   /* RWCS */

/*
 * Partition root states:
 *
 *   0 - member (not a partition root)
 *   1 - partition root
 *   2 - partition root without load balancing (isolated)
 *  -1 - invalid partition root
 *  -2 - invalid isolated partition root
 *
 *  There are 2 types of partitions - local or remote. Local partitions are
 *  those whose parents are partition root themselves. Setting of
 *  cpuset.cpus.exclusive are optional in setting up local partitions.
 *  Remote partitions are those whose parents are not partition roots. Passing
 *  down exclusive CPUs by setting cpuset.cpus.exclusive along its ancestor
 *  nodes are mandatory in creating a remote partition.
 *
 *  For simplicity, a local partition can be created under a local or remote
 *  partition but a remote partition cannot have any partition root in its
 *  ancestor chain except the cgroup root.
 *
 *  A valid partition can be formed by setting exclusive_cpus or cpus_allowed
 *  if exclusive_cpus is not set. In the case of partition with empty
 *  exclusive_cpus, all the conflicting exclusive CPUs specified in the
 *  following cpumasks of sibling cpusets will be removed from its
 *  cpus_allowed in determining its effective_xcpus.
 *  - effective_xcpus
 *  - exclusive_cpus
 *
 *  The "cpuset.cpus.exclusive" control file should be used for setting up
 *  partition if the users want to get as many CPUs as possible.
 */
#define PRS_MEMBER              0
#define PRS_ROOT                1
#define PRS_ISOLATED            2
#define PRS_INVALID_ROOT        -1
#define PRS_INVALID_ISOLATED    -2

/*
 * Temporary cpumasks for working with partitions that are passed among
 * functions to avoid memory allocation in inner functions.
 */
struct tmpmasks {
        cpumask_var_t addmask, delmask; /* For partition root */
        cpumask_var_t new_cpus;         /* For update_cpumasks_hier() */
};

void inc_dl_tasks_cs(struct task_struct *p)
{
        struct cpuset *cs = task_cs(p);

        cs->nr_deadline_tasks++;
}

void dec_dl_tasks_cs(struct task_struct *p)
{
        struct cpuset *cs = task_cs(p);

        cs->nr_deadline_tasks--;
}

static inline bool is_partition_valid(const struct cpuset *cs)
{
        return cs->partition_root_state > 0;
}

static inline bool is_partition_invalid(const struct cpuset *cs)
{
        return cs->partition_root_state < 0;
}

static inline bool cs_is_member(const struct cpuset *cs)
{
        return cs->partition_root_state == PRS_MEMBER;
}

/*
 * Callers should hold callback_lock to modify partition_root_state.
 */
static inline void make_partition_invalid(struct cpuset *cs)
{
        if (cs->partition_root_state > 0)
                cs->partition_root_state = -cs->partition_root_state;
}

/*
 * Send notification event of whenever partition_root_state changes.
 */
static inline void notify_partition_change(struct cpuset *cs, int old_prs)
{
        if (old_prs == cs->partition_root_state)
                return;
        cgroup_file_notify(&cs->partition_file);

        /* Reset prs_err if not invalid */
        if (is_partition_valid(cs))
                WRITE_ONCE(cs->prs_err, PERR_NONE);
}

/*
 * The top_cpuset is always synchronized to cpu_active_mask and we should avoid
 * using cpu_online_mask as much as possible. An active CPU is always an online
 * CPU, but not vice versa. cpu_active_mask and cpu_online_mask can differ
 * during hotplug operations. A CPU is marked active at the last stage of CPU
 * bringup (CPUHP_AP_ACTIVE). It is also the stage where cpuset hotplug code
 * will be called to update the sched domains so that the scheduler can move
 * a normal task to a newly active CPU or remove tasks away from a newly
 * inactivated CPU. The online bit is set much earlier in the CPU bringup
 * process and cleared much later in CPU teardown.
 *
 * If cpu_online_mask is used while a hotunplug operation is happening in
 * parallel, we may leave an offline CPU in cpu_allowed or some other masks.
 */
struct cpuset top_cpuset = {
        .flags = BIT(CS_CPU_EXCLUSIVE) |
                 BIT(CS_MEM_EXCLUSIVE) | BIT(CS_SCHED_LOAD_BALANCE),
        .partition_root_state = PRS_ROOT,
};

/**
 * cpuset_lock - Acquire the global cpuset mutex
 *
 * This locks the global cpuset mutex to prevent modifications to cpuset
 * hierarchy and configurations. This helper is not enough to make modification.
 */
void cpuset_lock(void)
{
        mutex_lock(&cpuset_mutex);
}

void cpuset_unlock(void)
{
        mutex_unlock(&cpuset_mutex);
}

void lockdep_assert_cpuset_lock_held(void)
{
        lockdep_assert_held(&cpuset_mutex);
}

/**
 * cpuset_full_lock - Acquire full protection for cpuset modification
 *
 * Takes both CPU hotplug read lock (cpus_read_lock()) and cpuset mutex
 * to safely modify cpuset data.
 */
void cpuset_full_lock(void)
{
        mutex_lock(&cpuset_top_mutex);
        cpus_read_lock();
        mutex_lock(&cpuset_mutex);
}

void cpuset_full_unlock(void)
{
        mutex_unlock(&cpuset_mutex);
        cpus_read_unlock();
        mutex_unlock(&cpuset_top_mutex);
}

#ifdef CONFIG_LOCKDEP
bool lockdep_is_cpuset_held(void)
{
        return lockdep_is_held(&cpuset_mutex) ||
               lockdep_is_held(&cpuset_top_mutex);
}
#endif

static DEFINE_SPINLOCK(callback_lock);

void cpuset_callback_lock_irq(void)
{
        spin_lock_irq(&callback_lock);
}

void cpuset_callback_unlock_irq(void)
{
        spin_unlock_irq(&callback_lock);
}

static struct workqueue_struct *cpuset_migrate_mm_wq;

static DECLARE_WAIT_QUEUE_HEAD(cpuset_attach_wq);

static inline void check_insane_mems_config(nodemask_t *nodes)
{
        if (!cpusets_insane_config() &&
                movable_only_nodes(nodes)) {
                static_branch_enable_cpuslocked(&cpusets_insane_config_key);
                pr_info("Unsupported (movable nodes only) cpuset configuration detected (nmask=%*pbl)!\n"
                        "Cpuset allocations might fail even with a lot of memory available.\n",
                        nodemask_pr_args(nodes));
        }
}

/*
 * decrease cs->attach_in_progress.
 * wake_up cpuset_attach_wq if cs->attach_in_progress==0.
 */
static inline void dec_attach_in_progress_locked(struct cpuset *cs)
{
        lockdep_assert_cpuset_lock_held();

        cs->attach_in_progress--;
        if (!cs->attach_in_progress)
                wake_up(&cpuset_attach_wq);
}

static inline void dec_attach_in_progress(struct cpuset *cs)
{
        mutex_lock(&cpuset_mutex);
        dec_attach_in_progress_locked(cs);
        mutex_unlock(&cpuset_mutex);
}

static inline bool cpuset_v2(void)
{
        return !IS_ENABLED(CONFIG_CPUSETS_V1) ||
                cgroup_subsys_on_dfl(cpuset_cgrp_subsys);
}

/*
 * Cgroup v2 behavior is used on the "cpus" and "mems" control files when
 * on default hierarchy or when the cpuset_v2_mode flag is set by mounting
 * the v1 cpuset cgroup filesystem with the "cpuset_v2_mode" mount option.
 * With v2 behavior, "cpus" and "mems" are always what the users have
 * requested and won't be changed by hotplug events. Only the effective
 * cpus or mems will be affected.
 */
static inline bool is_in_v2_mode(void)
{
        return cpuset_v2() ||
              (cpuset_cgrp_subsys.root->flags & CGRP_ROOT_CPUSET_V2_MODE);
}

/**
 * partition_is_populated - check if partition has tasks
 * @cs: partition root to be checked
 * @excluded_child: a child cpuset to be excluded in task checking
 * Return: true if there are tasks, false otherwise
 *
 * @cs should be a valid partition root or going to become a partition root.
 * @excluded_child should be non-NULL when this cpuset is going to become a
 * partition itself.
 *
 * Note that a remote partition is not allowed underneath a valid local
 * or remote partition. So if a non-partition root child is populated,
 * the whole partition is considered populated.
 */
static inline bool partition_is_populated(struct cpuset *cs,
                                          struct cpuset *excluded_child)
{
        struct cpuset *cp;
        struct cgroup_subsys_state *pos_css;

        /*
         * We cannot call cs_is_populated(cs) directly, as
         * nr_populated_domain_children may include populated
         * csets from descendants that are partitions.
         */
        if (cs->css.cgroup->nr_populated_csets ||
            cs->attach_in_progress)
                return true;

        rcu_read_lock();
        cpuset_for_each_descendant_pre(cp, pos_css, cs) {
                if (cp == cs || cp == excluded_child)
                        continue;

                if (is_partition_valid(cp)) {
                        pos_css = css_rightmost_descendant(pos_css);
                        continue;
                }

                if (cpuset_is_populated(cp)) {
                        rcu_read_unlock();
                        return true;
                }
        }
        rcu_read_unlock();
        return false;
}

/*
 * Return in pmask the portion of a task's cpusets's cpus_allowed that
 * are online and are capable of running the task.  If none are found,
 * walk up the cpuset hierarchy until we find one that does have some
 * appropriate cpus.
 *
 * One way or another, we guarantee to return some non-empty subset
 * of cpu_active_mask.
 *
 * Call with callback_lock or cpuset_mutex held.
 */
static void guarantee_active_cpus(struct task_struct *tsk,
                                  struct cpumask *pmask)
{
        const struct cpumask *possible_mask = task_cpu_possible_mask(tsk);
        struct cpuset *cs;

        if (WARN_ON(!cpumask_and(pmask, possible_mask, cpu_active_mask)))
                cpumask_copy(pmask, cpu_active_mask);

        rcu_read_lock();
        cs = task_cs(tsk);

        while (!cpumask_intersects(cs->effective_cpus, pmask))
                cs = parent_cs(cs);

        cpumask_and(pmask, pmask, cs->effective_cpus);
        rcu_read_unlock();
}

/*
 * Return in *pmask the portion of a cpusets's mems_allowed that
 * are online, with memory.  If none are online with memory, walk
 * up the cpuset hierarchy until we find one that does have some
 * online mems.  The top cpuset always has some mems online.
 *
 * One way or another, we guarantee to return some non-empty subset
 * of node_states[N_MEMORY].
 *
 * Call with callback_lock or cpuset_mutex held.
 */
static void guarantee_online_mems(struct cpuset *cs, nodemask_t *pmask)
{
        while (!nodes_and(*pmask, cs->effective_mems, node_states[N_MEMORY]))
                cs = parent_cs(cs);
}

/**
 * alloc_cpumasks - Allocate an array of cpumask variables
 * @pmasks: Pointer to array of cpumask_var_t pointers
 * @size: Number of cpumasks to allocate
 * Return: 0 if successful, -ENOMEM otherwise.
 *
 * Allocates @size cpumasks and initializes them to empty. Returns 0 on
 * success, -ENOMEM on allocation failure. On failure, any previously
 * allocated cpumasks are freed.
 */
static inline int alloc_cpumasks(cpumask_var_t *pmasks[], u32 size)
{
        int i;

        for (i = 0; i < size; i++) {
                if (!zalloc_cpumask_var(pmasks[i], GFP_KERNEL)) {
                        while (--i >= 0)
                                free_cpumask_var(*pmasks[i]);
                        return -ENOMEM;
                }
        }
        return 0;
}

/**
 * alloc_tmpmasks - Allocate temporary cpumasks for cpuset operations.
 * @tmp: Pointer to tmpmasks structure to populate
 * Return: 0 on success, -ENOMEM on allocation failure
 */
static inline int alloc_tmpmasks(struct tmpmasks *tmp)
{
        /*
         * Array of pointers to the three cpumask_var_t fields in tmpmasks.
         * Note: Array size must match actual number of masks (3)
         */
        cpumask_var_t *pmask[3] = {
                &tmp->new_cpus,
                &tmp->addmask,
                &tmp->delmask
        };

        return alloc_cpumasks(pmask, ARRAY_SIZE(pmask));
}

/**
 * free_tmpmasks - free cpumasks in a tmpmasks structure
 * @tmp: the tmpmasks structure pointer
 */
static inline void free_tmpmasks(struct tmpmasks *tmp)
{
        if (!tmp)
                return;

        free_cpumask_var(tmp->new_cpus);
        free_cpumask_var(tmp->addmask);
        free_cpumask_var(tmp->delmask);
}

/**
 * dup_or_alloc_cpuset - Duplicate or allocate a new cpuset
 * @cs: Source cpuset to duplicate (NULL for a fresh allocation)
 *
 * Creates a new cpuset by either:
 * 1. Duplicating an existing cpuset (if @cs is non-NULL), or
 * 2. Allocating a fresh cpuset with zero-initialized masks (if @cs is NULL)
 *
 * Return: Pointer to newly allocated cpuset on success, NULL on failure
 */
static struct cpuset *dup_or_alloc_cpuset(struct cpuset *cs)
{
        struct cpuset *trial;

        /* Allocate base structure */
        trial = cs ? kmemdup(cs, sizeof(*cs), GFP_KERNEL) :
                     kzalloc_obj(*cs);
        if (!trial)
                return NULL;

        /* Setup cpumask pointer array */
        cpumask_var_t *pmask[4] = {
                &trial->cpus_allowed,
                &trial->effective_cpus,
                &trial->effective_xcpus,
                &trial->exclusive_cpus
        };

        if (alloc_cpumasks(pmask, ARRAY_SIZE(pmask))) {
                kfree(trial);
                return NULL;
        }

        /* Copy masks if duplicating */
        if (cs) {
                cpumask_copy(trial->cpus_allowed, cs->cpus_allowed);
                cpumask_copy(trial->effective_cpus, cs->effective_cpus);
                cpumask_copy(trial->effective_xcpus, cs->effective_xcpus);
                cpumask_copy(trial->exclusive_cpus, cs->exclusive_cpus);
        }

        return trial;
}

/**
 * free_cpuset - free the cpuset
 * @cs: the cpuset to be freed
 */
static inline void free_cpuset(struct cpuset *cs)
{
        free_cpumask_var(cs->cpus_allowed);
        free_cpumask_var(cs->effective_cpus);
        free_cpumask_var(cs->effective_xcpus);
        free_cpumask_var(cs->exclusive_cpus);
        kfree(cs);
}

/* Return user specified exclusive CPUs */
static inline struct cpumask *user_xcpus(struct cpuset *cs)
{
        return cpumask_empty(cs->exclusive_cpus) ? cs->cpus_allowed
                                                 : cs->exclusive_cpus;
}

static inline bool xcpus_empty(struct cpuset *cs)
{
        return cpumask_empty(cs->cpus_allowed) &&
               cpumask_empty(cs->exclusive_cpus);
}

/*
 * cpusets_are_exclusive() - check if two cpusets are exclusive
 *
 * Return true if exclusive, false if not
 */
static inline bool cpusets_are_exclusive(struct cpuset *cs1, struct cpuset *cs2)
{
        struct cpumask *xcpus1 = user_xcpus(cs1);
        struct cpumask *xcpus2 = user_xcpus(cs2);

        if (cpumask_intersects(xcpus1, xcpus2))
                return false;
        return true;
}

/**
 * cpus_excl_conflict - Check if two cpusets have exclusive CPU conflicts
 * @trial:      the trial cpuset to be checked
 * @sibling:    a sibling cpuset to be checked against
 * @xcpus_changed: set if exclusive_cpus has been set
 *
 * Returns: true if CPU exclusivity conflict exists, false otherwise
 *
 * Conflict detection rules:
 *  o cgroup v1
 *    See cpuset1_cpus_excl_conflict()
 *  o cgroup v2
 *    - The exclusive_cpus values cannot overlap.
 *    - New exclusive_cpus cannot be a superset of a sibling's cpus_allowed.
 */
static inline bool cpus_excl_conflict(struct cpuset *trial, struct cpuset *sibling,
                                      bool xcpus_changed)
{
        if (!cpuset_v2())
                return cpuset1_cpus_excl_conflict(trial, sibling);

        /* The cpus_allowed of a sibling cpuset cannot be a subset of the new exclusive_cpus */
        if (xcpus_changed && !cpumask_empty(sibling->cpus_allowed) &&
            cpumask_subset(sibling->cpus_allowed, trial->exclusive_cpus))
                return true;

        /* Exclusive_cpus cannot intersect */
        return cpumask_intersects(trial->exclusive_cpus, sibling->exclusive_cpus);
}

static inline bool mems_excl_conflict(struct cpuset *cs1, struct cpuset *cs2)
{
        if ((is_mem_exclusive(cs1) || is_mem_exclusive(cs2)))
                return nodes_intersects(cs1->mems_allowed, cs2->mems_allowed);
        return false;
}

/*
 * validate_change() - Used to validate that any proposed cpuset change
 *                     follows the structural rules for cpusets.
 *
 * If we replaced the flag and mask values of the current cpuset
 * (cur) with those values in the trial cpuset (trial), would
 * our various subset and exclusive rules still be valid?  Presumes
 * cpuset_mutex held.
 *
 * 'cur' is the address of an actual, in-use cpuset.  Operations
 * such as list traversal that depend on the actual address of the
 * cpuset in the list must use cur below, not trial.
 *
 * 'trial' is the address of bulk structure copy of cur, with
 * perhaps one or more of the fields cpus_allowed, mems_allowed,
 * or flags changed to new, trial values.
 *
 * Return 0 if valid, -errno if not.
 */

static int validate_change(struct cpuset *cur, struct cpuset *trial)
{
        struct cgroup_subsys_state *css;
        struct cpuset *c, *par;
        bool xcpus_changed;
        int ret = 0;

        rcu_read_lock();

        if (!is_in_v2_mode())
                ret = cpuset1_validate_change(cur, trial);
        if (ret)
                goto out;

        /* Remaining checks don't apply to root cpuset */
        if (cur == &top_cpuset)
                goto out;

        par = parent_cs(cur);

        /*
         * We can't shrink if we won't have enough room for SCHED_DEADLINE
         * tasks. This check is not done when scheduling is disabled as the
         * users should know what they are doing.
         *
         * For v1, effective_cpus == cpus_allowed & user_xcpus() returns
         * cpus_allowed.
         *
         * For v2, is_cpu_exclusive() & is_sched_load_balance() are true only
         * for non-isolated partition root. At this point, the target
         * effective_cpus isn't computed yet. user_xcpus() is the best
         * approximation.
         *
         * TBD: May need to precompute the real effective_cpus here in case
         * incorrect scheduling of SCHED_DEADLINE tasks in a partition
         * becomes an issue.
         */
        ret = -EBUSY;
        if (is_cpu_exclusive(cur) && is_sched_load_balance(cur) &&
            !cpuset_cpumask_can_shrink(cur->effective_cpus, user_xcpus(trial)))
                goto out;

        /*
         * If either I or some sibling (!= me) is exclusive, we can't
         * overlap. exclusive_cpus cannot overlap with each other if set.
         */
        ret = -EINVAL;
        xcpus_changed = !cpumask_equal(cur->exclusive_cpus, trial->exclusive_cpus);
        cpuset_for_each_child(c, css, par) {
                if (c == cur)
                        continue;
                if (cpus_excl_conflict(trial, c, xcpus_changed))
                        goto out;
                if (mems_excl_conflict(trial, c))
                        goto out;
        }

        ret = 0;
out:
        rcu_read_unlock();
        return ret;
}

#ifdef CONFIG_SMP

/*
 * generate_sched_domains()
 *
 * This function builds a partial partition of the systems CPUs
 * A 'partial partition' is a set of non-overlapping subsets whose
 * union is a subset of that set.
 * The output of this function needs to be passed to kernel/sched/core.c
 * partition_sched_domains() routine, which will rebuild the scheduler's
 * load balancing domains (sched domains) as specified by that partial
 * partition.
 *
 * See "What is sched_load_balance" in Documentation/admin-guide/cgroup-v1/cpusets.rst
 * for a background explanation of this.
 *
 * Does not return errors, on the theory that the callers of this
 * routine would rather not worry about failures to rebuild sched
 * domains when operating in the severe memory shortage situations
 * that could cause allocation failures below.
 *
 * Must be called with cpuset_mutex held.
 *
 * The three key local variables below are:
 *    cp - cpuset pointer, used (together with pos_css) to perform a
 *         top-down scan of all cpusets. For our purposes, rebuilding
 *         the schedulers sched domains, we can ignore !is_sched_load_
 *         balance cpusets.
 *  csa  - (for CpuSet Array) Array of pointers to all the cpusets
 *         that need to be load balanced, for convenient iterative
 *         access by the subsequent code that finds the best partition,
 *         i.e the set of domains (subsets) of CPUs such that the
 *         cpus_allowed of every cpuset marked is_sched_load_balance
 *         is a subset of one of these domains, while there are as
 *         many such domains as possible, each as small as possible.
 * doms  - Conversion of 'csa' to an array of cpumasks, for passing to
 *         the kernel/sched/core.c routine partition_sched_domains() in a
 *         convenient format, that can be easily compared to the prior
 *         value to determine what partition elements (sched domains)
 *         were changed (added or removed.)
 */
static int generate_sched_domains(cpumask_var_t **domains,
                        struct sched_domain_attr **attributes)
{
        struct cpuset *cp;      /* top-down scan of cpusets */
        struct cpuset **csa;    /* array of all cpuset ptrs */
        int i, j;               /* indices for partition finding loops */
        cpumask_var_t *doms;    /* resulting partition; i.e. sched domains */
        struct sched_domain_attr *dattr;  /* attributes for custom domains */
        int ndoms = 0;          /* number of sched domains in result */
        struct cgroup_subsys_state *pos_css;

        if (!cpuset_v2())
                return cpuset1_generate_sched_domains(domains, attributes);

        doms = NULL;
        dattr = NULL;
        csa = NULL;

        /* Special case for the 99% of systems with one, full, sched domain */
        if (cpumask_empty(subpartitions_cpus)) {
                ndoms = 1;
                /* !csa will be checked and can be correctly handled */
                goto generate_doms;
        }

        csa = kmalloc_objs(cp, nr_cpusets());
        if (!csa)
                goto done;

        /* Find how many partitions and cache them to csa[] */
        rcu_read_lock();
        cpuset_for_each_descendant_pre(cp, pos_css, &top_cpuset) {
                /*
                 * Only valid partition roots that are not isolated and with
                 * non-empty effective_cpus will be saved into csa[].
                 */
                if ((cp->partition_root_state == PRS_ROOT) &&
                    !cpumask_empty(cp->effective_cpus))
                        csa[ndoms++] = cp;

                /*
                 * Skip @cp's subtree if not a partition root and has no
                 * exclusive CPUs to be granted to child cpusets.
                 */
                if (!is_partition_valid(cp) && cpumask_empty(cp->exclusive_cpus))
                        pos_css = css_rightmost_descendant(pos_css);
        }
        rcu_read_unlock();

        for (i = 0; i < ndoms; i++) {
                for (j = i + 1; j < ndoms; j++) {
                        if (cpusets_overlap(csa[i], csa[j]))
                                /*
                                 * Cgroup v2 shouldn't pass down overlapping
                                 * partition root cpusets.
                                 */
                                WARN_ON_ONCE(1);
                }
        }

generate_doms:
        doms = alloc_sched_domains(ndoms);
        if (!doms)
                goto done;

        /*
         * The rest of the code, including the scheduler, can deal with
         * dattr==NULL case. No need to abort if alloc fails.
         */
        dattr = kmalloc_objs(struct sched_domain_attr, ndoms);

        /*
         * Cgroup v2 doesn't support domain attributes, just set all of them
         * to SD_ATTR_INIT. Also non-isolating partition root CPUs are a
         * subset of HK_TYPE_DOMAIN_BOOT housekeeping CPUs.
         */
        for (i = 0; i < ndoms; i++) {
                /*
                 * The top cpuset may contain some boot time isolated
                 * CPUs that need to be excluded from the sched domain.
                 */
                if (!csa || csa[i] == &top_cpuset)
                        cpumask_and(doms[i], top_cpuset.effective_cpus,
                                    housekeeping_cpumask(HK_TYPE_DOMAIN_BOOT));
                else
                        cpumask_copy(doms[i], csa[i]->effective_cpus);
                if (dattr)
                        dattr[i] = SD_ATTR_INIT;
        }

done:
        kfree(csa);

        /*
         * Fallback to the default domain if kmalloc() failed.
         * See comments in partition_sched_domains().
         */
        if (doms == NULL)
                ndoms = 1;

        *domains    = doms;
        *attributes = dattr;
        return ndoms;
}

static void dl_update_tasks_root_domain(struct cpuset *cs)
{
        struct css_task_iter it;
        struct task_struct *task;

        if (cs->nr_deadline_tasks == 0)
                return;

        css_task_iter_start(&cs->css, 0, &it);

        while ((task = css_task_iter_next(&it)))
                dl_add_task_root_domain(task);

        css_task_iter_end(&it);
}

void dl_rebuild_rd_accounting(void)
{
        struct cpuset *cs = NULL;
        struct cgroup_subsys_state *pos_css;
        int cpu;
        u64 cookie = ++dl_cookie;

        lockdep_assert_cpuset_lock_held();
        lockdep_assert_cpus_held();
        lockdep_assert_held(&sched_domains_mutex);

        rcu_read_lock();

        for_each_possible_cpu(cpu) {
                if (dl_bw_visited(cpu, cookie))
                        continue;

                dl_clear_root_domain_cpu(cpu);
        }

        cpuset_for_each_descendant_pre(cs, pos_css, &top_cpuset) {

                if (cpumask_empty(cs->effective_cpus)) {
                        pos_css = css_rightmost_descendant(pos_css);
                        continue;
                }

                css_get(&cs->css);

                rcu_read_unlock();

                dl_update_tasks_root_domain(cs);

                rcu_read_lock();
                css_put(&cs->css);
        }
        rcu_read_unlock();
}

/*
 * Rebuild scheduler domains.
 *
 * If the flag 'sched_load_balance' of any cpuset with non-empty
 * 'cpus' changes, or if the 'cpus' allowed changes in any cpuset
 * which has that flag enabled, or if any cpuset with a non-empty
 * 'cpus' is removed, then call this routine to rebuild the
 * scheduler's dynamic sched domains.
 *
 * Call with cpuset_mutex held.  Takes cpus_read_lock().
 */
void rebuild_sched_domains_locked(void)
{
        struct sched_domain_attr *attr;
        cpumask_var_t *doms;
        int ndoms;
        int i;

        lockdep_assert_cpus_held();
        lockdep_assert_cpuset_lock_held();
        force_sd_rebuild = false;

        /* Generate domain masks and attrs */
        ndoms = generate_sched_domains(&doms, &attr);

        /*
        * cpuset_hotplug_workfn is invoked synchronously now, thus this
        * function should not race with CPU hotplug. And the effective CPUs
        * must not include any offline CPUs. Passing an offline CPU in the
        * doms to partition_sched_domains() will trigger a kernel panic.
        *
        * We perform a final check here: if the doms contains any
        * offline CPUs, a warning is emitted and we return directly to
        * prevent the panic.
        */
        for (i = 0; doms && i < ndoms; i++) {
                if (WARN_ON_ONCE(!cpumask_subset(doms[i], cpu_active_mask)))
                        return;
        }

        /* Have scheduler rebuild the domains */
        partition_sched_domains(ndoms, doms, attr);
}
#else /* !CONFIG_SMP */
void rebuild_sched_domains_locked(void)
{
}
#endif /* CONFIG_SMP */

static void rebuild_sched_domains_cpuslocked(void)
{
        mutex_lock(&cpuset_mutex);
        rebuild_sched_domains_locked();
        mutex_unlock(&cpuset_mutex);
}

void rebuild_sched_domains(void)
{
        cpus_read_lock();
        rebuild_sched_domains_cpuslocked();
        cpus_read_unlock();
}

void cpuset_reset_sched_domains(void)
{
        mutex_lock(&cpuset_mutex);
        partition_sched_domains(1, NULL, NULL);
        mutex_unlock(&cpuset_mutex);
}

/**
 * cpuset_update_tasks_cpumask - Update the cpumasks of tasks in the cpuset.
 * @cs: the cpuset in which each task's cpus_allowed mask needs to be changed
 * @new_cpus: the temp variable for the new effective_cpus mask
 *
 * Iterate through each task of @cs updating its cpus_allowed to the
 * effective cpuset's.  As this function is called with cpuset_mutex held,
 * cpuset membership stays stable.
 *
 * For top_cpuset, task_cpu_possible_mask() is used instead of effective_cpus
 * to make sure all offline CPUs are also included as hotplug code won't
 * update cpumasks for tasks in top_cpuset.
 *
 * As task_cpu_possible_mask() can be task dependent in arm64, we have to
 * do cpu masking per task instead of doing it once for all.
 */
void cpuset_update_tasks_cpumask(struct cpuset *cs, struct cpumask *new_cpus)
{
        struct css_task_iter it;
        struct task_struct *task;
        bool top_cs = cs == &top_cpuset;

        css_task_iter_start(&cs->css, 0, &it);
        while ((task = css_task_iter_next(&it))) {
                const struct cpumask *possible_mask = task_cpu_possible_mask(task);

                if (top_cs) {
                        /*
                         * PF_KTHREAD tasks are handled by housekeeping.
                         * PF_NO_SETAFFINITY tasks are ignored.
                         */
                        if (task->flags & (PF_KTHREAD | PF_NO_SETAFFINITY))
                                continue;
                        cpumask_andnot(new_cpus, possible_mask, subpartitions_cpus);
                } else {
                        cpumask_and(new_cpus, possible_mask, cs->effective_cpus);
                }
                set_cpus_allowed_ptr(task, new_cpus);
        }
        css_task_iter_end(&it);
}

/**
 * compute_effective_cpumask - Compute the effective cpumask of the cpuset
 * @new_cpus: the temp variable for the new effective_cpus mask
 * @cs: the cpuset the need to recompute the new effective_cpus mask
 * @parent: the parent cpuset
 *
 * The result is valid only if the given cpuset isn't a partition root.
 */
static void compute_effective_cpumask(struct cpumask *new_cpus,
                                      struct cpuset *cs, struct cpuset *parent)
{
        cpumask_and(new_cpus, cs->cpus_allowed, parent->effective_cpus);
}

/*
 * Commands for update_parent_effective_cpumask
 */
enum partition_cmd {
        partcmd_enable,         /* Enable partition root          */
        partcmd_enablei,        /* Enable isolated partition root */
        partcmd_disable,        /* Disable partition root         */
        partcmd_update,         /* Update parent's effective_cpus */
        partcmd_invalidate,     /* Make partition invalid         */
};

static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,
                                    struct tmpmasks *tmp);

/*
 * Update partition exclusive flag
 *
 * Return: 0 if successful, an error code otherwise
 */
static int update_partition_exclusive_flag(struct cpuset *cs, int new_prs)
{
        bool exclusive = (new_prs > PRS_MEMBER);

        if (exclusive && !is_cpu_exclusive(cs)) {
                if (cpuset_update_flag(CS_CPU_EXCLUSIVE, cs, 1))
                        return PERR_NOTEXCL;
        } else if (!exclusive && is_cpu_exclusive(cs)) {
                /* Turning off CS_CPU_EXCLUSIVE will not return error */
                cpuset_update_flag(CS_CPU_EXCLUSIVE, cs, 0);
        }
        return 0;
}

/*
 * Update partition load balance flag and/or rebuild sched domain
 *
 * Changing load balance flag will automatically call
 * rebuild_sched_domains_locked().
 * This function is for cgroup v2 only.
 */
static void update_partition_sd_lb(struct cpuset *cs, int old_prs)
{
        int new_prs = cs->partition_root_state;
        bool rebuild_domains = (new_prs > 0) || (old_prs > 0);
        bool new_lb;

        /*
         * If cs is not a valid partition root, the load balance state
         * will follow its parent.
         */
        if (new_prs > 0) {
                new_lb = (new_prs != PRS_ISOLATED);
        } else {
                new_lb = is_sched_load_balance(parent_cs(cs));
        }
        if (new_lb != !!is_sched_load_balance(cs)) {
                rebuild_domains = true;
                if (new_lb)
                        set_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
                else
                        clear_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
        }

        if (rebuild_domains)
                cpuset_force_rebuild();
}

/*
 * tasks_nocpu_error - Return true if tasks will have no effective_cpus
 */
static bool tasks_nocpu_error(struct cpuset *parent, struct cpuset *cs,
                              struct cpumask *xcpus)
{
        /*
         * A populated partition (cs or parent) can't have empty effective_cpus
         */
        return (cpumask_subset(parent->effective_cpus, xcpus) &&
                partition_is_populated(parent, cs)) ||
               (!cpumask_intersects(xcpus, cpu_active_mask) &&
                partition_is_populated(cs, NULL));
}

static void reset_partition_data(struct cpuset *cs)
{
        struct cpuset *parent = parent_cs(cs);

        if (!cpuset_v2())
                return;

        lockdep_assert_held(&callback_lock);

        if (cpumask_empty(cs->exclusive_cpus)) {
                cpumask_clear(cs->effective_xcpus);
                if (is_cpu_exclusive(cs))
                        clear_bit(CS_CPU_EXCLUSIVE, &cs->flags);
        }
        if (!cpumask_and(cs->effective_cpus, parent->effective_cpus, cs->cpus_allowed))
                cpumask_copy(cs->effective_cpus, parent->effective_cpus);
}

/*
 * isolated_cpus_update - Update the isolated_cpus mask
 * @old_prs: old partition_root_state
 * @new_prs: new partition_root_state
 * @xcpus: exclusive CPUs with state change
 */
static void isolated_cpus_update(int old_prs, int new_prs, struct cpumask *xcpus)
{
        WARN_ON_ONCE(old_prs == new_prs);
        lockdep_assert_held(&callback_lock);
        lockdep_assert_held(&cpuset_mutex);
        if (new_prs == PRS_ISOLATED) {
                if (cpumask_subset(xcpus, isolated_cpus))
                        return;
                cpumask_or(isolated_cpus, isolated_cpus, xcpus);
        } else {
                if (!cpumask_intersects(xcpus, isolated_cpus))
                        return;
                cpumask_andnot(isolated_cpus, isolated_cpus, xcpus);
        }
        update_housekeeping = true;
}

/*
 * partition_xcpus_add - Add new exclusive CPUs to partition
 * @new_prs: new partition_root_state
 * @parent: parent cpuset
 * @xcpus: exclusive CPUs to be added
 *
 * Remote partition if parent == NULL
 */
static void partition_xcpus_add(int new_prs, struct cpuset *parent,
                                struct cpumask *xcpus)
{
        WARN_ON_ONCE(new_prs < 0);
        lockdep_assert_held(&callback_lock);
        if (!parent)
                parent = &top_cpuset;


        if (parent == &top_cpuset)
                cpumask_or(subpartitions_cpus, subpartitions_cpus, xcpus);

        if (new_prs != parent->partition_root_state)
                isolated_cpus_update(parent->partition_root_state, new_prs,
                                     xcpus);

        cpumask_andnot(parent->effective_cpus, parent->effective_cpus, xcpus);
}

/*
 * partition_xcpus_del - Remove exclusive CPUs from partition
 * @old_prs: old partition_root_state
 * @parent: parent cpuset
 * @xcpus: exclusive CPUs to be removed
 *
 * Remote partition if parent == NULL
 */
static void partition_xcpus_del(int old_prs, struct cpuset *parent,
                                struct cpumask *xcpus)
{
        WARN_ON_ONCE(old_prs < 0);
        lockdep_assert_held(&callback_lock);
        if (!parent)
                parent = &top_cpuset;

        if (parent == &top_cpuset)
                cpumask_andnot(subpartitions_cpus, subpartitions_cpus, xcpus);

        if (old_prs != parent->partition_root_state)
                isolated_cpus_update(old_prs, parent->partition_root_state,
                                     xcpus);

        cpumask_or(parent->effective_cpus, parent->effective_cpus, xcpus);
        cpumask_and(parent->effective_cpus, parent->effective_cpus, cpu_active_mask);
}

/*
 * isolated_cpus_can_update - check for isolated & nohz_full conflicts
 * @add_cpus: cpu mask for cpus that are going to be isolated
 * @del_cpus: cpu mask for cpus that are no longer isolated, can be NULL
 * Return: false if there is conflict, true otherwise
 *
 * If nohz_full is enabled and we have isolated CPUs, their combination must
 * still leave housekeeping CPUs.
 *
 * TBD: Should consider merging this function into
 *      prstate_housekeeping_conflict().
 */
static bool isolated_cpus_can_update(struct cpumask *add_cpus,
                                     struct cpumask *del_cpus)
{
        cpumask_var_t full_hk_cpus;
        int res = true;

        if (!housekeeping_enabled(HK_TYPE_KERNEL_NOISE))
                return true;

        if (del_cpus && cpumask_weight_and(del_cpus,
                        housekeeping_cpumask(HK_TYPE_KERNEL_NOISE)))
                return true;

        if (!alloc_cpumask_var(&full_hk_cpus, GFP_KERNEL))
                return false;

        cpumask_and(full_hk_cpus, housekeeping_cpumask(HK_TYPE_KERNEL_NOISE),
                    housekeeping_cpumask(HK_TYPE_DOMAIN));
        cpumask_andnot(full_hk_cpus, full_hk_cpus, isolated_cpus);
        cpumask_and(full_hk_cpus, full_hk_cpus, cpu_active_mask);
        if (!cpumask_weight_andnot(full_hk_cpus, add_cpus))
                res = false;

        free_cpumask_var(full_hk_cpus);
        return res;
}

/*
 * prstate_housekeeping_conflict - check for partition & housekeeping conflicts
 * @prstate: partition root state to be checked
 * @new_cpus: cpu mask
 * Return: true if there is conflict, false otherwise
 *
 * CPUs outside of HK_TYPE_DOMAIN_BOOT, if defined, can only be used in an
 * isolated partition.
 */
static bool prstate_housekeeping_conflict(int prstate, struct cpumask *new_cpus)
{
        if (!housekeeping_enabled(HK_TYPE_DOMAIN_BOOT))
                return false;

        if ((prstate != PRS_ISOLATED) &&
            !cpumask_subset(new_cpus, housekeeping_cpumask(HK_TYPE_DOMAIN_BOOT)))
                return true;

        return false;
}

/*
 * cpuset_update_sd_hk_unlock - Rebuild sched domains, update HK & unlock
 *
 * Update housekeeping cpumasks and rebuild sched domains if necessary and
 * then do a cpuset_full_unlock().
 * This should be called at the end of cpuset operation.
 */
static void cpuset_update_sd_hk_unlock(void)
        __releases(&cpuset_mutex)
        __releases(&cpuset_top_mutex)
{
        /* force_sd_rebuild will be cleared in rebuild_sched_domains_locked() */
        if (force_sd_rebuild)
                rebuild_sched_domains_locked();

        if (update_housekeeping) {
                update_housekeeping = false;
                cpumask_copy(isolated_hk_cpus, isolated_cpus);

                /*
                 * housekeeping_update() is now called without holding
                 * cpus_read_lock and cpuset_mutex. Only cpuset_top_mutex
                 * is still being held for mutual exclusion.
                 */
                mutex_unlock(&cpuset_mutex);
                cpus_read_unlock();
                WARN_ON_ONCE(housekeeping_update(isolated_hk_cpus));
                mutex_unlock(&cpuset_top_mutex);
        } else {
                cpuset_full_unlock();
        }
}

/*
 * Work function to invoke cpuset_update_sd_hk_unlock()
 */
static void hk_sd_workfn(struct work_struct *work)
{
        cpuset_full_lock();
        cpuset_update_sd_hk_unlock();
}

/**
 * rm_siblings_excl_cpus - Remove exclusive CPUs that are used by sibling cpusets
 * @parent: Parent cpuset containing all siblings
 * @cs: Current cpuset (will be skipped)
 * @excpus:  exclusive effective CPU mask to modify
 *
 * This function ensures the given @excpus mask doesn't include any CPUs that
 * are exclusively allocated to sibling cpusets. It walks through all siblings
 * of @cs under @parent and removes their exclusive CPUs from @excpus.
 */
static int rm_siblings_excl_cpus(struct cpuset *parent, struct cpuset *cs,
                                        struct cpumask *excpus)
{
        struct cgroup_subsys_state *css;
        struct cpuset *sibling;
        int retval = 0;

        if (cpumask_empty(excpus))
                return 0;

        /*
         * Remove exclusive CPUs from siblings
         */
        rcu_read_lock();
        cpuset_for_each_child(sibling, css, parent) {
                struct cpumask *sibling_xcpus;

                if (sibling == cs)
                        continue;

                /*
                 * If exclusive_cpus is defined, effective_xcpus will always
                 * be a subset. Otherwise, effective_xcpus will only be set
                 * in a valid partition root.
                 */
                sibling_xcpus = cpumask_empty(sibling->exclusive_cpus)
                              ? sibling->effective_xcpus
                              : sibling->exclusive_cpus;

                if (cpumask_intersects(excpus, sibling_xcpus)) {
                        cpumask_andnot(excpus, excpus, sibling_xcpus);
                        retval++;
                }
        }
        rcu_read_unlock();

        return retval;
}

/*
 * compute_excpus - compute effective exclusive CPUs
 * @cs: cpuset
 * @xcpus: effective exclusive CPUs value to be set
 * Return: 0 if there is no sibling conflict, > 0 otherwise
 *
 * If exclusive_cpus isn't explicitly set , we have to scan the sibling cpusets
 * and exclude their exclusive_cpus or effective_xcpus as well.
 */
static int compute_excpus(struct cpuset *cs, struct cpumask *excpus)
{
        struct cpuset *parent = parent_cs(cs);

        cpumask_and(excpus, user_xcpus(cs), parent->effective_xcpus);

        if (!cpumask_empty(cs->exclusive_cpus))
                return 0;

        return rm_siblings_excl_cpus(parent, cs, excpus);
}

/*
 * compute_trialcs_excpus - Compute effective exclusive CPUs for a trial cpuset
 * @trialcs: The trial cpuset containing the proposed new configuration
 * @cs: The original cpuset that the trial configuration is based on
 * Return: 0 if successful with no sibling conflict, >0 if a conflict is found
 *
 * Computes the effective_xcpus for a trial configuration. @cs is provided to represent
 * the real cs.
 */
static int compute_trialcs_excpus(struct cpuset *trialcs, struct cpuset *cs)
{
        struct cpuset *parent = parent_cs(trialcs);
        struct cpumask *excpus = trialcs->effective_xcpus;

        /* trialcs is member, cpuset.cpus has no impact to excpus */
        if (cs_is_member(cs))
                cpumask_and(excpus, trialcs->exclusive_cpus,
                                parent->effective_xcpus);
        else
                cpumask_and(excpus, user_xcpus(trialcs), parent->effective_xcpus);

        return rm_siblings_excl_cpus(parent, cs, excpus);
}

static inline bool is_remote_partition(struct cpuset *cs)
{
        return cs->remote_partition;
}

static inline bool is_local_partition(struct cpuset *cs)
{
        return is_partition_valid(cs) && !is_remote_partition(cs);
}

/*
 * remote_partition_enable - Enable current cpuset as a remote partition root
 * @cs: the cpuset to update
 * @new_prs: new partition_root_state
 * @tmp: temporary masks
 * Return: 0 if successful, errcode if error
 *
 * Enable the current cpuset to become a remote partition root taking CPUs
 * directly from the top cpuset. cpuset_mutex must be held by the caller.
 */
static int remote_partition_enable(struct cpuset *cs, int new_prs,
                                   struct tmpmasks *tmp)
{
        /*
         * The user must have sysadmin privilege.
         */
        if (!capable(CAP_SYS_ADMIN))
                return PERR_ACCESS;

        /*
         * The requested exclusive_cpus must not be allocated to other
         * partitions and it can't use up all the root's effective_cpus.
         *
         * The effective_xcpus mask can contain offline CPUs, but there must
         * be at least one or more online CPUs present before it can be enabled.
         *
         * Note that creating a remote partition with any local partition root
         * above it or remote partition root underneath it is not allowed.
         */
        compute_excpus(cs, tmp->new_cpus);
        WARN_ON_ONCE(cpumask_intersects(tmp->new_cpus, subpartitions_cpus));
        if (!cpumask_intersects(tmp->new_cpus, cpu_active_mask) ||
            cpumask_subset(top_cpuset.effective_cpus, tmp->new_cpus))
                return PERR_INVCPUS;
        if (((new_prs == PRS_ISOLATED) &&
             !isolated_cpus_can_update(tmp->new_cpus, NULL)) ||
            prstate_housekeeping_conflict(new_prs, tmp->new_cpus))
                return PERR_HKEEPING;

        spin_lock_irq(&callback_lock);
        partition_xcpus_add(new_prs, NULL, tmp->new_cpus);
        cs->remote_partition = true;
        cpumask_copy(cs->effective_xcpus, tmp->new_cpus);
        spin_unlock_irq(&callback_lock);
        cpuset_force_rebuild();
        cs->prs_err = 0;

        /*
         * Propagate changes in top_cpuset's effective_cpus down the hierarchy.
         */
        cpuset_update_tasks_cpumask(&top_cpuset, tmp->new_cpus);
        update_sibling_cpumasks(&top_cpuset, NULL, tmp);
        return 0;
}

/*
 * remote_partition_disable - Remove current cpuset from remote partition list
 * @cs: the cpuset to update
 * @tmp: temporary masks
 *
 * The effective_cpus is also updated.
 *
 * cpuset_mutex must be held by the caller.
 */
static void remote_partition_disable(struct cpuset *cs, struct tmpmasks *tmp)
{
        WARN_ON_ONCE(!is_remote_partition(cs));
        /*
         * When a CPU is offlined, top_cpuset may end up with no available CPUs,
         * which should clear subpartitions_cpus. We should not emit a warning for this
         * scenario: the hierarchy is updated from top to bottom, so subpartitions_cpus
         * may already be cleared when disabling the partition.
         */
        WARN_ON_ONCE(!cpumask_subset(cs->effective_xcpus, subpartitions_cpus) &&
                     !cpumask_empty(subpartitions_cpus));

        spin_lock_irq(&callback_lock);
        cs->remote_partition = false;
        partition_xcpus_del(cs->partition_root_state, NULL, cs->effective_xcpus);
        if (cs->prs_err)
                cs->partition_root_state = -cs->partition_root_state;
        else
                cs->partition_root_state = PRS_MEMBER;

        /* effective_xcpus may need to be changed */
        compute_excpus(cs, cs->effective_xcpus);
        reset_partition_data(cs);
        spin_unlock_irq(&callback_lock);
        cpuset_force_rebuild();

        /*
         * Propagate changes in top_cpuset's effective_cpus down the hierarchy.
         */
        cpuset_update_tasks_cpumask(&top_cpuset, tmp->new_cpus);
        update_sibling_cpumasks(&top_cpuset, NULL, tmp);
}

/*
 * remote_cpus_update - cpus_exclusive change of remote partition
 * @cs: the cpuset to be updated
 * @xcpus: the new exclusive_cpus mask, if non-NULL
 * @excpus: the new effective_xcpus mask
 * @tmp: temporary masks
 *
 * top_cpuset and subpartitions_cpus will be updated or partition can be
 * invalidated.
 */
static void remote_cpus_update(struct cpuset *cs, struct cpumask *xcpus,
                               struct cpumask *excpus, struct tmpmasks *tmp)
{
        bool adding, deleting;
        int prs = cs->partition_root_state;

        if (WARN_ON_ONCE(!is_remote_partition(cs)))
                return;

        WARN_ON_ONCE(!cpumask_subset(cs->effective_xcpus, subpartitions_cpus));

        if (cpumask_empty(excpus)) {
                cs->prs_err = PERR_CPUSEMPTY;
                goto invalidate;
        }

        adding   = cpumask_andnot(tmp->addmask, excpus, cs->effective_xcpus);
        deleting = cpumask_andnot(tmp->delmask, cs->effective_xcpus, excpus);

        /*
         * Additions of remote CPUs is only allowed if those CPUs are
         * not allocated to other partitions and there are effective_cpus
         * left in the top cpuset.
         */
        if (adding) {
                WARN_ON_ONCE(cpumask_intersects(tmp->addmask, subpartitions_cpus));
                if (!capable(CAP_SYS_ADMIN))
                        cs->prs_err = PERR_ACCESS;
                else if (cpumask_intersects(tmp->addmask, subpartitions_cpus) ||
                         cpumask_subset(top_cpuset.effective_cpus, tmp->addmask))
                        cs->prs_err = PERR_NOCPUS;
                else if ((prs == PRS_ISOLATED) &&
                         !isolated_cpus_can_update(tmp->addmask, tmp->delmask))
                        cs->prs_err = PERR_HKEEPING;
                if (cs->prs_err)
                        goto invalidate;
        }

        spin_lock_irq(&callback_lock);
        if (adding)
                partition_xcpus_add(prs, NULL, tmp->addmask);
        if (deleting)
                partition_xcpus_del(prs, NULL, tmp->delmask);
        /*
         * Need to update effective_xcpus and exclusive_cpus now as
         * update_sibling_cpumasks() below may iterate back to the same cs.
         */
        cpumask_copy(cs->effective_xcpus, excpus);
        if (xcpus)
                cpumask_copy(cs->exclusive_cpus, xcpus);
        spin_unlock_irq(&callback_lock);
        if (adding || deleting)
                cpuset_force_rebuild();

        /*
         * Propagate changes in top_cpuset's effective_cpus down the hierarchy.
         */
        cpuset_update_tasks_cpumask(&top_cpuset, tmp->new_cpus);
        update_sibling_cpumasks(&top_cpuset, NULL, tmp);
        return;

invalidate:
        remote_partition_disable(cs, tmp);
}

/**
 * update_parent_effective_cpumask - update effective_cpus mask of parent cpuset
 * @cs:      The cpuset that requests change in partition root state
 * @cmd:     Partition root state change command
 * @newmask: Optional new cpumask for partcmd_update
 * @tmp:     Temporary addmask and delmask
 * Return:   0 or a partition root state error code
 *
 * For partcmd_enable*, the cpuset is being transformed from a non-partition
 * root to a partition root. The effective_xcpus (cpus_allowed if
 * effective_xcpus not set) mask of the given cpuset will be taken away from
 * parent's effective_cpus. The function will return 0 if all the CPUs listed
 * in effective_xcpus can be granted or an error code will be returned.
 *
 * For partcmd_disable, the cpuset is being transformed from a partition
 * root back to a non-partition root. Any CPUs in effective_xcpus will be
 * given back to parent's effective_cpus. 0 will always be returned.
 *
 * For partcmd_update, if the optional newmask is specified, the cpu list is
 * to be changed from effective_xcpus to newmask. Otherwise, effective_xcpus is
 * assumed to remain the same. The cpuset should either be a valid or invalid
 * partition root. The partition root state may change from valid to invalid
 * or vice versa. An error code will be returned if transitioning from
 * invalid to valid violates the exclusivity rule.
 *
 * For partcmd_invalidate, the current partition will be made invalid.
 *
 * The partcmd_enable* and partcmd_disable commands are used by
 * update_prstate(). An error code may be returned and the caller will check
 * for error.
 *
 * The partcmd_update command is used by update_cpumasks_hier() with newmask
 * NULL and update_cpumask() with newmask set. The partcmd_invalidate is used
 * by update_cpumask() with NULL newmask. In both cases, the callers won't
 * check for error and so partition_root_state and prs_err will be updated
 * directly.
 */
static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
                                           struct cpumask *newmask,
                                           struct tmpmasks *tmp)
{
        struct cpuset *parent = parent_cs(cs);
        int adding;     /* Adding cpus to parent's effective_cpus       */
        int deleting;   /* Deleting cpus from parent's effective_cpus   */
        int old_prs, new_prs;
        int part_error = PERR_NONE;     /* Partition error? */
        struct cpumask *xcpus = user_xcpus(cs);
        int parent_prs = parent->partition_root_state;
        bool nocpu;

        lockdep_assert_cpuset_lock_held();
        WARN_ON_ONCE(is_remote_partition(cs));  /* For local partition only */

        /*
         * new_prs will only be changed for the partcmd_update and
         * partcmd_invalidate commands.
         */
        adding = deleting = false;
        old_prs = new_prs = cs->partition_root_state;

        if (cmd == partcmd_invalidate) {
                if (is_partition_invalid(cs))
                        return 0;

                /*
                 * Make the current partition invalid.
                 */
                if (is_partition_valid(parent))
                        adding = cpumask_and(tmp->addmask,
                                             xcpus, parent->effective_xcpus);
                if (old_prs > 0)
                        new_prs = -old_prs;

                goto write_error;
        }

        /*
         * The parent must be a partition root.
         * The new cpumask, if present, or the current cpus_allowed must
         * not be empty.
         */
        if (!is_partition_valid(parent)) {
                return is_partition_invalid(parent)
                       ? PERR_INVPARENT : PERR_NOTPART;
        }
        if (!newmask && xcpus_empty(cs))
                return PERR_CPUSEMPTY;

        nocpu = tasks_nocpu_error(parent, cs, xcpus);

        if ((cmd == partcmd_enable) || (cmd == partcmd_enablei)) {
                /*
                 * Need to call compute_excpus() in case
                 * exclusive_cpus not set. Sibling conflict should only happen
                 * if exclusive_cpus isn't set.
                 */
                xcpus = tmp->delmask;
                if (compute_excpus(cs, xcpus))
                        WARN_ON_ONCE(!cpumask_empty(cs->exclusive_cpus));
                new_prs = (cmd == partcmd_enable) ? PRS_ROOT : PRS_ISOLATED;

                /*
                 * Enabling partition root is not allowed if its
                 * effective_xcpus is empty.
                 */
                if (cpumask_empty(xcpus))
                        return PERR_INVCPUS;

                if (prstate_housekeeping_conflict(new_prs, xcpus))
                        return PERR_HKEEPING;

                if ((new_prs == PRS_ISOLATED) && (new_prs != parent_prs) &&
                    !isolated_cpus_can_update(xcpus, NULL))
                        return PERR_HKEEPING;

                if (tasks_nocpu_error(parent, cs, xcpus))
                        return PERR_NOCPUS;

                /*
                 * This function will only be called when all the preliminary
                 * checks have passed. At this point, the following condition
                 * should hold.
                 *
                 * (cs->effective_xcpus & cpu_active_mask) ⊆ parent->effective_cpus
                 *
                 * Warn if it is not the case.
                 */
                cpumask_and(tmp->new_cpus, xcpus, cpu_active_mask);
                WARN_ON_ONCE(!cpumask_subset(tmp->new_cpus, parent->effective_cpus));

                deleting = true;
        } else if (cmd == partcmd_disable) {
                /*
                 * May need to add cpus back to parent's effective_cpus
                 * (and maybe removed from subpartitions_cpus/isolated_cpus)
                 * for valid partition root. xcpus may contain CPUs that
                 * shouldn't be removed from the two global cpumasks.
                 */
                if (is_partition_valid(cs)) {
                        cpumask_copy(tmp->addmask, cs->effective_xcpus);
                        adding = true;
                }
                new_prs = PRS_MEMBER;
        } else if (newmask) {
                /*
                 * Empty cpumask is not allowed
                 */
                if (cpumask_empty(newmask)) {
                        part_error = PERR_CPUSEMPTY;
                        goto write_error;
                }

                /* Check newmask again, whether cpus are available for parent/cs */
                nocpu |= tasks_nocpu_error(parent, cs, newmask);

                /*
                 * partcmd_update with newmask:
                 *
                 * Compute add/delete mask to/from effective_cpus
                 *
                 * For valid partition:
                 *   addmask = exclusive_cpus & ~newmask
                 *                            & parent->effective_xcpus
                 *   delmask = newmask & ~exclusive_cpus
                 *                     & parent->effective_xcpus
                 *
                 * For invalid partition:
                 *   delmask = newmask & parent->effective_xcpus
                 *   The partition may become valid soon.
                 */
                if (is_partition_invalid(cs)) {
                        adding = false;
                        deleting = cpumask_and(tmp->delmask,
                                        newmask, parent->effective_xcpus);
                } else {
                        cpumask_andnot(tmp->addmask, xcpus, newmask);
                        adding = cpumask_and(tmp->addmask, tmp->addmask,
                                             parent->effective_xcpus);

                        cpumask_andnot(tmp->delmask, newmask, xcpus);
                        deleting = cpumask_and(tmp->delmask, tmp->delmask,
                                               parent->effective_xcpus);
                }

                /*
                 * TBD: Invalidate a currently valid child root partition may
                 * still break isolated_cpus_can_update() rule if parent is an
                 * isolated partition.
                 */
                if (is_partition_valid(cs) && (old_prs != parent_prs)) {
                        if ((parent_prs == PRS_ROOT) &&
                            /* Adding to parent means removing isolated CPUs */
                            !isolated_cpus_can_update(tmp->delmask, tmp->addmask))
                                part_error = PERR_HKEEPING;
                        if ((parent_prs == PRS_ISOLATED) &&
                            /* Adding to parent means adding isolated CPUs */
                            !isolated_cpus_can_update(tmp->addmask, tmp->delmask))
                                part_error = PERR_HKEEPING;
                }

                /*
                 * The new CPUs to be removed from parent's effective CPUs
                 * must be present.
                 */
                if (deleting) {
                        cpumask_and(tmp->new_cpus, tmp->delmask, cpu_active_mask);
                        WARN_ON_ONCE(!cpumask_subset(tmp->new_cpus, parent->effective_cpus));
                }

                /*
                 * Make partition invalid if parent's effective_cpus could
                 * become empty and there are tasks in the parent.
                 */
                if (nocpu && (!adding ||
                    !cpumask_intersects(tmp->addmask, cpu_active_mask))) {
                        part_error = PERR_NOCPUS;
                        deleting = false;
                        adding = cpumask_and(tmp->addmask,
                                             xcpus, parent->effective_xcpus);
                }
        } else {
                /*
                 * partcmd_update w/o newmask
                 *
                 * delmask = effective_xcpus & parent->effective_cpus
                 *
                 * This can be called from:
                 * 1) update_cpumasks_hier()
                 * 2) cpuset_hotplug_update_tasks()
                 *
                 * Check to see if it can be transitioned from valid to
                 * invalid partition or vice versa.
                 *
                 * A partition error happens when parent has tasks and all
                 * its effective CPUs will have to be distributed out.
                 */
                if (nocpu) {
                        part_error = PERR_NOCPUS;
                        if (is_partition_valid(cs))
                                adding = cpumask_and(tmp->addmask,
                                                xcpus, parent->effective_xcpus);
                } else if (is_partition_invalid(cs) && !cpumask_empty(xcpus) &&
                           cpumask_subset(xcpus, parent->effective_xcpus)) {
                        struct cgroup_subsys_state *css;
                        struct cpuset *child;
                        bool exclusive = true;

                        /*
                         * Convert invalid partition to valid has to
                         * pass the cpu exclusivity test.
                         */
                        rcu_read_lock();
                        cpuset_for_each_child(child, css, parent) {
                                if (child == cs)
                                        continue;
                                if (!cpusets_are_exclusive(cs, child)) {
                                        exclusive = false;
                                        break;
                                }
                        }
                        rcu_read_unlock();
                        if (exclusive)
                                deleting = cpumask_and(tmp->delmask,
                                                xcpus, parent->effective_cpus);
                        else
                                part_error = PERR_NOTEXCL;
                }
        }

write_error:
        if (part_error)
                WRITE_ONCE(cs->prs_err, part_error);

        if (cmd == partcmd_update) {
                /*
                 * Check for possible transition between valid and invalid
                 * partition root.
                 */
                switch (cs->partition_root_state) {
                case PRS_ROOT:
                case PRS_ISOLATED:
                        if (part_error)
                                new_prs = -old_prs;
                        break;
                case PRS_INVALID_ROOT:
                case PRS_INVALID_ISOLATED:
                        if (!part_error)
                                new_prs = -old_prs;
                        break;
                }
        }

        if (!adding && !deleting && (new_prs == old_prs))
                return 0;

        /*
         * Transitioning between invalid to valid or vice versa may require
         * changing CS_CPU_EXCLUSIVE. In the case of partcmd_update,
         * validate_change() has already been successfully called and
         * CPU lists in cs haven't been updated yet. So defer it to later.
         */
        if ((old_prs != new_prs) && (cmd != partcmd_update))  {
                int err = update_partition_exclusive_flag(cs, new_prs);

                if (err)
                        return err;
        }

        /*
         * Change the parent's effective_cpus & effective_xcpus (top cpuset
         * only).
         *
         * Newly added CPUs will be removed from effective_cpus and
         * newly deleted ones will be added back to effective_cpus.
         */
        spin_lock_irq(&callback_lock);
        if (old_prs != new_prs)
                cs->partition_root_state = new_prs;

        /*
         * Adding to parent's effective_cpus means deletion CPUs from cs
         * and vice versa.
         */
        if (adding)
                partition_xcpus_del(old_prs, parent, tmp->addmask);
        if (deleting)
                partition_xcpus_add(new_prs, parent, tmp->delmask);

        spin_unlock_irq(&callback_lock);

        if ((old_prs != new_prs) && (cmd == partcmd_update))
                update_partition_exclusive_flag(cs, new_prs);

        if (adding || deleting) {
                cpuset_update_tasks_cpumask(parent, tmp->addmask);
                update_sibling_cpumasks(parent, cs, tmp);
        }

        /*
         * For partcmd_update without newmask, it is being called from
         * cpuset_handle_hotplug(). Update the load balance flag and
         * scheduling domain accordingly.
         */
        if ((cmd == partcmd_update) && !newmask)
                update_partition_sd_lb(cs, old_prs);

        notify_partition_change(cs, old_prs);
        return 0;
}

/**
 * compute_partition_effective_cpumask - compute effective_cpus for partition
 * @cs: partition root cpuset
 * @new_ecpus: previously computed effective_cpus to be updated
 *
 * Compute the effective_cpus of a partition root by scanning effective_xcpus
 * of child partition roots and excluding their effective_xcpus.
 *
 * This has the side effect of invalidating valid child partition roots,
 * if necessary. Since it is called from either cpuset_hotplug_update_tasks()
 * or update_cpumasks_hier() where parent and children are modified
 * successively, we don't need to call update_parent_effective_cpumask()
 * and the child's effective_cpus will be updated in later iterations.
 *
 * Note that rcu_read_lock() is assumed to be held.
 */
static void compute_partition_effective_cpumask(struct cpuset *cs,
                                                struct cpumask *new_ecpus)
{
        struct cgroup_subsys_state *css;
        struct cpuset *child;
        bool populated = partition_is_populated(cs, NULL);

        /*
         * Check child partition roots to see if they should be
         * invalidated when
         *  1) child effective_xcpus not a subset of new
         *     excluisve_cpus
         *  2) All the effective_cpus will be used up and cp
         *     has tasks
         */
        compute_excpus(cs, new_ecpus);
        cpumask_and(new_ecpus, new_ecpus, cpu_active_mask);

        rcu_read_lock();
        cpuset_for_each_child(child, css, cs) {
                if (!is_partition_valid(child))
                        continue;

                /*
                 * There shouldn't be a remote partition underneath another
                 * partition root.
                 */
                WARN_ON_ONCE(is_remote_partition(child));
                child->prs_err = 0;
                if (!cpumask_subset(child->effective_xcpus,
                                    cs->effective_xcpus))
                        child->prs_err = PERR_INVCPUS;
                else if (populated &&
                         cpumask_subset(new_ecpus, child->effective_xcpus))
                        child->prs_err = PERR_NOCPUS;

                if (child->prs_err) {
                        int old_prs = child->partition_root_state;

                        /*
                         * Invalidate child partition
                         */
                        spin_lock_irq(&callback_lock);
                        make_partition_invalid(child);
                        spin_unlock_irq(&callback_lock);
                        notify_partition_change(child, old_prs);
                        continue;
                }
                cpumask_andnot(new_ecpus, new_ecpus,
                               child->effective_xcpus);
        }
        rcu_read_unlock();
}

/*
 * update_cpumasks_hier - Update effective cpumasks and tasks in the subtree
 * @cs:  the cpuset to consider
 * @tmp: temp variables for calculating effective_cpus & partition setup
 * @force: don't skip any descendant cpusets if set
 *
 * When configured cpumask is changed, the effective cpumasks of this cpuset
 * and all its descendants need to be updated.
 *
 * On legacy hierarchy, effective_cpus will be the same with cpu_allowed.
 *
 * Called with cpuset_mutex held
 */
static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp,
                                 bool force)
{
        struct cpuset *cp;
        struct cgroup_subsys_state *pos_css;
        int old_prs, new_prs;

        rcu_read_lock();
        cpuset_for_each_descendant_pre(cp, pos_css, cs) {
                struct cpuset *parent = parent_cs(cp);
                bool remote = is_remote_partition(cp);
                bool update_parent = false;

                old_prs = new_prs = cp->partition_root_state;

                /*
                 * For child remote partition root (!= cs), we need to call
                 * remote_cpus_update() if effective_xcpus will be changed.
                 * Otherwise, we can skip the whole subtree.
                 *
                 * remote_cpus_update() will reuse tmp->new_cpus only after
                 * its value is being processed.
                 */
                if (remote && (cp != cs)) {
                        compute_excpus(cp, tmp->new_cpus);
                        if (cpumask_equal(cp->effective_xcpus, tmp->new_cpus)) {
                                pos_css = css_rightmost_descendant(pos_css);
                                continue;
                        }
                        rcu_read_unlock();
                        remote_cpus_update(cp, NULL, tmp->new_cpus, tmp);
                        rcu_read_lock();

                        /* Remote partition may be invalidated */
                        new_prs = cp->partition_root_state;
                        remote = (new_prs == old_prs);
                }

                if (remote || (is_partition_valid(parent) && is_partition_valid(cp)))
                        compute_partition_effective_cpumask(cp, tmp->new_cpus);
                else
                        compute_effective_cpumask(tmp->new_cpus, cp, parent);

                if (remote)
                        goto get_css;   /* Ready to update cpuset data */

                /*
                 * A partition with no effective_cpus is allowed as long as
                 * there is no task associated with it. Call
                 * update_parent_effective_cpumask() to check it.
                 */
                if (is_partition_valid(cp) && cpumask_empty(tmp->new_cpus)) {
                        update_parent = true;
                        goto update_parent_effective;
                }

                /*
                 * If it becomes empty, inherit the effective mask of the
                 * parent, which is guaranteed to have some CPUs unless
                 * it is a partition root that has explicitly distributed
                 * out all its CPUs.
                 */
                if (is_in_v2_mode() && !remote && cpumask_empty(tmp->new_cpus))
                        cpumask_copy(tmp->new_cpus, parent->effective_cpus);

                /*
                 * Skip the whole subtree if
                 * 1) the cpumask remains the same,
                 * 2) has no partition root state,
                 * 3) force flag not set, and
                 * 4) for v2 load balance state same as its parent.
                 */
                if (!cp->partition_root_state && !force &&
                    cpumask_equal(tmp->new_cpus, cp->effective_cpus) &&
                    (!cpuset_v2() ||
                    (is_sched_load_balance(parent) == is_sched_load_balance(cp)))) {
                        pos_css = css_rightmost_descendant(pos_css);
                        continue;
                }

update_parent_effective:
                /*
                 * update_parent_effective_cpumask() should have been called
                 * for cs already in update_cpumask(). We should also call
                 * cpuset_update_tasks_cpumask() again for tasks in the parent
                 * cpuset if the parent's effective_cpus changes.
                 */
                if ((cp != cs) && old_prs) {
                        switch (parent->partition_root_state) {
                        case PRS_ROOT:
                        case PRS_ISOLATED:
                                update_parent = true;
                                break;

                        default:
                                /*
                                 * When parent is not a partition root or is
                                 * invalid, child partition roots become
                                 * invalid too.
                                 */
                                if (is_partition_valid(cp))
                                        new_prs = -cp->partition_root_state;
                                WRITE_ONCE(cp->prs_err,
                                           is_partition_invalid(parent)
                                           ? PERR_INVPARENT : PERR_NOTPART);
                                break;
                        }
                }
get_css:
                if (!css_tryget_online(&cp->css))
                        continue;
                rcu_read_unlock();

                if (update_parent) {
                        update_parent_effective_cpumask(cp, partcmd_update, NULL, tmp);
                        /*
                         * The cpuset partition_root_state may become
                         * invalid. Capture it.
                         */
                        new_prs = cp->partition_root_state;
                }

                spin_lock_irq(&callback_lock);
                cpumask_copy(cp->effective_cpus, tmp->new_cpus);
                cp->partition_root_state = new_prs;
                /*
                 * Need to compute effective_xcpus if either exclusive_cpus
                 * is non-empty or it is a valid partition root.
                 */
                if ((new_prs > 0) || !cpumask_empty(cp->exclusive_cpus))
                        compute_excpus(cp, cp->effective_xcpus);
                if (new_prs <= 0)
                        reset_partition_data(cp);
                spin_unlock_irq(&callback_lock);

                notify_partition_change(cp, old_prs);

                WARN_ON(!is_in_v2_mode() &&
                        !cpumask_equal(cp->cpus_allowed, cp->effective_cpus));

                cpuset_update_tasks_cpumask(cp, tmp->new_cpus);

                /*
                 * On default hierarchy, inherit the CS_SCHED_LOAD_BALANCE
                 * from parent if current cpuset isn't a valid partition root
                 * and their load balance states differ.
                 */
                if (cpuset_v2() && !is_partition_valid(cp) &&
                    (is_sched_load_balance(parent) != is_sched_load_balance(cp))) {
                        if (is_sched_load_balance(parent))
                                set_bit(CS_SCHED_LOAD_BALANCE, &cp->flags);
                        else
                                clear_bit(CS_SCHED_LOAD_BALANCE, &cp->flags);
                }

                /*
                 * On legacy hierarchy, if the effective cpumask of any non-
                 * empty cpuset is changed, we need to rebuild sched domains.
                 * On default hierarchy, the cpuset needs to be a partition
                 * root as well.
                 */
                if (!cpumask_empty(cp->cpus_allowed) &&
                    is_sched_load_balance(cp) &&
                   (!cpuset_v2() || is_partition_valid(cp)))
                        cpuset_force_rebuild();

                rcu_read_lock();
                css_put(&cp->css);
        }
        rcu_read_unlock();
}

/**
 * update_sibling_cpumasks - Update siblings cpumasks
 * @parent:  Parent cpuset
 * @cs:      Current cpuset
 * @tmp:     Temp variables
 */
static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,
                                    struct tmpmasks *tmp)
{
        struct cpuset *sibling;
        struct cgroup_subsys_state *pos_css;

        lockdep_assert_cpuset_lock_held();

        /*
         * Check all its siblings and call update_cpumasks_hier()
         * if their effective_cpus will need to be changed.
         *
         * It is possible a change in parent's effective_cpus
         * due to a change in a child partition's effective_xcpus will impact
         * its siblings even if they do not inherit parent's effective_cpus
         * directly. It should not impact valid partition.
         *
         * The update_cpumasks_hier() function may sleep. So we have to
         * release the RCU read lock before calling it.
         */
        rcu_read_lock();
        cpuset_for_each_child(sibling, pos_css, parent) {
                if (sibling == cs || is_partition_valid(sibling))
                        continue;

                compute_effective_cpumask(tmp->new_cpus, sibling,
                                          parent);
                if (cpumask_equal(tmp->new_cpus, sibling->effective_cpus))
                        continue;

                if (!css_tryget_online(&sibling->css))
                        continue;

                rcu_read_unlock();
                update_cpumasks_hier(sibling, tmp, false);
                rcu_read_lock();
                css_put(&sibling->css);
        }
        rcu_read_unlock();
}

static int parse_cpuset_cpulist(const char *buf, struct cpumask *out_mask)
{
        int retval;

        retval = cpulist_parse(buf, out_mask);
        if (retval < 0)
                return retval;
        if (!cpumask_subset(out_mask, top_cpuset.cpus_allowed))
                return -EINVAL;

        return 0;
}

/**
 * validate_partition - Validate a cpuset partition configuration
 * @cs: The cpuset to validate
 * @trialcs: The trial cpuset containing proposed configuration changes
 *
 * If any validation check fails, the appropriate error code is set in the
 * cpuset's prs_err field.
 *
 * Return: PRS error code (0 if valid, non-zero error code if invalid)
 */
static enum prs_errcode validate_partition(struct cpuset *cs, struct cpuset *trialcs)
{
        struct cpuset *parent = parent_cs(cs);

        if (cs_is_member(trialcs))
                return PERR_NONE;

        if (cpumask_empty(trialcs->effective_xcpus))
                return PERR_INVCPUS;

        if (prstate_housekeeping_conflict(trialcs->partition_root_state,
                                          trialcs->effective_xcpus))
                return PERR_HKEEPING;

        if (tasks_nocpu_error(parent, cs, trialcs->effective_xcpus))
                return PERR_NOCPUS;

        return PERR_NONE;
}

/**
 * partition_cpus_change - Handle partition state changes due to CPU mask updates
 * @cs: The target cpuset being modified
 * @trialcs: The trial cpuset containing proposed configuration changes
 * @tmp: Temporary masks for intermediate calculations
 *
 * This function handles partition state transitions triggered by CPU mask changes.
 * CPU modifications may cause a partition to be disabled or require state updates.
 */
static void partition_cpus_change(struct cpuset *cs, struct cpuset *trialcs,
                                        struct tmpmasks *tmp)
{
        enum prs_errcode prs_err;

        if (cs_is_member(cs))
                return;

        prs_err = validate_partition(cs, trialcs);
        if (prs_err)
                trialcs->prs_err = cs->prs_err = prs_err;

        if (is_remote_partition(cs)) {
                if (trialcs->prs_err)
                        remote_partition_disable(cs, tmp);
                else
                        remote_cpus_update(cs, trialcs->exclusive_cpus,
                                           trialcs->effective_xcpus, tmp);
        } else {
                if (trialcs->prs_err)
                        update_parent_effective_cpumask(cs, partcmd_invalidate,
                                                        NULL, tmp);
                else
                        update_parent_effective_cpumask(cs, partcmd_update,
                                                        trialcs->effective_xcpus, tmp);
        }
}

/**
 * update_cpumask - update the cpus_allowed mask of a cpuset and all tasks in it
 * @cs: the cpuset to consider
 * @trialcs: trial cpuset
 * @buf: buffer of cpu numbers written to this cpuset
 */
static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
                          const char *buf)
{
        int retval;
        struct tmpmasks tmp;
        bool force = false;
        int old_prs = cs->partition_root_state;

        retval = parse_cpuset_cpulist(buf, trialcs->cpus_allowed);
        if (retval < 0)
                return retval;

        /* Nothing to do if the cpus didn't change */
        if (cpumask_equal(cs->cpus_allowed, trialcs->cpus_allowed))
                return 0;

        compute_trialcs_excpus(trialcs, cs);
        trialcs->prs_err = PERR_NONE;

        retval = validate_change(cs, trialcs);
        if (retval < 0)
                return retval;

        if (alloc_tmpmasks(&tmp))
                return -ENOMEM;

        /*
         * Check all the descendants in update_cpumasks_hier() if
         * effective_xcpus is to be changed.
         */
        force = !cpumask_equal(cs->effective_xcpus, trialcs->effective_xcpus);

        partition_cpus_change(cs, trialcs, &tmp);

        spin_lock_irq(&callback_lock);
        cpumask_copy(cs->cpus_allowed, trialcs->cpus_allowed);
        cpumask_copy(cs->effective_xcpus, trialcs->effective_xcpus);
        if ((old_prs > 0) && !is_partition_valid(cs))
                reset_partition_data(cs);
        spin_unlock_irq(&callback_lock);

        /* effective_cpus/effective_xcpus will be updated here */
        update_cpumasks_hier(cs, &tmp, force);

        /* Update CS_SCHED_LOAD_BALANCE and/or sched_domains, if necessary */
        if (cs->partition_root_state)
                update_partition_sd_lb(cs, old_prs);

        free_tmpmasks(&tmp);
        return retval;
}

/**
 * update_exclusive_cpumask - update the exclusive_cpus mask of a cpuset
 * @cs: the cpuset to consider
 * @trialcs: trial cpuset
 * @buf: buffer of cpu numbers written to this cpuset
 *
 * The tasks' cpumask will be updated if cs is a valid partition root.
 */
static int update_exclusive_cpumask(struct cpuset *cs, struct cpuset *trialcs,
                                    const char *buf)
{
        int retval;
        struct tmpmasks tmp;
        bool force = false;
        int old_prs = cs->partition_root_state;

        retval = parse_cpuset_cpulist(buf, trialcs->exclusive_cpus);
        if (retval < 0)
                return retval;

        /* Nothing to do if the CPUs didn't change */
        if (cpumask_equal(cs->exclusive_cpus, trialcs->exclusive_cpus))
                return 0;

        /*
         * Reject the change if there is exclusive CPUs conflict with
         * the siblings.
         */
        if (compute_trialcs_excpus(trialcs, cs))
                return -EINVAL;

        /*
         * Check all the descendants in update_cpumasks_hier() if
         * effective_xcpus is to be changed.
         */
        force = !cpumask_equal(cs->effective_xcpus, trialcs->effective_xcpus);

        retval = validate_change(cs, trialcs);
        if (retval)
                return retval;

        if (alloc_tmpmasks(&tmp))
                return -ENOMEM;

        trialcs->prs_err = PERR_NONE;
        partition_cpus_change(cs, trialcs, &tmp);

        spin_lock_irq(&callback_lock);
        cpumask_copy(cs->exclusive_cpus, trialcs->exclusive_cpus);
        cpumask_copy(cs->effective_xcpus, trialcs->effective_xcpus);
        if ((old_prs > 0) && !is_partition_valid(cs))
                reset_partition_data(cs);
        spin_unlock_irq(&callback_lock);

        /*
         * Call update_cpumasks_hier() to update effective_cpus/effective_xcpus
         * of the subtree when it is a valid partition root or effective_xcpus
         * is updated.
         */
        if (is_partition_valid(cs) || force)
                update_cpumasks_hier(cs, &tmp, force);

        /* Update CS_SCHED_LOAD_BALANCE and/or sched_domains, if necessary */
        if (cs->partition_root_state)
                update_partition_sd_lb(cs, old_prs);

        free_tmpmasks(&tmp);
        return 0;
}

/*
 * Migrate memory region from one set of nodes to another.  This is
 * performed asynchronously as it can be called from process migration path
 * holding locks involved in process management.  All mm migrations are
 * performed in the queued order and can be waited for by flushing
 * cpuset_migrate_mm_wq.
 */

struct cpuset_migrate_mm_work {
        struct work_struct      work;
        struct mm_struct        *mm;
        nodemask_t              from;
        nodemask_t              to;
};

static void cpuset_migrate_mm_workfn(struct work_struct *work)
{
        struct cpuset_migrate_mm_work *mwork =
                container_of(work, struct cpuset_migrate_mm_work, work);

        /* on a wq worker, no need to worry about %current's mems_allowed */
        do_migrate_pages(mwork->mm, &mwork->from, &mwork->to, MPOL_MF_MOVE_ALL);
        mmput(mwork->mm);
        kfree(mwork);
}

static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
                                                        const nodemask_t *to)
{
        struct cpuset_migrate_mm_work *mwork;

        if (nodes_equal(*from, *to)) {
                mmput(mm);
                return;
        }

        mwork = kzalloc_obj(*mwork);
        if (mwork) {
                mwork->mm = mm;
                mwork->from = *from;
                mwork->to = *to;
                INIT_WORK(&mwork->work, cpuset_migrate_mm_workfn);
                queue_work(cpuset_migrate_mm_wq, &mwork->work);
        } else {
                mmput(mm);
        }
}

static void flush_migrate_mm_task_workfn(struct callback_head *head)
{
        flush_workqueue(cpuset_migrate_mm_wq);
        kfree(head);
}

static void schedule_flush_migrate_mm(void)
{
        struct callback_head *flush_cb;

        flush_cb = kzalloc_obj(struct callback_head);
        if (!flush_cb)
                return;

        init_task_work(flush_cb, flush_migrate_mm_task_workfn);

        if (task_work_add(current, flush_cb, TWA_RESUME))
                kfree(flush_cb);
}

/*
 * cpuset_change_task_nodemask - change task's mems_allowed and mempolicy
 * @tsk: the task to change
 * @newmems: new nodes that the task will be set
 *
 * We use the mems_allowed_seq seqlock to safely update both tsk->mems_allowed
 * and rebind an eventual tasks' mempolicy. If the task is allocating in
 * parallel, it might temporarily see an empty intersection, which results in
 * a seqlock check and retry before OOM or allocation failure.
 */
static void cpuset_change_task_nodemask(struct task_struct *tsk,
                                        nodemask_t *newmems)
{
        task_lock(tsk);

        local_irq_disable();
        write_seqcount_begin(&tsk->mems_allowed_seq);

        nodes_or(tsk->mems_allowed, tsk->mems_allowed, *newmems);
        mpol_rebind_task(tsk, newmems);
        tsk->mems_allowed = *newmems;

        write_seqcount_end(&tsk->mems_allowed_seq);
        local_irq_enable();

        task_unlock(tsk);
}

static void *cpuset_being_rebound;

/**
 * cpuset_update_tasks_nodemask - Update the nodemasks of tasks in the cpuset.
 * @cs: the cpuset in which each task's mems_allowed mask needs to be changed
 *
 * Iterate through each task of @cs updating its mems_allowed to the
 * effective cpuset's.  As this function is called with cpuset_mutex held,
 * cpuset membership stays stable.
 */
void cpuset_update_tasks_nodemask(struct cpuset *cs)
{
        static nodemask_t newmems;      /* protected by cpuset_mutex */
        struct css_task_iter it;
        struct task_struct *task;

        cpuset_being_rebound = cs;              /* causes mpol_dup() rebind */

        guarantee_online_mems(cs, &newmems);

        /*
         * The mpol_rebind_mm() call takes mmap_lock, which we couldn't
         * take while holding tasklist_lock.  Forks can happen - the
         * mpol_dup() cpuset_being_rebound check will catch such forks,
         * and rebind their vma mempolicies too.  Because we still hold
         * the global cpuset_mutex, we know that no other rebind effort
         * will be contending for the global variable cpuset_being_rebound.
         * It's ok if we rebind the same mm twice; mpol_rebind_mm()
         * is idempotent.  Also migrate pages in each mm to new nodes.
         */
        css_task_iter_start(&cs->css, 0, &it);
        while ((task = css_task_iter_next(&it))) {
                struct mm_struct *mm;
                bool migrate;

                cpuset_change_task_nodemask(task, &newmems);

                mm = get_task_mm(task);
                if (!mm)
                        continue;

                migrate = is_memory_migrate(cs);

                mpol_rebind_mm(mm, &cs->mems_allowed);
                if (migrate)
                        cpuset_migrate_mm(mm, &cs->old_mems_allowed, &newmems);
                else
                        mmput(mm);
        }
        css_task_iter_end(&it);

        /*
         * All the tasks' nodemasks have been updated, update
         * cs->old_mems_allowed.
         */
        cs->old_mems_allowed = newmems;

        /* We're done rebinding vmas to this cpuset's new mems_allowed. */
        cpuset_being_rebound = NULL;
}

/*
 * update_nodemasks_hier - Update effective nodemasks and tasks in the subtree
 * @cs: the cpuset to consider
 * @new_mems: a temp variable for calculating new effective_mems
 *
 * When configured nodemask is changed, the effective nodemasks of this cpuset
 * and all its descendants need to be updated.
 *
 * On legacy hierarchy, effective_mems will be the same with mems_allowed.
 *
 * Called with cpuset_mutex held
 */
static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems)
{
        struct cpuset *cp;
        struct cgroup_subsys_state *pos_css;

        rcu_read_lock();
        cpuset_for_each_descendant_pre(cp, pos_css, cs) {
                struct cpuset *parent = parent_cs(cp);

                bool has_mems = nodes_and(*new_mems, cp->mems_allowed, parent->effective_mems);

                /*
                 * If it becomes empty, inherit the effective mask of the
                 * parent, which is guaranteed to have some MEMs.
                 */
                if (is_in_v2_mode() && !has_mems)
                        *new_mems = parent->effective_mems;

                /* Skip the whole subtree if the nodemask remains the same. */
                if (nodes_equal(*new_mems, cp->effective_mems)) {
                        pos_css = css_rightmost_descendant(pos_css);
                        continue;
                }

                if (!css_tryget_online(&cp->css))
                        continue;
                rcu_read_unlock();

                spin_lock_irq(&callback_lock);
                cp->effective_mems = *new_mems;
                spin_unlock_irq(&callback_lock);

                WARN_ON(!is_in_v2_mode() &&
                        !nodes_equal(cp->mems_allowed, cp->effective_mems));

                cpuset_update_tasks_nodemask(cp);

                rcu_read_lock();
                css_put(&cp->css);
        }
        rcu_read_unlock();
}

/*
 * Handle user request to change the 'mems' memory placement
 * of a cpuset.  Needs to validate the request, update the
 * cpusets mems_allowed, and for each task in the cpuset,
 * update mems_allowed and rebind task's mempolicy and any vma
 * mempolicies and if the cpuset is marked 'memory_migrate',
 * migrate the tasks pages to the new memory.
 *
 * Call with cpuset_mutex held. May take callback_lock during call.
 * Will take tasklist_lock, scan tasklist for tasks in cpuset cs,
 * lock each such tasks mm->mmap_lock, scan its vma's and rebind
 * their mempolicies to the cpusets new mems_allowed.
 */
static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,
                           const char *buf)
{
        int retval;

        /*
         * An empty mems_allowed is ok iff there are no tasks in the cpuset.
         * The validate_change() call ensures that cpusets with tasks have memory.
         */
        retval = nodelist_parse(buf, trialcs->mems_allowed);
        if (retval < 0)
                return retval;

        if (!nodes_subset(trialcs->mems_allowed,
                          top_cpuset.mems_allowed))
                return -EINVAL;

        /* No change? nothing to do */
        if (nodes_equal(cs->mems_allowed, trialcs->mems_allowed))
                return 0;

        retval = validate_change(cs, trialcs);
        if (retval < 0)
                return retval;

        check_insane_mems_config(&trialcs->mems_allowed);

        spin_lock_irq(&callback_lock);
        cs->mems_allowed = trialcs->mems_allowed;
        spin_unlock_irq(&callback_lock);

        /* use trialcs->mems_allowed as a temp variable */
        update_nodemasks_hier(cs, &trialcs->mems_allowed);
        return 0;
}

bool current_cpuset_is_being_rebound(void)
{
        bool ret;

        rcu_read_lock();
        ret = task_cs(current) == cpuset_being_rebound;
        rcu_read_unlock();

        return ret;
}

/*
 * cpuset_update_flag - read a 0 or a 1 in a file and update associated flag
 * bit:         the bit to update (see cpuset_flagbits_t)
 * cs:          the cpuset to update
 * turning_on:  whether the flag is being set or cleared
 *
 * Call with cpuset_mutex held.
 */

int cpuset_update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
                       int turning_on)
{
        struct cpuset *trialcs;
        int balance_flag_changed;
        int spread_flag_changed;
        int err;

        trialcs = dup_or_alloc_cpuset(cs);
        if (!trialcs)
                return -ENOMEM;

        if (turning_on)
                set_bit(bit, &trialcs->flags);
        else
                clear_bit(bit, &trialcs->flags);

        err = validate_change(cs, trialcs);
        if (err < 0)
                goto out;

        balance_flag_changed = (is_sched_load_balance(cs) !=
                                is_sched_load_balance(trialcs));

        spread_flag_changed = ((is_spread_slab(cs) != is_spread_slab(trialcs))
                        || (is_spread_page(cs) != is_spread_page(trialcs)));

        spin_lock_irq(&callback_lock);
        cs->flags = trialcs->flags;
        spin_unlock_irq(&callback_lock);

        if (!cpumask_empty(trialcs->cpus_allowed) && balance_flag_changed) {
                if (cpuset_v2())
                        cpuset_force_rebuild();
                else
                        rebuild_sched_domains_locked();
        }

        if (spread_flag_changed)
                cpuset1_update_tasks_flags(cs);
out:
        free_cpuset(trialcs);
        return err;
}

/**
 * update_prstate - update partition_root_state
 * @cs: the cpuset to update
 * @new_prs: new partition root state
 * Return: 0 if successful, != 0 if error
 *
 * Call with cpuset_mutex held.
 */
static int update_prstate(struct cpuset *cs, int new_prs)
{
        int err = PERR_NONE, old_prs = cs->partition_root_state;
        struct cpuset *parent = parent_cs(cs);
        struct tmpmasks tmpmask;
        bool isolcpus_updated = false;

        if (old_prs == new_prs)
                return 0;

        /*
         * Treat a previously invalid partition root as if it is a "member".
         */
        if (new_prs && is_partition_invalid(cs))
                old_prs = PRS_MEMBER;

        if (alloc_tmpmasks(&tmpmask))
                return -ENOMEM;

        err = update_partition_exclusive_flag(cs, new_prs);
        if (err)
                goto out;

        if (!old_prs) {
                /*
                 * cpus_allowed and exclusive_cpus cannot be both empty.
                 */
                if (xcpus_empty(cs)) {
                        err = PERR_CPUSEMPTY;
                        goto out;
                }

                /*
                 * We don't support the creation of a new local partition with
                 * a remote partition underneath it. This unsupported
                 * setting can happen only if parent is the top_cpuset because
                 * a remote partition cannot be created underneath an existing
                 * local or remote partition.
                 */
                if ((parent == &top_cpuset) &&
                    cpumask_intersects(cs->exclusive_cpus, subpartitions_cpus)) {
                        err = PERR_REMOTE;
                        goto out;
                }

                /*
                 * If parent is valid partition, enable local partiion.
                 * Otherwise, enable a remote partition.
                 */
                if (is_partition_valid(parent)) {
                        enum partition_cmd cmd = (new_prs == PRS_ROOT)
                                               ? partcmd_enable : partcmd_enablei;

                        err = update_parent_effective_cpumask(cs, cmd, NULL, &tmpmask);
                } else {
                        err = remote_partition_enable(cs, new_prs, &tmpmask);
                }
        } else if (old_prs && new_prs) {
                /*
                 * A change in load balance state only, no change in cpumasks.
                 * Need to update isolated_cpus.
                 */
                if (((new_prs == PRS_ISOLATED) &&
                     !isolated_cpus_can_update(cs->effective_xcpus, NULL)) ||
                    prstate_housekeeping_conflict(new_prs, cs->effective_xcpus))
                        err = PERR_HKEEPING;
                else
                        isolcpus_updated = true;
        } else {
                /*
                 * Switching back to member is always allowed even if it
                 * disables child partitions.
                 */
                if (is_remote_partition(cs))
                        remote_partition_disable(cs, &tmpmask);
                else
                        update_parent_effective_cpumask(cs, partcmd_disable,
                                                        NULL, &tmpmask);

                /*
                 * Invalidation of child partitions will be done in
                 * update_cpumasks_hier().
                 */
        }
out:
        /*
         * Make partition invalid & disable CS_CPU_EXCLUSIVE if an error
         * happens.
         */
        if (err) {
                new_prs = -new_prs;
                update_partition_exclusive_flag(cs, new_prs);
        }

        spin_lock_irq(&callback_lock);
        cs->partition_root_state = new_prs;
        WRITE_ONCE(cs->prs_err, err);
        if (!is_partition_valid(cs))
                reset_partition_data(cs);
        else if (isolcpus_updated)
                isolated_cpus_update(old_prs, new_prs, cs->effective_xcpus);
        spin_unlock_irq(&callback_lock);

        /* Force update if switching back to member & update effective_xcpus */
        update_cpumasks_hier(cs, &tmpmask, !new_prs);

        /* A newly created partition must have effective_xcpus set */
        WARN_ON_ONCE(!old_prs && (new_prs > 0)
                              && cpumask_empty(cs->effective_xcpus));

        /* Update sched domains and load balance flag */
        update_partition_sd_lb(cs, old_prs);

        notify_partition_change(cs, old_prs);
        if (force_sd_rebuild)
                rebuild_sched_domains_locked();
        free_tmpmasks(&tmpmask);
        return 0;
}

static struct cpuset *cpuset_attach_old_cs;

/*
 * Check to see if a cpuset can accept a new task
 * For v1, cpus_allowed and mems_allowed can't be empty.
 * For v2, effective_cpus can't be empty.
 * Note that in v1, effective_cpus = cpus_allowed.
 */
static int cpuset_can_attach_check(struct cpuset *cs)
{
        if (cpumask_empty(cs->effective_cpus) ||
           (!is_in_v2_mode() && nodes_empty(cs->mems_allowed)))
                return -ENOSPC;
        return 0;
}

static void reset_migrate_dl_data(struct cpuset *cs)
{
        cs->nr_migrate_dl_tasks = 0;
        cs->sum_migrate_dl_bw = 0;
}

/* Called by cgroups to determine if a cpuset is usable; cpuset_mutex held */
static int cpuset_can_attach(struct cgroup_taskset *tset)
{
        struct cgroup_subsys_state *css;
        struct cpuset *cs, *oldcs;
        struct task_struct *task;
        bool setsched_check;
        int ret;

        /* used later by cpuset_attach() */
        cpuset_attach_old_cs = task_cs(cgroup_taskset_first(tset, &css));
        oldcs = cpuset_attach_old_cs;
        cs = css_cs(css);

        mutex_lock(&cpuset_mutex);

        /* Check to see if task is allowed in the cpuset */
        ret = cpuset_can_attach_check(cs);
        if (ret)
                goto out_unlock;

        /*
         * Skip rights over task setsched check in v2 when nothing changes,
         * migration permission derives from hierarchy ownership in
         * cgroup_procs_write_permission()).
         */
        setsched_check = !cpuset_v2() ||
                !cpumask_equal(cs->effective_cpus, oldcs->effective_cpus) ||
                !nodes_equal(cs->effective_mems, oldcs->effective_mems);

        /*
         * A v1 cpuset with tasks will have no CPU left only when CPU hotplug
         * brings the last online CPU offline as users are not allowed to empty
         * cpuset.cpus when there are active tasks inside. When that happens,
         * we should allow tasks to migrate out without security check to make
         * sure they will be able to run after migration.
         */
        if (!is_in_v2_mode() && cpumask_empty(oldcs->effective_cpus))
                setsched_check = false;

        cgroup_taskset_for_each(task, css, tset) {
                ret = task_can_attach(task);
                if (ret)
                        goto out_unlock;

                if (setsched_check) {
                        ret = security_task_setscheduler(task);
                        if (ret)
                                goto out_unlock;
                }

                if (dl_task(task)) {
                        cs->nr_migrate_dl_tasks++;
                        cs->sum_migrate_dl_bw += task->dl.dl_bw;
                }
        }

        if (!cs->nr_migrate_dl_tasks)
                goto out_success;

        if (!cpumask_intersects(oldcs->effective_cpus, cs->effective_cpus)) {
                int cpu = cpumask_any_and(cpu_active_mask, cs->effective_cpus);

                if (unlikely(cpu >= nr_cpu_ids)) {
                        reset_migrate_dl_data(cs);
                        ret = -EINVAL;
                        goto out_unlock;
                }

                ret = dl_bw_alloc(cpu, cs->sum_migrate_dl_bw);
                if (ret) {
                        reset_migrate_dl_data(cs);
                        goto out_unlock;
                }
        }

out_success:
        /*
         * Mark attach is in progress.  This makes validate_change() fail
         * changes which zero cpus/mems_allowed.
         */
        cs->attach_in_progress++;
out_unlock:
        mutex_unlock(&cpuset_mutex);
        return ret;
}

static void cpuset_cancel_attach(struct cgroup_taskset *tset)
{
        struct cgroup_subsys_state *css;
        struct cpuset *cs;

        cgroup_taskset_first(tset, &css);
        cs = css_cs(css);

        mutex_lock(&cpuset_mutex);
        dec_attach_in_progress_locked(cs);

        if (cs->nr_migrate_dl_tasks) {
                int cpu = cpumask_any(cs->effective_cpus);

                dl_bw_free(cpu, cs->sum_migrate_dl_bw);
                reset_migrate_dl_data(cs);
        }

        mutex_unlock(&cpuset_mutex);
}

/*
 * Protected by cpuset_mutex. cpus_attach is used only by cpuset_attach_task()
 * but we can't allocate it dynamically there.  Define it global and
 * allocate from cpuset_init().
 */
static cpumask_var_t cpus_attach;
static nodemask_t cpuset_attach_nodemask_to;

static void cpuset_attach_task(struct cpuset *cs, struct task_struct *task)
{
        lockdep_assert_cpuset_lock_held();

        if (cs != &top_cpuset)
                guarantee_active_cpus(task, cpus_attach);
        else
                cpumask_andnot(cpus_attach, task_cpu_possible_mask(task),
                               subpartitions_cpus);
        /*
         * can_attach beforehand should guarantee that this doesn't
         * fail.  TODO: have a better way to handle failure here
         */
        WARN_ON_ONCE(set_cpus_allowed_ptr(task, cpus_attach));

        cpuset_change_task_nodemask(task, &cpuset_attach_nodemask_to);
        cpuset1_update_task_spread_flags(cs, task);
}

static void cpuset_attach(struct cgroup_taskset *tset)
{
        struct task_struct *task;
        struct task_struct *leader;
        struct cgroup_subsys_state *css;
        struct cpuset *cs;
        struct cpuset *oldcs = cpuset_attach_old_cs;
        bool cpus_updated, mems_updated;
        bool queue_task_work = false;

        cgroup_taskset_first(tset, &css);
        cs = css_cs(css);

        lockdep_assert_cpus_held();     /* see cgroup_attach_lock() */
        mutex_lock(&cpuset_mutex);
        cpus_updated = !cpumask_equal(cs->effective_cpus,
                                      oldcs->effective_cpus);
        mems_updated = !nodes_equal(cs->effective_mems, oldcs->effective_mems);

        /*
         * In the default hierarchy, enabling cpuset in the child cgroups
         * will trigger a number of cpuset_attach() calls with no change
         * in effective cpus and mems. In that case, we can optimize out
         * by skipping the task iteration and update.
         */
        if (cpuset_v2() && !cpus_updated && !mems_updated) {
                cpuset_attach_nodemask_to = cs->effective_mems;
                goto out;
        }

        guarantee_online_mems(cs, &cpuset_attach_nodemask_to);

        cgroup_taskset_for_each(task, css, tset)
                cpuset_attach_task(cs, task);

        /*
         * Change mm for all threadgroup leaders. This is expensive and may
         * sleep and should be moved outside migration path proper. Skip it
         * if there is no change in effective_mems and CS_MEMORY_MIGRATE is
         * not set.
         */
        cpuset_attach_nodemask_to = cs->effective_mems;
        if (!is_memory_migrate(cs) && !mems_updated)
                goto out;

        cgroup_taskset_for_each_leader(leader, css, tset) {
                struct mm_struct *mm = get_task_mm(leader);

                if (mm) {
                        mpol_rebind_mm(mm, &cpuset_attach_nodemask_to);

                        /*
                         * old_mems_allowed is the same with mems_allowed
                         * here, except if this task is being moved
                         * automatically due to hotplug.  In that case
                         * @mems_allowed has been updated and is empty, so
                         * @old_mems_allowed is the right nodesets that we
                         * migrate mm from.
                         */
                        if (is_memory_migrate(cs)) {
                                cpuset_migrate_mm(mm, &oldcs->old_mems_allowed,
                                                  &cpuset_attach_nodemask_to);
                                queue_task_work = true;
                        } else
                                mmput(mm);
                }
        }

out:
        if (queue_task_work)
                schedule_flush_migrate_mm();
        cs->old_mems_allowed = cpuset_attach_nodemask_to;

        if (cs->nr_migrate_dl_tasks) {
                cs->nr_deadline_tasks += cs->nr_migrate_dl_tasks;
                oldcs->nr_deadline_tasks -= cs->nr_migrate_dl_tasks;
                reset_migrate_dl_data(cs);
        }

        dec_attach_in_progress_locked(cs);

        mutex_unlock(&cpuset_mutex);
}

/*
 * Common handling for a write to a "cpus" or "mems" file.
 */
ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
                                    char *buf, size_t nbytes, loff_t off)
{
        struct cpuset *cs = css_cs(of_css(of));
        struct cpuset *trialcs;
        int retval = -ENODEV;

        /* root is read-only */
        if (cs == &top_cpuset)
                return -EACCES;

        buf = strstrip(buf);
        cpuset_full_lock();
        if (!is_cpuset_online(cs))
                goto out_unlock;

        trialcs = dup_or_alloc_cpuset(cs);
        if (!trialcs) {
                retval = -ENOMEM;
                goto out_unlock;
        }

        switch (of_cft(of)->private) {
        case FILE_CPULIST:
                retval = update_cpumask(cs, trialcs, buf);
                break;
        case FILE_EXCLUSIVE_CPULIST:
                retval = update_exclusive_cpumask(cs, trialcs, buf);
                break;
        case FILE_MEMLIST:
                retval = update_nodemask(cs, trialcs, buf);
                break;
        default:
                retval = -EINVAL;
                break;
        }

        free_cpuset(trialcs);
out_unlock:
        cpuset_update_sd_hk_unlock();
        if (of_cft(of)->private == FILE_MEMLIST)
                schedule_flush_migrate_mm();
        return retval ?: nbytes;
}

/*
 * These ascii lists should be read in a single call, by using a user
 * buffer large enough to hold the entire map.  If read in smaller
 * chunks, there is no guarantee of atomicity.  Since the display format
 * used, list of ranges of sequential numbers, is variable length,
 * and since these maps can change value dynamically, one could read
 * gibberish by doing partial reads while a list was changing.
 */
int cpuset_common_seq_show(struct seq_file *sf, void *v)
{
        struct cpuset *cs = css_cs(seq_css(sf));
        cpuset_filetype_t type = seq_cft(sf)->private;
        int ret = 0;

        spin_lock_irq(&callback_lock);

        switch (type) {
        case FILE_CPULIST:
                seq_printf(sf, "%*pbl\n", cpumask_pr_args(cs->cpus_allowed));
                break;
        case FILE_MEMLIST:
                seq_printf(sf, "%*pbl\n", nodemask_pr_args(&cs->mems_allowed));
                break;
        case FILE_EFFECTIVE_CPULIST:
                seq_printf(sf, "%*pbl\n", cpumask_pr_args(cs->effective_cpus));
                break;
        case FILE_EFFECTIVE_MEMLIST:
                seq_printf(sf, "%*pbl\n", nodemask_pr_args(&cs->effective_mems));
                break;
        case FILE_EXCLUSIVE_CPULIST:
                seq_printf(sf, "%*pbl\n", cpumask_pr_args(cs->exclusive_cpus));
                break;
        case FILE_EFFECTIVE_XCPULIST:
                seq_printf(sf, "%*pbl\n", cpumask_pr_args(cs->effective_xcpus));
                break;
        case FILE_SUBPARTS_CPULIST:
                seq_printf(sf, "%*pbl\n", cpumask_pr_args(subpartitions_cpus));
                break;
        case FILE_ISOLATED_CPULIST:
                seq_printf(sf, "%*pbl\n", cpumask_pr_args(isolated_cpus));
                break;
        default:
                ret = -EINVAL;
        }

        spin_unlock_irq(&callback_lock);
        return ret;
}

static int cpuset_partition_show(struct seq_file *seq, void *v)
{
        struct cpuset *cs = css_cs(seq_css(seq));
        const char *err, *type = NULL;

        switch (cs->partition_root_state) {
        case PRS_ROOT:
                seq_puts(seq, "root\n");
                break;
        case PRS_ISOLATED:
                seq_puts(seq, "isolated\n");
                break;
        case PRS_MEMBER:
                seq_puts(seq, "member\n");
                break;
        case PRS_INVALID_ROOT:
                type = "root";
                fallthrough;
        case PRS_INVALID_ISOLATED:
                if (!type)
                        type = "isolated";
                err = perr_strings[READ_ONCE(cs->prs_err)];
                if (err)
                        seq_printf(seq, "%s invalid (%s)\n", type, err);
                else
                        seq_printf(seq, "%s invalid\n", type);
                break;
        }
        return 0;
}

static ssize_t cpuset_partition_write(struct kernfs_open_file *of, char *buf,
                                     size_t nbytes, loff_t off)
{
        struct cpuset *cs = css_cs(of_css(of));
        int val;
        int retval = -ENODEV;

        buf = strstrip(buf);

        if (!strcmp(buf, "root"))
                val = PRS_ROOT;
        else if (!strcmp(buf, "member"))
                val = PRS_MEMBER;
        else if (!strcmp(buf, "isolated"))
                val = PRS_ISOLATED;
        else
                return -EINVAL;

        cpuset_full_lock();
        if (is_cpuset_online(cs))
                retval = update_prstate(cs, val);
        cpuset_update_sd_hk_unlock();
        return retval ?: nbytes;
}

/*
 * This is currently a minimal set for the default hierarchy. It can be
 * expanded later on by migrating more features and control files from v1.
 */
static struct cftype dfl_files[] = {
        {
                .name = "cpus",
                .seq_show = cpuset_common_seq_show,
                .write = cpuset_write_resmask,
                .max_write_len = (100U + 6 * NR_CPUS),
                .private = FILE_CPULIST,
                .flags = CFTYPE_NOT_ON_ROOT,
        },

        {
                .name = "mems",
                .seq_show = cpuset_common_seq_show,
                .write = cpuset_write_resmask,
                .max_write_len = (100U + 6 * MAX_NUMNODES),
                .private = FILE_MEMLIST,
                .flags = CFTYPE_NOT_ON_ROOT,
        },

        {
                .name = "cpus.effective",
                .seq_show = cpuset_common_seq_show,
                .private = FILE_EFFECTIVE_CPULIST,
        },

        {
                .name = "mems.effective",
                .seq_show = cpuset_common_seq_show,
                .private = FILE_EFFECTIVE_MEMLIST,
        },

        {
                .name = "cpus.partition",
                .seq_show = cpuset_partition_show,
                .write = cpuset_partition_write,
                .private = FILE_PARTITION_ROOT,
                .flags = CFTYPE_NOT_ON_ROOT,
                .file_offset = offsetof(struct cpuset, partition_file),
        },

        {
                .name = "cpus.exclusive",
                .seq_show = cpuset_common_seq_show,
                .write = cpuset_write_resmask,
                .max_write_len = (100U + 6 * NR_CPUS),
                .private = FILE_EXCLUSIVE_CPULIST,
                .flags = CFTYPE_NOT_ON_ROOT,
        },

        {
                .name = "cpus.exclusive.effective",
                .seq_show = cpuset_common_seq_show,
                .private = FILE_EFFECTIVE_XCPULIST,
                .flags = CFTYPE_NOT_ON_ROOT,
        },

        {
                .name = "cpus.subpartitions",
                .seq_show = cpuset_common_seq_show,
                .private = FILE_SUBPARTS_CPULIST,
                .flags = CFTYPE_ONLY_ON_ROOT | CFTYPE_DEBUG,
        },

        {
                .name = "cpus.isolated",
                .seq_show = cpuset_common_seq_show,
                .private = FILE_ISOLATED_CPULIST,
                .flags = CFTYPE_ONLY_ON_ROOT,
        },

        { }     /* terminate */
};


/**
 * cpuset_css_alloc - Allocate a cpuset css
 * @parent_css: Parent css of the control group that the new cpuset will be
 *              part of
 * Return: cpuset css on success, -ENOMEM on failure.
 *
 * Allocate and initialize a new cpuset css, for non-NULL @parent_css, return
 * top cpuset css otherwise.
 */
static struct cgroup_subsys_state *
cpuset_css_alloc(struct cgroup_subsys_state *parent_css)
{
        struct cpuset *cs;

        if (!parent_css)
                return &top_cpuset.css;

        cs = dup_or_alloc_cpuset(NULL);
        if (!cs)
                return ERR_PTR(-ENOMEM);

        __set_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
        cpuset1_init(cs);

        /* Set CS_MEMORY_MIGRATE for default hierarchy */
        if (cpuset_v2())
                __set_bit(CS_MEMORY_MIGRATE, &cs->flags);

        return &cs->css;
}

static int cpuset_css_online(struct cgroup_subsys_state *css)
{
        struct cpuset *cs = css_cs(css);
        struct cpuset *parent = parent_cs(cs);

        if (!parent)
                return 0;

        cpuset_full_lock();
        /*
         * For v2, clear CS_SCHED_LOAD_BALANCE if parent is isolated
         */
        if (cpuset_v2() && !is_sched_load_balance(parent))
                clear_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);

        cpuset_inc();

        spin_lock_irq(&callback_lock);
        if (is_in_v2_mode()) {
                cpumask_copy(cs->effective_cpus, parent->effective_cpus);
                cs->effective_mems = parent->effective_mems;
        }
        spin_unlock_irq(&callback_lock);
        cpuset1_online_css(css);

        cpuset_full_unlock();
        return 0;
}

/*
 * If the cpuset being removed has its flag 'sched_load_balance'
 * enabled, then simulate turning sched_load_balance off, which
 * will call rebuild_sched_domains_locked(). That is not needed
 * in the default hierarchy where only changes in partition
 * will cause repartitioning.
 */
static void cpuset_css_offline(struct cgroup_subsys_state *css)
{
        struct cpuset *cs = css_cs(css);

        cpuset_full_lock();
        if (!cpuset_v2() && is_sched_load_balance(cs))
                cpuset_update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);

        cpuset_dec();
        cpuset_full_unlock();
}

/*
 * If a dying cpuset has the 'cpus.partition' enabled, turn it off by
 * changing it back to member to free its exclusive CPUs back to the pool to
 * be used by other online cpusets.
 */
static void cpuset_css_killed(struct cgroup_subsys_state *css)
{
        struct cpuset *cs = css_cs(css);

        cpuset_full_lock();
        /* Reset valid partition back to member */
        if (is_partition_valid(cs))
                update_prstate(cs, PRS_MEMBER);
        cpuset_update_sd_hk_unlock();
}

static void cpuset_css_free(struct cgroup_subsys_state *css)
{
        struct cpuset *cs = css_cs(css);

        free_cpuset(cs);
}

static void cpuset_bind(struct cgroup_subsys_state *root_css)
{
        mutex_lock(&cpuset_mutex);
        spin_lock_irq(&callback_lock);

        if (is_in_v2_mode()) {
                cpumask_copy(top_cpuset.cpus_allowed, cpu_possible_mask);
                cpumask_copy(top_cpuset.effective_xcpus, cpu_possible_mask);
                top_cpuset.mems_allowed = node_possible_map;
        } else {
                cpumask_copy(top_cpuset.cpus_allowed,
                             top_cpuset.effective_cpus);
                top_cpuset.mems_allowed = top_cpuset.effective_mems;
        }

        spin_unlock_irq(&callback_lock);
        mutex_unlock(&cpuset_mutex);
}

/*
 * In case the child is cloned into a cpuset different from its parent,
 * additional checks are done to see if the move is allowed.
 */
static int cpuset_can_fork(struct task_struct *task, struct css_set *cset)
{
        struct cpuset *cs = css_cs(cset->subsys[cpuset_cgrp_id]);
        bool same_cs;
        int ret;

        rcu_read_lock();
        same_cs = (cs == task_cs(current));
        rcu_read_unlock();

        if (same_cs)
                return 0;

        lockdep_assert_held(&cgroup_mutex);
        mutex_lock(&cpuset_mutex);

        /* Check to see if task is allowed in the cpuset */
        ret = cpuset_can_attach_check(cs);
        if (ret)
                goto out_unlock;

        ret = task_can_attach(task);
        if (ret)
                goto out_unlock;

        ret = security_task_setscheduler(task);
        if (ret)
                goto out_unlock;

        /*
         * Mark attach is in progress.  This makes validate_change() fail
         * changes which zero cpus/mems_allowed.
         */
        cs->attach_in_progress++;
out_unlock:
        mutex_unlock(&cpuset_mutex);
        return ret;
}

static void cpuset_cancel_fork(struct task_struct *task, struct css_set *cset)
{
        struct cpuset *cs = css_cs(cset->subsys[cpuset_cgrp_id]);
        bool same_cs;

        rcu_read_lock();
        same_cs = (cs == task_cs(current));
        rcu_read_unlock();

        if (same_cs)
                return;

        dec_attach_in_progress(cs);
}

/*
 * Make sure the new task conform to the current state of its parent,
 * which could have been changed by cpuset just after it inherits the
 * state from the parent and before it sits on the cgroup's task list.
 */
static void cpuset_fork(struct task_struct *task)
{
        struct cpuset *cs;
        bool same_cs;

        rcu_read_lock();
        cs = task_cs(task);
        same_cs = (cs == task_cs(current));
        rcu_read_unlock();

        if (same_cs) {
                if (cs == &top_cpuset)
                        return;

                set_cpus_allowed_ptr(task, current->cpus_ptr);
                task->mems_allowed = current->mems_allowed;
                return;
        }

        /* CLONE_INTO_CGROUP */
        mutex_lock(&cpuset_mutex);
        guarantee_online_mems(cs, &cpuset_attach_nodemask_to);
        cpuset_attach_task(cs, task);

        dec_attach_in_progress_locked(cs);
        mutex_unlock(&cpuset_mutex);
}

struct cgroup_subsys cpuset_cgrp_subsys = {
        .css_alloc      = cpuset_css_alloc,
        .css_online     = cpuset_css_online,
        .css_offline    = cpuset_css_offline,
        .css_killed     = cpuset_css_killed,
        .css_free       = cpuset_css_free,
        .can_attach     = cpuset_can_attach,
        .cancel_attach  = cpuset_cancel_attach,
        .attach         = cpuset_attach,
        .bind           = cpuset_bind,
        .can_fork       = cpuset_can_fork,
        .cancel_fork    = cpuset_cancel_fork,
        .fork           = cpuset_fork,
#ifdef CONFIG_CPUSETS_V1
        .legacy_cftypes = cpuset1_files,
#endif
        .dfl_cftypes    = dfl_files,
        .early_init     = true,
        .threaded       = true,
};

/**
 * cpuset_init - initialize cpusets at system boot
 *
 * Description: Initialize top_cpuset
 **/

int __init cpuset_init(void)
{
        BUG_ON(!alloc_cpumask_var(&top_cpuset.cpus_allowed, GFP_KERNEL));
        BUG_ON(!alloc_cpumask_var(&top_cpuset.effective_cpus, GFP_KERNEL));
        BUG_ON(!alloc_cpumask_var(&top_cpuset.effective_xcpus, GFP_KERNEL));
        BUG_ON(!alloc_cpumask_var(&top_cpuset.exclusive_cpus, GFP_KERNEL));
        BUG_ON(!zalloc_cpumask_var(&subpartitions_cpus, GFP_KERNEL));
        BUG_ON(!zalloc_cpumask_var(&isolated_cpus, GFP_KERNEL));
        BUG_ON(!zalloc_cpumask_var(&isolated_hk_cpus, GFP_KERNEL));

        cpumask_setall(top_cpuset.cpus_allowed);
        nodes_setall(top_cpuset.mems_allowed);
        cpumask_setall(top_cpuset.effective_cpus);
        cpumask_setall(top_cpuset.effective_xcpus);
        cpumask_setall(top_cpuset.exclusive_cpus);
        nodes_setall(top_cpuset.effective_mems);

        cpuset1_init(&top_cpuset);

        BUG_ON(!alloc_cpumask_var(&cpus_attach, GFP_KERNEL));

        if (housekeeping_enabled(HK_TYPE_DOMAIN_BOOT))
                cpumask_andnot(isolated_cpus, cpu_possible_mask,
                               housekeeping_cpumask(HK_TYPE_DOMAIN_BOOT));

        return 0;
}

static void
hotplug_update_tasks(struct cpuset *cs,
                     struct cpumask *new_cpus, nodemask_t *new_mems,
                     bool cpus_updated, bool mems_updated)
{
        /* A partition root is allowed to have empty effective cpus */
        if (cpumask_empty(new_cpus) && !is_partition_valid(cs))
                cpumask_copy(new_cpus, parent_cs(cs)->effective_cpus);
        if (nodes_empty(*new_mems))
                *new_mems = parent_cs(cs)->effective_mems;

        spin_lock_irq(&callback_lock);
        cpumask_copy(cs->effective_cpus, new_cpus);
        cs->effective_mems = *new_mems;
        spin_unlock_irq(&callback_lock);

        if (cpus_updated)
                cpuset_update_tasks_cpumask(cs, new_cpus);
        if (mems_updated)
                cpuset_update_tasks_nodemask(cs);
}

void cpuset_force_rebuild(void)
{
        force_sd_rebuild = true;
}

/**
 * cpuset_hotplug_update_tasks - update tasks in a cpuset for hotunplug
 * @cs: cpuset in interest
 * @tmp: the tmpmasks structure pointer
 *
 * Compare @cs's cpu and mem masks against top_cpuset and if some have gone
 * offline, update @cs accordingly.  If @cs ends up with no CPU or memory,
 * all its tasks are moved to the nearest ancestor with both resources.
 */
static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp)
{
        static cpumask_t new_cpus;
        static nodemask_t new_mems;
        bool cpus_updated;
        bool mems_updated;
        bool remote;
        int partcmd = -1;
        struct cpuset *parent;
retry:
        wait_event(cpuset_attach_wq, cs->attach_in_progress == 0);

        mutex_lock(&cpuset_mutex);

        /*
         * We have raced with task attaching. We wait until attaching
         * is finished, so we won't attach a task to an empty cpuset.
         */
        if (cs->attach_in_progress) {
                mutex_unlock(&cpuset_mutex);
                goto retry;
        }

        parent = parent_cs(cs);
        compute_effective_cpumask(&new_cpus, cs, parent);
        nodes_and(new_mems, cs->mems_allowed, parent->effective_mems);

        if (!tmp || !cs->partition_root_state)
                goto update_tasks;

        /*
         * Compute effective_cpus for valid partition root, may invalidate
         * child partition roots if necessary.
         */
        remote = is_remote_partition(cs);
        if (remote || (is_partition_valid(cs) && is_partition_valid(parent)))
                compute_partition_effective_cpumask(cs, &new_cpus);

        if (remote && (cpumask_empty(subpartitions_cpus) ||
                        (cpumask_empty(&new_cpus) &&
                         partition_is_populated(cs, NULL)))) {
                cs->prs_err = PERR_HOTPLUG;
                remote_partition_disable(cs, tmp);
                compute_effective_cpumask(&new_cpus, cs, parent);
                remote = false;
        }

        /*
         * Force the partition to become invalid if either one of
         * the following conditions hold:
         * 1) empty effective cpus but not valid empty partition.
         * 2) parent is invalid or doesn't grant any cpus to child
         *    partitions.
         * 3) subpartitions_cpus is empty.
         */
        if (is_local_partition(cs) &&
            (!is_partition_valid(parent) ||
             tasks_nocpu_error(parent, cs, &new_cpus) ||
             cpumask_empty(subpartitions_cpus)))
                partcmd = partcmd_invalidate;
        /*
         * On the other hand, an invalid partition root may be transitioned
         * back to a regular one with a non-empty effective xcpus.
         */
        else if (is_partition_valid(parent) && is_partition_invalid(cs) &&
                 !cpumask_empty(cs->effective_xcpus))
                partcmd = partcmd_update;

        if (partcmd >= 0) {
                update_parent_effective_cpumask(cs, partcmd, NULL, tmp);
                if ((partcmd == partcmd_invalidate) || is_partition_valid(cs)) {
                        compute_partition_effective_cpumask(cs, &new_cpus);
                        cpuset_force_rebuild();
                }
        }

update_tasks:
        cpus_updated = !cpumask_equal(&new_cpus, cs->effective_cpus);
        mems_updated = !nodes_equal(new_mems, cs->effective_mems);
        if (!cpus_updated && !mems_updated)
                goto unlock;    /* Hotplug doesn't affect this cpuset */

        if (mems_updated)
                check_insane_mems_config(&new_mems);

        if (is_in_v2_mode())
                hotplug_update_tasks(cs, &new_cpus, &new_mems,
                                     cpus_updated, mems_updated);
        else
                cpuset1_hotplug_update_tasks(cs, &new_cpus, &new_mems,
                                            cpus_updated, mems_updated);

unlock:
        mutex_unlock(&cpuset_mutex);
}

/**
 * cpuset_handle_hotplug - handle CPU/memory hot{,un}plug for a cpuset
 *
 * This function is called after either CPU or memory configuration has
 * changed and updates cpuset accordingly.  The top_cpuset is always
 * synchronized to cpu_active_mask and N_MEMORY, which is necessary in
 * order to make cpusets transparent (of no affect) on systems that are
 * actively using CPU hotplug but making no active use of cpusets.
 *
 * Non-root cpusets are only affected by offlining.  If any CPUs or memory
 * nodes have been taken down, cpuset_hotplug_update_tasks() is invoked on
 * all descendants.
 *
 * Note that CPU offlining during suspend is ignored.  We don't modify
 * cpusets across suspend/resume cycles at all.
 *
 * CPU / memory hotplug is handled synchronously.
 */
static void cpuset_handle_hotplug(void)
{
        static DECLARE_WORK(hk_sd_work, hk_sd_workfn);
        static cpumask_t new_cpus;
        static nodemask_t new_mems;
        bool cpus_updated, mems_updated;
        bool on_dfl = is_in_v2_mode();
        struct tmpmasks tmp, *ptmp = NULL;

        if (on_dfl && !alloc_tmpmasks(&tmp))
                ptmp = &tmp;

        lockdep_assert_cpus_held();
        mutex_lock(&cpuset_mutex);

        /* fetch the available cpus/mems and find out which changed how */
        cpumask_copy(&new_cpus, cpu_active_mask);
        new_mems = node_states[N_MEMORY];

        /*
         * If subpartitions_cpus is populated, it is likely that the check
         * below will produce a false positive on cpus_updated when the cpu
         * list isn't changed. It is extra work, but it is better to be safe.
         */
        cpus_updated = !cpumask_equal(top_cpuset.effective_cpus, &new_cpus) ||
                       !cpumask_empty(subpartitions_cpus);
        mems_updated = !nodes_equal(top_cpuset.effective_mems, new_mems);

        /* For v1, synchronize cpus_allowed to cpu_active_mask */
        if (cpus_updated) {
                cpuset_force_rebuild();
                spin_lock_irq(&callback_lock);
                if (!on_dfl)
                        cpumask_copy(top_cpuset.cpus_allowed, &new_cpus);
                /*
                 * Make sure that CPUs allocated to child partitions
                 * do not show up in effective_cpus. If no CPU is left,
                 * we clear the subpartitions_cpus & let the child partitions
                 * fight for the CPUs again.
                 */
                if (!cpumask_empty(subpartitions_cpus)) {
                        if (cpumask_subset(&new_cpus, subpartitions_cpus)) {
                                cpumask_clear(subpartitions_cpus);
                        } else {
                                cpumask_andnot(&new_cpus, &new_cpus,
                                               subpartitions_cpus);
                        }
                }
                cpumask_copy(top_cpuset.effective_cpus, &new_cpus);
                spin_unlock_irq(&callback_lock);
                /* we don't mess with cpumasks of tasks in top_cpuset */
        }

        /* synchronize mems_allowed to N_MEMORY */
        if (mems_updated) {
                spin_lock_irq(&callback_lock);
                if (!on_dfl)
                        top_cpuset.mems_allowed = new_mems;
                top_cpuset.effective_mems = new_mems;
                spin_unlock_irq(&callback_lock);
                cpuset_update_tasks_nodemask(&top_cpuset);
        }

        mutex_unlock(&cpuset_mutex);

        /* if cpus or mems changed, we need to propagate to descendants */
        if (cpus_updated || mems_updated) {
                struct cpuset *cs;
                struct cgroup_subsys_state *pos_css;

                rcu_read_lock();
                cpuset_for_each_descendant_pre(cs, pos_css, &top_cpuset) {
                        if (cs == &top_cpuset || !css_tryget_online(&cs->css))
                                continue;
                        rcu_read_unlock();

                        cpuset_hotplug_update_tasks(cs, ptmp);

                        rcu_read_lock();
                        css_put(&cs->css);
                }
                rcu_read_unlock();
        }

        /*
         * rebuild_sched_domains() will always be called directly if needed
         * to make sure that newly added or removed CPU will be reflected in
         * the sched domains. However, if isolated partition invalidation
         * or recreation is being done (update_housekeeping set), a work item
         * will be queued to call housekeeping_update() to update the
         * corresponding housekeeping cpumasks after some slight delay.
         *
         * We rely on WORK_STRUCT_PENDING_BIT to not requeue a work item that
         * is still pending. Before the pending bit is cleared, the work data
         * is copied out and work item dequeued. So it is possible to queue
         * the work again before the hk_sd_workfn() is invoked to process the
         * previously queued work. Since hk_sd_workfn() doesn't use the work
         * item at all, this is not a problem.
         */
        if (force_sd_rebuild)
                rebuild_sched_domains_cpuslocked();
        if (update_housekeeping)
                queue_work(system_dfl_wq, &hk_sd_work);

        free_tmpmasks(ptmp);
}

void cpuset_update_active_cpus(void)
{
        /*
         * We're inside cpu hotplug critical region which usually nests
         * inside cgroup synchronization.  Bounce actual hotplug processing
         * to a work item to avoid reverse locking order.
         */
        cpuset_handle_hotplug();
}

/*
 * Keep top_cpuset.mems_allowed tracking node_states[N_MEMORY].
 * Call this routine anytime after node_states[N_MEMORY] changes.
 * See cpuset_update_active_cpus() for CPU hotplug handling.
 */
static int cpuset_track_online_nodes(struct notifier_block *self,
                                unsigned long action, void *arg)
{
        cpuset_handle_hotplug();
        return NOTIFY_OK;
}

/**
 * cpuset_init_smp - initialize cpus_allowed
 *
 * Description: Finish top cpuset after cpu, node maps are initialized
 */
void __init cpuset_init_smp(void)
{
        /*
         * cpus_allowd/mems_allowed set to v2 values in the initial
         * cpuset_bind() call will be reset to v1 values in another
         * cpuset_bind() call when v1 cpuset is mounted.
         */
        top_cpuset.old_mems_allowed = top_cpuset.mems_allowed;

        cpumask_copy(top_cpuset.effective_cpus, cpu_active_mask);
        top_cpuset.effective_mems = node_states[N_MEMORY];

        hotplug_node_notifier(cpuset_track_online_nodes, CPUSET_CALLBACK_PRI);

        cpuset_migrate_mm_wq = alloc_ordered_workqueue("cpuset_migrate_mm", 0);
        BUG_ON(!cpuset_migrate_mm_wq);
}

/*
 * Return cpus_allowed mask from a task's cpuset.
 */
static void __cpuset_cpus_allowed_locked(struct task_struct *tsk, struct cpumask *pmask)
{
        struct cpuset *cs;

        cs = task_cs(tsk);
        if (cs != &top_cpuset)
                guarantee_active_cpus(tsk, pmask);
        /*
         * Tasks in the top cpuset won't get update to their cpumasks
         * when a hotplug online/offline event happens. So we include all
         * offline cpus in the allowed cpu list.
         */
        if ((cs == &top_cpuset) || cpumask_empty(pmask)) {
                const struct cpumask *possible_mask = task_cpu_possible_mask(tsk);

                /*
                 * We first exclude cpus allocated to partitions. If there is no
                 * allowable online cpu left, we fall back to all possible cpus.
                 */
                cpumask_andnot(pmask, possible_mask, subpartitions_cpus);
                if (!cpumask_intersects(pmask, cpu_active_mask))
                        cpumask_copy(pmask, possible_mask);
        }
}

/**
 * cpuset_cpus_allowed_locked - return cpus_allowed mask from a task's cpuset.
 * @tsk: pointer to task_struct from which to obtain cpuset->cpus_allowed.
 * @pmask: pointer to struct cpumask variable to receive cpus_allowed set.
 *
 * Similir to cpuset_cpus_allowed() except that the caller must have acquired
 * cpuset_mutex.
 */
void cpuset_cpus_allowed_locked(struct task_struct *tsk, struct cpumask *pmask)
{
        lockdep_assert_cpuset_lock_held();
        __cpuset_cpus_allowed_locked(tsk, pmask);
}

/**
 * cpuset_cpus_allowed - return cpus_allowed mask from a task's cpuset.
 * @tsk: pointer to task_struct from which to obtain cpuset->cpus_allowed.
 * @pmask: pointer to struct cpumask variable to receive cpus_allowed set.
 *
 * Description: Returns the cpumask_var_t cpus_allowed of the cpuset
 * attached to the specified @tsk.  Guaranteed to return some non-empty
 * subset of cpu_active_mask, even if this means going outside the
 * tasks cpuset, except when the task is in the top cpuset.
 **/

void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask)
{
        unsigned long flags;

        spin_lock_irqsave(&callback_lock, flags);
        __cpuset_cpus_allowed_locked(tsk, pmask);
        spin_unlock_irqrestore(&callback_lock, flags);
}

/**
 * cpuset_cpus_allowed_fallback - final fallback before complete catastrophe.
 * @tsk: pointer to task_struct with which the scheduler is struggling
 *
 * Description: In the case that the scheduler cannot find an allowed cpu in
 * tsk->cpus_allowed, we fall back to task_cs(tsk)->cpus_allowed. In legacy
 * mode however, this value is the same as task_cs(tsk)->effective_cpus,
 * which will not contain a sane cpumask during cases such as cpu hotplugging.
 * This is the absolute last resort for the scheduler and it is only used if
 * _every_ other avenue has been traveled.
 *
 * Returns true if the affinity of @tsk was changed, false otherwise.
 **/

bool cpuset_cpus_allowed_fallback(struct task_struct *tsk)
{
        const struct cpumask *possible_mask = task_cpu_possible_mask(tsk);
        const struct cpumask *cs_mask;
        bool changed = false;

        rcu_read_lock();
        cs_mask = task_cs(tsk)->cpus_allowed;
        if (is_in_v2_mode() && cpumask_subset(cs_mask, possible_mask)) {
                set_cpus_allowed_force(tsk, cs_mask);
                changed = true;
        }
        rcu_read_unlock();

        /*
         * We own tsk->cpus_allowed, nobody can change it under us.
         *
         * But we used cs && cs->cpus_allowed lockless and thus can
         * race with cgroup_attach_task() or update_cpumask() and get
         * the wrong tsk->cpus_allowed. However, both cases imply the
         * subsequent cpuset_change_cpumask()->set_cpus_allowed_ptr()
         * which takes task_rq_lock().
         *
         * If we are called after it dropped the lock we must see all
         * changes in tsk_cs()->cpus_allowed. Otherwise we can temporary
         * set any mask even if it is not right from task_cs() pov,
         * the pending set_cpus_allowed_ptr() will fix things.
         *
         * select_fallback_rq() will fix things ups and set cpu_possible_mask
         * if required.
         */
        return changed;
}

void __init cpuset_init_current_mems_allowed(void)
{
        nodes_setall(current->mems_allowed);
}

/**
 * cpuset_mems_allowed - return mems_allowed mask from a tasks cpuset.
 * @tsk: pointer to task_struct from which to obtain cpuset->mems_allowed.
 *
 * Description: Returns the nodemask_t mems_allowed of the cpuset
 * attached to the specified @tsk.  Guaranteed to return some non-empty
 * subset of node_states[N_MEMORY], even if this means going outside the
 * tasks cpuset.
 **/

nodemask_t cpuset_mems_allowed(struct task_struct *tsk)
{
        nodemask_t mask;
        unsigned long flags;

        spin_lock_irqsave(&callback_lock, flags);
        guarantee_online_mems(task_cs(tsk), &mask);
        spin_unlock_irqrestore(&callback_lock, flags);

        return mask;
}

/**
 * cpuset_nodemask_valid_mems_allowed - check nodemask vs. current mems_allowed
 * @nodemask: the nodemask to be checked
 *
 * Are any of the nodes in the nodemask allowed in current->mems_allowed?
 */
int cpuset_nodemask_valid_mems_allowed(nodemask_t *nodemask)
{
        return nodes_intersects(*nodemask, current->mems_allowed);
}

/*
 * nearest_hardwall_ancestor() - Returns the nearest mem_exclusive or
 * mem_hardwall ancestor to the specified cpuset.  Call holding
 * callback_lock.  If no ancestor is mem_exclusive or mem_hardwall
 * (an unusual configuration), then returns the root cpuset.
 */
static struct cpuset *nearest_hardwall_ancestor(struct cpuset *cs)
{
        while (!(is_mem_exclusive(cs) || is_mem_hardwall(cs)) && parent_cs(cs))
                cs = parent_cs(cs);
        return cs;
}

/*
 * cpuset_current_node_allowed - Can current task allocate on a memory node?
 * @node: is this an allowed node?
 * @gfp_mask: memory allocation flags
 *
 * If we're in interrupt, yes, we can always allocate.  If @node is set in
 * current's mems_allowed, yes.  If it's not a __GFP_HARDWALL request and this
 * node is set in the nearest hardwalled cpuset ancestor to current's cpuset,
 * yes.  If current has access to memory reserves as an oom victim, yes.
 * Otherwise, no.
 *
 * GFP_USER allocations are marked with the __GFP_HARDWALL bit,
 * and do not allow allocations outside the current tasks cpuset
 * unless the task has been OOM killed.
 * GFP_KERNEL allocations are not so marked, so can escape to the
 * nearest enclosing hardwalled ancestor cpuset.
 *
 * Scanning up parent cpusets requires callback_lock.  The
 * __alloc_pages() routine only calls here with __GFP_HARDWALL bit
 * _not_ set if it's a GFP_KERNEL allocation, and all nodes in the
 * current tasks mems_allowed came up empty on the first pass over
 * the zonelist.  So only GFP_KERNEL allocations, if all nodes in the
 * cpuset are short of memory, might require taking the callback_lock.
 *
 * The first call here from mm/page_alloc:get_page_from_freelist()
 * has __GFP_HARDWALL set in gfp_mask, enforcing hardwall cpusets,
 * so no allocation on a node outside the cpuset is allowed (unless
 * in interrupt, of course).
 *
 * The second pass through get_page_from_freelist() doesn't even call
 * here for GFP_ATOMIC calls.  For those calls, the __alloc_pages()
 * variable 'wait' is not set, and the bit ALLOC_CPUSET is not set
 * in alloc_flags.  That logic and the checks below have the combined
 * affect that:
 *      in_interrupt - any node ok (current task context irrelevant)
 *      GFP_ATOMIC   - any node ok
 *      tsk_is_oom_victim   - any node ok
 *      GFP_KERNEL   - any node in enclosing hardwalled cpuset ok
 *      GFP_USER     - only nodes in current tasks mems allowed ok.
 */
bool cpuset_current_node_allowed(int node, gfp_t gfp_mask)
{
        struct cpuset *cs;              /* current cpuset ancestors */
        bool allowed;                   /* is allocation in zone z allowed? */
        unsigned long flags;

        if (in_interrupt())
                return true;
        if (node_isset(node, current->mems_allowed))
                return true;
        /*
         * Allow tasks that have access to memory reserves because they have
         * been OOM killed to get memory anywhere.
         */
        if (unlikely(tsk_is_oom_victim(current)))
                return true;
        if (gfp_mask & __GFP_HARDWALL)  /* If hardwall request, stop here */
                return false;

        if (current->flags & PF_EXITING) /* Let dying task have memory */
                return true;

        /* Not hardwall and node outside mems_allowed: scan up cpusets */
        spin_lock_irqsave(&callback_lock, flags);

        cs = nearest_hardwall_ancestor(task_cs(current));
        allowed = node_isset(node, cs->mems_allowed);

        spin_unlock_irqrestore(&callback_lock, flags);
        return allowed;
}

/**
 * cpuset_nodes_allowed - return effective_mems mask from a cgroup cpuset.
 * @cgroup: pointer to struct cgroup.
 * @mask: pointer to struct nodemask_t to be returned.
 *
 * Returns effective_mems mask from a cgroup cpuset if it is cgroup v2 and
 * has cpuset subsys. Otherwise, returns node_states[N_MEMORY].
 *
 * This function intentionally avoids taking the cpuset_mutex or callback_lock
 * when accessing effective_mems. This is because the obtained effective_mems
 * is stale immediately after the query anyway (e.g., effective_mems is updated
 * immediately after releasing the lock but before returning).
 *
 * As a result, returned @mask may be empty because cs->effective_mems can be
 * rebound during this call. Besides, nodes in @mask are not guaranteed to be
 * online due to hot plugins. Callers should check the mask for validity on
 * return based on its subsequent use.
 **/
void cpuset_nodes_allowed(struct cgroup *cgroup, nodemask_t *mask)
{
        struct cgroup_subsys_state *css;
        struct cpuset *cs;

        /*
         * In v1, mem_cgroup and cpuset are unlikely in the same hierarchy
         * and mems_allowed is likely to be empty even if we could get to it,
         * so return directly to avoid taking a global lock on the empty check.
         */
        if (!cgroup || !cpuset_v2()) {
                nodes_copy(*mask, node_states[N_MEMORY]);
                return;
        }

        css = cgroup_get_e_css(cgroup, &cpuset_cgrp_subsys);
        if (!css) {
                nodes_copy(*mask, node_states[N_MEMORY]);
                return;
        }

        /*
         * The reference taken via cgroup_get_e_css is sufficient to
         * protect css, but it does not imply safe accesses to effective_mems.
         *
         * Normally, accessing effective_mems would require the cpuset_mutex
         * or callback_lock - but the correctness of this information is stale
         * immediately after the query anyway. We do not acquire the lock
         * during this process to save lock contention in exchange for racing
         * against mems_allowed rebinds.
         */
        cs = container_of(css, struct cpuset, css);
        nodes_copy(*mask, cs->effective_mems);
        css_put(css);
}

/**
 * cpuset_spread_node() - On which node to begin search for a page
 * @rotor: round robin rotor
 *
 * If a task is marked PF_SPREAD_PAGE or PF_SPREAD_SLAB (as for
 * tasks in a cpuset with is_spread_page or is_spread_slab set),
 * and if the memory allocation used cpuset_mem_spread_node()
 * to determine on which node to start looking, as it will for
 * certain page cache or slab cache pages such as used for file
 * system buffers and inode caches, then instead of starting on the
 * local node to look for a free page, rather spread the starting
 * node around the tasks mems_allowed nodes.
 *
 * We don't have to worry about the returned node being offline
 * because "it can't happen", and even if it did, it would be ok.
 *
 * The routines calling guarantee_online_mems() are careful to
 * only set nodes in task->mems_allowed that are online.  So it
 * should not be possible for the following code to return an
 * offline node.  But if it did, that would be ok, as this routine
 * is not returning the node where the allocation must be, only
 * the node where the search should start.  The zonelist passed to
 * __alloc_pages() will include all nodes.  If the slab allocator
 * is passed an offline node, it will fall back to the local node.
 * See kmem_cache_alloc_node().
 */
static int cpuset_spread_node(int *rotor)
{
        return *rotor = next_node_in(*rotor, current->mems_allowed);
}

/**
 * cpuset_mem_spread_node() - On which node to begin search for a file page
 */
int cpuset_mem_spread_node(void)
{
        if (current->cpuset_mem_spread_rotor == NUMA_NO_NODE)
                current->cpuset_mem_spread_rotor =
                        node_random(&current->mems_allowed);

        return cpuset_spread_node(&current->cpuset_mem_spread_rotor);
}

/**
 * cpuset_mems_allowed_intersects - Does @tsk1's mems_allowed intersect @tsk2's?
 * @tsk1: pointer to task_struct of some task.
 * @tsk2: pointer to task_struct of some other task.
 *
 * Description: Return true if @tsk1's mems_allowed intersects the
 * mems_allowed of @tsk2.  Used by the OOM killer to determine if
 * one of the task's memory usage might impact the memory available
 * to the other.
 **/

int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
                                   const struct task_struct *tsk2)
{
        return nodes_intersects(tsk1->mems_allowed, tsk2->mems_allowed);
}

/**
 * cpuset_print_current_mems_allowed - prints current's cpuset and mems_allowed
 *
 * Description: Prints current's name, cpuset name, and cached copy of its
 * mems_allowed to the kernel log.
 */
void cpuset_print_current_mems_allowed(void)
{
        struct cgroup *cgrp;

        rcu_read_lock();

        cgrp = task_cs(current)->css.cgroup;
        pr_cont(",cpuset=");
        pr_cont_cgroup_name(cgrp);
        pr_cont(",mems_allowed=%*pbl",
                nodemask_pr_args(&current->mems_allowed));

        rcu_read_unlock();
}

/* Display task mems_allowed in /proc/<pid>/status file. */
void cpuset_task_status_allowed(struct seq_file *m, struct task_struct *task)
{
        seq_printf(m, "Mems_allowed:\t%*pb\n",
                   nodemask_pr_args(&task->mems_allowed));
        seq_printf(m, "Mems_allowed_list:\t%*pbl\n",
                   nodemask_pr_args(&task->mems_allowed));
}