// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2017-2018 Christoph Hellwig.
 */

#include <linux/backing-dev.h>
#include <linux/moduleparam.h>
#include <linux/vmalloc.h>
#include <trace/events/block.h>
#include "nvme.h"

bool multipath = true;
static bool multipath_always_on;

static int multipath_param_set(const char *val, const struct kernel_param *kp)
{
        int ret;
        bool *arg = kp->arg;

        ret = param_set_bool(val, kp);
        if (ret)
                return ret;

        if (multipath_always_on && !*arg) {
                pr_err("Can't disable multipath when multipath_always_on is configured.\n");
                *arg = true;
                return -EINVAL;
        }

        return 0;
}

static const struct kernel_param_ops multipath_param_ops = {
        .set = multipath_param_set,
        .get = param_get_bool,
};

module_param_cb(multipath, &multipath_param_ops, &multipath, 0444);
MODULE_PARM_DESC(multipath,
        "turn on native support for multiple controllers per subsystem");

static int multipath_always_on_set(const char *val,
                const struct kernel_param *kp)
{
        int ret;
        bool *arg = kp->arg;

        ret = param_set_bool(val, kp);
        if (ret < 0)
                return ret;

        if (*arg)
                multipath = true;

        return 0;
}

static const struct kernel_param_ops multipath_always_on_ops = {
        .set = multipath_always_on_set,
        .get = param_get_bool,
};

module_param_cb(multipath_always_on, &multipath_always_on_ops,
                &multipath_always_on, 0444);
MODULE_PARM_DESC(multipath_always_on,
        "create multipath node always except for private namespace with non-unique nsid; note that this also implicitly enables native multipath support");

static const char *nvme_iopolicy_names[] = {
        [NVME_IOPOLICY_NUMA]    = "numa",
        [NVME_IOPOLICY_RR]      = "round-robin",
        [NVME_IOPOLICY_QD]      = "queue-depth",
};

static int iopolicy = NVME_IOPOLICY_NUMA;

static int nvme_set_iopolicy(const char *val, const struct kernel_param *kp)
{
        if (!val)
                return -EINVAL;
        if (!strncmp(val, "numa", 4))
                iopolicy = NVME_IOPOLICY_NUMA;
        else if (!strncmp(val, "round-robin", 11))
                iopolicy = NVME_IOPOLICY_RR;
        else if (!strncmp(val, "queue-depth", 11))
                iopolicy = NVME_IOPOLICY_QD;
        else
                return -EINVAL;

        return 0;
}

static int nvme_get_iopolicy(char *buf, const struct kernel_param *kp)
{
        return sprintf(buf, "%s\n", nvme_iopolicy_names[iopolicy]);
}

module_param_call(iopolicy, nvme_set_iopolicy, nvme_get_iopolicy,
        &iopolicy, 0644);
MODULE_PARM_DESC(iopolicy,
        "Default multipath I/O policy; 'numa' (default), 'round-robin' or 'queue-depth'");

void nvme_mpath_default_iopolicy(struct nvme_subsystem *subsys)
{
        subsys->iopolicy = iopolicy;
}

void nvme_mpath_unfreeze(struct nvme_subsystem *subsys)
{
        struct nvme_ns_head *h;

        lockdep_assert_held(&subsys->lock);
        list_for_each_entry(h, &subsys->nsheads, entry)
                if (h->disk)
                        blk_mq_unfreeze_queue_nomemrestore(h->disk->queue);
}

void nvme_mpath_wait_freeze(struct nvme_subsystem *subsys)
{
        struct nvme_ns_head *h;

        lockdep_assert_held(&subsys->lock);
        list_for_each_entry(h, &subsys->nsheads, entry)
                if (h->disk)
                        blk_mq_freeze_queue_wait(h->disk->queue);
}

void nvme_mpath_start_freeze(struct nvme_subsystem *subsys)
{
        struct nvme_ns_head *h;

        lockdep_assert_held(&subsys->lock);
        list_for_each_entry(h, &subsys->nsheads, entry)
                if (h->disk)
                        blk_freeze_queue_start(h->disk->queue);
}

void nvme_failover_req(struct request *req)
{
        struct nvme_ns *ns = req->q->queuedata;
        u16 status = nvme_req(req)->status & NVME_SCT_SC_MASK;
        unsigned long flags;
        struct bio *bio;

        nvme_mpath_clear_current_path(ns);

        /*
         * If we got back an ANA error, we know the controller is alive but not
         * ready to serve this namespace.  Kick of a re-read of the ANA
         * information page, and just try any other available path for now.
         */
        if (nvme_is_ana_error(status) && ns->ctrl->ana_log_buf) {
                set_bit(NVME_NS_ANA_PENDING, &ns->flags);
                queue_work(nvme_wq, &ns->ctrl->ana_work);
        }

        spin_lock_irqsave(&ns->head->requeue_lock, flags);
        for (bio = req->bio; bio; bio = bio->bi_next) {
                bio_set_dev(bio, ns->head->disk->part0);
                if (bio->bi_opf & REQ_POLLED) {
                        bio->bi_opf &= ~REQ_POLLED;
                        bio->bi_cookie = BLK_QC_T_NONE;
                }
                /*
                 * The alternate request queue that we may end up submitting
                 * the bio to may be frozen temporarily, in this case REQ_NOWAIT
                 * will fail the I/O immediately with EAGAIN to the issuer.
                 * We are not in the issuer context which cannot block. Clear
                 * the flag to avoid spurious EAGAIN I/O failures.
                 */
                bio->bi_opf &= ~REQ_NOWAIT;
        }
        blk_steal_bios(&ns->head->requeue_list, req);
        spin_unlock_irqrestore(&ns->head->requeue_lock, flags);

        nvme_req(req)->status = 0;
        nvme_end_req(req);
        kblockd_schedule_work(&ns->head->requeue_work);
}

void nvme_mpath_start_request(struct request *rq)
{
        struct nvme_ns *ns = rq->q->queuedata;
        struct gendisk *disk = ns->head->disk;

        if ((READ_ONCE(ns->head->subsys->iopolicy) == NVME_IOPOLICY_QD) &&
            !(nvme_req(rq)->flags & NVME_MPATH_CNT_ACTIVE)) {
                atomic_inc(&ns->ctrl->nr_active);
                nvme_req(rq)->flags |= NVME_MPATH_CNT_ACTIVE;
        }

        if (!blk_queue_io_stat(disk->queue) || blk_rq_is_passthrough(rq) ||
            (nvme_req(rq)->flags & NVME_MPATH_IO_STATS))
                return;

        nvme_req(rq)->flags |= NVME_MPATH_IO_STATS;
        nvme_req(rq)->start_time = bdev_start_io_acct(disk->part0, req_op(rq),
                                                      jiffies);
}
EXPORT_SYMBOL_GPL(nvme_mpath_start_request);

void nvme_mpath_end_request(struct request *rq)
{
        struct nvme_ns *ns = rq->q->queuedata;

        if (nvme_req(rq)->flags & NVME_MPATH_CNT_ACTIVE)
                atomic_dec_if_positive(&ns->ctrl->nr_active);

        if (!(nvme_req(rq)->flags & NVME_MPATH_IO_STATS))
                return;
        bdev_end_io_acct(ns->head->disk->part0, req_op(rq),
                         blk_rq_bytes(rq) >> SECTOR_SHIFT,
                         nvme_req(rq)->start_time);
}

void nvme_kick_requeue_lists(struct nvme_ctrl *ctrl)
{
        struct nvme_ns *ns;
        int srcu_idx;

        srcu_idx = srcu_read_lock(&ctrl->srcu);
        list_for_each_entry_srcu(ns, &ctrl->namespaces, list,
                                 srcu_read_lock_held(&ctrl->srcu)) {
                if (!ns->head->disk)
                        continue;
                kblockd_schedule_work(&ns->head->requeue_work);
                if (nvme_ctrl_state(ns->ctrl) == NVME_CTRL_LIVE)
                        disk_uevent(ns->head->disk, KOBJ_CHANGE);
        }
        srcu_read_unlock(&ctrl->srcu, srcu_idx);
}

static const char *nvme_ana_state_names[] = {
        [0]                             = "invalid state",
        [NVME_ANA_OPTIMIZED]            = "optimized",
        [NVME_ANA_NONOPTIMIZED]         = "non-optimized",
        [NVME_ANA_INACCESSIBLE]         = "inaccessible",
        [NVME_ANA_PERSISTENT_LOSS]      = "persistent-loss",
        [NVME_ANA_CHANGE]               = "change",
};

bool nvme_mpath_clear_current_path(struct nvme_ns *ns)
{
        struct nvme_ns_head *head = ns->head;
        bool changed = false;
        int node;

        if (!head)
                goto out;

        for_each_node(node) {
                if (ns == rcu_access_pointer(head->current_path[node])) {
                        rcu_assign_pointer(head->current_path[node], NULL);
                        changed = true;
                }
        }
out:
        return changed;
}

void nvme_mpath_clear_ctrl_paths(struct nvme_ctrl *ctrl)
{
        struct nvme_ns *ns;
        int srcu_idx;

        srcu_idx = srcu_read_lock(&ctrl->srcu);
        list_for_each_entry_srcu(ns, &ctrl->namespaces, list,
                                 srcu_read_lock_held(&ctrl->srcu)) {
                nvme_mpath_clear_current_path(ns);
                kblockd_schedule_work(&ns->head->requeue_work);
        }
        srcu_read_unlock(&ctrl->srcu, srcu_idx);
}

void nvme_mpath_revalidate_paths(struct nvme_ns *ns)
{
        struct nvme_ns_head *head = ns->head;
        sector_t capacity = get_capacity(head->disk);
        int node;
        int srcu_idx;

        srcu_idx = srcu_read_lock(&head->srcu);
        list_for_each_entry_srcu(ns, &head->list, siblings,
                                 srcu_read_lock_held(&head->srcu)) {
                if (capacity != get_capacity(ns->disk))
                        clear_bit(NVME_NS_READY, &ns->flags);
        }
        srcu_read_unlock(&head->srcu, srcu_idx);

        for_each_node(node)
                rcu_assign_pointer(head->current_path[node], NULL);
        kblockd_schedule_work(&head->requeue_work);
}

static bool nvme_path_is_disabled(struct nvme_ns *ns)
{
        enum nvme_ctrl_state state = nvme_ctrl_state(ns->ctrl);

        /*
         * We don't treat NVME_CTRL_DELETING as a disabled path as I/O should
         * still be able to complete assuming that the controller is connected.
         * Otherwise it will fail immediately and return to the requeue list.
         */
        if (state != NVME_CTRL_LIVE && state != NVME_CTRL_DELETING)
                return true;
        if (test_bit(NVME_NS_ANA_PENDING, &ns->flags) ||
            !test_bit(NVME_NS_READY, &ns->flags))
                return true;
        return false;
}

static struct nvme_ns *__nvme_find_path(struct nvme_ns_head *head, int node)
{
        int found_distance = INT_MAX, fallback_distance = INT_MAX, distance;
        struct nvme_ns *found = NULL, *fallback = NULL, *ns;

        list_for_each_entry_srcu(ns, &head->list, siblings,
                                 srcu_read_lock_held(&head->srcu)) {
                if (nvme_path_is_disabled(ns))
                        continue;

                if (ns->ctrl->numa_node != NUMA_NO_NODE &&
                    READ_ONCE(head->subsys->iopolicy) == NVME_IOPOLICY_NUMA)
                        distance = node_distance(node, ns->ctrl->numa_node);
                else
                        distance = LOCAL_DISTANCE;

                switch (ns->ana_state) {
                case NVME_ANA_OPTIMIZED:
                        if (distance < found_distance) {
                                found_distance = distance;
                                found = ns;
                        }
                        break;
                case NVME_ANA_NONOPTIMIZED:
                        if (distance < fallback_distance) {
                                fallback_distance = distance;
                                fallback = ns;
                        }
                        break;
                default:
                        break;
                }
        }

        if (!found)
                found = fallback;
        if (found)
                rcu_assign_pointer(head->current_path[node], found);
        return found;
}

static struct nvme_ns *nvme_next_ns(struct nvme_ns_head *head,
                struct nvme_ns *ns)
{
        ns = list_next_or_null_rcu(&head->list, &ns->siblings, struct nvme_ns,
                        siblings);
        if (ns)
                return ns;
        return list_first_or_null_rcu(&head->list, struct nvme_ns, siblings);
}

static struct nvme_ns *nvme_round_robin_path(struct nvme_ns_head *head)
{
        struct nvme_ns *ns, *found = NULL;
        int node = numa_node_id();
        struct nvme_ns *old = srcu_dereference(head->current_path[node],
                                               &head->srcu);

        if (unlikely(!old))
                return __nvme_find_path(head, node);

        if (list_is_singular(&head->list)) {
                if (nvme_path_is_disabled(old))
                        return NULL;
                return old;
        }

        for (ns = nvme_next_ns(head, old);
             ns && ns != old;
             ns = nvme_next_ns(head, ns)) {
                if (nvme_path_is_disabled(ns))
                        continue;

                if (ns->ana_state == NVME_ANA_OPTIMIZED) {
                        found = ns;
                        goto out;
                }
                if (ns->ana_state == NVME_ANA_NONOPTIMIZED)
                        found = ns;
        }

        /*
         * The loop above skips the current path for round-robin semantics.
         * Fall back to the current path if either:
         *  - no other optimized path found and current is optimized,
         *  - no other usable path found and current is usable.
         */
        if (!nvme_path_is_disabled(old) &&
            (old->ana_state == NVME_ANA_OPTIMIZED ||
             (!found && old->ana_state == NVME_ANA_NONOPTIMIZED)))
                return old;

        if (!found)
                return NULL;
out:
        rcu_assign_pointer(head->current_path[node], found);
        return found;
}

static struct nvme_ns *nvme_queue_depth_path(struct nvme_ns_head *head)
{
        struct nvme_ns *best_opt = NULL, *best_nonopt = NULL, *ns;
        unsigned int min_depth_opt = UINT_MAX, min_depth_nonopt = UINT_MAX;
        unsigned int depth;

        list_for_each_entry_srcu(ns, &head->list, siblings,
                                 srcu_read_lock_held(&head->srcu)) {
                if (nvme_path_is_disabled(ns))
                        continue;

                depth = atomic_read(&ns->ctrl->nr_active);

                switch (ns->ana_state) {
                case NVME_ANA_OPTIMIZED:
                        if (depth < min_depth_opt) {
                                min_depth_opt = depth;
                                best_opt = ns;
                        }
                        break;
                case NVME_ANA_NONOPTIMIZED:
                        if (depth < min_depth_nonopt) {
                                min_depth_nonopt = depth;
                                best_nonopt = ns;
                        }
                        break;
                default:
                        break;
                }

                if (min_depth_opt == 0)
                        return best_opt;
        }

        return best_opt ? best_opt : best_nonopt;
}

static inline bool nvme_path_is_optimized(struct nvme_ns *ns)
{
        return nvme_ctrl_state(ns->ctrl) == NVME_CTRL_LIVE &&
                ns->ana_state == NVME_ANA_OPTIMIZED;
}

static struct nvme_ns *nvme_numa_path(struct nvme_ns_head *head)
{
        int node = numa_node_id();
        struct nvme_ns *ns;

        ns = srcu_dereference(head->current_path[node], &head->srcu);
        if (unlikely(!ns))
                return __nvme_find_path(head, node);
        if (unlikely(!nvme_path_is_optimized(ns)))
                return __nvme_find_path(head, node);
        return ns;
}

inline struct nvme_ns *nvme_find_path(struct nvme_ns_head *head)
{
        switch (READ_ONCE(head->subsys->iopolicy)) {
        case NVME_IOPOLICY_QD:
                return nvme_queue_depth_path(head);
        case NVME_IOPOLICY_RR:
                return nvme_round_robin_path(head);
        default:
                return nvme_numa_path(head);
        }
}

static bool nvme_available_path(struct nvme_ns_head *head)
{
        struct nvme_ns *ns;

        if (!test_bit(NVME_NSHEAD_DISK_LIVE, &head->flags))
                return false;

        list_for_each_entry_srcu(ns, &head->list, siblings,
                                 srcu_read_lock_held(&head->srcu)) {
                if (test_bit(NVME_CTRL_FAILFAST_EXPIRED, &ns->ctrl->flags))
                        continue;
                switch (nvme_ctrl_state(ns->ctrl)) {
                case NVME_CTRL_LIVE:
                case NVME_CTRL_RESETTING:
                case NVME_CTRL_CONNECTING:
                        return true;
                default:
                        break;
                }
        }

        /*
         * If "head->delayed_removal_secs" is configured (i.e., non-zero), do
         * not immediately fail I/O. Instead, requeue the I/O for the configured
         * duration, anticipating that if there's a transient link failure then
         * it may recover within this time window. This parameter is exported to
         * userspace via sysfs, and its default value is zero. It is internally
         * mapped to NVME_NSHEAD_QUEUE_IF_NO_PATH. When delayed_removal_secs is
         * non-zero, this flag is set to true. When zero, the flag is cleared.
         */
        return nvme_mpath_queue_if_no_path(head);
}

static void nvme_ns_head_submit_bio(struct bio *bio)
{
        struct nvme_ns_head *head = bio->bi_bdev->bd_disk->private_data;
        struct device *dev = disk_to_dev(head->disk);
        struct nvme_ns *ns;
        int srcu_idx;

        /*
         * The namespace might be going away and the bio might be moved to a
         * different queue via blk_steal_bios(), so we need to use the bio_split
         * pool from the original queue to allocate the bvecs from.
         */
        bio = bio_split_to_limits(bio);
        if (!bio)
                return;

        srcu_idx = srcu_read_lock(&head->srcu);
        ns = nvme_find_path(head);
        if (likely(ns)) {
                bio_set_dev(bio, ns->disk->part0);
                bio->bi_opf |= REQ_NVME_MPATH;
                trace_block_bio_remap(bio, disk_devt(ns->head->disk),
                                      bio->bi_iter.bi_sector);
                submit_bio_noacct(bio);
        } else if (nvme_available_path(head)) {
                dev_warn_ratelimited(dev, "no usable path - requeuing I/O\n");

                spin_lock_irq(&head->requeue_lock);
                bio_list_add(&head->requeue_list, bio);
                spin_unlock_irq(&head->requeue_lock);
        } else {
                dev_warn_ratelimited(dev, "no available path - failing I/O\n");

                bio_io_error(bio);
        }

        srcu_read_unlock(&head->srcu, srcu_idx);
}

static int nvme_ns_head_open(struct gendisk *disk, blk_mode_t mode)
{
        if (!nvme_tryget_ns_head(disk->private_data))
                return -ENXIO;
        return 0;
}

static void nvme_ns_head_release(struct gendisk *disk)
{
        nvme_put_ns_head(disk->private_data);
}

static int nvme_ns_head_get_unique_id(struct gendisk *disk, u8 id[16],
                enum blk_unique_id type)
{
        struct nvme_ns_head *head = disk->private_data;
        struct nvme_ns *ns;
        int srcu_idx, ret = -EWOULDBLOCK;

        srcu_idx = srcu_read_lock(&head->srcu);
        ns = nvme_find_path(head);
        if (ns)
                ret = nvme_ns_get_unique_id(ns, id, type);
        srcu_read_unlock(&head->srcu, srcu_idx);
        return ret;
}

#ifdef CONFIG_BLK_DEV_ZONED
static int nvme_ns_head_report_zones(struct gendisk *disk, sector_t sector,
                unsigned int nr_zones, struct blk_report_zones_args *args)
{
        struct nvme_ns_head *head = disk->private_data;
        struct nvme_ns *ns;
        int srcu_idx, ret = -EWOULDBLOCK;

        srcu_idx = srcu_read_lock(&head->srcu);
        ns = nvme_find_path(head);
        if (ns)
                ret = nvme_ns_report_zones(ns, sector, nr_zones, args);
        srcu_read_unlock(&head->srcu, srcu_idx);
        return ret;
}
#else
#define nvme_ns_head_report_zones       NULL
#endif /* CONFIG_BLK_DEV_ZONED */

const struct block_device_operations nvme_ns_head_ops = {
        .owner          = THIS_MODULE,
        .submit_bio     = nvme_ns_head_submit_bio,
        .open           = nvme_ns_head_open,
        .release        = nvme_ns_head_release,
        .ioctl          = nvme_ns_head_ioctl,
        .compat_ioctl   = blkdev_compat_ptr_ioctl,
        .getgeo         = nvme_getgeo,
        .get_unique_id  = nvme_ns_head_get_unique_id,
        .report_zones   = nvme_ns_head_report_zones,
        .pr_ops         = &nvme_pr_ops,
};

static inline struct nvme_ns_head *cdev_to_ns_head(struct cdev *cdev)
{
        return container_of(cdev, struct nvme_ns_head, cdev);
}

static int nvme_ns_head_chr_open(struct inode *inode, struct file *file)
{
        if (!nvme_tryget_ns_head(cdev_to_ns_head(inode->i_cdev)))
                return -ENXIO;
        return 0;
}

static int nvme_ns_head_chr_release(struct inode *inode, struct file *file)
{
        nvme_put_ns_head(cdev_to_ns_head(inode->i_cdev));
        return 0;
}

static const struct file_operations nvme_ns_head_chr_fops = {
        .owner          = THIS_MODULE,
        .open           = nvme_ns_head_chr_open,
        .release        = nvme_ns_head_chr_release,
        .unlocked_ioctl = nvme_ns_head_chr_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
        .uring_cmd      = nvme_ns_head_chr_uring_cmd,
        .uring_cmd_iopoll = nvme_ns_chr_uring_cmd_iopoll,
};

static int nvme_add_ns_head_cdev(struct nvme_ns_head *head)
{
        int ret;

        head->cdev_device.parent = &head->subsys->dev;
        ret = dev_set_name(&head->cdev_device, "ng%dn%d",
                           head->subsys->instance, head->instance);
        if (ret)
                return ret;
        ret = nvme_cdev_add(&head->cdev, &head->cdev_device,
                            &nvme_ns_head_chr_fops, THIS_MODULE);
        return ret;
}

static void nvme_partition_scan_work(struct work_struct *work)
{
        struct nvme_ns_head *head =
                container_of(work, struct nvme_ns_head, partition_scan_work);

        if (WARN_ON_ONCE(!test_and_clear_bit(GD_SUPPRESS_PART_SCAN,
                                             &head->disk->state)))
                return;

        mutex_lock(&head->disk->open_mutex);
        bdev_disk_changed(head->disk, false);
        mutex_unlock(&head->disk->open_mutex);
}

static void nvme_requeue_work(struct work_struct *work)
{
        struct nvme_ns_head *head =
                container_of(work, struct nvme_ns_head, requeue_work);
        struct bio *bio, *next;

        spin_lock_irq(&head->requeue_lock);
        next = bio_list_get(&head->requeue_list);
        spin_unlock_irq(&head->requeue_lock);

        while ((bio = next) != NULL) {
                next = bio->bi_next;
                bio->bi_next = NULL;

                submit_bio_noacct(bio);
        }
}

static void nvme_remove_head(struct nvme_ns_head *head)
{
        if (test_and_clear_bit(NVME_NSHEAD_DISK_LIVE, &head->flags)) {
                /*
                 * requeue I/O after NVME_NSHEAD_DISK_LIVE has been cleared
                 * to allow multipath to fail all I/O.
                 */
                kblockd_schedule_work(&head->requeue_work);

                nvme_cdev_del(&head->cdev, &head->cdev_device);
                synchronize_srcu(&head->srcu);
                del_gendisk(head->disk);
        }
        nvme_put_ns_head(head);
}

static void nvme_remove_head_work(struct work_struct *work)
{
        struct nvme_ns_head *head = container_of(to_delayed_work(work),
                        struct nvme_ns_head, remove_work);
        bool remove = false;

        mutex_lock(&head->subsys->lock);
        if (list_empty(&head->list)) {
                list_del_init(&head->entry);
                remove = true;
        }
        mutex_unlock(&head->subsys->lock);
        if (remove)
                nvme_remove_head(head);

        module_put(THIS_MODULE);
}

int nvme_mpath_alloc_disk(struct nvme_ctrl *ctrl, struct nvme_ns_head *head)
{
        struct queue_limits lim;

        mutex_init(&head->lock);
        bio_list_init(&head->requeue_list);
        spin_lock_init(&head->requeue_lock);
        INIT_WORK(&head->requeue_work, nvme_requeue_work);
        INIT_WORK(&head->partition_scan_work, nvme_partition_scan_work);
        INIT_DELAYED_WORK(&head->remove_work, nvme_remove_head_work);
        head->delayed_removal_secs = 0;

        /*
         * If "multipath_always_on" is enabled, a multipath node is added
         * regardless of whether the disk is single/multi ported, and whether
         * the namespace is shared or private. If "multipath_always_on" is not
         * enabled, a multipath node is added only if the subsystem supports
         * multiple controllers and the "multipath" option is configured. In
         * either case, for private namespaces, we ensure that the NSID is
         * unique.
         */
        if (!multipath_always_on) {
                if (!(ctrl->subsys->cmic & NVME_CTRL_CMIC_MULTI_CTRL) ||
                                !multipath)
                        return 0;
        }

        if (!nvme_is_unique_nsid(ctrl, head))
                return 0;

        blk_set_stacking_limits(&lim);
        lim.dma_alignment = 3;
        lim.features |= BLK_FEAT_IO_STAT | BLK_FEAT_NOWAIT |
                BLK_FEAT_POLL | BLK_FEAT_ATOMIC_WRITES;
        if (head->ids.csi == NVME_CSI_ZNS)
                lim.features |= BLK_FEAT_ZONED;

        head->disk = blk_alloc_disk(&lim, ctrl->numa_node);
        if (IS_ERR(head->disk))
                return PTR_ERR(head->disk);
        head->disk->fops = &nvme_ns_head_ops;
        head->disk->private_data = head;

        /*
         * We need to suppress the partition scan from occuring within the
         * controller's scan_work context. If a path error occurs here, the IO
         * will wait until a path becomes available or all paths are torn down,
         * but that action also occurs within scan_work, so it would deadlock.
         * Defer the partition scan to a different context that does not block
         * scan_work.
         */
        set_bit(GD_SUPPRESS_PART_SCAN, &head->disk->state);
        sprintf(head->disk->disk_name, "nvme%dn%d",
                        ctrl->subsys->instance, head->instance);
        nvme_tryget_ns_head(head);
        return 0;
}

static void nvme_mpath_set_live(struct nvme_ns *ns)
{
        struct nvme_ns_head *head = ns->head;
        int rc;

        if (!head->disk)
                return;

        /*
         * test_and_set_bit() is used because it is protecting against two nvme
         * paths simultaneously calling device_add_disk() on the same namespace
         * head.
         */
        if (!test_and_set_bit(NVME_NSHEAD_DISK_LIVE, &head->flags)) {
                rc = device_add_disk(&head->subsys->dev, head->disk,
                                     nvme_ns_attr_groups);
                if (rc) {
                        clear_bit(NVME_NSHEAD_DISK_LIVE, &head->flags);
                        return;
                }
                nvme_add_ns_head_cdev(head);
                queue_work(nvme_wq, &head->partition_scan_work);
        }

        nvme_mpath_add_sysfs_link(ns->head);

        mutex_lock(&head->lock);
        if (nvme_path_is_optimized(ns)) {
                int node, srcu_idx;

                srcu_idx = srcu_read_lock(&head->srcu);
                for_each_online_node(node)
                        __nvme_find_path(head, node);
                srcu_read_unlock(&head->srcu, srcu_idx);
        }
        mutex_unlock(&head->lock);

        synchronize_srcu(&head->srcu);
        kblockd_schedule_work(&head->requeue_work);
}

static int nvme_parse_ana_log(struct nvme_ctrl *ctrl, void *data,
                int (*cb)(struct nvme_ctrl *ctrl, struct nvme_ana_group_desc *,
                        void *))
{
        void *base = ctrl->ana_log_buf;
        size_t offset = sizeof(struct nvme_ana_rsp_hdr);
        int error, i;

        lockdep_assert_held(&ctrl->ana_lock);

        for (i = 0; i < le16_to_cpu(ctrl->ana_log_buf->ngrps); i++) {
                struct nvme_ana_group_desc *desc = base + offset;
                u32 nr_nsids;
                size_t nsid_buf_size;

                if (WARN_ON_ONCE(offset > ctrl->ana_log_size - sizeof(*desc)))
                        return -EINVAL;

                nr_nsids = le32_to_cpu(desc->nnsids);
                nsid_buf_size = flex_array_size(desc, nsids, nr_nsids);

                if (WARN_ON_ONCE(desc->grpid == 0))
                        return -EINVAL;
                if (WARN_ON_ONCE(le32_to_cpu(desc->grpid) > ctrl->anagrpmax))
                        return -EINVAL;
                if (WARN_ON_ONCE(desc->state == 0))
                        return -EINVAL;
                if (WARN_ON_ONCE(desc->state > NVME_ANA_CHANGE))
                        return -EINVAL;

                offset += sizeof(*desc);
                if (WARN_ON_ONCE(offset > ctrl->ana_log_size - nsid_buf_size))
                        return -EINVAL;

                error = cb(ctrl, desc, data);
                if (error)
                        return error;

                offset += nsid_buf_size;
        }

        return 0;
}

static inline bool nvme_state_is_live(enum nvme_ana_state state)
{
        return state == NVME_ANA_OPTIMIZED || state == NVME_ANA_NONOPTIMIZED;
}

static void nvme_update_ns_ana_state(struct nvme_ana_group_desc *desc,
                struct nvme_ns *ns)
{
        ns->ana_grpid = le32_to_cpu(desc->grpid);
        ns->ana_state = desc->state;
        clear_bit(NVME_NS_ANA_PENDING, &ns->flags);
        /*
         * nvme_mpath_set_live() will trigger I/O to the multipath path device
         * and in turn to this path device.  However we cannot accept this I/O
         * if the controller is not live.  This may deadlock if called from
         * nvme_mpath_init_identify() and the ctrl will never complete
         * initialization, preventing I/O from completing.  For this case we
         * will reprocess the ANA log page in nvme_mpath_update() once the
         * controller is ready.
         */
        if (nvme_state_is_live(ns->ana_state) &&
            nvme_ctrl_state(ns->ctrl) == NVME_CTRL_LIVE)
                nvme_mpath_set_live(ns);
        else {
                /*
                 * Add sysfs link from multipath head gendisk node to path
                 * device gendisk node.
                 * If path's ana state is live (i.e. state is either optimized
                 * or non-optimized) while we alloc the ns then sysfs link would
                 * be created from nvme_mpath_set_live(). In that case we would
                 * not fallthrough this code path. However for the path's ana
                 * state other than live, we call nvme_mpath_set_live() only
                 * after ana state transitioned to the live state. But we still
                 * want to create the sysfs link from head node to a path device
                 * irrespctive of the path's ana state.
                 * If we reach through here then it means that path's ana state
                 * is not live but still create the sysfs link to this path from
                 * head node if head node of the path has already come alive.
                 */
                if (test_bit(NVME_NSHEAD_DISK_LIVE, &ns->head->flags))
                        nvme_mpath_add_sysfs_link(ns->head);
        }
}

static int nvme_update_ana_state(struct nvme_ctrl *ctrl,
                struct nvme_ana_group_desc *desc, void *data)
{
        u32 nr_nsids = le32_to_cpu(desc->nnsids), n = 0;
        unsigned *nr_change_groups = data;
        struct nvme_ns *ns;
        int srcu_idx;

        dev_dbg(ctrl->device, "ANA group %d: %s.\n",
                        le32_to_cpu(desc->grpid),
                        nvme_ana_state_names[desc->state]);

        if (desc->state == NVME_ANA_CHANGE)
                (*nr_change_groups)++;

        if (!nr_nsids)
                return 0;

        srcu_idx = srcu_read_lock(&ctrl->srcu);
        list_for_each_entry_srcu(ns, &ctrl->namespaces, list,
                                 srcu_read_lock_held(&ctrl->srcu)) {
                unsigned nsid;
again:
                nsid = le32_to_cpu(desc->nsids[n]);
                if (ns->head->ns_id < nsid)
                        continue;
                if (ns->head->ns_id == nsid)
                        nvme_update_ns_ana_state(desc, ns);
                if (++n == nr_nsids)
                        break;
                if (ns->head->ns_id > nsid)
                        goto again;
        }
        srcu_read_unlock(&ctrl->srcu, srcu_idx);
        return 0;
}

static int nvme_read_ana_log(struct nvme_ctrl *ctrl)
{
        u32 nr_change_groups = 0;
        int error;

        mutex_lock(&ctrl->ana_lock);
        error = nvme_get_log(ctrl, NVME_NSID_ALL, NVME_LOG_ANA, 0, NVME_CSI_NVM,
                        ctrl->ana_log_buf, ctrl->ana_log_size, 0);
        if (error) {
                dev_warn(ctrl->device, "Failed to get ANA log: %d\n", error);
                goto out_unlock;
        }

        error = nvme_parse_ana_log(ctrl, &nr_change_groups,
                        nvme_update_ana_state);
        if (error)
                goto out_unlock;

        /*
         * In theory we should have an ANATT timer per group as they might enter
         * the change state at different times.  But that is a lot of overhead
         * just to protect against a target that keeps entering new changes
         * states while never finishing previous ones.  But we'll still
         * eventually time out once all groups are in change state, so this
         * isn't a big deal.
         *
         * We also double the ANATT value to provide some slack for transports
         * or AEN processing overhead.
         */
        if (nr_change_groups)
                mod_timer(&ctrl->anatt_timer, ctrl->anatt * HZ * 2 + jiffies);
        else
                timer_delete_sync(&ctrl->anatt_timer);
out_unlock:
        mutex_unlock(&ctrl->ana_lock);
        return error;
}

static void nvme_ana_work(struct work_struct *work)
{
        struct nvme_ctrl *ctrl = container_of(work, struct nvme_ctrl, ana_work);

        if (nvme_ctrl_state(ctrl) != NVME_CTRL_LIVE)
                return;

        nvme_read_ana_log(ctrl);
}

void nvme_mpath_update(struct nvme_ctrl *ctrl)
{
        u32 nr_change_groups = 0;

        if (!ctrl->ana_log_buf)
                return;

        mutex_lock(&ctrl->ana_lock);
        nvme_parse_ana_log(ctrl, &nr_change_groups, nvme_update_ana_state);
        mutex_unlock(&ctrl->ana_lock);
}

static void nvme_anatt_timeout(struct timer_list *t)
{
        struct nvme_ctrl *ctrl = timer_container_of(ctrl, t, anatt_timer);

        dev_info(ctrl->device, "ANATT timeout, resetting controller.\n");
        nvme_reset_ctrl(ctrl);
}

void nvme_mpath_stop(struct nvme_ctrl *ctrl)
{
        if (!nvme_ctrl_use_ana(ctrl))
                return;
        timer_delete_sync(&ctrl->anatt_timer);
        cancel_work_sync(&ctrl->ana_work);
}

#define SUBSYS_ATTR_RW(_name, _mode, _show, _store)  \
        struct device_attribute subsys_attr_##_name =   \
                __ATTR(_name, _mode, _show, _store)

static ssize_t nvme_subsys_iopolicy_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct nvme_subsystem *subsys =
                container_of(dev, struct nvme_subsystem, dev);

        return sysfs_emit(buf, "%s\n",
                          nvme_iopolicy_names[READ_ONCE(subsys->iopolicy)]);
}

static void nvme_subsys_iopolicy_update(struct nvme_subsystem *subsys,
                int iopolicy)
{
        struct nvme_ctrl *ctrl;
        int old_iopolicy = READ_ONCE(subsys->iopolicy);

        if (old_iopolicy == iopolicy)
                return;

        WRITE_ONCE(subsys->iopolicy, iopolicy);

        /* iopolicy changes clear the mpath by design */
        mutex_lock(&nvme_subsystems_lock);
        list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry)
                nvme_mpath_clear_ctrl_paths(ctrl);
        mutex_unlock(&nvme_subsystems_lock);

        pr_notice("subsysnqn %s iopolicy changed from %s to %s\n",
                        subsys->subnqn,
                        nvme_iopolicy_names[old_iopolicy],
                        nvme_iopolicy_names[iopolicy]);
}

static ssize_t nvme_subsys_iopolicy_store(struct device *dev,
                struct device_attribute *attr, const char *buf, size_t count)
{
        struct nvme_subsystem *subsys =
                container_of(dev, struct nvme_subsystem, dev);
        int i;

        for (i = 0; i < ARRAY_SIZE(nvme_iopolicy_names); i++) {
                if (sysfs_streq(buf, nvme_iopolicy_names[i])) {
                        nvme_subsys_iopolicy_update(subsys, i);
                        return count;
                }
        }

        return -EINVAL;
}
SUBSYS_ATTR_RW(iopolicy, S_IRUGO | S_IWUSR,
                      nvme_subsys_iopolicy_show, nvme_subsys_iopolicy_store);

static ssize_t ana_grpid_show(struct device *dev, struct device_attribute *attr,
                char *buf)
{
        return sysfs_emit(buf, "%d\n", nvme_get_ns_from_dev(dev)->ana_grpid);
}
DEVICE_ATTR_RO(ana_grpid);

static ssize_t ana_state_show(struct device *dev, struct device_attribute *attr,
                char *buf)
{
        struct nvme_ns *ns = nvme_get_ns_from_dev(dev);

        return sysfs_emit(buf, "%s\n", nvme_ana_state_names[ns->ana_state]);
}
DEVICE_ATTR_RO(ana_state);

static ssize_t queue_depth_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct nvme_ns *ns = nvme_get_ns_from_dev(dev);

        if (ns->head->subsys->iopolicy != NVME_IOPOLICY_QD)
                return 0;

        return sysfs_emit(buf, "%d\n", atomic_read(&ns->ctrl->nr_active));
}
DEVICE_ATTR_RO(queue_depth);

static ssize_t numa_nodes_show(struct device *dev, struct device_attribute *attr,
                char *buf)
{
        int node, srcu_idx;
        nodemask_t numa_nodes;
        struct nvme_ns *current_ns;
        struct nvme_ns *ns = nvme_get_ns_from_dev(dev);
        struct nvme_ns_head *head = ns->head;

        if (head->subsys->iopolicy != NVME_IOPOLICY_NUMA)
                return 0;

        nodes_clear(numa_nodes);

        srcu_idx = srcu_read_lock(&head->srcu);
        for_each_node(node) {
                current_ns = srcu_dereference(head->current_path[node],
                                &head->srcu);
                if (ns == current_ns)
                        node_set(node, numa_nodes);
        }
        srcu_read_unlock(&head->srcu, srcu_idx);

        return sysfs_emit(buf, "%*pbl\n", nodemask_pr_args(&numa_nodes));
}
DEVICE_ATTR_RO(numa_nodes);

static ssize_t delayed_removal_secs_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct gendisk *disk = dev_to_disk(dev);
        struct nvme_ns_head *head = disk->private_data;
        int ret;

        mutex_lock(&head->subsys->lock);
        ret = sysfs_emit(buf, "%u\n", head->delayed_removal_secs);
        mutex_unlock(&head->subsys->lock);
        return ret;
}

static ssize_t delayed_removal_secs_store(struct device *dev,
                struct device_attribute *attr, const char *buf, size_t count)
{
        struct gendisk *disk = dev_to_disk(dev);
        struct nvme_ns_head *head = disk->private_data;
        unsigned int sec;
        int ret;

        ret = kstrtouint(buf, 0, &sec);
        if (ret < 0)
                return ret;

        mutex_lock(&head->subsys->lock);
        head->delayed_removal_secs = sec;
        if (sec)
                set_bit(NVME_NSHEAD_QUEUE_IF_NO_PATH, &head->flags);
        else
                clear_bit(NVME_NSHEAD_QUEUE_IF_NO_PATH, &head->flags);
        mutex_unlock(&head->subsys->lock);
        /*
         * Ensure that update to NVME_NSHEAD_QUEUE_IF_NO_PATH is seen
         * by its reader.
         */
        synchronize_srcu(&head->srcu);

        return count;
}

DEVICE_ATTR_RW(delayed_removal_secs);

static int nvme_lookup_ana_group_desc(struct nvme_ctrl *ctrl,
                struct nvme_ana_group_desc *desc, void *data)
{
        struct nvme_ana_group_desc *dst = data;

        if (desc->grpid != dst->grpid)
                return 0;

        *dst = *desc;
        return -ENXIO; /* just break out of the loop */
}

void nvme_mpath_add_sysfs_link(struct nvme_ns_head *head)
{
        struct device *target;
        int rc, srcu_idx;
        struct nvme_ns *ns;
        struct kobject *kobj;

        /*
         * Ensure head disk node is already added otherwise we may get invalid
         * kobj for head disk node
         */
        if (!test_bit(GD_ADDED, &head->disk->state))
                return;

        kobj = &disk_to_dev(head->disk)->kobj;

        /*
         * loop through each ns chained through the head->list and create the
         * sysfs link from head node to the ns path node
         */
        srcu_idx = srcu_read_lock(&head->srcu);

        list_for_each_entry_srcu(ns, &head->list, siblings,
                                 srcu_read_lock_held(&head->srcu)) {
                /*
                 * Ensure that ns path disk node is already added otherwise we
                 * may get invalid kobj name for target
                 */
                if (!test_bit(GD_ADDED, &ns->disk->state))
                        continue;

                /*
                 * Avoid creating link if it already exists for the given path.
                 * When path ana state transitions from optimized to non-
                 * optimized or vice-versa, the nvme_mpath_set_live() is
                 * invoked which in truns call this function. Now if the sysfs
                 * link already exists for the given path and we attempt to re-
                 * create the link then sysfs code would warn about it loudly.
                 * So we evaluate NVME_NS_SYSFS_ATTR_LINK flag here to ensure
                 * that we're not creating duplicate link.
                 * The test_and_set_bit() is used because it is protecting
                 * against multiple nvme paths being simultaneously added.
                 */
                if (test_and_set_bit(NVME_NS_SYSFS_ATTR_LINK, &ns->flags))
                        continue;

                target = disk_to_dev(ns->disk);
                /*
                 * Create sysfs link from head gendisk kobject @kobj to the
                 * ns path gendisk kobject @target->kobj.
                 */
                rc = sysfs_add_link_to_group(kobj, nvme_ns_mpath_attr_group.name,
                                &target->kobj, dev_name(target));
                if (unlikely(rc)) {
                        dev_err(disk_to_dev(ns->head->disk),
                                        "failed to create link to %s\n",
                                        dev_name(target));
                        clear_bit(NVME_NS_SYSFS_ATTR_LINK, &ns->flags);
                }
        }

        srcu_read_unlock(&head->srcu, srcu_idx);
}

void nvme_mpath_remove_sysfs_link(struct nvme_ns *ns)
{
        struct device *target;
        struct kobject *kobj;

        if (!test_bit(NVME_NS_SYSFS_ATTR_LINK, &ns->flags))
                return;

        target = disk_to_dev(ns->disk);
        kobj = &disk_to_dev(ns->head->disk)->kobj;
        sysfs_remove_link_from_group(kobj, nvme_ns_mpath_attr_group.name,
                        dev_name(target));
        clear_bit(NVME_NS_SYSFS_ATTR_LINK, &ns->flags);
}

void nvme_mpath_add_disk(struct nvme_ns *ns, __le32 anagrpid)
{
        if (nvme_ctrl_use_ana(ns->ctrl)) {
                struct nvme_ana_group_desc desc = {
                        .grpid = anagrpid,
                        .state = 0,
                };

                mutex_lock(&ns->ctrl->ana_lock);
                ns->ana_grpid = le32_to_cpu(anagrpid);
                nvme_parse_ana_log(ns->ctrl, &desc, nvme_lookup_ana_group_desc);
                mutex_unlock(&ns->ctrl->ana_lock);
                if (desc.state) {
                        /* found the group desc: update */
                        nvme_update_ns_ana_state(&desc, ns);
                } else {
                        /* group desc not found: trigger a re-read */
                        set_bit(NVME_NS_ANA_PENDING, &ns->flags);
                        queue_work(nvme_wq, &ns->ctrl->ana_work);
                }
        } else {
                ns->ana_state = NVME_ANA_OPTIMIZED;
                nvme_mpath_set_live(ns);
        }

#ifdef CONFIG_BLK_DEV_ZONED
        if (blk_queue_is_zoned(ns->queue) && ns->head->disk)
                ns->head->disk->nr_zones = ns->disk->nr_zones;
#endif
}

void nvme_mpath_remove_disk(struct nvme_ns_head *head)
{
        bool remove = false;

        if (!head->disk)
                return;

        mutex_lock(&head->subsys->lock);
        /*
         * We are called when all paths have been removed, and at that point
         * head->list is expected to be empty. However, nvme_ns_remove() and
         * nvme_init_ns_head() can run concurrently and so if head->delayed_
         * removal_secs is configured, it is possible that by the time we reach
         * this point, head->list may no longer be empty. Therefore, we recheck
         * head->list here. If it is no longer empty then we skip enqueuing the
         * delayed head removal work.
         */
        if (!list_empty(&head->list))
                goto out;

        /*
         * Ensure that no one could remove this module while the head
         * remove work is pending.
         */
        if (head->delayed_removal_secs && try_module_get(THIS_MODULE)) {
                mod_delayed_work(nvme_wq, &head->remove_work,
                                head->delayed_removal_secs * HZ);
        } else {
                list_del_init(&head->entry);
                remove = true;
        }
out:
        mutex_unlock(&head->subsys->lock);
        if (remove)
                nvme_remove_head(head);
}

void nvme_mpath_put_disk(struct nvme_ns_head *head)
{
        if (!head->disk)
                return;
        /* make sure all pending bios are cleaned up */
        kblockd_schedule_work(&head->requeue_work);
        flush_work(&head->requeue_work);
        flush_work(&head->partition_scan_work);
        put_disk(head->disk);
}

void nvme_mpath_init_ctrl(struct nvme_ctrl *ctrl)
{
        mutex_init(&ctrl->ana_lock);
        timer_setup(&ctrl->anatt_timer, nvme_anatt_timeout, 0);
        INIT_WORK(&ctrl->ana_work, nvme_ana_work);
}

int nvme_mpath_init_identify(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id)
{
        size_t max_transfer_size = ctrl->max_hw_sectors << SECTOR_SHIFT;
        size_t ana_log_size;
        int error = 0;

        /* check if multipath is enabled and we have the capability */
        if (!multipath || !ctrl->subsys ||
            !(ctrl->subsys->cmic & NVME_CTRL_CMIC_ANA))
                return 0;

        /* initialize this in the identify path to cover controller resets */
        atomic_set(&ctrl->nr_active, 0);

        if (!ctrl->max_namespaces ||
            ctrl->max_namespaces > le32_to_cpu(id->nn)) {
                dev_err(ctrl->device,
                        "Invalid MNAN value %u\n", ctrl->max_namespaces);
                return -EINVAL;
        }

        ctrl->anacap = id->anacap;
        ctrl->anatt = id->anatt;
        ctrl->nanagrpid = le32_to_cpu(id->nanagrpid);
        ctrl->anagrpmax = le32_to_cpu(id->anagrpmax);

        ana_log_size = sizeof(struct nvme_ana_rsp_hdr) +
                ctrl->nanagrpid * sizeof(struct nvme_ana_group_desc) +
                ctrl->max_namespaces * sizeof(__le32);
        if (ana_log_size > max_transfer_size) {
                dev_err(ctrl->device,
                        "ANA log page size (%zd) larger than MDTS (%zd).\n",
                        ana_log_size, max_transfer_size);
                dev_err(ctrl->device, "disabling ANA support.\n");
                goto out_uninit;
        }
        if (ana_log_size > ctrl->ana_log_size) {
                nvme_mpath_stop(ctrl);
                nvme_mpath_uninit(ctrl);
                ctrl->ana_log_buf = kvmalloc(ana_log_size, GFP_KERNEL);
                if (!ctrl->ana_log_buf)
                        return -ENOMEM;
        }
        ctrl->ana_log_size = ana_log_size;
        error = nvme_read_ana_log(ctrl);
        if (error)
                goto out_uninit;
        return 0;

out_uninit:
        nvme_mpath_uninit(ctrl);
        return error;
}

void nvme_mpath_uninit(struct nvme_ctrl *ctrl)
{
        kvfree(ctrl->ana_log_buf);
        ctrl->ana_log_buf = NULL;
        ctrl->ana_log_size = 0;
}