// SPDX-License-Identifier: GPL-2.0
/*
 * Shared application/kernel submission and completion ring pairs, for
 * supporting fast/efficient IO.
 *
 * A note on the read/write ordering memory barriers that are matched between
 * the application and kernel side.
 *
 * After the application reads the CQ ring tail, it must use an
 * appropriate smp_rmb() to pair with the smp_wmb() the kernel uses
 * before writing the tail (using smp_load_acquire to read the tail will
 * do). It also needs a smp_mb() before updating CQ head (ordering the
 * entry load(s) with the head store), pairing with an implicit barrier
 * through a control-dependency in io_get_cqe (smp_store_release to
 * store head will do). Failure to do so could lead to reading invalid
 * CQ entries.
 *
 * Likewise, the application must use an appropriate smp_wmb() before
 * writing the SQ tail (ordering SQ entry stores with the tail store),
 * which pairs with smp_load_acquire in io_get_sqring (smp_store_release
 * to store the tail will do). And it needs a barrier ordering the SQ
 * head load before writing new SQ entries (smp_load_acquire to read
 * head will do).
 *
 * When using the SQ poll thread (IORING_SETUP_SQPOLL), the application
 * needs to check the SQ flags for IORING_SQ_NEED_WAKEUP *after*
 * updating the SQ tail; a full memory barrier smp_mb() is needed
 * between.
 *
 * Also see the examples in the liburing library:
 *
 *      git://git.kernel.org/pub/scm/linux/kernel/git/axboe/liburing.git
 *
 * io_uring also uses READ/WRITE_ONCE() for _any_ store or load that happens
 * from data shared between the kernel and application. This is done both
 * for ordering purposes, but also to ensure that once a value is loaded from
 * data that the application could potentially modify, it remains stable.
 *
 * Copyright (C) 2018-2019 Jens Axboe
 * Copyright (c) 2018-2019 Christoph Hellwig
 */
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/syscalls.h>
#include <linux/refcount.h>
#include <linux/bits.h>

#include <linux/sched/signal.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/percpu.h>
#include <linux/slab.h>
#include <linux/anon_inodes.h>
#include <linux/uaccess.h>
#include <linux/nospec.h>
#include <linux/task_work.h>
#include <linux/io_uring.h>
#include <linux/io_uring/cmd.h>
#include <linux/audit.h>
#include <linux/security.h>
#include <linux/jump_label.h>

#define CREATE_TRACE_POINTS
#include <trace/events/io_uring.h>

#include <uapi/linux/io_uring.h>

#include "io-wq.h"

#include "filetable.h"
#include "io_uring.h"
#include "opdef.h"
#include "refs.h"
#include "tctx.h"
#include "register.h"
#include "sqpoll.h"
#include "fdinfo.h"
#include "kbuf.h"
#include "rsrc.h"
#include "cancel.h"
#include "net.h"
#include "notif.h"
#include "waitid.h"
#include "futex.h"
#include "napi.h"
#include "uring_cmd.h"
#include "msg_ring.h"
#include "memmap.h"
#include "zcrx.h"

#include "timeout.h"
#include "poll.h"
#include "rw.h"
#include "alloc_cache.h"
#include "eventfd.h"
#include "wait.h"
#include "bpf_filter.h"

#define SQE_COMMON_FLAGS (IOSQE_FIXED_FILE | IOSQE_IO_LINK | \
                          IOSQE_IO_HARDLINK | IOSQE_ASYNC)

#define IO_REQ_LINK_FLAGS (REQ_F_LINK | REQ_F_HARDLINK)

#define IO_REQ_CLEAN_FLAGS (REQ_F_BUFFER_SELECTED | REQ_F_NEED_CLEANUP | \
                                REQ_F_INFLIGHT | REQ_F_CREDS | REQ_F_ASYNC_DATA)

#define IO_REQ_CLEAN_SLOW_FLAGS (REQ_F_REFCOUNT | IO_REQ_LINK_FLAGS | \
                                 REQ_F_REISSUE | REQ_F_POLLED | \
                                 IO_REQ_CLEAN_FLAGS)

#define IO_TCTX_REFS_CACHE_NR   (1U << 10)

#define IO_COMPL_BATCH                  32
#define IO_REQ_ALLOC_BATCH              8

/* requests with any of those set should undergo io_disarm_next() */
#define IO_DISARM_MASK (REQ_F_ARM_LTIMEOUT | REQ_F_LINK_TIMEOUT | REQ_F_FAIL)

static void io_queue_sqe(struct io_kiocb *req, unsigned int extra_flags);
static void __io_req_caches_free(struct io_ring_ctx *ctx);

static __read_mostly DEFINE_STATIC_KEY_DEFERRED_FALSE(io_key_has_sqarray, HZ);

struct kmem_cache *req_cachep;
static struct workqueue_struct *iou_wq __ro_after_init;

static int __read_mostly sysctl_io_uring_disabled;
static int __read_mostly sysctl_io_uring_group = -1;

#ifdef CONFIG_SYSCTL
static const struct ctl_table kernel_io_uring_disabled_table[] = {
        {
                .procname       = "io_uring_disabled",
                .data           = &sysctl_io_uring_disabled,
                .maxlen         = sizeof(sysctl_io_uring_disabled),
                .mode           = 0644,
                .proc_handler   = proc_dointvec_minmax,
                .extra1         = SYSCTL_ZERO,
                .extra2         = SYSCTL_TWO,
        },
        {
                .procname       = "io_uring_group",
                .data           = &sysctl_io_uring_group,
                .maxlen         = sizeof(gid_t),
                .mode           = 0644,
                .proc_handler   = proc_dointvec,
        },
};
#endif

static void io_poison_cached_req(struct io_kiocb *req)
{
        req->ctx = IO_URING_PTR_POISON;
        req->tctx = IO_URING_PTR_POISON;
        req->file = IO_URING_PTR_POISON;
        req->creds = IO_URING_PTR_POISON;
        req->io_task_work.func = IO_URING_PTR_POISON;
        req->apoll = IO_URING_PTR_POISON;
}

static void io_poison_req(struct io_kiocb *req)
{
        io_poison_cached_req(req);
        req->async_data = IO_URING_PTR_POISON;
        req->kbuf = IO_URING_PTR_POISON;
        req->comp_list.next = IO_URING_PTR_POISON;
        req->file_node = IO_URING_PTR_POISON;
        req->link = IO_URING_PTR_POISON;
}

static inline void req_fail_link_node(struct io_kiocb *req, int res)
{
        req_set_fail(req);
        io_req_set_res(req, res, 0);
}

static inline void io_req_add_to_cache(struct io_kiocb *req, struct io_ring_ctx *ctx)
{
        if (IS_ENABLED(CONFIG_KASAN))
                io_poison_cached_req(req);
        wq_stack_add_head(&req->comp_list, &ctx->submit_state.free_list);
}

static __cold void io_ring_ctx_ref_free(struct percpu_ref *ref)
{
        struct io_ring_ctx *ctx = container_of(ref, struct io_ring_ctx, refs);

        complete(&ctx->ref_comp);
}

static int io_alloc_hash_table(struct io_hash_table *table, unsigned bits)
{
        unsigned int hash_buckets;
        int i;

        do {
                hash_buckets = 1U << bits;
                table->hbs = kvmalloc_objs(table->hbs[0], hash_buckets,
                                           GFP_KERNEL_ACCOUNT);
                if (table->hbs)
                        break;
                if (bits == 1)
                        return -ENOMEM;
                bits--;
        } while (1);

        table->hash_bits = bits;
        for (i = 0; i < hash_buckets; i++)
                INIT_HLIST_HEAD(&table->hbs[i].list);
        return 0;
}

static void io_free_alloc_caches(struct io_ring_ctx *ctx)
{
        io_alloc_cache_free(&ctx->apoll_cache, kfree);
        io_alloc_cache_free(&ctx->netmsg_cache, io_netmsg_cache_free);
        io_alloc_cache_free(&ctx->rw_cache, io_rw_cache_free);
        io_alloc_cache_free(&ctx->cmd_cache, io_cmd_cache_free);
        io_futex_cache_free(ctx);
        io_rsrc_cache_free(ctx);
}

static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
{
        struct io_ring_ctx *ctx;
        int hash_bits;
        bool ret;

        ctx = kzalloc_obj(*ctx);
        if (!ctx)
                return NULL;

        xa_init(&ctx->io_bl_xa);

        /*
         * Use 5 bits less than the max cq entries, that should give us around
         * 32 entries per hash list if totally full and uniformly spread, but
         * don't keep too many buckets to not overconsume memory.
         */
        hash_bits = ilog2(p->cq_entries) - 5;
        hash_bits = clamp(hash_bits, 1, 8);
        if (io_alloc_hash_table(&ctx->cancel_table, hash_bits))
                goto err;
        if (percpu_ref_init(&ctx->refs, io_ring_ctx_ref_free,
                            0, GFP_KERNEL))
                goto err;

        ctx->flags = p->flags;
        ctx->hybrid_poll_time = LLONG_MAX;
        atomic_set(&ctx->cq_wait_nr, IO_CQ_WAKE_INIT);
        init_waitqueue_head(&ctx->sqo_sq_wait);
        INIT_LIST_HEAD(&ctx->sqd_list);
        INIT_LIST_HEAD(&ctx->cq_overflow_list);
        ret = io_alloc_cache_init(&ctx->apoll_cache, IO_POLL_ALLOC_CACHE_MAX,
                            sizeof(struct async_poll), 0);
        ret |= io_alloc_cache_init(&ctx->netmsg_cache, IO_ALLOC_CACHE_MAX,
                            sizeof(struct io_async_msghdr),
                            offsetof(struct io_async_msghdr, clear));
        ret |= io_alloc_cache_init(&ctx->rw_cache, IO_ALLOC_CACHE_MAX,
                            sizeof(struct io_async_rw),
                            offsetof(struct io_async_rw, clear));
        ret |= io_alloc_cache_init(&ctx->cmd_cache, IO_ALLOC_CACHE_MAX,
                            sizeof(struct io_async_cmd),
                            sizeof(struct io_async_cmd));
        ret |= io_futex_cache_init(ctx);
        ret |= io_rsrc_cache_init(ctx);
        if (ret)
                goto free_ref;
        init_completion(&ctx->ref_comp);
        xa_init_flags(&ctx->personalities, XA_FLAGS_ALLOC1);
        mutex_init(&ctx->uring_lock);
        init_waitqueue_head(&ctx->cq_wait);
        init_waitqueue_head(&ctx->poll_wq);
        spin_lock_init(&ctx->completion_lock);
        raw_spin_lock_init(&ctx->timeout_lock);
        INIT_LIST_HEAD(&ctx->iopoll_list);
        INIT_LIST_HEAD(&ctx->defer_list);
        INIT_LIST_HEAD(&ctx->timeout_list);
        INIT_LIST_HEAD(&ctx->ltimeout_list);
        init_llist_head(&ctx->work_llist);
        INIT_LIST_HEAD(&ctx->tctx_list);
        mutex_init(&ctx->tctx_lock);
        ctx->submit_state.free_list.next = NULL;
        INIT_HLIST_HEAD(&ctx->waitid_list);
        xa_init_flags(&ctx->zcrx_ctxs, XA_FLAGS_ALLOC);
#ifdef CONFIG_FUTEX
        INIT_HLIST_HEAD(&ctx->futex_list);
#endif
        INIT_DELAYED_WORK(&ctx->fallback_work, io_fallback_req_func);
        INIT_WQ_LIST(&ctx->submit_state.compl_reqs);
        INIT_HLIST_HEAD(&ctx->cancelable_uring_cmd);
        io_napi_init(ctx);
        mutex_init(&ctx->mmap_lock);

        return ctx;

free_ref:
        percpu_ref_exit(&ctx->refs);
err:
        io_free_alloc_caches(ctx);
        kvfree(ctx->cancel_table.hbs);
        xa_destroy(&ctx->io_bl_xa);
        kfree(ctx);
        return NULL;
}

static void io_clean_op(struct io_kiocb *req)
{
        if (unlikely(req->flags & REQ_F_BUFFER_SELECTED))
                io_kbuf_drop_legacy(req);

        if (req->flags & REQ_F_NEED_CLEANUP) {
                const struct io_cold_def *def = &io_cold_defs[req->opcode];

                if (def->cleanup)
                        def->cleanup(req);
        }
        if (req->flags & REQ_F_INFLIGHT)
                atomic_dec(&req->tctx->inflight_tracked);
        if (req->flags & REQ_F_CREDS)
                put_cred(req->creds);
        if (req->flags & REQ_F_ASYNC_DATA) {
                kfree(req->async_data);
                req->async_data = NULL;
        }
        req->flags &= ~IO_REQ_CLEAN_FLAGS;
}

/*
 * Mark the request as inflight, so that file cancelation will find it.
 * Can be used if the file is an io_uring instance, or if the request itself
 * relies on ->mm being alive for the duration of the request.
 */
inline void io_req_track_inflight(struct io_kiocb *req)
{
        if (!(req->flags & REQ_F_INFLIGHT)) {
                req->flags |= REQ_F_INFLIGHT;
                atomic_inc(&req->tctx->inflight_tracked);
        }
}

static struct io_kiocb *__io_prep_linked_timeout(struct io_kiocb *req)
{
        if (WARN_ON_ONCE(!req->link))
                return NULL;

        req->flags &= ~REQ_F_ARM_LTIMEOUT;
        req->flags |= REQ_F_LINK_TIMEOUT;

        /* linked timeouts should have two refs once prep'ed */
        io_req_set_refcount(req);
        __io_req_set_refcount(req->link, 2);
        return req->link;
}

static void io_prep_async_work(struct io_kiocb *req)
{
        const struct io_issue_def *def = &io_issue_defs[req->opcode];
        struct io_ring_ctx *ctx = req->ctx;

        if (!(req->flags & REQ_F_CREDS)) {
                req->flags |= REQ_F_CREDS;
                req->creds = get_current_cred();
        }

        req->work.list.next = NULL;
        atomic_set(&req->work.flags, 0);
        if (req->flags & REQ_F_FORCE_ASYNC)
                atomic_or(IO_WQ_WORK_CONCURRENT, &req->work.flags);

        if (req->file && !(req->flags & REQ_F_FIXED_FILE))
                req->flags |= io_file_get_flags(req->file);

        if (req->file && (req->flags & REQ_F_ISREG)) {
                bool should_hash = def->hash_reg_file;

                /* don't serialize this request if the fs doesn't need it */
                if (should_hash && (req->file->f_flags & O_DIRECT) &&
                    (req->file->f_op->fop_flags & FOP_DIO_PARALLEL_WRITE))
                        should_hash = false;
                if (should_hash || (ctx->flags & IORING_SETUP_IOPOLL))
                        io_wq_hash_work(&req->work, file_inode(req->file));
        } else if (!req->file || !S_ISBLK(file_inode(req->file)->i_mode)) {
                if (def->unbound_nonreg_file)
                        atomic_or(IO_WQ_WORK_UNBOUND, &req->work.flags);
        }
}

static void io_prep_async_link(struct io_kiocb *req)
{
        struct io_kiocb *cur;

        if (req->flags & REQ_F_LINK_TIMEOUT) {
                struct io_ring_ctx *ctx = req->ctx;

                raw_spin_lock_irq(&ctx->timeout_lock);
                io_for_each_link(cur, req)
                        io_prep_async_work(cur);
                raw_spin_unlock_irq(&ctx->timeout_lock);
        } else {
                io_for_each_link(cur, req)
                        io_prep_async_work(cur);
        }
}

static void io_queue_iowq(struct io_kiocb *req)
{
        struct io_uring_task *tctx = req->tctx;

        BUG_ON(!tctx);

        if ((current->flags & PF_KTHREAD) || !tctx->io_wq) {
                io_req_task_queue_fail(req, -ECANCELED);
                return;
        }

        /* init ->work of the whole link before punting */
        io_prep_async_link(req);

        /*
         * Not expected to happen, but if we do have a bug where this _can_
         * happen, catch it here and ensure the request is marked as
         * canceled. That will make io-wq go through the usual work cancel
         * procedure rather than attempt to run this request (or create a new
         * worker for it).
         */
        if (WARN_ON_ONCE(!same_thread_group(tctx->task, current)))
                atomic_or(IO_WQ_WORK_CANCEL, &req->work.flags);

        trace_io_uring_queue_async_work(req, io_wq_is_hashed(&req->work));
        io_wq_enqueue(tctx->io_wq, &req->work);
}

static void io_req_queue_iowq_tw(struct io_tw_req tw_req, io_tw_token_t tw)
{
        io_queue_iowq(tw_req.req);
}

void io_req_queue_iowq(struct io_kiocb *req)
{
        req->io_task_work.func = io_req_queue_iowq_tw;
        io_req_task_work_add(req);
}

unsigned io_linked_nr(struct io_kiocb *req)
{
        struct io_kiocb *tmp;
        unsigned nr = 0;

        io_for_each_link(tmp, req)
                nr++;
        return nr;
}

static __cold noinline void io_queue_deferred(struct io_ring_ctx *ctx)
{
        bool drain_seen = false, first = true;

        lockdep_assert_held(&ctx->uring_lock);
        __io_req_caches_free(ctx);

        while (!list_empty(&ctx->defer_list)) {
                struct io_defer_entry *de = list_first_entry(&ctx->defer_list,
                                                struct io_defer_entry, list);

                drain_seen |= de->req->flags & REQ_F_IO_DRAIN;
                if ((drain_seen || first) && ctx->nr_req_allocated != ctx->nr_drained)
                        return;

                list_del_init(&de->list);
                ctx->nr_drained -= io_linked_nr(de->req);
                io_req_task_queue(de->req);
                kfree(de);
                first = false;
        }
}

void __io_commit_cqring_flush(struct io_ring_ctx *ctx)
{
        if (ctx->poll_activated)
                io_poll_wq_wake(ctx);
        if (ctx->off_timeout_used)
                io_flush_timeouts(ctx);
        if (ctx->has_evfd)
                io_eventfd_signal(ctx, true);
}

static inline void __io_cq_lock(struct io_ring_ctx *ctx)
{
        if (!ctx->lockless_cq)
                spin_lock(&ctx->completion_lock);
}

static inline void io_cq_lock(struct io_ring_ctx *ctx)
        __acquires(ctx->completion_lock)
{
        spin_lock(&ctx->completion_lock);
}

static inline void __io_cq_unlock_post(struct io_ring_ctx *ctx)
{
        io_commit_cqring(ctx);
        if (!ctx->task_complete) {
                if (!ctx->lockless_cq)
                        spin_unlock(&ctx->completion_lock);
                /* IOPOLL rings only need to wake up if it's also SQPOLL */
                if (!ctx->syscall_iopoll)
                        io_cqring_wake(ctx);
        }
        io_commit_cqring_flush(ctx);
}

static void io_cq_unlock_post(struct io_ring_ctx *ctx)
        __releases(ctx->completion_lock)
{
        io_commit_cqring(ctx);
        spin_unlock(&ctx->completion_lock);
        io_cqring_wake(ctx);
        io_commit_cqring_flush(ctx);
}

static void __io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool dying)
{
        lockdep_assert_held(&ctx->uring_lock);

        /* don't abort if we're dying, entries must get freed */
        if (!dying && __io_cqring_events(ctx) == ctx->cq_entries)
                return;

        io_cq_lock(ctx);
        while (!list_empty(&ctx->cq_overflow_list)) {
                size_t cqe_size = sizeof(struct io_uring_cqe);
                struct io_uring_cqe *cqe;
                struct io_overflow_cqe *ocqe;
                bool is_cqe32 = false;

                ocqe = list_first_entry(&ctx->cq_overflow_list,
                                        struct io_overflow_cqe, list);
                if (ocqe->cqe.flags & IORING_CQE_F_32 ||
                    ctx->flags & IORING_SETUP_CQE32) {
                        is_cqe32 = true;
                        cqe_size <<= 1;
                }
                if (ctx->flags & IORING_SETUP_CQE32)
                        is_cqe32 = false;

                if (!dying) {
                        if (!io_get_cqe_overflow(ctx, &cqe, true, is_cqe32))
                                break;
                        memcpy(cqe, &ocqe->cqe, cqe_size);
                }
                list_del(&ocqe->list);
                kfree(ocqe);

                /*
                 * For silly syzbot cases that deliberately overflow by huge
                 * amounts, check if we need to resched and drop and
                 * reacquire the locks if so. Nothing real would ever hit this.
                 * Ideally we'd have a non-posting unlock for this, but hard
                 * to care for a non-real case.
                 */
                if (need_resched()) {
                        ctx->cqe_sentinel = ctx->cqe_cached;
                        io_cq_unlock_post(ctx);
                        mutex_unlock(&ctx->uring_lock);
                        cond_resched();
                        mutex_lock(&ctx->uring_lock);
                        io_cq_lock(ctx);
                }
        }

        if (list_empty(&ctx->cq_overflow_list)) {
                clear_bit(IO_CHECK_CQ_OVERFLOW_BIT, &ctx->check_cq);
                atomic_andnot(IORING_SQ_CQ_OVERFLOW, &ctx->rings->sq_flags);
        }
        io_cq_unlock_post(ctx);
}

static void io_cqring_overflow_kill(struct io_ring_ctx *ctx)
{
        if (ctx->rings)
                __io_cqring_overflow_flush(ctx, true);
}

void io_cqring_do_overflow_flush(struct io_ring_ctx *ctx)
{
        mutex_lock(&ctx->uring_lock);
        __io_cqring_overflow_flush(ctx, false);
        mutex_unlock(&ctx->uring_lock);
}

/* must to be called somewhat shortly after putting a request */
static inline void io_put_task(struct io_kiocb *req)
{
        struct io_uring_task *tctx = req->tctx;

        if (likely(tctx->task == current)) {
                tctx->cached_refs++;
        } else {
                percpu_counter_sub(&tctx->inflight, 1);
                if (unlikely(atomic_read(&tctx->in_cancel)))
                        wake_up(&tctx->wait);
                put_task_struct(tctx->task);
        }
}

void io_task_refs_refill(struct io_uring_task *tctx)
{
        unsigned int refill = -tctx->cached_refs + IO_TCTX_REFS_CACHE_NR;

        percpu_counter_add(&tctx->inflight, refill);
        refcount_add(refill, &current->usage);
        tctx->cached_refs += refill;
}

__cold void io_uring_drop_tctx_refs(struct task_struct *task)
{
        struct io_uring_task *tctx = task->io_uring;
        unsigned int refs = tctx->cached_refs;

        if (refs) {
                tctx->cached_refs = 0;
                percpu_counter_sub(&tctx->inflight, refs);
                put_task_struct_many(task, refs);
        }
}

static __cold bool io_cqring_add_overflow(struct io_ring_ctx *ctx,
                                          struct io_overflow_cqe *ocqe)
{
        lockdep_assert_held(&ctx->completion_lock);

        if (!ocqe) {
                struct io_rings *r = ctx->rings;

                /*
                 * If we're in ring overflow flush mode, or in task cancel mode,
                 * or cannot allocate an overflow entry, then we need to drop it
                 * on the floor.
                 */
                WRITE_ONCE(r->cq_overflow, READ_ONCE(r->cq_overflow) + 1);
                set_bit(IO_CHECK_CQ_DROPPED_BIT, &ctx->check_cq);
                return false;
        }
        if (list_empty(&ctx->cq_overflow_list)) {
                set_bit(IO_CHECK_CQ_OVERFLOW_BIT, &ctx->check_cq);
                atomic_or(IORING_SQ_CQ_OVERFLOW, &ctx->rings->sq_flags);

        }
        list_add_tail(&ocqe->list, &ctx->cq_overflow_list);
        return true;
}

static struct io_overflow_cqe *io_alloc_ocqe(struct io_ring_ctx *ctx,
                                             struct io_cqe *cqe,
                                             struct io_big_cqe *big_cqe, gfp_t gfp)
{
        struct io_overflow_cqe *ocqe;
        size_t ocq_size = sizeof(struct io_overflow_cqe);
        bool is_cqe32 = false;

        if (cqe->flags & IORING_CQE_F_32 || ctx->flags & IORING_SETUP_CQE32) {
                is_cqe32 = true;
                ocq_size += sizeof(struct io_uring_cqe);
        }

        ocqe = kzalloc(ocq_size, gfp | __GFP_ACCOUNT);
        trace_io_uring_cqe_overflow(ctx, cqe->user_data, cqe->res, cqe->flags, ocqe);
        if (ocqe) {
                ocqe->cqe.user_data = cqe->user_data;
                ocqe->cqe.res = cqe->res;
                ocqe->cqe.flags = cqe->flags;
                if (is_cqe32 && big_cqe) {
                        ocqe->cqe.big_cqe[0] = big_cqe->extra1;
                        ocqe->cqe.big_cqe[1] = big_cqe->extra2;
                }
        }
        if (big_cqe)
                big_cqe->extra1 = big_cqe->extra2 = 0;
        return ocqe;
}

/*
 * Fill an empty dummy CQE, in case alignment is off for posting a 32b CQE
 * because the ring is a single 16b entry away from wrapping.
 */
static bool io_fill_nop_cqe(struct io_ring_ctx *ctx, unsigned int off)
{
        if (__io_cqring_events(ctx) < ctx->cq_entries) {
                struct io_uring_cqe *cqe = &ctx->rings->cqes[off];

                cqe->user_data = 0;
                cqe->res = 0;
                cqe->flags = IORING_CQE_F_SKIP;
                ctx->cached_cq_tail++;
                return true;
        }
        return false;
}

/*
 * writes to the cq entry need to come after reading head; the
 * control dependency is enough as we're using WRITE_ONCE to
 * fill the cq entry
 */
bool io_cqe_cache_refill(struct io_ring_ctx *ctx, bool overflow, bool cqe32)
{
        struct io_rings *rings = ctx->rings;
        unsigned int off = ctx->cached_cq_tail & (ctx->cq_entries - 1);
        unsigned int free, queued, len;

        /*
         * Posting into the CQ when there are pending overflowed CQEs may break
         * ordering guarantees, which will affect links, F_MORE users and more.
         * Force overflow the completion.
         */
        if (!overflow && (ctx->check_cq & BIT(IO_CHECK_CQ_OVERFLOW_BIT)))
                return false;

        /*
         * Post dummy CQE if a 32b CQE is needed and there's only room for a
         * 16b CQE before the ring wraps.
         */
        if (cqe32 && off + 1 == ctx->cq_entries) {
                if (!io_fill_nop_cqe(ctx, off))
                        return false;
                off = 0;
        }

        /* userspace may cheat modifying the tail, be safe and do min */
        queued = min(__io_cqring_events(ctx), ctx->cq_entries);
        free = ctx->cq_entries - queued;
        /* we need a contiguous range, limit based on the current array offset */
        len = min(free, ctx->cq_entries - off);
        if (len < (cqe32 + 1))
                return false;

        if (ctx->flags & IORING_SETUP_CQE32) {
                off <<= 1;
                len <<= 1;
        }

        ctx->cqe_cached = &rings->cqes[off];
        ctx->cqe_sentinel = ctx->cqe_cached + len;
        return true;
}

static bool io_fill_cqe_aux32(struct io_ring_ctx *ctx,
                              struct io_uring_cqe src_cqe[2])
{
        struct io_uring_cqe *cqe;

        if (WARN_ON_ONCE(!(ctx->flags & (IORING_SETUP_CQE32|IORING_SETUP_CQE_MIXED))))
                return false;
        if (unlikely(!io_get_cqe(ctx, &cqe, true)))
                return false;

        memcpy(cqe, src_cqe, 2 * sizeof(*cqe));
        trace_io_uring_complete(ctx, NULL, cqe);
        return true;
}

static bool io_fill_cqe_aux(struct io_ring_ctx *ctx, u64 user_data, s32 res,
                              u32 cflags)
{
        bool cqe32 = cflags & IORING_CQE_F_32;
        struct io_uring_cqe *cqe;

        if (likely(io_get_cqe(ctx, &cqe, cqe32))) {
                WRITE_ONCE(cqe->user_data, user_data);
                WRITE_ONCE(cqe->res, res);
                WRITE_ONCE(cqe->flags, cflags);

                if (cqe32) {
                        WRITE_ONCE(cqe->big_cqe[0], 0);
                        WRITE_ONCE(cqe->big_cqe[1], 0);
                }

                trace_io_uring_complete(ctx, NULL, cqe);
                return true;
        }
        return false;
}

static inline struct io_cqe io_init_cqe(u64 user_data, s32 res, u32 cflags)
{
        return (struct io_cqe) { .user_data = user_data, .res = res, .flags = cflags };
}

static __cold void io_cqe_overflow(struct io_ring_ctx *ctx, struct io_cqe *cqe,
                                   struct io_big_cqe *big_cqe)
{
        struct io_overflow_cqe *ocqe;

        ocqe = io_alloc_ocqe(ctx, cqe, big_cqe, GFP_KERNEL);
        spin_lock(&ctx->completion_lock);
        io_cqring_add_overflow(ctx, ocqe);
        spin_unlock(&ctx->completion_lock);
}

static __cold bool io_cqe_overflow_locked(struct io_ring_ctx *ctx,
                                          struct io_cqe *cqe,
                                          struct io_big_cqe *big_cqe)
{
        struct io_overflow_cqe *ocqe;

        ocqe = io_alloc_ocqe(ctx, cqe, big_cqe, GFP_NOWAIT);
        return io_cqring_add_overflow(ctx, ocqe);
}

bool io_post_aux_cqe(struct io_ring_ctx *ctx, u64 user_data, s32 res, u32 cflags)
{
        bool filled;

        io_cq_lock(ctx);
        filled = io_fill_cqe_aux(ctx, user_data, res, cflags);
        if (unlikely(!filled)) {
                struct io_cqe cqe = io_init_cqe(user_data, res, cflags);

                filled = io_cqe_overflow_locked(ctx, &cqe, NULL);
        }
        io_cq_unlock_post(ctx);
        return filled;
}

/*
 * Must be called from inline task_work so we know a flush will happen later,
 * and obviously with ctx->uring_lock held (tw always has that).
 */
void io_add_aux_cqe(struct io_ring_ctx *ctx, u64 user_data, s32 res, u32 cflags)
{
        lockdep_assert_held(&ctx->uring_lock);
        lockdep_assert(ctx->lockless_cq);

        if (!io_fill_cqe_aux(ctx, user_data, res, cflags)) {
                struct io_cqe cqe = io_init_cqe(user_data, res, cflags);

                io_cqe_overflow(ctx, &cqe, NULL);
        }
        ctx->submit_state.cq_flush = true;
}

/*
 * A helper for multishot requests posting additional CQEs.
 * Should only be used from a task_work including IO_URING_F_MULTISHOT.
 */
bool io_req_post_cqe(struct io_kiocb *req, s32 res, u32 cflags)
{
        struct io_ring_ctx *ctx = req->ctx;
        bool posted;

        /*
         * If multishot has already posted deferred completions, ensure that
         * those are flushed first before posting this one. If not, CQEs
         * could get reordered.
         */
        if (!wq_list_empty(&ctx->submit_state.compl_reqs))
                __io_submit_flush_completions(ctx);

        lockdep_assert(!io_wq_current_is_worker());
        lockdep_assert_held(&ctx->uring_lock);

        if (!ctx->lockless_cq) {
                spin_lock(&ctx->completion_lock);
                posted = io_fill_cqe_aux(ctx, req->cqe.user_data, res, cflags);
                spin_unlock(&ctx->completion_lock);
        } else {
                posted = io_fill_cqe_aux(ctx, req->cqe.user_data, res, cflags);
        }

        ctx->submit_state.cq_flush = true;
        return posted;
}

/*
 * A helper for multishot requests posting additional CQEs.
 * Should only be used from a task_work including IO_URING_F_MULTISHOT.
 */
bool io_req_post_cqe32(struct io_kiocb *req, struct io_uring_cqe cqe[2])
{
        struct io_ring_ctx *ctx = req->ctx;
        bool posted;

        lockdep_assert(!io_wq_current_is_worker());
        lockdep_assert_held(&ctx->uring_lock);

        cqe[0].user_data = req->cqe.user_data;
        if (!ctx->lockless_cq) {
                spin_lock(&ctx->completion_lock);
                posted = io_fill_cqe_aux32(ctx, cqe);
                spin_unlock(&ctx->completion_lock);
        } else {
                posted = io_fill_cqe_aux32(ctx, cqe);
        }

        ctx->submit_state.cq_flush = true;
        return posted;
}

static void io_req_complete_post(struct io_kiocb *req, unsigned issue_flags)
{
        struct io_ring_ctx *ctx = req->ctx;
        bool completed = true;

        /*
         * All execution paths but io-wq use the deferred completions by
         * passing IO_URING_F_COMPLETE_DEFER and thus should not end up here.
         */
        if (WARN_ON_ONCE(!(issue_flags & IO_URING_F_IOWQ)))
                return;

        /*
         * Handle special CQ sync cases via task_work. DEFER_TASKRUN requires
         * the submitter task context, IOPOLL protects with uring_lock.
         */
        if (ctx->lockless_cq || (req->flags & REQ_F_REISSUE)) {
defer_complete:
                req->io_task_work.func = io_req_task_complete;
                io_req_task_work_add(req);
                return;
        }

        io_cq_lock(ctx);
        if (!(req->flags & REQ_F_CQE_SKIP))
                completed = io_fill_cqe_req(ctx, req);
        io_cq_unlock_post(ctx);

        if (!completed)
                goto defer_complete;

        /*
         * We don't free the request here because we know it's called from
         * io-wq only, which holds a reference, so it cannot be the last put.
         */
        req_ref_put(req);
}

void io_req_defer_failed(struct io_kiocb *req, s32 res)
        __must_hold(&ctx->uring_lock)
{
        const struct io_cold_def *def = &io_cold_defs[req->opcode];

        lockdep_assert_held(&req->ctx->uring_lock);

        req_set_fail(req);
        io_req_set_res(req, res, io_put_kbuf(req, res, NULL));
        if (def->fail)
                def->fail(req);
        io_req_complete_defer(req);
}

/*
 * A request might get retired back into the request caches even before opcode
 * handlers and io_issue_sqe() are done with it, e.g. inline completion path.
 * Because of that, io_alloc_req() should be called only under ->uring_lock
 * and with extra caution to not get a request that is still worked on.
 */
__cold bool __io_alloc_req_refill(struct io_ring_ctx *ctx)
        __must_hold(&ctx->uring_lock)
{
        gfp_t gfp = GFP_KERNEL | __GFP_NOWARN | __GFP_ZERO;
        void *reqs[IO_REQ_ALLOC_BATCH];
        int ret;

        ret = kmem_cache_alloc_bulk(req_cachep, gfp, ARRAY_SIZE(reqs), reqs);

        /*
         * Bulk alloc is all-or-nothing. If we fail to get a batch,
         * retry single alloc to be on the safe side.
         */
        if (unlikely(ret <= 0)) {
                reqs[0] = kmem_cache_alloc(req_cachep, gfp);
                if (!reqs[0])
                        return false;
                ret = 1;
        }

        percpu_ref_get_many(&ctx->refs, ret);
        ctx->nr_req_allocated += ret;

        while (ret--) {
                struct io_kiocb *req = reqs[ret];

                io_req_add_to_cache(req, ctx);
        }
        return true;
}

__cold void io_free_req(struct io_kiocb *req)
{
        /* refs were already put, restore them for io_req_task_complete() */
        req->flags &= ~REQ_F_REFCOUNT;
        /* we only want to free it, don't post CQEs */
        req->flags |= REQ_F_CQE_SKIP;
        req->io_task_work.func = io_req_task_complete;
        io_req_task_work_add(req);
}

static void __io_req_find_next_prep(struct io_kiocb *req)
{
        struct io_ring_ctx *ctx = req->ctx;

        spin_lock(&ctx->completion_lock);
        io_disarm_next(req);
        spin_unlock(&ctx->completion_lock);
}

static inline struct io_kiocb *io_req_find_next(struct io_kiocb *req)
{
        struct io_kiocb *nxt;

        /*
         * If LINK is set, we have dependent requests in this chain. If we
         * didn't fail this request, queue the first one up, moving any other
         * dependencies to the next request. In case of failure, fail the rest
         * of the chain.
         */
        if (unlikely(req->flags & IO_DISARM_MASK))
                __io_req_find_next_prep(req);
        nxt = req->link;
        req->link = NULL;
        return nxt;
}

static void io_req_task_cancel(struct io_tw_req tw_req, io_tw_token_t tw)
{
        struct io_kiocb *req = tw_req.req;

        io_tw_lock(req->ctx, tw);
        io_req_defer_failed(req, req->cqe.res);
}

void io_req_task_submit(struct io_tw_req tw_req, io_tw_token_t tw)
{
        struct io_kiocb *req = tw_req.req;
        struct io_ring_ctx *ctx = req->ctx;

        io_tw_lock(ctx, tw);
        if (unlikely(tw.cancel))
                io_req_defer_failed(req, -EFAULT);
        else if (req->flags & REQ_F_FORCE_ASYNC)
                io_queue_iowq(req);
        else
                io_queue_sqe(req, 0);
}

void io_req_task_queue_fail(struct io_kiocb *req, int ret)
{
        io_req_set_res(req, ret, 0);
        req->io_task_work.func = io_req_task_cancel;
        io_req_task_work_add(req);
}

void io_req_task_queue(struct io_kiocb *req)
{
        req->io_task_work.func = io_req_task_submit;
        io_req_task_work_add(req);
}

void io_queue_next(struct io_kiocb *req)
{
        struct io_kiocb *nxt = io_req_find_next(req);

        if (nxt)
                io_req_task_queue(nxt);
}

static inline void io_req_put_rsrc_nodes(struct io_kiocb *req)
{
        if (req->file_node) {
                io_put_rsrc_node(req->ctx, req->file_node);
                req->file_node = NULL;
        }
        if (req->flags & REQ_F_BUF_NODE)
                io_put_rsrc_node(req->ctx, req->buf_node);
}

static void io_free_batch_list(struct io_ring_ctx *ctx,
                               struct io_wq_work_node *node)
        __must_hold(&ctx->uring_lock)
{
        do {
                struct io_kiocb *req = container_of(node, struct io_kiocb,
                                                    comp_list);

                if (unlikely(req->flags & IO_REQ_CLEAN_SLOW_FLAGS)) {
                        if (req->flags & REQ_F_REISSUE) {
                                node = req->comp_list.next;
                                req->flags &= ~REQ_F_REISSUE;
                                io_queue_iowq(req);
                                continue;
                        }
                        if (req->flags & REQ_F_REFCOUNT) {
                                node = req->comp_list.next;
                                if (!req_ref_put_and_test(req))
                                        continue;
                        }
                        if ((req->flags & REQ_F_POLLED) && req->apoll) {
                                struct async_poll *apoll = req->apoll;

                                if (apoll->double_poll)
                                        kfree(apoll->double_poll);
                                io_cache_free(&ctx->apoll_cache, apoll);
                                req->flags &= ~REQ_F_POLLED;
                        }
                        if (req->flags & IO_REQ_LINK_FLAGS)
                                io_queue_next(req);
                        if (unlikely(req->flags & IO_REQ_CLEAN_FLAGS))
                                io_clean_op(req);
                }
                io_put_file(req);
                io_req_put_rsrc_nodes(req);
                io_put_task(req);

                node = req->comp_list.next;
                io_req_add_to_cache(req, ctx);
        } while (node);
}

void __io_submit_flush_completions(struct io_ring_ctx *ctx)
        __must_hold(&ctx->uring_lock)
{
        struct io_submit_state *state = &ctx->submit_state;
        struct io_wq_work_node *node;

        __io_cq_lock(ctx);
        __wq_list_for_each(node, &state->compl_reqs) {
                struct io_kiocb *req = container_of(node, struct io_kiocb,
                                            comp_list);

                /*
                 * Requests marked with REQUEUE should not post a CQE, they
                 * will go through the io-wq retry machinery and post one
                 * later.
                 */
                if (!(req->flags & (REQ_F_CQE_SKIP | REQ_F_REISSUE)) &&
                    unlikely(!io_fill_cqe_req(ctx, req))) {
                        if (ctx->lockless_cq)
                                io_cqe_overflow(ctx, &req->cqe, &req->big_cqe);
                        else
                                io_cqe_overflow_locked(ctx, &req->cqe, &req->big_cqe);
                }
        }
        __io_cq_unlock_post(ctx);

        if (!wq_list_empty(&state->compl_reqs)) {
                io_free_batch_list(ctx, state->compl_reqs.first);
                INIT_WQ_LIST(&state->compl_reqs);
        }

        if (unlikely(ctx->drain_active))
                io_queue_deferred(ctx);

        ctx->submit_state.cq_flush = false;
}

/*
 * We can't just wait for polled events to come to us, we have to actively
 * find and complete them.
 */
__cold void io_iopoll_try_reap_events(struct io_ring_ctx *ctx)
{
        if (!(ctx->flags & IORING_SETUP_IOPOLL))
                return;

        mutex_lock(&ctx->uring_lock);
        while (!list_empty(&ctx->iopoll_list)) {
                /* let it sleep and repeat later if can't complete a request */
                if (io_do_iopoll(ctx, true) == 0)
                        break;
                /*
                 * Ensure we allow local-to-the-cpu processing to take place,
                 * in this case we need to ensure that we reap all events.
                 * Also let task_work, etc. to progress by releasing the mutex
                 */
                if (need_resched()) {
                        mutex_unlock(&ctx->uring_lock);
                        cond_resched();
                        mutex_lock(&ctx->uring_lock);
                }
        }
        mutex_unlock(&ctx->uring_lock);

        if (ctx->flags & IORING_SETUP_DEFER_TASKRUN)
                io_move_task_work_from_local(ctx);
}

static int io_iopoll_check(struct io_ring_ctx *ctx, unsigned int min_events)
{
        unsigned int nr_events = 0;
        unsigned long check_cq;

        min_events = min(min_events, ctx->cq_entries);

        lockdep_assert_held(&ctx->uring_lock);

        if (!io_allowed_run_tw(ctx))
                return -EEXIST;

        check_cq = READ_ONCE(ctx->check_cq);
        if (unlikely(check_cq)) {
                if (check_cq & BIT(IO_CHECK_CQ_OVERFLOW_BIT))
                        __io_cqring_overflow_flush(ctx, false);
                /*
                 * Similarly do not spin if we have not informed the user of any
                 * dropped CQE.
                 */
                if (check_cq & BIT(IO_CHECK_CQ_DROPPED_BIT))
                        return -EBADR;
        }
        /*
         * Don't enter poll loop if we already have events pending.
         * If we do, we can potentially be spinning for commands that
         * already triggered a CQE (eg in error).
         */
        if (io_cqring_events(ctx))
                return 0;

        do {
                int ret = 0;

                /*
                 * If a submit got punted to a workqueue, we can have the
                 * application entering polling for a command before it gets
                 * issued. That app will hold the uring_lock for the duration
                 * of the poll right here, so we need to take a breather every
                 * now and then to ensure that the issue has a chance to add
                 * the poll to the issued list. Otherwise we can spin here
                 * forever, while the workqueue is stuck trying to acquire the
                 * very same mutex.
                 */
                if (list_empty(&ctx->iopoll_list) || io_task_work_pending(ctx)) {
                        u32 tail = ctx->cached_cq_tail;

                        (void) io_run_local_work_locked(ctx, min_events);

                        if (task_work_pending(current) || list_empty(&ctx->iopoll_list)) {
                                mutex_unlock(&ctx->uring_lock);
                                io_run_task_work();
                                mutex_lock(&ctx->uring_lock);
                        }
                        /* some requests don't go through iopoll_list */
                        if (tail != ctx->cached_cq_tail || list_empty(&ctx->iopoll_list))
                                break;
                }
                ret = io_do_iopoll(ctx, !min_events);
                if (unlikely(ret < 0))
                        return ret;

                if (task_sigpending(current))
                        return -EINTR;
                if (need_resched())
                        break;

                nr_events += ret;
        } while (nr_events < min_events);

        return 0;
}

void io_req_task_complete(struct io_tw_req tw_req, io_tw_token_t tw)
{
        io_req_complete_defer(tw_req.req);
}

/*
 * After the iocb has been issued, it's safe to be found on the poll list.
 * Adding the kiocb to the list AFTER submission ensures that we don't
 * find it from a io_do_iopoll() thread before the issuer is done
 * accessing the kiocb cookie.
 */
static void io_iopoll_req_issued(struct io_kiocb *req, unsigned int issue_flags)
{
        struct io_ring_ctx *ctx = req->ctx;
        const bool needs_lock = issue_flags & IO_URING_F_UNLOCKED;

        /* workqueue context doesn't hold uring_lock, grab it now */
        if (unlikely(needs_lock))
                mutex_lock(&ctx->uring_lock);

        /*
         * Track whether we have multiple files in our lists. This will impact
         * how we do polling eventually, not spinning if we're on potentially
         * different devices.
         */
        if (list_empty(&ctx->iopoll_list)) {
                ctx->poll_multi_queue = false;
        } else if (!ctx->poll_multi_queue) {
                struct io_kiocb *list_req;

                list_req = list_first_entry(&ctx->iopoll_list, struct io_kiocb, iopoll_node);
                if (list_req->file != req->file)
                        ctx->poll_multi_queue = true;
        }

        list_add_tail(&req->iopoll_node, &ctx->iopoll_list);

        if (unlikely(needs_lock)) {
                /*
                 * If IORING_SETUP_SQPOLL is enabled, sqes are either handle
                 * in sq thread task context or in io worker task context. If
                 * current task context is sq thread, we don't need to check
                 * whether should wake up sq thread.
                 */
                if ((ctx->flags & IORING_SETUP_SQPOLL) &&
                    wq_has_sleeper(&ctx->sq_data->wait))
                        wake_up(&ctx->sq_data->wait);

                mutex_unlock(&ctx->uring_lock);
        }
}

io_req_flags_t io_file_get_flags(struct file *file)
{
        io_req_flags_t res = 0;

        BUILD_BUG_ON(REQ_F_ISREG_BIT != REQ_F_SUPPORT_NOWAIT_BIT + 1);

        if (S_ISREG(file_inode(file)->i_mode))
                res |= REQ_F_ISREG;
        if ((file->f_flags & O_NONBLOCK) || (file->f_mode & FMODE_NOWAIT))
                res |= REQ_F_SUPPORT_NOWAIT;
        return res;
}

static __cold void io_drain_req(struct io_kiocb *req)
        __must_hold(&ctx->uring_lock)
{
        struct io_ring_ctx *ctx = req->ctx;
        bool drain = req->flags & IOSQE_IO_DRAIN;
        struct io_defer_entry *de;

        de = kmalloc_obj(*de, GFP_KERNEL_ACCOUNT);
        if (!de) {
                io_req_defer_failed(req, -ENOMEM);
                return;
        }

        io_prep_async_link(req);
        trace_io_uring_defer(req);
        de->req = req;

        ctx->nr_drained += io_linked_nr(req);
        list_add_tail(&de->list, &ctx->defer_list);
        io_queue_deferred(ctx);
        if (!drain && list_empty(&ctx->defer_list))
                ctx->drain_active = false;
}

static bool io_assign_file(struct io_kiocb *req, const struct io_issue_def *def,
                           unsigned int issue_flags)
{
        if (req->file || !def->needs_file)
                return true;

        if (req->flags & REQ_F_FIXED_FILE)
                req->file = io_file_get_fixed(req, req->cqe.fd, issue_flags);
        else
                req->file = io_file_get_normal(req, req->cqe.fd);

        return !!req->file;
}

#define REQ_ISSUE_SLOW_FLAGS    (REQ_F_CREDS | REQ_F_ARM_LTIMEOUT)

static inline int __io_issue_sqe(struct io_kiocb *req,
                                 unsigned int issue_flags,
                                 const struct io_issue_def *def)
{
        const struct cred *creds = NULL;
        struct io_kiocb *link = NULL;
        int ret;

        if (unlikely(req->flags & REQ_ISSUE_SLOW_FLAGS)) {
                if ((req->flags & REQ_F_CREDS) && req->creds != current_cred())
                        creds = override_creds(req->creds);
                if (req->flags & REQ_F_ARM_LTIMEOUT)
                        link = __io_prep_linked_timeout(req);
        }

        if (!def->audit_skip)
                audit_uring_entry(req->opcode);

        ret = def->issue(req, issue_flags);

        if (!def->audit_skip)
                audit_uring_exit(!ret, ret);

        if (unlikely(creds || link)) {
                if (creds)
                        revert_creds(creds);
                if (link)
                        io_queue_linked_timeout(link);
        }

        return ret;
}

static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)
{
        const struct io_issue_def *def = &io_issue_defs[req->opcode];
        int ret;

        if (unlikely(!io_assign_file(req, def, issue_flags)))
                return -EBADF;

        ret = __io_issue_sqe(req, issue_flags, def);

        if (ret == IOU_COMPLETE) {
                if (issue_flags & IO_URING_F_COMPLETE_DEFER)
                        io_req_complete_defer(req);
                else
                        io_req_complete_post(req, issue_flags);

                return 0;
        }

        if (ret == IOU_ISSUE_SKIP_COMPLETE) {
                ret = 0;

                /* If the op doesn't have a file, we're not polling for it */
                if ((req->ctx->flags & IORING_SETUP_IOPOLL) && def->iopoll_queue)
                        io_iopoll_req_issued(req, issue_flags);
        }
        return ret;
}

int io_poll_issue(struct io_kiocb *req, io_tw_token_t tw)
{
        const unsigned int issue_flags = IO_URING_F_NONBLOCK |
                                         IO_URING_F_MULTISHOT |
                                         IO_URING_F_COMPLETE_DEFER;
        int ret;

        io_tw_lock(req->ctx, tw);

        WARN_ON_ONCE(!req->file);
        if (WARN_ON_ONCE(req->ctx->flags & IORING_SETUP_IOPOLL))
                return -EFAULT;

        ret = __io_issue_sqe(req, issue_flags, &io_issue_defs[req->opcode]);

        WARN_ON_ONCE(ret == IOU_ISSUE_SKIP_COMPLETE);
        return ret;
}

struct io_wq_work *io_wq_free_work(struct io_wq_work *work)
{
        struct io_kiocb *req = container_of(work, struct io_kiocb, work);
        struct io_kiocb *nxt = NULL;

        if (req_ref_put_and_test_atomic(req)) {
                if (req->flags & IO_REQ_LINK_FLAGS)
                        nxt = io_req_find_next(req);
                io_free_req(req);
        }
        return nxt ? &nxt->work : NULL;
}

void io_wq_submit_work(struct io_wq_work *work)
{
        struct io_kiocb *req = container_of(work, struct io_kiocb, work);
        const struct io_issue_def *def = &io_issue_defs[req->opcode];
        unsigned int issue_flags = IO_URING_F_UNLOCKED | IO_URING_F_IOWQ;
        bool needs_poll = false;
        int ret = 0, err = -ECANCELED;

        /* one will be dropped by io_wq_free_work() after returning to io-wq */
        if (!(req->flags & REQ_F_REFCOUNT))
                __io_req_set_refcount(req, 2);
        else
                req_ref_get(req);

        /* either cancelled or io-wq is dying, so don't touch tctx->iowq */
        if (atomic_read(&work->flags) & IO_WQ_WORK_CANCEL) {
fail:
                io_req_task_queue_fail(req, err);
                return;
        }
        if (!io_assign_file(req, def, issue_flags)) {
                err = -EBADF;
                atomic_or(IO_WQ_WORK_CANCEL, &work->flags);
                goto fail;
        }

        /*
         * If DEFER_TASKRUN is set, it's only allowed to post CQEs from the
         * submitter task context. Final request completions are handed to the
         * right context, however this is not the case of auxiliary CQEs,
         * which is the main mean of operation for multishot requests.
         * Don't allow any multishot execution from io-wq. It's more restrictive
         * than necessary and also cleaner.
         */
        if (req->flags & (REQ_F_MULTISHOT|REQ_F_APOLL_MULTISHOT)) {
                err = -EBADFD;
                if (!io_file_can_poll(req))
                        goto fail;
                if (req->file->f_flags & O_NONBLOCK ||
                    req->file->f_mode & FMODE_NOWAIT) {
                        err = -ECANCELED;
                        if (io_arm_poll_handler(req, issue_flags) != IO_APOLL_OK)
                                goto fail;
                        return;
                } else {
                        req->flags &= ~(REQ_F_APOLL_MULTISHOT|REQ_F_MULTISHOT);
                }
        }

        if (req->flags & REQ_F_FORCE_ASYNC) {
                bool opcode_poll = def->pollin || def->pollout;

                if (opcode_poll && io_file_can_poll(req)) {
                        needs_poll = true;
                        issue_flags |= IO_URING_F_NONBLOCK;
                }
        }

        do {
                ret = io_issue_sqe(req, issue_flags);
                if (ret != -EAGAIN)
                        break;

                /*
                 * If REQ_F_NOWAIT is set, then don't wait or retry with
                 * poll. -EAGAIN is final for that case.
                 */
                if (req->flags & REQ_F_NOWAIT)
                        break;

                /*
                 * We can get EAGAIN for iopolled IO even though we're
                 * forcing a sync submission from here, since we can't
                 * wait for request slots on the block side.
                 */
                if (!needs_poll) {
                        if (!(req->ctx->flags & IORING_SETUP_IOPOLL))
                                break;
                        if (io_wq_worker_stopped())
                                break;
                        cond_resched();
                        continue;
                }

                if (io_arm_poll_handler(req, issue_flags) == IO_APOLL_OK)
                        return;
                /* aborted or ready, in either case retry blocking */
                needs_poll = false;
                issue_flags &= ~IO_URING_F_NONBLOCK;
        } while (1);

        /* avoid locking problems by failing it from a clean context */
        if (ret)
                io_req_task_queue_fail(req, ret);
}

inline struct file *io_file_get_fixed(struct io_kiocb *req, int fd,
                                      unsigned int issue_flags)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct io_rsrc_node *node;
        struct file *file = NULL;

        io_ring_submit_lock(ctx, issue_flags);
        node = io_rsrc_node_lookup(&ctx->file_table.data, fd);
        if (node) {
                node->refs++;
                req->file_node = node;
                req->flags |= io_slot_flags(node);
                file = io_slot_file(node);
        }
        io_ring_submit_unlock(ctx, issue_flags);
        return file;
}

struct file *io_file_get_normal(struct io_kiocb *req, int fd)
{
        struct file *file = fget(fd);

        trace_io_uring_file_get(req, fd);

        /* we don't allow fixed io_uring files */
        if (file && io_is_uring_fops(file))
                io_req_track_inflight(req);
        return file;
}

static int io_req_sqe_copy(struct io_kiocb *req, unsigned int issue_flags)
{
        const struct io_cold_def *def = &io_cold_defs[req->opcode];

        if (req->flags & REQ_F_SQE_COPIED)
                return 0;
        req->flags |= REQ_F_SQE_COPIED;
        if (!def->sqe_copy)
                return 0;
        if (WARN_ON_ONCE(!(issue_flags & IO_URING_F_INLINE)))
                return -EFAULT;
        def->sqe_copy(req);
        return 0;
}

static void io_queue_async(struct io_kiocb *req, unsigned int issue_flags, int ret)
        __must_hold(&req->ctx->uring_lock)
{
        if (ret != -EAGAIN || (req->flags & REQ_F_NOWAIT)) {
fail:
                io_req_defer_failed(req, ret);
                return;
        }

        ret = io_req_sqe_copy(req, issue_flags);
        if (unlikely(ret))
                goto fail;

        switch (io_arm_poll_handler(req, 0)) {
        case IO_APOLL_READY:
                io_req_task_queue(req);
                break;
        case IO_APOLL_ABORTED:
                io_queue_iowq(req);
                break;
        case IO_APOLL_OK:
                break;
        }
}

static inline void io_queue_sqe(struct io_kiocb *req, unsigned int extra_flags)
        __must_hold(&req->ctx->uring_lock)
{
        unsigned int issue_flags = IO_URING_F_NONBLOCK |
                                   IO_URING_F_COMPLETE_DEFER | extra_flags;
        int ret;

        ret = io_issue_sqe(req, issue_flags);

        /*
         * We async punt it if the file wasn't marked NOWAIT, or if the file
         * doesn't support non-blocking read/write attempts
         */
        if (unlikely(ret))
                io_queue_async(req, issue_flags, ret);
}

static void io_queue_sqe_fallback(struct io_kiocb *req)
        __must_hold(&req->ctx->uring_lock)
{
        if (unlikely(req->flags & REQ_F_FAIL)) {
                /*
                 * We don't submit, fail them all, for that replace hardlinks
                 * with normal links. Extra REQ_F_LINK is tolerated.
                 */
                req->flags &= ~REQ_F_HARDLINK;
                req->flags |= REQ_F_LINK;
                io_req_defer_failed(req, req->cqe.res);
        } else {
                /* can't fail with IO_URING_F_INLINE */
                io_req_sqe_copy(req, IO_URING_F_INLINE);
                if (unlikely(req->ctx->drain_active))
                        io_drain_req(req);
                else
                        io_queue_iowq(req);
        }
}

/*
 * Check SQE restrictions (opcode and flags).
 *
 * Returns 'true' if SQE is allowed, 'false' otherwise.
 */
static inline bool io_check_restriction(struct io_ring_ctx *ctx,
                                        struct io_kiocb *req,
                                        unsigned int sqe_flags)
{
        if (!ctx->op_restricted)
                return true;
        if (!test_bit(req->opcode, ctx->restrictions.sqe_op))
                return false;

        if ((sqe_flags & ctx->restrictions.sqe_flags_required) !=
            ctx->restrictions.sqe_flags_required)
                return false;

        if (sqe_flags & ~(ctx->restrictions.sqe_flags_allowed |
                          ctx->restrictions.sqe_flags_required))
                return false;

        return true;
}

static void io_init_drain(struct io_ring_ctx *ctx)
{
        struct io_kiocb *head = ctx->submit_state.link.head;

        ctx->drain_active = true;
        if (head) {
                /*
                 * If we need to drain a request in the middle of a link, drain
                 * the head request and the next request/link after the current
                 * link. Considering sequential execution of links,
                 * REQ_F_IO_DRAIN will be maintained for every request of our
                 * link.
                 */
                head->flags |= REQ_F_IO_DRAIN | REQ_F_FORCE_ASYNC;
                ctx->drain_next = true;
        }
}

static __cold int io_init_fail_req(struct io_kiocb *req, int err)
{
        /* ensure per-opcode data is cleared if we fail before prep */
        memset(&req->cmd.data, 0, sizeof(req->cmd.data));
        return err;
}

static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
                       const struct io_uring_sqe *sqe, unsigned int *left)
        __must_hold(&ctx->uring_lock)
{
        const struct io_issue_def *def;
        unsigned int sqe_flags;
        int personality;
        u8 opcode;

        req->ctx = ctx;
        req->opcode = opcode = READ_ONCE(sqe->opcode);
        /* same numerical values with corresponding REQ_F_*, safe to copy */
        sqe_flags = READ_ONCE(sqe->flags);
        req->flags = (__force io_req_flags_t) sqe_flags;
        req->cqe.user_data = READ_ONCE(sqe->user_data);
        req->file = NULL;
        req->tctx = current->io_uring;
        req->cancel_seq_set = false;
        req->async_data = NULL;

        if (unlikely(opcode >= IORING_OP_LAST)) {
                req->opcode = 0;
                return io_init_fail_req(req, -EINVAL);
        }
        opcode = array_index_nospec(opcode, IORING_OP_LAST);

        def = &io_issue_defs[opcode];
        if (def->is_128 && !(ctx->flags & IORING_SETUP_SQE128)) {
                /*
                 * A 128b op on a non-128b SQ requires mixed SQE support as
                 * well as 2 contiguous entries.
                 */
                if (!(ctx->flags & IORING_SETUP_SQE_MIXED) || *left < 2 ||
                    (unsigned)(sqe - ctx->sq_sqes) >= ctx->sq_entries - 1)
                        return io_init_fail_req(req, -EINVAL);
                /*
                 * A 128b operation on a mixed SQ uses two entries, so we have
                 * to increment the head and cached refs, and decrement what's
                 * left.
                 */
                current->io_uring->cached_refs++;
                ctx->cached_sq_head++;
                (*left)--;
        }

        if (unlikely(sqe_flags & ~SQE_COMMON_FLAGS)) {
                /* enforce forwards compatibility on users */
                if (sqe_flags & ~SQE_VALID_FLAGS)
                        return io_init_fail_req(req, -EINVAL);
                if (sqe_flags & IOSQE_BUFFER_SELECT) {
                        if (!def->buffer_select)
                                return io_init_fail_req(req, -EOPNOTSUPP);
                        req->buf_index = READ_ONCE(sqe->buf_group);
                }
                if (sqe_flags & IOSQE_CQE_SKIP_SUCCESS)
                        ctx->drain_disabled = true;
                if (sqe_flags & IOSQE_IO_DRAIN) {
                        if (ctx->drain_disabled)
                                return io_init_fail_req(req, -EOPNOTSUPP);
                        io_init_drain(ctx);
                }
        }
        if (unlikely(ctx->op_restricted || ctx->drain_active || ctx->drain_next)) {
                if (!io_check_restriction(ctx, req, sqe_flags))
                        return io_init_fail_req(req, -EACCES);
                /* knock it to the slow queue path, will be drained there */
                if (ctx->drain_active)
                        req->flags |= REQ_F_FORCE_ASYNC;
                /* if there is no link, we're at "next" request and need to drain */
                if (unlikely(ctx->drain_next) && !ctx->submit_state.link.head) {
                        ctx->drain_next = false;
                        ctx->drain_active = true;
                        req->flags |= REQ_F_IO_DRAIN | REQ_F_FORCE_ASYNC;
                }
        }

        if (!def->ioprio && sqe->ioprio)
                return io_init_fail_req(req, -EINVAL);
        if (!def->iopoll && (ctx->flags & IORING_SETUP_IOPOLL))
                return io_init_fail_req(req, -EINVAL);

        if (def->needs_file) {
                struct io_submit_state *state = &ctx->submit_state;

                req->cqe.fd = READ_ONCE(sqe->fd);

                /*
                 * Plug now if we have more than 2 IO left after this, and the
                 * target is potentially a read/write to block based storage.
                 */
                if (state->need_plug && def->plug) {
                        state->plug_started = true;
                        state->need_plug = false;
                        blk_start_plug_nr_ios(&state->plug, state->submit_nr);
                }
        }

        personality = READ_ONCE(sqe->personality);
        if (personality) {
                int ret;

                req->creds = xa_load(&ctx->personalities, personality);
                if (!req->creds)
                        return io_init_fail_req(req, -EINVAL);
                get_cred(req->creds);
                ret = security_uring_override_creds(req->creds);
                if (ret) {
                        put_cred(req->creds);
                        return io_init_fail_req(req, ret);
                }
                req->flags |= REQ_F_CREDS;
        }

        return def->prep(req, sqe);
}

static __cold int io_submit_fail_init(const struct io_uring_sqe *sqe,
                                      struct io_kiocb *req, int ret)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct io_submit_link *link = &ctx->submit_state.link;
        struct io_kiocb *head = link->head;

        trace_io_uring_req_failed(sqe, req, ret);

        /*
         * Avoid breaking links in the middle as it renders links with SQPOLL
         * unusable. Instead of failing eagerly, continue assembling the link if
         * applicable and mark the head with REQ_F_FAIL. The link flushing code
         * should find the flag and handle the rest.
         */
        req_fail_link_node(req, ret);
        if (head && !(head->flags & REQ_F_FAIL))
                req_fail_link_node(head, -ECANCELED);

        if (!(req->flags & IO_REQ_LINK_FLAGS)) {
                if (head) {
                        link->last->link = req;
                        link->head = NULL;
                        req = head;
                }
                io_queue_sqe_fallback(req);
                return ret;
        }

        if (head)
                link->last->link = req;
        else
                link->head = req;
        link->last = req;
        return 0;
}

static inline int io_submit_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req,
                         const struct io_uring_sqe *sqe, unsigned int *left)
        __must_hold(&ctx->uring_lock)
{
        struct io_submit_link *link = &ctx->submit_state.link;
        int ret;

        ret = io_init_req(ctx, req, sqe, left);
        if (unlikely(ret))
                return io_submit_fail_init(sqe, req, ret);

        if (unlikely(ctx->bpf_filters)) {
                ret = io_uring_run_bpf_filters(ctx->bpf_filters, req);
                if (ret)
                        return io_submit_fail_init(sqe, req, ret);
        }

        trace_io_uring_submit_req(req);

        /*
         * If we already have a head request, queue this one for async
         * submittal once the head completes. If we don't have a head but
         * IOSQE_IO_LINK is set in the sqe, start a new head. This one will be
         * submitted sync once the chain is complete. If none of those
         * conditions are true (normal request), then just queue it.
         */
        if (unlikely(link->head)) {
                trace_io_uring_link(req, link->last);
                io_req_sqe_copy(req, IO_URING_F_INLINE);
                link->last->link = req;
                link->last = req;

                if (req->flags & IO_REQ_LINK_FLAGS)
                        return 0;
                /* last request of the link, flush it */
                req = link->head;
                link->head = NULL;
                if (req->flags & (REQ_F_FORCE_ASYNC | REQ_F_FAIL))
                        goto fallback;

        } else if (unlikely(req->flags & (IO_REQ_LINK_FLAGS |
                                          REQ_F_FORCE_ASYNC | REQ_F_FAIL))) {
                if (req->flags & IO_REQ_LINK_FLAGS) {
                        link->head = req;
                        link->last = req;
                } else {
fallback:
                        io_queue_sqe_fallback(req);
                }
                return 0;
        }

        io_queue_sqe(req, IO_URING_F_INLINE);
        return 0;
}

/*
 * Batched submission is done, ensure local IO is flushed out.
 */
static void io_submit_state_end(struct io_ring_ctx *ctx)
{
        struct io_submit_state *state = &ctx->submit_state;

        if (unlikely(state->link.head))
                io_queue_sqe_fallback(state->link.head);
        /* flush only after queuing links as they can generate completions */
        io_submit_flush_completions(ctx);
        if (state->plug_started)
                blk_finish_plug(&state->plug);
}

/*
 * Start submission side cache.
 */
static void io_submit_state_start(struct io_submit_state *state,
                                  unsigned int max_ios)
{
        state->plug_started = false;
        state->need_plug = max_ios > 2;
        state->submit_nr = max_ios;
        /* set only head, no need to init link_last in advance */
        state->link.head = NULL;
}

static void io_commit_sqring(struct io_ring_ctx *ctx)
{
        struct io_rings *rings = ctx->rings;

        if (ctx->flags & IORING_SETUP_SQ_REWIND) {
                ctx->cached_sq_head = 0;
        } else {
                /*
                 * Ensure any loads from the SQEs are done at this point,
                 * since once we write the new head, the application could
                 * write new data to them.
                 */
                smp_store_release(&rings->sq.head, ctx->cached_sq_head);
        }
}

/*
 * Fetch an sqe, if one is available. Note this returns a pointer to memory
 * that is mapped by userspace. This means that care needs to be taken to
 * ensure that reads are stable, as we cannot rely on userspace always
 * being a good citizen. If members of the sqe are validated and then later
 * used, it's important that those reads are done through READ_ONCE() to
 * prevent a re-load down the line.
 */
static bool io_get_sqe(struct io_ring_ctx *ctx, const struct io_uring_sqe **sqe)
{
        unsigned mask = ctx->sq_entries - 1;
        unsigned head = ctx->cached_sq_head++ & mask;

        if (static_branch_unlikely(&io_key_has_sqarray.key) &&
            (!(ctx->flags & IORING_SETUP_NO_SQARRAY))) {
                head = READ_ONCE(ctx->sq_array[head]);
                if (unlikely(head >= ctx->sq_entries)) {
                        WRITE_ONCE(ctx->rings->sq_dropped,
                                   READ_ONCE(ctx->rings->sq_dropped) + 1);
                        return false;
                }
                head = array_index_nospec(head, ctx->sq_entries);
        }

        /*
         * The cached sq head (or cq tail) serves two purposes:
         *
         * 1) allows us to batch the cost of updating the user visible
         *    head updates.
         * 2) allows the kernel side to track the head on its own, even
         *    though the application is the one updating it.
         */

        /* double index for 128-byte SQEs, twice as long */
        if (ctx->flags & IORING_SETUP_SQE128)
                head <<= 1;
        *sqe = &ctx->sq_sqes[head];
        return true;
}

int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr)
        __must_hold(&ctx->uring_lock)
{
        unsigned int entries;
        unsigned int left;
        int ret;

        if (ctx->flags & IORING_SETUP_SQ_REWIND)
                entries = ctx->sq_entries;
        else
                entries = __io_sqring_entries(ctx);

        entries = min(nr, entries);
        if (unlikely(!entries))
                return 0;

        ret = left = entries;
        io_get_task_refs(left);
        io_submit_state_start(&ctx->submit_state, left);

        do {
                const struct io_uring_sqe *sqe;
                struct io_kiocb *req;

                if (unlikely(!io_alloc_req(ctx, &req)))
                        break;
                if (unlikely(!io_get_sqe(ctx, &sqe))) {
                        io_req_add_to_cache(req, ctx);
                        break;
                }

                /*
                 * Continue submitting even for sqe failure if the
                 * ring was setup with IORING_SETUP_SUBMIT_ALL
                 */
                if (unlikely(io_submit_sqe(ctx, req, sqe, &left)) &&
                    !(ctx->flags & IORING_SETUP_SUBMIT_ALL)) {
                        left--;
                        break;
                }
        } while (--left);

        if (unlikely(left)) {
                ret -= left;
                /* try again if it submitted nothing and can't allocate a req */
                if (!ret && io_req_cache_empty(ctx))
                        ret = -EAGAIN;
                current->io_uring->cached_refs += left;
        }

        io_submit_state_end(ctx);
         /* Commit SQ ring head once we've consumed and submitted all SQEs */
        io_commit_sqring(ctx);
        return ret;
}

static void io_rings_free(struct io_ring_ctx *ctx)
{
        io_free_region(ctx->user, &ctx->sq_region);
        io_free_region(ctx->user, &ctx->ring_region);
        ctx->rings = NULL;
        RCU_INIT_POINTER(ctx->rings_rcu, NULL);
        ctx->sq_sqes = NULL;
}

static int rings_size(unsigned int flags, unsigned int sq_entries,
                      unsigned int cq_entries, struct io_rings_layout *rl)
{
        struct io_rings *rings;
        size_t sqe_size;
        size_t off;

        if (flags & IORING_SETUP_CQE_MIXED) {
                if (cq_entries < 2)
                        return -EOVERFLOW;
        }
        if (flags & IORING_SETUP_SQE_MIXED) {
                if (sq_entries < 2)
                        return -EOVERFLOW;
        }

        rl->sq_array_offset = SIZE_MAX;

        sqe_size = sizeof(struct io_uring_sqe);
        if (flags & IORING_SETUP_SQE128)
                sqe_size *= 2;

        rl->sq_size = array_size(sqe_size, sq_entries);
        if (rl->sq_size == SIZE_MAX)
                return -EOVERFLOW;

        off = struct_size(rings, cqes, cq_entries);
        if (flags & IORING_SETUP_CQE32)
                off = size_mul(off, 2);
        if (off == SIZE_MAX)
                return -EOVERFLOW;

#ifdef CONFIG_SMP
        off = ALIGN(off, SMP_CACHE_BYTES);
        if (off == 0)
                return -EOVERFLOW;
#endif

        if (!(flags & IORING_SETUP_NO_SQARRAY)) {
                size_t sq_array_size;

                rl->sq_array_offset = off;

                sq_array_size = array_size(sizeof(u32), sq_entries);
                off = size_add(off, sq_array_size);
                if (off == SIZE_MAX)
                        return -EOVERFLOW;
        }

        rl->rings_size = off;
        return 0;
}

static __cold void __io_req_caches_free(struct io_ring_ctx *ctx)
{
        struct io_kiocb *req;
        int nr = 0;

        while (!io_req_cache_empty(ctx)) {
                req = io_extract_req(ctx);
                io_poison_req(req);
                kmem_cache_free(req_cachep, req);
                nr++;
        }
        if (nr) {
                ctx->nr_req_allocated -= nr;
                percpu_ref_put_many(&ctx->refs, nr);
        }
}

static __cold void io_req_caches_free(struct io_ring_ctx *ctx)
{
        guard(mutex)(&ctx->uring_lock);
        __io_req_caches_free(ctx);
}

static __cold void io_ring_ctx_free(struct io_ring_ctx *ctx)
{
        io_sq_thread_finish(ctx);

        mutex_lock(&ctx->uring_lock);
        io_sqe_buffers_unregister(ctx);
        io_sqe_files_unregister(ctx);
        io_unregister_zcrx_ifqs(ctx);
        io_cqring_overflow_kill(ctx);
        io_eventfd_unregister(ctx);
        io_free_alloc_caches(ctx);
        io_destroy_buffers(ctx);
        io_free_region(ctx->user, &ctx->param_region);
        mutex_unlock(&ctx->uring_lock);
        if (ctx->sq_creds)
                put_cred(ctx->sq_creds);
        if (ctx->submitter_task)
                put_task_struct(ctx->submitter_task);

        WARN_ON_ONCE(!list_empty(&ctx->ltimeout_list));

        if (ctx->mm_account) {
                mmdrop(ctx->mm_account);
                ctx->mm_account = NULL;
        }
        io_rings_free(ctx);

        if (!(ctx->flags & IORING_SETUP_NO_SQARRAY))
                static_branch_slow_dec_deferred(&io_key_has_sqarray);

        percpu_ref_exit(&ctx->refs);
        free_uid(ctx->user);
        io_req_caches_free(ctx);

        if (ctx->restrictions.bpf_filters) {
                WARN_ON_ONCE(ctx->bpf_filters !=
                             ctx->restrictions.bpf_filters->filters);
        } else {
                WARN_ON_ONCE(ctx->bpf_filters);
        }
        io_put_bpf_filters(&ctx->restrictions);

        WARN_ON_ONCE(ctx->nr_req_allocated);

        if (ctx->hash_map)
                io_wq_put_hash(ctx->hash_map);
        io_napi_free(ctx);
        kvfree(ctx->cancel_table.hbs);
        xa_destroy(&ctx->io_bl_xa);
        kfree(ctx);
}

static __cold void io_activate_pollwq_cb(struct callback_head *cb)
{
        struct io_ring_ctx *ctx = container_of(cb, struct io_ring_ctx,
                                               poll_wq_task_work);

        mutex_lock(&ctx->uring_lock);
        ctx->poll_activated = true;
        mutex_unlock(&ctx->uring_lock);

        /*
         * Wake ups for some events between start of polling and activation
         * might've been lost due to loose synchronisation.
         */
        wake_up_all(&ctx->poll_wq);
        percpu_ref_put(&ctx->refs);
}

__cold void io_activate_pollwq(struct io_ring_ctx *ctx)
{
        spin_lock(&ctx->completion_lock);
        /* already activated or in progress */
        if (ctx->poll_activated || ctx->poll_wq_task_work.func)
                goto out;
        if (WARN_ON_ONCE(!ctx->task_complete))
                goto out;
        if (!ctx->submitter_task)
                goto out;
        /*
         * with ->submitter_task only the submitter task completes requests, we
         * only need to sync with it, which is done by injecting a tw
         */
        init_task_work(&ctx->poll_wq_task_work, io_activate_pollwq_cb);
        percpu_ref_get(&ctx->refs);
        if (task_work_add(ctx->submitter_task, &ctx->poll_wq_task_work, TWA_SIGNAL))
                percpu_ref_put(&ctx->refs);
out:
        spin_unlock(&ctx->completion_lock);
}

static __poll_t io_uring_poll(struct file *file, poll_table *wait)
{
        struct io_ring_ctx *ctx = file->private_data;
        __poll_t mask = 0;

        if (unlikely(!ctx->poll_activated))
                io_activate_pollwq(ctx);
        /*
         * provides mb() which pairs with barrier from wq_has_sleeper
         * call in io_commit_cqring
         */
        poll_wait(file, &ctx->poll_wq, wait);

        rcu_read_lock();

        if (!__io_sqring_full(ctx))
                mask |= EPOLLOUT | EPOLLWRNORM;

        /*
         * Don't flush cqring overflow list here, just do a simple check.
         * Otherwise there could possible be ABBA deadlock:
         *      CPU0                    CPU1
         *      ----                    ----
         * lock(&ctx->uring_lock);
         *                              lock(&ep->mtx);
         *                              lock(&ctx->uring_lock);
         * lock(&ep->mtx);
         *
         * Users may get EPOLLIN meanwhile seeing nothing in cqring, this
         * pushes them to do the flush.
         */

        if (__io_cqring_events_user(ctx) || io_has_work(ctx))
                mask |= EPOLLIN | EPOLLRDNORM;

        rcu_read_unlock();
        return mask;
}

struct io_tctx_exit {
        struct callback_head            task_work;
        struct completion               completion;
        struct io_ring_ctx              *ctx;
};

static __cold void io_tctx_exit_cb(struct callback_head *cb)
{
        struct io_uring_task *tctx = current->io_uring;
        struct io_tctx_exit *work;

        work = container_of(cb, struct io_tctx_exit, task_work);
        /*
         * When @in_cancel, we're in cancellation and it's racy to remove the
         * node. It'll be removed by the end of cancellation, just ignore it.
         * tctx can be NULL if the queueing of this task_work raced with
         * work cancelation off the exec path.
         */
        if (tctx && !atomic_read(&tctx->in_cancel))
                io_uring_del_tctx_node((unsigned long)work->ctx);
        complete(&work->completion);
}

static __cold void io_ring_exit_work(struct work_struct *work)
{
        struct io_ring_ctx *ctx = container_of(work, struct io_ring_ctx, exit_work);
        unsigned long timeout = jiffies + IO_URING_EXIT_WAIT_MAX;
        unsigned long interval = HZ / 20;
        struct io_tctx_exit exit;
        struct io_tctx_node *node;
        int ret;

        /*
         * If we're doing polled IO and end up having requests being
         * submitted async (out-of-line), then completions can come in while
         * we're waiting for refs to drop. We need to reap these manually,
         * as nobody else will be looking for them.
         */
        do {
                if (test_bit(IO_CHECK_CQ_OVERFLOW_BIT, &ctx->check_cq)) {
                        mutex_lock(&ctx->uring_lock);
                        io_cqring_overflow_kill(ctx);
                        mutex_unlock(&ctx->uring_lock);
                }

                /* The SQPOLL thread never reaches this path */
                do {
                        if (ctx->flags & IORING_SETUP_DEFER_TASKRUN)
                                io_move_task_work_from_local(ctx);
                        cond_resched();
                } while (io_uring_try_cancel_requests(ctx, NULL, true, false));

                if (ctx->sq_data) {
                        struct io_sq_data *sqd = ctx->sq_data;
                        struct task_struct *tsk;

                        io_sq_thread_park(sqd);
                        tsk = sqpoll_task_locked(sqd);
                        if (tsk && tsk->io_uring && tsk->io_uring->io_wq)
                                io_wq_cancel_cb(tsk->io_uring->io_wq,
                                                io_cancel_ctx_cb, ctx, true);
                        io_sq_thread_unpark(sqd);
                }

                io_req_caches_free(ctx);

                if (WARN_ON_ONCE(time_after(jiffies, timeout))) {
                        /* there is little hope left, don't run it too often */
                        interval = HZ * 60;
                }
                /*
                 * This is really an uninterruptible wait, as it has to be
                 * complete. But it's also run from a kworker, which doesn't
                 * take signals, so it's fine to make it interruptible. This
                 * avoids scenarios where we knowingly can wait much longer
                 * on completions, for example if someone does a SIGSTOP on
                 * a task that needs to finish task_work to make this loop
                 * complete. That's a synthetic situation that should not
                 * cause a stuck task backtrace, and hence a potential panic
                 * on stuck tasks if that is enabled.
                 */
        } while (!wait_for_completion_interruptible_timeout(&ctx->ref_comp, interval));

        init_completion(&exit.completion);
        init_task_work(&exit.task_work, io_tctx_exit_cb);
        exit.ctx = ctx;

        mutex_lock(&ctx->uring_lock);
        mutex_lock(&ctx->tctx_lock);
        while (!list_empty(&ctx->tctx_list)) {
                WARN_ON_ONCE(time_after(jiffies, timeout));

                node = list_first_entry(&ctx->tctx_list, struct io_tctx_node,
                                        ctx_node);
                /* don't spin on a single task if cancellation failed */
                list_rotate_left(&ctx->tctx_list);
                ret = task_work_add(node->task, &exit.task_work, TWA_SIGNAL);
                if (WARN_ON_ONCE(ret))
                        continue;

                mutex_unlock(&ctx->tctx_lock);
                mutex_unlock(&ctx->uring_lock);
                /*
                 * See comment above for
                 * wait_for_completion_interruptible_timeout() on why this
                 * wait is marked as interruptible.
                 */
                wait_for_completion_interruptible(&exit.completion);
                mutex_lock(&ctx->uring_lock);
                mutex_lock(&ctx->tctx_lock);
        }
        mutex_unlock(&ctx->tctx_lock);
        mutex_unlock(&ctx->uring_lock);
        spin_lock(&ctx->completion_lock);
        spin_unlock(&ctx->completion_lock);

        /* pairs with RCU read section in io_req_local_work_add() */
        if (ctx->flags & IORING_SETUP_DEFER_TASKRUN)
                synchronize_rcu();

        io_ring_ctx_free(ctx);
}

static __cold void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx)
{
        unsigned long index;
        struct cred *creds;

        mutex_lock(&ctx->uring_lock);
        percpu_ref_kill(&ctx->refs);
        xa_for_each(&ctx->personalities, index, creds)
                io_unregister_personality(ctx, index);
        mutex_unlock(&ctx->uring_lock);

        flush_delayed_work(&ctx->fallback_work);

        INIT_WORK(&ctx->exit_work, io_ring_exit_work);
        /*
         * Use system_dfl_wq to avoid spawning tons of event kworkers
         * if we're exiting a ton of rings at the same time. It just adds
         * noise and overhead, there's no discernable change in runtime
         * over using system_percpu_wq.
         */
        queue_work(iou_wq, &ctx->exit_work);
}

static int io_uring_release(struct inode *inode, struct file *file)
{
        struct io_ring_ctx *ctx = file->private_data;

        file->private_data = NULL;
        io_ring_ctx_wait_and_kill(ctx);
        return 0;
}

static struct io_uring_reg_wait *io_get_ext_arg_reg(struct io_ring_ctx *ctx,
                        const struct io_uring_getevents_arg __user *uarg)
{
        unsigned long size = sizeof(struct io_uring_reg_wait);
        unsigned long offset = (uintptr_t)uarg;
        unsigned long end;

        if (unlikely(offset % sizeof(long)))
                return ERR_PTR(-EFAULT);

        /* also protects from NULL ->cq_wait_arg as the size would be 0 */
        if (unlikely(check_add_overflow(offset, size, &end) ||
                     end > ctx->cq_wait_size))
                return ERR_PTR(-EFAULT);

        offset = array_index_nospec(offset, ctx->cq_wait_size - size);
        return ctx->cq_wait_arg + offset;
}

static int io_validate_ext_arg(struct io_ring_ctx *ctx, unsigned flags,
                               const void __user *argp, size_t argsz)
{
        struct io_uring_getevents_arg arg;

        if (!(flags & IORING_ENTER_EXT_ARG))
                return 0;
        if (flags & IORING_ENTER_EXT_ARG_REG)
                return -EINVAL;
        if (argsz != sizeof(arg))
                return -EINVAL;
        if (copy_from_user(&arg, argp, sizeof(arg)))
                return -EFAULT;
        return 0;
}

static int io_get_ext_arg(struct io_ring_ctx *ctx, unsigned flags,
                          const void __user *argp, struct ext_arg *ext_arg)
{
        const struct io_uring_getevents_arg __user *uarg = argp;
        struct io_uring_getevents_arg arg;

        ext_arg->iowait = !(flags & IORING_ENTER_NO_IOWAIT);

        /*
         * If EXT_ARG isn't set, then we have no timespec and the argp pointer
         * is just a pointer to the sigset_t.
         */
        if (!(flags & IORING_ENTER_EXT_ARG)) {
                ext_arg->sig = (const sigset_t __user *) argp;
                return 0;
        }

        if (flags & IORING_ENTER_EXT_ARG_REG) {
                struct io_uring_reg_wait *w;

                if (ext_arg->argsz != sizeof(struct io_uring_reg_wait))
                        return -EINVAL;
                w = io_get_ext_arg_reg(ctx, argp);
                if (IS_ERR(w))
                        return PTR_ERR(w);

                if (w->flags & ~IORING_REG_WAIT_TS)
                        return -EINVAL;
                ext_arg->min_time = READ_ONCE(w->min_wait_usec) * NSEC_PER_USEC;
                ext_arg->sig = u64_to_user_ptr(READ_ONCE(w->sigmask));
                ext_arg->argsz = READ_ONCE(w->sigmask_sz);
                if (w->flags & IORING_REG_WAIT_TS) {
                        ext_arg->ts.tv_sec = READ_ONCE(w->ts.tv_sec);
                        ext_arg->ts.tv_nsec = READ_ONCE(w->ts.tv_nsec);
                        ext_arg->ts_set = true;
                }
                return 0;
        }

        /*
         * EXT_ARG is set - ensure we agree on the size of it and copy in our
         * timespec and sigset_t pointers if good.
         */
        if (ext_arg->argsz != sizeof(arg))
                return -EINVAL;
#ifdef CONFIG_64BIT
        if (!user_access_begin(uarg, sizeof(*uarg)))
                return -EFAULT;
        unsafe_get_user(arg.sigmask, &uarg->sigmask, uaccess_end);
        unsafe_get_user(arg.sigmask_sz, &uarg->sigmask_sz, uaccess_end);
        unsafe_get_user(arg.min_wait_usec, &uarg->min_wait_usec, uaccess_end);
        unsafe_get_user(arg.ts, &uarg->ts, uaccess_end);
        user_access_end();
#else
        if (copy_from_user(&arg, uarg, sizeof(arg)))
                return -EFAULT;
#endif
        ext_arg->min_time = arg.min_wait_usec * NSEC_PER_USEC;
        ext_arg->sig = u64_to_user_ptr(arg.sigmask);
        ext_arg->argsz = arg.sigmask_sz;
        if (arg.ts) {
                if (get_timespec64(&ext_arg->ts, u64_to_user_ptr(arg.ts)))
                        return -EFAULT;
                ext_arg->ts_set = true;
        }
        return 0;
#ifdef CONFIG_64BIT
uaccess_end:
        user_access_end();
        return -EFAULT;
#endif
}

SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
                u32, min_complete, u32, flags, const void __user *, argp,
                size_t, argsz)
{
        struct io_ring_ctx *ctx;
        struct file *file;
        long ret;

        if (unlikely(flags & ~IORING_ENTER_FLAGS))
                return -EINVAL;

        /*
         * Ring fd has been registered via IORING_REGISTER_RING_FDS, we
         * need only dereference our task private array to find it.
         */
        if (flags & IORING_ENTER_REGISTERED_RING) {
                struct io_uring_task *tctx = current->io_uring;

                if (unlikely(!tctx || fd >= IO_RINGFD_REG_MAX))
                        return -EINVAL;
                fd = array_index_nospec(fd, IO_RINGFD_REG_MAX);
                file = tctx->registered_rings[fd];
                if (unlikely(!file))
                        return -EBADF;
        } else {
                file = fget(fd);
                if (unlikely(!file))
                        return -EBADF;
                ret = -EOPNOTSUPP;
                if (unlikely(!io_is_uring_fops(file)))
                        goto out;
        }

        ctx = file->private_data;
        ret = -EBADFD;
        /*
         * Keep IORING_SETUP_R_DISABLED check before submitter_task load
         * in io_uring_add_tctx_node() -> __io_uring_add_tctx_node_from_submit()
         */
        if (unlikely(smp_load_acquire(&ctx->flags) & IORING_SETUP_R_DISABLED))
                goto out;

        /*
         * For SQ polling, the thread will do all submissions and completions.
         * Just return the requested submit count, and wake the thread if
         * we were asked to.
         */
        ret = 0;
        if (ctx->flags & IORING_SETUP_SQPOLL) {
                if (unlikely(ctx->sq_data->thread == NULL)) {
                        ret = -EOWNERDEAD;
                        goto out;
                }
                if (flags & IORING_ENTER_SQ_WAKEUP)
                        wake_up(&ctx->sq_data->wait);
                if (flags & IORING_ENTER_SQ_WAIT)
                        io_sqpoll_wait_sq(ctx);

                ret = to_submit;
        } else if (to_submit) {
                ret = io_uring_add_tctx_node(ctx);
                if (unlikely(ret))
                        goto out;

                mutex_lock(&ctx->uring_lock);
                ret = io_submit_sqes(ctx, to_submit);
                if (ret != to_submit) {
                        mutex_unlock(&ctx->uring_lock);
                        goto out;
                }
                if (flags & IORING_ENTER_GETEVENTS) {
                        if (ctx->syscall_iopoll)
                                goto iopoll_locked;
                        /*
                         * Ignore errors, we'll soon call io_cqring_wait() and
                         * it should handle ownership problems if any.
                         */
                        if (ctx->flags & IORING_SETUP_DEFER_TASKRUN)
                                (void)io_run_local_work_locked(ctx, min_complete);
                }
                mutex_unlock(&ctx->uring_lock);
        }

        if (flags & IORING_ENTER_GETEVENTS) {
                int ret2;

                if (ctx->syscall_iopoll) {
                        /*
                         * We disallow the app entering submit/complete with
                         * polling, but we still need to lock the ring to
                         * prevent racing with polled issue that got punted to
                         * a workqueue.
                         */
                        mutex_lock(&ctx->uring_lock);
iopoll_locked:
                        ret2 = io_validate_ext_arg(ctx, flags, argp, argsz);
                        if (likely(!ret2))
                                ret2 = io_iopoll_check(ctx, min_complete);
                        mutex_unlock(&ctx->uring_lock);
                } else {
                        struct ext_arg ext_arg = { .argsz = argsz };

                        ret2 = io_get_ext_arg(ctx, flags, argp, &ext_arg);
                        if (likely(!ret2))
                                ret2 = io_cqring_wait(ctx, min_complete, flags,
                                                      &ext_arg);
                }

                if (!ret) {
                        ret = ret2;

                        /*
                         * EBADR indicates that one or more CQE were dropped.
                         * Once the user has been informed we can clear the bit
                         * as they are obviously ok with those drops.
                         */
                        if (unlikely(ret2 == -EBADR))
                                clear_bit(IO_CHECK_CQ_DROPPED_BIT,
                                          &ctx->check_cq);
                }
        }
out:
        if (!(flags & IORING_ENTER_REGISTERED_RING))
                fput(file);
        return ret;
}

static const struct file_operations io_uring_fops = {
        .release        = io_uring_release,
        .mmap           = io_uring_mmap,
        .get_unmapped_area = io_uring_get_unmapped_area,
#ifndef CONFIG_MMU
        .mmap_capabilities = io_uring_nommu_mmap_capabilities,
#endif
        .poll           = io_uring_poll,
#ifdef CONFIG_PROC_FS
        .show_fdinfo    = io_uring_show_fdinfo,
#endif
};

bool io_is_uring_fops(struct file *file)
{
        return file->f_op == &io_uring_fops;
}

static __cold int io_allocate_scq_urings(struct io_ring_ctx *ctx,
                                         struct io_ctx_config *config)
{
        struct io_uring_params *p = &config->p;
        struct io_rings_layout *rl = &config->layout;
        struct io_uring_region_desc rd;
        struct io_rings *rings;
        int ret;

        /* make sure these are sane, as we already accounted them */
        ctx->sq_entries = p->sq_entries;
        ctx->cq_entries = p->cq_entries;

        memset(&rd, 0, sizeof(rd));
        rd.size = PAGE_ALIGN(rl->rings_size);
        if (ctx->flags & IORING_SETUP_NO_MMAP) {
                rd.user_addr = p->cq_off.user_addr;
                rd.flags |= IORING_MEM_REGION_TYPE_USER;
        }
        ret = io_create_region(ctx, &ctx->ring_region, &rd, IORING_OFF_CQ_RING);
        if (ret)
                return ret;
        ctx->rings = rings = io_region_get_ptr(&ctx->ring_region);
        rcu_assign_pointer(ctx->rings_rcu, rings);
        if (!(ctx->flags & IORING_SETUP_NO_SQARRAY))
                ctx->sq_array = (u32 *)((char *)rings + rl->sq_array_offset);

        memset(&rd, 0, sizeof(rd));
        rd.size = PAGE_ALIGN(rl->sq_size);
        if (ctx->flags & IORING_SETUP_NO_MMAP) {
                rd.user_addr = p->sq_off.user_addr;
                rd.flags |= IORING_MEM_REGION_TYPE_USER;
        }
        ret = io_create_region(ctx, &ctx->sq_region, &rd, IORING_OFF_SQES);
        if (ret) {
                io_rings_free(ctx);
                return ret;
        }
        ctx->sq_sqes = io_region_get_ptr(&ctx->sq_region);

        memset(rings, 0, sizeof(*rings));
        WRITE_ONCE(rings->sq_ring_mask, ctx->sq_entries - 1);
        WRITE_ONCE(rings->cq_ring_mask, ctx->cq_entries - 1);
        WRITE_ONCE(rings->sq_ring_entries, ctx->sq_entries);
        WRITE_ONCE(rings->cq_ring_entries, ctx->cq_entries);
        return 0;
}

static int io_uring_install_fd(struct file *file)
{
        int fd;

        fd = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
        if (fd < 0)
                return fd;
        fd_install(fd, file);
        return fd;
}

/*
 * Allocate an anonymous fd, this is what constitutes the application
 * visible backing of an io_uring instance. The application mmaps this
 * fd to gain access to the SQ/CQ ring details.
 */
static struct file *io_uring_get_file(struct io_ring_ctx *ctx)
{
        /* Create a new inode so that the LSM can block the creation.  */
        return anon_inode_create_getfile("[io_uring]", &io_uring_fops, ctx,
                                         O_RDWR | O_CLOEXEC, NULL);
}

static int io_uring_sanitise_params(struct io_uring_params *p)
{
        unsigned flags = p->flags;

        if (flags & ~IORING_SETUP_FLAGS)
                return -EINVAL;

        if (flags & IORING_SETUP_SQ_REWIND) {
                if ((flags & IORING_SETUP_SQPOLL) ||
                    !(flags & IORING_SETUP_NO_SQARRAY))
                        return -EINVAL;
        }

        /* There is no way to mmap rings without a real fd */
        if ((flags & IORING_SETUP_REGISTERED_FD_ONLY) &&
            !(flags & IORING_SETUP_NO_MMAP))
                return -EINVAL;

        if (flags & IORING_SETUP_SQPOLL) {
                /* IPI related flags don't make sense with SQPOLL */
                if (flags & (IORING_SETUP_COOP_TASKRUN |
                             IORING_SETUP_TASKRUN_FLAG |
                             IORING_SETUP_DEFER_TASKRUN))
                        return -EINVAL;
        }

        if (flags & IORING_SETUP_TASKRUN_FLAG) {
                if (!(flags & (IORING_SETUP_COOP_TASKRUN |
                               IORING_SETUP_DEFER_TASKRUN)))
                        return -EINVAL;
        }

        /* HYBRID_IOPOLL only valid with IOPOLL */
        if ((flags & IORING_SETUP_HYBRID_IOPOLL) && !(flags & IORING_SETUP_IOPOLL))
                return -EINVAL;

        /*
         * For DEFER_TASKRUN we require the completion task to be the same as
         * the submission task. This implies that there is only one submitter.
         */
        if ((flags & IORING_SETUP_DEFER_TASKRUN) &&
            !(flags & IORING_SETUP_SINGLE_ISSUER))
                return -EINVAL;

        /*
         * Nonsensical to ask for CQE32 and mixed CQE support, it's not
         * supported to post 16b CQEs on a ring setup with CQE32.
         */
        if ((flags & (IORING_SETUP_CQE32|IORING_SETUP_CQE_MIXED)) ==
            (IORING_SETUP_CQE32|IORING_SETUP_CQE_MIXED))
                return -EINVAL;
        /*
         * Nonsensical to ask for SQE128 and mixed SQE support, it's not
         * supported to post 64b SQEs on a ring setup with SQE128.
         */
        if ((flags & (IORING_SETUP_SQE128|IORING_SETUP_SQE_MIXED)) ==
            (IORING_SETUP_SQE128|IORING_SETUP_SQE_MIXED))
                return -EINVAL;

        return 0;
}

static int io_uring_fill_params(struct io_uring_params *p)
{
        unsigned entries = p->sq_entries;

        if (!entries)
                return -EINVAL;
        if (entries > IORING_MAX_ENTRIES) {
                if (!(p->flags & IORING_SETUP_CLAMP))
                        return -EINVAL;
                entries = IORING_MAX_ENTRIES;
        }

        /*
         * Use twice as many entries for the CQ ring. It's possible for the
         * application to drive a higher depth than the size of the SQ ring,
         * since the sqes are only used at submission time. This allows for
         * some flexibility in overcommitting a bit. If the application has
         * set IORING_SETUP_CQSIZE, it will have passed in the desired number
         * of CQ ring entries manually.
         */
        p->sq_entries = roundup_pow_of_two(entries);
        if (p->flags & IORING_SETUP_CQSIZE) {
                /*
                 * If IORING_SETUP_CQSIZE is set, we do the same roundup
                 * to a power-of-two, if it isn't already. We do NOT impose
                 * any cq vs sq ring sizing.
                 */
                if (!p->cq_entries)
                        return -EINVAL;
                if (p->cq_entries > IORING_MAX_CQ_ENTRIES) {
                        if (!(p->flags & IORING_SETUP_CLAMP))
                                return -EINVAL;
                        p->cq_entries = IORING_MAX_CQ_ENTRIES;
                }
                p->cq_entries = roundup_pow_of_two(p->cq_entries);
                if (p->cq_entries < p->sq_entries)
                        return -EINVAL;
        } else {
                p->cq_entries = 2 * p->sq_entries;
        }

        return 0;
}

int io_prepare_config(struct io_ctx_config *config)
{
        struct io_uring_params *p = &config->p;
        int ret;

        ret = io_uring_sanitise_params(p);
        if (ret)
                return ret;

        ret = io_uring_fill_params(p);
        if (ret)
                return ret;

        ret = rings_size(p->flags, p->sq_entries, p->cq_entries,
                         &config->layout);
        if (ret)
                return ret;

        p->sq_off.head = offsetof(struct io_rings, sq.head);
        p->sq_off.tail = offsetof(struct io_rings, sq.tail);
        p->sq_off.ring_mask = offsetof(struct io_rings, sq_ring_mask);
        p->sq_off.ring_entries = offsetof(struct io_rings, sq_ring_entries);
        p->sq_off.flags = offsetof(struct io_rings, sq_flags);
        p->sq_off.dropped = offsetof(struct io_rings, sq_dropped);
        p->sq_off.resv1 = 0;
        if (!(p->flags & IORING_SETUP_NO_MMAP))
                p->sq_off.user_addr = 0;

        p->cq_off.head = offsetof(struct io_rings, cq.head);
        p->cq_off.tail = offsetof(struct io_rings, cq.tail);
        p->cq_off.ring_mask = offsetof(struct io_rings, cq_ring_mask);
        p->cq_off.ring_entries = offsetof(struct io_rings, cq_ring_entries);
        p->cq_off.overflow = offsetof(struct io_rings, cq_overflow);
        p->cq_off.cqes = offsetof(struct io_rings, cqes);
        p->cq_off.flags = offsetof(struct io_rings, cq_flags);
        p->cq_off.resv1 = 0;
        if (!(p->flags & IORING_SETUP_NO_MMAP))
                p->cq_off.user_addr = 0;
        if (!(p->flags & IORING_SETUP_NO_SQARRAY))
                p->sq_off.array = config->layout.sq_array_offset;

        return 0;
}

void io_restriction_clone(struct io_restriction *dst, struct io_restriction *src)
{
        memcpy(&dst->register_op, &src->register_op, sizeof(dst->register_op));
        memcpy(&dst->sqe_op, &src->sqe_op, sizeof(dst->sqe_op));
        dst->sqe_flags_allowed = src->sqe_flags_allowed;
        dst->sqe_flags_required = src->sqe_flags_required;
        dst->op_registered = src->op_registered;
        dst->reg_registered = src->reg_registered;

        io_bpf_filter_clone(dst, src);
}

static void io_ctx_restriction_clone(struct io_ring_ctx *ctx,
                                     struct io_restriction *src)
{
        struct io_restriction *dst = &ctx->restrictions;

        io_restriction_clone(dst, src);
        if (dst->bpf_filters)
                WRITE_ONCE(ctx->bpf_filters, dst->bpf_filters->filters);
        if (dst->op_registered)
                ctx->op_restricted = 1;
        if (dst->reg_registered)
                ctx->reg_restricted = 1;
}

static __cold int io_uring_create(struct io_ctx_config *config)
{
        struct io_uring_params *p = &config->p;
        struct io_ring_ctx *ctx;
        struct io_uring_task *tctx;
        struct file *file;
        int ret;

        ret = io_prepare_config(config);
        if (ret)
                return ret;

        ctx = io_ring_ctx_alloc(p);
        if (!ctx)
                return -ENOMEM;

        ctx->clockid = CLOCK_MONOTONIC;
        ctx->clock_offset = 0;

        if (!(ctx->flags & IORING_SETUP_NO_SQARRAY))
                static_branch_deferred_inc(&io_key_has_sqarray);

        if ((ctx->flags & IORING_SETUP_DEFER_TASKRUN) &&
            !(ctx->flags & IORING_SETUP_IOPOLL))
                ctx->task_complete = true;

        if (ctx->task_complete || (ctx->flags & IORING_SETUP_IOPOLL))
                ctx->lockless_cq = true;

        /*
         * lazy poll_wq activation relies on ->task_complete for synchronisation
         * purposes, see io_activate_pollwq()
         */
        if (!ctx->task_complete)
                ctx->poll_activated = true;

        /*
         * When SETUP_IOPOLL and SETUP_SQPOLL are both enabled, user
         * space applications don't need to do io completion events
         * polling again, they can rely on io_sq_thread to do polling
         * work, which can reduce cpu usage and uring_lock contention.
         */
        if (ctx->flags & IORING_SETUP_IOPOLL &&
            !(ctx->flags & IORING_SETUP_SQPOLL))
                ctx->syscall_iopoll = 1;

        ctx->compat = in_compat_syscall();
        if (!ns_capable_noaudit(&init_user_ns, CAP_IPC_LOCK))
                ctx->user = get_uid(current_user());

        /*
         * For SQPOLL, we just need a wakeup, always. For !SQPOLL, if
         * COOP_TASKRUN is set, then IPIs are never needed by the app.
         */
        if (ctx->flags & (IORING_SETUP_SQPOLL|IORING_SETUP_COOP_TASKRUN))
                ctx->notify_method = TWA_SIGNAL_NO_IPI;
        else
                ctx->notify_method = TWA_SIGNAL;

        /*
         * If the current task has restrictions enabled, then copy them to
         * our newly created ring and mark it as registered.
         */
        if (current->io_uring_restrict)
                io_ctx_restriction_clone(ctx, current->io_uring_restrict);

        /*
         * This is just grabbed for accounting purposes. When a process exits,
         * the mm is exited and dropped before the files, hence we need to hang
         * on to this mm purely for the purposes of being able to unaccount
         * memory (locked/pinned vm). It's not used for anything else.
         */
        mmgrab(current->mm);
        ctx->mm_account = current->mm;

        ret = io_allocate_scq_urings(ctx, config);
        if (ret)
                goto err;

        ret = io_sq_offload_create(ctx, p);
        if (ret)
                goto err;

        p->features = IORING_FEAT_FLAGS;

        if (copy_to_user(config->uptr, p, sizeof(*p))) {
                ret = -EFAULT;
                goto err;
        }

        if (ctx->flags & IORING_SETUP_SINGLE_ISSUER
            && !(ctx->flags & IORING_SETUP_R_DISABLED))
                ctx->submitter_task = get_task_struct(current);

        file = io_uring_get_file(ctx);
        if (IS_ERR(file)) {
                ret = PTR_ERR(file);
                goto err;
        }

        ret = __io_uring_add_tctx_node(ctx);
        if (ret)
                goto err_fput;
        tctx = current->io_uring;

        /*
         * Install ring fd as the very last thing, so we don't risk someone
         * having closed it before we finish setup
         */
        if (p->flags & IORING_SETUP_REGISTERED_FD_ONLY)
                ret = io_ring_add_registered_file(tctx, file, 0, IO_RINGFD_REG_MAX);
        else
                ret = io_uring_install_fd(file);
        if (ret < 0)
                goto err_fput;

        trace_io_uring_create(ret, ctx, p->sq_entries, p->cq_entries, p->flags);
        return ret;
err:
        io_ring_ctx_wait_and_kill(ctx);
        return ret;
err_fput:
        fput(file);
        return ret;
}

/*
 * Sets up an aio uring context, and returns the fd. Applications asks for a
 * ring size, we return the actual sq/cq ring sizes (among other things) in the
 * params structure passed in.
 */
static long io_uring_setup(u32 entries, struct io_uring_params __user *params)
{
        struct io_ctx_config config;

        memset(&config, 0, sizeof(config));

        if (copy_from_user(&config.p, params, sizeof(config.p)))
                return -EFAULT;

        if (!mem_is_zero(&config.p.resv, sizeof(config.p.resv)))
                return -EINVAL;

        config.p.sq_entries = entries;
        config.uptr = params;
        return io_uring_create(&config);
}

static inline int io_uring_allowed(void)
{
        int disabled = READ_ONCE(sysctl_io_uring_disabled);
        kgid_t io_uring_group;

        if (disabled == 2)
                return -EPERM;

        if (disabled == 0 || capable(CAP_SYS_ADMIN))
                goto allowed_lsm;

        io_uring_group = make_kgid(&init_user_ns, sysctl_io_uring_group);
        if (!gid_valid(io_uring_group))
                return -EPERM;

        if (!in_group_p(io_uring_group))
                return -EPERM;

allowed_lsm:
        return security_uring_allowed();
}

SYSCALL_DEFINE2(io_uring_setup, u32, entries,
                struct io_uring_params __user *, params)
{
        int ret;

        ret = io_uring_allowed();
        if (ret)
                return ret;

        return io_uring_setup(entries, params);
}

static int __init io_uring_init(void)
{
        struct kmem_cache_args kmem_args = {
                .useroffset = offsetof(struct io_kiocb, cmd.data),
                .usersize = sizeof_field(struct io_kiocb, cmd.data),
                .freeptr_offset = offsetof(struct io_kiocb, work),
                .use_freeptr_offset = true,
        };

#define __BUILD_BUG_VERIFY_OFFSET_SIZE(stype, eoffset, esize, ename) do { \
        BUILD_BUG_ON(offsetof(stype, ename) != eoffset); \
        BUILD_BUG_ON(sizeof_field(stype, ename) != esize); \
} while (0)

#define BUILD_BUG_SQE_ELEM(eoffset, etype, ename) \
        __BUILD_BUG_VERIFY_OFFSET_SIZE(struct io_uring_sqe, eoffset, sizeof(etype), ename)
#define BUILD_BUG_SQE_ELEM_SIZE(eoffset, esize, ename) \
        __BUILD_BUG_VERIFY_OFFSET_SIZE(struct io_uring_sqe, eoffset, esize, ename)
        BUILD_BUG_ON(sizeof(struct io_uring_sqe) != 64);
        BUILD_BUG_SQE_ELEM(0,  __u8,   opcode);
        BUILD_BUG_SQE_ELEM(1,  __u8,   flags);
        BUILD_BUG_SQE_ELEM(2,  __u16,  ioprio);
        BUILD_BUG_SQE_ELEM(4,  __s32,  fd);
        BUILD_BUG_SQE_ELEM(8,  __u64,  off);
        BUILD_BUG_SQE_ELEM(8,  __u64,  addr2);
        BUILD_BUG_SQE_ELEM(8,  __u32,  cmd_op);
        BUILD_BUG_SQE_ELEM(12, __u32, __pad1);
        BUILD_BUG_SQE_ELEM(16, __u64,  addr);
        BUILD_BUG_SQE_ELEM(16, __u64,  splice_off_in);
        BUILD_BUG_SQE_ELEM(24, __u32,  len);
        BUILD_BUG_SQE_ELEM(28,     __kernel_rwf_t, rw_flags);
        BUILD_BUG_SQE_ELEM(28, /* compat */   int, rw_flags);
        BUILD_BUG_SQE_ELEM(28, /* compat */ __u32, rw_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  fsync_flags);
        BUILD_BUG_SQE_ELEM(28, /* compat */ __u16,  poll_events);
        BUILD_BUG_SQE_ELEM(28, __u32,  poll32_events);
        BUILD_BUG_SQE_ELEM(28, __u32,  sync_range_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  msg_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  timeout_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  accept_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  cancel_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  open_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  statx_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  fadvise_advice);
        BUILD_BUG_SQE_ELEM(28, __u32,  splice_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  rename_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  unlink_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  hardlink_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  xattr_flags);
        BUILD_BUG_SQE_ELEM(28, __u32,  msg_ring_flags);
        BUILD_BUG_SQE_ELEM(32, __u64,  user_data);
        BUILD_BUG_SQE_ELEM(40, __u16,  buf_index);
        BUILD_BUG_SQE_ELEM(40, __u16,  buf_group);
        BUILD_BUG_SQE_ELEM(42, __u16,  personality);
        BUILD_BUG_SQE_ELEM(44, __s32,  splice_fd_in);
        BUILD_BUG_SQE_ELEM(44, __u32,  file_index);
        BUILD_BUG_SQE_ELEM(44, __u16,  addr_len);
        BUILD_BUG_SQE_ELEM(44, __u8,   write_stream);
        BUILD_BUG_SQE_ELEM(45, __u8,   __pad4[0]);
        BUILD_BUG_SQE_ELEM(46, __u16,  __pad3[0]);
        BUILD_BUG_SQE_ELEM(48, __u64,  addr3);
        BUILD_BUG_SQE_ELEM_SIZE(48, 0, cmd);
        BUILD_BUG_SQE_ELEM(48, __u64, attr_ptr);
        BUILD_BUG_SQE_ELEM(56, __u64, attr_type_mask);
        BUILD_BUG_SQE_ELEM(56, __u64,  __pad2);

        BUILD_BUG_ON(sizeof(struct io_uring_files_update) !=
                     sizeof(struct io_uring_rsrc_update));
        BUILD_BUG_ON(sizeof(struct io_uring_rsrc_update) >
                     sizeof(struct io_uring_rsrc_update2));

        /* ->buf_index is u16 */
        BUILD_BUG_ON(offsetof(struct io_uring_buf_ring, bufs) != 0);
        BUILD_BUG_ON(offsetof(struct io_uring_buf, resv) !=
                     offsetof(struct io_uring_buf_ring, tail));

        /* should fit into one byte */
        BUILD_BUG_ON(SQE_VALID_FLAGS >= (1 << 8));
        BUILD_BUG_ON(SQE_COMMON_FLAGS >= (1 << 8));
        BUILD_BUG_ON((SQE_VALID_FLAGS | SQE_COMMON_FLAGS) != SQE_VALID_FLAGS);

        BUILD_BUG_ON(__REQ_F_LAST_BIT > 8 * sizeof_field(struct io_kiocb, flags));

        BUILD_BUG_ON(sizeof(atomic_t) != sizeof(u32));

        /* top 8bits are for internal use */
        BUILD_BUG_ON((IORING_URING_CMD_MASK & 0xff000000) != 0);

        io_uring_optable_init();

        /* imu->dir is u8 */
        BUILD_BUG_ON((IO_IMU_DEST | IO_IMU_SOURCE) > U8_MAX);

        /*
         * Allow user copy in the per-command field, which starts after the
         * file in io_kiocb and until the opcode field. The openat2 handling
         * requires copying in user memory into the io_kiocb object in that
         * range, and HARDENED_USERCOPY will complain if we haven't
         * correctly annotated this range.
         */
        req_cachep = kmem_cache_create("io_kiocb", sizeof(struct io_kiocb), &kmem_args,
                                SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT |
                                SLAB_TYPESAFE_BY_RCU);

        iou_wq = alloc_workqueue("iou_exit", WQ_UNBOUND, 64);
        BUG_ON(!iou_wq);

#ifdef CONFIG_SYSCTL
        register_sysctl_init("kernel", kernel_io_uring_disabled_table);
#endif

        return 0;
};
__initcall(io_uring_init);