OSCL-LXR linux-6.0.1/​io_uring/​io_uring.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // 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.dk/liburing
  *
  * 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/init.h>
 #include <linux/errno.h>
 #include <linux/syscalls.h>
 #include <net/compat.h>
 #include <linux/refcount.h>
 #include <linux/uio.h>
 #include <linux/bits.h>
 
 #include <linux/sched/signal.h>
 #include <linux/fs.h>
 #include <linux/file.h>
 #include <linux/fdtable.h>
 #include <linux/mm.h>
 #include <linux/mman.h>
 #include <linux/percpu.h>
 #include <linux/slab.h>
 #include <linux/bvec.h>
 #include <linux/net.h>
 #include <net/sock.h>
 #include <net/af_unix.h>
 #include <net/scm.h>
 #include <linux/anon_inodes.h>
 #include <linux/sched/mm.h>
 #include <linux/uaccess.h>
 #include <linux/nospec.h>
 #include <linux/highmem.h>
 #include <linux/fsnotify.h>
 #include <linux/fadvise.h>
 #include <linux/task_work.h>
 #include <linux/io_uring.h>
 #include <linux/audit.h>
 #include <linux/security.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/io_uring.h>
 
 #include <uapi/linux/io_uring.h>
 
 #include "io-wq.h"
 
 #include "io_uring.h"
 #include "opdef.h"
 #include "refs.h"
 #include "tctx.h"
 #include "sqpoll.h"
 #include "fdinfo.h"
 #include "kbuf.h"
 #include "rsrc.h"
 #include "cancel.h"
 #include "net.h"
 #include "notif.h"
 
 #include "timeout.h"
 #include "poll.h"
 #include "alloc_cache.h"
 
 #define IORING_MAX_ENTRIES  32768
 #define IORING_MAX_CQ_ENTRIES   (2 * IORING_MAX_ENTRIES)
 
 #define IORING_MAX_RESTRICTIONS (IORING_RESTRICTION_LAST + \
                  IORING_REGISTER_LAST + IORING_OP_LAST)
 
 #define SQE_COMMON_FLAGS (IOSQE_FIXED_FILE | IOSQE_IO_LINK | \
               IOSQE_IO_HARDLINK | IOSQE_ASYNC)
 
 #define SQE_VALID_FLAGS (SQE_COMMON_FLAGS | IOSQE_BUFFER_SELECT | \
             IOSQE_IO_DRAIN | IOSQE_CQE_SKIP_SUCCESS)
 
 #define IO_REQ_CLEAN_FLAGS (REQ_F_BUFFER_SELECTED | REQ_F_NEED_CLEANUP | \
                 REQ_F_POLLED | REQ_F_INFLIGHT | REQ_F_CREDS | \
                 REQ_F_ASYNC_DATA)
 
 #define IO_REQ_CLEAN_SLOW_FLAGS (REQ_F_REFCOUNT | REQ_F_LINK | REQ_F_HARDLINK |\
                  IO_REQ_CLEAN_FLAGS)
 
 #define IO_TCTX_REFS_CACHE_NR   (1U << 10)
 
 #define IO_COMPL_BATCH          32
 #define IO_REQ_ALLOC_BATCH      8
 
 enum {
     IO_CHECK_CQ_OVERFLOW_BIT,
     IO_CHECK_CQ_DROPPED_BIT,
 };
 
 struct io_defer_entry {
     struct list_head    list;
     struct io_kiocb     *req;
     u32         seq;
 };
 
 /* 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)
 #define IO_REQ_LINK_FLAGS (REQ_F_LINK | REQ_F_HARDLINK)
 
 static bool io_uring_try_cancel_requests(struct io_ring_ctx *ctx,
                      struct task_struct *task,
                      bool cancel_all);
 
 static void io_dismantle_req(struct io_kiocb *req);
 static void io_clean_op(struct io_kiocb *req);
 static void io_queue_sqe(struct io_kiocb *req);
 
 static void __io_submit_flush_completions(struct io_ring_ctx *ctx);
 
 static struct kmem_cache *req_cachep;
 
 struct sock *io_uring_get_socket(struct file *file)
 {
 #if defined(CONFIG_UNIX)
     if (io_is_uring_fops(file)) {
         struct io_ring_ctx *ctx = file->private_data;
 
         return ctx->ring_sock->sk;
     }
 #endif
     return NULL;
 }
 EXPORT_SYMBOL(io_uring_get_socket);
 
 static inline void io_submit_flush_completions(struct io_ring_ctx *ctx)
 {
     if (!wq_list_empty(&ctx->submit_state.compl_reqs))
         __io_submit_flush_completions(ctx);
 }
 
 static inline unsigned int __io_cqring_events(struct io_ring_ctx *ctx)
 {
     return ctx->cached_cq_tail - READ_ONCE(ctx->rings->cq.head);
 }
 
 static bool io_match_linked(struct io_kiocb *head)
 {
     struct io_kiocb *req;
 
     io_for_each_link(req, head) {
         if (req->flags & REQ_F_INFLIGHT)
             return true;
     }
     return false;
 }
 
 /*
  * As io_match_task() but protected against racing with linked timeouts.
  * User must not hold timeout_lock.
  */
 bool io_match_task_safe(struct io_kiocb *head, struct task_struct *task,
             bool cancel_all)
 {
     bool matched;
 
     if (task && head->task != task)
         return false;
     if (cancel_all)
         return true;
 
     if (head->flags & REQ_F_LINK_TIMEOUT) {
         struct io_ring_ctx *ctx = head->ctx;
 
         /* protect against races with linked timeouts */
         spin_lock_irq(&ctx->timeout_lock);
         matched = io_match_linked(head);
         spin_unlock_irq(&ctx->timeout_lock);
     } else {
         matched = io_match_linked(head);
     }
     return matched;
 }
 
 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)
 {
     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 __cold void io_fallback_req_func(struct work_struct *work)
 {
     struct io_ring_ctx *ctx = container_of(work, struct io_ring_ctx,
                         fallback_work.work);
     struct llist_node *node = llist_del_all(&ctx->fallback_llist);
     struct io_kiocb *req, *tmp;
     bool locked = false;
 
     percpu_ref_get(&ctx->refs);
     llist_for_each_entry_safe(req, tmp, node, io_task_work.node)
         req->io_task_work.func(req, &locked);
 
     if (locked) {
         io_submit_flush_completions(ctx);
         mutex_unlock(&ctx->uring_lock);
     }
     percpu_ref_put(&ctx->refs);
 }
 
 static int io_alloc_hash_table(struct io_hash_table *table, unsigned bits)
 {
     unsigned hash_buckets = 1U << bits;
     size_t hash_size = hash_buckets * sizeof(table->hbs[0]);
 
     table->hbs = kmalloc(hash_size, GFP_KERNEL);
     if (!table->hbs)
         return -ENOMEM;
 
     table->hash_bits = bits;
     init_hash_table(table, hash_buckets);
     return 0;
 }
 
 static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
 {
     struct io_ring_ctx *ctx;
     int hash_bits;
 
     ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
     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 (io_alloc_hash_table(&ctx->cancel_table_locked, hash_bits))
         goto err;
 
     ctx->dummy_ubuf = kzalloc(sizeof(*ctx->dummy_ubuf), GFP_KERNEL);
     if (!ctx->dummy_ubuf)
         goto err;
     /* set invalid range, so io_import_fixed() fails meeting it */
     ctx->dummy_ubuf->ubuf = -1UL;
 
     if (percpu_ref_init(&ctx->refs, io_ring_ctx_ref_free,
                 0, GFP_KERNEL))
         goto err;
 
     ctx->flags = p->flags;
     init_waitqueue_head(&ctx->sqo_sq_wait);
     INIT_LIST_HEAD(&ctx->sqd_list);
     INIT_LIST_HEAD(&ctx->cq_overflow_list);
     INIT_LIST_HEAD(&ctx->io_buffers_cache);
     io_alloc_cache_init(&ctx->apoll_cache);
     io_alloc_cache_init(&ctx->netmsg_cache);
     init_completion(&ctx->ref_comp);
     xa_init_flags(&ctx->personalities, XA_FLAGS_ALLOC1);
     mutex_init(&ctx->uring_lock);
     init_waitqueue_head(&ctx->cq_wait);
     spin_lock_init(&ctx->completion_lock);
     spin_lock_init(&ctx->timeout_lock);
     INIT_WQ_LIST(&ctx->iopoll_list);
     INIT_LIST_HEAD(&ctx->io_buffers_pages);
     INIT_LIST_HEAD(&ctx->io_buffers_comp);
     INIT_LIST_HEAD(&ctx->defer_list);
     INIT_LIST_HEAD(&ctx->timeout_list);
     INIT_LIST_HEAD(&ctx->ltimeout_list);
     spin_lock_init(&ctx->rsrc_ref_lock);
     INIT_LIST_HEAD(&ctx->rsrc_ref_list);
     INIT_DELAYED_WORK(&ctx->rsrc_put_work, io_rsrc_put_work);
     init_llist_head(&ctx->rsrc_put_llist);
     INIT_LIST_HEAD(&ctx->tctx_list);
     ctx->submit_state.free_list.next = NULL;
     INIT_WQ_LIST(&ctx->locked_free_list);
     INIT_DELAYED_WORK(&ctx->fallback_work, io_fallback_req_func);
     INIT_WQ_LIST(&ctx->submit_state.compl_reqs);
     return ctx;
 err:
     kfree(ctx->dummy_ubuf);
     kfree(ctx->cancel_table.hbs);
     kfree(ctx->cancel_table_locked.hbs);
     kfree(ctx->io_bl);
     xa_destroy(&ctx->io_bl_xa);
     kfree(ctx);
     return NULL;
 }
 
 static void io_account_cq_overflow(struct io_ring_ctx *ctx)
 {
     struct io_rings *r = ctx->rings;
 
     WRITE_ONCE(r->cq_overflow, READ_ONCE(r->cq_overflow) + 1);
     ctx->cq_extra--;
 }
 
 static bool req_need_defer(struct io_kiocb *req, u32 seq)
 {
     if (unlikely(req->flags & REQ_F_IO_DRAIN)) {
         struct io_ring_ctx *ctx = req->ctx;
 
         return seq + READ_ONCE(ctx->cq_extra) != ctx->cached_cq_tail;
     }
 
     return false;
 }
 
 static inline void io_req_track_inflight(struct io_kiocb *req)
 {
     if (!(req->flags & REQ_F_INFLIGHT)) {
         req->flags |= REQ_F_INFLIGHT;
         atomic_inc(&req->task->io_uring->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 inline struct io_kiocb *io_prep_linked_timeout(struct io_kiocb *req)
 {
     if (likely(!(req->flags & REQ_F_ARM_LTIMEOUT)))
         return NULL;
     return __io_prep_linked_timeout(req);
 }
 
 static noinline void __io_arm_ltimeout(struct io_kiocb *req)
 {
     io_queue_linked_timeout(__io_prep_linked_timeout(req));
 }
 
 static inline void io_arm_ltimeout(struct io_kiocb *req)
 {
     if (unlikely(req->flags & REQ_F_ARM_LTIMEOUT))
         __io_arm_ltimeout(req);
 }
 
 static void io_prep_async_work(struct io_kiocb *req)
 {
     const struct io_op_def *def = &io_op_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;
     req->work.flags = 0;
     req->work.cancel_seq = atomic_read(&ctx->cancel_seq);
     if (req->flags & REQ_F_FORCE_ASYNC)
         req->work.flags |= IO_WQ_WORK_CONCURRENT;
 
     if (req->file && !io_req_ffs_set(req))
         req->flags |= io_file_get_flags(req->file) << REQ_F_SUPPORT_NOWAIT_BIT;
 
     if (req->flags & REQ_F_ISREG) {
         if (def->hash_reg_file || (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)
             req->work.flags |= IO_WQ_WORK_UNBOUND;
     }
 }
 
 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;
 
         spin_lock_irq(&ctx->timeout_lock);
         io_for_each_link(cur, req)
             io_prep_async_work(cur);
         spin_unlock_irq(&ctx->timeout_lock);
     } else {
         io_for_each_link(cur, req)
             io_prep_async_work(cur);
     }
 }
 
 void io_queue_iowq(struct io_kiocb *req, bool *dont_use)
 {
     struct io_kiocb *link = io_prep_linked_timeout(req);
     struct io_uring_task *tctx = req->task->io_uring;
 
     BUG_ON(!tctx);
     BUG_ON(!tctx->io_wq);
 
     /* 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(req->task, current)))
         req->work.flags |= IO_WQ_WORK_CANCEL;
 
     trace_io_uring_queue_async_work(req, io_wq_is_hashed(&req->work));
     io_wq_enqueue(tctx->io_wq, &req->work);
     if (link)
         io_queue_linked_timeout(link);
 }
 
 static __cold void io_queue_deferred(struct io_ring_ctx *ctx)
 {
     while (!list_empty(&ctx->defer_list)) {
         struct io_defer_entry *de = list_first_entry(&ctx->defer_list,
                         struct io_defer_entry, list);
 
         if (req_need_defer(de->req, de->seq))
             break;
         list_del_init(&de->list);
         io_req_task_queue(de->req);
         kfree(de);
     }
 }
 
 static void io_eventfd_signal(struct io_ring_ctx *ctx)
 {
     struct io_ev_fd *ev_fd;
     bool skip;
 
     spin_lock(&ctx->completion_lock);
     /*
      * Eventfd should only get triggered when at least one event has been
      * posted. Some applications rely on the eventfd notification count only
      * changing IFF a new CQE has been added to the CQ ring. There's no
      * depedency on 1:1 relationship between how many times this function is
      * called (and hence the eventfd count) and number of CQEs posted to the
      * CQ ring.
      */
     skip = ctx->cached_cq_tail == ctx->evfd_last_cq_tail;
     ctx->evfd_last_cq_tail = ctx->cached_cq_tail;
     spin_unlock(&ctx->completion_lock);
     if (skip)
         return;
 
     rcu_read_lock();
     /*
      * rcu_dereference ctx->io_ev_fd once and use it for both for checking
      * and eventfd_signal
      */
     ev_fd = rcu_dereference(ctx->io_ev_fd);
 
     /*
      * Check again if ev_fd exists incase an io_eventfd_unregister call
      * completed between the NULL check of ctx->io_ev_fd at the start of
      * the function and rcu_read_lock.
      */
     if (unlikely(!ev_fd))
         goto out;
     if (READ_ONCE(ctx->rings->cq_flags) & IORING_CQ_EVENTFD_DISABLED)
         goto out;
 
     if (!ev_fd->eventfd_async || io_wq_current_is_worker())
         eventfd_signal(ev_fd->cq_ev_fd, 1);
 out:
     rcu_read_unlock();
 }
 
 void __io_commit_cqring_flush(struct io_ring_ctx *ctx)
 {
     if (ctx->off_timeout_used || ctx->drain_active) {
         spin_lock(&ctx->completion_lock);
         if (ctx->off_timeout_used)
             io_flush_timeouts(ctx);
         if (ctx->drain_active)
             io_queue_deferred(ctx);
         spin_unlock(&ctx->completion_lock);
     }
     if (ctx->has_evfd)
         io_eventfd_signal(ctx);
 }
 
 static inline void io_cqring_ev_posted(struct io_ring_ctx *ctx)
 {
     io_commit_cqring_flush(ctx);
     io_cqring_wake(ctx);
 }
 
 static inline 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_ev_posted(ctx);
 }
 
 void io_cq_unlock_post(struct io_ring_ctx *ctx)
 {
     __io_cq_unlock_post(ctx);
 }
 
 /* Returns true if there are no backlogged entries after the flush */
 static bool __io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force)
 {
     bool all_flushed;
     size_t cqe_size = sizeof(struct io_uring_cqe);
 
     if (!force && __io_cqring_events(ctx) == ctx->cq_entries)
         return false;
 
     if (ctx->flags & IORING_SETUP_CQE32)
         cqe_size <<= 1;
 
     io_cq_lock(ctx);
     while (!list_empty(&ctx->cq_overflow_list)) {
         struct io_uring_cqe *cqe = io_get_cqe(ctx);
         struct io_overflow_cqe *ocqe;
 
         if (!cqe && !force)
             break;
         ocqe = list_first_entry(&ctx->cq_overflow_list,
                     struct io_overflow_cqe, list);
         if (cqe)
             memcpy(cqe, &ocqe->cqe, cqe_size);
         else
             io_account_cq_overflow(ctx);
 
         list_del(&ocqe->list);
         kfree(ocqe);
     }
 
     all_flushed = list_empty(&ctx->cq_overflow_list);
     if (all_flushed) {
         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);
     return all_flushed;
 }
 
 static bool io_cqring_overflow_flush(struct io_ring_ctx *ctx)
 {
     bool ret = true;
 
     if (test_bit(IO_CHECK_CQ_OVERFLOW_BIT, &ctx->check_cq)) {
         /* iopoll syncs against uring_lock, not completion_lock */
         if (ctx->flags & IORING_SETUP_IOPOLL)
             mutex_lock(&ctx->uring_lock);
         ret = __io_cqring_overflow_flush(ctx, false);
         if (ctx->flags & IORING_SETUP_IOPOLL)
             mutex_unlock(&ctx->uring_lock);
     }
 
     return ret;
 }
 
 void __io_put_task(struct task_struct *task, int nr)
 {
     struct io_uring_task *tctx = task->io_uring;
 
     percpu_counter_sub(&tctx->inflight, nr);
     if (unlikely(atomic_read(&tctx->in_idle)))
         wake_up(&tctx->wait);
     put_task_struct_many(task, nr);
 }
 
 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;
 }
 
 static __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 bool io_cqring_event_overflow(struct io_ring_ctx *ctx, u64 user_data,
                      s32 res, u32 cflags, u64 extra1, u64 extra2)
 {
     struct io_overflow_cqe *ocqe;
     size_t ocq_size = sizeof(struct io_overflow_cqe);
     bool is_cqe32 = (ctx->flags & IORING_SETUP_CQE32);
 
     if (is_cqe32)
         ocq_size += sizeof(struct io_uring_cqe);
 
     ocqe = kmalloc(ocq_size, GFP_ATOMIC | __GFP_ACCOUNT);
     trace_io_uring_cqe_overflow(ctx, user_data, res, cflags, ocqe);
     if (!ocqe) {
         /*
          * 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.
          */
         io_account_cq_overflow(ctx);
         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);
 
     }
     ocqe->cqe.user_data = user_data;
     ocqe->cqe.res = res;
     ocqe->cqe.flags = cflags;
     if (is_cqe32) {
         ocqe->cqe.big_cqe[0] = extra1;
         ocqe->cqe.big_cqe[1] = extra2;
     }
     list_add_tail(&ocqe->list, &ctx->cq_overflow_list);
     return true;
 }
 
 bool io_req_cqe_overflow(struct io_kiocb *req)
 {
     if (!(req->flags & REQ_F_CQE32_INIT)) {
         req->extra1 = 0;
         req->extra2 = 0;
     }
     return io_cqring_event_overflow(req->ctx, req->cqe.user_data,
                     req->cqe.res, req->cqe.flags,
                     req->extra1, req->extra2);
 }
 
 /*
  * 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
  */
 struct io_uring_cqe *__io_get_cqe(struct io_ring_ctx *ctx)
 {
     struct io_rings *rings = ctx->rings;
     unsigned int off = ctx->cached_cq_tail & (ctx->cq_entries - 1);
     unsigned int free, queued, len;
 
 
     /* 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)
         return NULL;
 
     if (ctx->flags & IORING_SETUP_CQE32) {
         off <<= 1;
         len <<= 1;
     }
 
     ctx->cqe_cached = &rings->cqes[off];
     ctx->cqe_sentinel = ctx->cqe_cached + len;
 
     ctx->cached_cq_tail++;
     ctx->cqe_cached++;
     if (ctx->flags & IORING_SETUP_CQE32)
         ctx->cqe_cached++;
     return &rings->cqes[off];
 }
 
 bool io_fill_cqe_aux(struct io_ring_ctx *ctx, u64 user_data, s32 res, u32 cflags,
              bool allow_overflow)
 {
     struct io_uring_cqe *cqe;
 
     ctx->cq_extra++;
 
     /*
      * If we can't get a cq entry, userspace overflowed the
      * submission (by quite a lot). Increment the overflow count in
      * the ring.
      */
     cqe = io_get_cqe(ctx);
     if (likely(cqe)) {
         trace_io_uring_complete(ctx, NULL, user_data, res, cflags, 0, 0);
 
         WRITE_ONCE(cqe->user_data, user_data);
         WRITE_ONCE(cqe->res, res);
         WRITE_ONCE(cqe->flags, cflags);
 
         if (ctx->flags & IORING_SETUP_CQE32) {
             WRITE_ONCE(cqe->big_cqe[0], 0);
             WRITE_ONCE(cqe->big_cqe[1], 0);
         }
         return true;
     }
 
     if (allow_overflow)
         return io_cqring_event_overflow(ctx, user_data, res, cflags, 0, 0);
 
     return false;
 }
 
 bool io_post_aux_cqe(struct io_ring_ctx *ctx,
              u64 user_data, s32 res, u32 cflags,
              bool allow_overflow)
 {
     bool filled;
 
     io_cq_lock(ctx);
     filled = io_fill_cqe_aux(ctx, user_data, res, cflags, allow_overflow);
     io_cq_unlock_post(ctx);
     return filled;
 }
 
 static void __io_req_complete_put(struct io_kiocb *req)
 {
     /*
      * If we're the last reference to this request, add to our locked
      * free_list cache.
      */
     if (req_ref_put_and_test(req)) {
         struct io_ring_ctx *ctx = req->ctx;
 
         if (req->flags & IO_REQ_LINK_FLAGS) {
             if (req->flags & IO_DISARM_MASK)
                 io_disarm_next(req);
             if (req->link) {
                 io_req_task_queue(req->link);
                 req->link = NULL;
             }
         }
         io_req_put_rsrc(req);
         /*
          * Selected buffer deallocation in io_clean_op() assumes that
          * we don't hold ->completion_lock. Clean them here to avoid
          * deadlocks.
          */
         io_put_kbuf_comp(req);
         io_dismantle_req(req);
         io_put_task(req->task, 1);
         wq_list_add_head(&req->comp_list, &ctx->locked_free_list);
         ctx->locked_free_nr++;
     }
 }
 
 void __io_req_complete_post(struct io_kiocb *req)
 {
     if (!(req->flags & REQ_F_CQE_SKIP))
         __io_fill_cqe_req(req->ctx, req);
     __io_req_complete_put(req);
 }
 
 void io_req_complete_post(struct io_kiocb *req)
 {
     struct io_ring_ctx *ctx = req->ctx;
 
     io_cq_lock(ctx);
     __io_req_complete_post(req);
     io_cq_unlock_post(ctx);
 }
 
 inline void __io_req_complete(struct io_kiocb *req, unsigned issue_flags)
 {
     io_req_complete_post(req);
 }
 
 void io_req_complete_failed(struct io_kiocb *req, s32 res)
 {
     req_set_fail(req);
     io_req_set_res(req, res, io_put_kbuf(req, IO_URING_F_UNLOCKED));
     io_req_complete_post(req);
 }
 
 /*
  * Don't initialise the fields below on every allocation, but do that in
  * advance and keep them valid across allocations.
  */
 static void io_preinit_req(struct io_kiocb *req, struct io_ring_ctx *ctx)
 {
     req->ctx = ctx;
     req->link = NULL;
     req->async_data = NULL;
     /* not necessary, but safer to zero */
     req->cqe.res = 0;
 }
 
 static void io_flush_cached_locked_reqs(struct io_ring_ctx *ctx,
                     struct io_submit_state *state)
 {
     spin_lock(&ctx->completion_lock);
     wq_list_splice(&ctx->locked_free_list, &state->free_list);
     ctx->locked_free_nr = 0;
     spin_unlock(&ctx->completion_lock);
 }
 
 /*
  * 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;
     void *reqs[IO_REQ_ALLOC_BATCH];
     int ret, i;
 
     /*
      * If we have more than a batch's worth of requests in our IRQ side
      * locked cache, grab the lock and move them over to our submission
      * side cache.
      */
     if (data_race(ctx->locked_free_nr) > IO_COMPL_BATCH) {
         io_flush_cached_locked_reqs(ctx, &ctx->submit_state);
         if (!io_req_cache_empty(ctx))
             return true;
     }
 
     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);
     for (i = 0; i < ret; i++) {
         struct io_kiocb *req = reqs[i];
 
         io_preinit_req(req, ctx);
         io_req_add_to_cache(req, ctx);
     }
     return true;
 }
 
 static inline void io_dismantle_req(struct io_kiocb *req)
 {
     unsigned int flags = req->flags;
 
     if (unlikely(flags & IO_REQ_CLEAN_FLAGS))
         io_clean_op(req);
     if (!(flags & REQ_F_FIXED_FILE))
         io_put_file(req->file);
 }
 
 __cold void io_free_req(struct io_kiocb *req)
 {
     struct io_ring_ctx *ctx = req->ctx;
 
     io_req_put_rsrc(req);
     io_dismantle_req(req);
     io_put_task(req->task, 1);
 
     spin_lock(&ctx->completion_lock);
     wq_list_add_head(&req->comp_list, &ctx->locked_free_list);
     ctx->locked_free_nr++;
     spin_unlock(&ctx->completion_lock);
 }
 
 static void __io_req_find_next_prep(struct io_kiocb *req)
 {
     struct io_ring_ctx *ctx = req->ctx;
 
     io_cq_lock(ctx);
     io_disarm_next(req);
     io_cq_unlock_post(ctx);
 }
 
 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 ctx_flush_and_put(struct io_ring_ctx *ctx, bool *locked)
 {
     if (!ctx)
         return;
     if (ctx->flags & IORING_SETUP_TASKRUN_FLAG)
         atomic_andnot(IORING_SQ_TASKRUN, &ctx->rings->sq_flags);
     if (*locked) {
         io_submit_flush_completions(ctx);
         mutex_unlock(&ctx->uring_lock);
         *locked = false;
     }
     percpu_ref_put(&ctx->refs);
 }
 
 static unsigned int handle_tw_list(struct llist_node *node,
                    struct io_ring_ctx **ctx, bool *locked,
                    struct llist_node *last)
 {
     unsigned int count = 0;
 
     while (node != last) {
         struct llist_node *next = node->next;
         struct io_kiocb *req = container_of(node, struct io_kiocb,
                             io_task_work.node);
 
         prefetch(container_of(next, struct io_kiocb, io_task_work.node));
 
         if (req->ctx != *ctx) {
             ctx_flush_and_put(*ctx, locked);
             *ctx = req->ctx;
             /* if not contended, grab and improve batching */
             *locked = mutex_trylock(&(*ctx)->uring_lock);
             percpu_ref_get(&(*ctx)->refs);
         }
         req->io_task_work.func(req, locked);
         node = next;
         count++;
     }
 
     return count;
 }
 
 /**
  * io_llist_xchg - swap all entries in a lock-less list
  * @head:   the head of lock-less list to delete all entries
  * @new:    new entry as the head of the list
  *
  * If list is empty, return NULL, otherwise, return the pointer to the first entry.
  * The order of entries returned is from the newest to the oldest added one.
  */
 static inline struct llist_node *io_llist_xchg(struct llist_head *head,
                            struct llist_node *new)
 {
     return xchg(&head->first, new);
 }
 
 /**
  * io_llist_cmpxchg - possibly swap all entries in a lock-less list
  * @head:   the head of lock-less list to delete all entries
  * @old:    expected old value of the first entry of the list
  * @new:    new entry as the head of the list
  *
  * perform a cmpxchg on the first entry of the list.
  */
 
 static inline struct llist_node *io_llist_cmpxchg(struct llist_head *head,
                           struct llist_node *old,
                           struct llist_node *new)
 {
     return cmpxchg(&head->first, old, new);
 }
 
 void tctx_task_work(struct callback_head *cb)
 {
     bool uring_locked = false;
     struct io_ring_ctx *ctx = NULL;
     struct io_uring_task *tctx = container_of(cb, struct io_uring_task,
                           task_work);
     struct llist_node fake = {};
     struct llist_node *node = io_llist_xchg(&tctx->task_list, &fake);
     unsigned int loops = 1;
     unsigned int count = handle_tw_list(node, &ctx, &uring_locked, NULL);
 
     node = io_llist_cmpxchg(&tctx->task_list, &fake, NULL);
     while (node != &fake) {
         loops++;
         node = io_llist_xchg(&tctx->task_list, &fake);
         count += handle_tw_list(node, &ctx, &uring_locked, &fake);
         node = io_llist_cmpxchg(&tctx->task_list, &fake, NULL);
     }
 
     ctx_flush_and_put(ctx, &uring_locked);
 
     /* relaxed read is enough as only the task itself sets ->in_idle */
     if (unlikely(atomic_read(&tctx->in_idle)))
         io_uring_drop_tctx_refs(current);
 
     trace_io_uring_task_work_run(tctx, count, loops);
 }
 
 void io_req_task_work_add(struct io_kiocb *req)
 {
     struct io_uring_task *tctx = req->task->io_uring;
     struct io_ring_ctx *ctx = req->ctx;
     struct llist_node *node;
     bool running;
 
     running = !llist_add(&req->io_task_work.node, &tctx->task_list);
 
     /* task_work already pending, we're done */
     if (running)
         return;
 
     if (ctx->flags & IORING_SETUP_TASKRUN_FLAG)
         atomic_or(IORING_SQ_TASKRUN, &ctx->rings->sq_flags);
 
     if (likely(!task_work_add(req->task, &tctx->task_work, ctx->notify_method)))
         return;
 
     node = llist_del_all(&tctx->task_list);
 
     while (node) {
         req = container_of(node, struct io_kiocb, io_task_work.node);
         node = node->next;
         if (llist_add(&req->io_task_work.node,
                   &req->ctx->fallback_llist))
             schedule_delayed_work(&req->ctx->fallback_work, 1);
     }
 }
 
 static void io_req_tw_post(struct io_kiocb *req, bool *locked)
 {
     io_req_complete_post(req);
 }
 
 void io_req_tw_post_queue(struct io_kiocb *req, s32 res, u32 cflags)
 {
     io_req_set_res(req, res, cflags);
     req->io_task_work.func = io_req_tw_post;
     io_req_task_work_add(req);
 }
 
 static void io_req_task_cancel(struct io_kiocb *req, bool *locked)
 {
     /* not needed for normal modes, but SQPOLL depends on it */
     io_tw_lock(req->ctx, locked);
     io_req_complete_failed(req, req->cqe.res);
 }
 
 void io_req_task_submit(struct io_kiocb *req, bool *locked)
 {
     io_tw_lock(req->ctx, locked);
     /* req->task == current here, checking PF_EXITING is safe */
     if (likely(!(req->task->flags & PF_EXITING)))
         io_queue_sqe(req);
     else
         io_req_complete_failed(req, -EFAULT);
 }
 
 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);
 }
 
 void io_free_batch_list(struct io_ring_ctx *ctx, struct io_wq_work_node *node)
     __must_hold(&ctx->uring_lock)
 {
     struct task_struct *task = NULL;
     int task_refs = 0;
 
     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_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);
                 if (!io_alloc_cache_put(&ctx->apoll_cache, &apoll->cache))
                     kfree(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);
         }
         if (!(req->flags & REQ_F_FIXED_FILE))
             io_put_file(req->file);
 
         io_req_put_rsrc_locked(req, ctx);
 
         if (req->task != task) {
             if (task)
                 io_put_task(task, task_refs);
             task = req->task;
             task_refs = 0;
         }
         task_refs++;
         node = req->comp_list.next;
         io_req_add_to_cache(req, ctx);
     } while (node);
 
     if (task)
         io_put_task(task, task_refs);
 }
 
 static void __io_submit_flush_completions(struct io_ring_ctx *ctx)
     __must_hold(&ctx->uring_lock)
 {
     struct io_wq_work_node *node, *prev;
     struct io_submit_state *state = &ctx->submit_state;
 
     spin_lock(&ctx->completion_lock);
     wq_list_for_each(node, prev, &state->compl_reqs) {
         struct io_kiocb *req = container_of(node, struct io_kiocb,
                         comp_list);
 
         if (!(req->flags & REQ_F_CQE_SKIP))
             __io_fill_cqe_req(ctx, req);
     }
     __io_cq_unlock_post(ctx);
 
     io_free_batch_list(ctx, state->compl_reqs.first);
     INIT_WQ_LIST(&state->compl_reqs);
 }
 
 /*
  * Drop reference to request, return next in chain (if there is one) if this
  * was the last reference to this request.
  */
 static inline struct io_kiocb *io_put_req_find_next(struct io_kiocb *req)
 {
     struct io_kiocb *nxt = NULL;
 
     if (req_ref_put_and_test(req)) {
         if (unlikely(req->flags & IO_REQ_LINK_FLAGS))
             nxt = io_req_find_next(req);
         io_free_req(req);
     }
     return nxt;
 }
 
 static unsigned io_cqring_events(struct io_ring_ctx *ctx)
 {
     /* See comment at the top of this file */
     smp_rmb();
     return __io_cqring_events(ctx);
 }
 
 /*
  * We can't just wait for polled events to come to us, we have to actively
  * find and complete them.
  */
 static __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 (!wq_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);
 }
 
 static int io_iopoll_check(struct io_ring_ctx *ctx, long min)
 {
     unsigned int nr_events = 0;
     int ret = 0;
     unsigned long check_cq;
 
     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 {
         /*
          * 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 (wq_list_empty(&ctx->iopoll_list)) {
             u32 tail = ctx->cached_cq_tail;
 
             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 ||
                 wq_list_empty(&ctx->iopoll_list))
                 break;
         }
         ret = io_do_iopoll(ctx, !min);
         if (ret < 0)
             break;
         nr_events += ret;
         ret = 0;
     } while (nr_events < min && !need_resched());
 
     return ret;
 }
 
 void io_req_task_complete(struct io_kiocb *req, bool *locked)
 {
     if (req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING)) {
         unsigned issue_flags = *locked ? 0 : IO_URING_F_UNLOCKED;
 
         req->cqe.flags |= io_put_kbuf(req, issue_flags);
     }
 
     if (*locked)
         io_req_complete_defer(req);
     else
         io_req_complete_post(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 (wq_list_empty(&ctx->iopoll_list)) {
         ctx->poll_multi_queue = false;
     } else if (!ctx->poll_multi_queue) {
         struct io_kiocb *list_req;
 
         list_req = container_of(ctx->iopoll_list.first, struct io_kiocb,
                     comp_list);
         if (list_req->file != req->file)
             ctx->poll_multi_queue = true;
     }
 
     /*
      * For fast devices, IO may have already completed. If it has, add
      * it to the front so we find it first.
      */
     if (READ_ONCE(req->iopoll_completed))
         wq_list_add_head(&req->comp_list, &ctx->iopoll_list);
     else
         wq_list_add_tail(&req->comp_list, &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);
     }
 }
 
 static bool io_bdev_nowait(struct block_device *bdev)
 {
     return !bdev || blk_queue_nowait(bdev_get_queue(bdev));
 }
 
 /*
  * If we tracked the file through the SCM inflight mechanism, we could support
  * any file. For now, just ensure that anything potentially problematic is done
  * inline.
  */
 static bool __io_file_supports_nowait(struct file *file, umode_t mode)
 {
     if (S_ISBLK(mode)) {
         if (IS_ENABLED(CONFIG_BLOCK) &&
             io_bdev_nowait(I_BDEV(file->f_mapping->host)))
             return true;
         return false;
     }
     if (S_ISSOCK(mode))
         return true;
     if (S_ISREG(mode)) {
         if (IS_ENABLED(CONFIG_BLOCK) &&
             io_bdev_nowait(file->f_inode->i_sb->s_bdev) &&
             !io_is_uring_fops(file))
             return true;
         return false;
     }
 
     /* any ->read/write should understand O_NONBLOCK */
     if (file->f_flags & O_NONBLOCK)
         return true;
     return file->f_mode & FMODE_NOWAIT;
 }
 
 /*
  * If we tracked the file through the SCM inflight mechanism, we could support
  * any file. For now, just ensure that anything potentially problematic is done
  * inline.
  */
 unsigned int io_file_get_flags(struct file *file)
 {
     umode_t mode = file_inode(file)->i_mode;
     unsigned int res = 0;
 
     if (S_ISREG(mode))
         res |= FFS_ISREG;
     if (__io_file_supports_nowait(file, mode))
         res |= FFS_NOWAIT;
     if (io_file_need_scm(file))
         res |= FFS_SCM;
     return res;
 }
 
 bool io_alloc_async_data(struct io_kiocb *req)
 {
     WARN_ON_ONCE(!io_op_defs[req->opcode].async_size);
     req->async_data = kmalloc(io_op_defs[req->opcode].async_size, GFP_KERNEL);
     if (req->async_data) {
         req->flags |= REQ_F_ASYNC_DATA;
         return false;
     }
     return true;
 }
 
 int io_req_prep_async(struct io_kiocb *req)
 {
     const struct io_op_def *def = &io_op_defs[req->opcode];
 
     /* assign early for deferred execution for non-fixed file */
     if (def->needs_file && !(req->flags & REQ_F_FIXED_FILE))
         req->file = io_file_get_normal(req, req->cqe.fd);
     if (!def->prep_async)
         return 0;
     if (WARN_ON_ONCE(req_has_async_data(req)))
         return -EFAULT;
     if (!io_op_defs[req->opcode].manual_alloc) {
         if (io_alloc_async_data(req))
             return -EAGAIN;
     }
     return def->prep_async(req);
 }
 
 static u32 io_get_sequence(struct io_kiocb *req)
 {
     u32 seq = req->ctx->cached_sq_head;
     struct io_kiocb *cur;
 
     /* need original cached_sq_head, but it was increased for each req */
     io_for_each_link(cur, req)
         seq--;
     return seq;
 }
 
 static __cold void io_drain_req(struct io_kiocb *req)
 {
     struct io_ring_ctx *ctx = req->ctx;
     struct io_defer_entry *de;
     int ret;
     u32 seq = io_get_sequence(req);
 
     /* Still need defer if there is pending req in defer list. */
     spin_lock(&ctx->completion_lock);
     if (!req_need_defer(req, seq) && list_empty_careful(&ctx->defer_list)) {
         spin_unlock(&ctx->completion_lock);
 queue:
         ctx->drain_active = false;
         io_req_task_queue(req);
         return;
     }
     spin_unlock(&ctx->completion_lock);
 
     ret = io_req_prep_async(req);
     if (ret) {
 fail:
         io_req_complete_failed(req, ret);
         return;
     }
     io_prep_async_link(req);
     de = kmalloc(sizeof(*de), GFP_KERNEL);
     if (!de) {
         ret = -ENOMEM;
         goto fail;
     }
 
     spin_lock(&ctx->completion_lock);
     if (!req_need_defer(req, seq) && list_empty(&ctx->defer_list)) {
         spin_unlock(&ctx->completion_lock);
         kfree(de);
         goto queue;
     }
 
     trace_io_uring_defer(req);
     de->req = req;
     de->seq = seq;
     list_add_tail(&de->list, &ctx->defer_list);
     spin_unlock(&ctx->completion_lock);
 }
 
 static void io_clean_op(struct io_kiocb *req)
 {
     if (req->flags & REQ_F_BUFFER_SELECTED) {
         spin_lock(&req->ctx->completion_lock);
         io_put_kbuf_comp(req);
         spin_unlock(&req->ctx->completion_lock);
     }
 
     if (req->flags & REQ_F_NEED_CLEANUP) {
         const struct io_op_def *def = &io_op_defs[req->opcode];
 
         if (def->cleanup)
             def->cleanup(req);
     }
     if ((req->flags & REQ_F_POLLED) && req->apoll) {
         kfree(req->apoll->double_poll);
         kfree(req->apoll);
         req->apoll = NULL;
     }
     if (req->flags & REQ_F_INFLIGHT) {
         struct io_uring_task *tctx = req->task->io_uring;
 
         atomic_dec(&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;
 }
 
 static bool io_assign_file(struct io_kiocb *req, unsigned int issue_flags)
 {
     if (req->file || !io_op_defs[req->opcode].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;
 }
 
 static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)
 {
     const struct io_op_def *def = &io_op_defs[req->opcode];
     const struct cred *creds = NULL;
     int ret;
 
     if (unlikely(!io_assign_file(req, issue_flags)))
         return -EBADF;
 
     if (unlikely((req->flags & REQ_F_CREDS) && req->creds != current_cred()))
         creds = override_creds(req->creds);
 
     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 (creds)
         revert_creds(creds);
 
     if (ret == IOU_OK) {
         if (issue_flags & IO_URING_F_COMPLETE_DEFER)
             io_req_complete_defer(req);
         else
             io_req_complete_post(req);
     } else if (ret != IOU_ISSUE_SKIP_COMPLETE)
         return ret;
 
     /* If the op doesn't have a file, we're not polling for it */
     if ((req->ctx->flags & IORING_SETUP_IOPOLL) && req->file)
         io_iopoll_req_issued(req, issue_flags);
 
     return 0;
 }
 
 int io_poll_issue(struct io_kiocb *req, bool *locked)
 {
     io_tw_lock(req->ctx, locked);
     if (unlikely(req->task->flags & PF_EXITING))
         return -EFAULT;
     return io_issue_sqe(req, IO_URING_F_NONBLOCK);
 }
 
 struct io_wq_work *io_wq_free_work(struct io_wq_work *work)
 {
     struct io_kiocb *req = container_of(work, struct io_kiocb, work);
 
     req = io_put_req_find_next(req);
     return req ? &req->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_op_def *def = &io_op_defs[req->opcode];
     unsigned int issue_flags = IO_URING_F_UNLOCKED;
     bool needs_poll = false;
     int ret = 0, err = -ECANCELED;
 
     /* one will be dropped by ->io_free_work() after returning to io-wq */
     if (!(req->flags & REQ_F_REFCOUNT))
         __io_req_set_refcount(req, 2);
     else
         req_ref_get(req);
 
     io_arm_ltimeout(req);
 
     /* either cancelled or io-wq is dying, so don't touch tctx->iowq */
     if (work->flags & IO_WQ_WORK_CANCEL) {
 fail:
         io_req_task_queue_fail(req, err);
         return;
     }
     if (!io_assign_file(req, issue_flags)) {
         err = -EBADF;
         work->flags |= IO_WQ_WORK_CANCEL;
         goto fail;
     }
 
     if (req->flags & REQ_F_FORCE_ASYNC) {
         bool opcode_poll = def->pollin || def->pollout;
 
         if (opcode_poll && file_can_poll(req->file)) {
             needs_poll = true;
             issue_flags |= IO_URING_F_NONBLOCK;
         }
     }
 
     do {
         ret = io_issue_sqe(req, issue_flags);
         if (ret != -EAGAIN)
             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;
             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 < 0)
         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 file *file = NULL;
     unsigned long file_ptr;
 
     io_ring_submit_lock(ctx, issue_flags);
 
     if (unlikely((unsigned int)fd >= ctx->nr_user_files))
         goto out;
     fd = array_index_nospec(fd, ctx->nr_user_files);
     file_ptr = io_fixed_file_slot(&ctx->file_table, fd)->file_ptr;
     file = (struct file *) (file_ptr & FFS_MASK);
     file_ptr &= ~FFS_MASK;
     /* mask in overlapping REQ_F and FFS bits */
     req->flags |= (file_ptr << REQ_F_SUPPORT_NOWAIT_BIT);
     io_req_set_rsrc_node(req, ctx, 0);
     WARN_ON_ONCE(file && !test_bit(fd, ctx->file_table.bitmap));
 out:
     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 void io_queue_async(struct io_kiocb *req, int ret)
     __must_hold(&req->ctx->uring_lock)
 {
     struct io_kiocb *linked_timeout;
 
     if (ret != -EAGAIN || (req->flags & REQ_F_NOWAIT)) {
         io_req_complete_failed(req, ret);
         return;
     }
 
     linked_timeout = io_prep_linked_timeout(req);
 
     switch (io_arm_poll_handler(req, 0)) {
     case IO_APOLL_READY:
         io_kbuf_recycle(req, 0);
         io_req_task_queue(req);
         break;
     case IO_APOLL_ABORTED:
         /*
          * Queued up for async execution, worker will release
          * submit reference when the iocb is actually submitted.
          */
         io_kbuf_recycle(req, 0);
         io_queue_iowq(req, NULL);
         break;
     case IO_APOLL_OK:
         break;
     }
 
     if (linked_timeout)
         io_queue_linked_timeout(linked_timeout);
 }
 
 static inline void io_queue_sqe(struct io_kiocb *req)
     __must_hold(&req->ctx->uring_lock)
 {
     int ret;
 
     ret = io_issue_sqe(req, IO_URING_F_NONBLOCK|IO_URING_F_COMPLETE_DEFER);
 
     /*
      * We async punt it if the file wasn't marked NOWAIT, or if the file
      * doesn't support non-blocking read/write attempts
      */
     if (likely(!ret))
         io_arm_ltimeout(req);
     else
         io_queue_async(req, 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_complete_failed(req, req->cqe.res);
     } else if (unlikely(req->ctx->drain_active)) {
         io_drain_req(req);
     } else {
         int ret = io_req_prep_async(req);
 
         if (unlikely(ret))
             io_req_complete_failed(req, ret);
         else
             io_queue_iowq(req, NULL);
     }
 }
 
 /*
  * 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 (!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_req_drain(struct io_kiocb *req)
 {
     struct io_ring_ctx *ctx = req->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 int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
                const struct io_uring_sqe *sqe)
     __must_hold(&ctx->uring_lock)
 {
     const struct io_op_def *def;
     unsigned int sqe_flags;
     int personality;
     u8 opcode;
 
     /* req is partially pre-initialised, see io_preinit_req() */
     req->opcode = opcode = READ_ONCE(sqe->opcode);
     /* same numerical values with corresponding REQ_F_*, safe to copy */
     req->flags = sqe_flags = READ_ONCE(sqe->flags);
     req->cqe.user_data = READ_ONCE(sqe->user_data);
     req->file = NULL;
     req->rsrc_node = NULL;
     req->task = current;
 
     if (unlikely(opcode >= IORING_OP_LAST)) {
         req->opcode = 0;
         return -EINVAL;
     }
     def = &io_op_defs[opcode];
     if (unlikely(sqe_flags & ~SQE_COMMON_FLAGS)) {
         /* enforce forwards compatibility on users */
         if (sqe_flags & ~SQE_VALID_FLAGS)
             return -EINVAL;
         if (sqe_flags & IOSQE_BUFFER_SELECT) {
             if (!def->buffer_select)
                 return -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 -EOPNOTSUPP;
             io_init_req_drain(req);
         }
     }
     if (unlikely(ctx->restricted || ctx->drain_active || ctx->drain_next)) {
         if (ctx->restricted && !io_check_restriction(ctx, req, sqe_flags))
             return -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 -EINVAL;
     if (!def->iopoll && (ctx->flags & IORING_SETUP_IOPOLL))
         return -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 -EINVAL;
         get_cred(req->creds);
         ret = security_uring_override_creds(req->creds);
         if (ret) {
             put_cred(req->creds);
             return 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)
     __must_hold(&ctx->uring_lock)
 {
     struct io_submit_link *link = &ctx->submit_state.link;
     int ret;
 
     ret = io_init_req(ctx, req, sqe);
     if (unlikely(ret))
         return io_submit_fail_init(sqe, req, ret);
 
     /* don't need @sqe from now on */
     trace_io_uring_submit_sqe(req, true);
 
     /*
      * 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)) {
         ret = io_req_prep_async(req);
         if (unlikely(ret))
             return io_submit_fail_init(sqe, req, ret);
 
         trace_io_uring_link(req, link->head);
         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);
     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;
 
     /*
      * 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 const struct io_uring_sqe *io_get_sqe(struct io_ring_ctx *ctx)
 {
     unsigned head, mask = ctx->sq_entries - 1;
     unsigned sq_idx = ctx->cached_sq_head++ & mask;
 
     /*
      * 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.
      */
     head = READ_ONCE(ctx->sq_array[sq_idx]);
     if (likely(head < ctx->sq_entries)) {
         /* double index for 128-byte SQEs, twice as long */
         if (ctx->flags & IORING_SETUP_SQE128)
             head <<= 1;
         return &ctx->sq_sqes[head];
     }
 
     /* drop invalid entries */
     ctx->cq_extra--;
     WRITE_ONCE(ctx->rings->sq_dropped,
            READ_ONCE(ctx->rings->sq_dropped) + 1);
     return NULL;
 }
 
 int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr)
     __must_hold(&ctx->uring_lock)
 {
     unsigned int entries = io_sqring_entries(ctx);
     unsigned int left;
     int ret;
 
     if (unlikely(!entries))
         return 0;
     /* make sure SQ entry isn't read before tail */
     ret = left = min3(nr, ctx->sq_entries, 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_refill(ctx)))
             break;
         req = io_alloc_req(ctx);
         sqe = io_get_sqe(ctx);
         if (unlikely(!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)) &&
             !(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;
 }
 
 struct io_wait_queue {
     struct wait_queue_entry wq;
     struct io_ring_ctx *ctx;
     unsigned cq_tail;
     unsigned nr_timeouts;
 };
 
 static inline bool io_should_wake(struct io_wait_queue *iowq)
 {
     struct io_ring_ctx *ctx = iowq->ctx;
     int dist = ctx->cached_cq_tail - (int) iowq->cq_tail;
 
     /*
      * Wake up if we have enough events, or if a timeout occurred since we
      * started waiting. For timeouts, we always want to return to userspace,
      * regardless of event count.
      */
     return dist >= 0 || atomic_read(&ctx->cq_timeouts) != iowq->nr_timeouts;
 }
 
 static int io_wake_function(struct wait_queue_entry *curr, unsigned int mode,
                 int wake_flags, void *key)
 {
     struct io_wait_queue *iowq = container_of(curr, struct io_wait_queue,
                             wq);
 
     /*
      * Cannot safely flush overflowed CQEs from here, ensure we wake up
      * the task, and the next invocation will do it.
      */
     if (io_should_wake(iowq) ||
         test_bit(IO_CHECK_CQ_OVERFLOW_BIT, &iowq->ctx->check_cq))
         return autoremove_wake_function(curr, mode, wake_flags, key);
     return -1;
 }
 
 int io_run_task_work_sig(void)
 {
     if (io_run_task_work())
         return 1;
     if (task_sigpending(current))
         return -EINTR;
     return 0;
 }
 
 /* when returns >0, the caller should retry */
 static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx,
                       struct io_wait_queue *iowq,
                       ktime_t timeout)
 {
     int ret;
     unsigned long check_cq;
 
     /* make sure we run task_work before checking for signals */
     ret = io_run_task_work_sig();
     if (ret || io_should_wake(iowq))
         return ret;
 
     check_cq = READ_ONCE(ctx->check_cq);
     if (unlikely(check_cq)) {
         /* let the caller flush overflows, retry */
         if (check_cq & BIT(IO_CHECK_CQ_OVERFLOW_BIT))
             return 1;
         if (check_cq & BIT(IO_CHECK_CQ_DROPPED_BIT))
             return -EBADR;
     }
     if (!schedule_hrtimeout(&timeout, HRTIMER_MODE_ABS))
         return -ETIME;
     return 1;
 }
 
 /*
  * Wait until events become available, if we don't already have some. The
  * application must reap them itself, as they reside on the shared cq ring.
  */
 static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
               const sigset_t __user *sig, size_t sigsz,
               struct __kernel_timespec __user *uts)
 {
     struct io_wait_queue iowq;
     struct io_rings *rings = ctx->rings;
     ktime_t timeout = KTIME_MAX;
     int ret;
 
     do {
         io_cqring_overflow_flush(ctx);
         if (io_cqring_events(ctx) >= min_events)
             return 0;
         if (!io_run_task_work())
             break;
     } while (1);
 
     if (sig) {
 #ifdef CONFIG_COMPAT
         if (in_compat_syscall())
             ret = set_compat_user_sigmask((const compat_sigset_t __user *)sig,
                               sigsz);
         else
 #endif
             ret = set_user_sigmask(sig, sigsz);
 
         if (ret)
             return ret;
     }
 
     if (uts) {
         struct timespec64 ts;
 
         if (get_timespec64(&ts, uts))
             return -EFAULT;
         timeout = ktime_add_ns(timespec64_to_ktime(ts), ktime_get_ns());
     }
 
     init_waitqueue_func_entry(&iowq.wq, io_wake_function);
     iowq.wq.private = current;
     INIT_LIST_HEAD(&iowq.wq.entry);
     iowq.ctx = ctx;
     iowq.nr_timeouts = atomic_read(&ctx->cq_timeouts);
     iowq.cq_tail = READ_ONCE(ctx->rings->cq.head) + min_events;
 
     trace_io_uring_cqring_wait(ctx, min_events);
     do {
         /* if we can't even flush overflow, don't wait for more */
         if (!io_cqring_overflow_flush(ctx)) {
             ret = -EBUSY;
             break;
         }
         prepare_to_wait_exclusive(&ctx->cq_wait, &iowq.wq,
                         TASK_INTERRUPTIBLE);
         ret = io_cqring_wait_schedule(ctx, &iowq, timeout);
         cond_resched();
     } while (ret > 0);
 
     finish_wait(&ctx->cq_wait, &iowq.wq);
     restore_saved_sigmask_unless(ret == -EINTR);
 
     return READ_ONCE(rings->cq.head) == READ_ONCE(rings->cq.tail) ? ret : 0;
 }
 
 static void io_mem_free(void *ptr)
 {
     struct page *page;
 
     if (!ptr)
         return;
 
     page = virt_to_head_page(ptr);
     if (put_page_testzero(page))
         free_compound_page(page);
 }
 
 static void *io_mem_alloc(size_t size)
 {
     gfp_t gfp = GFP_KERNEL_ACCOUNT | __GFP_ZERO | __GFP_NOWARN | __GFP_COMP;
 
     return (void *) __get_free_pages(gfp, get_order(size));
 }
 
 static unsigned long rings_size(struct io_ring_ctx *ctx, unsigned int sq_entries,
                 unsigned int cq_entries, size_t *sq_offset)
 {
     struct io_rings *rings;
     size_t off, sq_array_size;
 
     off = struct_size(rings, cqes, cq_entries);
     if (off == SIZE_MAX)
         return SIZE_MAX;
     if (ctx->flags & IORING_SETUP_CQE32) {
         if (check_shl_overflow(off, 1, &off))
             return SIZE_MAX;
     }
 
 #ifdef CONFIG_SMP
     off = ALIGN(off, SMP_CACHE_BYTES);
     if (off == 0)
         return SIZE_MAX;
 #endif
 
     if (sq_offset)
         *sq_offset = off;
 
     sq_array_size = array_size(sizeof(u32), sq_entries);
     if (sq_array_size == SIZE_MAX)
         return SIZE_MAX;
 
     if (check_add_overflow(off, sq_array_size, &off))
         return SIZE_MAX;
 
     return off;
 }
 
 static int io_eventfd_register(struct io_ring_ctx *ctx, void __user *arg,
                    unsigned int eventfd_async)
 {
     struct io_ev_fd *ev_fd;
     __s32 __user *fds = arg;
     int fd;
 
     ev_fd = rcu_dereference_protected(ctx->io_ev_fd,
                     lockdep_is_held(&ctx->uring_lock));
     if (ev_fd)
         return -EBUSY;
 
     if (copy_from_user(&fd, fds, sizeof(*fds)))
         return -EFAULT;
 
     ev_fd = kmalloc(sizeof(*ev_fd), GFP_KERNEL);
     if (!ev_fd)
         return -ENOMEM;
 
     ev_fd->cq_ev_fd = eventfd_ctx_fdget(fd);
     if (IS_ERR(ev_fd->cq_ev_fd)) {
         int ret = PTR_ERR(ev_fd->cq_ev_fd);
         kfree(ev_fd);
         return ret;
     }
 
     spin_lock(&ctx->completion_lock);
     ctx->evfd_last_cq_tail = ctx->cached_cq_tail;
     spin_unlock(&ctx->completion_lock);
 
     ev_fd->eventfd_async = eventfd_async;
     ctx->has_evfd = true;
     rcu_assign_pointer(ctx->io_ev_fd, ev_fd);
     return 0;
 }
 
 static void io_eventfd_put(struct rcu_head *rcu)
 {
     struct io_ev_fd *ev_fd = container_of(rcu, struct io_ev_fd, rcu);
 
     eventfd_ctx_put(ev_fd->cq_ev_fd);
     kfree(ev_fd);
 }
 
 static int io_eventfd_unregister(struct io_ring_ctx *ctx)
 {
     struct io_ev_fd *ev_fd;
 
     ev_fd = rcu_dereference_protected(ctx->io_ev_fd,
                     lockdep_is_held(&ctx->uring_lock));
     if (ev_fd) {
         ctx->has_evfd = false;
         rcu_assign_pointer(ctx->io_ev_fd, NULL);
         call_rcu(&ev_fd->rcu, io_eventfd_put);
         return 0;
     }
 
     return -ENXIO;
 }
 
 static void io_req_caches_free(struct io_ring_ctx *ctx)
 {
     struct io_submit_state *state = &ctx->submit_state;
     int nr = 0;
 
     mutex_lock(&ctx->uring_lock);
     io_flush_cached_locked_reqs(ctx, state);
 
     while (!io_req_cache_empty(ctx)) {
         struct io_wq_work_node *node;
         struct io_kiocb *req;
 
         node = wq_stack_extract(&state->free_list);
         req = container_of(node, struct io_kiocb, comp_list);
         kmem_cache_free(req_cachep, req);
         nr++;
     }
     if (nr)
         percpu_ref_put_many(&ctx->refs, nr);
     mutex_unlock(&ctx->uring_lock);
 }
 
 static __cold void io_ring_ctx_free(struct io_ring_ctx *ctx)
 {
     io_sq_thread_finish(ctx);
 
     if (ctx->mm_account) {
         mmdrop(ctx->mm_account);
         ctx->mm_account = NULL;
     }
 
     io_rsrc_refs_drop(ctx);
     /* __io_rsrc_put_work() may need uring_lock to progress, wait w/o it */
     io_wait_rsrc_data(ctx->buf_data);
     io_wait_rsrc_data(ctx->file_data);
 
     mutex_lock(&ctx->uring_lock);
     if (ctx->buf_data)
         __io_sqe_buffers_unregister(ctx);
     if (ctx->file_data)
         __io_sqe_files_unregister(ctx);
     if (ctx->rings)
         __io_cqring_overflow_flush(ctx, true);
     io_eventfd_unregister(ctx);
     io_alloc_cache_free(&ctx->apoll_cache, io_apoll_cache_free);
     io_alloc_cache_free(&ctx->netmsg_cache, io_netmsg_cache_free);
     mutex_unlock(&ctx->uring_lock);
     io_destroy_buffers(ctx);
     if (ctx->sq_creds)
         put_cred(ctx->sq_creds);
     if (ctx->submitter_task)
         put_task_struct(ctx->submitter_task);
 
     /* there are no registered resources left, nobody uses it */
     if (ctx->rsrc_node)
         io_rsrc_node_destroy(ctx->rsrc_node);
     if (ctx->rsrc_backup_node)
         io_rsrc_node_destroy(ctx->rsrc_backup_node);
     flush_delayed_work(&ctx->rsrc_put_work);
     flush_delayed_work(&ctx->fallback_work);
 
     WARN_ON_ONCE(!list_empty(&ctx->rsrc_ref_list));
     WARN_ON_ONCE(!llist_empty(&ctx->rsrc_put_llist));
 
 #if defined(CONFIG_UNIX)
     if (ctx->ring_sock) {
         ctx->ring_sock->file = NULL; /* so that iput() is called */
         sock_release(ctx->ring_sock);
     }
 #endif
     WARN_ON_ONCE(!list_empty(&ctx->ltimeout_list));
     WARN_ON_ONCE(ctx->notif_slots || ctx->nr_notif_slots);
 
     io_mem_free(ctx->rings);
     io_mem_free(ctx->sq_sqes);
 
     percpu_ref_exit(&ctx->refs);
     free_uid(ctx->user);
     io_req_caches_free(ctx);
     if (ctx->hash_map)
         io_wq_put_hash(ctx->hash_map);
     kfree(ctx->cancel_table.hbs);
     kfree(ctx->cancel_table_locked.hbs);
     kfree(ctx->dummy_ubuf);
     kfree(ctx->io_bl);
     xa_destroy(&ctx->io_bl_xa);
     kfree(ctx);
 }
 
 static __poll_t io_uring_poll(struct file *file, poll_table *wait)
 {
     struct io_ring_ctx *ctx = file->private_data;
     __poll_t mask = 0;
 
     poll_wait(file, &ctx->cq_wait, wait);
     /*
      * synchronizes with barrier from wq_has_sleeper call in
      * io_commit_cqring
      */
     smp_rmb();
     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
      * pushs them to do the flush.
      */
     if (io_cqring_events(ctx) ||
         test_bit(IO_CHECK_CQ_OVERFLOW_BIT, &ctx->check_cq))
         mask |= EPOLLIN | EPOLLRDNORM;
 
     return mask;
 }
 
 static int io_unregister_personality(struct io_ring_ctx *ctx, unsigned id)
 {
     const struct cred *creds;
 
     creds = xa_erase(&ctx->personalities, id);
     if (creds) {
         put_cred(creds);
         return 0;
     }
 
     return -EINVAL;
 }
 
 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_idle, we're in cancellation and it's racy to remove the
      * node. It'll be removed by the end of cancellation, just ignore it.
      */
     if (!atomic_read(&tctx->in_idle))
         io_uring_del_tctx_node((unsigned long)work->ctx);
     complete(&work->completion);
 }
 
 static __cold bool io_cancel_ctx_cb(struct io_wq_work *work, void *data)
 {
     struct io_kiocb *req = container_of(work, struct io_kiocb, work);
 
     return req->ctx == data;
 }
 
 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 + HZ * 60 * 5;
     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 {
         while (io_uring_try_cancel_requests(ctx, NULL, true))
             cond_resched();
 
         if (ctx->sq_data) {
             struct io_sq_data *sqd = ctx->sq_data;
             struct task_struct *tsk;
 
             io_sq_thread_park(sqd);
             tsk = sqd->thread;
             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;
         }
     } while (!wait_for_completion_timeout(&ctx->ref_comp, interval));
 
     init_completion(&exit.completion);
     init_task_work(&exit.task_work, io_tctx_exit_cb);
     exit.ctx = ctx;
     /*
      * Some may use context even when all refs and requests have been put,
      * and they are free to do so while still holding uring_lock or
      * completion_lock, see io_req_task_submit(). Apart from other work,
      * this lock/unlock section also waits them to finish.
      */
     mutex_lock(&ctx->uring_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->uring_lock);
         wait_for_completion(&exit.completion);
         mutex_lock(&ctx->uring_lock);
     }
     mutex_unlock(&ctx->uring_lock);
     spin_lock(&ctx->completion_lock);
     spin_unlock(&ctx->completion_lock);
 
     io_ring_ctx_free(ctx);
 }
 
 static __cold void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx)
 {
     unsigned long index;
     struct creds *creds;
 
     mutex_lock(&ctx->uring_lock);
     percpu_ref_kill(&ctx->refs);
     if (ctx->rings)
         __io_cqring_overflow_flush(ctx, true);
     xa_for_each(&ctx->personalities, index, creds)
         io_unregister_personality(ctx, index);
     if (ctx->rings)
         io_poll_remove_all(ctx, NULL, true);
     mutex_unlock(&ctx->uring_lock);
 
     /* failed during ring init, it couldn't have issued any requests */
     if (ctx->rings) {
         io_kill_timeouts(ctx, NULL, true);
         /* if we failed setting up the ctx, we might not have any rings */
         io_iopoll_try_reap_events(ctx);
         /* drop cached put refs after potentially doing completions */
         if (current->io_uring)
             io_uring_drop_tctx_refs(current);
     }
 
     INIT_WORK(&ctx->exit_work, io_ring_exit_work);
     /*
      * Use system_unbound_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_wq.
      */
     queue_work(system_unbound_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;
 }
 
 struct io_task_cancel {
     struct task_struct *task;
     bool all;
 };
 
 static bool io_cancel_task_cb(struct io_wq_work *work, void *data)
 {
     struct io_kiocb *req = container_of(work, struct io_kiocb, work);
     struct io_task_cancel *cancel = data;
 
     return io_match_task_safe(req, cancel->task, cancel->all);
 }
 
 static __cold bool io_cancel_defer_files(struct io_ring_ctx *ctx,
                      struct task_struct *task,
                      bool cancel_all)
 {
     struct io_defer_entry *de;
     LIST_HEAD(list);
 
     spin_lock(&ctx->completion_lock);
     list_for_each_entry_reverse(de, &ctx->defer_list, list) {
         if (io_match_task_safe(de->req, task, cancel_all)) {
             list_cut_position(&list, &ctx->defer_list, &de->list);
             break;
         }
     }
     spin_unlock(&ctx->completion_lock);
     if (list_empty(&list))
         return false;
 
     while (!list_empty(&list)) {
         de = list_first_entry(&list, struct io_defer_entry, list);
         list_del_init(&de->list);
         io_req_complete_failed(de->req, -ECANCELED);
         kfree(de);
     }
     return true;
 }
 
 static __cold bool io_uring_try_cancel_iowq(struct io_ring_ctx *ctx)
 {
     struct io_tctx_node *node;
     enum io_wq_cancel cret;
     bool ret = false;
 
     mutex_lock(&ctx->uring_lock);
     list_for_each_entry(node, &ctx->tctx_list, ctx_node) {
         struct io_uring_task *tctx = node->task->io_uring;
 
         /*
          * io_wq will stay alive while we hold uring_lock, because it's
          * killed after ctx nodes, which requires to take the lock.
          */
         if (!tctx || !tctx->io_wq)
             continue;
         cret = io_wq_cancel_cb(tctx->io_wq, io_cancel_ctx_cb, ctx, true);
         ret |= (cret != IO_WQ_CANCEL_NOTFOUND);
     }
     mutex_unlock(&ctx->uring_lock);
 
     return ret;
 }
 
 static __cold bool io_uring_try_cancel_requests(struct io_ring_ctx *ctx,
                         struct task_struct *task,
                         bool cancel_all)
 {
     struct io_task_cancel cancel = { .task = task, .all = cancel_all, };
     struct io_uring_task *tctx = task ? task->io_uring : NULL;
     enum io_wq_cancel cret;
     bool ret = false;
 
     /* failed during ring init, it couldn't have issued any requests */
     if (!ctx->rings)
         return false;
 
     if (!task) {
         ret |= io_uring_try_cancel_iowq(ctx);
     } else if (tctx && tctx->io_wq) {
         /*
          * Cancels requests of all rings, not only @ctx, but
          * it's fine as the task is in exit/exec.
          */
         cret = io_wq_cancel_cb(tctx->io_wq, io_cancel_task_cb,
                        &cancel, true);
         ret |= (cret != IO_WQ_CANCEL_NOTFOUND);
     }
 
     /* SQPOLL thread does its own polling */
     if ((!(ctx->flags & IORING_SETUP_SQPOLL) && cancel_all) ||
         (ctx->sq_data && ctx->sq_data->thread == current)) {
         while (!wq_list_empty(&ctx->iopoll_list)) {
             io_iopoll_try_reap_events(ctx);
             ret = true;
         }
     }
 
     ret |= io_cancel_defer_files(ctx, task, cancel_all);
     mutex_lock(&ctx->uring_lock);
     ret |= io_poll_remove_all(ctx, task, cancel_all);
     mutex_unlock(&ctx->uring_lock);
     ret |= io_kill_timeouts(ctx, task, cancel_all);
     if (task)
         ret |= io_run_task_work();
     return ret;
 }
 
 static s64 tctx_inflight(struct io_uring_task *tctx, bool tracked)
 {
     if (tracked)
         return atomic_read(&tctx->inflight_tracked);
     return percpu_counter_sum(&tctx->inflight);
 }
 
 /*
  * Find any io_uring ctx that this task has registered or done IO on, and cancel
  * requests. @sqd should be not-null IFF it's an SQPOLL thread cancellation.
  */
 __cold void io_uring_cancel_generic(bool cancel_all, struct io_sq_data *sqd)
 {
     struct io_uring_task *tctx = current->io_uring;
     struct io_ring_ctx *ctx;
     s64 inflight;
     DEFINE_WAIT(wait);
 
     WARN_ON_ONCE(sqd && sqd->thread != current);
 
     if (!current->io_uring)
         return;
     if (tctx->io_wq)
         io_wq_exit_start(tctx->io_wq);
 
     atomic_inc(&tctx->in_idle);
     do {
         bool loop = false;
 
         io_uring_drop_tctx_refs(current);
         /* read completions before cancelations */
         inflight = tctx_inflight(tctx, !cancel_all);
         if (!inflight)
             break;
 
         if (!sqd) {
             struct io_tctx_node *node;
             unsigned long index;
 
             xa_for_each(&tctx->xa, index, node) {
                 /* sqpoll task will cancel all its requests */
                 if (node->ctx->sq_data)
                     continue;
                 loop |= io_uring_try_cancel_requests(node->ctx,
                             current, cancel_all);
             }
         } else {
             list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
                 loop |= io_uring_try_cancel_requests(ctx,
                                      current,
                                      cancel_all);
         }
 
         if (loop) {
             cond_resched();
             continue;
         }
 
         prepare_to_wait(&tctx->wait, &wait, TASK_INTERRUPTIBLE);
         io_run_task_work();
         io_uring_drop_tctx_refs(current);
 
         /*
          * If we've seen completions, retry without waiting. This
          * avoids a race where a completion comes in before we did
          * prepare_to_wait().
          */
         if (inflight == tctx_inflight(tctx, !cancel_all))
             schedule();
         finish_wait(&tctx->wait, &wait);
     } while (1);
 
     io_uring_clean_tctx(tctx);
     if (cancel_all) {
         /*
          * We shouldn't run task_works after cancel, so just leave
          * ->in_idle set for normal exit.
          */
         atomic_dec(&tctx->in_idle);
         /* for exec all current's requests should be gone, kill tctx */
         __io_uring_free(current);
     }
 }
 
 void __io_uring_cancel(bool cancel_all)
 {
     io_uring_cancel_generic(cancel_all, NULL);
 }
 
 static void *io_uring_validate_mmap_request(struct file *file,
                         loff_t pgoff, size_t sz)
 {
     struct io_ring_ctx *ctx = file->private_data;
     loff_t offset = pgoff << PAGE_SHIFT;
     struct page *page;
     void *ptr;
 
     switch (offset) {
     case IORING_OFF_SQ_RING:
     case IORING_OFF_CQ_RING:
         ptr = ctx->rings;
         break;
     case IORING_OFF_SQES:
         ptr = ctx->sq_sqes;
         break;
     default:
         return ERR_PTR(-EINVAL);
     }
 
     page = virt_to_head_page(ptr);
     if (sz > page_size(page))
         return ERR_PTR(-EINVAL);
 
     return ptr;
 }
 
 #ifdef CONFIG_MMU
 
 static __cold int io_uring_mmap(struct file *file, struct vm_area_struct *vma)
 {
     size_t sz = vma->vm_end - vma->vm_start;
     unsigned long pfn;
     void *ptr;
 
     ptr = io_uring_validate_mmap_request(file, vma->vm_pgoff, sz);
     if (IS_ERR(ptr))
         return PTR_ERR(ptr);
 
     pfn = virt_to_phys(ptr) >> PAGE_SHIFT;
     return remap_pfn_range(vma, vma->vm_start, pfn, sz, vma->vm_page_prot);
 }
 
 #else /* !CONFIG_MMU */
 
 static int io_uring_mmap(struct file *file, struct vm_area_struct *vma)
 {
     return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -EINVAL;
 }
 
 static unsigned int io_uring_nommu_mmap_capabilities(struct file *file)
 {
     return NOMMU_MAP_DIRECT | NOMMU_MAP_READ | NOMMU_MAP_WRITE;
 }
 
 static unsigned long io_uring_nommu_get_unmapped_area(struct file *file,
     unsigned long addr, unsigned long len,
     unsigned long pgoff, unsigned long flags)
 {
     void *ptr;
 
     ptr = io_uring_validate_mmap_request(file, pgoff, len);
     if (IS_ERR(ptr))
         return PTR_ERR(ptr);
 
     return (unsigned long) ptr;
 }
 
 #endif /* !CONFIG_MMU */
 
 static int io_validate_ext_arg(unsigned flags, const void __user *argp, size_t argsz)
 {
     if (flags & IORING_ENTER_EXT_ARG) {
         struct io_uring_getevents_arg arg;
 
         if (argsz != sizeof(arg))
             return -EINVAL;
         if (copy_from_user(&arg, argp, sizeof(arg)))
             return -EFAULT;
     }
     return 0;
 }
 
 static int io_get_ext_arg(unsigned flags, const void __user *argp, size_t *argsz,
               struct __kernel_timespec __user **ts,
               const sigset_t __user **sig)
 {
     struct io_uring_getevents_arg arg;
 
     /*
      * 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)) {
         *sig = (const sigset_t __user *) argp;
         *ts = NULL;
         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 (*argsz != sizeof(arg))
         return -EINVAL;
     if (copy_from_user(&arg, argp, sizeof(arg)))
         return -EFAULT;
     if (arg.pad)
         return -EINVAL;
     *sig = u64_to_user_ptr(arg.sigmask);
     *argsz = arg.sigmask_sz;
     *ts = u64_to_user_ptr(arg.ts);
     return 0;
 }
 
 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 fd f;
     long ret;
 
     io_run_task_work();
 
     if (unlikely(flags & ~(IORING_ENTER_GETEVENTS | IORING_ENTER_SQ_WAKEUP |
                    IORING_ENTER_SQ_WAIT | IORING_ENTER_EXT_ARG |
                    IORING_ENTER_REGISTERED_RING)))
         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);
         f.file = tctx->registered_rings[fd];
         f.flags = 0;
         if (unlikely(!f.file))
             return -EBADF;
     } else {
         f = fdget(fd);
         if (unlikely(!f.file))
             return -EBADF;
         ret = -EOPNOTSUPP;
         if (unlikely(!io_is_uring_fops(f.file)))
             goto out;
     }
 
     ctx = f.file->private_data;
     ret = -EBADFD;
     if (unlikely(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) {
         io_cqring_overflow_flush(ctx);
 
         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) {
             ret = io_sqpoll_wait_sq(ctx);
             if (ret)
                 goto out;
         }
         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) && ctx->syscall_iopoll)
             goto iopoll_locked;
         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(flags, argp, argsz);
             if (likely(!ret2)) {
                 min_complete = min(min_complete,
                            ctx->cq_entries);
                 ret2 = io_iopoll_check(ctx, min_complete);
             }
             mutex_unlock(&ctx->uring_lock);
         } else {
             const sigset_t __user *sig;
             struct __kernel_timespec __user *ts;
 
             ret2 = io_get_ext_arg(flags, argp, &argsz, &ts, &sig);
             if (likely(!ret2)) {
                 min_complete = min(min_complete,
                            ctx->cq_entries);
                 ret2 = io_cqring_wait(ctx, min_complete, sig,
                               argsz, ts);
             }
         }
 
         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:
     fdput(f);
     return ret;
 }
 
 static const struct file_operations io_uring_fops = {
     .release    = io_uring_release,
     .mmap       = io_uring_mmap,
 #ifndef CONFIG_MMU
     .get_unmapped_area = io_uring_nommu_get_unmapped_area,
     .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_uring_params *p)
 {
     struct io_rings *rings;
     size_t size, sq_array_offset;
 
     /* make sure these are sane, as we already accounted them */
     ctx->sq_entries = p->sq_entries;
     ctx->cq_entries = p->cq_entries;
 
     size = rings_size(ctx, p->sq_entries, p->cq_entries, &sq_array_offset);
     if (size == SIZE_MAX)
         return -EOVERFLOW;
 
     rings = io_mem_alloc(size);
     if (!rings)
         return -ENOMEM;
 
     ctx->rings = rings;
     ctx->sq_array = (u32 *)((char *)rings + sq_array_offset);
     rings->sq_ring_mask = p->sq_entries - 1;
     rings->cq_ring_mask = p->cq_entries - 1;
     rings->sq_ring_entries = p->sq_entries;
     rings->cq_ring_entries = p->cq_entries;
 
     if (p->flags & IORING_SETUP_SQE128)
         size = array_size(2 * sizeof(struct io_uring_sqe), p->sq_entries);
     else
         size = array_size(sizeof(struct io_uring_sqe), p->sq_entries);
     if (size == SIZE_MAX) {
         io_mem_free(ctx->rings);
         ctx->rings = NULL;
         return -EOVERFLOW;
     }
 
     ctx->sq_sqes = io_mem_alloc(size);
     if (!ctx->sq_sqes) {
         io_mem_free(ctx->rings);
         ctx->rings = NULL;
         return -ENOMEM;
     }
 
     return 0;
 }
 
 static int io_uring_install_fd(struct io_ring_ctx *ctx, struct file *file)
 {
     int ret, fd;
 
     fd = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
     if (fd < 0)
         return fd;
 
     ret = __io_uring_add_tctx_node(ctx, false);
     if (ret) {
         put_unused_fd(fd);
         return ret;
     }
     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. If UNIX sockets are enabled,
  * we have to tie this fd to a socket for file garbage collection purposes.
  */
 static struct file *io_uring_get_file(struct io_ring_ctx *ctx)
 {
     struct file *file;
 #if defined(CONFIG_UNIX)
     int ret;
 
     ret = sock_create_kern(&init_net, PF_UNIX, SOCK_RAW, IPPROTO_IP,
                 &ctx->ring_sock);
     if (ret)
         return ERR_PTR(ret);
 #endif
 
     file = anon_inode_getfile_secure("[io_uring]", &io_uring_fops, ctx,
                      O_RDWR | O_CLOEXEC, NULL);
 #if defined(CONFIG_UNIX)
     if (IS_ERR(file)) {
         sock_release(ctx->ring_sock);
         ctx->ring_sock = NULL;
     } else {
         ctx->ring_sock->file = file;
     }
 #endif
     return file;
 }
 
 static __cold int io_uring_create(unsigned entries, struct io_uring_params *p,
                   struct io_uring_params __user *params)
 {
     struct io_ring_ctx *ctx;
     struct file *file;
     int ret;
 
     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;
     }
 
     ctx = io_ring_ctx_alloc(p);
     if (!ctx)
         return -ENOMEM;
 
     /*
      * 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 (!capable(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.
      */
     ret = -EINVAL;
     if (ctx->flags & IORING_SETUP_SQPOLL) {
         /* IPI related flags don't make sense with SQPOLL */
         if (ctx->flags & (IORING_SETUP_COOP_TASKRUN |
                   IORING_SETUP_TASKRUN_FLAG))
             goto err;
         ctx->notify_method = TWA_SIGNAL_NO_IPI;
     } else if (ctx->flags & IORING_SETUP_COOP_TASKRUN) {
         ctx->notify_method = TWA_SIGNAL_NO_IPI;
     } else {
         if (ctx->flags & IORING_SETUP_TASKRUN_FLAG)
             goto err;
         ctx->notify_method = TWA_SIGNAL;
     }
 
     /*
      * 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, p);
     if (ret)
         goto err;
 
     ret = io_sq_offload_create(ctx, p);
     if (ret)
         goto err;
     /* always set a rsrc node */
     ret = io_rsrc_node_switch_start(ctx);
     if (ret)
         goto err;
     io_rsrc_node_switch(ctx, NULL);
 
     memset(&p->sq_off, 0, sizeof(p->sq_off));
     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.array = (char *)ctx->sq_array - (char *)ctx->rings;
 
     memset(&p->cq_off, 0, sizeof(p->cq_off));
     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->features = IORING_FEAT_SINGLE_MMAP | IORING_FEAT_NODROP |
             IORING_FEAT_SUBMIT_STABLE | IORING_FEAT_RW_CUR_POS |
             IORING_FEAT_CUR_PERSONALITY | IORING_FEAT_FAST_POLL |
             IORING_FEAT_POLL_32BITS | IORING_FEAT_SQPOLL_NONFIXED |
             IORING_FEAT_EXT_ARG | IORING_FEAT_NATIVE_WORKERS |
             IORING_FEAT_RSRC_TAGS | IORING_FEAT_CQE_SKIP |
             IORING_FEAT_LINKED_FILE;
 
     if (copy_to_user(params, 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;
     }
 
     /*
      * Install ring fd as the very last thing, so we don't risk someone
      * having closed it before we finish setup
      */
     ret = io_uring_install_fd(ctx, file);
     if (ret < 0) {
         /* fput will clean it up */
         fput(file);
         return ret;
     }
 
     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;
 }
 
 /*
  * 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_uring_params p;
     int i;
 
     if (copy_from_user(&p, params, sizeof(p)))
         return -EFAULT;
     for (i = 0; i < ARRAY_SIZE(p.resv); i++) {
         if (p.resv[i])
             return -EINVAL;
     }
 
     if (p.flags & ~(IORING_SETUP_IOPOLL | IORING_SETUP_SQPOLL |
             IORING_SETUP_SQ_AFF | IORING_SETUP_CQSIZE |
             IORING_SETUP_CLAMP | IORING_SETUP_ATTACH_WQ |
             IORING_SETUP_R_DISABLED | IORING_SETUP_SUBMIT_ALL |
             IORING_SETUP_COOP_TASKRUN | IORING_SETUP_TASKRUN_FLAG |
             IORING_SETUP_SQE128 | IORING_SETUP_CQE32 |
             IORING_SETUP_SINGLE_ISSUER))
         return -EINVAL;
 
     return io_uring_create(entries, &p, params);
 }
 
 SYSCALL_DEFINE2(io_uring_setup, u32, entries,
         struct io_uring_params __user *, params)
 {
     return io_uring_setup(entries, params);
 }
 
 static __cold int io_probe(struct io_ring_ctx *ctx, void __user *arg,
                unsigned nr_args)
 {
     struct io_uring_probe *p;
     size_t size;
     int i, ret;
 
     size = struct_size(p, ops, nr_args);
     if (size == SIZE_MAX)
         return -EOVERFLOW;
     p = kzalloc(size, GFP_KERNEL);
     if (!p)
         return -ENOMEM;
 
     ret = -EFAULT;
     if (copy_from_user(p, arg, size))
         goto out;
     ret = -EINVAL;
     if (memchr_inv(p, 0, size))
         goto out;
 
     p->last_op = IORING_OP_LAST - 1;
     if (nr_args > IORING_OP_LAST)
         nr_args = IORING_OP_LAST;
 
     for (i = 0; i < nr_args; i++) {
         p->ops[i].op = i;
         if (!io_op_defs[i].not_supported)
             p->ops[i].flags = IO_URING_OP_SUPPORTED;
     }
     p->ops_len = i;
 
     ret = 0;
     if (copy_to_user(arg, p, size))
         ret = -EFAULT;
 out:
     kfree(p);
     return ret;
 }
 
 static int io_register_personality(struct io_ring_ctx *ctx)
 {
     const struct cred *creds;
     u32 id;
     int ret;
 
     creds = get_current_cred();
 
     ret = xa_alloc_cyclic(&ctx->personalities, &id, (void *)creds,
             XA_LIMIT(0, USHRT_MAX), &ctx->pers_next, GFP_KERNEL);
     if (ret < 0) {
         put_cred(creds);
         return ret;
     }
     return id;
 }
 
 static __cold int io_register_restrictions(struct io_ring_ctx *ctx,
                        void __user *arg, unsigned int nr_args)
 {
     struct io_uring_restriction *res;
     size_t size;
     int i, ret;
 
     /* Restrictions allowed only if rings started disabled */
     if (!(ctx->flags & IORING_SETUP_R_DISABLED))
         return -EBADFD;
 
     /* We allow only a single restrictions registration */
     if (ctx->restrictions.registered)
         return -EBUSY;
 
     if (!arg || nr_args > IORING_MAX_RESTRICTIONS)
         return -EINVAL;
 
     size = array_size(nr_args, sizeof(*res));
     if (size == SIZE_MAX)
         return -EOVERFLOW;
 
     res = memdup_user(arg, size);
     if (IS_ERR(res))
         return PTR_ERR(res);
 
     ret = 0;
 
     for (i = 0; i < nr_args; i++) {
         switch (res[i].opcode) {
         case IORING_RESTRICTION_REGISTER_OP:
             if (res[i].register_op >= IORING_REGISTER_LAST) {
                 ret = -EINVAL;
                 goto out;
             }
 
             __set_bit(res[i].register_op,
                   ctx->restrictions.register_op);
             break;
         case IORING_RESTRICTION_SQE_OP:
             if (res[i].sqe_op >= IORING_OP_LAST) {
                 ret = -EINVAL;
                 goto out;
             }
 
             __set_bit(res[i].sqe_op, ctx->restrictions.sqe_op);
             break;
         case IORING_RESTRICTION_SQE_FLAGS_ALLOWED:
             ctx->restrictions.sqe_flags_allowed = res[i].sqe_flags;
             break;
         case IORING_RESTRICTION_SQE_FLAGS_REQUIRED:
             ctx->restrictions.sqe_flags_required = res[i].sqe_flags;
             break;
         default:
             ret = -EINVAL;
             goto out;
         }
     }
 
 out:
     /* Reset all restrictions if an error happened */
     if (ret != 0)
         memset(&ctx->restrictions, 0, sizeof(ctx->restrictions));
     else
         ctx->restrictions.registered = true;
 
     kfree(res);
     return ret;
 }
 
 static int io_register_enable_rings(struct io_ring_ctx *ctx)
 {
     if (!(ctx->flags & IORING_SETUP_R_DISABLED))
         return -EBADFD;
 
     if (ctx->flags & IORING_SETUP_SINGLE_ISSUER && !ctx->submitter_task)
         ctx->submitter_task = get_task_struct(current);
 
     if (ctx->restrictions.registered)
         ctx->restricted = 1;
 
     ctx->flags &= ~IORING_SETUP_R_DISABLED;
     if (ctx->sq_data && wq_has_sleeper(&ctx->sq_data->wait))
         wake_up(&ctx->sq_data->wait);
     return 0;
 }
 
 static __cold int io_register_iowq_aff(struct io_ring_ctx *ctx,
                        void __user *arg, unsigned len)
 {
     struct io_uring_task *tctx = current->io_uring;
     cpumask_var_t new_mask;
     int ret;
 
     if (!tctx || !tctx->io_wq)
         return -EINVAL;
 
     if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
         return -ENOMEM;
 
     cpumask_clear(new_mask);
     if (len > cpumask_size())
         len = cpumask_size();
 
     if (in_compat_syscall()) {
         ret = compat_get_bitmap(cpumask_bits(new_mask),
                     (const compat_ulong_t __user *)arg,
                     len * 8 /* CHAR_BIT */);
     } else {
         ret = copy_from_user(new_mask, arg, len);
     }
 
     if (ret) {
         free_cpumask_var(new_mask);
         return -EFAULT;
     }
 
     ret = io_wq_cpu_affinity(tctx->io_wq, new_mask);
     free_cpumask_var(new_mask);
     return ret;
 }
 
 static __cold int io_unregister_iowq_aff(struct io_ring_ctx *ctx)
 {
     struct io_uring_task *tctx = current->io_uring;
 
     if (!tctx || !tctx->io_wq)
         return -EINVAL;
 
     return io_wq_cpu_affinity(tctx->io_wq, NULL);
 }
 
 static __cold int io_register_iowq_max_workers(struct io_ring_ctx *ctx,
                            void __user *arg)
     __must_hold(&ctx->uring_lock)
 {
     struct io_tctx_node *node;
     struct io_uring_task *tctx = NULL;
     struct io_sq_data *sqd = NULL;
     __u32 new_count[2];
     int i, ret;
 
     if (copy_from_user(new_count, arg, sizeof(new_count)))
         return -EFAULT;
     for (i = 0; i < ARRAY_SIZE(new_count); i++)
         if (new_count[i] > INT_MAX)
             return -EINVAL;
 
     if (ctx->flags & IORING_SETUP_SQPOLL) {
         sqd = ctx->sq_data;
         if (sqd) {
             /*
              * Observe the correct sqd->lock -> ctx->uring_lock
              * ordering. Fine to drop uring_lock here, we hold
              * a ref to the ctx.
              */
             refcount_inc(&sqd->refs);
             mutex_unlock(&ctx->uring_lock);
             mutex_lock(&sqd->lock);
             mutex_lock(&ctx->uring_lock);
             if (sqd->thread)
                 tctx = sqd->thread->io_uring;
         }
     } else {
         tctx = current->io_uring;
     }
 
     BUILD_BUG_ON(sizeof(new_count) != sizeof(ctx->iowq_limits));
 
     for (i = 0; i < ARRAY_SIZE(new_count); i++)
         if (new_count[i])
             ctx->iowq_limits[i] = new_count[i];
     ctx->iowq_limits_set = true;
 
     if (tctx && tctx->io_wq) {
         ret = io_wq_max_workers(tctx->io_wq, new_count);
         if (ret)
             goto err;
     } else {
         memset(new_count, 0, sizeof(new_count));
     }
 
     if (sqd) {
         mutex_unlock(&sqd->lock);
         io_put_sq_data(sqd);
     }
 
     if (copy_to_user(arg, new_count, sizeof(new_count)))
         return -EFAULT;
 
     /* that's it for SQPOLL, only the SQPOLL task creates requests */
     if (sqd)
         return 0;
 
     /* now propagate the restriction to all registered users */
     list_for_each_entry(node, &ctx->tctx_list, ctx_node) {
         struct io_uring_task *tctx = node->task->io_uring;
 
         if (WARN_ON_ONCE(!tctx->io_wq))
             continue;
 
         for (i = 0; i < ARRAY_SIZE(new_count); i++)
             new_count[i] = ctx->iowq_limits[i];
         /* ignore errors, it always returns zero anyway */
         (void)io_wq_max_workers(tctx->io_wq, new_count);
     }
     return 0;
 err:
     if (sqd) {
         mutex_unlock(&sqd->lock);
         io_put_sq_data(sqd);
     }
     return ret;
 }
 
 static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
                    void __user *arg, unsigned nr_args)
     __releases(ctx->uring_lock)
     __acquires(ctx->uring_lock)
 {
     int ret;
 
     /*
      * We don't quiesce the refs for register anymore and so it can't be
      * dying as we're holding a file ref here.
      */
     if (WARN_ON_ONCE(percpu_ref_is_dying(&ctx->refs)))
         return -ENXIO;
 
     if (ctx->restricted) {
         if (opcode >= IORING_REGISTER_LAST)
             return -EINVAL;
         opcode = array_index_nospec(opcode, IORING_REGISTER_LAST);
         if (!test_bit(opcode, ctx->restrictions.register_op))
             return -EACCES;
     }
 
     switch (opcode) {
     case IORING_REGISTER_BUFFERS:
         ret = -EFAULT;
         if (!arg)
             break;
         ret = io_sqe_buffers_register(ctx, arg, nr_args, NULL);
         break;
     case IORING_UNREGISTER_BUFFERS:
         ret = -EINVAL;
         if (arg || nr_args)
             break;
         ret = io_sqe_buffers_unregister(ctx);
         break;
     case IORING_REGISTER_FILES:
         ret = -EFAULT;
         if (!arg)
             break;
         ret = io_sqe_files_register(ctx, arg, nr_args, NULL);
         break;
     case IORING_UNREGISTER_FILES:
         ret = -EINVAL;
         if (arg || nr_args)
             break;
         ret = io_sqe_files_unregister(ctx);
         break;
     case IORING_REGISTER_FILES_UPDATE:
         ret = io_register_files_update(ctx, arg, nr_args);
         break;
     case IORING_REGISTER_EVENTFD:
         ret = -EINVAL;
         if (nr_args != 1)
             break;
         ret = io_eventfd_register(ctx, arg, 0);
         break;
     case IORING_REGISTER_EVENTFD_ASYNC:
         ret = -EINVAL;
         if (nr_args != 1)
             break;
         ret = io_eventfd_register(ctx, arg, 1);
         break;
     case IORING_UNREGISTER_EVENTFD:
         ret = -EINVAL;
         if (arg || nr_args)
             break;
         ret = io_eventfd_unregister(ctx);
         break;
     case IORING_REGISTER_PROBE:
         ret = -EINVAL;
         if (!arg || nr_args > 256)
             break;
         ret = io_probe(ctx, arg, nr_args);
         break;
     case IORING_REGISTER_PERSONALITY:
         ret = -EINVAL;
         if (arg || nr_args)
             break;
         ret = io_register_personality(ctx);
         break;
     case IORING_UNREGISTER_PERSONALITY:
         ret = -EINVAL;
         if (arg)
             break;
         ret = io_unregister_personality(ctx, nr_args);
         break;
     case IORING_REGISTER_ENABLE_RINGS:
         ret = -EINVAL;
         if (arg || nr_args)
             break;
         ret = io_register_enable_rings(ctx);
         break;
     case IORING_REGISTER_RESTRICTIONS:
         ret = io_register_restrictions(ctx, arg, nr_args);
         break;
     case IORING_REGISTER_FILES2:
         ret = io_register_rsrc(ctx, arg, nr_args, IORING_RSRC_FILE);
         break;
     case IORING_REGISTER_FILES_UPDATE2:
         ret = io_register_rsrc_update(ctx, arg, nr_args,
                           IORING_RSRC_FILE);
         break;
     case IORING_REGISTER_BUFFERS2:
         ret = io_register_rsrc(ctx, arg, nr_args, IORING_RSRC_BUFFER);
         break;
     case IORING_REGISTER_BUFFERS_UPDATE:
         ret = io_register_rsrc_update(ctx, arg, nr_args,
                           IORING_RSRC_BUFFER);
         break;
     case IORING_REGISTER_IOWQ_AFF:
         ret = -EINVAL;
         if (!arg || !nr_args)
             break;
         ret = io_register_iowq_aff(ctx, arg, nr_args);
         break;
     case IORING_UNREGISTER_IOWQ_AFF:
         ret = -EINVAL;
         if (arg || nr_args)
             break;
         ret = io_unregister_iowq_aff(ctx);
         break;
     case IORING_REGISTER_IOWQ_MAX_WORKERS:
         ret = -EINVAL;
         if (!arg || nr_args != 2)
             break;
         ret = io_register_iowq_max_workers(ctx, arg);
         break;
     case IORING_REGISTER_RING_FDS:
         ret = io_ringfd_register(ctx, arg, nr_args);
         break;
     case IORING_UNREGISTER_RING_FDS:
         ret = io_ringfd_unregister(ctx, arg, nr_args);
         break;
     case IORING_REGISTER_PBUF_RING:
         ret = -EINVAL;
         if (!arg || nr_args != 1)
             break;
         ret = io_register_pbuf_ring(ctx, arg);
         break;
     case IORING_UNREGISTER_PBUF_RING:
         ret = -EINVAL;
         if (!arg || nr_args != 1)
             break;
         ret = io_unregister_pbuf_ring(ctx, arg);
         break;
     case IORING_REGISTER_SYNC_CANCEL:
         ret = -EINVAL;
         if (!arg || nr_args != 1)
             break;
         ret = io_sync_cancel(ctx, arg);
         break;
     case IORING_REGISTER_FILE_ALLOC_RANGE:
         ret = -EINVAL;
         if (!arg || nr_args)
             break;
         ret = io_register_file_alloc_range(ctx, arg);
         break;
     default:
         ret = -EINVAL;
         break;
     }
 
     return ret;
 }
 
 SYSCALL_DEFINE4(io_uring_register, unsigned int, fd, unsigned int, opcode,
         void __user *, arg, unsigned int, nr_args)
 {
     struct io_ring_ctx *ctx;
     long ret = -EBADF;
     struct fd f;
 
     f = fdget(fd);
     if (!f.file)
         return -EBADF;
 
     ret = -EOPNOTSUPP;
     if (!io_is_uring_fops(f.file))
         goto out_fput;
 
     ctx = f.file->private_data;
 
     io_run_task_work();
 
     mutex_lock(&ctx->uring_lock);
     ret = __io_uring_register(ctx, opcode, arg, nr_args);
     mutex_unlock(&ctx->uring_lock);
     trace_io_uring_register(ctx, opcode, ctx->nr_user_files, ctx->nr_user_bufs, ret);
 out_fput:
     fdput(f);
     return ret;
 }
 
 static int __init io_uring_init(void)
 {
 #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(46, __u16,  __pad3[0]);
     BUILD_BUG_SQE_ELEM(48, __u64,  addr3);
     BUILD_BUG_SQE_ELEM_SIZE(48, 0, cmd);
     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(int));
 
     BUILD_BUG_ON(sizeof(atomic_t) != sizeof(u32));
 
     io_uring_optable_init();
 
     req_cachep = KMEM_CACHE(io_kiocb, SLAB_HWCACHE_ALIGN | SLAB_PANIC |
                 SLAB_ACCOUNT);
     return 0;
 };
 __initcall(io_uring_init);