Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1061 insertions, 0 deletions

diff --git a/io_uring/poll.c b/io_uring/poll.c
new file mode 100644
index 000000000..a4084acaf
--- /dev/null
+++ b/io_uring/poll.c
@@ -0,0 +1,1061 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/poll.h>
+#include <linux/hashtable.h>
+#include <linux/io_uring.h>
+
+#include <trace/events/io_uring.h>
+
+#include <uapi/linux/io_uring.h>
+
+#include "io_uring.h"
+#include "refs.h"
+#include "opdef.h"
+#include "kbuf.h"
+#include "poll.h"
+#include "cancel.h"
+
+struct io_poll_update {
+	struct file			*file;
+	u64				old_user_data;
+	u64				new_user_data;
+	__poll_t			events;
+	bool				update_events;
+	bool				update_user_data;
+};
+
+struct io_poll_table {
+	struct poll_table_struct pt;
+	struct io_kiocb *req;
+	int nr_entries;
+	int error;
+	bool owning;
+	/* output value, set only if arm poll returns >0 */
+	__poll_t result_mask;
+};
+
+#define IO_POLL_CANCEL_FLAG	BIT(31)
+#define IO_POLL_RETRY_FLAG	BIT(30)
+#define IO_POLL_REF_MASK	GENMASK(29, 0)
+
+/*
+ * We usually have 1-2 refs taken, 128 is more than enough and we want to
+ * maximise the margin between this amount and the moment when it overflows.
+ */
+#define IO_POLL_REF_BIAS	128
+
+#define IO_WQE_F_DOUBLE		1
+
+static inline struct io_kiocb *wqe_to_req(struct wait_queue_entry *wqe)
+{
+	unsigned long priv = (unsigned long)wqe->private;
+
+	return (struct io_kiocb *)(priv & ~IO_WQE_F_DOUBLE);
+}
+
+static inline bool wqe_is_double(struct wait_queue_entry *wqe)
+{
+	unsigned long priv = (unsigned long)wqe->private;
+
+	return priv & IO_WQE_F_DOUBLE;
+}
+
+static bool io_poll_get_ownership_slowpath(struct io_kiocb *req)
+{
+	int v;
+
+	/*
+	 * poll_refs are already elevated and we don't have much hope for
+	 * grabbing the ownership. Instead of incrementing set a retry flag
+	 * to notify the loop that there might have been some change.
+	 */
+	v = atomic_fetch_or(IO_POLL_RETRY_FLAG, &req->poll_refs);
+	if (v & IO_POLL_REF_MASK)
+		return false;
+	return !(atomic_fetch_inc(&req->poll_refs) & IO_POLL_REF_MASK);
+}
+
+/*
+ * If refs part of ->poll_refs (see IO_POLL_REF_MASK) is 0, it's free. We can
+ * bump it and acquire ownership. It's disallowed to modify requests while not
+ * owning it, that prevents from races for enqueueing task_work's and b/w
+ * arming poll and wakeups.
+ */
+static inline bool io_poll_get_ownership(struct io_kiocb *req)
+{
+	if (unlikely(atomic_read(&req->poll_refs) >= IO_POLL_REF_BIAS))
+		return io_poll_get_ownership_slowpath(req);
+	return !(atomic_fetch_inc(&req->poll_refs) & IO_POLL_REF_MASK);
+}
+
+static void io_poll_mark_cancelled(struct io_kiocb *req)
+{
+	atomic_or(IO_POLL_CANCEL_FLAG, &req->poll_refs);
+}
+
+static struct io_poll *io_poll_get_double(struct io_kiocb *req)
+{
+	/* pure poll stashes this in ->async_data, poll driven retry elsewhere */
+	if (req->opcode == IORING_OP_POLL_ADD)
+		return req->async_data;
+	return req->apoll->double_poll;
+}
+
+static struct io_poll *io_poll_get_single(struct io_kiocb *req)
+{
+	if (req->opcode == IORING_OP_POLL_ADD)
+		return io_kiocb_to_cmd(req, struct io_poll);
+	return &req->apoll->poll;
+}
+
+static void io_poll_req_insert(struct io_kiocb *req)
+{
+	struct io_hash_table *table = &req->ctx->cancel_table;
+	u32 index = hash_long(req->cqe.user_data, table->hash_bits);
+	struct io_hash_bucket *hb = &table->hbs[index];
+
+	spin_lock(&hb->lock);
+	hlist_add_head(&req->hash_node, &hb->list);
+	spin_unlock(&hb->lock);
+}
+
+static void io_poll_req_delete(struct io_kiocb *req, struct io_ring_ctx *ctx)
+{
+	struct io_hash_table *table = &req->ctx->cancel_table;
+	u32 index = hash_long(req->cqe.user_data, table->hash_bits);
+	spinlock_t *lock = &table->hbs[index].lock;
+
+	spin_lock(lock);
+	hash_del(&req->hash_node);
+	spin_unlock(lock);
+}
+
+static void io_poll_req_insert_locked(struct io_kiocb *req)
+{
+	struct io_hash_table *table = &req->ctx->cancel_table_locked;
+	u32 index = hash_long(req->cqe.user_data, table->hash_bits);
+
+	lockdep_assert_held(&req->ctx->uring_lock);
+
+	hlist_add_head(&req->hash_node, &table->hbs[index].list);
+}
+
+static void io_poll_tw_hash_eject(struct io_kiocb *req, bool *locked)
+{
+	struct io_ring_ctx *ctx = req->ctx;
+
+	if (req->flags & REQ_F_HASH_LOCKED) {
+		/*
+		 * ->cancel_table_locked is protected by ->uring_lock in
+		 * contrast to per bucket spinlocks. Likely, tctx_task_work()
+		 * already grabbed the mutex for us, but there is a chance it
+		 * failed.
+		 */
+		io_tw_lock(ctx, locked);
+		hash_del(&req->hash_node);
+		req->flags &= ~REQ_F_HASH_LOCKED;
+	} else {
+		io_poll_req_delete(req, ctx);
+	}
+}
+
+static void io_init_poll_iocb(struct io_poll *poll, __poll_t events,
+			      wait_queue_func_t wake_func)
+{
+	poll->head = NULL;
+#define IO_POLL_UNMASK	(EPOLLERR|EPOLLHUP|EPOLLNVAL|EPOLLRDHUP)
+	/* mask in events that we always want/need */
+	poll->events = events | IO_POLL_UNMASK;
+	INIT_LIST_HEAD(&poll->wait.entry);
+	init_waitqueue_func_entry(&poll->wait, wake_func);
+}
+
+static inline void io_poll_remove_entry(struct io_poll *poll)
+{
+	struct wait_queue_head *head = smp_load_acquire(&poll->head);
+
+	if (head) {
+		spin_lock_irq(&head->lock);
+		list_del_init(&poll->wait.entry);
+		poll->head = NULL;
+		spin_unlock_irq(&head->lock);
+	}
+}
+
+static void io_poll_remove_entries(struct io_kiocb *req)
+{
+	/*
+	 * Nothing to do if neither of those flags are set. Avoid dipping
+	 * into the poll/apoll/double cachelines if we can.
+	 */
+	if (!(req->flags & (REQ_F_SINGLE_POLL | REQ_F_DOUBLE_POLL)))
+		return;
+
+	/*
+	 * While we hold the waitqueue lock and the waitqueue is nonempty,
+	 * wake_up_pollfree() will wait for us.  However, taking the waitqueue
+	 * lock in the first place can race with the waitqueue being freed.
+	 *
+	 * We solve this as eventpoll does: by taking advantage of the fact that
+	 * all users of wake_up_pollfree() will RCU-delay the actual free.  If
+	 * we enter rcu_read_lock() and see that the pointer to the queue is
+	 * non-NULL, we can then lock it without the memory being freed out from
+	 * under us.
+	 *
+	 * Keep holding rcu_read_lock() as long as we hold the queue lock, in
+	 * case the caller deletes the entry from the queue, leaving it empty.
+	 * In that case, only RCU prevents the queue memory from being freed.
+	 */
+	rcu_read_lock();
+	if (req->flags & REQ_F_SINGLE_POLL)
+		io_poll_remove_entry(io_poll_get_single(req));
+	if (req->flags & REQ_F_DOUBLE_POLL)
+		io_poll_remove_entry(io_poll_get_double(req));
+	rcu_read_unlock();
+}
+
+enum {
+	IOU_POLL_DONE = 0,
+	IOU_POLL_NO_ACTION = 1,
+	IOU_POLL_REMOVE_POLL_USE_RES = 2,
+	IOU_POLL_REISSUE = 3,
+};
+
+/*
+ * All poll tw should go through this. Checks for poll events, manages
+ * references, does rewait, etc.
+ *
+ * Returns a negative error on failure. IOU_POLL_NO_ACTION when no action
+ * require, which is either spurious wakeup or multishot CQE is served.
+ * IOU_POLL_DONE when it's done with the request, then the mask is stored in
+ * req->cqe.res. IOU_POLL_REMOVE_POLL_USE_RES indicates to remove multishot
+ * poll and that the result is stored in req->cqe.
+ */
+static int io_poll_check_events(struct io_kiocb *req, bool *locked)
+{
+	struct io_ring_ctx *ctx = req->ctx;
+	int v;
+
+	/* req->task == current here, checking PF_EXITING is safe */
+	if (unlikely(req->task->flags & PF_EXITING))
+		return -ECANCELED;
+
+	do {
+		v = atomic_read(&req->poll_refs);
+
+		/* tw handler should be the owner, and so have some references */
+		if (WARN_ON_ONCE(!(v & IO_POLL_REF_MASK)))
+			return IOU_POLL_DONE;
+		if (v & IO_POLL_CANCEL_FLAG)
+			return -ECANCELED;
+		/*
+		 * cqe.res contains only events of the first wake up
+		 * and all others are be lost. Redo vfs_poll() to get
+		 * up to date state.
+		 */
+		if ((v & IO_POLL_REF_MASK) != 1)
+			req->cqe.res = 0;
+		if (v & IO_POLL_RETRY_FLAG) {
+			req->cqe.res = 0;
+			/*
+			 * We won't find new events that came in between
+			 * vfs_poll and the ref put unless we clear the flag
+			 * in advance.
+			 */
+			atomic_andnot(IO_POLL_RETRY_FLAG, &req->poll_refs);
+			v &= ~IO_POLL_RETRY_FLAG;
+		}
+
+		/* the mask was stashed in __io_poll_execute */
+		if (!req->cqe.res) {
+			struct poll_table_struct pt = { ._key = req->apoll_events };
+			req->cqe.res = vfs_poll(req->file, &pt) & req->apoll_events;
+			/*
+			 * We got woken with a mask, but someone else got to
+			 * it first. The above vfs_poll() doesn't add us back
+			 * to the waitqueue, so if we get nothing back, we
+			 * should be safe and attempt a reissue.
+			 */
+			if (unlikely(!req->cqe.res)) {
+				/* Multishot armed need not reissue */
+				if (!(req->apoll_events & EPOLLONESHOT))
+					continue;
+				return IOU_POLL_REISSUE;
+			}
+		}
+		if (req->apoll_events & EPOLLONESHOT)
+			return IOU_POLL_DONE;
+		if (io_is_uring_fops(req->file))
+			return IOU_POLL_DONE;
+
+		/* multishot, just fill a CQE and proceed */
+		if (!(req->flags & REQ_F_APOLL_MULTISHOT)) {
+			__poll_t mask = mangle_poll(req->cqe.res &
+						    req->apoll_events);
+
+			if (!io_post_aux_cqe(ctx, req->cqe.user_data,
+					     mask, IORING_CQE_F_MORE, false)) {
+				io_req_set_res(req, mask, 0);
+				return IOU_POLL_REMOVE_POLL_USE_RES;
+			}
+		} else {
+			int ret = io_poll_issue(req, locked);
+			if (ret == IOU_STOP_MULTISHOT)
+				return IOU_POLL_REMOVE_POLL_USE_RES;
+			if (ret < 0)
+				return ret;
+		}
+
+		/* force the next iteration to vfs_poll() */
+		req->cqe.res = 0;
+
+		/*
+		 * Release all references, retry if someone tried to restart
+		 * task_work while we were executing it.
+		 */
+	} while (atomic_sub_return(v & IO_POLL_REF_MASK, &req->poll_refs) &
+					IO_POLL_REF_MASK);
+
+	return IOU_POLL_NO_ACTION;
+}
+
+static void io_poll_task_func(struct io_kiocb *req, bool *locked)
+{
+	int ret;
+
+	ret = io_poll_check_events(req, locked);
+	if (ret == IOU_POLL_NO_ACTION)
+		return;
+
+	if (ret == IOU_POLL_DONE) {
+		struct io_poll *poll = io_kiocb_to_cmd(req, struct io_poll);
+		req->cqe.res = mangle_poll(req->cqe.res & poll->events);
+	} else if (ret == IOU_POLL_REISSUE) {
+		io_poll_remove_entries(req);
+		io_poll_tw_hash_eject(req, locked);
+		io_req_task_submit(req, locked);
+		return;
+	} else if (ret != IOU_POLL_REMOVE_POLL_USE_RES) {
+		req->cqe.res = ret;
+		req_set_fail(req);
+	}
+
+	io_poll_remove_entries(req);
+	io_poll_tw_hash_eject(req, locked);
+
+	io_req_set_res(req, req->cqe.res, 0);
+	io_req_task_complete(req, locked);
+}
+
+static void io_apoll_task_func(struct io_kiocb *req, bool *locked)
+{
+	int ret;
+
+	ret = io_poll_check_events(req, locked);
+	if (ret == IOU_POLL_NO_ACTION)
+		return;
+
+	io_tw_lock(req->ctx, locked);
+	io_poll_remove_entries(req);
+	io_poll_tw_hash_eject(req, locked);
+
+	if (ret == IOU_POLL_REMOVE_POLL_USE_RES)
+		io_req_task_complete(req, locked);
+	else if (ret == IOU_POLL_DONE || ret == IOU_POLL_REISSUE)
+		io_req_task_submit(req, locked);
+	else
+		io_req_complete_failed(req, ret);
+}
+
+static void __io_poll_execute(struct io_kiocb *req, int mask)
+{
+	io_req_set_res(req, mask, 0);
+	/*
+	 * This is useful for poll that is armed on behalf of another
+	 * request, and where the wakeup path could be on a different
+	 * CPU. We want to avoid pulling in req->apoll->events for that
+	 * case.
+	 */
+	if (req->opcode == IORING_OP_POLL_ADD)
+		req->io_task_work.func = io_poll_task_func;
+	else
+		req->io_task_work.func = io_apoll_task_func;
+
+	trace_io_uring_task_add(req, mask);
+	io_req_task_work_add(req);
+}
+
+static inline void io_poll_execute(struct io_kiocb *req, int res)
+{
+	if (io_poll_get_ownership(req))
+		__io_poll_execute(req, res);
+}
+
+static void io_poll_cancel_req(struct io_kiocb *req)
+{
+	io_poll_mark_cancelled(req);
+	/* kick tw, which should complete the request */
+	io_poll_execute(req, 0);
+}
+
+#define IO_ASYNC_POLL_COMMON	(EPOLLONESHOT | EPOLLPRI)
+
+static __cold int io_pollfree_wake(struct io_kiocb *req, struct io_poll *poll)
+{
+	io_poll_mark_cancelled(req);
+	/* we have to kick tw in case it's not already */
+	io_poll_execute(req, 0);
+
+	/*
+	 * If the waitqueue is being freed early but someone is already
+	 * holds ownership over it, we have to tear down the request as
+	 * best we can. That means immediately removing the request from
+	 * its waitqueue and preventing all further accesses to the
+	 * waitqueue via the request.
+	 */
+	list_del_init(&poll->wait.entry);
+
+	/*
+	 * Careful: this *must* be the last step, since as soon
+	 * as req->head is NULL'ed out, the request can be
+	 * completed and freed, since aio_poll_complete_work()
+	 * will no longer need to take the waitqueue lock.
+	 */
+	smp_store_release(&poll->head, NULL);
+	return 1;
+}
+
+static int io_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
+			void *key)
+{
+	struct io_kiocb *req = wqe_to_req(wait);
+	struct io_poll *poll = container_of(wait, struct io_poll, wait);
+	__poll_t mask = key_to_poll(key);
+
+	if (unlikely(mask & POLLFREE))
+		return io_pollfree_wake(req, poll);
+
+	/* for instances that support it check for an event match first */
+	if (mask && !(mask & (poll->events & ~IO_ASYNC_POLL_COMMON)))
+		return 0;
+
+	if (io_poll_get_ownership(req)) {
+		/*
+		 * If we trigger a multishot poll off our own wakeup path,
+		 * disable multishot as there is a circular dependency between
+		 * CQ posting and triggering the event.
+		 */
+		if (mask & EPOLL_URING_WAKE)
+			poll->events |= EPOLLONESHOT;
+
+		/* optional, saves extra locking for removal in tw handler */
+		if (mask && poll->events & EPOLLONESHOT) {
+			list_del_init(&poll->wait.entry);
+			poll->head = NULL;
+			if (wqe_is_double(wait))
+				req->flags &= ~REQ_F_DOUBLE_POLL;
+			else
+				req->flags &= ~REQ_F_SINGLE_POLL;
+		}
+		__io_poll_execute(req, mask);
+	}
+	return 1;
+}
+
+/* fails only when polling is already completing by the first entry */
+static bool io_poll_double_prepare(struct io_kiocb *req)
+{
+	struct wait_queue_head *head;
+	struct io_poll *poll = io_poll_get_single(req);
+
+	/* head is RCU protected, see io_poll_remove_entries() comments */
+	rcu_read_lock();
+	head = smp_load_acquire(&poll->head);
+	/*
+	 * poll arm might not hold ownership and so race for req->flags with
+	 * io_poll_wake(). There is only one poll entry queued, serialise with
+	 * it by taking its head lock. As we're still arming the tw hanlder
+	 * is not going to be run, so there are no races with it.
+	 */
+	if (head) {
+		spin_lock_irq(&head->lock);
+		req->flags |= REQ_F_DOUBLE_POLL;
+		if (req->opcode == IORING_OP_POLL_ADD)
+			req->flags |= REQ_F_ASYNC_DATA;
+		spin_unlock_irq(&head->lock);
+	}
+	rcu_read_unlock();
+	return !!head;
+}
+
+static void __io_queue_proc(struct io_poll *poll, struct io_poll_table *pt,
+			    struct wait_queue_head *head,
+			    struct io_poll **poll_ptr)
+{
+	struct io_kiocb *req = pt->req;
+	unsigned long wqe_private = (unsigned long) req;
+
+	/*
+	 * The file being polled uses multiple waitqueues for poll handling
+	 * (e.g. one for read, one for write). Setup a separate io_poll
+	 * if this happens.
+	 */
+	if (unlikely(pt->nr_entries)) {
+		struct io_poll *first = poll;
+
+		/* double add on the same waitqueue head, ignore */
+		if (first->head == head)
+			return;
+		/* already have a 2nd entry, fail a third attempt */
+		if (*poll_ptr) {
+			if ((*poll_ptr)->head == head)
+				return;
+			pt->error = -EINVAL;
+			return;
+		}
+
+		poll = kmalloc(sizeof(*poll), GFP_ATOMIC);
+		if (!poll) {
+			pt->error = -ENOMEM;
+			return;
+		}
+
+		/* mark as double wq entry */
+		wqe_private |= IO_WQE_F_DOUBLE;
+		io_init_poll_iocb(poll, first->events, first->wait.func);
+		if (!io_poll_double_prepare(req)) {
+			/* the request is completing, just back off */
+			kfree(poll);
+			return;
+		}
+		*poll_ptr = poll;
+	} else {
+		/* fine to modify, there is no poll queued to race with us */
+		req->flags |= REQ_F_SINGLE_POLL;
+	}
+
+	pt->nr_entries++;
+	poll->head = head;
+	poll->wait.private = (void *) wqe_private;
+
+	if (poll->events & EPOLLEXCLUSIVE)
+		add_wait_queue_exclusive(head, &poll->wait);
+	else
+		add_wait_queue(head, &poll->wait);
+}
+
+static void io_poll_queue_proc(struct file *file, struct wait_queue_head *head,
+			       struct poll_table_struct *p)
+{
+	struct io_poll_table *pt = container_of(p, struct io_poll_table, pt);
+	struct io_poll *poll = io_kiocb_to_cmd(pt->req, struct io_poll);
+
+	__io_queue_proc(poll, pt, head,
+			(struct io_poll **) &pt->req->async_data);
+}
+
+static bool io_poll_can_finish_inline(struct io_kiocb *req,
+				      struct io_poll_table *pt)
+{
+	return pt->owning || io_poll_get_ownership(req);
+}
+
+static void io_poll_add_hash(struct io_kiocb *req)
+{
+	if (req->flags & REQ_F_HASH_LOCKED)
+		io_poll_req_insert_locked(req);
+	else
+		io_poll_req_insert(req);
+}
+
+/*
+ * Returns 0 when it's handed over for polling. The caller owns the requests if
+ * it returns non-zero, but otherwise should not touch it. Negative values
+ * contain an error code. When the result is >0, the polling has completed
+ * inline and ipt.result_mask is set to the mask.
+ */
+static int __io_arm_poll_handler(struct io_kiocb *req,
+				 struct io_poll *poll,
+				 struct io_poll_table *ipt, __poll_t mask,
+				 unsigned issue_flags)
+{
+	struct io_ring_ctx *ctx = req->ctx;
+
+	INIT_HLIST_NODE(&req->hash_node);
+	req->work.cancel_seq = atomic_read(&ctx->cancel_seq);
+	io_init_poll_iocb(poll, mask, io_poll_wake);
+	poll->file = req->file;
+	req->apoll_events = poll->events;
+
+	ipt->pt._key = mask;
+	ipt->req = req;
+	ipt->error = 0;
+	ipt->nr_entries = 0;
+	/*
+	 * Polling is either completed here or via task_work, so if we're in the
+	 * task context we're naturally serialised with tw by merit of running
+	 * the same task. When it's io-wq, take the ownership to prevent tw
+	 * from running. However, when we're in the task context, skip taking
+	 * it as an optimisation.
+	 *
+	 * Note: even though the request won't be completed/freed, without
+	 * ownership we still can race with io_poll_wake().
+	 * io_poll_can_finish_inline() tries to deal with that.
+	 */
+	ipt->owning = issue_flags & IO_URING_F_UNLOCKED;
+	atomic_set(&req->poll_refs, (int)ipt->owning);
+
+	/* io-wq doesn't hold uring_lock */
+	if (issue_flags & IO_URING_F_UNLOCKED)
+		req->flags &= ~REQ_F_HASH_LOCKED;
+
+	mask = vfs_poll(req->file, &ipt->pt) & poll->events;
+
+	if (unlikely(ipt->error || !ipt->nr_entries)) {
+		io_poll_remove_entries(req);
+
+		if (!io_poll_can_finish_inline(req, ipt)) {
+			io_poll_mark_cancelled(req);
+			return 0;
+		} else if (mask && (poll->events & EPOLLET)) {
+			ipt->result_mask = mask;
+			return 1;
+		}
+		return ipt->error ?: -EINVAL;
+	}
+
+	if (mask &&
+	   ((poll->events & (EPOLLET|EPOLLONESHOT)) == (EPOLLET|EPOLLONESHOT))) {
+		if (!io_poll_can_finish_inline(req, ipt)) {
+			io_poll_add_hash(req);
+			return 0;
+		}
+		io_poll_remove_entries(req);
+		ipt->result_mask = mask;
+		/* no one else has access to the req, forget about the ref */
+		return 1;
+	}
+
+	io_poll_add_hash(req);
+
+	if (mask && (poll->events & EPOLLET) &&
+	    io_poll_can_finish_inline(req, ipt)) {
+		__io_poll_execute(req, mask);
+		return 0;
+	}
+
+	if (ipt->owning) {
+		/*
+		 * Try to release ownership. If we see a change of state, e.g.
+		 * poll was waken up, queue up a tw, it'll deal with it.
+		 */
+		if (atomic_cmpxchg(&req->poll_refs, 1, 0) != 1)
+			__io_poll_execute(req, 0);
+	}
+	return 0;
+}
+
+static void io_async_queue_proc(struct file *file, struct wait_queue_head *head,
+			       struct poll_table_struct *p)
+{
+	struct io_poll_table *pt = container_of(p, struct io_poll_table, pt);
+	struct async_poll *apoll = pt->req->apoll;
+
+	__io_queue_proc(&apoll->poll, pt, head, &apoll->double_poll);
+}
+
+/*
+ * We can't reliably detect loops in repeated poll triggers and issue
+ * subsequently failing. But rather than fail these immediately, allow a
+ * certain amount of retries before we give up. Given that this condition
+ * should _rarely_ trigger even once, we should be fine with a larger value.
+ */
+#define APOLL_MAX_RETRY		128
+
+static struct async_poll *io_req_alloc_apoll(struct io_kiocb *req,
+					     unsigned issue_flags)
+{
+	struct io_ring_ctx *ctx = req->ctx;
+	struct io_cache_entry *entry;
+	struct async_poll *apoll;
+
+	if (req->flags & REQ_F_POLLED) {
+		apoll = req->apoll;
+		kfree(apoll->double_poll);
+	} else if (!(issue_flags & IO_URING_F_UNLOCKED)) {
+		entry = io_alloc_cache_get(&ctx->apoll_cache);
+		if (entry == NULL)
+			goto alloc_apoll;
+		apoll = container_of(entry, struct async_poll, cache);
+		apoll->poll.retries = APOLL_MAX_RETRY;
+	} else {
+alloc_apoll:
+		apoll = kmalloc(sizeof(*apoll), GFP_ATOMIC);
+		if (unlikely(!apoll))
+			return NULL;
+		apoll->poll.retries = APOLL_MAX_RETRY;
+	}
+	apoll->double_poll = NULL;
+	req->apoll = apoll;
+	if (unlikely(!--apoll->poll.retries))
+		return NULL;
+	return apoll;
+}
+
+int io_arm_poll_handler(struct io_kiocb *req, unsigned issue_flags)
+{
+	const struct io_op_def *def = &io_op_defs[req->opcode];
+	struct async_poll *apoll;
+	struct io_poll_table ipt;
+	__poll_t mask = POLLPRI | POLLERR | EPOLLET;
+	int ret;
+
+	/*
+	 * apoll requests already grab the mutex to complete in the tw handler,
+	 * so removal from the mutex-backed hash is free, use it by default.
+	 */
+	req->flags |= REQ_F_HASH_LOCKED;
+
+	if (!def->pollin && !def->pollout)
+		return IO_APOLL_ABORTED;
+	if (!file_can_poll(req->file))
+		return IO_APOLL_ABORTED;
+	if (!(req->flags & REQ_F_APOLL_MULTISHOT))
+		mask |= EPOLLONESHOT;
+
+	if (def->pollin) {
+		mask |= EPOLLIN | EPOLLRDNORM;
+
+		/* If reading from MSG_ERRQUEUE using recvmsg, ignore POLLIN */
+		if (req->flags & REQ_F_CLEAR_POLLIN)
+			mask &= ~EPOLLIN;
+	} else {
+		mask |= EPOLLOUT | EPOLLWRNORM;
+	}
+	if (def->poll_exclusive)
+		mask |= EPOLLEXCLUSIVE;
+
+	apoll = io_req_alloc_apoll(req, issue_flags);
+	if (!apoll)
+		return IO_APOLL_ABORTED;
+	req->flags &= ~(REQ_F_SINGLE_POLL | REQ_F_DOUBLE_POLL);
+	req->flags |= REQ_F_POLLED;
+	ipt.pt._qproc = io_async_queue_proc;
+
+	io_kbuf_recycle(req, issue_flags);
+
+	ret = __io_arm_poll_handler(req, &apoll->poll, &ipt, mask, issue_flags);
+	if (ret)
+		return ret > 0 ? IO_APOLL_READY : IO_APOLL_ABORTED;
+	trace_io_uring_poll_arm(req, mask, apoll->poll.events);
+	return IO_APOLL_OK;
+}
+
+static __cold bool io_poll_remove_all_table(struct task_struct *tsk,
+					    struct io_hash_table *table,
+					    bool cancel_all)
+{
+	unsigned nr_buckets = 1U << table->hash_bits;
+	struct hlist_node *tmp;
+	struct io_kiocb *req;
+	bool found = false;
+	int i;
+
+	for (i = 0; i < nr_buckets; i++) {
+		struct io_hash_bucket *hb = &table->hbs[i];
+
+		spin_lock(&hb->lock);
+		hlist_for_each_entry_safe(req, tmp, &hb->list, hash_node) {
+			if (io_match_task_safe(req, tsk, cancel_all)) {
+				hlist_del_init(&req->hash_node);
+				io_poll_cancel_req(req);
+				found = true;
+			}
+		}
+		spin_unlock(&hb->lock);
+	}
+	return found;
+}
+
+/*
+ * Returns true if we found and killed one or more poll requests
+ */
+__cold bool io_poll_remove_all(struct io_ring_ctx *ctx, struct task_struct *tsk,
+			       bool cancel_all)
+	__must_hold(&ctx->uring_lock)
+{
+	bool ret;
+
+	ret = io_poll_remove_all_table(tsk, &ctx->cancel_table, cancel_all);
+	ret |= io_poll_remove_all_table(tsk, &ctx->cancel_table_locked, cancel_all);
+	return ret;
+}
+
+static struct io_kiocb *io_poll_find(struct io_ring_ctx *ctx, bool poll_only,
+				     struct io_cancel_data *cd,
+				     struct io_hash_table *table,
+				     struct io_hash_bucket **out_bucket)
+{
+	struct io_kiocb *req;
+	u32 index = hash_long(cd->data, table->hash_bits);
+	struct io_hash_bucket *hb = &table->hbs[index];
+
+	*out_bucket = NULL;
+
+	spin_lock(&hb->lock);
+	hlist_for_each_entry(req, &hb->list, hash_node) {
+		if (cd->data != req->cqe.user_data)
+			continue;
+		if (poll_only && req->opcode != IORING_OP_POLL_ADD)
+			continue;
+		if (cd->flags & IORING_ASYNC_CANCEL_ALL) {
+			if (cd->seq == req->work.cancel_seq)
+				continue;
+			req->work.cancel_seq = cd->seq;
+		}
+		*out_bucket = hb;
+		return req;
+	}
+	spin_unlock(&hb->lock);
+	return NULL;
+}
+
+static struct io_kiocb *io_poll_file_find(struct io_ring_ctx *ctx,
+					  struct io_cancel_data *cd,
+					  struct io_hash_table *table,
+					  struct io_hash_bucket **out_bucket)
+{
+	unsigned nr_buckets = 1U << table->hash_bits;
+	struct io_kiocb *req;
+	int i;
+
+	*out_bucket = NULL;
+
+	for (i = 0; i < nr_buckets; i++) {
+		struct io_hash_bucket *hb = &table->hbs[i];
+
+		spin_lock(&hb->lock);
+		hlist_for_each_entry(req, &hb->list, hash_node) {
+			if (!(cd->flags & IORING_ASYNC_CANCEL_ANY) &&
+			    req->file != cd->file)
+				continue;
+			if (cd->seq == req->work.cancel_seq)
+				continue;
+			req->work.cancel_seq = cd->seq;
+			*out_bucket = hb;
+			return req;
+		}
+		spin_unlock(&hb->lock);
+	}
+	return NULL;
+}
+
+static int io_poll_disarm(struct io_kiocb *req)
+{
+	if (!req)
+		return -ENOENT;
+	if (!io_poll_get_ownership(req))
+		return -EALREADY;
+	io_poll_remove_entries(req);
+	hash_del(&req->hash_node);
+	return 0;
+}
+
+static int __io_poll_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd,
+			    struct io_hash_table *table)
+{
+	struct io_hash_bucket *bucket;
+	struct io_kiocb *req;
+
+	if (cd->flags & (IORING_ASYNC_CANCEL_FD|IORING_ASYNC_CANCEL_ANY))
+		req = io_poll_file_find(ctx, cd, table, &bucket);
+	else
+		req = io_poll_find(ctx, false, cd, table, &bucket);
+
+	if (req)
+		io_poll_cancel_req(req);
+	if (bucket)
+		spin_unlock(&bucket->lock);
+	return req ? 0 : -ENOENT;
+}
+
+int io_poll_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd,
+		   unsigned issue_flags)
+{
+	int ret;
+
+	ret = __io_poll_cancel(ctx, cd, &ctx->cancel_table);
+	if (ret != -ENOENT)
+		return ret;
+
+	io_ring_submit_lock(ctx, issue_flags);
+	ret = __io_poll_cancel(ctx, cd, &ctx->cancel_table_locked);
+	io_ring_submit_unlock(ctx, issue_flags);
+	return ret;
+}
+
+static __poll_t io_poll_parse_events(const struct io_uring_sqe *sqe,
+				     unsigned int flags)
+{
+	u32 events;
+
+	events = READ_ONCE(sqe->poll32_events);
+#ifdef __BIG_ENDIAN
+	events = swahw32(events);
+#endif
+	if (!(flags & IORING_POLL_ADD_MULTI))
+		events |= EPOLLONESHOT;
+	if (!(flags & IORING_POLL_ADD_LEVEL))
+		events |= EPOLLET;
+	return demangle_poll(events) |
+		(events & (EPOLLEXCLUSIVE|EPOLLONESHOT|EPOLLET));
+}
+
+int io_poll_remove_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_poll_update *upd = io_kiocb_to_cmd(req, struct io_poll_update);
+	u32 flags;
+
+	if (sqe->buf_index || sqe->splice_fd_in)
+		return -EINVAL;
+	flags = READ_ONCE(sqe->len);
+	if (flags & ~(IORING_POLL_UPDATE_EVENTS | IORING_POLL_UPDATE_USER_DATA |
+		      IORING_POLL_ADD_MULTI))
+		return -EINVAL;
+	/* meaningless without update */
+	if (flags == IORING_POLL_ADD_MULTI)
+		return -EINVAL;
+
+	upd->old_user_data = READ_ONCE(sqe->addr);
+	upd->update_events = flags & IORING_POLL_UPDATE_EVENTS;
+	upd->update_user_data = flags & IORING_POLL_UPDATE_USER_DATA;
+
+	upd->new_user_data = READ_ONCE(sqe->off);
+	if (!upd->update_user_data && upd->new_user_data)
+		return -EINVAL;
+	if (upd->update_events)
+		upd->events = io_poll_parse_events(sqe, flags);
+	else if (sqe->poll32_events)
+		return -EINVAL;
+
+	return 0;
+}
+
+int io_poll_add_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_poll *poll = io_kiocb_to_cmd(req, struct io_poll);
+	u32 flags;
+
+	if (sqe->buf_index || sqe->off || sqe->addr)
+		return -EINVAL;
+	flags = READ_ONCE(sqe->len);
+	if (flags & ~IORING_POLL_ADD_MULTI)
+		return -EINVAL;
+	if ((flags & IORING_POLL_ADD_MULTI) && (req->flags & REQ_F_CQE_SKIP))
+		return -EINVAL;
+
+	poll->events = io_poll_parse_events(sqe, flags);
+	return 0;
+}
+
+int io_poll_add(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_poll *poll = io_kiocb_to_cmd(req, struct io_poll);
+	struct io_poll_table ipt;
+	int ret;
+
+	ipt.pt._qproc = io_poll_queue_proc;
+
+	/*
+	 * If sqpoll or single issuer, there is no contention for ->uring_lock
+	 * and we'll end up holding it in tw handlers anyway.
+	 */
+	if (req->ctx->flags & (IORING_SETUP_SQPOLL|IORING_SETUP_SINGLE_ISSUER))
+		req->flags |= REQ_F_HASH_LOCKED;
+
+	ret = __io_arm_poll_handler(req, poll, &ipt, poll->events, issue_flags);
+	if (ret > 0) {
+		io_req_set_res(req, ipt.result_mask, 0);
+		return IOU_OK;
+	}
+	return ret ?: IOU_ISSUE_SKIP_COMPLETE;
+}
+
+int io_poll_remove(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_poll_update *poll_update = io_kiocb_to_cmd(req, struct io_poll_update);
+	struct io_cancel_data cd = { .data = poll_update->old_user_data, };
+	struct io_ring_ctx *ctx = req->ctx;
+	struct io_hash_bucket *bucket;
+	struct io_kiocb *preq;
+	int ret2, ret = 0;
+	bool locked = true;
+
+	io_ring_submit_lock(ctx, issue_flags);
+	preq = io_poll_find(ctx, true, &cd, &ctx->cancel_table, &bucket);
+	ret2 = io_poll_disarm(preq);
+	if (bucket)
+		spin_unlock(&bucket->lock);
+	if (!ret2)
+		goto found;
+	if (ret2 != -ENOENT) {
+		ret = ret2;
+		goto out;
+	}
+
+	preq = io_poll_find(ctx, true, &cd, &ctx->cancel_table_locked, &bucket);
+	ret2 = io_poll_disarm(preq);
+	if (bucket)
+		spin_unlock(&bucket->lock);
+	if (ret2) {
+		ret = ret2;
+		goto out;
+	}
+
+found:
+	if (WARN_ON_ONCE(preq->opcode != IORING_OP_POLL_ADD)) {
+		ret = -EFAULT;
+		goto out;
+	}
+
+	if (poll_update->update_events || poll_update->update_user_data) {
+		/* only mask one event flags, keep behavior flags */
+		if (poll_update->update_events) {
+			struct io_poll *poll = io_kiocb_to_cmd(preq, struct io_poll);
+
+			poll->events &= ~0xffff;
+			poll->events |= poll_update->events & 0xffff;
+			poll->events |= IO_POLL_UNMASK;
+		}
+		if (poll_update->update_user_data)
+			preq->cqe.user_data = poll_update->new_user_data;
+
+		ret2 = io_poll_add(preq, issue_flags & ~IO_URING_F_UNLOCKED);
+		/* successfully updated, don't complete poll request */
+		if (!ret2 || ret2 == -EIOCBQUEUED)
+			goto out;
+	}
+
+	req_set_fail(preq);
+	io_req_set_res(preq, -ECANCELED, 0);
+	io_req_task_complete(preq, &locked);
+out:
+	io_ring_submit_unlock(ctx, issue_flags);
+	if (ret < 0) {
+		req_set_fail(req);
+		return ret;
+	}
+	/* complete update request, we're done with it */
+	io_req_set_res(req, ret, 0);
+	return IOU_OK;
+}
+
+void io_apoll_cache_free(struct io_cache_entry *entry)
+{
+	kfree(container_of(entry, struct async_poll, cache));
+}