1 files changed, 76 insertions, 142 deletions

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 7a97a6c1c09e..a16b5632ce6f 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -77,6 +77,7 @@
 #include <linux/eventpoll.h>
 #include <linux/fs_struct.h>
 #include <linux/splice.h>
+#include <linux/task_work.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/io_uring.h>
@@ -291,7 +292,6 @@ struct io_ring_ctx {
 
 	struct {
 		spinlock_t		completion_lock;
-		struct llist_head	poll_llist;
 
 		/*
 		 * ->poll_list is protected by the ctx->uring_lock for
@@ -558,10 +558,6 @@ struct io_kiocb {
 	};
 
 	struct io_async_ctx		*io;
-	/*
-	 * llist_node is only used for poll deferred completions
-	 */
-	struct llist_node		llist_node;
 	bool				needs_fixed_file;
 	u8				opcode;
 
@@ -579,7 +575,17 @@ struct io_kiocb {
 
 	struct list_head	inflight_entry;
 
-	struct io_wq_work	work;
+	union {
+		/*
+		 * Only commands that never go async can use the below fields,
+		 * obviously. Right now only IORING_OP_POLL_ADD uses them.
+		 */
+		struct {
+			struct task_struct	*task;
+			struct callback_head	task_work;
+		};
+		struct io_wq_work	work;
+	};
 };
 
 #define IO_PLUG_THRESHOLD		2
@@ -774,10 +780,10 @@ static int __io_sqe_files_update(struct io_ring_ctx *ctx,
 static int io_grab_files(struct io_kiocb *req);
 static void io_ring_file_ref_flush(struct fixed_file_data *data);
 static void io_cleanup_req(struct io_kiocb *req);
-static int io_file_get(struct io_submit_state *state,
-		       struct io_kiocb *req,
-		       int fd, struct file **out_file,
-		       bool fixed);
+static int io_file_get(struct io_submit_state *state, struct io_kiocb *req,
+		       int fd, struct file **out_file, bool fixed);
+static void __io_queue_sqe(struct io_kiocb *req,
+			   const struct io_uring_sqe *sqe);
 
 static struct kmem_cache *req_cachep;
 
@@ -848,7 +854,6 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
 	mutex_init(&ctx->uring_lock);
 	init_waitqueue_head(&ctx->wait);
 	spin_lock_init(&ctx->completion_lock);
-	init_llist_head(&ctx->poll_llist);
 	INIT_LIST_HEAD(&ctx->poll_list);
 	INIT_LIST_HEAD(&ctx->defer_list);
 	INIT_LIST_HEAD(&ctx->timeout_list);
@@ -1081,24 +1086,19 @@ static inline bool io_should_trigger_evfd(struct io_ring_ctx *ctx)
 		return false;
 	if (!ctx->eventfd_async)
 		return true;
-	return io_wq_current_is_worker() || in_interrupt();
+	return io_wq_current_is_worker();
 }
 
-static void __io_cqring_ev_posted(struct io_ring_ctx *ctx, bool trigger_ev)
+static void io_cqring_ev_posted(struct io_ring_ctx *ctx)
 {
 	if (waitqueue_active(&ctx->wait))
 		wake_up(&ctx->wait);
 	if (waitqueue_active(&ctx->sqo_wait))
 		wake_up(&ctx->sqo_wait);
-	if (trigger_ev)
+	if (io_should_trigger_evfd(ctx))
 		eventfd_signal(ctx->cq_ev_fd, 1);
 }
 
-static void io_cqring_ev_posted(struct io_ring_ctx *ctx)
-{
-	__io_cqring_ev_posted(ctx, io_should_trigger_evfd(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)
 {
@@ -3548,18 +3548,27 @@ out:
 #endif
 }
 
-static void io_poll_remove_one(struct io_kiocb *req)
+static bool io_poll_remove_one(struct io_kiocb *req)
 {
 	struct io_poll_iocb *poll = &req->poll;
+	bool do_complete = false;
 
 	spin_lock(&poll->head->lock);
 	WRITE_ONCE(poll->canceled, true);
 	if (!list_empty(&poll->wait.entry)) {
 		list_del_init(&poll->wait.entry);
-		io_queue_async_work(req);
+		do_complete = true;
 	}
 	spin_unlock(&poll->head->lock);
 	hash_del(&req->hash_node);
+	if (do_complete) {
+		io_cqring_fill_event(req, -ECANCELED);
+		io_commit_cqring(req->ctx);
+		req->flags |= REQ_F_COMP_LOCKED;
+		io_put_req(req);
+	}
+
+	return do_complete;
 }
 
 static void io_poll_remove_all(struct io_ring_ctx *ctx)
@@ -3577,6 +3586,8 @@ static void io_poll_remove_all(struct io_ring_ctx *ctx)
 			io_poll_remove_one(req);
 	}
 	spin_unlock_irq(&ctx->completion_lock);
+
+	io_cqring_ev_posted(ctx);
 }
 
 static int io_poll_cancel(struct io_ring_ctx *ctx, __u64 sqe_addr)
@@ -3586,10 +3597,11 @@ static int io_poll_cancel(struct io_ring_ctx *ctx, __u64 sqe_addr)
 
 	list = &ctx->cancel_hash[hash_long(sqe_addr, ctx->cancel_hash_bits)];
 	hlist_for_each_entry(req, list, hash_node) {
-		if (sqe_addr == req->user_data) {
-			io_poll_remove_one(req);
+		if (sqe_addr != req->user_data)
+			continue;
+		if (io_poll_remove_one(req))
 			return 0;
-		}
+		return -EALREADY;
 	}
 
 	return -ENOENT;
@@ -3639,92 +3651,28 @@ static void io_poll_complete(struct io_kiocb *req, __poll_t mask, int error)
 	io_commit_cqring(ctx);
 }
 
-static void io_poll_complete_work(struct io_wq_work **workptr)
+static void io_poll_task_handler(struct io_kiocb *req, struct io_kiocb **nxt)
 {
-	struct io_wq_work *work = *workptr;
-	struct io_kiocb *req = container_of(work, struct io_kiocb, work);
-	struct io_poll_iocb *poll = &req->poll;
-	struct poll_table_struct pt = { ._key = poll->events };
 	struct io_ring_ctx *ctx = req->ctx;
-	struct io_kiocb *nxt = NULL;
-	__poll_t mask = 0;
-	int ret = 0;
-
-	if (work->flags & IO_WQ_WORK_CANCEL) {
-		WRITE_ONCE(poll->canceled, true);
-		ret = -ECANCELED;
-	} else if (READ_ONCE(poll->canceled)) {
-		ret = -ECANCELED;
-	}
-
-	if (ret != -ECANCELED)
-		mask = vfs_poll(poll->file, &pt) & poll->events;
 
-	/*
-	 * Note that ->ki_cancel callers also delete iocb from active_reqs after
-	 * calling ->ki_cancel.  We need the ctx_lock roundtrip here to
-	 * synchronize with them.  In the cancellation case the list_del_init
-	 * itself is not actually needed, but harmless so we keep it in to
-	 * avoid further branches in the fast path.
-	 */
 	spin_lock_irq(&ctx->completion_lock);
-	if (!mask && ret != -ECANCELED) {
-		add_wait_queue(poll->head, &poll->wait);
-		spin_unlock_irq(&ctx->completion_lock);
-		return;
-	}
 	hash_del(&req->hash_node);
-	io_poll_complete(req, mask, ret);
-	spin_unlock_irq(&ctx->completion_lock);
-
-	io_cqring_ev_posted(ctx);
-
-	if (ret < 0)
-		req_set_fail_links(req);
-	io_put_req_find_next(req, &nxt);
-	if (nxt)
-		io_wq_assign_next(workptr, nxt);
-}
-
-static void __io_poll_flush(struct io_ring_ctx *ctx, struct llist_node *nodes)
-{
-	struct io_kiocb *req, *tmp;
-	struct req_batch rb;
-
-	rb.to_free = rb.need_iter = 0;
-	spin_lock_irq(&ctx->completion_lock);
-	llist_for_each_entry_safe(req, tmp, nodes, llist_node) {
-		hash_del(&req->hash_node);
-		io_poll_complete(req, req->result, 0);
-
-		if (refcount_dec_and_test(&req->refs) &&
-		    !io_req_multi_free(&rb, req)) {
-			req->flags |= REQ_F_COMP_LOCKED;
-			io_free_req(req);
-		}
-	}
+	io_poll_complete(req, req->result, 0);
+	req->flags |= REQ_F_COMP_LOCKED;
+	io_put_req_find_next(req, nxt);
 	spin_unlock_irq(&ctx->completion_lock);
 
 	io_cqring_ev_posted(ctx);
-	io_free_req_many(ctx, &rb);
-}
-
-static void io_poll_flush(struct io_wq_work **workptr)
-{
-	struct io_kiocb *req = container_of(*workptr, struct io_kiocb, work);
-	struct llist_node *nodes;
-
-	nodes = llist_del_all(&req->ctx->poll_llist);
-	if (nodes)
-		__io_poll_flush(req->ctx, nodes);
 }
 
-static void io_poll_trigger_evfd(struct io_wq_work **workptr)
+static void io_poll_task_func(struct callback_head *cb)
 {
-	struct io_kiocb *req = container_of(*workptr, struct io_kiocb, work);
+	struct io_kiocb *req = container_of(cb, struct io_kiocb, task_work);
+	struct io_kiocb *nxt = NULL;
 
-	eventfd_signal(req->ctx->cq_ev_fd, 1);
-	io_put_req(req);
+	io_poll_task_handler(req, &nxt);
+	if (nxt)
+		__io_queue_sqe(nxt, NULL);
 }
 
 static int io_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
@@ -3732,8 +3680,8 @@ static int io_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
 {
 	struct io_kiocb *req = wait->private;
 	struct io_poll_iocb *poll = &req->poll;
-	struct io_ring_ctx *ctx = req->ctx;
 	__poll_t mask = key_to_poll(key);
+	struct task_struct *tsk;
 
 	/* for instances that support it check for an event match first: */
 	if (mask && !(mask & poll->events))
@@ -3741,46 +3689,11 @@ static int io_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
 
 	list_del_init(&poll->wait.entry);
 
-	/*
-	 * Run completion inline if we can. We're using trylock here because
-	 * we are violating the completion_lock -> poll wq lock ordering.
-	 * If we have a link timeout we're going to need the completion_lock
-	 * for finalizing the request, mark us as having grabbed that already.
-	 */
-	if (mask) {
-		unsigned long flags;
-
-		if (llist_empty(&ctx->poll_llist) &&
-		    spin_trylock_irqsave(&ctx->completion_lock, flags)) {
-			bool trigger_ev;
-
-			hash_del(&req->hash_node);
-			io_poll_complete(req, mask, 0);
-
-			trigger_ev = io_should_trigger_evfd(ctx);
-			if (trigger_ev && eventfd_signal_count()) {
-				trigger_ev = false;
-				req->work.func = io_poll_trigger_evfd;
-			} else {
-				req->flags |= REQ_F_COMP_LOCKED;
-				io_put_req(req);
-				req = NULL;
-			}
-			spin_unlock_irqrestore(&ctx->completion_lock, flags);
-			__io_cqring_ev_posted(ctx, trigger_ev);
-		} else {
-			req->result = mask;
-			req->llist_node.next = NULL;
-			/* if the list wasn't empty, we're done */
-			if (!llist_add(&req->llist_node, &ctx->poll_llist))
-				req = NULL;
-			else
-				req->work.func = io_poll_flush;
-		}
-	}
-	if (req)
-		io_queue_async_work(req);
-
+	tsk = req->task;
+	req->result = mask;
+	init_task_work(&req->task_work, io_poll_task_func);
+	task_work_add(tsk, &req->task_work, true);
+	wake_up_process(tsk);
 	return 1;
 }
 
@@ -3828,6 +3741,9 @@ static int io_poll_add_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe
 
 	events = READ_ONCE(sqe->poll_events);
 	poll->events = demangle_poll(events) | EPOLLERR | EPOLLHUP;
+
+	/* task will wait for requests on exit, don't need a ref */
+	req->task = current;
 	return 0;
 }
 
@@ -3839,7 +3755,6 @@ static int io_poll_add(struct io_kiocb *req, struct io_kiocb **nxt)
 	bool cancel = false;
 	__poll_t mask;
 
-	INIT_IO_WORK(&req->work, io_poll_complete_work);
 	INIT_HLIST_NODE(&req->hash_node);
 
 	poll->head = NULL;
@@ -5268,6 +5183,8 @@ static int io_sq_thread(void *data)
 			if (!list_empty(&ctx->poll_list) ||
 			    (!time_after(jiffies, timeout) && ret != -EBUSY &&
 			    !percpu_ref_is_dying(&ctx->refs))) {
+				if (current->task_works)
+					task_work_run();
 				cond_resched();
 				continue;
 			}
@@ -5299,6 +5216,10 @@ static int io_sq_thread(void *data)
 					finish_wait(&ctx->sqo_wait, &wait);
 					break;
 				}
+				if (current->task_works) {
+					task_work_run();
+					continue;
+				}
 				if (signal_pending(current))
 					flush_signals(current);
 				schedule();
@@ -5318,6 +5239,9 @@ static int io_sq_thread(void *data)
 		timeout = jiffies + ctx->sq_thread_idle;
 	}
 
+	if (current->task_works)
+		task_work_run();
+
 	set_fs(old_fs);
 	if (cur_mm) {
 		unuse_mm(cur_mm);
@@ -5382,8 +5306,13 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
 	struct io_rings *rings = ctx->rings;
 	int ret = 0;
 
-	if (io_cqring_events(ctx, false) >= min_events)
-		return 0;
+	do {
+		if (io_cqring_events(ctx, false) >= min_events)
+			return 0;
+		if (!current->task_works)
+			break;
+		task_work_run();
+	} while (1);
 
 	if (sig) {
 #ifdef CONFIG_COMPAT
@@ -5403,6 +5332,8 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
 	do {
 		prepare_to_wait_exclusive(&ctx->wait, &iowq.wq,
 						TASK_INTERRUPTIBLE);
+		if (current->task_works)
+			task_work_run();
 		if (io_should_wake(&iowq, false))
 			break;
 		schedule();
@@ -6711,6 +6642,9 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
 	int submitted = 0;
 	struct fd f;
 
+	if (current->task_works)
+		task_work_run();
+
 	if (flags & ~(IORING_ENTER_GETEVENTS | IORING_ENTER_SQ_WAKEUP))
 		return -EINVAL;