[PATCH 2/4] io_uring: simplify linked timeout cancel

[Pavel Begunkov <asml.silence@gmail.com>]

As was done with general timeouts, don't remove linked timeouts from
link_list in io_link_cancel_timeout() unless they were successefully
cancelled with hrtimer_try_to_cancel(). With that it's not needed to
check if there was a race and the timeout got removed before getting
into io_link_timeout_fn().

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 32 +++++++++++---------------------
 1 file changed, 11 insertions(+), 21 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 373b67a252df..8065df90ce98 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1732,6 +1732,7 @@ static bool io_link_cancel_timeout(struct io_kiocb *req)
 
 	ret = hrtimer_try_to_cancel(&io->timer);
 	if (ret != -1) {
+		list_del_init(&req->link_list);
 		io_cqring_fill_event(req, -ECANCELED);
 		io_commit_cqring(ctx);
 		req->flags &= ~REQ_F_LINK_HEAD;
@@ -1747,13 +1748,11 @@ static bool __io_kill_linked_timeout(struct io_kiocb *req)
 	struct io_kiocb *link;
 	bool wake_ev;
 
-	if (list_empty(&req->link_list))
-		return false;
-	link = list_first_entry(&req->link_list, struct io_kiocb, link_list);
-	if (link->opcode != IORING_OP_LINK_TIMEOUT)
+	link = list_first_entry_or_null(&req->link_list, struct io_kiocb,
+					link_list);
+	if (!link || link->opcode != IORING_OP_LINK_TIMEOUT)
 		return false;
 
-	list_del_init(&link->link_list);
 	wake_ev = io_link_cancel_timeout(link);
 	req->flags &= ~REQ_F_LINK_TIMEOUT;
 	return wake_ev;
@@ -5970,27 +5969,18 @@ static enum hrtimer_restart io_link_timeout_fn(struct hrtimer *timer)
 {
 	struct io_timeout_data *data = container_of(timer,
 						struct io_timeout_data, timer);
-	struct io_kiocb *req = data->req;
+	struct io_kiocb *prev, *req = data->req;
 	struct io_ring_ctx *ctx = req->ctx;
-	struct io_kiocb *prev = NULL;
 	unsigned long flags;
 
 	spin_lock_irqsave(&ctx->completion_lock, flags);
+	prev = list_entry(req->link_list.prev, struct io_kiocb, link_list);
 
-	/*
-	 * We don't expect the list to be empty, that will only happen if we
-	 * race with the completion of the linked work.
-	 */
-	if (!list_empty(&req->link_list)) {
-		prev = list_entry(req->link_list.prev, struct io_kiocb,
-				  link_list);
-		if (refcount_inc_not_zero(&prev->refs)) {
-			list_del_init(&req->link_list);
-			prev->flags &= ~REQ_F_LINK_TIMEOUT;
-		} else
-			prev = NULL;
-	}
-
+	if (refcount_inc_not_zero(&prev->refs)) {
+		list_del_init(&req->link_list);
+		prev->flags &= ~REQ_F_LINK_TIMEOUT;
+	} else
+		prev = NULL;
 	spin_unlock_irqrestore(&ctx->completion_lock, flags);
 
 	if (prev) {
-- 
2.24.0