From 23a65db83b3f4549e5eee1fb5517c3365f627699 Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <asml.silence@gmail.com>
Date: Tue, 17 Aug 2021 20:28:11 +0100
Subject: [PATCH] io_uring: improve same wq polling
Git-commit: 23a65db83b3f4549e5eee1fb5517c3365f627699
Patch-mainline: v5.15-rc1
References: bsc#1205205

Move earlier the check for whether __io_queue_proc() tries to poll
already polled waitqueue, and do the same for the second poll entry, if
any. Shouldn't really matter, but at least it would have a more
predictable behaviour.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/8cb428cfe8ade0fd055859fabb878db8777d4c2f.1629228203.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>
---
 fs/io_uring.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 6f2668b6b867..71d54841ecbe 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5062,8 +5062,13 @@ static void __io_queue_proc(struct io_poll_iocb *poll, struct io_poll_table *pt,
 	if (unlikely(pt->nr_entries)) {
 		struct io_poll_iocb *poll_one = poll;
 
+		/* double add on the same waitqueue head, ignore */
+		if (poll_one->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;
 		}
@@ -5073,9 +5078,6 @@ static void __io_queue_proc(struct io_poll_iocb *poll, struct io_poll_table *pt,
 		 */
 		if (!(poll_one->events & EPOLLONESHOT))
 			poll_one->events |= EPOLLONESHOT;
-		/* double add on the same waitqueue head, ignore */
-		if (poll_one->head == head)
-			return;
 		poll = kmalloc(sizeof(*poll), GFP_ATOMIC);
 		if (!poll) {
 			pt->error = -ENOMEM;
-- 
2.35.3