From eb0089d629ba413ebf820733ad11b4b2bed45514 Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <asml.silence@gmail.com>
Date: Wed, 15 Dec 2021 22:08:49 +0000
Subject: [PATCH] io_uring: single shot poll removal optimisation
Git-commit: eb0089d629ba413ebf820733ad11b4b2bed45514
Patch-mainline: v5.17-rc1
References: bsc#1205205

We don't need to poll oneshot request if we've got a desired mask in
io_poll_wake(), task_work will clean it up correctly, but as we already
hold a wq spinlock, we can remove ourselves and save on additional
spinlocking in io_poll_remove_entries().

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/ee170a344a18c9ef36b554d806c64caadfd61c31.1639605189.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, 7 insertions(+), 1 deletion(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index a36eb6060e7e..206066b59b62 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5568,8 +5568,14 @@ static int io_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
 	if (mask && !(mask & poll->events))
 		return 0;
 
-	if (io_poll_get_ownership(req))
+	if (io_poll_get_ownership(req)) {
+		/* optional, saves extra locking for removal in tw handler */
+		if (mask && poll->events & EPOLLONESHOT) {
+			list_del_init(&poll->wait.entry);
+			poll->head = NULL;
+		}
 		__io_poll_execute(req, mask);
+	}
 	return 1;
 }
 
-- 
2.35.3