[PATCH 6/7] io_uring: single shot poll removal optimisation

Pavel Begunkov
2021-12-15T22:09:10Z

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>
---
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 d59d3fa93c9c..20feca3d86ae 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;
}

--
2.34.0