io_uring: single shot poll removal optimisation

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>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index a36eb6060e7e486569c2a9e4ec1cf24e047e95e4..206066b59b62392f348c39eec70aba7ff154e4c7 100644 (file)
--- 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;
 }