io_uring: fix tw losing poll events

We may never try to process a poll wake and its mask if there was
multiple wake ups racing for queueing up a tw. Force
io_poll_check_events() to update the mask by vfs_poll().

Cc: stable@vger.kernel.org
Fixes: aa43477b04025 ("io_uring: poll rework")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/00344d60f8b18907171178d7cf598de71d127b0b.1668710222.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/poll.c b/io_uring/poll.c
index 90920ab..c34019b 100644 (file)
--- a/io_uring/poll.c
+++ b/io_uring/poll.c
@@ -228,6 +228,13 @@ static int io_poll_check_events(struct io_kiocb *req, bool *locked)
                        return IOU_POLL_DONE;
                if (v & IO_POLL_CANCEL_FLAG)
                        return -ECANCELED;
+               /*
+                * cqe.res contains only events of the first wake up
+                * and all others are be lost. Redo vfs_poll() to get
+                * up to date state.
+                */
+               if ((v & IO_POLL_REF_MASK) != 1)
+                       req->cqe.res = 0;
 
                /* the mask was stashed in __io_poll_execute */
                if (!req->cqe.res) {