io_uring: fix io_cqring_events()'s noflush

Checking !list_empty(&ctx->cq_overflow_list) around noflush in
io_cqring_events() is racy, because if it fails but a request overflowed
just after that, io_cqring_overflow_flush() still will be called.

Remove the second check, it shouldn't be a problem for performance,
because there is cq_check_overflow bit check just above.

Cc: <stable@vger.kernel.org> # 5.5+
Signed-off-by: Pavel Begunkov <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 c0306f7..f53356c 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2329,7 +2329,7 @@ static unsigned io_cqring_events(struct io_ring_ctx *ctx, bool noflush)
                 * we wake up the task, and the next invocation will flush the
                 * entries. We cannot safely to it from here.
                 */
-               if (noflush && !list_empty(&ctx->cq_overflow_list))
+               if (noflush)
                        return -1U;
 
                io_cqring_overflow_flush(ctx, false, NULL, NULL);