io_uring: check non-sync defer_list carefully

io_req_defer() do double-checked locking. Use proper helpers for that,
i.e. list_empty_careful().

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 7f10af0..91ddc27 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5031,7 +5031,7 @@ static int io_req_defer(struct io_kiocb *req, const struct io_uring_sqe *sqe)
        int ret;
 
        /* Still need defer if there is pending req in defer list. */
-       if (!req_need_defer(req) && list_empty(&ctx->defer_list))
+       if (!req_need_defer(req) && list_empty_careful(&ctx->defer_list))
                return 0;
 
        if (!req->io && io_alloc_async_ctx(req))