From: Pavel Begunkov <asml.silence@gmail.com>
Date: Thu, 25 Mar 2021 19:05:14 +0000 (+0000)
Subject: io_uring: maintain CQE order of a failed link
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=90b8749022bbdd0c94a13182a78f4903b98fd0d7;p=linux.git

io_uring: maintain CQE order of a failed link

Arguably we want CQEs of linked requests be in a strict order of
submission as it always was. Now if init of a request fails its CQE may
be posted before all prior linked requests including the head of the
link. Fix it by failing it last.

Fixes: de59bc104c24f ("io_uring: fail links more in io_submit_sqe()")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/b7a96b05832e7ab23ad55f84092a2548c4a888b0.1616699075.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 8c5789b96dbb6..54ea561db4a55 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6480,8 +6480,6 @@ static int io_submit_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req,
 	ret = io_init_req(ctx, req, sqe);
 	if (unlikely(ret)) {
 fail_req:
-		io_put_req(req);
-		io_req_complete(req, ret);
 		if (link->head) {
 			/* fail even hard links since we don't submit */
 			link->head->flags |= REQ_F_FAIL_LINK;
@@ -6489,6 +6487,8 @@ fail_req:
 			io_req_complete(link->head, -ECANCELED);
 			link->head = NULL;
 		}
+		io_put_req(req);
+		io_req_complete(req, ret);
 		return ret;
 	}
 	ret = io_req_prep(req, sqe);