[PATCH v2 5.12] io_uring: maintain CQE order of a failed link

[PATCH v2 5.12] io_uring: maintain CQE order of a failed link

[Pavel Begunkov]

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>
---

v2: expand commit description

 fs/io_uring.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index f8df982017fa..947c9524c53a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6459,8 +6459,6 @@ 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;
@@ -6468,6 +6466,8 @@ static int io_submit_sqe(struct io_ring_ctx *ctx, struct io_kiocb *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);
-- 
2.24.0

Re: [PATCH v2 5.12] io_uring: maintain CQE order of a failed link

[Jens Axboe]

On 3/25/21 1:05 PM, Pavel Begunkov wrote:
> 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.

Applied, thanks.

-- 
Jens Axboe