linux-kernel - [PATCH 6.0 847/862] io_uring/net: fix notif cqe reordering

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Date:   Wed, 19 Oct 2022 10:35:34 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Pavel Begunkov <asml.silence@...il.com>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 6.0 847/862] io_uring/net: fix notif cqe reordering

From: Pavel Begunkov <asml.silence@...il.com>

[ upstream commit 108893ddcc4d3aa0a4a02aeb02d478e997001227 ]

send zc is not restricted to !IO_URING_F_UNLOCKED anymore and so
we can't use task-tw ordering trick to order notification cqes
with requests completions. In this case leave it alone and let
io_send_zc_cleanup() flush it.

Cc: stable@...r.kernel.org
Fixes: 53bdc88aac9a2 ("io_uring/notif: order notif vs send CQEs")
Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
Link: https://lore.kernel.org/r/0031f3a00d492e814a4a0935a2029a46d9c9ba06.1664486545.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 io_uring/net.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -1073,8 +1073,14 @@ int io_send_zc(struct io_kiocb *req, uns
 	else if (zc->done_io)
 		ret = zc->done_io;
 
-	io_notif_flush(zc->notif);
-	req->flags &= ~REQ_F_NEED_CLEANUP;
+	/*
+	 * If we're in io-wq we can't rely on tw ordering guarantees, defer
+	 * flushing notif to io_send_zc_cleanup()
+	 */
+	if (!(issue_flags & IO_URING_F_UNLOCKED)) {
+		io_notif_flush(zc->notif);
+		req->flags &= ~REQ_F_NEED_CLEANUP;
+	}
 	io_req_set_res(req, ret, IORING_CQE_F_MORE);
 	return IOU_OK;
 }