Re: FAILED: patch "[PATCH] io_uring: treat -EAGAIN for REQ_F_NOWAIT as final for io-wq" failed to apply to 5.15-stable tree

[Jens Axboe <axboe@kernel.dk>]

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On 7/23/23 6:54 AM, gregkh@linuxfoundation.org wrote:
> 
> The patch below does not apply to the 5.15-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.
> 
> To reproduce the conflict and resubmit, you may use the following commands:
> 
> git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
> git checkout FETCH_HEAD
> git cherry-pick -x a9be202269580ca611c6cebac90eaf1795497800
> # <resolve conflicts, build, test, etc.>
> git commit -s
> git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2023072352-cage-carnage-b38a@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Here's a tested backport for 5.10-stable and 5.15-stable. Thanks!

-- 
Jens Axboe


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From 7e1a56ef1480fede35eaca84b9e5fcd2cfb99e5a Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Mon, 24 Jul 2023 12:27:37 -0600
Subject: [PATCH] io_uring: treat -EAGAIN for REQ_F_NOWAIT as final for io-wq

Commit a9be202269580ca611c6cebac90eaf1795497800 upstream.

io-wq assumes that an issue is blocking, but it may not be if the
request type has asked for a non-blocking attempt. If we get
-EAGAIN for that case, then we need to treat it as a final result
and not retry or arm poll for it.

Cc: stable@vger.kernel.org # 5.10+
Link: https://github.com/axboe/liburing/issues/897
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 io_uring/io_uring.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index eae7a3d89397..0d80dcd0ac32 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -7055,6 +7055,14 @@ static void io_wq_submit_work(struct io_wq_work *work)
 			 */
 			if (ret != -EAGAIN || !(req->ctx->flags & IORING_SETUP_IOPOLL))
 				break;
+
+			/*
+			 * If REQ_F_NOWAIT is set, then don't wait or retry with
+			 * poll. -EAGAIN is final for that case.
+			 */
+			if (req->flags & REQ_F_NOWAIT)
+				break;
+
 			cond_resched();
 		} while (1);
 	}
-- 
2.40.1