FAILED: patch "[PATCH] io_uring: add reschedule point to handle_tw_list()" failed to apply to 5.15-stable tree

[<gregkh@linuxfoundation.org>]

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 f58680085478dd292435727210122960d38e8014
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '1678099737150217@kroah.com' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

f58680085478 ("io_uring: add reschedule point to handle_tw_list()")
c6dd763c2460 ("io_uring: trace task_work_run")
3a0c037b0e16 ("io_uring: batch task_work")
f88262e60bb9 ("io_uring: lockless task list")
ed5ccb3beeba ("io_uring: remove priority tw list optimisation")
4a0fef62788b ("io_uring: optimize io_uring_task layout")
253993210bd8 ("io_uring: introduce locking helpers for CQE posting")
305bef988708 ("io_uring: hide eventfd assumptions in eventfd paths")
d9dee4302a7c ("io_uring: remove ->flush_cqes optimisation")
a830ffd28780 ("io_uring: move io_eventfd_signal()")
9046c6415be6 ("io_uring: reshuffle io_uring/io_uring.h")
d142c3ec8d16 ("io_uring: remove extra io_commit_cqring()")
68494a65d0e2 ("io_uring: introduce io_req_cqe_overflow()")
faf88dde060f ("io_uring: don't inline __io_get_cqe()")
d245bca6375b ("io_uring: don't expose io_fill_cqe_aux()")
6a02e4be8187 ("io_uring: inline ->registered_rings")
aa1e90f64ee5 ("io_uring: move small helpers to headers")
aa1e90f64ee5 ("io_uring: move small helpers to headers")
aa1e90f64ee5 ("io_uring: move small helpers to headers")
aa1e90f64ee5 ("io_uring: move small helpers to headers")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f58680085478dd292435727210122960d38e8014 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Fri, 27 Jan 2023 09:50:31 -0700
Subject: [PATCH] io_uring: add reschedule point to handle_tw_list()

If CONFIG_PREEMPT_NONE is set and the task_work chains are long, we
could be running into issues blocking others for too long. Add a
reschedule check in handle_tw_list(), and flush the ctx if we need to
reschedule.

Cc: stable@vger.kernel.org # 5.10+
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index fab581a31dc1..acf6d9680d76 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -1179,10 +1179,16 @@ static unsigned int handle_tw_list(struct llist_node *node,
 			/* if not contended, grab and improve batching */
 			*locked = mutex_trylock(&(*ctx)->uring_lock);
 			percpu_ref_get(&(*ctx)->refs);
-		}
+		} else if (!*locked)
+			*locked = mutex_trylock(&(*ctx)->uring_lock);
 		req->io_task_work.func(req, locked);
 		node = next;
 		count++;
+		if (unlikely(need_resched())) {
+			ctx_flush_and_put(*ctx, locked);
+			*ctx = NULL;
+			cond_resched();
+		}
 	}
 
 	return count;