FAILED: patch "[PATCH] io_uring: move local task_work in exit cancel loop" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-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 <[email protected]>.

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-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x da579f05ef0faada3559e7faddf761c75cdf85e1
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026011957-earful-capillary-a00a@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From da579f05ef0faada3559e7faddf761c75cdf85e1 Mon Sep 17 00:00:00 2001
From: Ming Lei <[email protected]>
Date: Wed, 14 Jan 2026 16:54:05 +0800
Subject: [PATCH] io_uring: move local task_work in exit cancel loop

With IORING_SETUP_DEFER_TASKRUN, task work is queued to ctx->work_llist (local work) rather than the fallback list. During io_ring_exit_work(), io_move_task_work_from_local() was called once before the cancel loop, moving work from work_llist to fallback_llist.

However, task work can be added to work_llist during the cancel loop itself. There are two cases:

1) io_kill_timeouts() is called from io_uring_try_cancel_requests() to cancel pending timeouts, and it adds task work via io_req_queue_tw_complete() for each cancelled timeout:

2) URING_CMD requests like ublk can be completed via io_uring_cmd_complete_in_task() from ublk_queue_rq() during canceling, given ublk request queue is only quiesced when canceling the 1st uring_cmd.

Since io_allowed_defer_tw_run() returns false in io_ring_exit_work() (kworker != submitter_task), io_run_local_work() is never invoked, and the work_llist entries are never processed. This causes io_uring_try_cancel_requests() to loop indefinitely, resulting in 100% CPU usage in kworker threads.

Fix this by moving io_move_task_work_from_local() inside the cancel loop, ensuring any work on work_llist is moved to fallback before each cancel attempt.

index 87a87396e940..b7a077c11c21 100644
@@ -3003,12 +3003,12 @@ static __cold void io_ring_exit_work(struct work_struct *work)
 			mutex_unlock(&ctx->uring_lock);
 		}
 
-		if (ctx->flags & IORING_SETUP_DEFER_TASKRUN)
-			io_move_task_work_from_local(ctx);
-
 		/* The SQPOLL thread never reaches this path */
-		while (io_uring_try_cancel_requests(ctx, NULL, true, false))
+		do {
+			if (ctx->flags & IORING_SETUP_DEFER_TASKRUN)
+				io_move_task_work_from_local(ctx);
 			cond_resched();
+		} while (io_uring_try_cancel_requests(ctx, NULL, true, false));
 
 		if (ctx->sq_data) {
 			struct io_sq_data *sqd = ctx->sq_data;

And here's one for 6.1-stable.

Jens Axboe

From be0dd1628e49608e52adaec6a94c4956702eedd4 Mon Sep 17 00:00:00 2001
From: Ming Lei <[email protected]>
Date: Wed, 14 Jan 2026 16:54:05 +0800
Subject: [PATCH] io_uring: move local task_work in exit cancel loop

Commit da579f05ef0faada3559e7faddf761c75cdf85e1 upstream.

With IORING_SETUP_DEFER_TASKRUN, task work is queued to ctx->work_llist (local work) rather than the fallback list. During io_ring_exit_work(), io_move_task_work_from_local() was called once before the cancel loop, moving work from work_llist to fallback_llist.

However, task work can be added to work_llist during the cancel loop itself. There are two cases:

1) io_kill_timeouts() is called from io_uring_try_cancel_requests() to cancel pending timeouts, and it adds task work via io_req_queue_tw_complete() for each cancelled timeout:

2) URING_CMD requests like ublk can be completed via io_uring_cmd_complete_in_task() from ublk_queue_rq() during canceling, given ublk request queue is only quiesced when canceling the 1st uring_cmd.

Since io_allowed_defer_tw_run() returns false in io_ring_exit_work() (kworker != submitter_task), io_run_local_work() is never invoked, and the work_llist entries are never processed. This causes io_uring_try_cancel_requests() to loop indefinitely, resulting in 100% CPU usage in kworker threads.

Fix this by moving io_move_task_work_from_local() inside the cancel loop, ensuring any work on work_llist is moved to fallback before each cancel attempt.

---
 io_uring/io_uring.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

index 2aae0de6169c..d0d9ff6b87a0 100644
@@ -2867,11 +2867,11 @@ static __cold void io_ring_exit_work(struct work_struct *work)
 	 * as nobody else will be looking for them.
 	 */
 	do {
-		if (ctx->flags & IORING_SETUP_DEFER_TASKRUN)
-			io_move_task_work_from_local(ctx);
-
-		while (io_uring_try_cancel_requests(ctx, NULL, true))
+		do {
+			if (ctx->flags & IORING_SETUP_DEFER_TASKRUN)
+				io_move_task_work_from_local(ctx);
 			cond_resched();
+		} while (io_uring_try_cancel_requests(ctx, NULL, true));
 
 		if (ctx->sq_data) {
 			struct io_sq_data *sqd = ctx->sq_data;

2.51.0

Thanks for both, now queued up!

greg k-h