FAILED: patch "[PATCH] io_uring/timeout: count cancelled timeouts in cq_timeouts" failed to apply to 5.10-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 5.10-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-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x 1c8b49851543f41fc8bb18bcd1f15cc93d14b530
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261107063043-failed-5.10-1c8b49851543@kernel.org' --subject-prefix 'PATCH 5.10.y' 'HEAD^..'

Thanks,
Sasha

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

From 1c8b49851543f41fc8bb18bcd1f15cc93d14b530 Mon Sep 17 00:00:00 2001
From: Cheng Yongkang <teel4res@gmail.com>
Date: Thu, 29 Oct 2026 07:12:20 -0700
Subject: [PATCH] io_uring/timeout: count cancelled timeouts in cq_timeouts

io_timeout_cancel() posts the cancelled timeout's -ECANCELED CQE without
advancing ctx->cq_timeouts.  io_timeout_fn() and io_kill_timeout()
advance it for every timeout CQE they post, and io_flush_timeouts()
computes the number of non-timeout completions as

    seq = cached_cq_tail - cq_timeouts

to compare against each off timeout's target_seq.  The cancelled
timeout's CQE is therefore counted as a regular completion, so every
cancellation makes an already armed off timeout fire one completion
early.

A ring with a keep-alive timeout of off=4 completes it after two NOPs
when one off=100 victim is cancelled through IORING_OP_ASYNC_CANCEL, and
before any NOP when two victims are cancelled.  The cancel CQE should
count, but the cancelled timeouts' -ECANCELED CQEs must not: the
expected counts are three and two NOPs respectively.

Advance cq_timeouts when io_timeout_extract() succeeds, under
timeout_lock and before the -ECANCELED completion is queued, matching
io_timeout_fn() and io_kill_timeout().  The -ENOENT and -EALREADY paths
post no new timeout CQE and keep their accounting.  Both the
ASYNC_CANCEL and the TIMEOUT_REMOVE path go through io_timeout_cancel().

Fixes: bfe68a221905 ("io_uring: off timeouts based only on completions")
Cc: stable@vger.kernel.org
Assisted-by: LLM
Signed-off-by: Cheng Yongkang <teel4res@gmail.com>
Link: https://patch.msgid.link/179328314078.648427.13761781546953594668@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 io_uring/timeout.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/io_uring/timeout.c b/io_uring/timeout.c
index 8a2108aa14ae7..fa7b0d9a81d69 100644
--- a/io_uring/timeout.c
+++ b/io_uring/timeout.c
@@ -370,6 +370,9 @@ int io_timeout_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd)
 
 	raw_spin_lock_irq(&ctx->timeout_lock);
 	req = io_timeout_extract(ctx, cd);
+	if (!IS_ERR(req))
+		atomic_set(&ctx->cq_timeouts,
+			   atomic_read(&ctx->cq_timeouts) + 1);
 	raw_spin_unlock_irq(&ctx->timeout_lock);
 
 	if (IS_ERR(req))
-- 
2.53.0