From: Cong Zhang <cong.zhang@oss.qualcomm.com>
Date: Tue, 30 Dec 2025 09:17:05 +0000 (+0800)
Subject: blk-mq: skip CPU offline notify on unmapped hctx
X-Git-Tag: v6.18.4~226
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7d8a5b44b9f2403f874a158498022f936fe7765f;p=thirdparty%2Fkernel%2Fstable.git

blk-mq: skip CPU offline notify on unmapped hctx

[ Upstream commit 10845a105bbcb030647a729f1716c2309da71d33 ]

If an hctx has no software ctx mapped, blk_mq_map_swqueue() never
allocates tags and leaves hctx->tags NULL. The CPU hotplug offline
notifier can still run for that hctx, return early since hctx cannot
hold any requests.

Signed-off-by: Cong Zhang <cong.zhang@oss.qualcomm.com>
Fixes: bf0beec0607d ("blk-mq: drain I/O when all CPUs in a hctx are offline")
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/block/blk-mq.c b/block/blk-mq.c
index ea5f948af7a42..a03f52ab87d64 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3710,7 +3710,7 @@ static int blk_mq_hctx_notify_offline(unsigned int cpu, struct hlist_node *node)
 			struct blk_mq_hw_ctx, cpuhp_online);
 	int ret = 0;
 
-	if (blk_mq_hctx_has_online_cpu(hctx, cpu))
+	if (!hctx->nr_ctx || blk_mq_hctx_has_online_cpu(hctx, cpu))
 		return 0;
 
 	/*