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 ea5f948af7a42dc87d17465e6ba45e579b445e32..a03f52ab87d64dfc05c7c5380014ff291aa83879 100644 (file)
--- 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;
 
        /*