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This patch fixes the race be holding q->sysfs_lock. Reviewed-by: Christoph Hellwig Reported-by: Yi Zhang Tested-by: Yi Zhang Signed-off-by: Ming Lei Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/blk-mq.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/block/blk-mq.c b/block/blk-mq.c index 12bb7a49c5ba..c28d6b3088a0 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2314,6 +2314,9 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_= set *set, struct blk_mq_hw_ctx **hctxs =3D q->queue_hw_ctx; =20 blk_mq_sysfs_unregister(q); + + /* protect against switching io scheduler */ + mutex_lock(&q->sysfs_lock); for (i =3D 0; i < set->nr_hw_queues; i++) { int node; =20 @@ -2358,6 +2361,7 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_= set *set, } } q->nr_hw_queues =3D i; + mutex_unlock(&q->sysfs_lock); blk_mq_sysfs_register(q); } =20 --=20 2.14.1