blk-mq: don't hold q->sysfs_lock in blk_mq_map_swqueue

stable inclusion
from linux-4.19.176
commit 6ff18507a7c165b90f1fe51822c65d10265f5714

--------------------------------

commit c6ba9333 upstream.

blk_mq_map_swqueue() is called from blk_mq_init_allocated_queue()
and blk_mq_update_nr_hw_queues(). For the former caller, the kobject
isn't exposed to userspace yet. For the latter caller, hctx sysfs entries
and debugfs are un-registered before updating nr_hw_queues.

On the other hand, commit 2f8f1336 ("blk-mq: always free hctx after
request queue is freed") moves freeing hctx into queue's release
handler, so there won't be race with queue release path too.

So don't hold q->sysfs_lock in blk_mq_map_swqueue().

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>