blk-mq: remap queues when adding/removing hardware queues

blk-mq: remap queues when adding/removing hardware queues

Orabug: 26397427

blk_mq_update_nr_hw_queues() used to remap hardware queues, which is the
behavior that drivers expect. However, commit 4e68a011428a changed
blk_mq_queue_reinit() to not remap queues for the case of CPU
hotplugging, inadvertently making blk_mq_update_nr_hw_queues() not remap
queues as well. This breaks, for example, NBD's multi-connection mode,
leaving the added hardware queues unused. Fix it by making
blk_mq_update_nr_hw_queues() explicitly remap the queues.

Fixes: 4e68a011428a ("blk-mq: don't redistribute hardware queues on a CPU hotplug event")
Reviewed-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
(cherry picked from commit ebe8bddb6e30d7a02775b9972099271fc5910f37)

Conflicts:

	block/blk-mq.c

Signed-off-by: Junxiao Bi <junxiao.bi@oracle.com>
Reviewed-by: Jack Vogel <jack.vogel@oracle.com>