scsi: make sure that request queue queiesce and unquiesce balanced

scsi: make sure that request queue queiesce and unquiesce balanced

For fixing queue quiesce race between driver and block layer(elevator
switch, update nr_requests, ...), we need to support concurrent quiesce
and unquiesce, which requires the two call balanced.

It isn't easy to audit that in all scsi drivers, especially the two may
be called from different contexts, so do it in scsi core with one
per-device atomic variable to balance quiesce and unquiesce.

Reported-by: Yi Zhang <yi.zhang@redhat.com>
Fixes: e70feb8b3e68 ("blk-mq: support concurrent queue quiesce/unquiesce")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20211109071144.181581-4-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>