wbt_init() can be called from sysfs attribute and wbt_enable_default(),
however the lock order are inversely.

- queue_wb_lat_store() freeze queue first, and then wbt_init() hold
  rq_qos_mutex. In this case queue will be freezed again inside
  rq_qos_add(), however, in this case freeze queue recursivly is
  inoperative;
- wbt_enable_default() from elevator switch will hold rq_qos_mutex
  first, and then rq_qos_add() will freeze queue;

Fix this problem by converting to use new helper rq_qos_add_freezed() in
wbt_init(), and for wbt_enable_default(), freeze queue before calling
wbt_init().

Fixes: a13bd91 ("block/rq_qos: protect rq_qos apis with a new lock")
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>

Like wbt, rq_qos_add() can be called from two path and the lock order
are inversely:

- From ioc_qos_write(), queue is already freezed before rq_qos_add();
- From ioc_cost_model_write(), rq_qos_add() is called directly;

Fix this problem by converting to use blkg_conf_open_bdev_frozen()
from ioc_cost_model_write(), then since all rq_qos_add() callers
already freeze queue, convert to use rq_qos_add_freezed.

Signed-off-by: Yu Kuai <yukuai@fnnas.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>

…ueue

Currently blk-iolatency will hold rq_qos_mutex first and then call
rq_qos_add() to freeze queue.

Fix this problem by converting to use blkg_conf_open_bdev_frozen()
from iolatency_set_limit(), and convert to use rq_qos_add_freezed().

Signed-off-by: Yu Kuai <yukuai@fnnas.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>