mm/swapfile: refcount block and queue before using blkcg_schedule_throttle()
block devices are refcounted so to ensure once its final user goes away it
can be cleaned up by the lower layers properly. The block device's
request_queue structure is also refcounted, however, if the last
blk_put_queue() is called under atomic context the block layer has
to defer removal.
By refcounting the block device during the use of blkcg_schedule_throttle(),
we ensure ensure two things:
1) the block device remains available during the call
2) we ensure avoid having to deal with the fact we're using the
request_queue structure in atomic context, since the last
blk_put_queue() will be called upon disk_release(), *after*
our own bdput().
This means this code path is *not* going to remove the request_queue
structure, as we are ensuring some later upper layer disk_release()
will be the one to release the request_queue structure for us.
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Omar Sandoval <osandov@fb.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Nicolai Stange <nstange@suse.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: yu kuai <yukuai3@huawei.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
1 file changed
