writeback: make bdi->min/max_ratio handling cgroup writeback aware

bdi->min/max_ratio are user-configurable per-bdi knobs which regulate
dirty limit of each bdi.  For cgroup writeback, they need to be
further distributed across wb's (bdi_writeback's) belonging to the
configured bdi.

This patch introduces wb_min_max_ratio() which distributes
bdi->min/max_ratio according to a wb's proportion in the total active
bandwidth of its bdi.

v2: Update wb_min_max_ratio() to fix a bug where both min and max were
    assigned the min value and avoid calculations when possible.

Signed-off-by: Tejun Heo <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Jan Kara <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

0 files changed, 0 insertions, 0 deletions