writeback, memcg: Implement cgroup_writeback_by_id()
Implement cgroup_writeback_by_id() which initiates cgroup writeback
from bdi and memcg IDs. This will be used by memcg foreign inode
flushing.
v2: Use wb_get_lookup() instead of wb_get_create() to avoid creating
spurious wbs.
v3: Interpret 0 @nr as 1.25 * nr_dirty to implement best-effort
flushing while avoding possible livelocks.
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2 files changed