block: make block cgroup policies follow bio task association

Implement bio_blkio_cgroup() which returns the blkcg associated with
the bio if exists or %current's blkcg, and use it in blk-throttle and
cfq-iosched propio.  This makes both cgroup policies honor task
association for the bio instead of always assuming %current.

As nobody is using bio_set_task() yet, this doesn't introduce any
behavior change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 9 insertions, 2 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 27d39a810cb6..ee962f327ba5 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -71,12 +71,19 @@ struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
 }
 EXPORT_SYMBOL_GPL(cgroup_to_blkio_cgroup);
 
-struct blkio_cgroup *task_blkio_cgroup(struct task_struct *tsk)
+static struct blkio_cgroup *task_blkio_cgroup(struct task_struct *tsk)
 {
         return container_of(task_subsys_state(tsk, blkio_subsys_id),
                             struct blkio_cgroup, css);
 }
-EXPORT_SYMBOL_GPL(task_blkio_cgroup);
+
+struct blkio_cgroup *bio_blkio_cgroup(struct bio *bio)
+{
+        if (bio && bio->bi_css)
+                return container_of(bio->bi_css, struct blkio_cgroup, css);
+        return task_blkio_cgroup(current);
+}
+EXPORT_SYMBOL_GPL(bio_blkio_cgroup);
 
 static inline void blkio_update_group_weight(struct blkio_group *blkg,
                                              int plid, unsigned int weight)