block/blk-cgroup.c: free per-blkcg data when freeing the blkcg

Currently, per-blkcg data is freed each time a policy is deactivated,
that is also upon scheduler switch. However, when switching from a
scheduler implementing a policy which requires per-blkcg data to
another one, that same policy might be active on other devices, and
therefore those same per-blkcg data could be still in use.
This commit lets per-blkcg data be freed when the blkcg is freed
instead of on policy deactivation.

Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com>
Reported-and-tested-by: Michael Kaminsky <kaminsky@cs.cmu.edu>
Fixes: e48453c3 ("block, cgroup: implement policy-specific per-blkcg data")
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 9f97da52d006281b1ab3e2911d85934216e3931a..5e2723f2c6a389fa7df3118c06a68d371017c8d5 100644 (file)
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -822,8 +822,13 @@ static void blkcg_css_free(struct cgroup_subsys_state *css)
 {
        struct blkcg *blkcg = css_to_blkcg(css);
 
-       if (blkcg != &blkcg_root)
+       if (blkcg != &blkcg_root) {
+               int i;
+
+               for (i = 0; i < BLKCG_MAX_POLS; i++)
+                       kfree(blkcg->pd[i]);
                kfree(blkcg);
+       }
 }
 
 static struct cgroup_subsys_state *
@@ -1162,8 +1167,6 @@ void blkcg_deactivate_policy(struct request_queue *q,
 
                kfree(blkg->pd[pol->plid]);
                blkg->pd[pol->plid] = NULL;
-               kfree(blkg->blkcg->pd[pol->plid]);
-               blkg->blkcg->pd[pol->plid] = NULL;
 
                spin_unlock(&blkg->blkcg->lock);
        }