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>

1 files changed, 6 insertions, 3 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 9f97da52d006..5e2723f2c6a3 100644
--- 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);
         }