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

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

[Arianna Avanzini]

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")
---
 block/blk-cgroup.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 9f97da5..5e2723f 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);
 	}
-- 
2.1.4

Re: [PATCH] block/blk-cgroup.c: free per-blkcg data when freeing the blkcg

[Jens Axboe]

On 07/06/2015 07:08 PM, Arianna Avanzini wrote:
> 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")

Thanks Arianna, applied! Hopefully this is the end of the per-policy 
data issues for 4.2.

-- 
Jens Axboe