[PATCH v2] blkcg: add sanity check for blkcg policy operations

[weiping zhang <zhangweiping@didichuxing.com>]

blkcg policy should keep cpd/pd's alloc_fn and free_fn in pairs,
otherwise policy would register fail.

Signed-off-by: weiping zhang <zhangweiping@didichuxing.com>
---
 block/blk-cgroup.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index e7ec676..67b01c5 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1419,6 +1419,16 @@ int blkcg_policy_register(struct blkcg_policy *pol)
 	if (i >= BLKCG_MAX_POLS)
 		goto err_unlock;
 
+	/* Make sure cpd_alloc_fn and cpd_free_fn in pairs */
+	if ((pol->cpd_alloc_fn && !pol->cpd_free_fn) ||
+		(!pol->cpd_alloc_fn && pol->cpd_free_fn))
+		goto err_unlock;
+
+	/* Make sure pd_alloc_fn and pd_free_fn in pairs */
+	if ((pol->pd_alloc_fn && !pol->pd_free_fn) ||
+		(!pol->pd_alloc_fn && pol->pd_free_fn))
+		goto err_unlock;
+
 	/* register @pol */
 	pol->plid = i;
 	blkcg_policy[pol->plid] = pol;
-- 
2.9.4