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

Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de <javascript:;>>
Signed-off-by: weiping zhang <zhangweiping@didichuxing.com <javascript:;>>
---
Changes since V4:
 * merge "if(cpd->xxx)" and "if(pd->xxx)" together

Changes since V3:
 * make if more cleaner by using !pold->cpd_alloc_fn ^ !pol->cpd_free_fn

Chagnes since V2:
 * merge blkcg_policy_check_ops into the caller blkcg_policy_register

V1:
 * add blkcg_policy_check_ops to check cpd/pd's alloc_fn and free_fn in
 * pairs.

 block/blk-cgroup.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index e7ec676..4117524 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c

@@ -1419,6 +1419,11 @@ int blkcg_policy_register(struct blkcg_policy *pol)
        if (i >= BLKCG_MAX_POLS)
                goto err_unlock;

+       /* Make sure cpd/pd_alloc_fn and cpd/pd_free_fn in pairs */
+       if ((!pol->cpd_alloc_fn ^ !pol->cpd_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

Hello Jens,