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blkcg: check pol->cpd_free_fn before free cpd

PATCH In review weiping zhang 4 participants 4 messages Oct 10, 2017

Subsystems (2)
Block layer cgroup blkio
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weiping zhang

author
#0 lore raw

PATCH 1/1 blkcg: check pol->cpd_free_fn before free cpd

check pol->cpd_free_fn() instead of pol->cpd_alloc_fn() when free cpd.

Signed-off-by weiping zhang <[email protected]>
---
 block/blk-cgroup.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
block/blk-cgroup.c +2 -2
index d3f56ba..e7ec676 100644
@@ -1452,7 +1452,7 @@ int blkcg_policy_register(struct blkcg_policy *pol)
 	return 0;
 
 err_free_cpds:
-	if (pol->cpd_alloc_fn) {
+	if (pol->cpd_free_fn) {
 		list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
 			if (blkcg->cpd[pol->plid]) {
 				pol->cpd_free_fn(blkcg->cpd[pol->plid]);

@@ -1492,7 +1492,7 @@ void blkcg_policy_unregister(struct blkcg_policy *pol)
 	/* remove cpds and unregister */
 	mutex_lock(&blkcg_pol_mutex);
 
-	if (pol->cpd_alloc_fn) {
+	if (pol->cpd_free_fn) {
 		list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node) {
 			if (blkcg->cpd[pol->plid]) {
 				pol->cpd_free_fn(blkcg->cpd[pol->plid]);
Signature · 1 line
2.9.4
Reviewed-by on v1 1/1
#1 lore raw

Good catch,

Reviewed-by Johannes Thumshirn <[email protected]>
Signature · 6 lines
Johannes Thumshirn                                          Storage
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maintainer
#2 lore raw
In reply to weiping zhang
Quoted 1 line · weiping zhang

check pol->cpd_free_fn() instead of pol->cpd_alloc_fn() when free cpd.

In practice this shouldn't make a difference, since if you have an alloc_fn, you better also have a free_fn. I'd argue a better patch would be ensuring that's the case, since the current situation would at least oops and show you there's an issue, but with the patch we'll just leak the memory.

I'll apply it, but would be nice if this was handled a bit more proactively.

Signature · 1 line
Jens Axboe
#3 lore raw
Quoted 12 lines · Jens Axboe
Quoted 1 line · weiping zhang

check pol->cpd_free_fn() instead of pol->cpd_alloc_fn() when free cpd.

In practice this shouldn't make a difference, since if you have an alloc_fn, you better also have a free_fn. I'd argue a better patch would be ensuring that's the case, since the current situation would at least oops and show you there's an issue, but with the patch we'll just leak the memory.

I'll apply it, but would be nice if this was handled a bit more proactively.

Thanks your comments, I'll add a sanity check in blkcg_policy_register function.