[Devel] [PATCH RHEL7 COMMIT] blk-cbt: fix in_use check in blk_cbt_release

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-1160.76.1.vz7.189.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-1160.76.1.vz7.189.7
------>
commit 780dad116d89430d5f28ace0476f58280d0df441
Author: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
Date:   Wed Nov 2 11:53:28 2022 +0300

    blk-cbt: fix in_use check in blk_cbt_release
    
    Calling cpt_release_callback on cbt->count != 0 here is really strange
    because cbt_page_alloc would anyway do it on decrementing count to zero,
    but in opposite case where cbt->count == 0 we should call the callback
    but we do not, let's fix it by reversing the condition.
    
    We have a cbt->cache percpu allocation leak detected by kmemleak, which
    might be caused by this uncalled release callback.
    
    https://jira.sw.ru/browse/PSBM-141114
    
    Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
    
    Feature: cbt: changed block tracking (for backup)
---
 block/blk-cbt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk-cbt.c b/block/blk-cbt.c
index 2580ccabaa17..054c73c6ef9f 100644
--- a/block/blk-cbt.c
+++ b/block/blk-cbt.c
@@ -540,7 +540,7 @@ void blk_cbt_release(struct request_queue *q)
 	rcu_assign_pointer(q->cbt, NULL);
 	in_use = cbt->count;
 	spin_unlock(&cbt->lock);
-	if (in_use)
+	if (!in_use)
 		call_rcu(&cbt->rcu, &cbt_release_callback);
 }