[Devel] [PATCH RHEL7 COMMIT] ms/fs/dcache: Fix incorrect nr_dentry_unused accounting in shrink_dcache_sb()

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-957.21.3.vz7.106.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-957.21.3.vz7.106.3
------>
commit 01ab4015298d9f11b259fd3b5966d023cb923c03
Author: Waiman Long <longman at redhat.com>
Date:   Mon Jul 1 12:37:18 2019 +0300

    ms/fs/dcache: Fix incorrect nr_dentry_unused accounting in shrink_dcache_sb()
    
    The nr_dentry_unused per-cpu counter tracks dentries in both the LRU
    lists and the shrink lists where the DCACHE_LRU_LIST bit is set.
    
    The shrink_dcache_sb() function moves dentries from the LRU list to a
    shrink list and subtracts the dentry count from nr_dentry_unused.  This
    is incorrect as the nr_dentry_unused count will also be decremented in
    shrink_dentry_list() via d_shrink_del().
    
    To fix this double decrement, the decrement in the shrink_dcache_sb()
    function is taken out.
    
    Fixes: 4e717f5c1083 ("list_lru: remove special case function list_lru_dispose_all."
    Cc: stable at kernel.org
    Signed-off-by: Waiman Long <longman at redhat.com>
    Reviewed-by: Dave Chinner <dchinner at redhat.com>
    Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
    
    Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
---
 fs/dcache.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 09a11fbd94ea..50f99faad6a5 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1050,15 +1050,11 @@ static enum lru_status dentry_lru_isolate_shrink(struct list_head *item,
  */
 void shrink_dcache_sb(struct super_block *sb)
 {
-	long freed;
-
 	do {
 		LIST_HEAD(dispose);
 
-		freed = list_lru_walk(&sb->s_dentry_lru,
+		list_lru_walk(&sb->s_dentry_lru,
 			dentry_lru_isolate_shrink, &dispose, 1024);
-
-		this_cpu_sub(nr_dentry_unused, freed);
 		shrink_dentry_list(&dispose);
 		cond_resched();
 	} while (list_lru_count(&sb->s_dentry_lru) > 0);