[PATCH v4 1/3] fs/dcache: Fix incorrect nr_dentry_unused accounting in shrink_dcache_sb()

From: Waiman Long
Date: Wed Sep 12 2018 - 13:36:05 EST

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@xxxxxxxxxxxxxxx

Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>
fs/dcache.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 2e7e8d8..cb515f1 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1202,15 +1202,11 @@ static enum lru_status dentry_lru_isolate_shrink(struct list_head *item,
void shrink_dcache_sb(struct super_block *sb)
- long freed;
do {

- 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);
} while (list_lru_count(&sb->s_dentry_lru) > 0);