make-sure-c_entry_count-does-not-get-decremented-past-zero

   1 mbcache: make sure c_entry_count is not decremented past zero
   2
   3 From: Jiang Biao <jiang.biao2@zte.com.cn>
   4
   5 Signed-off-by: Jiang Biao <jiang.biao2@zte.com.cn>
   6 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
   7 CC: Eric Biggers <ebiggers@google.com>
   8 CC: Andrew Morton <akpm@linux-foundation.org>
   9 CC: Jan Kara <jack@suse.cz>
  10 ---
  11  fs/mbcache.c | 4 +++-
  12  1 file changed, 3 insertions(+), 1 deletion(-)
  13
  14 diff --git a/fs/mbcache.c b/fs/mbcache.c
  15 index 0851af5c1c3d..f2f15b747bed 100644
  16 --- a/fs/mbcache.c
  17 +++ b/fs/mbcache.c
  18 @@ -239,7 +239,9 @@ void mb_cache_entry_delete(struct mb_cache *cache, u32 key, u64 value)
  19                         spin_lock(&cache->c_list_lock);
  20                         if (!list_empty(&entry->e_list)) {
  21                                 list_del_init(&entry->e_list);
  22 -                               cache->c_entry_count--;
  23 +                               if (!WARN_ONCE(cache->c_entry_count == 0,
  24 +               "mbcache: attempt to decrement c_entry_count past zero"))
  25 +                                       cache->c_entry_count--;
  26                                 atomic_dec(&entry->e_refcnt);
  27                         }
  28                         spin_unlock(&cache->c_list_lock);