When running ltp stress test for 7*24 hours, vmscan occasionally emits the
following warning continuously:
mb_cache_scan+0x0/0x3f0 negative objects to delete
nr=-9232265467809300450
....
Trace info shows the freeable(mb_cache_count returns) is -1, which causes
the continuous accumulation and overflow of total_scan.
This patch makes sure that mb_cache_count() not return a negative value,
which makes the mbcache shrinker more robust.
Signed-off-by: Jiang Biao <jiang.biao2@xxxxxxxxxx>
CC: "Theodore Ts'o" <tytso@xxxxxxx>
CC: Eric Biggers <ebiggers@xxxxxxxxxx>
CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
CC: Jan Kara <jack@xxxxxxx>
---
fs/mbcache.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/fs/mbcache.c b/fs/mbcache.c
index b8b8b9c..2a800e3 100644
--- a/fs/mbcache.c
+++ b/fs/mbcache.c
@@ -238,7 +238,11 @@ void mb_cache_entry_delete(struct mb_cache *cache, u32 key, u64 value)
spin_lock(&cache->c_list_lock);
if (!list_empty(&entry->e_list)) {
list_del_init(&entry->e_list);
- cache->c_entry_count--;
+ if (cache->c_entry_count > 0)
+ cache->c_entry_count--;
+ else
+ WARN_ONCE(1, "mbcache: Entry count "
+ "going negative!\n");
atomic_dec(&entry->e_refcnt);
}
spin_unlock(&cache->c_list_lock);
--
2.7.4
