[PATCH] erofs(shrinker): return SHRINK_EMPTY if no objects to free

[Chen Linxuan]

Comments in file include/linux/shrinker.h says that
`count_objects` of `struct shrinker` should return SHRINK_EMPTY
when there are no objects to free.

> If there are no objects to free, it should return SHRINK_EMPTY,
> while 0 is returned in cases of the number of freeable items cannot
> be determined or shrinker should skip this cache for this time
> (e.g., their number is below shrinkable limit).

Signed-off-by: Chen Linxuan <chenlinxuan@xxxxxxxxxxxxx>
---
 fs/erofs/zutil.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/erofs/zutil.c b/fs/erofs/zutil.c
index 0dd65cefce33..682863fa9e1c 100644
--- a/fs/erofs/zutil.c
+++ b/fs/erofs/zutil.c
@@ -243,7 +243,9 @@ void erofs_shrinker_unregister(struct super_block *sb)
 static unsigned long erofs_shrink_count(struct shrinker *shrink,
 					struct shrink_control *sc)
 {
-	return atomic_long_read(&erofs_global_shrink_cnt);
+	unsigned long count = atomic_long_read(&erofs_global_shrink_cnt);
+
+	return count ? count : SHRINK_EMPTY;
 }
 
 static unsigned long erofs_shrink_scan(struct shrinker *shrink,
-- 
2.43.0