[PATCH] f2fs: avoid race condition for shrinker count

[Jaegeuk Kim]

Light reported sometimes shinker gets nat_cnt < dirty_nat_cnt resulting in
wrong do_shinker work. Let's avoid to return insane overflowed value.

Reported-by: Light Hsieh <Light.Hsieh@xxxxxxxxxxxx>
Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
---
 fs/f2fs/shrinker.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/shrinker.c b/fs/f2fs/shrinker.c
index d66de5999a26..75b5b4aaed99 100644
--- a/fs/f2fs/shrinker.c
+++ b/fs/f2fs/shrinker.c
@@ -18,9 +18,9 @@ static unsigned int shrinker_run_no;
 
 static unsigned long __count_nat_entries(struct f2fs_sb_info *sbi)
 {
-	long count = NM_I(sbi)->nat_cnt - NM_I(sbi)->dirty_nat_cnt;
-
-	return count > 0 ? count : 0;
+	if (NM_I(sbi)->nat_cnt > NM_I(sbi)->dirty_nat_cnt)
+		return NM_I(sbi)->nat_cnt - NM_I(sbi)->dirty_nat_cnt;
+	return 0;
 }
 
 static unsigned long __count_free_nids(struct f2fs_sb_info *sbi)
-- 
2.29.2.454.gaff20da3a2-goog



>  
>  	return count > 0 ? count : 0;
>  }
> -- 
> 2.29.2.299.gdc1121823c-goog
> 
> 
> 
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