Re: [f2fs-dev] [PATCH v3] f2fs: avoid race condition for shinker count

[Chao Yu]

On 2020/11/12 13:40, Jaegeuk Kim wrote:

Light reported sometimes shinker gets nat_cnt < dirty_nat_cnt resulting in
wrong do_shinker work. Let's avoid to get stale data by using nat_tree_lock.

Reported-by: Light Hsieh <light.hs...@mediatek.com>
Signed-off-by: Jaegeuk Kim <jaeg...@kernel.org>
---
v3:
  - fix to use NM_I(sbi)

  fs/f2fs/shrinker.c | 6 +++++-
  1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/shrinker.c b/fs/f2fs/shrinker.c
index d66de5999a26..555712ba06d8 100644
--- a/fs/f2fs/shrinker.c
+++ b/fs/f2fs/shrinker.c
@@ -18,7 +18,11 @@ 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;
+       long count;
+
+       down_read(&NM_I(sbi)->nat_tree_lock);
+       count = NM_I(sbi)->nat_cnt - NM_I(sbi)->dirty_nat_cnt;
+       up_read(&NM_I(sbi)->nat_tree_lock);

return count > 0 ? count : 0;

Minor thing,

Just return count is enough? since count should never be smaller than 0.

Anyway,

Reviewed-by: Chao Yu <yuch...@huawei.com>

Thanks,

Thanks,

  }