Re: [PATCH v2 2/3] mm/damon/paddr: minor refactor of damon_pa_young()

From: Kefeng Wang
Date: Sun Mar 05 2023 - 20:56:58 EST




On 2023/3/6 9:10, Kefeng Wang wrote:


On 2023/3/4 2:39, SeongJae Park wrote:
Hi Kefeng,

On Fri, 3 Mar 2023 16:43:42 +0800 Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote:

Omit three lines by unified folio_put(), and make code more clear.

Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
---
  mm/damon/paddr.c | 11 ++++-------
  1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index 3fda00a0f786..2ef9db0189ca 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -130,24 +130,21 @@ static bool damon_pa_young(unsigned long paddr, unsigned long *folio_sz)
              accessed = false;
          else
              accessed = true;
-        folio_put(folio);
          goto out;

Because you moved 'out' label to not include *folio_sz setting, folio_sz will
not set in this case.  It should be set.
oh, it should be fixed.

      }
      need_lock = !folio_test_anon(folio) || folio_test_ksm(folio);
-    if (need_lock && !folio_trylock(folio)) {
-        folio_put(folio);
-        return false;
-    }

Hi SJ, apart from above issue, it looks that this branch need the folio_size() setting, right?

Thanks

+    if (need_lock && !folio_trylock(folio))
+        goto out;
      rmap_walk(folio, &rwc);
      if (need_lock)
          folio_unlock(folio);
-    folio_put(folio);
-out:
      *folio_sz = folio_size(folio);
+out:
+    folio_put(folio);

Before this change, folio_size() is called after folio_put(). Shouldn't it be
called before folio_put()?  If so, could we make a separate fix for that first,
and then make this change on top of it, so that it can be easily applied to
relevant stable kernels?

Yes, I could separate it, after folio_put(), the folio could be re-allocated and the folio_size calculation is not right.

Thanks,
SJ

      return accessed;
  }
--
2.35.3