Re: [PATCH v2 3/3] mm: remove folio_test_anon(folio)==false path in __folio_add_anon_rmap()

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On 18.06.24 01:11, Barry Song wrote:
From: Barry Song <v-songbaohua@xxxxxxxx>

The folio_test_anon(folio)==false cases has been relocated to
folio_add_new_anon_rmap(). Additionally, four other callers
consistently pass anonymous folios.

stack 1:
remove_migration_pmd
    -> folio_add_anon_rmap_pmd
      -> __folio_add_anon_rmap

stack 2:
__split_huge_pmd_locked
    -> folio_add_anon_rmap_ptes
       -> __folio_add_anon_rmap

stack 3:
remove_migration_pmd
    -> folio_add_anon_rmap_pmd
       -> __folio_add_anon_rmap (RMAP_LEVEL_PMD)

stack 4:
try_to_merge_one_page
    -> replace_page
      -> folio_add_anon_rmap_pte
        -> __folio_add_anon_rmap

__folio_add_anon_rmap() only needs to handle the cases
folio_test_anon(folio)==true now.
We can remove the !folio_test_anon(folio)) path within
__folio_add_anon_rmap() now.

Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
Tested-by: Shuai Yuan <yuanshuai@xxxxxxxx>
---
  mm/rmap.c | 17 +++--------------
  1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 2b19bb92eda5..ddcdda752982 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1297,23 +1297,12 @@ static __always_inline void __folio_add_anon_rmap(struct folio *folio,
  {
  	int i, nr, nr_pmdmapped = 0;
+ VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
+
  	nr = __folio_add_rmap(folio, page, nr_pages, level, &nr_pmdmapped);
- if (unlikely(!folio_test_anon(folio))) {
-		VM_WARN_ON_FOLIO(!folio_test_locked(folio), folio);
-		/*
-		 * For a PTE-mapped large folio, we only know that the single
-		 * PTE is exclusive. Further, __folio_set_anon() might not get
-		 * folio->index right when not given the address of the head
-		 * page.
-		 */
-		VM_WARN_ON_FOLIO(folio_test_large(folio) &&
-				 level != RMAP_LEVEL_PMD, folio);
-		__folio_set_anon(folio, vma, address,
-				 !!(flags & RMAP_EXCLUSIVE));
-	} else if (likely(!folio_test_ksm(folio))) {
+	if (likely(!folio_test_ksm(folio)))
  		__page_check_anon_rmap(folio, page, vma, address);
-	}
__folio_mod_stat(folio, nr, nr_pmdmapped);

Lovely!

Acked-by: David Hildenbrand <david@xxxxxxxxxx>

--
Cheers,

David / dhildenb





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