linux-kernel - [PATCH v2 3/3] mm: remove folio_test_anon(folio)==false path in __folio_add_anon

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Message-Id: <20240617231137.80726-4-21cnbao@gmail.com>
Date: Tue, 18 Jun 2024 11:11:37 +1200
From: Barry Song <21cnbao@...il.com>
To: akpm@...ux-foundation.org,
	david@...hat.com,
	linux-mm@...ck.org
Cc: baolin.wang@...ux.alibaba.com,
	chrisl@...nel.org,
	linux-kernel@...r.kernel.org,
	mhocko@...e.com,
	ryan.roberts@....com,
	shy828301@...il.com,
	surenb@...gle.com,
	v-songbaohua@...o.com,
	willy@...radead.org,
	ying.huang@...el.com,
	yosryahmed@...gle.com,
	yuzhao@...gle.com,
	Shuai Yuan <yuanshuai@...o.com>
Subject: [PATCH v2 3/3] mm: remove folio_test_anon(folio)==false path in __folio_add_anon_rmap()

From: Barry Song <v-songbaohua@...o.com>

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@...hat.com>
Signed-off-by: Barry Song <v-songbaohua@...o.com>
Tested-by: Shuai Yuan <yuanshuai@...o.com>
---
 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);
 
-- 
2.34.1