linux-kernel - [PATCH RFC 2/3] mm: do_swap_page: use folio_add_new_anon_rmap() if folio_test

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Date: Thu, 13 Jun 2024 12:07:20 +1200
From: Barry Song <21cnbao@...il.com>
To: david@...hat.com,
	akpm@...ux-foundation.org,
	linux-mm@...ck.org
Cc: chrisl@...nel.org,
	linux-kernel@...r.kernel.org,
	mhocko@...e.com,
	ryan.roberts@....com,
	baolin.wang@...ux.alibaba.com,
	yosryahmed@...gle.com,
	shy828301@...il.com,
	surenb@...gle.com,
	v-songbaohua@...o.com,
	willy@...radead.org,
	ying.huang@...el.com,
	yuzhao@...gle.com
Subject: [PATCH RFC 2/3] mm: do_swap_page: use folio_add_new_anon_rmap() if folio_test_anon(folio)==false

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

For the !folio_test_anon(folio) case, we can now invoke folio_add_new_anon_rmap()
with the rmap flags set to either EXCLUSIVE or non-EXCLUSIVE. This action will
suppress the VM_WARN_ON_FOLIO check within __folio_add_anon_rmap() while initiating
the process of bringing up mTHP swapin.

 static __always_inline void __folio_add_anon_rmap(struct folio *folio,
                 struct page *page, int nr_pages, struct vm_area_struct *vma,
                 unsigned long address, rmap_t flags, enum rmap_level level)
 {
         ...
         if (unlikely(!folio_test_anon(folio))) {
                 VM_WARN_ON_FOLIO(folio_test_large(folio) &&
                                  level != RMAP_LEVEL_PMD, folio);
         }
         ...
 }

It also enhances the code’s readability.

Suggested-by: David Hildenbrand <david@...hat.com>
Signed-off-by: Barry Song <v-songbaohua@...o.com>
---
 mm/memory.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/memory.c b/mm/memory.c
index 2f94921091fb..9c962f62f928 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4339,6 +4339,8 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 	if (unlikely(folio != swapcache && swapcache)) {
 		folio_add_new_anon_rmap(folio, vma, address, RMAP_EXCLUSIVE);
 		folio_add_lru_vma(folio, vma);
+	} else if (!folio_test_anon(folio)) {
+		folio_add_new_anon_rmap(folio, vma, address, rmap_flags);
 	} else {
 		folio_add_anon_rmap_ptes(folio, page, nr_pages, vma, address,
 					rmap_flags);
-- 
2.34.1