linux-kernel - [PATCH v1 10/11] mm/memory: ignore dirty/accessed/soft-dirty bits in folio_pte

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Date: Mon, 22 Jan 2024 20:41:59 +0100
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org,
	David Hildenbrand <david@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Matthew Wilcox <willy@...radead.org>,
	Ryan Roberts <ryan.roberts@....com>,
	Russell King <linux@...linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Dinh Nguyen <dinguyen@...nel.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	"Aneesh Kumar K.V" <aneesh.kumar@...nel.org>,
	"Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
	Heiko Carstens <hca@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>,
	Sven Schnelle <svens@...ux.ibm.com>,
	"David S. Miller" <davem@...emloft.net>,
	linux-arm-kernel@...ts.infradead.org,
	linuxppc-dev@...ts.ozlabs.org,
	linux-riscv@...ts.infradead.org,
	linux-s390@...r.kernel.org,
	sparclinux@...r.kernel.org
Subject: [PATCH v1 10/11] mm/memory: ignore dirty/accessed/soft-dirty bits in folio_pte_batch()

Let's ignore these bits: they are irrelevant for fork, and will likely
be irrelevant for upcoming users such as page unmapping.

Signed-off-by: David Hildenbrand <david@...hat.com>
---
 mm/memory.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index f563aec85b2a8..341b2be845b6e 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -953,24 +953,30 @@ static __always_inline void __copy_present_ptes(struct vm_area_struct *dst_vma,
 	set_ptes(dst_vma->vm_mm, addr, dst_pte, pte, nr);
 }
 
+static inline pte_t __pte_batch_clear_ignored(pte_t pte)
+{
+	return pte_clear_soft_dirty(pte_mkclean(pte_mkold(pte)));
+}
+
 /*
  * Detect a PTE batch: consecutive (present) PTEs that map consecutive
  * pages of the same folio.
  *
  * All PTEs inside a PTE batch have the same PTE bits set, excluding the PFN.
+ * the accessed bit, dirty bit and soft-dirty bit.
  */
 static inline int folio_pte_batch(struct folio *folio, unsigned long addr,
 		pte_t *start_ptep, pte_t pte, int max_nr)
 {
 	unsigned long folio_end_pfn = folio_pfn(folio) + folio_nr_pages(folio);
 	const pte_t *end_ptep = start_ptep + max_nr;
-	pte_t expected_pte = pte_next_pfn(pte);
+	pte_t expected_pte = __pte_batch_clear_ignored(pte_next_pfn(pte));
 	pte_t *ptep = start_ptep + 1;
 
 	VM_WARN_ON_FOLIO(!pte_present(pte), folio);
 
 	while (ptep != end_ptep) {
-		pte = ptep_get(ptep);
+		pte = __pte_batch_clear_ignored(ptep_get(ptep));
 
 		if (!pte_same(pte, expected_pte))
 			break;
-- 
2.43.0