linux-kernel - [PATCH 1/2] mm: pgtable: add missing flag and statistics for kernel PTE page

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Message-Id: <f023a6687b9f2109401e7522b727aa4708dc05f1.1706774109.git.zhengqi.arch@bytedance.com>
Date: Thu,  1 Feb 2024 16:05:40 +0800
From: Qi Zheng <zhengqi.arch@...edance.com>
To: akpm@...ux-foundation.org,
	arnd@...db.de
Cc: muchun.song@...ux.dev,
	david@...hat.com,
	willy@...radead.org,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org,
	Qi Zheng <zhengqi.arch@...edance.com>
Subject: [PATCH 1/2] mm: pgtable: add missing flag and statistics for kernel PTE page

For kernel PTE page, we do not need to allocate and initialize its split
ptlock, but as a page table page, it's still necessary to add PG_table
flag and NR_PAGETABLE statistics for it.

Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
---
 include/asm-generic/pgalloc.h |  7 ++++++-
 include/linux/mm.h            | 21 ++++++++++++++++-----
 2 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/include/asm-generic/pgalloc.h b/include/asm-generic/pgalloc.h
index 879e5f8aa5e9..908bd9140ac2 100644
--- a/include/asm-generic/pgalloc.h
+++ b/include/asm-generic/pgalloc.h
@@ -23,6 +23,8 @@ static inline pte_t *__pte_alloc_one_kernel(struct mm_struct *mm)
 
 	if (!ptdesc)
 		return NULL;
+
+	__pagetable_pte_ctor(ptdesc);
 	return ptdesc_address(ptdesc);
 }
 
@@ -46,7 +48,10 @@ static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm)
  */
 static inline void pte_free_kernel(struct mm_struct *mm, pte_t *pte)
 {
-	pagetable_free(virt_to_ptdesc(pte));
+	struct ptdesc *ptdesc = virt_to_ptdesc(pte);
+
+	__pagetable_pte_dtor(ptdesc);
+	pagetable_free(ptdesc);
 }
 
 /**
diff --git a/include/linux/mm.h b/include/linux/mm.h
index e442fd0efdd9..e37db032764e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2922,26 +2922,37 @@ static inline bool ptlock_init(struct ptdesc *ptdesc) { return true; }
 static inline void ptlock_free(struct ptdesc *ptdesc) {}
 #endif /* USE_SPLIT_PTE_PTLOCKS */
 
-static inline bool pagetable_pte_ctor(struct ptdesc *ptdesc)
+static inline void __pagetable_pte_ctor(struct ptdesc *ptdesc)
 {
 	struct folio *folio = ptdesc_folio(ptdesc);
 
-	if (!ptlock_init(ptdesc))
-		return false;
 	__folio_set_pgtable(folio);
 	lruvec_stat_add_folio(folio, NR_PAGETABLE);
+}
+
+static inline bool pagetable_pte_ctor(struct ptdesc *ptdesc)
+{
+	if (!ptlock_init(ptdesc))
+		return false;
+
+	__pagetable_pte_ctor(ptdesc);
 	return true;
 }
 
-static inline void pagetable_pte_dtor(struct ptdesc *ptdesc)
+static inline void __pagetable_pte_dtor(struct ptdesc *ptdesc)
 {
 	struct folio *folio = ptdesc_folio(ptdesc);
 
-	ptlock_free(ptdesc);
 	__folio_clear_pgtable(folio);
 	lruvec_stat_sub_folio(folio, NR_PAGETABLE);
 }
 
+static inline void pagetable_pte_dtor(struct ptdesc *ptdesc)
+{
+	ptlock_free(ptdesc);
+	__pagetable_pte_dtor(ptdesc);
+}
+
 pte_t *__pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp);
 static inline pte_t *pte_offset_map(pmd_t *pmd, unsigned long addr)
 {
-- 
2.30.2