linux-kernel - [RFC PATCH 3/3] mm: Add kernel PTE level pagetable pages account

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Message-Id: <d35f42f7b598f629437940f941826e2cc49a97f6.1654271618.git.baolin.wang@linux.alibaba.com>
Date:   Sat,  4 Jun 2022 09:32:31 +0800
From:   Baolin Wang <baolin.wang@...ux.alibaba.com>
To:     akpm@...ux-foundation.org
Cc:     baolin.wang@...ux.alibaba.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [RFC PATCH 3/3] mm: Add kernel PTE level pagetable pages account

Now the kernel PTE level ptes are always protected by mm->page_table_lock
instead of split pagetable lock, so the kernel PTE level pagetable pages
are not accounted. To get an accurate pagetable accounting, calling new
helpers pgtable_set_and_inc()/pgtable_clear_and_dec() when allocating or
freeing a kernel PTE level pagetable page.

Meanwhile converting architectures to use corresponding generic PTE pagetable
allocation and freeing functions.

Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
---
 arch/csky/include/asm/pgalloc.h |  2 +-
 arch/microblaze/mm/pgtable.c    |  2 +-
 arch/openrisc/mm/ioremap.c      |  2 +-
 include/asm-generic/pgalloc.h   | 10 +++++++++-
 4 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/csky/include/asm/pgalloc.h b/arch/csky/include/asm/pgalloc.h
index bbbd069..2443226 100644
--- a/arch/csky/include/asm/pgalloc.h
+++ b/arch/csky/include/asm/pgalloc.h
@@ -29,7 +29,7 @@ static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm)
 	pte_t *pte;
 	unsigned long i;
 
-	pte = (pte_t *) __get_free_page(GFP_KERNEL);
+	pte = __pte_alloc_one_kernel(mm);
 	if (!pte)
 		return NULL;
 
diff --git a/arch/microblaze/mm/pgtable.c b/arch/microblaze/mm/pgtable.c
index 9f73265..e96dd1b 100644
--- a/arch/microblaze/mm/pgtable.c
+++ b/arch/microblaze/mm/pgtable.c
@@ -245,7 +245,7 @@ unsigned long iopa(unsigned long addr)
 __ref pte_t *pte_alloc_one_kernel(struct mm_struct *mm)
 {
 	if (mem_init_done)
-		return (pte_t *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
+		return __pte_alloc_one_kernel(mm);
 	else
 		return memblock_alloc_try_nid(PAGE_SIZE, PAGE_SIZE,
 					      MEMBLOCK_LOW_LIMIT,
diff --git a/arch/openrisc/mm/ioremap.c b/arch/openrisc/mm/ioremap.c
index daae13a..3453acc 100644
--- a/arch/openrisc/mm/ioremap.c
+++ b/arch/openrisc/mm/ioremap.c
@@ -118,7 +118,7 @@ pte_t __ref *pte_alloc_one_kernel(struct mm_struct *mm)
 	pte_t *pte;
 
 	if (likely(mem_init_done)) {
-		pte = (pte_t *)get_zeroed_page(GFP_KERNEL);
+		pte = __pte_alloc_one_kernel(mm);
 	} else {
 		pte = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
 		if (!pte)
diff --git a/include/asm-generic/pgalloc.h b/include/asm-generic/pgalloc.h
index 78ab9f6..f5345b2 100644
--- a/include/asm-generic/pgalloc.h
+++ b/include/asm-generic/pgalloc.h
@@ -18,7 +18,14 @@
  */
 static inline pte_t *__pte_alloc_one_kernel(struct mm_struct *mm)
 {
-	return (pte_t *)__get_free_page(GFP_PGTABLE_KERNEL);
+	struct page *page;
+	gfp_t gfp = GFP_PGTABLE_KERNEL;
+
+	page = alloc_pages(gfp & ~__GFP_HIGHMEM, 0);
+	if (!page)
+		return NULL;
+	pgtable_set_and_inc(page);
+	return (pte_t *)page_address(page);
 }
 
 #ifndef __HAVE_ARCH_PTE_ALLOC_ONE_KERNEL
@@ -41,6 +48,7 @@ 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)
 {
+	pgtable_clear_and_dec(virt_to_page(pte));
 	free_page((unsigned long)pte);
 }
 
-- 
1.8.3.1