[RFC PATCH 2/3] mm: Add PUD level pagetable account

[Baolin Wang <baolin.wang@linux.alibaba.com>]

Now the PUD level ptes are always protected by mm->page_table_lock,
which means no split pagetable lock needed. So the generic PUD level
pagetable pages allocation will not call pgtable_pte_page_ctor/dtor(),
that means we will miss to account PUD level pagetable pages.

Adding pagetable account by calling pgtable_set_and_inc() or
pgtable_clear_and_dec() when allocating or freeing PUD level pagetable
pages to help to get an accurate pagetable accounting.

Moreover this patch will also mark the PUD level pagetable with PG_table
flag, which will help to do sanity validation in unpoison_memory() and
get more accurate pagetable accounting by /proc/kpageflags interface.

Meanwhile converting the architectures with using generic PUD pagatable
allocation to add corresponding pgtable_set_and_inc() or pgtable_clear_and_dec()
to account PUD level pagetable.

Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
---
 arch/arm64/include/asm/tlb.h    |  5 ++++-
 arch/mips/include/asm/pgalloc.h | 11 ++++++++---
 arch/s390/include/asm/tlb.h     |  1 +
 arch/x86/mm/pgtable.c           |  3 +++
 include/asm-generic/pgalloc.h   |  8 +++++++-
 5 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/asm/tlb.h b/arch/arm64/include/asm/tlb.h
index c995d1f..47e0623 100644
--- a/arch/arm64/include/asm/tlb.h
+++ b/arch/arm64/include/asm/tlb.h
@@ -94,7 +94,10 @@ static inline void __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmdp,
 static inline void __pud_free_tlb(struct mmu_gather *tlb, pud_t *pudp,
 				  unsigned long addr)
 {
-	tlb_remove_table(tlb, virt_to_page(pudp));
+	struct page *page = virt_to_page(pudp);
+
+	pgtable_clear_and_dec(page);
+	tlb_remove_table(tlb, page);
 }
 #endif
 
diff --git a/arch/mips/include/asm/pgalloc.h b/arch/mips/include/asm/pgalloc.h
index 867e9c3..0950f5f 100644
--- a/arch/mips/include/asm/pgalloc.h
+++ b/arch/mips/include/asm/pgalloc.h
@@ -89,11 +89,16 @@ static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long address)
 
 static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long address)
 {
+	struct page *pg;
 	pud_t *pud;
 
-	pud = (pud_t *) __get_free_pages(GFP_KERNEL, PUD_ORDER);
-	if (pud)
-		pud_init((unsigned long)pud, (unsigned long)invalid_pmd_table);
+	pg = alloc_pages(GFP_KERNEL & ~__GFP_HIGHMEM, PUD_ORDER);
+	if (!pg)
+		return NULL;
+
+	pgtable_set_and_inc(pg);
+	pud = (pud_t *)page_address(pg);
+	pud_init((unsigned long)pud, (unsigned long)invalid_pmd_table);
 	return pud;
 }
 
diff --git a/arch/s390/include/asm/tlb.h b/arch/s390/include/asm/tlb.h
index fe6407f..45f9541 100644
--- a/arch/s390/include/asm/tlb.h
+++ b/arch/s390/include/asm/tlb.h
@@ -125,6 +125,7 @@ static inline void pud_free_tlb(struct mmu_gather *tlb, pud_t *pud,
 {
 	if (mm_pud_folded(tlb->mm))
 		return;
+	pgtable_clear_and_dec(virt_to_page(pud));
 	tlb->mm->context.flush_mm = 1;
 	tlb->freed_tables = 1;
 	tlb->cleared_p4ds = 1;
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index a932d77..6cccf52 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -76,6 +76,9 @@ void ___pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd)
 #if CONFIG_PGTABLE_LEVELS > 3
 void ___pud_free_tlb(struct mmu_gather *tlb, pud_t *pud)
 {
+	struct page *page = virt_to_page(pud);
+
+	pgtable_clear_and_dec(page);
 	paravirt_release_pud(__pa(pud) >> PAGE_SHIFT);
 	paravirt_tlb_remove_table(tlb, virt_to_page(pud));
 }
diff --git a/include/asm-generic/pgalloc.h b/include/asm-generic/pgalloc.h
index 977bea1..78ab9f6 100644
--- a/include/asm-generic/pgalloc.h
+++ b/include/asm-generic/pgalloc.h
@@ -149,11 +149,16 @@ static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd)
 
 static inline pud_t *__pud_alloc_one(struct mm_struct *mm, unsigned long addr)
 {
+	struct page *page;
 	gfp_t gfp = GFP_PGTABLE_USER;
 
 	if (mm == &init_mm)
 		gfp = GFP_PGTABLE_KERNEL;
-	return (pud_t *)get_zeroed_page(gfp);
+	page = alloc_pages((gfp | __GFP_ZERO) & ~__GFP_HIGHMEM, 0);
+	if (!page)
+		return NULL;
+	pgtable_set_and_inc(page);
+	return (pud_t *)page_address(page);
 }
 
 #ifndef __HAVE_ARCH_PUD_ALLOC_ONE
@@ -175,6 +180,7 @@ static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long addr)
 static inline void __pud_free(struct mm_struct *mm, pud_t *pud)
 {
 	BUG_ON((unsigned long)pud & (PAGE_SIZE-1));
+	pgtable_clear_and_dec(virt_to_page(pud));
 	free_page((unsigned long)pud);
 }
 
-- 
1.8.3.1