Re: [RFC PATCH v2 2/3] mm: Add PUD level pagetable account

[Mike Rapoport <rppt@linux.ibm.com>]

On Wed, Jun 22, 2022 at 04:58:53PM +0800, Baolin Wang wrote:
> 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/loongarch/include/asm/pgalloc.h | 11 ++++++++---
>  arch/mips/include/asm/pgalloc.h      | 11 ++++++++---
>  arch/s390/include/asm/tlb.h          |  1 +
>  arch/x86/mm/pgtable.c                |  5 ++++-
>  include/asm-generic/pgalloc.h        | 12 ++++++++++--
>  6 files changed, 35 insertions(+), 10 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/loongarch/include/asm/pgalloc.h b/arch/loongarch/include/asm/pgalloc.h
> index b0a57b2..50a896f 100644
> --- a/arch/loongarch/include/asm/pgalloc.h
> +++ b/arch/loongarch/include/asm/pgalloc.h
> @@ -89,10 +89,15 @@ 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)
>  {
>  	pud_t *pud;
> +	struct page *pg;

	struct page *page;

looks better IMO.

> +
> +	pg = alloc_pages(GFP_KERNEL & ~__GFP_HIGHMEM, PUD_ORDER);
> +	if (!pg)
> +		return NULL;
>  
> -	pud = (pud_t *) __get_free_pages(GFP_KERNEL, PUD_ORDER);
> -	if (pud)
> -		pud_init((unsigned long)pud, (unsigned long)invalid_pmd_table);
> +	pgtable_set_and_inc(pg);
> +	pud = (pud_t *)page_address(pg);

I don't think __get_free_pages() should be replaced with alloc_pages()
here, just call pgtable_set_and_inc() with virt_to_page(pud). 

The same applies for the cases below.

> +	pud_init((unsigned long)pud, (unsigned long)invalid_pmd_table);
>  	return pud;
>  }
>  
> 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..a8ab3f9 100644
> --- a/arch/x86/mm/pgtable.c
> +++ b/arch/x86/mm/pgtable.c
> @@ -76,8 +76,11 @@ 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));
> +	paravirt_tlb_remove_table(tlb, page);
>  }
>  
>  #if CONFIG_PGTABLE_LEVELS > 4
> diff --git a/include/asm-generic/pgalloc.h b/include/asm-generic/pgalloc.h
> index 977bea1..328a714 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
> @@ -174,8 +179,11 @@ 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)
>  {
> +	struct page *page = virt_to_page(pud);
> +
>  	BUG_ON((unsigned long)pud & (PAGE_SIZE-1));
> -	free_page((unsigned long)pud);
> +	pgtable_clear_and_dec(page);
> +	__free_page(page);
>  }
>  
>  #ifndef __HAVE_ARCH_PUD_FREE
> -- 
> 1.8.3.1
> 

-- 
Sincerely yours,
Mike.