Re: [RFC PATCH v2 3/3] mm: Add kernel PTE level pagetable pages account

[Baolin Wang]

On 6/22/2022 10:44 PM, Mike Rapoport wrote:
> On Wed, Jun 22, 2022 at 04:58:54PM +0800, Baolin Wang wrote:
> > 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. Especially the vmalloc()/vmap() can consume lots of
> > kernel pagetable, so 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.
>
> This patch only adds accounting to the page tables allocated after boot,
> please mention this in the changelog.

OK. Will add in next version.

>   
> > Meanwhile converting architectures to use corresponding generic PTE pagetable
> > allocation and freeing functions.
> >
> > Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> > Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
> > ---
> >   arch/csky/include/asm/pgalloc.h |  2 +-
> >   arch/microblaze/mm/pgtable.c    |  2 +-
> >   arch/openrisc/mm/ioremap.c      |  2 +-
> >   arch/x86/mm/pgtable.c           |  5 ++++-
> >   include/asm-generic/pgalloc.h   | 14 ++++++++++++--
> >   5 files changed, 19 insertions(+), 6 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/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
> > index a8ab3f9..fc2b9ef 100644
> > --- a/arch/x86/mm/pgtable.c
> > +++ b/arch/x86/mm/pgtable.c
> > @@ -851,6 +851,7 @@ int pud_free_pmd_page(pud_t *pud, unsigned long addr)
> >   int pmd_free_pte_page(pmd_t *pmd, unsigned long addr)
> >   {
> >   	pte_t *pte;
> > +	struct page *page;
> >   
> >   	pte = (pte_t *)pmd_page_vaddr(*pmd);
> >   	pmd_clear(pmd);
> > @@ -858,7 +859,9 @@ int pmd_free_pte_page(pmd_t *pmd, unsigned long addr)
> >   	/* INVLPG to clear all paging-structure caches */
> >   	flush_tlb_kernel_range(addr, addr + PAGE_SIZE-1);
> >   
> > -	free_page((unsigned long)pte);
> > +	page = virt_to_page(pte);
> > +	pgtable_clear_and_dec(page);
> > +	__free_page(page);
> >   
> >   	return 1;
> >   }
> > diff --git a/include/asm-generic/pgalloc.h b/include/asm-generic/pgalloc.h
> > index 328a714..2e20e9e 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);
>
> {
> 	pte_t *pte = (pte_t *)__get_free_page(GFP_PGTABLE_KERNEL);
>
> 	if (pte)
> 		pgtable_set_and_inc(virt_to_page(pte));
>
> 	return pte;
> }
>
> looks simpler, doesn't it?

Yes, will do in next version. Thanks for reviewing.