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SubjectRe: [PATCHv2 2/2] xtensa: use buddy allocator for PTE table
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On Mon, Oct 14, 2013 at 6:32 PM, Kirill A. Shutemov
<kirill.shutemov@linux.intel.com> wrote:
> At the moment xtensa uses slab allocator for PTE table. It doesn't work
> with enabled split page table lock: slab uses page->slab_cache and
> page->first_page for its pages. These fields share stroage with
> page->ptl.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Cc: Chris Zankel <chris@zankel.net>
> Cc: Max Filippov <jcmvbkbc@gmail.com>
> ---
> v2:
> - add missed return in pte_alloc_one_kernel;
>
> arch/xtensa/include/asm/pgalloc.h | 20 ++++++++++++--------
> arch/xtensa/include/asm/pgtable.h | 3 +--
> arch/xtensa/mm/mmu.c | 20 --------------------
> 3 files changed, 13 insertions(+), 30 deletions(-)
>
> diff --git a/arch/xtensa/include/asm/pgalloc.h b/arch/xtensa/include/asm/pgalloc.h
> index b8774f1e21..8507b32d6e 100644
> --- a/arch/xtensa/include/asm/pgalloc.h
> +++ b/arch/xtensa/include/asm/pgalloc.h
> @@ -38,14 +38,18 @@ static inline void pgd_free(struct mm_struct *mm, pgd_t *pgd)
> free_page((unsigned long)pgd);
> }
>
> -/* Use a slab cache for the pte pages (see also sparc64 implementation) */
> -
> -extern struct kmem_cache *pgtable_cache;
> -
> static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm,
> unsigned long address)
> {
> - return kmem_cache_alloc(pgtable_cache, GFP_KERNEL|__GFP_REPEAT);
> + pte_t *ptep;
> + int i;
> +
> + ptep = (pte_t *)__get_free_page(GFP_KERNEL|__GFP_REPEAT);
> + if (!ptep)
> + return NULL;
> + for (i = 0; i < 1024; i++, ptep++)
> + pte_clear(NULL, 0, ptep);
> + return ptep;

You're returning modified ptep, not the allocated one.

> }
>
> static inline pgtable_t pte_alloc_one(struct mm_struct *mm,
> @@ -59,7 +63,7 @@ static inline pgtable_t pte_alloc_one(struct mm_struct *mm,
> return NULL;
> page = virt_to_page(pte);
> if (!pgtable_page_ctor(page)) {
> - kmem_cache_free(pgtable_cache, pte);
> + __free_page(page);
> return NULL;
> }
> return page;
> @@ -67,13 +71,13 @@ static inline pgtable_t pte_alloc_one(struct mm_struct *mm,
>
> static inline void pte_free_kernel(struct mm_struct *mm, pte_t *pte)
> {
> - kmem_cache_free(pgtable_cache, pte);
> + free_page((unsigned long)pte);
> }
>
> static inline void pte_free(struct mm_struct *mm, pgtable_t pte)
> {
> pgtable_page_dtor(pte);
> - kmem_cache_free(pgtable_cache, page_address(pte));
> + __free_page(pte);
> }
> #define pmd_pgtable(pmd) pmd_page(pmd)
>
> diff --git a/arch/xtensa/include/asm/pgtable.h b/arch/xtensa/include/asm/pgtable.h
> index 0fdf5d043f..216446295a 100644
> --- a/arch/xtensa/include/asm/pgtable.h
> +++ b/arch/xtensa/include/asm/pgtable.h
> @@ -220,12 +220,11 @@ extern unsigned long empty_zero_page[1024];
> #ifdef CONFIG_MMU
> extern pgd_t swapper_pg_dir[PAGE_SIZE/sizeof(pgd_t)];
> extern void paging_init(void);
> -extern void pgtable_cache_init(void);
> #else
> # define swapper_pg_dir NULL
> static inline void paging_init(void) { }
> -static inline void pgtable_cache_init(void) { }
> #endif
> +static inline void pgtable_cache_init(void) { }
>
> /*
> * The pmd contains the kernel virtual address of the pte page.
> diff --git a/arch/xtensa/mm/mmu.c b/arch/xtensa/mm/mmu.c
> index a1077570e3..c43771c974 100644
> --- a/arch/xtensa/mm/mmu.c
> +++ b/arch/xtensa/mm/mmu.c
> @@ -50,23 +50,3 @@ void __init init_mmu(void)
> */
> set_ptevaddr_register(PGTABLE_START);
> }
> -
> -struct kmem_cache *pgtable_cache __read_mostly;
> -
> -static void pgd_ctor(void *addr)
> -{
> - pte_t *ptep = (pte_t *)addr;
> - int i;
> -
> - for (i = 0; i < 1024; i++, ptep++)
> - pte_clear(NULL, 0, ptep);
> -
> -}
> -
> -void __init pgtable_cache_init(void)
> -{
> - pgtable_cache = kmem_cache_create("pgd",
> - PAGE_SIZE, PAGE_SIZE,
> - SLAB_HWCACHE_ALIGN,
> - pgd_ctor);
> -}
> --
> 1.8.4.rc3
>



--
Thanks.
-- Max


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