On Thu, 2017-02-09 at 08:30 +0530, Aneesh Kumar K.V wrote:
> Autonuma preserves the write permission across numa fault to avoid taking
> a writefault after a numa fault (Commit: b191f9b106ea " mm: numa: preserve PTE
> write permissions across a NUMA hinting fault"). Architecture can implement
> protnone in different ways and some may choose to implement that by clearing
> Read/
> Write/Exec bit of pte. Setting the write bit on such pte can result in wrong
> behaviour. Fix this up by allowing arch to override how to save the write bit
> on a protnone pte.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
FWIW this is pretty simple and helps with us in powerpc...
Acked-By: Michael Neuling <mikey@xxxxxxxxxxx>
> ---
> include/asm-generic/pgtable.h | 16 ++++++++++++++++
> mm/huge_memory.c | 4 ++--
> mm/memory.c | 2 +-
> mm/mprotect.c | 4 ++--
> 4 files changed, 21 insertions(+), 5 deletions(-)
>
> diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
> index 18af2bcefe6a..b6f3a8a4b738 100644
> --- a/include/asm-generic/pgtable.h
> +++ b/include/asm-generic/pgtable.h
> @@ -192,6 +192,22 @@ static inline void ptep_set_wrprotect(struct mm_struct
> *mm, unsigned long addres
> }
> #endif
>
> +#ifndef pte_savedwrite
> +#define pte_savedwrite pte_write
> +#endif
> +
> +#ifndef pte_mk_savedwrite
> +#define pte_mk_savedwrite pte_mkwrite
> +#endif
> +
> +#ifndef pmd_savedwrite
> +#define pmd_savedwrite pmd_write
> +#endif
> +
> +#ifndef pmd_mk_savedwrite
> +#define pmd_mk_savedwrite pmd_mkwrite
> +#endif
> +
> #ifndef __HAVE_ARCH_PMDP_SET_WRPROTECT
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> static inline void pmdp_set_wrprotect(struct mm_struct *mm,
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 9a6bd6c8d55a..2f0f855ec911 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1300,7 +1300,7 @@ int do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t
> pmd)
> goto out;
> clear_pmdnuma:
> BUG_ON(!PageLocked(page));
> - was_writable = pmd_write(pmd);
> + was_writable = pmd_savedwrite(pmd);
> pmd = pmd_modify(pmd, vma->vm_page_prot);
> pmd = pmd_mkyoung(pmd);
> if (was_writable)
> @@ -1555,7 +1555,7 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t
> *pmd,
> entry = pmdp_huge_get_and_clear_notify(mm, addr,
> pmd);
> entry = pmd_modify(entry, newprot);
> if (preserve_write)
> - entry = pmd_mkwrite(entry);
> + entry = pmd_mk_savedwrite(entry);
> ret = HPAGE_PMD_NR;
> set_pmd_at(mm, addr, pmd, entry);
> BUG_ON(vma_is_anonymous(vma) && !preserve_write &&
> diff --git a/mm/memory.c b/mm/memory.c
> index e78bf72f30dd..88c24f89d6d3 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3388,7 +3388,7 @@ static int do_numa_page(struct vm_fault *vmf)
> int target_nid;
> bool migrated = false;
> pte_t pte;
> - bool was_writable = pte_write(vmf->orig_pte);
> + bool was_writable = pte_savedwrite(vmf->orig_pte);
> int flags = 0;
>
> /*
> diff --git a/mm/mprotect.c b/mm/mprotect.c
> index f9c07f54dd62..15f5c174a7c1 100644
> --- a/mm/mprotect.c
> +++ b/mm/mprotect.c
> @@ -113,13 +113,13 @@ static unsigned long change_pte_range(struct
> vm_area_struct *vma, pmd_t *pmd,
> ptent = ptep_modify_prot_start(mm, addr, pte);
> ptent = pte_modify(ptent, newprot);
> if (preserve_write)
> - ptent = pte_mkwrite(ptent);
> + ptent = pte_mk_savedwrite(ptent);
>
> /* Avoid taking write faults for known dirty pages */
> if (dirty_accountable && pte_dirty(ptent) &&
> (pte_soft_dirty(ptent) ||
> !(vma->vm_flags & VM_SOFTDIRTY))) {
> - ptent = pte_mkwrite(ptent);
> + ptent = pte_mk_savedwrite(ptent);
> }
> ptep_modify_prot_commit(mm, addr, pte, ptent);
> pages++;
--
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