Re: [PATCH 2/2] thp: avoid race on multiple parallel page faults to the same page
On Fri, Nov 30, 2012 at 11:03 PM, Kirill A. Shutemov wrote: > From: "Kirill A. Shutemov" > > pmd value is stable only with mm->page_table_lock taken. After taking > the lock we need to check that nobody modified the pmd before change it. > > Signed-off-by: Kirill A. Shutemov Reviewed-by: Bob Liu > --- > mm/huge_memory.c | 29 - > 1 file changed, 24 insertions(+), 5 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 9d6f521..51cb8fe 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -770,17 +770,20 @@ static inline struct page *alloc_hugepage(int defrag) > } > #endif > > -static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, > +static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, > struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd, > unsigned long zero_pfn) > { > pmd_t entry; > + if (!pmd_none(*pmd)) > + return false; > entry = pfn_pmd(zero_pfn, vma->vm_page_prot); > entry = pmd_wrprotect(entry); > entry = pmd_mkhuge(entry); > set_pmd_at(mm, haddr, pmd, entry); > pgtable_trans_huge_deposit(mm, pgtable); > mm->nr_ptes++; > + return true; > } > > int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct > *vma, > @@ -800,6 +803,7 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, > struct vm_area_struct *vma, > transparent_hugepage_use_zero_page()) { > pgtable_t pgtable; > unsigned long zero_pfn; > + bool set; > pgtable = pte_alloc_one(mm, haddr); > if (unlikely(!pgtable)) > return VM_FAULT_OOM; > @@ -810,9 +814,13 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, > struct vm_area_struct *vma, > goto out; > } > spin_lock(>page_table_lock); > - set_huge_zero_page(pgtable, mm, vma, haddr, pmd, > + set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd, > zero_pfn); > spin_unlock(>page_table_lock); > + if (!set) { > + pte_free(mm, pgtable); > + put_huge_zero_page(); > + } > return 0; > } > page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), > @@ -1046,14 +1054,16 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct > mm_struct *src_mm, > */ > if (is_huge_zero_pmd(pmd)) { > unsigned long zero_pfn; > + bool set; > /* > * get_huge_zero_page() will never allocate a new page here, > * since we already have a zero page to copy. It just takes a > * reference. > */ > zero_pfn = get_huge_zero_page(); > - set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, > + set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, > zero_pfn); > + BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */ > ret = 0; > goto out_unlock; > } > @@ -1110,7 +1120,7 @@ unlock: > > static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm, > struct vm_area_struct *vma, unsigned long address, > - pmd_t *pmd, unsigned long haddr) > + pmd_t *pmd, pmd_t orig_pmd, unsigned long haddr) > { > pgtable_t pgtable; > pmd_t _pmd; > @@ -1139,6 +1149,9 @@ static int do_huge_pmd_wp_zero_page_fallback(struct > mm_struct *mm, > mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); > > spin_lock(>page_table_lock); > + if (unlikely(!pmd_same(*pmd, orig_pmd))) > + goto out_free_page; > + > pmdp_clear_flush(vma, haddr, pmd); > /* leave pmd empty until pte is filled */ > > @@ -1171,6 +1184,12 @@ static int do_huge_pmd_wp_zero_page_fallback(struct > mm_struct *mm, > ret |= VM_FAULT_WRITE; > out: > return ret; > +out_free_page: > + spin_unlock(>page_table_lock); > + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); > + mem_cgroup_uncharge_page(page); > + put_page(page); > + goto out; > } > > static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, > @@ -1317,7 +1336,7 @@ alloc: > count_vm_event(THP_FAULT_FALLBACK); > if (is_huge_zero_pmd(orig_pmd)) { > ret = do_huge_pmd_wp_zero_page_fallback(mm, vma, > - address, pmd, haddr); > +
Re: [PATCH 2/2] thp: avoid race on multiple parallel page faults to the same page
On Fri, Nov 30, 2012 at 11:03 PM, Kirill A. Shutemov kirill.shute...@linux.intel.com wrote: From: Kirill A. Shutemov kirill.shute...@linux.intel.com pmd value is stable only with mm-page_table_lock taken. After taking the lock we need to check that nobody modified the pmd before change it. Signed-off-by: Kirill A. Shutemov kirill.shute...@linux.intel.com Reviewed-by: Bob Liu lliu...@gmail.com --- mm/huge_memory.c | 29 - 1 file changed, 24 insertions(+), 5 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 9d6f521..51cb8fe 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -770,17 +770,20 @@ static inline struct page *alloc_hugepage(int defrag) } #endif -static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, +static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd, unsigned long zero_pfn) { pmd_t entry; + if (!pmd_none(*pmd)) + return false; entry = pfn_pmd(zero_pfn, vma-vm_page_prot); entry = pmd_wrprotect(entry); entry = pmd_mkhuge(entry); set_pmd_at(mm, haddr, pmd, entry); pgtable_trans_huge_deposit(mm, pgtable); mm-nr_ptes++; + return true; } int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, @@ -800,6 +803,7 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, transparent_hugepage_use_zero_page()) { pgtable_t pgtable; unsigned long zero_pfn; + bool set; pgtable = pte_alloc_one(mm, haddr); if (unlikely(!pgtable)) return VM_FAULT_OOM; @@ -810,9 +814,13 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, goto out; } spin_lock(mm-page_table_lock); - set_huge_zero_page(pgtable, mm, vma, haddr, pmd, + set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd, zero_pfn); spin_unlock(mm-page_table_lock); + if (!set) { + pte_free(mm, pgtable); + put_huge_zero_page(); + } return 0; } page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), @@ -1046,14 +1054,16 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, */ if (is_huge_zero_pmd(pmd)) { unsigned long zero_pfn; + bool set; /* * get_huge_zero_page() will never allocate a new page here, * since we already have a zero page to copy. It just takes a * reference. */ zero_pfn = get_huge_zero_page(); - set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, + set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, zero_pfn); + BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */ ret = 0; goto out_unlock; } @@ -1110,7 +1120,7 @@ unlock: static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, - pmd_t *pmd, unsigned long haddr) + pmd_t *pmd, pmd_t orig_pmd, unsigned long haddr) { pgtable_t pgtable; pmd_t _pmd; @@ -1139,6 +1149,9 @@ static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm, mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); spin_lock(mm-page_table_lock); + if (unlikely(!pmd_same(*pmd, orig_pmd))) + goto out_free_page; + pmdp_clear_flush(vma, haddr, pmd); /* leave pmd empty until pte is filled */ @@ -1171,6 +1184,12 @@ static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm, ret |= VM_FAULT_WRITE; out: return ret; +out_free_page: + spin_unlock(mm-page_table_lock); + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); + mem_cgroup_uncharge_page(page); + put_page(page); + goto out; } static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, @@ -1317,7 +1336,7 @@ alloc: count_vm_event(THP_FAULT_FALLBACK); if (is_huge_zero_pmd(orig_pmd)) { ret = do_huge_pmd_wp_zero_page_fallback(mm, vma, - address, pmd, haddr); +
[PATCH 2/2] thp: avoid race on multiple parallel page faults to the same page
From: "Kirill A. Shutemov" pmd value is stable only with mm->page_table_lock taken. After taking the lock we need to check that nobody modified the pmd before change it. Signed-off-by: Kirill A. Shutemov --- mm/huge_memory.c | 29 - 1 file changed, 24 insertions(+), 5 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 9d6f521..51cb8fe 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -770,17 +770,20 @@ static inline struct page *alloc_hugepage(int defrag) } #endif -static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, +static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd, unsigned long zero_pfn) { pmd_t entry; + if (!pmd_none(*pmd)) + return false; entry = pfn_pmd(zero_pfn, vma->vm_page_prot); entry = pmd_wrprotect(entry); entry = pmd_mkhuge(entry); set_pmd_at(mm, haddr, pmd, entry); pgtable_trans_huge_deposit(mm, pgtable); mm->nr_ptes++; + return true; } int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, @@ -800,6 +803,7 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, transparent_hugepage_use_zero_page()) { pgtable_t pgtable; unsigned long zero_pfn; + bool set; pgtable = pte_alloc_one(mm, haddr); if (unlikely(!pgtable)) return VM_FAULT_OOM; @@ -810,9 +814,13 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, goto out; } spin_lock(>page_table_lock); - set_huge_zero_page(pgtable, mm, vma, haddr, pmd, + set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd, zero_pfn); spin_unlock(>page_table_lock); + if (!set) { + pte_free(mm, pgtable); + put_huge_zero_page(); + } return 0; } page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), @@ -1046,14 +1054,16 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, */ if (is_huge_zero_pmd(pmd)) { unsigned long zero_pfn; + bool set; /* * get_huge_zero_page() will never allocate a new page here, * since we already have a zero page to copy. It just takes a * reference. */ zero_pfn = get_huge_zero_page(); - set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, + set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, zero_pfn); + BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */ ret = 0; goto out_unlock; } @@ -1110,7 +1120,7 @@ unlock: static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, - pmd_t *pmd, unsigned long haddr) + pmd_t *pmd, pmd_t orig_pmd, unsigned long haddr) { pgtable_t pgtable; pmd_t _pmd; @@ -1139,6 +1149,9 @@ static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm, mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); spin_lock(>page_table_lock); + if (unlikely(!pmd_same(*pmd, orig_pmd))) + goto out_free_page; + pmdp_clear_flush(vma, haddr, pmd); /* leave pmd empty until pte is filled */ @@ -1171,6 +1184,12 @@ static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm, ret |= VM_FAULT_WRITE; out: return ret; +out_free_page: + spin_unlock(>page_table_lock); + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); + mem_cgroup_uncharge_page(page); + put_page(page); + goto out; } static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, @@ -1317,7 +1336,7 @@ alloc: count_vm_event(THP_FAULT_FALLBACK); if (is_huge_zero_pmd(orig_pmd)) { ret = do_huge_pmd_wp_zero_page_fallback(mm, vma, - address, pmd, haddr); + address, pmd, orig_pmd, haddr); } else { ret = do_huge_pmd_wp_page_fallback(mm, vma, address, pmd, orig_pmd, page, haddr); -- 1.7.11.7 -- To unsubscribe from this list: send the line "unsubscribe
[PATCH 2/2] thp: avoid race on multiple parallel page faults to the same page
From: Kirill A. Shutemov kirill.shute...@linux.intel.com pmd value is stable only with mm-page_table_lock taken. After taking the lock we need to check that nobody modified the pmd before change it. Signed-off-by: Kirill A. Shutemov kirill.shute...@linux.intel.com --- mm/huge_memory.c | 29 - 1 file changed, 24 insertions(+), 5 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 9d6f521..51cb8fe 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -770,17 +770,20 @@ static inline struct page *alloc_hugepage(int defrag) } #endif -static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, +static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd, unsigned long zero_pfn) { pmd_t entry; + if (!pmd_none(*pmd)) + return false; entry = pfn_pmd(zero_pfn, vma-vm_page_prot); entry = pmd_wrprotect(entry); entry = pmd_mkhuge(entry); set_pmd_at(mm, haddr, pmd, entry); pgtable_trans_huge_deposit(mm, pgtable); mm-nr_ptes++; + return true; } int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, @@ -800,6 +803,7 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, transparent_hugepage_use_zero_page()) { pgtable_t pgtable; unsigned long zero_pfn; + bool set; pgtable = pte_alloc_one(mm, haddr); if (unlikely(!pgtable)) return VM_FAULT_OOM; @@ -810,9 +814,13 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, goto out; } spin_lock(mm-page_table_lock); - set_huge_zero_page(pgtable, mm, vma, haddr, pmd, + set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd, zero_pfn); spin_unlock(mm-page_table_lock); + if (!set) { + pte_free(mm, pgtable); + put_huge_zero_page(); + } return 0; } page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), @@ -1046,14 +1054,16 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, */ if (is_huge_zero_pmd(pmd)) { unsigned long zero_pfn; + bool set; /* * get_huge_zero_page() will never allocate a new page here, * since we already have a zero page to copy. It just takes a * reference. */ zero_pfn = get_huge_zero_page(); - set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, + set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, zero_pfn); + BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */ ret = 0; goto out_unlock; } @@ -1110,7 +1120,7 @@ unlock: static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, - pmd_t *pmd, unsigned long haddr) + pmd_t *pmd, pmd_t orig_pmd, unsigned long haddr) { pgtable_t pgtable; pmd_t _pmd; @@ -1139,6 +1149,9 @@ static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm, mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); spin_lock(mm-page_table_lock); + if (unlikely(!pmd_same(*pmd, orig_pmd))) + goto out_free_page; + pmdp_clear_flush(vma, haddr, pmd); /* leave pmd empty until pte is filled */ @@ -1171,6 +1184,12 @@ static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm, ret |= VM_FAULT_WRITE; out: return ret; +out_free_page: + spin_unlock(mm-page_table_lock); + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); + mem_cgroup_uncharge_page(page); + put_page(page); + goto out; } static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, @@ -1317,7 +1336,7 @@ alloc: count_vm_event(THP_FAULT_FALLBACK); if (is_huge_zero_pmd(orig_pmd)) { ret = do_huge_pmd_wp_zero_page_fallback(mm, vma, - address, pmd, haddr); + address, pmd, orig_pmd, haddr); } else { ret = do_huge_pmd_wp_page_fallback(mm, vma, address, pmd, orig_pmd, page, haddr); --