From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx128.postini.com [74.125.245.128]) by kanga.kvack.org (Postfix) with SMTP id 1A6D56B009D for ; Fri, 30 Nov 2012 10:02:43 -0500 (EST) From: "Kirill A. Shutemov" Subject: [PATCH 2/2] thp: avoid race on multiple parallel page faults to the same page Date: Fri, 30 Nov 2012 17:03:41 +0200 Message-Id: <1354287821-5925-3-git-send-email-kirill.shutemov@linux.intel.com> In-Reply-To: <1354287821-5925-1-git-send-email-kirill.shutemov@linux.intel.com> References: <50B52E17.8020205@suse.cz> <1354287821-5925-1-git-send-email-kirill.shutemov@linux.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Jiri Slaby Cc: linux-mm@kvack.org, LKML , David Rientjes , Bob Liu , Andrew Morton , Andrea Arcangeli , "Kirill A. Shutemov" 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(&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); -- 1.7.11.7 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org