From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> To: Andrew Morton <akpm@linux-foundation.org> Cc: Vlastimil Babka <vbabka@suse.cz>, Andrea Arcangeli <aarcange@redhat.com>, Michal Hocko <mhocko@kernel.org>, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Hugh Dickins <hughd@google.com> Subject: [PATCHv4 10/12] mm: Do not lose dirty and access bits in pmdp_invalidate() Date: Wed, 13 Dec 2017 13:57:54 +0300 [thread overview] Message-ID: <20171213105756.69879-11-kirill.shutemov@linux.intel.com> (raw) In-Reply-To: <20171213105756.69879-1-kirill.shutemov@linux.intel.com> Vlastimil noted that pmdp_invalidate() is not atomic and we can lose dirty and access bits if CPU sets them after pmdp dereference, but before set_pmd_at(). The patch change pmdp_invalidate() to make the entry non-present atomically and return previous value of the entry. This value can be used to check if CPU set dirty/accessed bits under us. The race window is very small and I haven't seen any reports that can be attributed to the bug. For this reason, I don't think backporting to stable trees needed. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reported-by: Vlastimil Babka <vbabka@suse.cz> Cc: Hugh Dickins <hughd@google.com> --- include/asm-generic/pgtable.h | 2 +- mm/pgtable-generic.c | 6 +++--- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h index ae83b14200b8..f449c71cbdc0 100644 --- a/include/asm-generic/pgtable.h +++ b/include/asm-generic/pgtable.h @@ -325,7 +325,7 @@ static inline pmd_t generic_pmdp_establish(struct vm_area_struct *vma, #endif #ifndef __HAVE_ARCH_PMDP_INVALIDATE -extern void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address, +extern pmd_t pmdp_invalidate(struct vm_area_struct *vma, unsigned long address, pmd_t *pmdp); #endif diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c index 1e4ee763c190..cf2af04b34b9 100644 --- a/mm/pgtable-generic.c +++ b/mm/pgtable-generic.c @@ -181,12 +181,12 @@ pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp) #endif #ifndef __HAVE_ARCH_PMDP_INVALIDATE -void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address, +pmd_t pmdp_invalidate(struct vm_area_struct *vma, unsigned long address, pmd_t *pmdp) { - pmd_t entry = *pmdp; - set_pmd_at(vma->vm_mm, address, pmdp, pmd_mknotpresent(entry)); + pmd_t old = pmdp_establish(vma, address, pmdp, pmd_mknotpresent(*pmdp)); flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE); + return old; } #endif -- 2.15.0
WARNING: multiple messages have this Message-ID (diff)
From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> To: Andrew Morton <akpm@linux-foundation.org> Cc: Vlastimil Babka <vbabka@suse.cz>, Andrea Arcangeli <aarcange@redhat.com>, Michal Hocko <mhocko@kernel.org>, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Hugh Dickins <hughd@google.com> Subject: [PATCHv4 10/12] mm: Do not lose dirty and access bits in pmdp_invalidate() Date: Wed, 13 Dec 2017 13:57:54 +0300 [thread overview] Message-ID: <20171213105756.69879-11-kirill.shutemov@linux.intel.com> (raw) In-Reply-To: <20171213105756.69879-1-kirill.shutemov@linux.intel.com> Vlastimil noted that pmdp_invalidate() is not atomic and we can lose dirty and access bits if CPU sets them after pmdp dereference, but before set_pmd_at(). The patch change pmdp_invalidate() to make the entry non-present atomically and return previous value of the entry. This value can be used to check if CPU set dirty/accessed bits under us. The race window is very small and I haven't seen any reports that can be attributed to the bug. For this reason, I don't think backporting to stable trees needed. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reported-by: Vlastimil Babka <vbabka@suse.cz> Cc: Hugh Dickins <hughd@google.com> --- include/asm-generic/pgtable.h | 2 +- mm/pgtable-generic.c | 6 +++--- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h index ae83b14200b8..f449c71cbdc0 100644 --- a/include/asm-generic/pgtable.h +++ b/include/asm-generic/pgtable.h @@ -325,7 +325,7 @@ static inline pmd_t generic_pmdp_establish(struct vm_area_struct *vma, #endif #ifndef __HAVE_ARCH_PMDP_INVALIDATE -extern void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address, +extern pmd_t pmdp_invalidate(struct vm_area_struct *vma, unsigned long address, pmd_t *pmdp); #endif diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c index 1e4ee763c190..cf2af04b34b9 100644 --- a/mm/pgtable-generic.c +++ b/mm/pgtable-generic.c @@ -181,12 +181,12 @@ pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp) #endif #ifndef __HAVE_ARCH_PMDP_INVALIDATE -void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address, +pmd_t pmdp_invalidate(struct vm_area_struct *vma, unsigned long address, pmd_t *pmdp) { - pmd_t entry = *pmdp; - set_pmd_at(vma->vm_mm, address, pmdp, pmd_mknotpresent(entry)); + pmd_t old = pmdp_establish(vma, address, pmdp, pmd_mknotpresent(*pmdp)); flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE); + return old; } #endif -- 2.15.0 -- 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: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-12-13 10:58 UTC|newest] Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-12-13 10:57 [PATCHv4 00/12] Do not lose dirty bit on THP pages Kirill A. Shutemov 2017-12-13 10:57 ` Kirill A. Shutemov 2017-12-13 10:57 ` [PATCHv4 01/12] asm-generic: Provide generic_pmdp_establish() Kirill A. Shutemov 2017-12-13 10:57 ` Kirill A. Shutemov 2017-12-13 10:57 ` [PATCHv4 02/12] arc: Use generic_pmdp_establish as pmdp_establish Kirill A. Shutemov 2017-12-13 10:57 ` Kirill A. Shutemov 2017-12-13 10:57 ` [PATCHv4 03/12] arm/mm: Provide pmdp_establish() helper Kirill A. Shutemov 2017-12-13 10:57 ` Kirill A. Shutemov 2017-12-13 10:57 ` [PATCHv4 04/12] arm64: " Kirill A. Shutemov 2017-12-13 10:57 ` Kirill A. Shutemov 2017-12-13 10:57 ` [PATCHv4 05/12] mips: Use generic_pmdp_establish as pmdp_establish Kirill A. Shutemov 2017-12-13 10:57 ` Kirill A. Shutemov 2017-12-13 10:57 ` [PATCHv4 06/12] powerpc/mm: update pmdp_invalidate to return old pmd value Kirill A. Shutemov 2017-12-13 10:57 ` Kirill A. Shutemov 2017-12-13 10:57 ` [PATCHv4 07/12] s390/mm: Modify pmdp_invalidate to return old value Kirill A. Shutemov 2017-12-13 10:57 ` Kirill A. Shutemov 2017-12-13 10:57 ` [PATCHv4 08/12] sparc64: Update pmdp_invalidate() to return old pmd value Kirill A. Shutemov 2017-12-13 10:57 ` Kirill A. Shutemov 2017-12-14 0:06 ` Andrew Morton 2017-12-14 0:06 ` Andrew Morton 2017-12-14 0:06 ` Andrew Morton 2017-12-13 10:57 ` [PATCHv4 09/12] x86/mm: Provide pmdp_establish() helper Kirill A. Shutemov 2017-12-13 10:57 ` Kirill A. Shutemov 2017-12-14 0:09 ` Andrew Morton 2017-12-14 0:09 ` Andrew Morton 2017-12-14 0:33 ` Kirill A. Shutemov 2017-12-14 0:33 ` Kirill A. Shutemov 2017-12-14 0:36 ` Andrew Morton 2017-12-14 0:36 ` Andrew Morton 2017-12-14 0:42 ` Kirill A. Shutemov 2017-12-14 0:42 ` Kirill A. Shutemov 2017-12-15 13:49 ` Kirill A. Shutemov 2017-12-15 13:49 ` Kirill A. Shutemov 2017-12-13 10:57 ` Kirill A. Shutemov [this message] 2017-12-13 10:57 ` [PATCHv4 10/12] mm: Do not lose dirty and access bits in pmdp_invalidate() Kirill A. Shutemov 2017-12-13 10:57 ` [PATCHv4 11/12] mm: Use updated pmdp_invalidate() interface to track dirty/accessed bits Kirill A. Shutemov 2017-12-13 10:57 ` Kirill A. Shutemov 2017-12-13 10:57 ` [PATCHv4 12/12] mm/thp: Remove pmd_huge_split_prepare Kirill A. Shutemov 2017-12-13 10:57 ` Kirill A. Shutemov
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