From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id D40536B0260 for ; Wed, 13 Dec 2017 05:58:15 -0500 (EST) Received: by mail-pf0-f200.google.com with SMTP id u16so1591917pfh.7 for ; Wed, 13 Dec 2017 02:58:15 -0800 (PST) Received: from mga04.intel.com (mga04.intel.com. [192.55.52.120]) by mx.google.com with ESMTPS id s17si1156494plp.176.2017.12.13.02.58.14 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 13 Dec 2017 02:58:14 -0800 (PST) From: "Kirill A. Shutemov" Subject: [PATCHv4 10/12] mm: Do not lose dirty and access bits in pmdp_invalidate() Date: Wed, 13 Dec 2017 13:57:54 +0300 Message-Id: <20171213105756.69879-11-kirill.shutemov@linux.intel.com> In-Reply-To: <20171213105756.69879-1-kirill.shutemov@linux.intel.com> References: <20171213105756.69879-1-kirill.shutemov@linux.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Vlastimil Babka , Andrea Arcangeli , Michal Hocko , linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" , Hugh Dickins 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 Reported-by: Vlastimil Babka Cc: Hugh Dickins --- 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: email@kvack.org