Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751865AbdILPku (ORCPT ); Tue, 12 Sep 2017 11:40:50 -0400 Received: from mga09.intel.com ([134.134.136.24]:4415 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751824AbdILPk2 (ORCPT ); Tue, 12 Sep 2017 11:40:28 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.42,383,1500966000"; d="scan'208";a="1171502673" From: "Kirill A. Shutemov" To: Andrew Morton , Vlastimil Babka , Vineet Gupta , Russell King , Will Deacon , Catalin Marinas , Ralf Baechle , "David S. Miller" , "Aneesh Kumar K . V" , Martin Schwidefsky , Heiko Carstens , Andrea Arcangeli Cc: linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" , Hugh Dickins Subject: [PATCHv3 10/11] mm: Do not loose dirty and access bits in pmdp_invalidate() Date: Tue, 12 Sep 2017 18:39:40 +0300 Message-Id: <20170912153941.47012-11-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20170912153941.47012-1-kirill.shutemov@linux.intel.com> References: <20170912153941.47012-1-kirill.shutemov@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2045 Lines: 55 Vlastimil noted that pmdp_invalidate() is not atomic and we can loose 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 bf0889eb774d..9df1da175fb0 100644 --- a/include/asm-generic/pgtable.h +++ b/include/asm-generic/pgtable.h @@ -324,7 +324,7 @@ 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 1175f6a24fdb..3db8f2f76666 100644 --- a/mm/pgtable-generic.c +++ b/mm/pgtable-generic.c @@ -180,12 +180,12 @@ 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 -- 2.14.1