From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id AEA6E1A08CD for ; Sat, 17 Oct 2015 02:00:28 +1100 (AEDT) Message-ID: <1445007605.24309.25.camel@kernel.crashing.org> Subject: Re: [PATCH 1/3] mm: clearing pte in clear_soft_dirty() From: Benjamin Herrenschmidt To: Laurent Dufour , linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, xemul@parallels.com, linuxppc-dev@lists.ozlabs.org, mpe@ellerman.id.au, aneesh.kumar@linux.vnet.ibm.com, paulus@samba.org Cc: criu@openvz.org Date: Fri, 16 Oct 2015 20:30:05 +0530 In-Reply-To: <8352032008c7d9f1eee8d39599888a4cbe570bf7.1444995096.git.ldufour@linux.vnet.ibm.com> References: <8352032008c7d9f1eee8d39599888a4cbe570bf7.1444995096.git.ldufour@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, 2015-10-16 at 14:07 +0200, Laurent Dufour wrote: > As mentioned in the commit 56eecdb912b5 ("mm: Use > ptep/pmdp_set_numa() > for updating _PAGE_NUMA bit"), architecture like ppc64 doesn't do > tlb flush in set_pte/pmd functions. > > So when dealing with existing pte in clear_soft_dirty, the pte must > be cleared before being modified. Note that this is true of more than powerpc afaik. There's is a general rule that we don't "restrict" a PTE access permissions without first clearing it, due to various races. > Signed-off-by: Laurent Dufour > CC: Aneesh Kumar K.V > --- > fs/proc/task_mmu.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index e2d46adb54b4..c9454ee39b28 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -753,19 +753,20 @@ static inline void clear_soft_dirty(struct > vm_area_struct *vma, > pte_t ptent = *pte; > > if (pte_present(ptent)) { > + ptent = ptep_modify_prot_start(vma->vm_mm, addr, > pte); > ptent = pte_wrprotect(ptent); > ptent = pte_clear_flags(ptent, _PAGE_SOFT_DIRTY); > + ptep_modify_prot_commit(vma->vm_mm, addr, pte, > ptent); > } else if (is_swap_pte(ptent)) { > ptent = pte_swp_clear_soft_dirty(ptent); > + set_pte_at(vma->vm_mm, addr, pte, ptent); > } > - > - set_pte_at(vma->vm_mm, addr, pte, ptent); > } > > static inline void clear_soft_dirty_pmd(struct vm_area_struct *vma, > unsigned long addr, pmd_t *pmdp) > { > - pmd_t pmd = *pmdp; > + pmd_t pmd = pmdp_huge_get_and_clear(vma->vm_mm, addr, pmdp); > > pmd = pmd_wrprotect(pmd); > pmd = pmd_clear_flags(pmd, _PAGE_SOFT_DIRTY);