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[148.163.156.1]) by mx.google.com with ESMTPS id z17-v6si8911qtz.71.2018.05.17.04.07.06 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 17 May 2018 04:07:07 -0700 (PDT) Received-SPF: neutral (google.com: 148.163.156.1 is neither permitted nor denied by best guess record for domain of ldufour@linux.vnet.ibm.com) client-ip=148.163.156.1; Authentication-Results: mx.google.com; spf=neutral (google.com: 148.163.156.1 is neither permitted nor denied by best guess record for domain of ldufour@linux.vnet.ibm.com) smtp.mailfrom=ldufour@linux.vnet.ibm.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=ibm.com Received: from pps.filterd (m0098399.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w4HB56qm103332 for ; Thu, 17 May 2018 07:07:06 -0400 Received: from e06smtp14.uk.ibm.com (e06smtp14.uk.ibm.com [195.75.94.110]) by mx0a-001b2d01.pphosted.com with ESMTP id 2j17g8u5e2-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 17 May 2018 07:07:04 -0400 Received: from localhost by e06smtp14.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Thu, 17 May 2018 12:06:52 +0100 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w4HB6pkp2818502; Thu, 17 May 2018 11:06:51 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4764E4C058; Thu, 17 May 2018 11:58:40 +0100 (BST) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id CD31A4C044; Thu, 17 May 2018 11:58:38 +0100 (BST) Received: from nimbus.lab.toulouse-stg.fr.ibm.com (unknown [9.101.4.33]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 17 May 2018 11:58:38 +0100 (BST) From: Laurent Dufour To: akpm@linux-foundation.org, mhocko@kernel.org, peterz@infradead.org, kirill@shutemov.name, ak@linux.intel.com, dave@stgolabs.net, jack@suse.cz, Matthew Wilcox , khandual@linux.vnet.ibm.com, aneesh.kumar@linux.vnet.ibm.com, benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@samba.org, Thomas Gleixner , Ingo Molnar , hpa@zytor.com, Will Deacon , Sergey Senozhatsky , sergey.senozhatsky.work@gmail.com, Andrea Arcangeli , Alexei Starovoitov , kemi.wang@intel.com, Daniel Jordan , David Rientjes , Jerome Glisse , Ganesh Mahendran , Minchan Kim , Punit Agrawal , vinayak menon , Yang Shi Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, haren@linux.vnet.ibm.com, npiggin@gmail.com, bsingharora@gmail.com, paulmck@linux.vnet.ibm.com, Tim Chen , linuxppc-dev@lists.ozlabs.org, x86@kernel.org Subject: [PATCH v11 07/26] mm: make pte_unmap_same compatible with SPF Date: Thu, 17 May 2018 13:06:14 +0200 X-Mailer: git-send-email 2.7.4 In-Reply-To: <1526555193-7242-1-git-send-email-ldufour@linux.vnet.ibm.com> References: <1526555193-7242-1-git-send-email-ldufour@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18051711-0044-0000-0000-00000553750F X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18051711-0045-0000-0000-00002894E8EC Message-Id: <1526555193-7242-8-git-send-email-ldufour@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2018-05-17_05:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1805170100 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: X-Virus-Scanned: ClamAV using ClamSMTP pte_unmap_same() is making the assumption that the page table are still around because the mmap_sem is held. This is no more the case when running a speculative page fault and additional check must be made to ensure that the final page table are still there. This is now done by calling pte_spinlock() to check for the VMA's consistency while locking for the page tables. This is requiring passing a vm_fault structure to pte_unmap_same() which is containing all the needed parameters. As pte_spinlock() may fail in the case of a speculative page fault, if the VMA has been touched in our back, pte_unmap_same() should now return 3 cases : 1. pte are the same (0) 2. pte are different (VM_FAULT_PTNOTSAME) 3. a VMA's changes has been detected (VM_FAULT_RETRY) The case 2 is handled by the introduction of a new VM_FAULT flag named VM_FAULT_PTNOTSAME which is then trapped in cow_user_page(). If VM_FAULT_RETRY is returned, it is passed up to the callers to retry the page fault while holding the mmap_sem. Acked-by: David Rientjes Signed-off-by: Laurent Dufour --- include/linux/mm.h | 4 +++- mm/memory.c | 39 ++++++++++++++++++++++++++++----------- 2 files changed, 31 insertions(+), 12 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 338b8a1afb02..113b572471ca 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1249,6 +1249,7 @@ static inline void clear_page_pfmemalloc(struct page *page) #define VM_FAULT_NEEDDSYNC 0x2000 /* ->fault did not modify page tables * and needs fsync() to complete (for * synchronous page faults in DAX) */ +#define VM_FAULT_PTNOTSAME 0x4000 /* Page table entries have changed */ #define VM_FAULT_ERROR (VM_FAULT_OOM | VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV | \ VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE | \ @@ -1267,7 +1268,8 @@ static inline void clear_page_pfmemalloc(struct page *page) { VM_FAULT_RETRY, "RETRY" }, \ { VM_FAULT_FALLBACK, "FALLBACK" }, \ { VM_FAULT_DONE_COW, "DONE_COW" }, \ - { VM_FAULT_NEEDDSYNC, "NEEDDSYNC" } + { VM_FAULT_NEEDDSYNC, "NEEDDSYNC" }, \ + { VM_FAULT_PTNOTSAME, "PTNOTSAME" } /* Encode hstate index for a hwpoisoned large page */ #define VM_FAULT_SET_HINDEX(x) ((x) << 12) diff --git a/mm/memory.c b/mm/memory.c index fa0d9493acac..75163c145c76 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2319,21 +2319,29 @@ static inline bool pte_map_lock(struct vm_fault *vmf) * parts, do_swap_page must check under lock before unmapping the pte and * proceeding (but do_wp_page is only called after already making such a check; * and do_anonymous_page can safely check later on). + * + * pte_unmap_same() returns: + * 0 if the PTE are the same + * VM_FAULT_PTNOTSAME if the PTE are different + * VM_FAULT_RETRY if the VMA has changed in our back during + * a speculative page fault handling. */ -static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd, - pte_t *page_table, pte_t orig_pte) +static inline int pte_unmap_same(struct vm_fault *vmf) { - int same = 1; + int ret = 0; + #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT) if (sizeof(pte_t) > sizeof(unsigned long)) { - spinlock_t *ptl = pte_lockptr(mm, pmd); - spin_lock(ptl); - same = pte_same(*page_table, orig_pte); - spin_unlock(ptl); + if (pte_spinlock(vmf)) { + if (!pte_same(*vmf->pte, vmf->orig_pte)) + ret = VM_FAULT_PTNOTSAME; + spin_unlock(vmf->ptl); + } else + ret = VM_FAULT_RETRY; } #endif - pte_unmap(page_table); - return same; + pte_unmap(vmf->pte); + return ret; } static inline void cow_user_page(struct page *dst, struct page *src, unsigned long va, struct vm_area_struct *vma) @@ -2922,10 +2930,19 @@ int do_swap_page(struct vm_fault *vmf) pte_t pte; int locked; int exclusive = 0; - int ret = 0; + int ret; - if (!pte_unmap_same(vma->vm_mm, vmf->pmd, vmf->pte, vmf->orig_pte)) + ret = pte_unmap_same(vmf); + if (ret) { + /* + * If pte != orig_pte, this means another thread did the + * swap operation in our back. + * So nothing else to do. + */ + if (ret == VM_FAULT_PTNOTSAME) + ret = 0; goto out; + } entry = pte_to_swp_entry(vmf->orig_pte); if (unlikely(non_swap_entry(entry))) {