From patchwork Tue Apr 17 14:33:12 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Laurent Dufour X-Patchwork-Id: 899394 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 40QT2Y5SWBz9ry1 for ; Wed, 18 Apr 2018 01:00:37 +1000 (AEST) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.vnet.ibm.com Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 40QT2Y4CPvzF21Q for ; Wed, 18 Apr 2018 01:00:37 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.vnet.ibm.com X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Authentication-Results: lists.ozlabs.org; spf=none (mailfrom) smtp.mailfrom=linux.vnet.ibm.com (client-ip=148.163.158.5; helo=mx0a-001b2d01.pphosted.com; envelope-from=ldufour@linux.vnet.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.vnet.ibm.com Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 40QSS02J8JzF20r for ; Wed, 18 Apr 2018 00:34:08 +1000 (AEST) Received: from pps.filterd (m0098417.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w3HESxb8121658 for ; Tue, 17 Apr 2018 10:34:05 -0400 Received: from e06smtp10.uk.ibm.com (e06smtp10.uk.ibm.com [195.75.94.106]) by mx0a-001b2d01.pphosted.com with ESMTP id 2hdj1637mp-1 (version=TLSv1.2 cipher=AES256-SHA256 bits=256 verify=NOT) for ; Tue, 17 Apr 2018 10:34:04 -0400 Received: from localhost by e06smtp10.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Tue, 17 Apr 2018 15:33:53 +0100 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w3HEXr1r63635710; Tue, 17 Apr 2018 14:33:53 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4E198A4051; Tue, 17 Apr 2018 15:26:02 +0100 (BST) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3402AA404D; Tue, 17 Apr 2018 15:26:00 +0100 (BST) Received: from nimbus.lab.toulouse-stg.fr.ibm.com (unknown [9.145.171.143]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 17 Apr 2018 15:26:00 +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 , benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@samba.org, Thomas Gleixner , Ingo Molnar , hpa@zytor.com, Will Deacon , Sergey Senozhatsky , Andrea Arcangeli , Alexei Starovoitov , kemi.wang@intel.com, sergey.senozhatsky.work@gmail.com, Daniel Jordan , David Rientjes , Jerome Glisse , Ganesh Mahendran Subject: [PATCH v10 06/25] mm: make pte_unmap_same compatible with SPF Date: Tue, 17 Apr 2018 16:33:12 +0200 X-Mailer: git-send-email 2.7.4 In-Reply-To: <1523975611-15978-1-git-send-email-ldufour@linux.vnet.ibm.com> References: <1523975611-15978-1-git-send-email-ldufour@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18041714-0040-0000-0000-0000042FFFAB X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18041714-0041-0000-0000-000026340AEF Message-Id: <1523975611-15978-7-git-send-email-ldufour@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2018-04-17_07:, , 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-1804170131 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-kernel@vger.kernel.org, npiggin@gmail.com, linux-mm@kvack.org, paulmck@linux.vnet.ibm.com, Tim Chen , haren@linux.vnet.ibm.com, khandual@linux.vnet.ibm.com Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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 | 1 + mm/memory.c | 39 ++++++++++++++++++++++++++++----------- 2 files changed, 29 insertions(+), 11 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 4d1aff80669c..714da99d77a3 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1208,6 +1208,7 @@ 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 | \ diff --git a/mm/memory.c b/mm/memory.c index 0b9a51f80e0e..f86efcb8e268 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2309,21 +2309,29 @@ 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) @@ -2912,10 +2920,19 @@ 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))) {