From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753520AbeDQOeR (ORCPT ); Tue, 17 Apr 2018 10:34:17 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:49764 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753436AbeDQOeL (ORCPT ); Tue, 17 Apr 2018 10:34:11 -0400 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 Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, haren@linux.vnet.ibm.com, khandual@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 v10 08/25] mm: VMA sequence count Date: Tue, 17 Apr 2018 16:33:14 +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: 18041714-0012-0000-0000-000005CBDCDA X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18041714-0013-0000-0000-000019482814 Message-Id: <1523975611-15978-9-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=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1804170131 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra Wrap the VMA modifications (vma_adjust/unmap_page_range) with sequence counts such that we can easily test if a VMA is changed. The unmap_page_range() one allows us to make assumptions about page-tables; when we find the seqcount hasn't changed we can assume page-tables are still valid. The flip side is that we cannot distinguish between a vma_adjust() and the unmap_page_range() -- where with the former we could have re-checked the vma bounds against the address. Signed-off-by: Peter Zijlstra (Intel) [Port to 4.12 kernel] [Build depends on CONFIG_SPECULATIVE_PAGE_FAULT] [Introduce vm_write_* inline function depending on CONFIG_SPECULATIVE_PAGE_FAULT] [Fix lock dependency between mapping->i_mmap_rwsem and vma->vm_sequence by using vm_raw_write* functions] [Fix a lock dependency warning in mmap_region() when entering the error path] [move sequence initialisation INIT_VMA()] Signed-off-by: Laurent Dufour --- include/linux/mm.h | 44 ++++++++++++++++++++++++++++++++++++++++++++ include/linux/mm_types.h | 3 +++ mm/memory.c | 2 ++ mm/mmap.c | 31 +++++++++++++++++++++++++++++++ 4 files changed, 80 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index efc1248b82bd..988daf7030c9 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1264,6 +1264,9 @@ struct zap_details { static inline void INIT_VMA(struct vm_area_struct *vma) { INIT_LIST_HEAD(&vma->anon_vma_chain); +#ifdef CONFIG_SPECULATIVE_PAGE_FAULT + seqcount_init(&vma->vm_sequence); +#endif } struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr, @@ -1386,6 +1389,47 @@ static inline void unmap_shared_mapping_range(struct address_space *mapping, unmap_mapping_range(mapping, holebegin, holelen, 0); } +#ifdef CONFIG_SPECULATIVE_PAGE_FAULT +static inline void vm_write_begin(struct vm_area_struct *vma) +{ + write_seqcount_begin(&vma->vm_sequence); +} +static inline void vm_write_begin_nested(struct vm_area_struct *vma, + int subclass) +{ + write_seqcount_begin_nested(&vma->vm_sequence, subclass); +} +static inline void vm_write_end(struct vm_area_struct *vma) +{ + write_seqcount_end(&vma->vm_sequence); +} +static inline void vm_raw_write_begin(struct vm_area_struct *vma) +{ + raw_write_seqcount_begin(&vma->vm_sequence); +} +static inline void vm_raw_write_end(struct vm_area_struct *vma) +{ + raw_write_seqcount_end(&vma->vm_sequence); +} +#else +static inline void vm_write_begin(struct vm_area_struct *vma) +{ +} +static inline void vm_write_begin_nested(struct vm_area_struct *vma, + int subclass) +{ +} +static inline void vm_write_end(struct vm_area_struct *vma) +{ +} +static inline void vm_raw_write_begin(struct vm_area_struct *vma) +{ +} +static inline void vm_raw_write_end(struct vm_area_struct *vma) +{ +} +#endif /* CONFIG_SPECULATIVE_PAGE_FAULT */ + extern int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, unsigned int gup_flags); extern int access_remote_vm(struct mm_struct *mm, unsigned long addr, diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 21612347d311..db5e9d630e7a 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -335,6 +335,9 @@ struct vm_area_struct { struct mempolicy *vm_policy; /* NUMA policy for the VMA */ #endif struct vm_userfaultfd_ctx vm_userfaultfd_ctx; +#ifdef CONFIG_SPECULATIVE_PAGE_FAULT + seqcount_t vm_sequence; +#endif } __randomize_layout; struct core_thread { diff --git a/mm/memory.c b/mm/memory.c index f86efcb8e268..f7fed053df80 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1503,6 +1503,7 @@ void unmap_page_range(struct mmu_gather *tlb, unsigned long next; BUG_ON(addr >= end); + vm_write_begin(vma); tlb_start_vma(tlb, vma); pgd = pgd_offset(vma->vm_mm, addr); do { @@ -1512,6 +1513,7 @@ void unmap_page_range(struct mmu_gather *tlb, next = zap_p4d_range(tlb, vma, pgd, addr, next, details); } while (pgd++, addr = next, addr != end); tlb_end_vma(tlb, vma); + vm_write_end(vma); } diff --git a/mm/mmap.c b/mm/mmap.c index 8bd9ae1dfacc..813e49589ea1 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -692,6 +692,30 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, long adjust_next = 0; int remove_next = 0; + /* + * Why using vm_raw_write*() functions here to avoid lockdep's warning ? + * + * Locked is complaining about a theoretical lock dependency, involving + * 3 locks: + * mapping->i_mmap_rwsem --> vma->vm_sequence --> fs_reclaim + * + * Here are the major path leading to this dependency : + * 1. __vma_adjust() mmap_sem -> vm_sequence -> i_mmap_rwsem + * 2. move_vmap() mmap_sem -> vm_sequence -> fs_reclaim + * 3. __alloc_pages_nodemask() fs_reclaim -> i_mmap_rwsem + * 4. unmap_mapping_range() i_mmap_rwsem -> vm_sequence + * + * So there is no way to solve this easily, especially because in + * unmap_mapping_range() the i_mmap_rwsem is grab while the impacted + * VMAs are not yet known. + * However, the way the vm_seq is used is guarantying that we will + * never block on it since we just check for its value and never wait + * for it to move, see vma_has_changed() and handle_speculative_fault(). + */ + vm_raw_write_begin(vma); + if (next) + vm_raw_write_begin(next); + if (next && !insert) { struct vm_area_struct *exporter = NULL, *importer = NULL; @@ -902,6 +926,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, anon_vma_merge(vma, next); mm->map_count--; mpol_put(vma_policy(next)); + vm_raw_write_end(next); kmem_cache_free(vm_area_cachep, next); /* * In mprotect's case 6 (see comments on vma_merge), @@ -916,6 +941,8 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, * "vma->vm_next" gap must be updated. */ next = vma->vm_next; + if (next) + vm_raw_write_begin(next); } else { /* * For the scope of the comment "next" and @@ -962,6 +989,10 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, if (insert && file) uprobe_mmap(insert); + if (next && next != vma) + vm_raw_write_end(next); + vm_raw_write_end(vma); + validate_mm(mm); return 0; -- 2.7.4