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Violators will be prosecuted for from ; Mon, 9 Oct 2017 11:08:19 +0100 From: Laurent Dufour Subject: [PATCH v4 04/20] mm: VMA sequence count Date: Mon, 9 Oct 2017 12:07:36 +0200 In-Reply-To: <1507543672-25821-1-git-send-email-ldufour@linux.vnet.ibm.com> References: <1507543672-25821-1-git-send-email-ldufour@linux.vnet.ibm.com> Message-Id: <1507543672-25821-5-git-send-email-ldufour@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: paulmck@linux.vnet.ibm.com, peterz@infradead.org, akpm@linux-foundation.org, kirill@shutemov.name, ak@linux.intel.com, mhocko@kernel.org, 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 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, Tim Chen , linuxppc-dev@lists.ozlabs.org, x86@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 __HAVE_ARCH_CALL_SPF] [Introduce vm_write_* inline function depending on __HAVE_ARCH_CALL_SPF] [Fix lock dependency between mapping->i_mmap_rwsem and vma->vm_sequence by using vm_raw_write* functions] Signed-off-by: Laurent Dufour Fix locked by raw function undo lockdep fix as raw services are now used --- include/linux/mm.h | 41 +++++++++++++++++++++++++++++++++++++++++ include/linux/mm_types.h | 3 +++ mm/memory.c | 2 ++ mm/mmap.c | 40 +++++++++++++++++++++++++++++++++++++--- 4 files changed, 83 insertions(+), 3 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index fb3477f7f742..aa06332fc01e 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1349,6 +1349,47 @@ static inline int fixup_user_fault(struct task_struct *tsk, } #endif +#ifdef __HAVE_ARCH_CALL_SPF +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 /* __HAVE_ARCH_CALL_SPF */ + 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 d1e5062b0c00..6736feb8cb28 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -346,6 +346,9 @@ struct vm_area_struct { struct mempolicy *vm_policy; /* NUMA policy for the VMA */ #endif struct vm_userfaultfd_ctx vm_userfaultfd_ctx; +#ifdef __HAVE_ARCH_CALL_SPF + seqcount_t vm_sequence; +#endif } __randomize_layout; struct core_thread { diff --git a/mm/memory.c b/mm/memory.c index 27f626c229f7..ac6822356a37 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1504,6 +1504,7 @@ 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 { @@ -1513,6 +1514,7 @@ 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 2f3971a051c6..ec896358fc5a 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -558,6 +558,10 @@ void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma, else mm->highest_vm_end = vm_end_gap(vma); +#ifdef __HAVE_ARCH_CALL_SPF + seqcount_init(&vma->vm_sequence); +#endif + /* * vma->vm_prev wasn't known when we followed the rbtree to find the * correct insertion point for that vma. As a result, we could not @@ -692,6 +696,30 @@ 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; @@ -903,6 +931,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, mm->map_count--; mpol_put(vma_policy(next)); kmem_cache_free(vm_area_cachep, next); + vm_raw_write_end(next); /* * In mprotect's case 6 (see comments on vma_merge), * we must remove another next too. It would clutter @@ -916,6 +945,8 @@ 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 @@ -933,10 +964,9 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, remove_next = 1; end = next->vm_end; goto again; - } - else if (next) + } else if (next) { vma_gap_update(next); - else { + } else { /* * If remove_next == 2 we obviously can't * reach this path. @@ -962,6 +992,10 @@ 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org