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Violators will be prosecuted for from ; Fri, 16 Jun 2017 18:52:51 +0100 From: Laurent Dufour Subject: [RFC v5 04/11] mm: VMA sequence count Date: Fri, 16 Jun 2017 19:52:28 +0200 In-Reply-To: <1497635555-25679-1-git-send-email-ldufour@linux.vnet.ibm.com> References: <1497635555-25679-1-git-send-email-ldufour@linux.vnet.ibm.com> Message-Id: <1497635555-25679-5-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 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 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] Signed-off-by: Laurent Dufour --- include/linux/mm_types.h | 1 + mm/memory.c | 2 ++ mm/mmap.c | 13 +++++++++++++ 3 files changed, 16 insertions(+) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 45cdb27791a3..8945743e4609 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -342,6 +342,7 @@ struct vm_area_struct { struct mempolicy *vm_policy; /* NUMA policy for the VMA */ #endif struct vm_userfaultfd_ctx vm_userfaultfd_ctx; + seqcount_t vm_sequence; }; struct core_thread { diff --git a/mm/memory.c b/mm/memory.c index f1132f7931ef..5d259cd67a83 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1379,6 +1379,7 @@ void unmap_page_range(struct mmu_gather *tlb, unsigned long next; BUG_ON(addr >= end); + write_seqcount_begin(&vma->vm_sequence); tlb_start_vma(tlb, vma); pgd = pgd_offset(vma->vm_mm, addr); do { @@ -1388,6 +1389,7 @@ 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); + write_seqcount_end(&vma->vm_sequence); } diff --git a/mm/mmap.c b/mm/mmap.c index f82741e199c0..9f86356d0012 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -543,6 +543,8 @@ void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma, else mm->highest_vm_end = vma->vm_end; + seqcount_init(&vma->vm_sequence); + /* * 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 @@ -677,6 +679,10 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, long adjust_next = 0; int remove_next = 0; + write_seqcount_begin(&vma->vm_sequence); + if (next) + write_seqcount_begin_nested(&next->vm_sequence, SINGLE_DEPTH_NESTING); + if (next && !insert) { struct vm_area_struct *exporter = NULL, *importer = NULL; @@ -888,6 +894,7 @@ 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); + write_seqcount_end(&next->vm_sequence); /* * In mprotect's case 6 (see comments on vma_merge), * we must remove another next too. It would clutter @@ -901,6 +908,8 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, * "vma->vm_next" gap must be updated. */ next = vma->vm_next; + if (next) + write_seqcount_begin_nested(&next->vm_sequence, SINGLE_DEPTH_NESTING); } else { /* * For the scope of the comment "next" and @@ -947,6 +956,10 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, if (insert && file) uprobe_mmap(insert); + if (next) + write_seqcount_end(&next->vm_sequence); + write_seqcount_end(&vma->vm_sequence); + 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