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Shutemov" , Peter Zijlstra Cc: Linux MM , Michal Hocko 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) --- include/linux/mm_types.h | 1 + mm/memory.c | 2 ++ mm/mmap.c | 12 ++++++++++++ 3 files changed, 15 insertions(+) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 903200f4ec41..620719bef808 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -358,6 +358,7 @@ 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 d19800904272..ec32cf710403 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1290,6 +1290,7 @@ 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 { @@ -1299,6 +1300,7 @@ void unmap_page_range(struct mmu_gather *tlb, next = zap_pud_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 ca9d91bca0d6..c2be9bd0ad92 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -514,6 +514,8 @@ 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 @@ -629,6 +631,10 @@ 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; @@ -802,7 +808,9 @@ again: * we must remove another next too. It would clutter * up the code too much to do both in one go. */ + write_seqcount_end(&next->vm_sequence); next = vma->vm_next; + write_seqcount_begin_nested(&next->vm_sequence, SINGLE_DEPTH_NESTING); if (remove_next == 2) { remove_next = 1; end = next->vm_end; @@ -816,6 +824,10 @@ again: 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. 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