From 1583aa278f5f6a58b6ff8e9e703d0cca2b953d97 Mon Sep 17 00:00:00 2001 From: Li Xinhai Date: Wed, 24 Feb 2021 12:04:53 -0800 Subject: [PATCH] mm: mremap: unlink anon_vmas when mremap with MREMAP_DONTUNMAP success mremap with MREMAP_DONTUNMAP can move all page table entries to new vma, which means all pages allocated for the old vma are not relevant to it anymore, and the relevant anon_vma links needs to be unlinked, in nature the old vma is much like been freshly created and have no pages been fault in. But we should not do unlink, if the new vma has effectively merged with the old one. [lixinhai.lxh@gmail.com: v2] Link: https://lkml.kernel.org/r/20210127083917.309264-2-lixinhai.lxh@gmail.com Link: https://lkml.kernel.org/r/20210119075126.3513154-2-lixinhai.lxh@gmail.com Signed-off-by: Li Xinhai Cc: Brian Geffon Cc: Lokesh Gidra Cc: Minchan Kim Cc: Kirill A. Shutemov Cc: Vlastimil Babka Cc: Andrea Arcangeli Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mremap.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/mm/mremap.c b/mm/mremap.c index 47192691fe32..ec8f840399ed 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -593,6 +593,14 @@ static unsigned long move_vma(struct vm_area_struct *vma, /* We always clear VM_LOCKED[ONFAULT] on the old vma */ vma->vm_flags &= VM_LOCKED_CLEAR_MASK; + /* + * anon_vma links of the old vma is no longer needed after its page + * table has been moved. + */ + if (new_vma != vma && vma->vm_start == old_addr && + vma->vm_end == (old_addr + old_len)) + unlink_anon_vmas(vma); + /* Because we won't unmap we don't need to touch locked_vm */ return new_addr; } -- 2.39.5