[PATCHv2 22/59] mm/rmap: Clear vma->anon_vma on unlink_anon_vmas()

Kirill A. Shutemov
2019-07-31T15:19:15Z

If all pages in the VMA got unmapped there's no reason to link it into
original anon VMA hierarchy: it cannot possibly share any pages with
other VMA.

Set vma->anon_vma to NULL on unlink_anon_vmas(). With the change VMA
can be reused. The new anon VMA will be allocated on the first fault.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
mm/rmap.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index e5dfe2ae6b0d..911367b5fb40 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -400,8 +400,10 @@ void unlink_anon_vmas(struct vm_area_struct *vma)
list_del(&avc->same_vma);
anon_vma_chain_free(avc);
}
- if (vma->anon_vma)
+ if (vma->anon_vma) {
vma->anon_vma->degree--;
+ vma->anon_vma = NULL;
+ }
unlock_anon_vma_root(root);

/*
--
2.21.0