[PATCH -mm 2/6] rmap: always add new vmas at the end

[Rik van Riel <riel@redhat.com>]

From: Andrea Arcangeli <aarcange@redhat.com>
Subject: always add new vmas at the end

Make sure to always add new VMAs at the end of the list.  This
is important so rmap_walk does not miss a VMA that was created
during the rmap_walk.

The old code got this right most of the time due to luck, but
was buggy when anon_vma_prepare reused a mergeable anon_vma.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
---

diff --git a/mm/rmap.c b/mm/rmap.c
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -149,7 +149,7 @@ int anon_vma_prepare(struct vm_area_stru
 			avc->anon_vma = anon_vma;
 			avc->vma = vma;
 			list_add(&avc->same_vma, &vma->anon_vma_chain);
-			list_add(&avc->same_anon_vma, &anon_vma->head);
+			list_add_tail(&avc->same_anon_vma, &anon_vma->head);
 			allocated = NULL;
 			avc = NULL;
 		}

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