hugetlb, rmap: always use anon_vma root pointer
This patch applies Andrea's fix given by the following patch into hugepage
rmapping code:
commit 288468c334e98aacbb7e2fb8bde6bc1adcd55e05
Author: Andrea Arcangeli <aarcange@redhat.com>
Date: Mon Aug 9 17:19:09 2010 -0700
This patch uses anon_vma->root and avoids unnecessary overwriting when
anon_vma is already set up.
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/rmap.c b/mm/rmap.c
index f6f0d2d..2854857 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1564,13 +1564,14 @@
struct vm_area_struct *vma, unsigned long address, int exclusive)
{
struct anon_vma *anon_vma = vma->anon_vma;
+
BUG_ON(!anon_vma);
- if (!exclusive) {
- struct anon_vma_chain *avc;
- avc = list_entry(vma->anon_vma_chain.prev,
- struct anon_vma_chain, same_vma);
- anon_vma = avc->anon_vma;
- }
+
+ if (PageAnon(page))
+ return;
+ if (!exclusive)
+ anon_vma = anon_vma->root;
+
anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
page->mapping = (struct address_space *) anon_vma;
page->index = linear_page_index(vma, address);