The patch titled
rmap: always use anon_vma root pointer
has been added to the -mm tree. Its filename is
rmap-always-use-anon_vma-root-pointer.patch
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------------------------------------------------------
Subject: rmap: always use anon_vma root pointer
From: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Always use anon_vma->root pointer instead of anon_vma_chain.prev.
Also optimize the map-paths, if a mapping is already established no need
to overwrite it with root anon-vma list, we can keep the more finegrined
anon-vma and skip the overwrite: see the PageAnon check in !exclusive
case. This is also the optimization that hidden the ksm bug as this tends
to make ksm_might_need_to_copy skip the copy, but only the proper fix to
ksm_might_need_to_copy guarantees not triggering the ksm bug unless ksm is
in use. this is an optimization only...
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/rmap.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)
diff -puN mm/rmap.c~rmap-always-use-anon_vma-root-pointer mm/rmap.c
--- a/mm/rmap.c~rmap-always-use-anon_vma-root-pointer
+++ a/mm/rmap.c
@@ -777,15 +777,13 @@ static void __page_set_anon_rmap(struct
* If the page isn't exclusively mapped into this vma,
* we must use the _oldest_ possible anon_vma for the
* page mapping!
- *
- * So take the last AVC chain entry in the vma, which is
- * the deepest ancestor, and use the anon_vma from that.
*/
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;
+ anon_vma = anon_vma->root;
+ } else
+ BUG_ON(PageAnon(page));
anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
page->mapping = (struct address_space *) anon_vma;
_
Patches currently in -mm which might be from aarcange@xxxxxxxxxx are
linux-next.patch
hugetlb-call-mmu-notifiers-on-hugepage-cow.patch
define-madv_hugepage.patch
mmap-remove-unnecessary-lock-from-__vma_link.patch
rmap-always-add-new-vmas-at-the-end.patch
ksm-fix-ksm-swapin-time-optimization.patch
rmap-always-use-anon_vma-root-pointer.patch
rmap-resurrect-page_address_in_vma-anon_vma-check.patch
add-anon_vma-bug-checks.patch
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