path: root/mm/rmap.c
diff options
authorAndrea Arcangeli <aarcange@redhat.com>2010-08-09 17:19:09 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-08-09 20:44:58 -0700
commit288468c334e98aacbb7e2fb8bde6bc1adcd55e05 (patch)
treef64cfebd7fedfd4e53fd5d4474048d5475a339b9 /mm/rmap.c
parentba6f0ff3981e6263ab81ac512f04cca55b85ec81 (diff)
rmap: always use anon_vma root pointer
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... [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: Rik van Riel <riel@redhat.com> [kamezawa.hiroyu@jp.fujitsu.com: fix false positive BUG_ON in __page_set_anon_rmap] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/rmap.c')
1 files changed, 12 insertions, 6 deletions
diff --git a/mm/rmap.c b/mm/rmap.c
index dce74a9efdd..f5d6799b8a7 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -767,14 +767,20 @@ static void __page_set_anon_rmap(struct page *page,
* 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 {
+ /*
+ * In this case, swapped-out-but-not-discarded swap-cache
+ * is remapped. So, no need to update page->mapping here.
+ * We convice anon_vma poitned by page->mapping is not obsolete
+ * because vma->anon_vma is necessary to be a family of it.
+ */
+ if (PageAnon(page))
+ return;
anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;