From: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Subject: 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...
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>
diff --git a/mm/rmap.c b/mm/rmap.c
index 006f223..2d9504d 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -776,15 +776,13 @@ 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
+ BUG_ON(PageAnon(page));
anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
page->mapping = (struct address_space *) anon_vma;
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxxx For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>