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-rw-r--r--mm/ksm.c30
1 files changed, 28 insertions, 2 deletions
diff --git a/mm/ksm.c b/mm/ksm.c
index fd2db6a74d3c..983fbac24bda 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -706,8 +706,9 @@ again:
* case this node is no longer referenced, and should be freed;
* however, it might mean that the page is under page_ref_freeze().
* The __remove_mapping() case is easy, again the node is now stale;
- * but if page is swapcache in migrate_page_move_mapping(), it might
- * still be our page, in which case it's essential to keep the node.
+ * the same is in reuse_ksm_page() case; but if page is swapcache
+ * in migrate_page_move_mapping(), it might still be our page,
+ * in which case it's essential to keep the node.
*/
while (!get_page_unless_zero(page)) {
/*
@@ -2642,6 +2643,31 @@ again:
goto again;
}
+bool reuse_ksm_page(struct page *page,
+ struct vm_area_struct *vma,
+ unsigned long address)
+{
+#ifdef CONFIG_DEBUG_VM
+ if (WARN_ON(is_zero_pfn(page_to_pfn(page))) ||
+ WARN_ON(!page_mapped(page)) ||
+ WARN_ON(!PageLocked(page))) {
+ dump_page(page, "reuse_ksm_page");
+ return false;
+ }
+#endif
+
+ if (PageSwapCache(page) || !page_stable_node(page))
+ return false;
+ /* Prohibit parallel get_ksm_page() */
+ if (!page_ref_freeze(page, 1))
+ return false;
+
+ page_move_anon_rmap(page, vma);
+ page->index = linear_page_index(vma, address);
+ page_ref_unfreeze(page, 1);
+
+ return true;
+}
#ifdef CONFIG_MIGRATION
void ksm_migrate_page(struct page *newpage, struct page *oldpage)
{