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-rw-r--r--include/linux/mm.h17
1 files changed, 16 insertions, 1 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 24c395694f4d..1202cd3121e1 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -620,13 +620,22 @@ void page_address_init(void);
/*
* On an anonymous page mapped into a user virtual memory area,
* page->mapping points to its anon_vma, not to a struct address_space;
- * with the PAGE_MAPPING_ANON bit set to distinguish it.
+ * with the PAGE_MAPPING_ANON bit set to distinguish it. See rmap.h.
+ *
+ * On an anonymous page in a VM_MERGEABLE area, if CONFIG_KSM is enabled,
+ * the PAGE_MAPPING_KSM bit may be set along with the PAGE_MAPPING_ANON bit;
+ * and then page->mapping points, not to an anon_vma, but to a private
+ * structure which KSM associates with that merged page. See ksm.h.
+ *
+ * PAGE_MAPPING_KSM without PAGE_MAPPING_ANON is currently never used.
*
* Please note that, confusingly, "page_mapping" refers to the inode
* address_space which maps the page from disk; whereas "page_mapped"
* refers to user virtual address space into which the page is mapped.
*/
#define PAGE_MAPPING_ANON 1
+#define PAGE_MAPPING_KSM 2
+#define PAGE_MAPPING_FLAGS (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM)
extern struct address_space swapper_space;
static inline struct address_space *page_mapping(struct page *page)
@@ -644,6 +653,12 @@ static inline struct address_space *page_mapping(struct page *page)
return mapping;
}
+/* Neutral page->mapping pointer to address_space or anon_vma or other */
+static inline void *page_rmapping(struct page *page)
+{
+ return (void *)((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS);
+}
+
static inline int PageAnon(struct page *page)
{
return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
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