4 files changed, 57 insertions, 0 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7c6dfd2faa69..7cdac1676b59 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -805,6 +805,17 @@ static inline void *page_rmapping(struct page *page)
         return (void *)((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS);
 }
 
+extern struct address_space *__page_file_mapping(struct page *);
+
+static inline
+struct address_space *page_file_mapping(struct page *page)
+{
+        if (unlikely(PageSwapCache(page)))
+                return __page_file_mapping(page);
+
+        return page->mapping;
+}
+
 static inline int PageAnon(struct page *page)
 {
         return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
@@ -821,6 +832,20 @@ static inline pgoff_t page_index(struct page *page)
         return page->index;
 }
 
+extern pgoff_t __page_file_index(struct page *page);
+
+/*
+ * Return the file index of the page. Regular pagecache pages use ->index
+ * whereas swapcache pages use swp_offset(->private)
+ */
+static inline pgoff_t page_file_index(struct page *page)
+{
+        if (unlikely(PageSwapCache(page)))
+                return __page_file_index(page);
+
+        return page->index;
+}
+
 /*
  * Return true if this page is mapped into pagetables.
  */
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 7cfad3bbb0cc..e42c762f0dc7 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -286,6 +286,11 @@ static inline loff_t page_offset(struct page *page)
         return ((loff_t)page->index) << PAGE_CACHE_SHIFT;
 }
 
+static inline loff_t page_file_offset(struct page *page)
+{
+        return ((loff_t)page_file_index(page)) << PAGE_CACHE_SHIFT;
+}
+
 extern pgoff_t linear_hugepage_index(struct vm_area_struct *vma,
                                      unsigned long address);
 
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 9a16bb1cefd1..e62425ded2ed 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -356,6 +356,7 @@ extern unsigned int count_swap_pages(int, int);
 extern sector_t map_swap_page(struct page *, struct block_device **);
 extern sector_t swapdev_block(int, pgoff_t);
 extern int page_swapcount(struct page *);
+extern struct swap_info_struct *page_swap_info(struct page *);
 extern int reuse_swap_page(struct page *);
 extern int try_to_free_swap(struct page *);
 struct backing_dev_info;
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 71373d03fcee..f89af5ba2eb2 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -33,6 +33,7 @@
 #include <linux/oom.h>
 #include <linux/frontswap.h>
 #include <linux/swapfile.h>
+#include <linux/export.h>
 
 #include <asm/pgtable.h>
 #include <asm/tlbflush.h>
@@ -2285,6 +2286,31 @@ int swapcache_prepare(swp_entry_t entry)
         return __swap_duplicate(entry, SWAP_HAS_CACHE);
 }
 
+struct swap_info_struct *page_swap_info(struct page *page)
+{
+        swp_entry_t swap = { .val = page_private(page) };
+        BUG_ON(!PageSwapCache(page));
+        return swap_info[swp_type(swap)];
+}
+
+/*
+ * out-of-line __page_file_ methods to avoid include hell.
+ */
+struct address_space *__page_file_mapping(struct page *page)
+{
+        VM_BUG_ON(!PageSwapCache(page));
+        return page_swap_info(page)->swap_file->f_mapping;
+}
+EXPORT_SYMBOL_GPL(__page_file_mapping);
+
+pgoff_t __page_file_index(struct page *page)
+{
+        swp_entry_t swap = { .val = page_private(page) };
+        VM_BUG_ON(!PageSwapCache(page));
+        return swp_offset(swap);
+}
+EXPORT_SYMBOL_GPL(__page_file_index);
+
 /*
  * add_swap_count_continuation - called when a swap count is duplicated
  * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's