7 files changed, 44 insertions, 2 deletions

diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
index 2704729777ef..96e970485b6c 100644
--- a/include/linux/mm_inline.h
+++ b/include/linux/mm_inline.h
@@ -1,3 +1,28 @@
+#ifndef LINUX_MM_INLINE_H
+#define LINUX_MM_INLINE_H
+
+/**
+ * page_is_file_cache - should the page be on a file LRU or anon LRU?
+ * @page: the page to test
+ *
+ * Returns !0 if @page is page cache page backed by a regular filesystem,
+ * or 0 if @page is anonymous, tmpfs or otherwise ram or swap backed.
+ * Used by functions that manipulate the LRU lists, to sort a page
+ * onto the right LRU list.
+ *
+ * We would like to get this info without a page flag, but the state
+ * needs to survive until the page is last deleted from the LRU, which
+ * could be as far down as __page_cache_release.
+ */
+static inline int page_is_file_cache(struct page *page)
+{
+        if (PageSwapBacked(page))
+                return 0;
+
+        /* The page is page cache backed by a normal filesystem. */
+        return 1;
+}
+
 static inline void
 add_page_to_lru_list(struct zone *zone, struct page *page, enum lru_list l)
 {
@@ -65,3 +90,5 @@ static inline enum lru_list page_lru(struct page *page)
 
         return lru;
 }
+
+#endif
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index c74d3e875314..57b688cfb5e2 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -93,6 +93,7 @@ enum pageflags {
         PG_mappedtodisk,        /* Has blocks allocated on-disk */
         PG_reclaim,             /* To be reclaimed asap */
         PG_buddy,               /* Page is free, on buddy lists */
+        PG_swapbacked,          /* Page is backed by RAM/swap */
 #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
         PG_uncached,            /* Page has been mapped as uncached */
 #endif
@@ -176,6 +177,7 @@ PAGEFLAG(SavePinned, savepinned);			/* Xen */
 PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved)
 PAGEFLAG(Private, private) __CLEARPAGEFLAG(Private, private)
         __SETPAGEFLAG(Private, private)
+PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked)
 
 __PAGEFLAG(SlobPage, slob_page)
 __PAGEFLAG(SlobFree, slob_free)
@@ -334,7 +336,8 @@ static inline void __ClearPageTail(struct page *page)
  * Flags checked in bad_page().  Pages on the free list should not have
  * these flags set.  It they are, there is a problem.
  */
-#define PAGE_FLAGS_CLEAR_WHEN_BAD (PAGE_FLAGS | 1 << PG_reclaim | 1 << PG_dirty)
+#define PAGE_FLAGS_CLEAR_WHEN_BAD (PAGE_FLAGS | \
+                1 << PG_reclaim | 1 << PG_dirty | 1 << PG_swapbacked)
 
 /*
  * Flags checked when a page is freed.  Pages being freed should not have
@@ -347,7 +350,8 @@ static inline void __ClearPageTail(struct page *page)
  * Pages being prepped should not have these flags set.  It they are, there
  * is a problem.
  */
-#define PAGE_FLAGS_CHECK_AT_PREP (PAGE_FLAGS | 1 << PG_reserved | 1 << PG_dirty)
+#define PAGE_FLAGS_CHECK_AT_PREP (PAGE_FLAGS | \
+                1 << PG_reserved | 1 << PG_dirty | 1 << PG_swapbacked)
 
 #endif /* !__GENERATING_BOUNDS_H */
 #endif  /* PAGE_FLAGS_H */
diff --git a/mm/memory.c b/mm/memory.c
index 1002f473f497..7512933dcc10 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1888,6 +1888,7 @@ gotten:
                 ptep_clear_flush_notify(vma, address, page_table);
                 set_pte_at(mm, address, page_table, entry);
                 update_mmu_cache(vma, address, entry);
+                SetPageSwapBacked(new_page);
                 lru_cache_add_active(new_page);
                 page_add_new_anon_rmap(new_page, vma, address);
 
@@ -2382,6 +2383,7 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
         if (!pte_none(*page_table))
                 goto release;
         inc_mm_counter(mm, anon_rss);
+        SetPageSwapBacked(page);
         lru_cache_add_active(page);
         page_add_new_anon_rmap(page, vma, address);
         set_pte_at(mm, address, page_table, entry);
@@ -2523,6 +2525,7 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
                 set_pte_at(mm, address, page_table, entry);
                 if (anon) {
                         inc_mm_counter(mm, anon_rss);
+                        SetPageSwapBacked(page);
                         lru_cache_add_active(page);
                         page_add_new_anon_rmap(page, vma, address);
                 } else {
diff --git a/mm/migrate.c b/mm/migrate.c
index ad15b5ef2599..c07327487111 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -572,6 +572,8 @@ static int move_to_new_page(struct page *newpage, struct page *page)
         /* Prepare mapping for the new page.*/
         newpage->index = page->index;
         newpage->mapping = page->mapping;
+        if (PageSwapBacked(page))
+                SetPageSwapBacked(newpage);
 
         mapping = page_mapping(page);
         if (!mapping)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ee7a96ef40dc..2099904d6cc4 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -462,6 +462,8 @@ static inline int free_pages_check(struct page *page)
                 bad_page(page);
         if (PageDirty(page))
                 __ClearPageDirty(page);
+        if (PageSwapBacked(page))
+                __ClearPageSwapBacked(page);
         /*
          * For now, we report if PG_reserved was found set, but do not
          * clear it, and do not free the page.  But we shall soon need
diff --git a/mm/shmem.c b/mm/shmem.c
index d87958a5f03e..fd421ed703ed 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1367,6 +1367,7 @@ repeat:
                                 error = -ENOMEM;
                                 goto failed;
                         }
+                        SetPageSwapBacked(filepage);
 
                         /* Precharge page while we can wait, compensate after */
                         error = mem_cgroup_cache_charge(filepage, current->mm,
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 797c3831cbec..7a3ece0b5a3b 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -75,6 +75,7 @@ int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)
         BUG_ON(!PageLocked(page));
         BUG_ON(PageSwapCache(page));
         BUG_ON(PagePrivate(page));
+        BUG_ON(!PageSwapBacked(page));
         error = radix_tree_preload(gfp_mask);
         if (!error) {
                 page_cache_get(page);
@@ -303,6 +304,7 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
                  * May fail (-ENOMEM) if radix-tree node allocation failed.
                  */
                 set_page_locked(new_page);
+                SetPageSwapBacked(new_page);
                 err = add_to_swap_cache(new_page, entry, gfp_mask & GFP_KERNEL);
                 if (likely(!err)) {
                         /*
@@ -312,6 +314,7 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
                         swap_readpage(NULL, new_page);
                         return new_page;
                 }
+                ClearPageSwapBacked(new_page);
                 clear_page_locked(new_page);
                 swap_free(entry);
         } while (err != -ENOMEM);