tmpfs: move swap swizzling into shmem

move_to_swap_cache and move_from_swap_cache functions (which swizzle a page
between tmpfs page cache and swap cache, to avoid page copying) are only used
by shmem.c; and our subsequent fix for unionfs needs different treatments in
the two instances of move_from_swap_cache.  Move them from swap_state.c into
their callsites shmem_writepage, shmem_unuse_inode and shmem_getpage, making
add_to_swap_cache externally visible.

shmem.c likes to say set_page_dirty where swap_state.c liked to say
SetPageDirty: respect that diversity, which __set_page_dirty_no_writeback
makes moot (and implies we should lose that "shift page from clean_pages to
dirty_pages list" comment: it's on neither).

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 11 deletions

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 16fd1209e9fa..353153ea0bd5 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -220,11 +220,9 @@ extern struct address_space swapper_space;
 #define total_swapcache_pages  swapper_space.nrpages
 extern void show_swap_cache_info(void);
 extern int add_to_swap(struct page *, gfp_t);
+extern int add_to_swap_cache(struct page *, swp_entry_t, gfp_t);
 extern void __delete_from_swap_cache(struct page *);
 extern void delete_from_swap_cache(struct page *);
-extern int move_to_swap_cache(struct page *, swp_entry_t);
-extern int move_from_swap_cache(struct page *, unsigned long,
-                struct address_space *);
 extern void free_page_and_swap_cache(struct page *);
 extern void free_pages_and_swap_cache(struct page **, int);
 extern struct page *lookup_swap_cache(swp_entry_t);
@@ -319,15 +317,10 @@ static inline struct page *lookup_swap_cache(swp_entry_t swp)
 
 #define can_share_swap_page(p)                  (page_mapcount(p) == 1)
 
-static inline int move_to_swap_cache(struct page *page, swp_entry_t entry)
+static inline int add_to_swap_cache(struct page *page, swp_entry_t entry,
+                                                        gfp_t gfp_mask)
 {
-        return 1;
-}
-
-static inline int move_from_swap_cache(struct page *page, unsigned long index,
-                                        struct address_space *mapping)
-{
-        return 1;
+        return -1;
 }
 
 static inline void __delete_from_swap_cache(struct page *page)