mm: remove gfp_mask from add_to_swap

Remove gfp_mask argument from add_to_swap(): it's misleading because its
only caller, shrink_page_list(), is not atomic at that point; and in due
course (implementing discard) we'll sometimes want to allocate some memory
with GFP_NOIO (as is used in swap_writepage) when allocating swap.

No change to the gfp_mask passed down to add_to_swap_cache(): still use
__GFP_HIGH without __GFP_WAIT (with nomemalloc and nowarn as before):
though it's not obvious if that's the best combination to ask for here.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Robin Holt <holt@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/swap.h

@@ -278,7 +278,7 @@ extern void end_swap_bio_read(struct bio *bio, int err);
 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(struct page *);
 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 *);

mm/swap_state.c

@@ -128,7 +128,7 @@ void __delete_from_swap_cache(struct page *page)
  * Allocate swap space for the page and add the page to the
  * swap cache.  Caller needs to hold the page lock. 
  */
-int add_to_swap(struct page * page, gfp_t gfp_mask)
+int add_to_swap(struct page *page)
 {
 	swp_entry_t entry;
 	int err;
@@ -153,7 +153,7 @@ int add_to_swap(struct page * page, gfp_t gfp_mask)
 		 * Add it to the swap cache and mark it dirty
 		 */
 		err = add_to_swap_cache(page, entry,
-				gfp_mask|__GFP_NOMEMALLOC|__GFP_NOWARN);
+				__GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN);
 
 		switch (err) {
 		case 0:				/* Success */

mm/vmscan.c

@@ -625,7 +625,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 		if (PageAnon(page) && !PageSwapCache(page)) {
 			if (!(sc->gfp_mask & __GFP_IO))
 				goto keep_locked;
-			if (!add_to_swap(page, GFP_ATOMIC))
+			if (!add_to_swap(page))
 				goto activate_locked;
 			may_enter_fs = 1;
 		}