[PATCH] mm: schedule find_trylock_page() removal

find_trylock_page() is an odd interface in that it doesn't take a reference
like the others.  Now that XFS no longer uses it, and its last remaining
caller actually wants an elevated refcount, opencode that callsite and
schedule find_trylock_page() for removal.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Documentation/feature-removal-schedule.txt

@@ -241,3 +241,15 @@ Why:	The USB subsystem has changed a lot over time, and it has been
 Who:	Greg Kroah-Hartman <gregkh@suse.de>
 
 ---------------------------
+
+What:	find_trylock_page
+When:	January 2007
+Why:	The interface no longer has any callers left in the kernel. It
+	is an odd interface (compared with other find_*_page functions), in
+	that it does not take a refcount to the page, only the page lock.
+	It should be replaced with find_get_page or find_lock_page if possible.
+	This feature removal can be reevaluated if users of the interface
+	cannot cleanly use something else.
+Who:	Nick Piggin <npiggin@suse.de>
+
+---------------------------

include/linux/pagemap.h

@@ -72,8 +72,8 @@ extern struct page * find_get_page(struct address_space *mapping,
 				unsigned long index);
 extern struct page * find_lock_page(struct address_space *mapping,
 				unsigned long index);
-extern struct page * find_trylock_page(struct address_space *mapping,
-				unsigned long index);
+extern __deprecated_for_modules struct page * find_trylock_page(
+			struct address_space *mapping, unsigned long index);
 extern struct page * find_or_create_page(struct address_space *mapping,
 				unsigned long index, gfp_t gfp_mask);
 unsigned find_get_pages(struct address_space *mapping, pgoff_t start,

mm/swapfile.c

@@ -397,18 +397,24 @@ void free_swap_and_cache(swp_entry_t entry)
 
 	p = swap_info_get(entry);
 	if (p) {
-		if (swap_entry_free(p, swp_offset(entry)) == 1)
-			page = find_trylock_page(&swapper_space, entry.val);
+		if (swap_entry_free(p, swp_offset(entry)) == 1) {
+			page = find_get_page(&swapper_space, entry.val);
+			if (page && unlikely(TestSetPageLocked(page))) {
+				page_cache_release(page);
+				page = NULL;
+			}
+		}
 		spin_unlock(&swap_lock);
 	}
 	if (page) {
 		int one_user;
 
 		BUG_ON(PagePrivate(page));
-		page_cache_get(page);
 		one_user = (page_count(page) == 2);
 		/* Only cache user (+us), or swap space full? Free it! */
-		if (!PageWriteback(page) && (one_user || vm_swap_full())) {
+		/* Also recheck PageSwapCache after page is locked (above) */
+		if (PageSwapCache(page) && !PageWriteback(page) &&
+					(one_user || vm_swap_full())) {
 			delete_from_swap_cache(page);
 			SetPageDirty(page);
 		}