[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>

3 files changed, 24 insertions, 6 deletions

diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index 495858b236b6..a92b10bb0b03 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/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>
+
+---------------------------
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 839f0b3c23aa..9539efd4f7e6 100644
--- a/include/linux/pagemap.h
+++ b/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,
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 39aa9d129612..e5fd5385f0cc 100644
--- a/mm/swapfile.c
+++ b/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);
                 }