[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>

diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index 495858b..a92b10b 100644 (file)
--- 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 839f0b3..9539efd 100644 (file)
--- 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 39aa9d1..e5fd538 100644 (file)
--- 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);
                }