mm: pagecache insertion fewer atomics

Setting and clearing the page locked when inserting it into swapcache /
pagecache when it has no other references can use non-atomic page flags
operations because no other CPU may be operating on it at this time.

This saves one atomic operation when inserting a page into pagecache.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 4b6c4d8..7334b2b 100644 (file)
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -299,14 +299,14 @@ extern int __lock_page_killable(struct page *page);
 extern void __lock_page_nosync(struct page *page);
 extern void unlock_page(struct page *page);
 
-static inline void set_page_locked(struct page *page)
+static inline void __set_page_locked(struct page *page)
 {
-       set_bit(PG_locked, &page->flags);
+       __set_bit(PG_locked, &page->flags);
 }
 
-static inline void clear_page_locked(struct page *page)
+static inline void __clear_page_locked(struct page *page)
 {
-       clear_bit(PG_locked, &page->flags);
+       __clear_bit(PG_locked, &page->flags);
 }
 
 static inline int trylock_page(struct page *page)
@@ -438,17 +438,17 @@ extern void __remove_from_page_cache(struct page *page);
 
 /*
  * Like add_to_page_cache_locked, but used to add newly allocated pages:
- * the page is new, so we can just run set_page_locked() against it.
+ * the page is new, so we can just run __set_page_locked() against it.
  */
 static inline int add_to_page_cache(struct page *page,
                struct address_space *mapping, pgoff_t offset, gfp_t gfp_mask)
 {
        int error;
 
-       set_page_locked(page);
+       __set_page_locked(page);
        error = add_to_page_cache_locked(page, mapping, offset, gfp_mask);
        if (unlikely(error))
-               clear_page_locked(page);
+               __clear_page_locked(page);
        return error;
 }
 

diff --git a/mm/swap_state.c b/mm/swap_state.c
index 43cda7b..3353c90 100644 (file)
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -303,7 +303,7 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
                 * re-using the just freed swap entry for an existing page.
                 * May fail (-ENOMEM) if radix-tree node allocation failed.
                 */
-               set_page_locked(new_page);
+               __set_page_locked(new_page);
                SetPageSwapBacked(new_page);
                err = add_to_swap_cache(new_page, entry, gfp_mask & GFP_KERNEL);
                if (likely(!err)) {
@@ -315,7 +315,7 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
                        return new_page;
                }
                ClearPageSwapBacked(new_page);
-               clear_page_locked(new_page);
+               __clear_page_locked(new_page);
                swap_free(entry);
        } while (err != -ENOMEM);