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Commit f45840b5 authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
Browse files

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: default avatarNick Piggin <npiggin@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9978ad58

include/linux/pagemap.h

+7 −7
Original line number Diff line number Diff line
@@ -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;

}

mm/swap_state.c

+2 −2
Original line number Diff line number Diff line
@@ -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);