Commit ef6a3c63 authored by Miklos Szeredi's avatar Miklos Szeredi Committed by Linus Torvalds
Browse files

mm: add replace_page_cache_page() function 



This function basically does:

     remove_from_page_cache(old);
     page_cache_release(old);
     add_to_page_cache_locked(new);

Except it does this atomically, so there's no possibility for the "add" to
fail because of a race.

If memory cgroups are enabled, then the memory cgroup charge is also moved
from the old page to the new.

This function is currently used by fuse to move pages into the page cache
on read, instead of copying the page contents.

[minchan.kim@gmail.com: add freepage() hook to replace_page_cache_page()]
Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
Acked-by: default avatarRik van Riel <riel@redhat.com>
Acked-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: default avatarMinchan Kim <minchan.kim@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 318b275f

fs/fuse/dev.c

+4 −6
Original line number Diff line number Diff line
@@ -737,14 +737,12 @@ static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep) 
	if (WARN_ON(PageMlocked(oldpage)))

		goto out_fallback_unlock;



	remove_from_page_cache(oldpage);

	page_cache_release(oldpage);



	err = add_to_page_cache_locked(newpage, mapping, index, GFP_KERNEL);

	err = replace_page_cache_page(oldpage, newpage, GFP_KERNEL);

	if (err) {

		printk(KERN_WARNING "fuse_try_move_page: failed to add page");

		goto out_fallback_unlock;

		unlock_page(newpage);

		return err;

	}



	page_cache_get(newpage);



	if (!(buf->flags & PIPE_BUF_FLAG_LRU))

include/linux/memcontrol.h

+2 −2
Original line number Diff line number Diff line
@@ -96,7 +96,7 @@ extern struct cgroup_subsys_state *mem_cgroup_css(struct mem_cgroup *mem); 


extern int

mem_cgroup_prepare_migration(struct page *page,

	struct page *newpage, struct mem_cgroup **ptr);

	struct page *newpage, struct mem_cgroup **ptr, gfp_t gfp_mask);

extern void mem_cgroup_end_migration(struct mem_cgroup *mem,

	struct page *oldpage, struct page *newpage, bool migration_ok);
@@ -249,7 +249,7 @@ static inline struct cgroup_subsys_state *mem_cgroup_css(struct mem_cgroup *mem) 


static inline int

mem_cgroup_prepare_migration(struct page *page, struct page *newpage,

	struct mem_cgroup **ptr)

	struct mem_cgroup **ptr, gfp_t gfp_mask)

{

	return 0;

}

include/linux/pagemap.h

+1 −0
Original line number Diff line number Diff line
@@ -457,6 +457,7 @@ int add_to_page_cache_lru(struct page *page, struct address_space *mapping, 
				pgoff_t index, gfp_t gfp_mask);

extern void remove_from_page_cache(struct page *page);

extern void __remove_from_page_cache(struct page *page);

int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask);



/*

 * Like add_to_page_cache_locked, but used to add newly allocated pages:

mm/filemap.c

+70 −0
Original line number Diff line number Diff line
@@ -386,6 +386,76 @@ int filemap_write_and_wait_range(struct address_space *mapping, 
}

EXPORT_SYMBOL(filemap_write_and_wait_range);



/**

 * replace_page_cache_page - replace a pagecache page with a new one

 * @old:	page to be replaced

 * @new:	page to replace with

 * @gfp_mask:	allocation mode

 *

 * This function replaces a page in the pagecache with a new one.  On

 * success it acquires the pagecache reference for the new page and

 * drops it for the old page.  Both the old and new pages must be

 * locked.  This function does not add the new page to the LRU, the

 * caller must do that.

 *

 * The remove + add is atomic.  The only way this function can fail is

 * memory allocation failure.

 */

int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)

{

	int error;

	struct mem_cgroup *memcg = NULL;



	VM_BUG_ON(!PageLocked(old));

	VM_BUG_ON(!PageLocked(new));

	VM_BUG_ON(new->mapping);



	/*

	 * This is not page migration, but prepare_migration and

	 * end_migration does enough work for charge replacement.

	 *

	 * In the longer term we probably want a specialized function

	 * for moving the charge from old to new in a more efficient

	 * manner.

	 */

	error = mem_cgroup_prepare_migration(old, new, &memcg, gfp_mask);

	if (error)

		return error;



	error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);

	if (!error) {

		struct address_space *mapping = old->mapping;

		void (*freepage)(struct page *);



		pgoff_t offset = old->index;

		freepage = mapping->a_ops->freepage;



		page_cache_get(new);

		new->mapping = mapping;

		new->index = offset;



		spin_lock_irq(&mapping->tree_lock);

		__remove_from_page_cache(old);

		error = radix_tree_insert(&mapping->page_tree, offset, new);

		BUG_ON(error);

		mapping->nrpages++;

		__inc_zone_page_state(new, NR_FILE_PAGES);

		if (PageSwapBacked(new))

			__inc_zone_page_state(new, NR_SHMEM);

		spin_unlock_irq(&mapping->tree_lock);

		radix_tree_preload_end();

		if (freepage)

			freepage(old);

		page_cache_release(old);

		mem_cgroup_end_migration(memcg, old, new, true);

	} else {

		mem_cgroup_end_migration(memcg, old, new, false);

	}



	return error;

}

EXPORT_SYMBOL_GPL(replace_page_cache_page);



/**

 * add_to_page_cache_locked - add a locked page to the pagecache

 * @page:	page to add

mm/memcontrol.c

+2 −2
Original line number Diff line number Diff line
@@ -2883,7 +2883,7 @@ static inline int mem_cgroup_move_swap_account(swp_entry_t entry, 
 * page belongs to.

 */

int mem_cgroup_prepare_migration(struct page *page,

	struct page *newpage, struct mem_cgroup **ptr)

	struct page *newpage, struct mem_cgroup **ptr, gfp_t gfp_mask)

{

	struct page_cgroup *pc;

	struct mem_cgroup *mem = NULL;
@@ -2940,7 +2940,7 @@ int mem_cgroup_prepare_migration(struct page *page, 
		return 0;



	*ptr = mem;

	ret = __mem_cgroup_try_charge(NULL, GFP_KERNEL, ptr, false, PAGE_SIZE);

	ret = __mem_cgroup_try_charge(NULL, gfp_mask, ptr, false, PAGE_SIZE);

	css_put(&mem->css);/* drop extra refcnt */

	if (ret || *ptr == NULL) {

		if (PageAnon(page)) {

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