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Commit 73b1262f authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

tmpfs: move swap swizzling into shmem 



move_to_swap_cache and move_from_swap_cache functions (which swizzle a page
between tmpfs page cache and swap cache, to avoid page copying) are only used
by shmem.c; and our subsequent fix for unionfs needs different treatments in
the two instances of move_from_swap_cache.  Move them from swap_state.c into
their callsites shmem_writepage, shmem_unuse_inode and shmem_getpage, making
add_to_swap_cache externally visible.

shmem.c likes to say set_page_dirty where swap_state.c liked to say
SetPageDirty: respect that diversity, which __set_page_dirty_no_writeback
makes moot (and implies we should lose that "shift page from clean_pages to
dirty_pages list" comment: it's on neither).

Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f000944d

include/linux/swap.h

+4 −11
Original line number Diff line number Diff line
@@ -220,11 +220,9 @@ extern struct address_space swapper_space; 
#define total_swapcache_pages  swapper_space.nrpages

extern void show_swap_cache_info(void);

extern int add_to_swap(struct page *, gfp_t);

extern int add_to_swap_cache(struct page *, swp_entry_t, gfp_t);

extern void __delete_from_swap_cache(struct page *);

extern void delete_from_swap_cache(struct page *);

extern int move_to_swap_cache(struct page *, swp_entry_t);

extern int move_from_swap_cache(struct page *, unsigned long,

		struct address_space *);

extern void free_page_and_swap_cache(struct page *);

extern void free_pages_and_swap_cache(struct page **, int);

extern struct page *lookup_swap_cache(swp_entry_t);
@@ -319,15 +317,10 @@ static inline struct page *lookup_swap_cache(swp_entry_t swp) 


#define can_share_swap_page(p)			(page_mapcount(p) == 1)



static inline int move_to_swap_cache(struct page *page, swp_entry_t entry)

static inline int add_to_swap_cache(struct page *page, swp_entry_t entry,

							gfp_t gfp_mask)

{

	return 1;

}



static inline int move_from_swap_cache(struct page *page, unsigned long index,

					struct address_space *mapping)

{

	return 1;

	return -1;

}



static inline void __delete_from_swap_cache(struct page *page)

mm/shmem.c

+12 −4
Original line number Diff line number Diff line
@@ -884,7 +884,9 @@ lost2: 
found:

	idx += offset;

	inode = &info->vfs_inode;

	if (move_from_swap_cache(page, idx, inode->i_mapping) == 0) {

	if (add_to_page_cache(page, inode->i_mapping, idx, GFP_ATOMIC) == 0) {

		delete_from_swap_cache(page);

		set_page_dirty(page);

		info->flags |= SHMEM_PAGEIN;

		shmem_swp_set(info, ptr + offset, 0);

	}
@@ -972,7 +974,8 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) 
	BUG_ON(!entry);

	BUG_ON(entry->val);



	if (move_to_swap_cache(page, swap) == 0) {

	if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {

		remove_from_page_cache(page);

		shmem_swp_set(info, entry, swap.val);

		shmem_swp_unmap(entry);

		spin_unlock(&info->lock);
@@ -982,6 +985,9 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) 
			list_move_tail(&info->swaplist, &shmem_swaplist);

			spin_unlock(&shmem_swaplist_lock);

		}

		swap_duplicate(swap);

		page_cache_release(page);	/* pagecache ref */

		set_page_dirty(page);

		unlock_page(page);

		return 0;

	}
@@ -1217,13 +1223,15 @@ repeat: 
			SetPageUptodate(filepage);

			set_page_dirty(filepage);

			swap_free(swap);

		} else if (!(error = move_from_swap_cache(

				swappage, idx, mapping))) {

		} else if (!(error = add_to_page_cache(

				swappage, mapping, idx, GFP_ATOMIC))) {

			info->flags |= SHMEM_PAGEIN;

			shmem_swp_set(info, entry, 0);

			shmem_swp_unmap(entry);

			delete_from_swap_cache(swappage);

			spin_unlock(&info->lock);

			filepage = swappage;

			set_page_dirty(filepage);

			swap_free(swap);

		} else {

			shmem_swp_unmap(entry);

mm/swap_state.c

+1 −34
Original line number Diff line number Diff line
@@ -67,8 +67,7 @@ void show_swap_cache_info(void) 
 * add_to_swap_cache resembles add_to_page_cache on swapper_space,

 * but sets SwapCache flag and private instead of mapping and index.

 */

static int add_to_swap_cache(struct page *page, swp_entry_t entry,

			       gfp_t gfp_mask)

int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)

{

	int error;
@@ -183,38 +182,6 @@ void delete_from_swap_cache(struct page *page) 
	page_cache_release(page);

}



/*

 * Strange swizzling function only for use by shmem_writepage

 */

int move_to_swap_cache(struct page *page, swp_entry_t entry)

{

	int err = add_to_swap_cache(page, entry, GFP_ATOMIC);

	if (!err) {

		remove_from_page_cache(page);

		page_cache_release(page);	/* pagecache ref */

		if (!swap_duplicate(entry))

			BUG();

		SetPageDirty(page);

	}

	return err;

}



/*

 * Strange swizzling function for shmem_getpage (and shmem_unuse)

 */

int move_from_swap_cache(struct page *page, unsigned long index,

		struct address_space *mapping)

{

	int err = add_to_page_cache(page, mapping, index, GFP_ATOMIC);

	if (!err) {

		delete_from_swap_cache(page);

		/* shift page from clean_pages to dirty_pages list */

		ClearPageDirty(page);

		set_page_dirty(page);

	}

	return err;

}



/* 

 * If we are the only user, then try to free up the swap cache. 

 *