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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: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Hugh Dickins 2008-02-04 22:28:50 -08:00 committed by Linus Torvalds
parent f000944d03
commit 73b1262fa4
3 changed files with 17 additions and 49 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
include/linux/swap.h
View File

@ -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)

16
mm/shmem.c
View File

@ -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);

35
mm/swap_state.c
View File

@ -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.
*