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swap: rework map_swap_page() again 

Seems that page_io.c doesn't really need to know that page_private(page)
is the swp_entry 'val'.  Rework map_swap_page() to do what its name says
and map a page to a page offset in the swap space.

The only other caller of map_swap_page() is internal to mm/swapfile.c and
it does want to map a swap entry to the 'sector'.  So rename
map_swap_page() to map_swap_entry(), make it 'static' and and implement
map_swap_page() as a wrapper around that.

Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Lee Schermerhorn 2009-12-14 17:58:49 -08:00 committed by Linus Torvalds
parent 7509765a29
commit d4906e1aa5
3 changed files with 18 additions and 8 deletions
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2
include/linux/swap.h
View File

@ -325,7 +325,7 @@ extern void swapcache_free(swp_entry_t, struct page *page);
extern int free_swap_and_cache(swp_entry_t);
extern int swap_type_of(dev_t, sector_t, struct block_device **);
extern unsigned int count_swap_pages(int, int);
extern sector_t map_swap_page(swp_entry_t, struct block_device **);
extern sector_t map_swap_page(struct page *, struct block_device **);
extern sector_t swapdev_block(int, pgoff_t);
extern int reuse_swap_page(struct page *);
extern int try_to_free_swap(struct page *);

4
mm/page_io.c
View File

@ -26,9 +26,7 @@ static struct bio *get_swap_bio(gfp_t gfp_flags,
bio = bio_alloc(gfp_flags, 1);
if (bio) {
swp_entry_t entry;
entry.val = page_private(page);
bio->bi_sector = map_swap_page(entry, &bio->bi_bdev);
bio->bi_sector = map_swap_page(page, &bio->bi_bdev);
bio->bi_sector <<= PAGE_SHIFT - 9;
bio->bi_io_vec[0].bv_page = page;
bio->bi_io_vec[0].bv_len = PAGE_SIZE;

20
mm/swapfile.c
View File

@ -38,6 +38,7 @@
static bool swap_count_continued(struct swap_info_struct *, pgoff_t,
unsigned char);
static void free_swap_count_continuations(struct swap_info_struct *);
static sector_t map_swap_entry(swp_entry_t, struct block_device**);
static DEFINE_SPINLOCK(swap_lock);
static unsigned int nr_swapfiles;
@ -782,7 +783,7 @@ sector_t swapdev_block(int type, pgoff_t offset)
return 0;
if (!(swap_info[type]->flags & SWP_WRITEOK))
return 0;
return map_swap_page(swp_entry(type, offset), &bdev);
return map_swap_entry(swp_entry(type, offset), &bdev);
}
/*
@ -1249,10 +1250,11 @@ static void drain_mmlist(void)
/*
* Use this swapdev's extent info to locate the (PAGE_SIZE) block which
* corresponds to page offset `offset'. Note that the type of this function
* is sector_t, but it returns page offset into the bdev, not sector offset.
* corresponds to page offset for the specified swap entry.
* Note that the type of this function is sector_t, but it returns page offset
* into the bdev, not sector offset.
*/
sector_t map_swap_page(swp_entry_t entry, struct block_device **bdev)
static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev)
{
struct swap_info_struct *sis;
struct swap_extent *start_se;
@ -1280,6 +1282,16 @@ sector_t map_swap_page(swp_entry_t entry, struct block_device **bdev)
}
}
/*
* Returns the page offset into bdev for the specified page's swap entry.
*/
sector_t map_swap_page(struct page *page, struct block_device **bdev)
{
swp_entry_t entry;
entry.val = page_private(page);
return map_swap_entry(entry, bdev);
}
/*
* Free all of a swapdev's extent information
*/