From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id 918326007E3 for ; Wed, 2 Dec 2009 15:10:41 -0500 (EST) Subject: [PATCH] swap: rework map_swap_page() again From: Lee Schermerhorn Content-Type: text/plain Date: Wed, 02 Dec 2009 15:10:31 -0500 Message-Id: <1259784631.4088.231.camel@useless.americas.hpqcorp.net> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Hugh Dickins Cc: linux-mm , Andrew Morton List-ID: Hugh: when your swap_info cleanup patches went by back in mid-Oct, I noticed your change to the map_swap_page() interface and this additional change occurred to me. Is this worth doing? [Maybe should do something about that magic '9' there in get_swap_bio() and all those "PAGE_SHIFT - 9" in swapfile.c as well?] Lee ------------------- Re: swap_info-private-to-swapfilec.patch in mmotm 091124 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 include/linux/swap.h | 2 +- mm/page_io.c | 4 +--- mm/swapfile.c | 20 ++++++++++++++++---- 3 files changed, 18 insertions(+), 8 deletions(-) Index: linux-2.6.32-rc8-mmotm-091124-1647/include/linux/swap.h =================================================================== --- linux-2.6.32-rc8-mmotm-091124-1647.orig/include/linux/swap.h 2009-12-02 14:05:25.000000000 -0500 +++ linux-2.6.32-rc8-mmotm-091124-1647/include/linux/swap.h 2009-12-02 14:05:26.000000000 -0500 @@ -325,7 +325,7 @@ extern void swapcache_free(swp_entry_t, 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 *); Index: linux-2.6.32-rc8-mmotm-091124-1647/mm/page_io.c =================================================================== --- linux-2.6.32-rc8-mmotm-091124-1647.orig/mm/page_io.c 2009-12-02 14:05:25.000000000 -0500 +++ linux-2.6.32-rc8-mmotm-091124-1647/mm/page_io.c 2009-12-02 14:05:26.000000000 -0500 @@ -26,9 +26,7 @@ static struct bio *get_swap_bio(gfp_t gf 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; Index: linux-2.6.32-rc8-mmotm-091124-1647/mm/swapfile.c =================================================================== --- linux-2.6.32-rc8-mmotm-091124-1647.orig/mm/swapfile.c 2009-12-02 14:05:25.000000000 -0500 +++ linux-2.6.32-rc8-mmotm-091124-1647/mm/swapfile.c 2009-12-02 14:51:44.000000000 -0500 @@ -39,6 +39,7 @@ 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; @@ -785,7 +786,7 @@ sector_t swapdev_block(int type, pgoff_t 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); } /* @@ -1258,10 +1259,11 @@ 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; @@ -1290,6 +1292,16 @@ sector_t map_swap_page(swp_entry_t entry } /* + * 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 */ static void destroy_swap_extents(struct swap_info_struct *sis) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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