In order to teach filesystems to handle swap cache pages, two new page functions are introduced: pgoff_t page_file_index(struct page *); struct address_space *page_file_mapping(struct page *); page_file_index - gives the offset of this page in the file in PAGE_CACHE_SIZE blocks. Like page->index is for mapped pages, this function also gives the correct index for PG_swapcache pages. page_file_mapping - gives the mapping backing the actual page; that is for swap cache pages it will give swap_file->f_mapping. page_offset() is modified to use page_file_index(), so that it will give the expected result, even for PG_swapcache pages. Signed-off-by: Peter Zijlstra CC: Trond Myklebust --- include/linux/mm.h | 30 ++++++++++++++++++++++++++++++ include/linux/pagemap.h | 2 +- include/linux/swap.h | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/swapops.h | 44 -------------------------------------------- 4 files changed, 79 insertions(+), 45 deletions(-) Index: linux-2.6/include/linux/mm.h =================================================================== --- linux-2.6.orig/include/linux/mm.h +++ linux-2.6/include/linux/mm.h @@ -15,6 +15,7 @@ #include #include #include +#include struct mempolicy; struct anon_vma; @@ -579,6 +580,22 @@ static inline struct address_space *page return mapping; } +static inline +struct swap_info_struct * page_swap_info(struct page *page) +{ + swp_entry_t swap = { .val = page_private(page) }; + BUG_ON(!PageSwapCache(page)); + return get_swap_info_struct(swp_type(swap)); +} + +static inline +struct address_space *page_file_mapping(struct page *page) +{ + if (unlikely(PageSwapCache(page))) + return page_swap_info(page)->swap_file->f_mapping; + return page->mapping; +} + static inline int PageAnon(struct page *page) { return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0; @@ -596,6 +613,19 @@ static inline pgoff_t page_index(struct } /* + * Return the file index of the page. Regular pagecache pages use ->index + * whereas swapcache pages use swp_offset(->private) + */ +static inline pgoff_t page_file_index(struct page *page) +{ + if (unlikely(PageSwapCache(page))) { + swp_entry_t swap = { .val = page_private(page) }; + return swp_offset(swap); + } + return page->index; +} + +/* * The atomic page->_mapcount, like _count, starts from -1: * so that transitions both from it and to it can be tracked, * using atomic_inc_and_test and atomic_add_negative(-1). Index: linux-2.6/include/linux/pagemap.h =================================================================== --- linux-2.6.orig/include/linux/pagemap.h +++ linux-2.6/include/linux/pagemap.h @@ -118,7 +118,7 @@ extern void __remove_from_page_cache(str */ static inline loff_t page_offset(struct page *page) { - return ((loff_t)page->index) << PAGE_CACHE_SHIFT; + return ((loff_t)page_file_index(page)) << PAGE_CACHE_SHIFT; } static inline pgoff_t linear_page_index(struct vm_area_struct *vma, Index: linux-2.6/include/linux/swap.h =================================================================== --- linux-2.6.orig/include/linux/swap.h +++ linux-2.6/include/linux/swap.h @@ -75,6 +75,50 @@ typedef struct { } swp_entry_t; /* + * swapcache pages are stored in the swapper_space radix tree. We want to + * get good packing density in that tree, so the index should be dense in + * the low-order bits. + * + * We arrange the `type' and `offset' fields so that `type' is at the five + * high-order bits of the swp_entry_t and `offset' is right-aligned in the + * remaining bits. + * + * swp_entry_t's are *never* stored anywhere in their arch-dependent format. + */ +#define SWP_TYPE_SHIFT(e) (sizeof(e.val) * 8 - MAX_SWAPFILES_SHIFT) +#define SWP_OFFSET_MASK(e) ((1UL << SWP_TYPE_SHIFT(e)) - 1) + +/* + * Store a type+offset into a swp_entry_t in an arch-independent format + */ +static inline swp_entry_t swp_entry(unsigned long type, pgoff_t offset) +{ + swp_entry_t ret; + + ret.val = (type << SWP_TYPE_SHIFT(ret)) | + (offset & SWP_OFFSET_MASK(ret)); + return ret; +} + +/* + * Extract the `type' field from a swp_entry_t. The swp_entry_t is in + * arch-independent format + */ +static inline unsigned swp_type(swp_entry_t entry) +{ + return (entry.val >> SWP_TYPE_SHIFT(entry)); +} + +/* + * Extract the `offset' field from a swp_entry_t. The swp_entry_t is in + * arch-independent format + */ +static inline pgoff_t swp_offset(swp_entry_t entry) +{ + return entry.val & SWP_OFFSET_MASK(entry); +} + +/* * current->reclaim_state points to one of these when a task is running * memory reclaim */ @@ -322,6 +366,10 @@ static inline int valid_swaphandles(swp_ return 0; } +static inline struct swap_info_struct *get_swap_info_struct(unsigned type) +{ + return NULL; +} #define can_share_swap_page(p) (page_mapcount(p) == 1) static inline int move_to_swap_cache(struct page *page, swp_entry_t entry) Index: linux-2.6/include/linux/swapops.h =================================================================== --- linux-2.6.orig/include/linux/swapops.h +++ linux-2.6/include/linux/swapops.h @@ -1,48 +1,4 @@ /* - * swapcache pages are stored in the swapper_space radix tree. We want to - * get good packing density in that tree, so the index should be dense in - * the low-order bits. - * - * We arrange the `type' and `offset' fields so that `type' is at the five - * high-order bits of the swp_entry_t and `offset' is right-aligned in the - * remaining bits. - * - * swp_entry_t's are *never* stored anywhere in their arch-dependent format. - */ -#define SWP_TYPE_SHIFT(e) (sizeof(e.val) * 8 - MAX_SWAPFILES_SHIFT) -#define SWP_OFFSET_MASK(e) ((1UL << SWP_TYPE_SHIFT(e)) - 1) - -/* - * Store a type+offset into a swp_entry_t in an arch-independent format - */ -static inline swp_entry_t swp_entry(unsigned long type, pgoff_t offset) -{ - swp_entry_t ret; - - ret.val = (type << SWP_TYPE_SHIFT(ret)) | - (offset & SWP_OFFSET_MASK(ret)); - return ret; -} - -/* - * Extract the `type' field from a swp_entry_t. The swp_entry_t is in - * arch-independent format - */ -static inline unsigned swp_type(swp_entry_t entry) -{ - return (entry.val >> SWP_TYPE_SHIFT(entry)); -} - -/* - * Extract the `offset' field from a swp_entry_t. The swp_entry_t is in - * arch-independent format - */ -static inline pgoff_t swp_offset(swp_entry_t entry) -{ - return entry.val & SWP_OFFSET_MASK(entry); -} - -/* * Convert the arch-dependent pte representation of a swp_entry_t into an * arch-independent swp_entry_t. */ -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/