[PATCH 23/29] mm: methods for teaching filesystems about PG_swapcache pages
From: Peter Zijlstra <hidden>
Date: 2007-02-21 15:34:49
Also in:
lkml, netdev
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 <redacted> CC: Trond Myklebust <redacted> --- include/linux/mm.h | 25 +++++++++++++++++++++++++ include/linux/pagemap.h | 2 +- 2 files changed, 26 insertions(+), 1 deletion(-) Index: linux-2.6-git/include/linux/mm.h ===================================================================
--- linux-2.6-git.orig/include/linux/mm.h 2007-02-21 12:15:01.000000000 +0100
+++ linux-2.6-git/include/linux/mm.h 2007-02-21 12:15:07.000000000 +0100@@ -594,6 +594,16 @@ static inline struct swap_info_struct *p return get_swap_info_struct(swp_type(swap)); } +static inline +struct address_space *page_file_mapping(struct page *page) +{ +#ifdef CONFIG_SWAP_FILE + if (unlikely(PageSwapCache(page))) + return page_swap_info(page)->swap_file->f_mapping; +#endif + return page->mapping; +} + static inline int PageAnon(struct page *page) { return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
@@ -611,6 +621,21 @@ 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) +{ +#ifdef CONFIG_SWAP_FILE + if (unlikely(PageSwapCache(page))) { + swp_entry_t swap = { .val = page_private(page) }; + return swp_offset(swap); + } +#endif + 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-git/include/linux/pagemap.h ===================================================================
--- linux-2.6-git.orig/include/linux/pagemap.h 2007-02-21 12:14:54.000000000 +0100
+++ linux-2.6-git/include/linux/pagemap.h 2007-02-21 12:15:07.000000000 +0100@@ -120,7 +120,7 @@ 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,
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