Commit f981c595 authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds

mm: methods for teaching filesystems about PG_swapcache pages

In order to teach filesystems to handle swap cache pages, three new page
functions are introduced:

  pgoff_t page_file_index(struct page *);
  loff_t page_file_offset(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_offset() - uses page_file_index(), so that it will give the
expected result, even 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.
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
Reviewed-by: default avatarRik van Riel <riel@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric B Munson <emunson@mgebm.net>
Cc: Eric Paris <eparis@redhat.com>
Cc: James Morris <jmorris@namei.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: Neil Brown <neilb@suse.de>
Cc: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Xiaotian Feng <dfeng@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6290c2c4
...@@ -805,6 +805,17 @@ static inline void *page_rmapping(struct page *page) ...@@ -805,6 +805,17 @@ static inline void *page_rmapping(struct page *page)
return (void *)((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS); return (void *)((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS);
} }
extern struct address_space *__page_file_mapping(struct page *);
static inline
struct address_space *page_file_mapping(struct page *page)
{
if (unlikely(PageSwapCache(page)))
return __page_file_mapping(page);
return page->mapping;
}
static inline int PageAnon(struct page *page) static inline int PageAnon(struct page *page)
{ {
return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0; return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
...@@ -821,6 +832,20 @@ static inline pgoff_t page_index(struct page *page) ...@@ -821,6 +832,20 @@ static inline pgoff_t page_index(struct page *page)
return page->index; return page->index;
} }
extern pgoff_t __page_file_index(struct page *page);
/*
* 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)))
return __page_file_index(page);
return page->index;
}
/* /*
* Return true if this page is mapped into pagetables. * Return true if this page is mapped into pagetables.
*/ */
......
...@@ -286,6 +286,11 @@ static inline loff_t page_offset(struct page *page) ...@@ -286,6 +286,11 @@ static inline loff_t page_offset(struct page *page)
return ((loff_t)page->index) << PAGE_CACHE_SHIFT; return ((loff_t)page->index) << PAGE_CACHE_SHIFT;
} }
static inline loff_t page_file_offset(struct page *page)
{
return ((loff_t)page_file_index(page)) << PAGE_CACHE_SHIFT;
}
extern pgoff_t linear_hugepage_index(struct vm_area_struct *vma, extern pgoff_t linear_hugepage_index(struct vm_area_struct *vma,
unsigned long address); unsigned long address);
......
...@@ -356,6 +356,7 @@ extern unsigned int count_swap_pages(int, int); ...@@ -356,6 +356,7 @@ extern unsigned int count_swap_pages(int, int);
extern sector_t map_swap_page(struct page *, struct block_device **); extern sector_t map_swap_page(struct page *, struct block_device **);
extern sector_t swapdev_block(int, pgoff_t); extern sector_t swapdev_block(int, pgoff_t);
extern int page_swapcount(struct page *); extern int page_swapcount(struct page *);
extern struct swap_info_struct *page_swap_info(struct page *);
extern int reuse_swap_page(struct page *); extern int reuse_swap_page(struct page *);
extern int try_to_free_swap(struct page *); extern int try_to_free_swap(struct page *);
struct backing_dev_info; struct backing_dev_info;
......
...@@ -33,6 +33,7 @@ ...@@ -33,6 +33,7 @@
#include <linux/oom.h> #include <linux/oom.h>
#include <linux/frontswap.h> #include <linux/frontswap.h>
#include <linux/swapfile.h> #include <linux/swapfile.h>
#include <linux/export.h>
#include <asm/pgtable.h> #include <asm/pgtable.h>
#include <asm/tlbflush.h> #include <asm/tlbflush.h>
...@@ -2285,6 +2286,31 @@ int swapcache_prepare(swp_entry_t entry) ...@@ -2285,6 +2286,31 @@ int swapcache_prepare(swp_entry_t entry)
return __swap_duplicate(entry, SWAP_HAS_CACHE); return __swap_duplicate(entry, SWAP_HAS_CACHE);
} }
struct swap_info_struct *page_swap_info(struct page *page)
{
swp_entry_t swap = { .val = page_private(page) };
BUG_ON(!PageSwapCache(page));
return swap_info[swp_type(swap)];
}
/*
* out-of-line __page_file_ methods to avoid include hell.
*/
struct address_space *__page_file_mapping(struct page *page)
{
VM_BUG_ON(!PageSwapCache(page));
return page_swap_info(page)->swap_file->f_mapping;
}
EXPORT_SYMBOL_GPL(__page_file_mapping);
pgoff_t __page_file_index(struct page *page)
{
swp_entry_t swap = { .val = page_private(page) };
VM_BUG_ON(!PageSwapCache(page));
return swp_offset(swap);
}
EXPORT_SYMBOL_GPL(__page_file_index);
/* /*
* add_swap_count_continuation - called when a swap count is duplicated * add_swap_count_continuation - called when a swap count is duplicated
* beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's
......
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