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

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

include/linux/mm.h

+25 −0
Original line number Diff line number Diff line
@@ -805,6 +805,17 @@ static inline void *page_rmapping(struct page *page) 
	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)

{

	return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
@@ -821,6 +832,20 @@ static inline pgoff_t page_index(struct page *page) 
	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.

 */

include/linux/pagemap.h

+5 −0
Original line number Diff line number Diff line
@@ -286,6 +286,11 @@ static inline loff_t page_offset(struct page *page) 
	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,

				     unsigned long address);

include/linux/swap.h

+1 −0
Original line number Diff line number Diff line
@@ -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 swapdev_block(int, pgoff_t);

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 try_to_free_swap(struct page *);

struct backing_dev_info;

mm/swapfile.c

+26 −0
Original line number Diff line number Diff line
@@ -33,6 +33,7 @@ 
#include <linux/oom.h>

#include <linux/frontswap.h>

#include <linux/swapfile.h>

#include <linux/export.h>



#include <asm/pgtable.h>

#include <asm/tlbflush.h>
@@ -2285,6 +2286,31 @@ int swapcache_prepare(swp_entry_t entry) 
	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

 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's