src/patches/suse-2.6.27.25/patches.suse/SoN-27-mm-page_file_methods.patch

   1 From: Peter Zijlstra <a.p.zijlstra@chello.nl>
   2 Subject: mm: methods for teaching filesystems about PG_swapcache pages
   3 Patch-mainline: No
   4 References: FATE#303834
   5
   6 In order to teach filesystems to handle swap cache pages, three new page
   7 functions are introduced:
   8
   9   pgoff_t page_file_index(struct page *);
  10   loff_t page_file_offset(struct page *);
  11   struct address_space *page_file_mapping(struct page *);
  12
  13 page_file_index() - gives the offset of this page in the file in
  14 PAGE_CACHE_SIZE blocks. Like page->index is for mapped pages, this function
  15 also gives the correct index for PG_swapcache pages.
  16
  17 page_file_offset() - uses page_file_index(), so that it will give the expected
  18 result, even for PG_swapcache pages.
  19
  20 page_file_mapping() - gives the mapping backing the actual page; that is for
  21 swap cache pages it will give swap_file->f_mapping.
  22
  23 Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
  24 Acked-by: Neil Brown <neilb@suse.de>
  25 Acked-by: Suresh Jayaraman <sjayaraman@suse.de>
  26
  27 ---
  28  include/linux/mm.h      |   25 +++++++++++++++++++++++++
  29  include/linux/pagemap.h |    5 +++++
  30  mm/swapfile.c           |   19 +++++++++++++++++++
  31  3 files changed, 49 insertions(+)
  32
  33 --- a/include/linux/mm.h
  34 +++ b/include/linux/mm.h
  35 @@ -646,6 +646,17 @@ static inline struct address_space *page
  36         return mapping;
  37  }
  38
  39 +extern struct address_space *__page_file_mapping(struct page *);
  40 +
  41 +static inline
  42 +struct address_space *page_file_mapping(struct page *page)
  43 +{
  44 +       if (unlikely(PageSwapCache(page)))
  45 +               return __page_file_mapping(page);
  46 +
  47 +       return page->mapping;
  48 +}
  49 +
  50  static inline int PageAnon(struct page *page)
  51  {
  52         return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
  53 @@ -662,6 +673,20 @@ static inline pgoff_t page_index(struct
  54         return page->index;
  55  }
  56
  57 +extern pgoff_t __page_file_index(struct page *page);
  58 +
  59 +/*
  60 + * Return the file index of the page. Regular pagecache pages use ->index
  61 + * whereas swapcache pages use swp_offset(->private)
  62 + */
  63 +static inline pgoff_t page_file_index(struct page *page)
  64 +{
  65 +       if (unlikely(PageSwapCache(page)))
  66 +               return __page_file_index(page);
  67 +
  68 +       return page->index;
  69 +}
  70 +
  71  /*
  72   * The atomic page->_mapcount, like _count, starts from -1:
  73   * so that transitions both from it and to it can be tracked,
  74 --- a/include/linux/pagemap.h
  75 +++ b/include/linux/pagemap.h
  76 @@ -259,6 +259,11 @@ static inline loff_t page_offset(struct
  77         return ((loff_t)page->index) << PAGE_CACHE_SHIFT;
  78  }
  79
  80 +static inline loff_t page_file_offset(struct page *page)
  81 +{
  82 +       return ((loff_t)page_file_index(page)) << PAGE_CACHE_SHIFT;
  83 +}
  84 +
  85  static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
  86                                         unsigned long address)
  87  {
  88 --- a/mm/swapfile.c
  89 +++ b/mm/swapfile.c
  90 @@ -1856,6 +1856,25 @@ struct swap_info_struct *page_swap_info(
  91  }
  92
  93  /*
  94 + * out-of-line __page_file_ methods to avoid include hell.
  95 + */
  96 +
  97 +struct address_space *__page_file_mapping(struct page *page)
  98 +{
  99 +       VM_BUG_ON(!PageSwapCache(page));
 100 +       return page_swap_info(page)->swap_file->f_mapping;
 101 +}
 102 +EXPORT_SYMBOL_GPL(__page_file_mapping);
 103 +
 104 +pgoff_t __page_file_index(struct page *page)
 105 +{
 106 +       swp_entry_t swap = { .val = page_private(page) };
 107 +       VM_BUG_ON(!PageSwapCache(page));
 108 +       return swp_offset(swap);
 109 +}
 110 +EXPORT_SYMBOL_GPL(__page_file_index);
 111 +
 112 +/*
 113   * swap_lock prevents swap_map being freed. Don't grab an extra
 114   * reference on the swaphandle, it doesn't matter if it becomes unused.
 115   */