okajima-2-ext3-implement-releasepage

   1 ext3: provide function to release metadata pages under memory pressure
   2
   3 From: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
   4
   5 Pages in the page cache belonging to ext3 data files are released via
   6 the ext3_releasepage() function specified in the ext3 inode's
   7 address_space_ops.  However, metadata blocks (such as indirect blocks,
   8 directory blocks, etc) are managed via the block device
   9 address_space_ops, and they can not be released by
  10 try_to_free_buffers() if they have a journal head attached to them.
  11
  12 To address this, we supply a release_metadata function which is called
  13 by the block device's blkdev_releasepage() function, which calls
  14 journal_try_to_free_buffers() function to free the metadata.
  15
  16 Signed-off-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
  17 Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
  18 Cc: linux-fsdevel@vger.kernel.org
  19 ---
  20  fs/ext3/inode.c         |   16 ++++++++++++++++
  21  fs/ext3/super.c         |    2 ++
  22  include/linux/ext3_fs.h |    2 ++
  23  3 files changed, 20 insertions(+)
  24
  25 diff -Nurp linux-2.6.28-rc4.orig/fs/ext3/inode.c linux-2.6.28-rc4/fs/ext3/inode.c
  26 --- linux-2.6.28-rc4.orig/fs/ext3/inode.c       2008-11-10 09:36:15.000000000 +0900
  27 +++ linux-2.6.28-rc4/fs/ext3/inode.c    2008-11-11 09:31:13.000000000 +0900
  28 @@ -1680,6 +1680,28 @@ static int ext3_releasepage(struct page
  29  }
  30
  31  /*
  32 + * Try to release metadata pages (indirect blocks, directories) which are
  33 + * mapped via the block device.  Since these pages could have journal heads
  34 + * which would prevent try_to_free_buffers() from freeing them, we must use
  35 + * jbd layer's try_to_free_buffers() function to release them.
  36 + */
  37 +int ext3_release_metadata(void *client, struct page *page, gfp_t wait)
  38 +{
  39 +       struct super_block *sb = (struct super_block*)client;
  40 +       journal_t *journal;
  41 +
  42 +       WARN_ON(PageChecked(page));
  43 +       if (!page_has_buffers(page))
  44 +               return 0;
  45 +       BUG_ON(EXT3_SB(sb) == NULL);
  46 +       journal = EXT3_SB(sb)->s_journal;
  47 +       if (journal != NULL)
  48 +               return journal_try_to_free_buffers(journal, page, wait);
  49 +       else
  50 +               return try_to_free_buffers(page);
  51 +}
  52 +
  53 +/*
  54   * If the O_DIRECT write will extend the file then add this inode to the
  55   * orphan list.  So recovery will truncate it back to the original size
  56   * if the machine crashes during the write.
  57 diff -Nurp linux-2.6.28-rc4.orig/fs/ext3/super.c linux-2.6.28-rc4/fs/ext3/super.c
  58 --- linux-2.6.28-rc4.orig/fs/ext3/super.c       2008-11-10 09:36:15.000000000 +0900
  59 +++ linux-2.6.28-rc4/fs/ext3/super.c    2008-11-11 09:01:53.000000000 +0900
  60 @@ -2972,6 +2972,8 @@ static struct file_system_type ext3_fs_t
  61         .name           = "ext3",
  62         .get_sb         = ext3_get_sb,
  63         .kill_sb        = kill_block_super,
  64 +       .release_metadata
  65 +                       = ext3_release_metadata,
  66         .fs_flags       = FS_REQUIRES_DEV,
  67  };
  68
  69 diff -Nurp linux-2.6.28-rc4.orig/include/linux/ext3_fs.h linux-2.6.28-rc4/include/linux/ext3_fs.h
  70 --- linux-2.6.28-rc4.orig/include/linux/ext3_fs.h       2008-11-10 09:36:15.000000000 +0900
  71 +++ linux-2.6.28-rc4/include/linux/ext3_fs.h    2008-11-10 18:33:52.000000000 +0900
  72 @@ -841,6 +841,8 @@ extern void ext3_get_inode_flags(struct
  73  extern void ext3_set_aops(struct inode *inode);
  74  extern int ext3_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
  75                        u64 start, u64 len);
  76 +extern int ext3_release_metadata(void *client, struct page *page,
  77 +                       gfp_t wait);
  78
  79  /* ioctl.c */
  80  extern int ext3_ioctl (struct inode *, struct file *, unsigned int,
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