ext2_large_blocksize_support.patch

   1 Support large blocksize up to PAGESIZE (max 64KB) for ext2
   2
   3 From: Takashi Sato <sho@tnes.nec.co.jp>
   4
   5 This patch set supports large block size(>4k, <=64k) in ext2,
   6 just enlarging the block size limit. But it is NOT possible to have 64kB
   7 blocksize on ext2 without some changes to the directory handling
   8 code.  The reason is that an empty 64kB directory block would have a
   9 rec_len == (__u16)2^16 == 0, and this would cause an error to be hit in
  10 the filesystem.  The proposed solution is treat 64k rec_len
  11 with a an impossible value like rec_len = 0xffff to handle this.
  12
  13 The Patch-set consists of the following 2 patches.
  14   [1/2]  ext2: enlarge blocksize
  15          - Allow blocksize up to pagesize
  16
  17   [2/2]  ext2: fix rec_len overflow
  18          - prevent rec_len from overflow with 64KB blocksize
  19
  20 Now on 64k page ppc64 box runs with this patch set we could create a 64k
  21 block size ext2, and able to handle empty directory block.
  22
  23 Signed-off-by: Takashi Sato <sho@tnes.nec.co.jp>
  24 Signed-off-by: Mingming Cao <cmm@us.ibm.com>
  25 ---
  26
  27  fs/ext2/super.c         |    3 ++-
  28  include/linux/ext2_fs.h |    4 ++--
  29  2 files changed, 4 insertions(+), 3 deletions(-)
  30
  31
  32 Index: linux-2.6.23-rc9/fs/ext2/super.c
  33 ===================================================================
  34 --- linux-2.6.23-rc9.orig/fs/ext2/super.c       2007-10-05 10:12:36.000000000 -0700
  35 +++ linux-2.6.23-rc9/fs/ext2/super.c    2007-10-05 10:13:38.000000000 -0700
  36 @@ -775,7 +775,8 @@ static int ext2_fill_super(struct super_
  37                 brelse(bh);
  38
  39                 if (!sb_set_blocksize(sb, blocksize)) {
  40 -                       printk(KERN_ERR "EXT2-fs: blocksize too small for device.\n");
  41 +                       printk(KERN_ERR "EXT2-fs: bad blocksize %d.\n",
  42 +                               blocksize);
  43                         goto failed_sbi;
  44                 }
  45
  46 Index: linux-2.6.23-rc9/include/linux/ext2_fs.h
  47 ===================================================================
  48 --- linux-2.6.23-rc9.orig/include/linux/ext2_fs.h       2007-10-05 10:12:36.000000000 -0700
  49 +++ linux-2.6.23-rc9/include/linux/ext2_fs.h    2007-10-05 10:13:38.000000000 -0700
  50 @@ -86,8 +86,8 @@ static inline struct ext2_sb_info *EXT2_
  51   * Macro-instructions used to manage several block sizes
  52   */
  53  #define EXT2_MIN_BLOCK_SIZE            1024
  54 -#define        EXT2_MAX_BLOCK_SIZE             4096
  55 -#define EXT2_MIN_BLOCK_LOG_SIZE                  10
  56 +#define EXT2_MAX_BLOCK_SIZE            65536
  57 +#define EXT2_MIN_BLOCK_LOG_SIZE                10
  58  #ifdef __KERNEL__
  59  # define EXT2_BLOCK_SIZE(s)            ((s)->s_blocksize)
  60  #else