ext4_large_blocksize_support.patch

   1 ext4:  Support large blocksize up to PAGESIZE
   2
   3 From: Takashi Sato <sho@tnes.nec.co.jp>
   4
   5 This patch set supports large block size(>4k, <=64k) in ext4,
   6 just enlarging the block size limit. But it is NOT possible to have 64kB
   7 blocksize on ext4 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]  ext4: enlarge blocksize
  15          - Allow blocksize up to pagesize
  16
  17   [2/2]  ext4: 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 ext4dev, 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/ext4/super.c         |    5 +++++
  28  include/linux/ext4_fs.h |    4 ++--
  29  2 files changed, 7 insertions(+), 2 deletions(-)
  30
  31
  32 diff --git a/fs/ext4/super.c b/fs/ext4/super.c
  33 index 1ca0f54..ab7010d 100644
  34 --- a/fs/ext4/super.c
  35 +++ b/fs/ext4/super.c
  36 @@ -1624,6 +1624,11 @@ static int ext4_fill_super (struct super_block *sb, void *data, int silent)
  37                 goto out_fail;
  38         }
  39
  40 +       if (!sb_set_blocksize(sb, blocksize)) {
  41 +               printk(KERN_ERR "EXT4-fs: bad blocksize %d.\n", blocksize);
  42 +               goto out_fail;
  43 +       }
  44 +
  45         /*
  46          * The ext4 superblock will not be buffer aligned for other than 1kB
  47          * block sizes.  We need to calculate the offset from buffer start.
  48 diff --git a/include/linux/ext4_fs.h b/include/linux/ext4_fs.h
  49 index 97dd409..dfe4487 100644
  50 --- a/include/linux/ext4_fs.h
  51 +++ b/include/linux/ext4_fs.h
  52 @@ -73,8 +73,8 @@
  53   * Macro-instructions used to manage several block sizes
  54   */
  55  #define EXT4_MIN_BLOCK_SIZE            1024
  56 -#define        EXT4_MAX_BLOCK_SIZE             4096
  57 -#define EXT4_MIN_BLOCK_LOG_SIZE                  10
  58 +#define        EXT4_MAX_BLOCK_SIZE             65536
  59 +#define EXT4_MIN_BLOCK_LOG_SIZE                10
  60  #ifdef __KERNEL__
  61  # define EXT4_BLOCK_SIZE(s)            ((s)->s_blocksize)
  62  #else