ext4: Support large blocksize up to PAGESIZE

This patch set supports large block size(>4k, <=64k) in ext4,
just enlarging the block size limit. But it is NOT possible to have 64kB
blocksize on ext4 without some changes to the directory handling
code.  The reason is that an empty 64kB directory block would have a
rec_len == (__u16)2^16 == 0, and this would cause an error to be hit in
the filesystem.  The proposed solution is treat 64k rec_len
with a an impossible value like rec_len = 0xffff to handle this.

The Patch-set consists of the following 2 patches.
  [1/2]  ext4: enlarge blocksize
         - Allow blocksize up to pagesize

  [2/2]  ext4: fix rec_len overflow
         - prevent rec_len from overflow with 64KB blocksize

Now on 64k page ppc64 box runs with this patch set we could create a 64k
block size ext4dev, and able to handle empty directory block.

Signed-off-by: Takashi Sato <sho@tnes.nec.co.jp>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 1ca0f546c466193e46c519879e8329a18c1b1af1..ab7010dde1b59574da2eccbc534d43fc421e6185 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1624,6 +1624,11 @@ static int ext4_fill_super (struct super_block *sb, void *data, int silent)
                goto out_fail;
        }
 
+       if (!sb_set_blocksize(sb, blocksize)) {
+               printk(KERN_ERR "EXT4-fs: bad blocksize %d.\n", blocksize);
+               goto out_fail;
+       }
+
        /*
         * The ext4 superblock will not be buffer aligned for other than 1kB
         * block sizes.  We need to calculate the offset from buffer start.

diff --git a/include/linux/ext4_fs.h b/include/linux/ext4_fs.h
index 97dd409d5f4a1194fa6034242793d03290968f59..dfe4487fc739ed9e7374d620a4763445696b7ff9 100644 (file)
--- a/include/linux/ext4_fs.h
+++ b/include/linux/ext4_fs.h
@@ -73,8 +73,8 @@
  * Macro-instructions used to manage several block sizes
  */
 #define EXT4_MIN_BLOCK_SIZE            1024
-#define        EXT4_MAX_BLOCK_SIZE             4096
-#define EXT4_MIN_BLOCK_LOG_SIZE                  10
+#define        EXT4_MAX_BLOCK_SIZE             65536
+#define EXT4_MIN_BLOCK_LOG_SIZE                10
 #ifdef __KERNEL__
 # define EXT4_BLOCK_SIZE(s)            ((s)->s_blocksize)
 #else