[RFC 1/4] Large Blocksize support for Ext2/3/4

Mingming Cao
2007-08-30T00:47:38Z

The next 4 patches support large block size (up to PAGESIZE, max 64KB)
for ext2/3/4, originally from Takashi Sato.
http://marc.info/?l=linux-ext4&m=115768873518400&w=2

It's quite simple to support large block size in ext2/3/4, mostly just
enlarge the block size limit. But it is NOT possible to have 64kB
blocksize on ext2/3/4 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 to put 2 empty records in such
a directory, or to special-case an impossible value like rec_len =
0xffff to handle this.

The Patch-set consists of the following 4 patches.
[1/4] ext2/3/4: enlarge blocksize
- Allow blocksize up to pagesize

[2/4] ext2: fix rec_len overflow
- prevent rec_len from overflow with 64KB blocksize

[3/4] ext3: fix rec_len overflow
- prevent rec_len from overflow with 64KB blocksize

[4/4] ext4: fix rec_len overflow
- prevent rec_len from overflow with 64KB blocksize

Just rebase to 2.6.23-rc4 and against the ext4 patch queue. Compile tested only.

Next steps:
Need a e2fsprogs changes to able test this feature. As mkfs needs to be
educated not assuming rec_len to be blocksize all the time.
Will try it with Christoph Lameter's large block patch next.

Signed-off-by: Takashi Sato <sho@tnes.nec.co.jp>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
---
---
fs/ext2/super.c | 2 +-
fs/ext3/super.c | 5 ++++-
fs/ext4/super.c | 5 +++++
include/linux/ext2_fs.h | 4 ++--
include/linux/ext3_fs.h | 4 ++--
include/linux/ext4_fs.h | 4 ++--
6 files changed, 16 insertions(+), 8 deletions(-)

Index: linux-2.6.23-rc3/fs/ext2/super.c
===================================================================
--- linux-2.6.23-rc3.orig/fs/ext2/super.c 2007-08-12 21:25:24.000000000 -0700
+++ linux-2.6.23-rc3/fs/ext2/super.c 2007-08-29 15:22:29.000000000 -0700
@@ -775,7 +775,7 @@ static int ext2_fill_super(struct super_
brelse(bh);

if (!sb_set_blocksize(sb, blocksize)) {
- printk(KERN_ERR "EXT2-fs: blocksize too small for device.\n");
+ printk(KERN_ERR "EXT2-fs: bad blocksize %d.\n", blocksize);
goto failed_sbi;
}

Index: linux-2.6.23-rc3/fs/ext3/super.c
===================================================================
--- linux-2.6.23-rc3.orig/fs/ext3/super.c 2007-08-12 21:25:24.000000000 -0700
+++ linux-2.6.23-rc3/fs/ext3/super.c 2007-08-29 15:22:29.000000000 -0700
@@ -1549,7 +1549,10 @@ static int ext3_fill_super (struct super
}

brelse (bh);
- sb_set_blocksize(sb, blocksize);
+ if (!sb_set_blocksize(sb, blocksize)) {
+ printk(KERN_ERR "EXT3-fs: bad blocksize %d.\n", blocksize);
+ goto out_fail;
+ }
logic_sb_block = (sb_block * EXT3_MIN_BLOCK_SIZE) / blocksize;
offset = (sb_block * EXT3_MIN_BLOCK_SIZE) % blocksize;
bh = sb_bread(sb, logic_sb_block);
Index: linux-2.6.23-rc3/fs/ext4/super.c
===================================================================
--- linux-2.6.23-rc3.orig/fs/ext4/super.c 2007-08-28 11:09:40.000000000 -0700
+++ linux-2.6.23-rc3/fs/ext4/super.c 2007-08-29 15:24:08.000000000 -0700
@@ -1626,6 +1626,11 @@ static int ext4_fill_super (struct super
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.
Index: linux-2.6.23-rc3/include/linux/ext2_fs.h
===================================================================
--- linux-2.6.23-rc3.orig/include/linux/ext2_fs.h 2007-08-12 21:25:24.000000000 -0700
+++ linux-2.6.23-rc3/include/linux/ext2_fs.h 2007-08-29 15:22:29.000000000 -0700
@@ -86,8 +86,8 @@ static inline struct ext2_sb_info *EXT2_
* Macro-instructions used to manage several block sizes
*/
#define EXT2_MIN_BLOCK_SIZE 1024
-#define EXT2_MAX_BLOCK_SIZE 4096
-#define EXT2_MIN_BLOCK_LOG_SIZE 10
+#define EXT2_MAX_BLOCK_SIZE 65536
+#define EXT2_MIN_BLOCK_LOG_SIZE 10
#ifdef __KERNEL__
# define EXT2_BLOCK_SIZE(s) ((s)->s_blocksize)
#else
Index: linux-2.6.23-rc3/include/linux/ext3_fs.h
===================================================================
--- linux-2.6.23-rc3.orig/include/linux/ext3_fs.h 2007-08-12 21:25:24.000000000 -0700
+++ linux-2.6.23-rc3/include/linux/ext3_fs.h 2007-08-29 15:22:29.000000000 -0700
@@ -76,8 +76,8 @@
* Macro-instructions used to manage several block sizes
*/
#define EXT3_MIN_BLOCK_SIZE 1024
-#define EXT3_MAX_BLOCK_SIZE 4096
-#define EXT3_MIN_BLOCK_LOG_SIZE 10
+#define EXT3_MAX_BLOCK_SIZE 65536
+#define EXT3_MIN_BLOCK_LOG_SIZE 10
#ifdef __KERNEL__
# define EXT3_BLOCK_SIZE(s) ((s)->s_blocksize)
#else
Index: linux-2.6.23-rc3/include/linux/ext4_fs.h
===================================================================
--- linux-2.6.23-rc3.orig/include/linux/ext4_fs.h 2007-08-28 11:09:40.000000000 -0700
+++ linux-2.6.23-rc3/include/linux/ext4_fs.h 2007-08-29 15:22:29.000000000 -0700
@@ -104,8 +104,8 @@ struct ext4_allocation_request {
* 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