[Updated PATCH] ext4: Use the correct block number when reading the super block.

[Updated PATCH] ext4: Use the correct block number when reading the super block.

[Aneesh Kumar K.V]

If the block device hard sector size is larger than EXT4_MIN_BLOCK_SIZE we
end up with wrong block number when reading super block.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 fs/ext4/super.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 1ca0f54..3095370 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1629,8 +1629,8 @@ static int ext4_fill_super (struct super_block *sb, void *data, int silent)
 	 * block sizes.  We need to calculate the offset from buffer start.
 	 */
 	if (blocksize != EXT4_MIN_BLOCK_SIZE) {
-		logical_sb_block = sb_block * EXT4_MIN_BLOCK_SIZE;
-		offset = do_div(logical_sb_block, blocksize);
+		logical_sb_block = (sb_block * EXT4_MIN_BLOCK_SIZE) / blocksize;
+		offset = do_div((sb_block * EXT4_MIN_BLOCK_SIZE), blocksize);
 	} else {
 		logical_sb_block = sb_block;
 	}
@@ -1747,8 +1747,8 @@ static int ext4_fill_super (struct super_block *sb, void *data, int silent)
 
 		brelse (bh);
 		sb_set_blocksize(sb, blocksize);
-		logical_sb_block = sb_block * EXT4_MIN_BLOCK_SIZE;
-		offset = do_div(logical_sb_block, blocksize);
+		logical_sb_block = (sb_block * EXT4_MIN_BLOCK_SIZE) / blocksize;
+		offset = do_div((sb_block * EXT4_MIN_BLOCK_SIZE), blocksize);
 		bh = sb_bread(sb, logical_sb_block);
 		if (!bh) {
 			printk(KERN_ERR
-- 
1.5.4.rc2-dirty

Re: [Updated PATCH] ext4: Use the correct block number when reading the super block.

[Aneesh Kumar K.V]

On Mon, Dec 31, 2007 at 01:59:22PM +0530, Aneesh Kumar K.V wrote:
> If the block device hard sector size is larger than EXT4_MIN_BLOCK_SIZE we
> end up with wrong block number when reading super block.
> 

Ignore the patch. I got confused by the do_div syntax. The do_div already save
the division result in logical_sb_block;

-aneesh