help regarding ext4 extend and multiblock allocation

[Greg Freemyer]

On Wed, Dec 28, 2011 at 10:42 PM, Swapnil Gaikwad
<swapnilgaik72 at gmail.com> wrote:
> How the extend is different from block allocation?
> How it is implemented in ext4?
> How helpful the multiblock allocation in ext4?
> Is there is some special cases than ext3 that handled in ext4 for above.

Have you read the kernelnewbies page on ext4:

http://kernelnewbies.org/Ext4

After you read that, quote the paragraph you don't understand and ask again.