recreate subvolume (not using btrfs send and receive)

recreate subvolume (not using btrfs send and receive)

[sri]

Hi,

I looking for a way to collect all metadata and data blocks associated 
with a subvolume or entire btrfs and recreate the same by dumping all 
blocks on newly allocated disks and bring the file system back assuming 
same number of disks are provided.

Example is say for ext3/ext4 using the information of used block bit map 
information in each block group, I can Identify all used blocks of the 
ext3/ext4 partition and simply copy all blocks.
Above will contains all metadata + data blocks (only used)
For a 10 Gb disk and say only 2 gb is used, using above, I can collect all 
2bg blocks.

Thank I can simply dump those blocks to a destination partition and 
recreate the partition. 

In the same way I am looking something similar for btrfs. 

Could anybody let me know is there a way to do this or something similar I 
can work it out.

Thanks you.