[Qemu-devel] [RFC] introduce a dynamic library to expose qemu block API

[Wenchao Xia <xiawenc@linux.vnet.ibm.com>]

Hi, Paolo and folks,
  qemu have good capabilities to access different virtual disks, I want
to expose its block layer API to let 3rd party program linked in, such
as management stack or block tools, to access images data directly.

Following is the objects:
  (1) API to write/read block device at offset.
  (2) Determine the image type,qcow2/qed/raw
  (3) Determine which blocks are allocated.
  (4) Determine backing file.

Following is my implementing plan draft:
  1 introduce libqblock.so in sub directory in qemu.
  2 write a nbd client in libqblock, similar to qemu nbd client. Then
use it to talk with nbd server, by default is qemu-nbd, to get access
to images. In this way, libqblock.so could be friendly LGPL licensed.
  3 still not got a good way to get additional info in (2)(3)(4),
currently in my head is patch qemu-nbd to add an additional nbd command,
"image-info", in which returns related info.

  What do you think about it?

-- 
Best Regards

Wenchao Xia
mail:xiawenc@linux.vnet.ibm.com
tel:86-010-82450803