[Qemu-devel] [PATCH 0/5 v2] qcow2 info: show highest-allocation and num-free-bytes

[Uri Lublin <uril@redhat.com>]

Hello,

The following 5 enhance "info blockstats" for qcow2 images (and
other formats that implement bdrv_get_info), to show 
higest-allocated-offset and number-of-free-bytes (below
the higest-allocated-offset) of the image.

One of the main usage for this information is to know and act
upon a case of end-of-storage-space. Instead of waiting for
-ENOSPACE (which now may cause the VM to stop), one can
define a threshold and extend the diskspace allocated for
the image.
This info is also good for management systems, so they
can report the user disk space status.

Also with highest_alloc and num_free_bytes, we can have a pretty 
good idea about how fragmented a qcow2 images is, and try to
defragment it later.

Patches 1,2,3, Provides information about the highest allocated byte (offset)
Patch 4, Provides information about the number of free bytes 
         below highest_alloc.
Patch 5, Provides info about highest_alloc and num_free_bytes through 
         qemu-img info


Changes from v1: better description of use cases.

Regards,
    Uri.