[Qemu-block] [PATCH 0/2] Add reduce image for qcow2

[Pavel Butsykin]

This patch adds the reduction of the image file for qcow2. As a result, this
allows us to reduce the virtual image size and free up space on the disk without
copying the image. Image can be fragmented and reduction is done by punching
holes in the image file.

# ./qemu-img create -f qcow2 -o size=4G image.qcow2
Formatting 'image.qcow2', fmt=qcow2 size=4294967296 encryption=off 
cluster_size=65536 lazy_refcounts=off refcount_bits=16

# ./qemu-io -c "write -P 0x22 0 1G" image.qcow2
wrote 1073741824/1073741824 bytes at offset 0
1 GiB, 1 ops; 0:00:02.59 (395.180 MiB/sec and 0.3859 ops/sec)

# ./qemu-img resize image.qcow2 128M
Image resized.

# qemu-img info image.qcow2 
image: image.qcow2
file format: qcow2
virtual size: 128M (134217728 bytes)
disk size: 128M
cluster_size: 65536
Format specific information:
    compat: 1.1
    lazy refcounts: false
    refcount bits: 16
    corrupt: false

# du -h image.qcow2 
129M    image.qcow2

Pavel Butsykin (2):
  qcow2: add reduce image support
  qemu-iotests: add reducing image test in 025

 block/qcow2-cache.c        |  8 +++++
 block/qcow2-cluster.c      | 83 ++++++++++++++++++++++++++++++++++++++++++++++
 block/qcow2-refcount.c     | 65 ++++++++++++++++++++++++++++++++++++
 block/qcow2.c              | 40 ++++++++++++++++------
 block/qcow2.h              |  4 +++
 qapi/block-core.json       |  4 ++-
 tests/qemu-iotests/025     | 19 +++++++++--
 tests/qemu-iotests/025.out | 12 ++++++-
 8 files changed, 221 insertions(+), 14 deletions(-)

-- 
2.11.0