Re: [Qemu-devel] [PATCH v3 0/2] qcow2: Patch for shrinking qcow2 disk image

[Jun Li <junmuzi@gmail.com>]

Please ignore this patch, I have submit a new version.

On Mon, 10/13 13:04, Jun Li wrote:
> This is the third version for qcow2 shrinking. In this version, fixed host
> cluster leak when shrinking a disk image. Such as:
> Step 1,
> # /opt/qemu-git-arm/bin/qemu-img info /home/lijun/Work/tmp/shrink.qcow2
> image: /home/lijun/Work/tmp/shrink.qcow2
> file format: qcow2
> virtual size: 2.0G (2147483648 bytes)
> disk size: 2.0G
> cluster_size: 65536
> Format specific information:
>     compat: 1.1
>     lazy refcounts: false
>     corrupt: false
> 
> Step 2,
> # /opt/qemu-git-arm/bin/qemu-img resize /home/lijun/Work/tmp/shrink.qcow2 -100M
> Image resized.
> 
> Step 3,
> # /opt/qemu-git-arm/bin/qemu-img info /home/lijun/Work/tmp/shrink.qcow2
> image: /home/lijun/Work/tmp/shrink.qcow2
> file format: qcow2
> virtual size: 1.9G (2042626048 bytes)
> disk size: 1.9G
> cluster_size: 65536
> Format specific information:
>     compat: 1.1
>     lazy refcounts: false
>     corrupt: false
> 
> Step 4,
> # /opt/qemu-git-arm/bin/qemu-img check /home/lijun/Work/tmp/shrink.qcow2
> No errors were found on the image.
> 31005/31168 = 99.48% allocated, 0.79% fragmented, 0.00% compressed clusters
> Image end offset: 2033844224
> 
> As above show, in step 1, "disk size" and "virtual size" are all 2.0G.
> After Step 3, "disk size" and "virtual size" are all 1.9G.
> 
> BTW, above is also a simple testing. I will submit a test case for
> qemu-iotests later. But I am not so familar with howto write qemu-iotests now.
> 
> In file block/qcow2.c, just using ftruncate to fix host cluster leak.
> 
> In file block/qcow2-cluster.c, just re-copy qcow2_grow_l1_table to
> realize qcow2_shrink_l1_and_l2_table.
> 
> In file block/qcow2-refcount.c, also update the realization to handle self-describing
> refcount blocks in function update_refcount.
> 
> Thanks.
> 
> 
> Jun Li (2):
>   qcow2: Add qcow2_shrink_l1_and_l2_table for qcow2 shrinking
>   qcow2: add update refcount table realization for update_refcount
> 
>  block/qcow2-cluster.c  | 173 +++++++++++++++++++++++++++++++++++++++++++++++++
>  block/qcow2-refcount.c |  44 +++++++++++++
>  block/qcow2.c          |  40 ++++++++++--
>  block/qcow2.h          |   2 +
>  4 files changed, 255 insertions(+), 4 deletions(-)
> 
> -- 
> 1.9.3
>