Re: [Qemu-devel] [PATCH v4 0/2] Truncate the tail of the image file in qcow2 shrinking

[Max Reitz]

On 2017-09-29 14:16, Pavel Butsykin wrote:
> Now after shrinking the qcow2 image, at the end of the image file, there might
> be a tail that probably will never be used. Although it will not bring any
> tangible benefit, we can cut the tail if it is. Yes, it will not free up disk
> space, but if the blocks were be allocated sequentially and the image is not
> heavily fragmented then the virtual size of the image file will be 
> commensurate
> with the real size. It also doesn't look like a great plus.. Well, at least we
> can discuss it.
> 
> Changes from v1:
> - rewrite qcow2_get_last_cluster() function according to Max's comments. (2)
> 
> Changes from v2:
> - report a warning if truncation of the tail of the image file failed. (2)
> 
> Pavel Butsykin (2):
>   qcow2: fix return error code in qcow2_truncate()
>   qcow2: truncate the tail of the image file after shrinking the image
> 
>  block/qcow2-refcount.c | 22 ++++++++++++++++++++++
>  block/qcow2.c          | 27 +++++++++++++++++++++++++--
>  block/qcow2.h          |  1 +
>  3 files changed, 48 insertions(+), 2 deletions(-)

Thanks, applied to my block branch:

https://github.com/XanClic/qemu/commits/block

Max

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