[libvirt] Re: [PATCH] also allow use of XZ for Qemu image compression

[Chris Lalancette]

Jim Meyering wrote:
> While this patch stays minimal by simply adding XZ/xz to the list,
> I think it would be better to remove lzma, since it uses
> an inferior format (which lacks an integrity check), and
> has been effectively subsumed by xz.
> 
> Let me know if you'd like that, and I'll prepare the slightly
> more invasive patch.

I'm on the fence about it.  While I do understand the situation now (thanks for
explaining), I think keeping lzma for compatibility with older distros might be
a good idea.  Either way, we have to keep the LZMA slot in the enum "free",
since it's part of the on-disk ABI for the save format.  And on that note...

> diff --git a/src/qemu_driver.c b/src/qemu_driver.c
> index f64d70b..7b64712 100644
> --- a/src/qemu_driver.c
> +++ b/src/qemu_driver.c
> @@ -3622,7 +3622,8 @@ enum qemud_save_formats {
>      QEMUD_SAVE_FORMAT_RAW,
>      QEMUD_SAVE_FORMAT_GZIP,
>      QEMUD_SAVE_FORMAT_BZIP2,
> -    QEMUD_SAVE_FORMAT_LZMA,
> +    QEMUD_SAVE_FORMAT_LZMA,  /* deprecated, in favor of xz */
> +    QEMUD_SAVE_FORMAT_XZ,
>      QEMUD_SAVE_FORMAT_LZOP,
>  };

You'll need to add QEMUD_SAVE_FORMAT_XZ to the end of the enum, to maintain
on-disk compatibility.  Otherwise it looks good.

-- 
Chris Lalancette