Re: [Qemu-devel] [PATCH] qed: add qed-tool.py image manipulation utility

[Stefan Hajnoczi]

On Fri, Dec 2, 2011 at 11:13 AM, Kevin Wolf <address@hidden> wrote:
> Am 02.12.2011 11:23, schrieb Stefan Hajnoczi:
>> On Fri, Dec 2, 2011 at 9:15 AM, Kevin Wolf <address@hidden> wrote:
>>> Am 01.12.2011 18:00, schrieb Stefan Hajnoczi:
>>>> The qed-tool.py utility can inspect and manipulate QED image files.  It
>>>> can be used for testing to see the state of image metadata and also to
>>>> inject corruptions into the image file.  It also has a scrubbing feature
>>>> to copy just the metadata out of an image file, allowing users to share
>>>> broken image files without revealing data in bug reports.
>>>>
>>>> This has lived in my local repo for a long time but could be useful to
>>>> others.
>>>>
>>>> Signed-off-by: Stefan Hajnoczi <address@hidden>
>>>
>>> For most of the commands, I think qemu-img/qemu-io should be extended
>>> instead of creating scripts for one or two formats and lacking the
>>> functionality for the rest.
>>
>> I have mixed feelings about that because I don't think a common
>> interface will ever live up to its promise.  We will have an interface
>> that no two file formats implement much of (i.e. lots of NULL function
>> pointers).  The user experience will be that these commands don't work
>> ("Operation not supported") and it's more flexible (and less code) to
>> write a format-specific script like this.
>>
>> Also, usually before I use any of these potentially destructive
>> commands I review the script's code to double-check exactly what the
>> impact on the file will be.  It's nice to have a concise Python script
>> that can be reviewed easily rather than looking through layers of
>> production C code.
>>
>> Do you really think there is much worth making common here?
>
> Ok, I had another, closer look and there are two functions that I would
> prefer to see in qemu-img info, namely fragmentation and dirty flag
> status. For the rest you're probably right that an external script makes
> more sense.

Okay, I will resubmit with patches to implement those two and a
cut-down qed-tool.py.

Stefan