Re: [Qemu-devel] [PATCH V4 1/4] Implement sync modes for drive-backup.

[Eric Blake]

On 07/18/2013 01:06 PM, Ian Main wrote:
> On Thu, Jul 18, 2013 at 11:19:43AM -0600, Eric Blake wrote:
>> On 07/17/2013 02:04 PM, Ian Main wrote:
>>> This patch adds sync-modes to the drive-backup interface and
>>> implements the FULL, NONE and TOP modes of synchronization.
>>>

>>> @@ -1807,6 +1807,10 @@
>>>  # @format: #optional the format of the new destination, default is to
>>>  #          probe if @mode is 'existing', else the format of the source
>>>  #
>>> +# @sync: what parts of the disk image should be copied to the destination
>>> +#        (all the disk, only the sectors allocated in the topmost image, or
>>> +#        only new I/O).
>>> +#
>>>  # @mode: #optional whether and how QEMU should create a new image, default 
>>> is
>>>  #        'absolute-paths'.
>>
>> This hunk looks bogus; the 'DriveBackup' type already documents @sync as
>> of commit b53169e, which makes me suspect this hunk got misapplied
>> during rebasing.
> 
> Did you check that?  I know there was one bit of documentation missing
> that I fixed here.  I also just did a clean rebase (git am) to
> kevin/block and it all applied fine.

Yes, it _applied_ fine, because of git's insistence on applying hunks
regardless of line fuzzing.  It probably applied to 'drive-mirror',
since I see this context in the section for 'drive-mirror' when reading
the unpatched file at current qemu.git head:

> # @format: #optional the format of the new destination, default is to
> #          probe if @mode is 'existing', else the format of the source
> #
> # @mode: #optional whether and how QEMU should create a new image, default is
> #        'absolute-paths'.
> #

Hence, my argument that you DON'T want this hunk.

>>>  Example:
>>>  -> { "execute": "drive-backup", "arguments": { "device": "drive0",
>>> +                                               "sync": "full",
>>>                                                 "target": "backup.img" } }
>>
>> Ouch - commit b53169e made 'sync' mandatory, but forgot to update the
>> example to match; perhaps this hunk ought to be applied independently?
> 
> That's up to you guys, I can split it out if needed.

I don't care either way as long as it gets fixed before 1.6; it all
depends on how long the review of the rest of your series takes.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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