Am 29.01.2013 14:45, schrieb Benoît Canet: > Le Tuesday 29 Jan 2013 à 14:25:42 (+0100), Kevin Wolf a écrit : >> Am 29.01.2013 14:07, schrieb Benoît Canet: >>>> Wait, what's happening here? I don't understand this patch and how it's >>>> related to snapshotting non-file protocols (if this is even what you >>>> mean). What is your exact scenario, what does the existing code do in >>>> it, and how does this change improve it? An empty commit message is >>>> definitely not appropriate for such a change. >>>> >>>> In any case, using NULL as drv for bdrv_open() looks plain wrong. >>> >>> When passing drv bdrv_open tries to open the url as qcow2 or another plain >>> file >>> format and fail. >> >> What exactly is a "plain file format" and what is the difference between >> it and other file formats? > > Quorum is a protocol which encapsulate n BlockDriverState.
So it's not a file format, neither plain nor otherwise. >> Anyway, this is not a problem description, let alone a description of >> your exact scenario. > > A scenario would be: > A user want to create a new quorum snapshot made of n qcow2 snapshots. > The user specify qcow2 as format so the new quorum files are created as qcow2. > Then the code try to open the quorum file as a qcow2 file and it fail. Like this? base1 [file] --- base1 [qcow2] --\ base2 [file] --- base2 [qcow2] --->-- quorum --- snap.qcow2 base3 [file] --- base3 [qcow2] --/ Or like this? (This is the only one where quorum is really used as a protocol) base1 [file] --\ base2 [file] --->-- quorum --- base [qcow2] --- snap.qcow2 base3 [file] --/ Or even this one? base1 [file] --- base1 [qcow2] --- snap1.qcow2 --\ base2 [file] --- base2 [qcow2] --- snap2.qcow2 --->-- quorum base3 [file] --- base3 [qcow2] --- snap3.qcow2 --/ I think the last one is what you really want, but it's certainly not the case that is enabled by this patch. >> If qcow2 is specified as the format in the QMP command, why is it then >> wrong to try and open the file as qcow2? Why does it fail? What is the >> correct driver? > > It's correct to format the individual quorum files as qcow2 so specifying > qcow2 > in the qmp command seems ok. > But opening a "quorum:" url which agregate these qcow2 files will fail if drv > is > the qcow2 driver. > Would passing the quorum protocol driver to bdrv_open be ok ? A quorum: URL opened with the qcow2 driver should succeed and result in something like the second case mentioned above. Kevin