Re: [Qemu-devel] Supporting unsafe create when backing file is not accessible

2017-07-17 Thread Kevin Wolf
Am 17.07.2017 um 14:25 hat Eric Blake geschrieben: > On 07/17/2017 07:19 AM, Kevin Wolf wrote: > > > While I think adding -u today is reasonably realistic, I'm doubtful that > > we can get an introspection mechanism in place today. Perhaps we can > > declare it a bug fix, but I'd rather not rush

Re: [Qemu-devel] Supporting unsafe create when backing file is not accessible

2017-07-17 Thread Eric Blake
On 07/17/2017 07:19 AM, Kevin Wolf wrote: > While I think adding -u today is reasonably realistic, I'm doubtful that > we can get an introspection mechanism in place today. Perhaps we can > declare it a bug fix, but I'd rather not rush something like that. > > How does libvirt detect qemu-img

Re: [Qemu-devel] Supporting unsafe create when backing file is not accessible

2017-07-17 Thread Kevin Wolf
Am 17.07.2017 um 13:36 hat Eric Blake geschrieben: > On 07/14/2017 02:13 PM, Nir Soffer wrote: > > Eric, we are more concerned about using the current qemu version. > > > > We can use the fact that providing both size and backing format, > > qemu does not open the backing file, but this is not

Re: [Qemu-devel] Supporting unsafe create when backing file is not accessible

2017-07-17 Thread Eric Blake
On 07/14/2017 02:13 PM, Nir Soffer wrote: > Eric, we are more concerned about using the current qemu version. > > We can use the fact that providing both size and backing format, > qemu does not open the backing file, but this is not documented, and > we don't want to base oVirt code on

Re: [Qemu-devel] Supporting unsafe create when backing file is not accessible

2017-07-17 Thread Kevin Wolf
Am 14.07.2017 um 21:13 hat Nir Soffer geschrieben: > On Wed, Jul 12, 2017 at 5:40 PM Eric Blake wrote: > > > On 07/12/2017 03:56 AM, Ala Hino wrote: > > > Hi, > > > > > > We encountered a performance issue when creating a volume for a running > > VM > > > and we'd like to

Re: [Qemu-devel] Supporting unsafe create when backing file is not accessible

2017-07-14 Thread Nir Soffer
On Wed, Jul 12, 2017 at 5:40 PM Eric Blake wrote: > On 07/12/2017 03:56 AM, Ala Hino wrote: > > Hi, > > > > We encountered a performance issue when creating a volume for a running > VM > > and we'd like to share the info with you. The root cause of the issue is > in > > our

Re: [Qemu-devel] Supporting unsafe create when backing file is not accessible

2017-07-12 Thread Eric Blake
On 07/12/2017 03:56 AM, Ala Hino wrote: > Hi, > > We encountered a performance issue when creating a volume for a running VM > and we'd like to share the info with you. The root cause of the issue is in > our code but we found a workaround that relies on qemu-img create > undocumented behavior. >

[Qemu-devel] Supporting unsafe create when backing file is not accessible

2017-07-12 Thread Ala Hino
Hi, We encountered a performance issue when creating a volume for a running VM and we'd like to share the info with you. The root cause of the issue is in our code but we found a workaround that relies on qemu-img create undocumented behavior. During our tests, we found that in order to create a