[Qemu-devel] [PATCH RFC] block: Tolerate existing writers on read only BdrvChild

2017-03-01 Thread Fam Zheng
In an ideal world, read-write access to an image is inherently exclusive, because we cannot guarantee other readers and writers a consistency view of the whole image at all point. That's what the current permission system does, and it is okay as long as it is entirely internal. But that would chang

Re: [Qemu-devel] [PATCH RFC] block: Tolerate existing writers on read only BdrvChild

2017-03-01 Thread Kevin Wolf
Am 01.03.2017 um 09:15 hat Fam Zheng geschrieben: > In an ideal world, read-write access to an image is inherently > exclusive, because we cannot guarantee other readers and writers a > consistency view of the whole image at all point. That's what the > current permission system does, and it is oka

Re: [Qemu-devel] [PATCH RFC] block: Tolerate existing writers on read only BdrvChild

2017-03-01 Thread Fam Zheng
On Wed, 03/01 10:49, Kevin Wolf wrote: > Am 01.03.2017 um 09:15 hat Fam Zheng geschrieben: > > In an ideal world, read-write access to an image is inherently > > exclusive, because we cannot guarantee other readers and writers a > > consistency view of the whole image at all point. That's what the

Re: [Qemu-devel] [PATCH RFC] block: Tolerate existing writers on read only BdrvChild

2017-03-01 Thread Kevin Wolf
Am 01.03.2017 um 13:39 hat Fam Zheng geschrieben: > On Wed, 03/01 10:49, Kevin Wolf wrote: > > Am 01.03.2017 um 09:15 hat Fam Zheng geschrieben: > > > In an ideal world, read-write access to an image is inherently > > > exclusive, because we cannot guarantee other readers and writers a > > > consis

Re: [Qemu-devel] [PATCH RFC] block: Tolerate existing writers on read only BdrvChild

2017-03-01 Thread Fam Zheng
On Wed, 03/01 16:16, Kevin Wolf wrote: > > I'm not sure about this because: 1) this is intrusive from a user PoV, many > > scripts and upper layer tools will stop working; > > Are you sure? I don't expect user scripts or even proper management > tools to use qemu-io on running VMs. I do expect tha

Re: [Qemu-devel] [PATCH RFC] block: Tolerate existing writers on read only BdrvChild

2017-03-01 Thread Kevin Wolf
Am 01.03.2017 um 17:10 hat Fam Zheng geschrieben: > On Wed, 03/01 16:16, Kevin Wolf wrote: > > > I'm not sure about this because: 1) this is intrusive from a user PoV, > > > many > > > scripts and upper layer tools will stop working; > > > > Are you sure? I don't expect user scripts or even prope

Re: [Qemu-devel] [PATCH RFC] block: Tolerate existing writers on read only BdrvChild

2017-03-02 Thread Fam Zheng
On Wed, 03/01 17:22, Kevin Wolf wrote: > Am 01.03.2017 um 17:10 hat Fam Zheng geschrieben: > > On Wed, 03/01 16:16, Kevin Wolf wrote: > > > > I'm not sure about this because: 1) this is intrusive from a user PoV, > > > > many > > > > scripts and upper layer tools will stop working; > > > > > > Ar

Re: [Qemu-devel] [PATCH RFC] block: Tolerate existing writers on read only BdrvChild

2017-03-02 Thread Kevin Wolf
Am 02.03.2017 um 12:21 hat Fam Zheng geschrieben: > On Wed, 03/01 17:22, Kevin Wolf wrote: > > Am 01.03.2017 um 17:10 hat Fam Zheng geschrieben: > > > On Wed, 03/01 16:16, Kevin Wolf wrote: > > > > > I'm not sure about this because: 1) this is intrusive from a user > > > > > PoV, many > > > > > sc

Re: [Qemu-devel] [PATCH RFC] block: Tolerate existing writers on read only BdrvChild

2017-03-02 Thread Fam Zheng
On Thu, 03/02 15:23, Kevin Wolf wrote: > Am 02.03.2017 um 12:21 hat Fam Zheng geschrieben: > > On Wed, 03/01 17:22, Kevin Wolf wrote: > > > Am 01.03.2017 um 17:10 hat Fam Zheng geschrieben: > > > > On Wed, 03/01 16:16, Kevin Wolf wrote: > > > > > > I'm not sure about this because: 1) this is intrus