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Re: [Qemu-devel] Fwd: qemu drive mirror assert fault
From: |
Fam Zheng |
Subject: |
Re: [Qemu-devel] Fwd: qemu drive mirror assert fault |
Date: |
Tue, 5 May 2015 20:09:25 +0800 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Tue, 05/05 13:48, Kevin Wolf wrote:
> Am 05.05.2015 um 12:27 hat Fam Zheng geschrieben:
> > On Tue, 05/05 12:13, Paolo Bonzini wrote:
> > >
> > >
> > > On 05/05/2015 09:36, Fam Zheng wrote:
> > > I don't think this commit is relevant. The bug is caused by
> > > bdrv_co_discard clearing the bitmap (which is not supported during
> > > iteration, and is caught by the assertion). That bdrv_reset_dirty is
> > > not removed by the commit you pointed out.
> >
> > You are right, I think the bug is the bdrv_reset_dirty in bdrv_co_discard.
> > The
> > discard may zero out the src area (depending on the backend), we should
> > probably replicate this to dest (actual data or the discard operation),
> > rather
> > than forgetting the change.
>
> It depends. In its basic form, bdrv_discard() just means "I don't care
> about the data any more". Then clearing the dirty bitmap is correct.
>
> The content is only important if the caller used discard to write zeros
> because can_write_zeroes_with_unmap = true. Do we have any such callers
> apart from qemu-img convert?
The guest could be taking advantage of this "can_write_zeroes_with_unmap"..
Fam
- Re: [Qemu-devel] Fwd: qemu drive mirror assert fault, Fam Zheng, 2015/05/05
- Re: [Qemu-devel] Fwd: qemu drive mirror assert fault, Paolo Bonzini, 2015/05/05
- Re: [Qemu-devel] Fwd: qemu drive mirror assert fault, Fam Zheng, 2015/05/05
- Re: [Qemu-devel] Fwd: qemu drive mirror assert fault, Kevin Wolf, 2015/05/05
- Re: [Qemu-devel] Fwd: qemu drive mirror assert fault, Paolo Bonzini, 2015/05/05
- Re: [Qemu-devel] Fwd: qemu drive mirror assert fault, Paolo Bonzini, 2015/05/05
- Re: [Qemu-devel] Fwd: qemu drive mirror assert fault, Kevin Wolf, 2015/05/05
- Re: [Qemu-devel] Fwd: qemu drive mirror assert fault, Paolo Bonzini, 2015/05/05
- Re: [Qemu-devel] Fwd: qemu drive mirror assert fault, Kevin Wolf, 2015/05/05
- Re: [Qemu-devel] Fwd: qemu drive mirror assert fault,
Fam Zheng <=