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Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks.
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks. |
Date: |
Tue, 08 Dec 2009 10:40:15 +0100 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.4pre) Gecko/20091014 Fedora/3.0-2.8.b4.fc11 Thunderbird/3.0b4 |
Am 07.12.2009 15:53, schrieb Anthony Liguori:
> Daniel P. Berrange wrote:
>> It is safe if you assume that no one else has tried to modify the disk
>> since you opened it, otherwise you'd be commiting changes against a
>> base state which no longer exists.
>
> 1) first user opens cow1.qcow, acquires F_WRLCK
> 2) first user opens base.qcow, acquires F_RDLCK
> 3) second user opens cow2.qcow, acquires F_WRLCK
> 4) second user opens base.qcow, acquires F_RDLCK
>
> 5) second user attempts to commit cow2.qcow to base.qcow
This is broken regardless of locking (except for very... special use
that I don't want to even think about, I'd call it criminal). Better
don't commit to a backing file that is used by other COW images.
Kevin
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., (continued)
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Richard W.M. Jones, 2009/12/07
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Jamie Lokier, 2009/12/07
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Daniel P. Berrange, 2009/12/07
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Richard W.M. Jones, 2009/12/07
- [Qemu-devel] Re: [PATCH] Disk image shared and exclusive locks., Paolo Bonzini, 2009/12/07
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Anthony Liguori, 2009/12/07
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Daniel P. Berrange, 2009/12/07
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Anthony Liguori, 2009/12/07
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Daniel P. Berrange, 2009/12/07
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Anthony Liguori, 2009/12/07
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks.,
Kevin Wolf <=
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Richard W.M. Jones, 2009/12/07
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Richard W.M. Jones, 2009/12/07
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Jamie Lokier, 2009/12/07
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Anthony Liguori, 2009/12/07
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Richard W.M. Jones, 2009/12/07
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Anthony Liguori, 2009/12/07
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Richard W.M. Jones, 2009/12/07
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Anthony Liguori, 2009/12/07
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Kevin Wolf, 2009/12/08
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Richard W.M. Jones, 2009/12/08