From: Kevin Wolf <kwolf@redhat.com>
To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Avi Kivity <avi@redhat.com>,
"Richard W.M. Jones" <rjones@redhat.com>,
qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks.
Date: Tue, 08 Dec 2009 10:40:15 +0100 [thread overview]
Message-ID: <4B1E1EFF.5010608@redhat.com> (raw)
In-Reply-To: <4B1D16DA.6040405@codemonkey.ws>
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
next prev parent reply other threads:[~2009-12-08 9:41 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-12-04 16:53 [Qemu-devel] [PATCH] Disk image shared and exclusive locks Richard W.M. Jones
2009-12-04 17:15 ` Anthony Liguori
2009-12-04 21:57 ` Richard W.M. Jones
2009-12-04 22:29 ` Anthony Liguori
2009-12-05 17:31 ` Avi Kivity
2009-12-05 17:47 ` Anthony Liguori
2009-12-05 17:55 ` Avi Kivity
2009-12-05 17:59 ` Anthony Liguori
2009-12-07 10:31 ` Jamie Lokier
2009-12-07 10:42 ` Kevin Wolf
2009-12-07 10:48 ` Avi Kivity
2009-12-07 10:56 ` Kevin Wolf
2009-12-07 11:28 ` Jamie Lokier
2009-12-07 11:51 ` Kevin Wolf
2009-12-07 12:06 ` Daniel P. Berrange
2009-12-07 10:45 ` Daniel P. Berrange
2009-12-07 11:19 ` Jamie Lokier
2009-12-07 11:30 ` Daniel P. Berrange
2009-12-07 11:31 ` Richard W.M. Jones
2009-12-07 11:38 ` Jamie Lokier
2009-12-07 11:49 ` Daniel P. Berrange
2009-12-07 11:59 ` Richard W.M. Jones
2009-12-07 14:35 ` [Qemu-devel] " Paolo Bonzini
2009-12-07 13:43 ` [Qemu-devel] " Anthony Liguori
2009-12-07 14:01 ` Daniel P. Berrange
2009-12-07 14:15 ` Anthony Liguori
2009-12-07 14:28 ` Daniel P. Berrange
2009-12-07 14:53 ` Anthony Liguori
2009-12-08 9:40 ` Kevin Wolf [this message]
2009-12-07 11:04 ` Richard W.M. Jones
2009-12-07 10:58 ` Richard W.M. Jones
2009-12-07 11:35 ` Jamie Lokier
2009-12-07 13:39 ` Anthony Liguori
2009-12-07 14:08 ` Richard W.M. Jones
2009-12-07 14:22 ` Anthony Liguori
2009-12-07 14:31 ` Richard W.M. Jones
2009-12-07 14:55 ` Anthony Liguori
2009-12-08 9:48 ` Kevin Wolf
2009-12-08 10:16 ` Richard W.M. Jones
2009-12-07 14:38 ` [Qemu-devel] " Paolo Bonzini
2009-12-07 9:38 ` [Qemu-devel] " Daniel P. Berrange
2009-12-07 10:39 ` Chris Webb
2009-12-07 13:32 ` Anthony Liguori
2009-12-07 13:38 ` Chris Webb
2009-12-07 13:47 ` Anthony Liguori
2009-12-07 14:25 ` Daniel P. Berrange
2009-12-07 14:58 ` Chris Webb
2009-12-07 14:16 ` [Qemu-devel] [PATCH VERSION 2] " Richard W.M. Jones
2009-12-07 15:06 ` Anthony Liguori
2009-12-08 8:48 ` [Qemu-devel] " Paolo Bonzini
2009-12-08 10:00 ` [Qemu-devel] " Kevin Wolf
2009-12-08 10:25 ` Richard W.M. Jones
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