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Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks.
From: |
Jamie Lokier |
Subject: |
Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks. |
Date: |
Mon, 7 Dec 2009 11:19:54 +0000 |
User-agent: |
Mutt/1.5.13 (2006-08-11) |
Daniel P. Berrange wrote:
> > Sometimes shared access to a raw image (partitioned or whole disk
> > filesystem) is ok, and sometimes it is not ok. Only the user knows
> > the difference, because only the user knows if the guests they are
> > running use distinct partitions in the same raw image, or cooperative
> > access to a shard image.
> >
> > But does it make sense to request a shared lock in that case? Not
> > really. If you have a group of guests correctly sharing an image, you
> > still want to prevent running the same group a second time - and a
> > shared lock wouldn't do that, because each group would be requesting
> > shared locks.
> >
> > So the distinction read/write makes more sense. Can anyone think of a
> > situation where a shared lock on an image opened for writing is useful?
>
> Isn't this what Richard has already done ? The patch implements 'shared'
> as a 'F_RDLCK' lock and 'exclusive' as 'F_WRLCK':
No, the question is whether it makes sense to provide a 'shared'
option on the command line, or simply to always map:
image opened read only => F_FDLCK
image opened writable => F_WRLCK
and provide only a single command line option: 'lock'.
-- Jamie
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., (continued)
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Avi Kivity, 2009/12/05
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Anthony Liguori, 2009/12/05
- 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., Kevin Wolf, 2009/12/07
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Avi Kivity, 2009/12/07
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks., Kevin Wolf, 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., Kevin Wolf, 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., Daniel P. Berrange, 2009/12/07
- Re: [Qemu-devel] [PATCH] Disk image shared and exclusive locks.,
Jamie Lokier <=
- 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
- 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