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Re: [Qemu-devel] [PATCH for-2.7 v2 07/17] rbd: Implement image locking
From: |
Fam Zheng |
Subject: |
Re: [Qemu-devel] [PATCH for-2.7 v2 07/17] rbd: Implement image locking |
Date: |
Thu, 28 Apr 2016 09:33:55 +0800 |
User-agent: |
Mutt/1.6.0 (2016-04-01) |
On Wed, 04/27 13:18, Jason Dillaman wrote:
> On Tue, Apr 26, 2016 at 7:20 PM, Fam Zheng <address@hidden> wrote:
> > On Tue, 04/26 10:42, Jason Dillaman wrote:
> >> On Sun, Apr 24, 2016 at 7:42 PM, Fam Zheng <address@hidden> wrote:
> >> > On Fri, 04/22 21:57, Jason Dillaman wrote:
> >> >> Since this cannot automatically recover from a crashed QEMU client with
> >> >> an
> >> >> RBD image, perhaps this RBD locking should not default to enabled.
> >> >> Additionally, this will conflict with the "exclusive-lock" feature
> >> >> available since the Ceph Hammer-release since both utilize the same
> >> >> locking
> >> >> construct.
> >> >>
> >> >> As a quick background, the optional exclusive-lock feature can be
> >> >> enabled/disabled on image and safely/automatically handles the case of
> >> >> recovery from a crashed client. Under normal conditions, the RBD
> >> >> exclusive-lock feature automatically acquires the lock upon the first
> >> >> attempt to write to the image and transparently transitions ownership of
> >> >> the lock between two or more clients -- used for QEMU live-migration.
> >> >
> >> > Is it enabled by default?
> >> >
> >>
> >> Starting with the Jewel release of Ceph it is enabled by default.
> >
> > OK, then I'll leave rbd in this QEMU series for now.
>
> Without exposing some new API methods, this patch will, unfortunately,
> directly conflict with the new Jewel rbd defaults and will actually
> result in the image becoming read-only since librbd won't be able to
> acquire the exclusive lock when QEMU owns the advisory lock.
>
> We can probably get the new API methods upstream within a week or two
> [1]. If that's too long of a delay, I'd recommend dropping rbd
> locking from the series for now.
Yes you are right, I tried to mean "drop" with "leave" :)
Thanks,
Fam
>
> [1] http://tracker.ceph.com/issues/15632
>
> --
> Jason
- Re: [Qemu-devel] [PATCH for-2.7 v2 05/17] raw-posix: Implement .bdrv_lockf, (continued)
[Qemu-devel] [PATCH for-2.7 v2 06/17] gluster: Implement .bdrv_lockf, Fam Zheng, 2016/04/14
[Qemu-devel] [PATCH for-2.7 v2 07/17] rbd: Implement image locking, Fam Zheng, 2016/04/14
[Qemu-devel] [PATCH for-2.7 v2 08/17] qemu-io: Add "-L" option for BDRV_O_NO_LOCK, Fam Zheng, 2016/04/14
[Qemu-devel] [PATCH for-2.7 v2 09/17] qemu-img: Add "-L" option to sub commands, Fam Zheng, 2016/04/14
[Qemu-devel] [PATCH for-2.7 v2 11/17] qemu-nbd: Add "--no-lock/-L" option, Fam Zheng, 2016/04/14