Re: [Qemu-devel] [PATCH 0/8] add basic recovery logic to quorum driver

["Benoît Canet" <benoit.canet@irqsave.net>]

The Wednesday 10 Sep 2014 à 15:18:22 (+0800), Liu Yuan wrote :
> On Sun, Sep 07, 2014 at 05:12:31PM +0200, Benoît Canet wrote:
> > The Monday 01 Sep 2014 à 15:43:06 (+0800), Liu Yuan wrote :
> > > This patch set mainly add mainly two logics to implement device recover
> > > - notify qourum driver of the broken states from the child driver(s)
> > > - dirty track and sync the device after it is repaired
> > > 
> > > Thus quorum allow VMs to continue while some child devices are broken and when
> > > the child devices are repaired and return back, we sync dirty bits during
> > > downtime to keep data consistency.
> > > 
> > > The recovery logic is based on the driver state bitmap and will sync the dirty
> > > bits with a timeslice window in a coroutine in this prtimive implementation.
> > > 
> > > Simple graph about 2 children with threshold=1 and read-pattern=fifo:
> > > (similary to DRBD)
> > > 
> > > + denote device sync iteration
> > > - IO on a single device
> > > = IO on two devices
> > > 
> > >                                       sync complete, release dirty bitmap
> > >                                          ^
> > >                                          |
> > >   ====-----------------++++----++++----++==========
> > >      |                 |
> > >      |                 v
> > >      |               device repaired and begin to sync
> > >      v
> > >    device broken, create a dirty bitmap
> > > 
> > >   This sync logic can take care of nested broken problem, that devices are
> > >   broken while in sync. We just start a sync process after the devices are
> > >   repaired again and switch the devices from broken to sound only when the sync
> > >   completes.
> > > 
> > > For read-pattern=quorum mode, it enjoys the recovery logic without any problem.
> > > 
> > > Todo:
> > > - use aio interface to sync data (multiple transfer in one go)
> > > - dynamic slice window to control sync bandwidth more smoothly
> > > - add auto-reconnection mechanism to other protocol (if not support yet)
> > > - add tests
> > > 
> > > Cc: Eric Blake <eblake@redhat.com>
> > > Cc: Benoit Canet <benoit@irqsave.net>
> > > Cc: Kevin Wolf <kwolf@redhat.com>
> > > Cc: Stefan Hajnoczi <stefanha@redhat.com>
> > > 
> > > Liu Yuan (8):
> > >   block/quorum: initialize qcrs.aiocb for read
> > >   block: add driver operation callbacks
> > >   block/sheepdog: propagate disconnect/reconnect events to upper driver
> > >   block/quorum: add quorum_aio_release() helper
> > >   quorum: fix quorum_aio_cancel()
> > >   block/quorum: add broken state to BlockDriverState
> > >   block: add two helpers
> > >   quorum: add basic device recovery logic
> > > 
> > >  block.c                   |  17 +++
> > >  block/quorum.c            | 324 +++++++++++++++++++++++++++++++++++++++++-----
> > >  block/sheepdog.c          |   9 ++
> > >  include/block/block.h     |   9 ++
> > >  include/block/block_int.h |   6 +
> > >  trace-events              |   5 +
> > >  6 files changed, 336 insertions(+), 34 deletions(-)
> > > 
> > > -- 
> > > 1.9.1
> > > 
> > 
> > Hi liu,
> > 
> > Had you noticed that your series conflict with one of Fam's series in the quorum cancel
> > function fix patch ?
> 
> Not yet, thanks for reminding.
I think Fam somehow digested you patch.
> 
> > Could you find an arrangement with Fam so the two patches don't collide anymore ?
> > 
> > Do you intend to respin your series ?
> 
> Yes, I'll rebase the v2 later before more possible reviews.
> 
> Thanks
> Yuan
>