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

[Liu Yuan <namei.unix@gmail.com>]

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.

> 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