Re: [PATCH 3/3] MD: hold mddev lock for md-cluster receive thread

[Shaohua Li <shli@kernel.org>]

On Mon, Aug 01, 2016 at 04:38:59PM +0800, Guoqing Jiang wrote:
> Hi,
> 
> On 07/31/2016 07:54 AM, shli@kernel.org wrote:
> >From: Shaohua Li <shli@fb.com>
> >
> >md-cluster receive thread calls .quiesce too, let it hold mddev lock.
> 
> I'd suggest hold on for the patchset, I can find lock problem easily with
> the patchset applied. Take a resyncing  clusteed raid1 as example.
> 
> md127_raid1 thread held reconfig_mutex then update sb, so it needs dlm
> token lock. Meanwhile md127_resync thread got token lock and wants
> EX on ack lock but recv_daemon can't release ack lock since recv_daemon
> doesn't get reconfig_mutex.

Thansk, I'll drop this one. Other two patches are still safe for md-cluster,
right? I really hope to have consistent locking for .quiesce. For the
process_recvd_msg, I'm wondering what's protecting the datas? for example,
md-cluster uses md_find_rdev_nr_rcu, which access the disks list without
locking. Is there a race? Does it work if we move the mddev lock to
process_recvd_msg?

Thanks,
Shaohua