v4.14-rc5 NVMeOF regression?

[Christoph Hellwig]

On Wed, Oct 18, 2017 at 08:26:05AM +0300, Sagi Grimberg wrote:
> > Additionally, can you explain to me why you think the above patch is
> > necessary? As far as I can see nvme_rdma_ctrl_mutex is not held around
> > the ib_register_client(&nvme_rdma_ib_client) call nor around the
> > ib_unregister_client(&nvme_rdma_ib_client) calls.
> 
> Its held under ib_unregister_client, my understanding is that the
> _nested annotation is required for the inner mutex lock acquire.

No.  Anytime we take a single lock out of order it is a bug an a
potential deadlock.  _nested only works if we have multiple instances
of a lock (say in each inode) and we have a well defined ordering
between the instances (e.g. by the address of the inode structure).