Re: [PATCH] xprtrdma: take vendor driver refcount at client

[Chuck Lever <chuck.lever-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>]

On Jul 28, 2015, at 4:46 AM, Sagi Grimberg <sagig-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org> wrote:

> On 7/28/2015 2:01 AM, Devesh Sharma wrote:
>> Thanks Chuck Lever for the valuable feedback and suggestions.
>> 
>> This is a rework of the following patch sent almost a year back:
>> http://www.mail-archive.com/linux-rdma%40vger.kernel.org/msg20730.html
>> 
>> In presence of active mount if someone tries to rmmod vendor-driver, the
>> command remains stuck forever waiting for destruction of all rdma-cm-id.
>> in worst case client can crash during shutdown with active mounts.
> 
> Ouch, taking a reference on the module preventing it from unloading is
> not very well behaved (putting it nicely). That's also breaking the
> layering of ULPs <-> core <-> provider scheme.
> 
> Why not just cleanup everything upon DEVICE_REMOVAL?

xprtrdma does not support DEVICE_REMOVAL yet. That's why we are
taking this temporary approach.


>> The existing code assumes that ia->ri_id->device cannot change during
>> the lifetime of a transport. Lifting that assumption is a long chain
>> of work, and is in plan.
>> 
>> The community decided that preventing the hang right now is more
>> important than waiting for architectural changes.
> 
> Well, if you are putting a bandage here - the code should be documented
> with a proper FIXME.

That's a good suggestion.


--
Chuck Lever



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