Re: [for-next 1/2] xprtrdma: take reference of rdma provider module

[Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>]

On 7/17/2014 9:01 AM, Devesh Sharma wrote:
> If verndor driver is attempted for removal while xprtrdma still has an
> active mount, the removal of driver may never complete and can cause
> unseen races or in worst case system crash.
>
> To solve this, xprtrdma module should get reference of struct ib_device
> structure for every mount. Reference is taken after local device address
> resolution is completed successfuly.
>
> reference to the struct ib_device pointer is put just before cm_id destruction.
>
> Signed-off-by: Devesh Sharma <devesh.sharma-laKkSmNT4hbQT0dZR+AlfA@public.gmane.org>

This seems like an issue with the rdma-cm or rdma core, not xprtrdma.  I 
see that user rdma applications cause a ref on the provider module here 
in ib_uverbs_open():

         if (!try_module_get(dev->ib_dev->owner)) {
                 ret = -ENODEV;
                 goto err;


Maybe kernel applications that allocate device resources should cause a 
ref on the provider's module.

Sean/Roland,  is there some history here as to how rdma provider module 
removal should be handled?

Steve.
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