Re: [PATCH V2 for-next 2/7] IB/core: Add support for idr types

[Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>]

On Thu, Mar 30, 2017 at 06:42:12PM +0300, Matan Barak wrote:
> Yeah, I guess both are ok. I tend to like symmetrical approaches, but
> I don't have a strong objection
> to go with needs_kfree_rcu if you really prefer that.

I think it reads a bit better and there are two fewer branches on
lookup

> > Since it is lookup_get the caller always has to call uobj_put on any
> > failure, and that does fput for fds. No problem?
> >
> 
> Not necessarily. For example, lookup_get could fail because it can't
> find a valid object.  In that case, you have no object to
> put. However, I'll just put a type->lookup_put in the release path,
> so we could move that into the shared code.

Sure, something like that

> We don't have a release memory functions - we got rid of them awhile ago.
> However, when you detach a driver based fd object, and the release
> file_operations of that
> fd points to driver code. You could get a nasty exception if you try
> to close that file
> after unbinding the context because the module was unloaded.

Remember that fops holds a module lock on the functions inside struct
file_operations.

We must ensure that our functions in struct file_operations never call
through to a driver after detach is called.

So, no messing with modules should be needed..

Jason
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