RE: [PATCH v11 rdma-next 5/7] RDMA/qedr: Use the common mmap API

[Michal Kalderon <mkalderon@marvell.com>]

> From: linux-rdma-owner@vger.kernel.org <linux-rdma-
> owner@vger.kernel.org> On Behalf Of Gal Pressman
> 
> On 19/09/2019 20:55, Jason Gunthorpe wrote:
> > Huh. If you recall we did all this work with the XA and the free
> > callback because you said qedr was mmaping BAR pages that had some HW
> > lifetime associated with them, and the HW resource was not to be
> > reallocated until all users were gone.
> >
> > I think it would be a better example of this API if you pulled the
> >
> >  	dev->ops->rdma_remove_user(dev->rdma_ctx, ctx->dpi);
> >
> > Into qedr_mmap_free().
> >
> > Then the rdma_user_mmap_entry_remove() will call it naturally as it
> > does entry_put() and if we are destroying the ucontext we already know
> > the mmaps are destroyed.
> >
> > Maybe the same basic comment for EFA, not sure. Gal?
> 
> That's what EFA already does in this series, no?
> We no longer remove entries on dealloc_ucontext, only when the entry is
> freed.

Actually, I think most of the discussions you had on the topic were with Gal, but
Some apply to qedr as well, however, for qedr, the only hw resource we allocate (bar)
is on alloc_ucontext , therefore we were safe to free it on dealloc_ucontext as all mappings
were already zapped. Making the mmap_free a bit redundant for qedr except for the need
to free the entry. 

For EFA, it seemed the only operation delayed was freeing memory - I didn't see hw resources
being freed... Gal?