Re: [RFC PATCH 2/2] mm/gup: introduce vaddr_pin_pages_remote()

From: Ira Weiny <ira.weiny@intel.com>
To: Jan Kara <jack@suse.cz>
Cc: "John Hubbard" <jhubbard@nvidia.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Christoph Hellwig" <hch@infradead.org>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Dave Chinner" <david@fromorbit.com>,
	"Jason Gunthorpe" <jgg@ziepe.ca>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
	linux-rdma@vger.kernel.org
Subject: Re: [RFC PATCH 2/2] mm/gup: introduce vaddr_pin_pages_remote()
Date: Fri, 16 Aug 2019 11:33:38 -0700	[thread overview]
Message-ID: <20190816183337.GA371@iweiny-DESK2.sc.intel.com> (raw)
In-Reply-To: <20190816154108.GE3041@quack2.suse.cz>

On Fri, Aug 16, 2019 at 05:41:08PM +0200, Jan Kara wrote:
> On Thu 15-08-19 19:14:08, John Hubbard wrote:
> > On 8/15/19 10:41 AM, John Hubbard wrote:
> > > On 8/15/19 10:32 AM, Ira Weiny wrote:
> > >> On Thu, Aug 15, 2019 at 03:35:10PM +0200, Jan Kara wrote:
> > >>> On Thu 15-08-19 15:26:22, Jan Kara wrote:
> > >>>> On Wed 14-08-19 20:01:07, John Hubbard wrote:
> > >>>>> On 8/14/19 5:02 PM, John Hubbard wrote:
> > ...
> > >> Ok just to make this clear I threw up my current tree with your patches here:
> > >>
> > >> https://github.com/weiny2/linux-kernel/commits/mmotm-rdmafsdax-b0-v4
> > >>
> > >> I'm talking about dropping the final patch:
> > >> 05fd2d3afa6b rdma/umem_odp: Use vaddr_pin_pages_remote() in ODP
> > >>
> > >> The other 2 can stay.  I split out the *_remote() call.  We don't have a user
> > >> but I'll keep it around for a bit.
> > >>
> > >> This tree is still WIP as I work through all the comments.  So I've not changed
> > >> names or variable types etc...  Just wanted to settle this.
> > >>
> > > 
> > > Right. And now that ODP is not a user, I'll take a quick look through my other
> > > call site conversions and see if I can find an easy one, to include here as
> > > the first user of vaddr_pin_pages_remote(). I'll send it your way if that
> > > works out.
> > > 
> > 
> > OK, there was only process_vm_access.c, plus (sort of) Bharath's sgi-gru
> > patch, maybe eventually [1].  But looking at process_vm_access.c, I think 
> > it is one of the patches that is no longer applicable, and I can just
> > drop it entirely...I'd welcome a second opinion on that...
> 
> I don't think you can drop the patch. process_vm_rw_pages() clearly touches
> page contents and does not synchronize with page_mkclean(). So it is case
> 1) and needs FOLL_PIN semantics.

John could you send a formal patch using vaddr_pin* and I'll add it to the
tree?

Ira

> 
> 								Honza
> -- 
> Jan Kara <jack@suse.com>
> SUSE Labs, CR
> 