linux-kernel - Re: [RFC PATCH 2/2] mm/gup: introduce vaddr_pin_pages

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Date:   Fri, 16 Aug 2019 11:33:38 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     Jan Kara <jack@...e.cz>
Cc:     John Hubbard <jhubbard@...dia.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Hellwig <hch@...radead.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Chinner <david@...morbit.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Jérôme Glisse <jglisse@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-rdma@...r.kernel.org
Subject: Re: [RFC PATCH 2/2] mm/gup: introduce vaddr_pin_pages_remote()

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 it is one of the patches that is no longer applicable, and I can just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@...e.com>
> SUSE Labs, CR
>