linux-kernel - Re: [PATCH 12/16] mm: consolidate the get_user

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Date:   Thu, 6 Jun 2019 00:44:02 -0700
From:   John Hubbard <jhubbard@...dia.com>
To:     Christoph Hellwig <hch@....de>
CC:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        "David S. Miller" <davem@...emloft.net>,
        Nicholas Piggin <npiggin@...il.com>,
        Khalid Aziz <khalid.aziz@...cle.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        <linux-mips@...r.kernel.org>, <linux-sh@...r.kernel.org>,
        <sparclinux@...r.kernel.org>, <linuxppc-dev@...ts.ozlabs.org>,
        <linux-mm@...ck.org>, <x86@...nel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 12/16] mm: consolidate the get_user_pages* implementations

On 6/5/19 11:20 PM, Christoph Hellwig wrote:
> On Wed, Jun 05, 2019 at 11:01:17PM -0700, John Hubbard wrote:
>> I started reviewing this one patch, and it's kind of messy figuring out
>> if the code motion preserves everything because of
>> all the consolidation from other places, plus having to move things in
>> and out of the ifdef blocks.  So I figured I'd check and see if this is
>> going to make it past RFC status soon, and if it's going before or after
>> Ira's recent RFC ("RDMA/FS DAX truncate proposal").
> 
> I don't like the huge moves either, but I can't really think of any
> better way to do it.  Proposals welcome, though.
> 

One way would be to do it in two patches:

1) Move the code into gup.c, maybe at the bottom. Surround each function
or group of functions by whatever ifdefs they need.

2) Move code out of the bottom of gup.c, into the final location.

...but I'm not certain that will be that much better. In the spirit of
not creating gratuitous work for others, I could try it out and send
out something if it looks like it's noticeably easier to verify/review.

thanks,
-- 
John Hubbard
NVIDIA