linux-kernel - Re: [PATCH] mm, gup: introduce concept of "foreign" get_user

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Date:	Wed, 20 Jan 2016 10:48:33 -0800
From:	Dave Hansen <dave@...1.net>
To:	Vlastimil Babka <vbabka@...e.cz>, linux-kernel@...r.kernel.org
Cc:	linux-mm@...ck.org, x86@...nel.org, dave.hansen@...ux.intel.com,
	akpm@...ux-foundation.org, kirill.shutemov@...ux.intel.com,
	aarcange@...hat.com, n-horiguchi@...jp.nec.com, jack@...e.cz
Subject: Re: [PATCH] mm, gup: introduce concept of "foreign" get_user_pages()

On 01/20/2016 09:56 AM, Vlastimil Babka wrote:
> On 01/20/2016 06:35 PM, Dave Hansen wrote:
>> This also switches get_user_pages_(un)locked() over to be like
>> get_user_pages() and not take a tsk/mm.  There is no
>> get_user_pages_foreign_(un)locked().  If someone wants that
>> behavior they just have to use "__" variant and pass in
>> FOLL_FOREIGN explicitly.
> 
> Hm so this gets a bit ahead of patch "mm: add gup flag to indicate "foreign" mm
> access", right? It might be cleaner to postpone passing FOLL_FOREIGN until then,
> but not critical.

I've reworded that patch a bit, so it just talks about only enforcing
pkey permissions on non-foreign accesses.  I think I'll keep
FOLL_FOREIGN in this patch because it fits in well with the other things
converted to get_user_pages_foreign().

> BTW doesn't that other patch miss passing FOLL_FOREIGN from
> get_user_pages_foreign() or something? I see it only uses it from break_ksm(),
> am I missing something?

Nope.  At some point along the way, it got dropped in a merge.  Thanks
for catching that!  I'll include it in future versions of this patch.