linux-kernel - Re: [PATCH v7 3/6] mm: Introduce VM

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Message-ID: <20150826072016.GD25196@dhcp22.suse.cz>
Date:	Wed, 26 Aug 2015 09:20:16 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Eric B Munson <emunson@...mai.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Jonathan Corbet <corbet@....net>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	linux-mm@...ck.org, linux-api@...r.kernel.org
Subject: Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT

On Tue 25-08-15 15:03:00, Eric B Munson wrote:
[...]
> Would you drop your objections to the VMA flag if I drop the portions of
> the patch that expose it to userspace?
> 
> The rework to not use the VMA flag is pretty sizeable and is much more
> ugly IMO.  I know that you are not wild about using bit 30 of 32 for
> this, but perhaps we can settle on not exporting it to userspace so we
> can reclaim it if we really need it in the future?

Yes, that would be definitely more acceptable for me. I do understand
that you are not wild about changing mremap behavior.

Anyway, I would really prefer if the vma flag was really used only at
few places - when we are clearing it along with VM_LOCKED (which could
be hidden in VM_LOCKED_CLEAR_MASK or something like that) and when we
decide whether the populate or not (this should be __mm_populate). But
maybe I am missing some call paths where gup is called unconditionally,
I haven't checked that.
-- 
Michal Hocko
SUSE Labs
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