Date: Wed, 26 Aug 2015 09:20:16 +0200
From: Michal Hocko <mhocko@kernel.org>
To: Eric B Munson <emunson@akamai.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Vlastimil Babka <vbabka@suse.cz>, Jonathan Corbet <corbet@lwn.net>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
        linux-mm@kvack.org, linux-api@vger.kernel.org
Subject: Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT
Message-ID: <20150826072016.GD25196@dhcp22.suse.cz>
References: <20150812115909.GA5182@dhcp22.suse.cz>
 <20150819213345.GB4536@akamai.com>
 <20150820075611.GD4780@dhcp22.suse.cz>
 <20150820170309.GA11557@akamai.com>
 <20150821072552.GF23723@dhcp22.suse.cz>
 <20150821183132.GA12835@akamai.com>
 <20150825134154.GB6285@dhcp22.suse.cz>
 <20150825142902.GF17005@akamai.com>
 <20150825185829.GA10222@dhcp22.suse.cz>
 <20150825190300.GG17005@akamai.com>
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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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