linux-kernel - [PATCH 0/2] do not squash mapping flags and gfp_mask together (was: Re: [PATCH -v2] mm: Don't use radix tree writeback tags for pages in)

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Date:   Mon, 12 Sep 2016 13:16:06 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
        "Huang, Ying" <ying.huang@...el.com>, tim.c.chen@...el.com,
        dave.hansen@...el.com, andi.kleen@...el.com, aaron.lu@...el.com,
        Hugh Dickins <hughd@...gle.com>, Shaohua Li <shli@...nel.org>,
        Minchan Kim <minchan@...nel.org>,
        Rik van Riel <riel@...hat.com>, Tejun Heo <tj@...nel.org>,
        Wu Fengguang <fengguang.wu@...el.com>
Subject: [PATCH 0/2] do not squash mapping flags and gfp_mask together (was: Re: [PATCH -v2] mm: Don't use radix tree writeback tags for pages in)

On Thu 01-09-16 11:13:47, Michal Hocko wrote:
> On Wed 31-08-16 14:30:31, Andrew Morton wrote:
> > On Wed, 31 Aug 2016 10:14:59 +0100 Mel Gorman <mgorman@...hsingularity.net> wrote:
[...]
> > > I didn't see anything wrong with the patch but it's worth highlighting
> > > that this hunk means we are now out of GFP bits.
> > 
> > Well ugh.  What are we to do about that?
> 
> Can we simply give these AS_ flags their own word in mapping rather than
> squash them together with gfp flags and impose the restriction on the
> number of gfp flags. There was some demand for new gfp flags already and
> mapping flags were in the way.

OK, it seems this got unnoticed. What do you think about the following
two patches? I have only compile tested them and git grep suggests
nobody else should be relying on storing gfp_mask into flags directly.
So either I my grep-foo fools me or this should be safe. The two patches
will come as a reply to this email.