linux-kernel - Re: [PATCH 2/2] mm, thp: consolidate THP gfp handling into alloc_hugepage_direct

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Message-Id: <20181018191147.33e8d5e1ebd785c06aab7b30@linux-foundation.org>
Date:   Thu, 18 Oct 2018 19:11:47 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     "Kirill A. Shutemov" <kirill@...temov.name>,
        Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
        David Rientjes <rientjes@...gle.com>,
        Andrea Argangeli <andrea@...nel.org>,
        Zi Yan <zi.yan@...rutgers.edu>,
        Stefan Priebe - Profihost AG <s.priebe@...fihost.ag>,
        linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] mm, thp: consolidate THP gfp handling into
 alloc_hugepage_direct_gfpmask

On Wed, 26 Sep 2018 16:22:27 +0200 Michal Hocko <mhocko@...nel.org> wrote:

> > MPOL_PREFERRED is handled by policy_node() before we call __alloc_pages_nodemask.
> > __GFP_THISNODE is applied only when we are not using
> > __GFP_DIRECT_RECLAIM which is handled in alloc_hugepage_direct_gfpmask
> > now.
> > Lastly MPOL_BIND wasn't handled explicitly but in the end the removed
> > late check would remove __GFP_THISNODE for it as well. So in the end we
> > are doing the same thing unless I miss something
> 
> Forgot to add. One notable exception would be that the previous code
> would allow to hit
> 	WARN_ON_ONCE(policy->mode == MPOL_BIND && (gfp & __GFP_THISNODE));
> in policy_node if the requested node (e.g. cpu local one) was outside of
> the mbind nodemask. This is not possible now. We haven't heard about any
> such warning yet so it is unlikely that it happens though.

Perhaps a changelog addition is needed to cover the above?

I assume that David's mbind() concern has gone away.

No acks or reviewed-by's yet?