From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christopher Lameter <cl-vYTEC60ixJUAvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH RFC v2 4/4] mm/mempolicy: add nodes_empty check in
 SYSC_migrate_pages
Date: Tue, 7 Nov 2017 08:54:46 -0600 (CST)
Message-ID: <alpine.DEB.2.20.1711070851560.18776@nuc-kabylake>
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To: Yisheng Xie <xieyisheng1-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
Cc: Vlastimil Babka <vbabka-AlSwsSmVLrQ@public.gmane.org>, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, mhocko-IBi9RG/b67k@public.gmane.org, mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, rientjes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, n-horiguchi-PaJj6Psr51x8UrSeD/g0lQ@public.gmane.org, salls-b3bnyZ7c9ISVc3sceRu5cw@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, tanxiaojun-hv44wF8Li93QT0dZR+AlfA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Andi Kleen <ak-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
List-Id: linux-api@vger.kernel.org

On Tue, 7 Nov 2017, Yisheng Xie wrote:

> On 2017/11/6 23:29, Christopher Lameter wrote:
> > On Mon, 6 Nov 2017, Vlastimil Babka wrote:
> >
> >> I'm not sure what exactly is the EPERM intention. Should really the
> >> capability of THIS process override the cpuset restriction of the TARGET
> >> process? Maybe yes. Then, does "insufficient privilege (CAP_SYS_NICE) to
> >
> > CAP_SYS_NICE never overrides cpuset restrictions. The cap can be used to
> > migrate pages that are *also* mapped by other processes (and thus move
> > pages of another process which may have different cpu set restrictions!).
>
> So you means the specified nodes should be a subset of target cpu set, right?

The specified nodes need to be part of the *current* cpu set.

Migrate pages moves the pages of a single process there is no TARGET
process.

Thus thehe *target* nodes need to be a subset of the current cpu set.