linux-kernel - Re: [PATCH v1] mm: Fix access of uninitialized memmaps in fs/proc/page.c

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Message-ID: <20191009132950.GB6681@dhcp22.suse.cz>
Date:   Wed, 9 Oct 2019 15:29:50 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Qian Cai <cai@....pw>, Alexey Dobriyan <adobriyan@...il.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Toshiki Fukasawa <t-fukasawa@...jp.nec.com>,
        Konstantin Khlebnikov <koct9i@...il.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Anthony Yznaga <anthony.yznaga@...cle.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Dan Williams <dan.j.williams@...el.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Ira Weiny <ira.weiny@...el.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v1] mm: Fix access of uninitialized memmaps in
 fs/proc/page.c

On Wed 09-10-19 15:24:05, David Hildenbrand wrote:
> On 09.10.19 15:22, Michal Hocko wrote:
> > On Wed 09-10-19 14:58:24, David Hildenbrand wrote:
> > [...]
> >> I would be fine with this, but it means that - for now - the three
> >> /proc/ files won't be able to deal with ZONE_DEVICE memory.
> > 
> > Thanks for the clarification. Is this an actual problem though? Do we
> > have any consumers of the functionality?
> > 
> 
> I don't know, that's why I was being careful in not changing its behavior.

Can we simply go with pfn_to_online_page. I would be quite surprised if
anybody was really examining zone device memory ranges as they are
static IIUC. If there is some usecase I am pretty sure we will learn
that and can address it accordingly.
-- 
Michal Hocko
SUSE Labs