linux-kernel - Re: [PATCH v1 3/7] mm: rename and move page_is

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Date:   Wed, 5 May 2021 15:45:47 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Mike Rapoport <rppt@...nel.org>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Oscar Salvador <osalvador@...e.de>,
        Roman Gushchin <guro@...com>,
        Alex Shi <alex.shi@...ux.alibaba.com>,
        Steven Price <steven.price@....com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Aili Yao <yaoaili@...gsoft.com>, Jiri Bohac <jbohac@...e.cz>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        linux-hyperv@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v1 3/7] mm: rename and move page_is_poisoned()

On Wed 05-05-21 15:39:08, David Hildenbrand wrote:
> > > Long story short, this should be good enough for the cases we actually can
> > > handle? What am I missing?
> > 
> > I am not sure I follow. My point is that I fail to see any added value
> > of the check as it doesn't prevent the race (it fundamentally cannot as
> > the page can be poisoned at any time) but the failure path doesn't
> > put_page which is incorrect even for hwpoison pages.
> 
> Oh, I think you are right. If we have a page and return NULL we would leak a
> reference.
> 
> Actually, we discussed in that thread handling this entirely differently,
> which resulted in a v7 [1]; however Andrew moved forward with this
> (outdated?) patch, maybe that was just a mistake?
> 
> Yes, I agree we should revert that patch for now.

OK, Let me send the revert to Andrew.

-- 
Michal Hocko
SUSE Labs