Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Wed, 5 May 2021 15:13:11 +0200
From:   Michal Hocko <mhocko@suse.com>
To:     David Hildenbrand <david@redhat.com>
Cc:     linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Mike Rapoport <rppt@kernel.org>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        Oscar Salvador <osalvador@suse.de>,
        Roman Gushchin <guro@fb.com>,
        Alex Shi <alex.shi@linux.alibaba.com>,
        Steven Price <steven.price@arm.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Aili Yao <yaoaili@kingsoft.com>, Jiri Bohac <jbohac@suse.cz>,
        "K. Y. Srinivasan" <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Wei Liu <wei.liu@kernel.org>,
        Naoya Horiguchi <naoya.horiguchi@nec.com>,
        linux-hyperv@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH v1 3/7] mm: rename and move page_is_poisoned()
Message-ID: <YJKZ5yXdl18m9YSM@dhcp22.suse.cz>
References: <20210429122519.15183-1-david@redhat.com>
 <20210429122519.15183-4-david@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20210429122519.15183-4-david@redhat.com>
Precedence: bulk

On Thu 29-04-21 14:25:15, David Hildenbrand wrote:
> Commit d3378e86d182 ("mm/gup: check page posion status for coredump.")
> introduced page_is_poisoned(), however, v5 [1] of the patch used
> "page_is_hwpoison()" and something went wrong while upstreaming. Rename the
> function and move it to page-flags.h, from where it can be used in other
> -- kcore -- context.
> 
> Move the comment to the place where it belongs and simplify.
> 
> [1] https://lkml.kernel.org/r/20210322193318.377c9ce9@alex-virtual-machine
> 
> Signed-off-by: David Hildenbrand <david@redhat.com>

I do agree that being explicit about hwpoison is much better. Poisoned
page can be also an unitialized one and I believe this is the reason why
you are bringing that up.

But you've made me look at d3378e86d182 and I am wondering whether this
is really a valid patch. First of all it can leak a reference count
AFAICS. Moreover it doesn't really fix anything because the page can be
marked hwpoison right after the check is done. I do not think the race
is feasible to be closed. So shouldn't we rather revert it?

-- 
Michal Hocko
SUSE Labs