From: Michal Hocko <mhocko@kernel.org>
To: David Hildenbrand <david@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
virtualization@lists.linux-foundation.org,
Andrea Arcangeli <aarcange@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Juergen Gross <jgross@suse.com>,
Pavel Tatashin <pavel.tatashin@microsoft.com>,
Alexander Duyck <alexander.h.duyck@linux.intel.com>,
Anthony Yznaga <anthony.yznaga@oracle.com>,
Vlastimil Babka <vbabka@suse.cz>,
Johannes Weiner <hannes@cmpxchg.org>,
Oscar Salvador <osalvador@suse.de>,
Pingfan Liu <kernelfans@gmail.com>, Qian Cai <cai@lca.pw>,
Dan Williams <dan.j.williams@intel.com>,
Mel Gorman <mgorman@techsingularity.net>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
Wei Yang <richardw.yang@linux.intel.com>,
Alexander Potapenko <glider@google.com>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Jason Gunthorpe <jgg@ziepe.ca>,
Stephen Rothwell <sfr@canb.auug.org.au>,
Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
Matthew Wilcox <willy@infradead.org>, Yu Zhao <yuzhao@google.com>,
Minchan Kim <minchan@kernel.org>,
Yang Shi <yang.shi@linux.alibaba.com>,
Ira Weiny <ira.weiny@intel.com>,
Andrey Ryabinin <aryabinin@virtuozzo.com>
Subject: Re: [PATCH RFC v3 6/9] mm: Allow to offline PageOffline() pages with a reference count of 0
Date: Wed, 16 Oct 2019 16:09:58 +0200 [thread overview]
Message-ID: <20191016140958.GE317@dhcp22.suse.cz> (raw)
In-Reply-To: <2aef8477-7d12-63a8-e273-9eae8712d5c2@redhat.com>
On Wed 16-10-19 15:55:00, David Hildenbrand wrote:
> On 16.10.19 15:45, Michal Hocko wrote:
[...]
> > There is state stored in the struct page. In other words this shouldn't
> > be really different from HWPoison pages. I cannot find the code that is
> > doing that and maybe we don't handle that. But we cannot simply online
> > hwpoisoned page. Offlining the range will not make a broken memory OK
> > all of the sudden. And your usecase sounds similar to me.
>
> Sorry to say, but whenever we online memory the memmap is overwritten,
> because there is no way you could tell it contains garbage or not. You have
> to assume it is garbage. (my recent patch even poisons the memmap when
> offlining, which helped to find a lot of these "garbage memmap" BUGs)
>
> online_pages()
> ...
> move_pfn_range_to_zone(zone, pfn, nr_pages, NULL);
> ...
> memmap_init_zone()
> -> memmap initialized
>
> So yes, offlining memory with HWPoison and re-onlining it effectively drops
> HWPoison markers. On the next access, you will trigger a new HWPoison.
Right you are! I need to sit on this much more and think about it with a
clean head.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-10-16 14:10 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-19 14:22 [PATCH RFC v3 0/9] virtio-mem: paravirtualized memory David Hildenbrand
2019-09-19 14:22 ` [PATCH RFC v3 1/9] ACPI: NUMA: export pxm_to_node David Hildenbrand
2019-09-23 10:13 ` David Hildenbrand
2019-09-23 10:36 ` Michal Hocko
2019-09-23 10:39 ` David Hildenbrand
2019-09-19 14:22 ` [PATCH RFC v3 2/9] virtio-mem: Paravirtualized memory hotplug David Hildenbrand
2019-09-19 14:22 ` [PATCH RFC v3 3/9] virtio-mem: Paravirtualized memory hotunplug part 1 David Hildenbrand
2019-09-19 14:22 ` [PATCH RFC v3 4/9] mm: Export alloc_contig_range() / free_contig_range() David Hildenbrand
2019-10-16 11:20 ` Michal Hocko
2019-10-16 12:31 ` David Hildenbrand
2019-09-19 14:22 ` [PATCH RFC v3 5/9] virtio-mem: Paravirtualized memory hotunplug part 2 David Hildenbrand
2019-09-19 14:22 ` [PATCH RFC v3 6/9] mm: Allow to offline PageOffline() pages with a reference count of 0 David Hildenbrand
2019-10-16 11:43 ` Michal Hocko
2019-10-16 12:50 ` David Hildenbrand
2019-10-16 13:45 ` Michal Hocko
2019-10-16 13:55 ` David Hildenbrand
2019-10-16 14:09 ` Michal Hocko [this message]
2019-10-16 14:16 ` David Hildenbrand
2019-10-16 13:59 ` David Hildenbrand
2019-10-16 13:45 ` David Hildenbrand
2019-10-16 14:03 ` Michal Hocko
2019-10-16 14:14 ` David Hildenbrand
2019-10-18 8:15 ` Michal Hocko
2019-10-18 8:50 ` David Hildenbrand
2019-10-18 11:20 ` Michal Hocko
2019-10-18 12:35 ` David Hildenbrand
2019-10-22 12:23 ` Michal Hocko
2019-10-22 14:02 ` David Hildenbrand
2019-10-23 9:43 ` Michal Hocko
2019-10-23 10:03 ` David Hildenbrand
2019-10-24 8:42 ` Michal Hocko
2019-10-24 8:51 ` David Hildenbrand
2019-10-25 11:28 ` [PATCH RFC] mm: Allow to offline unmovable PageOffline() pages if the driver agrees David Hildenbrand
2019-09-19 14:22 ` [PATCH RFC v3 7/9] virtio-mem: Allow to offline partially unplugged memory blocks David Hildenbrand
2019-09-19 14:22 ` [PATCH RFC v3 8/9] mm/memory_hotplug: Introduce offline_and_remove_memory() David Hildenbrand
2019-10-16 11:47 ` Michal Hocko
2019-10-16 12:57 ` David Hildenbrand
2019-09-19 14:22 ` [PATCH RFC v3 9/9] virtio-mem: Offline and remove completely unplugged memory blocks David Hildenbrand
2019-10-16 8:12 ` [PATCH RFC v3 0/9] virtio-mem: paravirtualized memory David Hildenbrand
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