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From: David Hildenbrand <david@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org,
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	Dan Williams <dan.j.williams@intel.com>,
	Wei Yang <richard.weiyang@gmail.com>, Qian Cai <cai@lca.pw>,
	Jason Gunthorpe <jgg@ziepe.ca>,
	Logan Gunthorpe <logang@deltatee.com>,
	Ira Weiny <ira.weiny@intel.com>
Subject: Re: [PATCH v6 05/10] mm/memory_hotplug: Shrink zones when offlining memory
Date: Wed, 18 Dec 2019 18:08:04 +0100
Message-ID: <4a3d7420-2d11-a37c-0e82-2096fbf7bca6@redhat.com> (raw)
In-Reply-To: <20191130152159.258fa331542fc693e24723eb@linux-foundation.org>

On 01.12.19 00:21, Andrew Morton wrote:
> On Sun, 27 Oct 2019 23:45:52 +0100 David Hildenbrand <david@redhat.com> wrote:
> 
>> I think I just found an issue with try_offline_node(). 
>> try_offline_node() is pretty much broken already (touches garbage 
>> memmaps and will not considers mixed NIDs within sections), however, 
>> relies on the node span to look for memory sections to probe. So it 
>> seems to rely on the nodes getting shrunk when removing memory, not when 
>> offlining.
>>
>> As we shrink the node span when offlining now and not when removing, 
>> this can go wrong once we offline the last memory block of the node and 
>> offline the last CPU. We could still have memory around that we could 
>> re-online, however, the node would already be offline. Unlikely, but 
>> possible.
>>
>> Note that the same is also broken without this patch in case memory is 
>> never onlined. The "pfn_to_nid(pfn) != nid" can easily succeed on the 
>> garbage memmap, resulting in  no memory being detected as belonging to 
>> the node. Also, resize_pgdat_range() is called when onlining memory, not 
>> when adding it. :/ Oh this is so broken :)
>>
>> The right fix is probably to walk over all memory blocks that could 
>> exist and test if they belong to the nid (if offline, check the 
>> block->nid, if online check all pageblocks). A fix we can then move in 
>> front of this patch.
>>
>> Will look into this this week.
> 
> And this series shows almost no sign of having been reviewed.  I'll hold
> it over for 5.6.
> 

Hi Andrew, any chance we can get the (now at least reviewed - thx Oscar)
fix in patch #5 into 5.5? (I want to do the final stable backports for
the uninitialized memmap stuff)

-- 
Thanks,

David / dhildenb



  parent reply index

Thread overview: 75+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-06  8:56 [PATCH v6 00/10] mm/memory_hotplug: Shrink zones before removing memory David Hildenbrand
2019-10-06  8:56 ` [PATCH v6 01/10] mm/memunmap: Don't access uninitialized memmap in memunmap_pages() David Hildenbrand
2019-10-06 19:58   ` Damian Tometzki
2019-10-06 20:13     ` David Hildenbrand
2019-10-14  9:05   ` David Hildenbrand
2019-10-06  8:56 ` [PATCH v6 02/10] mm/memmap_init: Update variable name in memmap_init_zone David Hildenbrand
2019-10-06  8:56 ` [PATCH v6 03/10] mm/memory_hotplug: Don't access uninitialized memmaps in shrink_pgdat_span() David Hildenbrand
2019-10-14  9:31   ` David Hildenbrand
2019-10-06  8:56 ` [PATCH v6 04/10] mm/memory_hotplug: Don't access uninitialized memmaps in shrink_zone_span() David Hildenbrand
2019-10-14  9:32   ` David Hildenbrand
2019-10-14 19:17     ` Andrew Morton
2019-11-19 14:16       ` David Hildenbrand
2019-11-19 20:44         ` Andrew Morton
2019-10-06  8:56 ` [PATCH v6 05/10] mm/memory_hotplug: Shrink zones when offlining memory David Hildenbrand
2019-10-14  9:39   ` David Hildenbrand
2019-10-14 19:16     ` Andrew Morton
2019-10-27 22:45   ` David Hildenbrand
2019-11-30 23:21     ` Andrew Morton
2019-11-30 23:43       ` David Hildenbrand
2019-12-18 17:08       ` David Hildenbrand [this message]
2019-12-18 20:16         ` Andrew Morton
2019-12-03 15:10   ` Oscar Salvador
2019-12-03 15:27     ` David Hildenbrand
2019-10-06  8:56 ` [PATCH v6 06/10] mm/memory_hotplug: Poison memmap in remove_pfn_range_from_zone() David Hildenbrand
2019-10-16 14:01   ` David Hildenbrand
2020-02-04  8:59   ` Oscar Salvador
2019-10-06  8:56 ` [PATCH v6 07/10] mm/memory_hotplug: We always have a zone in find_(smallest|biggest)_section_pfn David Hildenbrand
2020-02-04  9:06   ` Oscar Salvador
2020-02-05  8:57   ` Wei Yang
2020-02-05  8:59     ` David Hildenbrand
2020-02-05  9:26       ` Wei Yang
2019-10-06  8:56 ` [PATCH v6 08/10] mm/memory_hotplug: Don't check for "all holes" in shrink_zone_span() David Hildenbrand
2020-02-04  9:13   ` Oscar Salvador
2020-02-04  9:20     ` David Hildenbrand
2020-02-04 14:25   ` Baoquan He
2020-02-04 14:42     ` David Hildenbrand
2020-02-05 12:43       ` Baoquan He
2020-02-05 13:20         ` David Hildenbrand
2020-02-05 13:34           ` Baoquan He
2020-02-05 13:38             ` David Hildenbrand
2020-02-05 14:12               ` Baoquan He
2020-02-05 14:16                 ` David Hildenbrand
2020-02-05 14:26                   ` Baoquan He
2020-02-05  9:59   ` Wei Yang
2020-02-05 14:48     ` Baoquan He
2020-02-05 22:56       ` Wei Yang
2020-02-05 23:08         ` Baoquan He
2020-02-05 23:26           ` Wei Yang
2020-02-05 23:30             ` Baoquan He
2020-02-05 23:34               ` Wei Yang
2020-02-05 14:54     ` David Laight
2020-02-05 14:55       ` David Hildenbrand
2019-10-06  8:56 ` [PATCH v6 09/10] mm/memory_hotplug: Drop local variables " David Hildenbrand
2020-02-04  9:26   ` Oscar Salvador
2020-02-04  9:29     ` David Hildenbrand
2020-02-05 10:07   ` Wei Yang
2019-10-06  8:56 ` [PATCH v6 10/10] mm/memory_hotplug: Cleanup __remove_pages() David Hildenbrand
2020-02-04  9:46   ` Oscar Salvador
2020-02-04 12:41     ` David Hildenbrand
2020-02-04 13:13       ` Segher Boessenkool
2020-02-04 13:38         ` David Hildenbrand
2020-02-05 12:51           ` Segher Boessenkool
2020-02-05 13:17             ` David Hildenbrand
2020-02-05 13:18               ` David Hildenbrand
2020-02-05 13:23                 ` David Hildenbrand
2020-02-05 11:48   ` Wei Yang
2019-12-02  9:09 ` [PATCH v6 00/10] mm/memory_hotplug: Shrink zones before removing memory David Hildenbrand
2019-12-03 13:36   ` Oscar Salvador
2020-01-31  4:40     ` Andrew Morton
2020-01-31  9:18       ` David Hildenbrand
2020-01-31 10:03         ` Michal Hocko
2020-01-31 10:36           ` David Hildenbrand
2020-02-04  1:46         ` Andrew Morton
2020-02-04  8:45           ` David Hildenbrand
2020-02-04  9:51             ` Oscar Salvador

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