From: David Hildenbrand <david@redhat.com>
To: Michal Hocko <mhocko@suse.com>, Pingfan Liu <kernelfans@gmail.com>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Dan Williams <dan.j.williams@intel.com>,
Oscar Salvador <osalvador@suse.de>, Baoquan He <bhe@redhat.com>,
Qian Cai <cai@lca.pw>,
kexec@lists.infradead.org, Kazuhito Hagio <k-hagio@ab.jp.nec.com>
Subject: Re: [PATCHv2] mm/sparse: reset section's mem_map when fully deactivated
Date: Mon, 20 Jan 2020 10:03:44 +0100 [thread overview]
Message-ID: <ee0f02ca-9710-eef0-00c1-4e08c049473a@redhat.com> (raw)
In-Reply-To: <20200120072939.GD18451@dhcp22.suse.cz>
On 20.01.20 08:29, Michal Hocko wrote:
> On Mon 20-01-20 10:33:14, Pingfan Liu wrote:
>> After commit ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug"),
>> when a mem section is fully deactivated, section_mem_map still records the
>> section's start pfn, which is not used any more and will be reassigned
>> during re-added.
>>
>> In analogy with alloc/free pattern, it is better to clear all fields of
>> section_mem_map.
>>
>> Beside this, it breaks the user space tool "makedumpfile" [1], which makes
>> assumption that a hot-removed section has mem_map as NULL, instead of
>> checking directly against SECTION_MARKED_PRESENT bit. (makedumpfile will be
>> better to change the assumption, and need a patch)
>>
>> The bug can be reproduced on IBM POWERVM by "drmgr -c mem -r -q 5" ,
>> trigger a crash, and save vmcore by makedumpfile
>
> While makedumpfile lives very closely to the kernel and occasional
> breakage is to be expected I still believe that Fixes: ba72b4c8cf60
> is due.
+1 as I expressed earlier.
>
>> [1]: makedumpfile, commit e73016540293 ("[v1.6.7] Update version")
>>
>> Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
>> To: linux-mm@kvack.org
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: David Hildenbrand <david@redhat.com>
>> Cc: Dan Williams <dan.j.williams@intel.com>
>> Cc: Oscar Salvador <osalvador@suse.de>
>> Cc: Michal Hocko <mhocko@kernel.org>
>> Cc: Baoquan He <bhe@redhat.com>
>> Cc: Qian Cai <cai@lca.pw>
>> Cc: kexec@lists.infradead.org
>> Cc: Kazuhito Hagio <k-hagio@ab.jp.nec.com>
>
I think you dropped my
Acked-by: David Hildenbrand <david@redhat.com>
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2020-01-20 9:03 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-20 2:33 Pingfan Liu
2020-01-20 7:29 ` Michal Hocko
2020-01-20 9:03 ` David Hildenbrand [this message]
2020-01-20 10:12 ` Pingfan Liu
2020-01-24 3:10 ` Andrew Morton
2020-01-24 6:49 ` Michal Hocko
2020-01-25 13:26 ` Pingfan Liu
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