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@xxxxxxxxx>
>> To: linux-mm@xxxxxxxxx
>> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>> Cc: David Hildenbrand <david@xxxxxxxxxx>
>> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
>> Cc: Oscar Salvador <osalvador@xxxxxxx>
>> Cc: Michal Hocko <mhocko@xxxxxxxxxx>
>> Cc: Baoquan He <bhe@xxxxxxxxxx>
>> Cc: Qian Cai <cai@xxxxxx>
>> Cc: kexec@xxxxxxxxxxxxxxxxxxx
>> Cc: Kazuhito Hagio <k-hagio@xxxxxxxxxxxxx>
>
I think you dropped my
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
--
Thanks,
David / dhildenb
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