Vlastimil Babka <vba...@suse.cz> writes:
> On 10/11/2017 08:51 AM, Michal Hocko wrote:
>> On Wed 11-10-17 13:37:50, Michael Ellerman wrote:
>>> Michal Hocko <mho...@kernel.org> writes:
>>>> On Tue 10-10-17 23:05:08, Michael Ellerman wrote:
>>>>> Michal Hocko <mho...@kernel.org> writes:
>>>>>> From: Michal Hocko <mho...@suse.com>
>>>>>>
>>>>>> Memory offlining can fail just too eagerly under a heavy memory pressure.
...
>>>>>
>>>>> This breaks offline for me.
>>>>>
>>>>> Prior to this commit:
>>>>> /sys/devices/system/memory/memory0# time echo 0 > online
>>>>> -bash: echo: write error: Device or resource busy
>
> Well, that means offline didn't actually work for that block even before
> this patch, right? Is it even a movable_node block? I guess not?
Correct. It should fail.
>>>>> After:
>>>>> /sys/devices/system/memory/memory0# time echo 0 > online
>>>>> -bash: echo: write error: Device or resource busy
>>>>>
>>>>> real 2m0.009s
>>>>> user 0m0.000s
>>>>> sys 1m25.035s
>>>>>
>>>>> There's no way that block can be removed, it contains the kernel text,
>>>>> so it should instantly fail - which it used to.
>
> Ah, right. So your complain is really about that the failure is not
> instant anymore for blocks that can't be offlined.
Yes. Previously it failed instantly, now it doesn't fail, and loops
infinitely (once the 2 minute limit is removed).
>> This is really strange! As you write in other email the page is
>> reserved. That means that some of the earlier checks
>> if (zone_idx(zone) == ZONE_MOVABLE)
>> return false;
>> mt = get_pageblock_migratetype(page);
>> if (mt == MIGRATE_MOVABLE || is_migrate_cma(mt))
>
> The MIGRATE_MOVABLE check is indeed bogus, because that doesn't
> guarantee there are no unmovable pages in the block (CMA block OTOH
> should be a guarantee).
OK I'll try that and get back to you.
cheers
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 3badcedf96a7..5b4d85ae445c 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -7355,9 +7355,6 @@ bool has_unmovable_pages(struct zone *zone, struct
>> page *page, int count,
>> */
>> if (zone_idx(zone) == ZONE_MOVABLE)
>> return false;
>> - mt = get_pageblock_migratetype(page);
>> - if (mt == MIGRATE_MOVABLE || is_migrate_cma(mt))
>> - return false;
>>
>> pfn = page_to_pfn(page);
>> for (found = 0, iter = 0; iter < pageblock_nr_pages; iter++) {
>> @@ -7368,6 +7365,9 @@ bool has_unmovable_pages(struct zone *zone, struct
>> page *page, int count,
>>
>> page = pfn_to_page(check);
>>
>> + if (PageReserved(page))
>> + return true;
>> +
>> /*
>> * Hugepages are not in LRU lists, but they're movable.
>> * We need not scan over tail pages bacause we don't
>>
