On 2022/5/12 9:47, Rei Yamamoto wrote:
> On Wed, 11 May 2022 17:26:16 Miaohe Lin wrote:
>> On 2022/5/11 15:07, Rei Yamamoto wrote:
>>> On Wed, 11 May 2022 14:25:34 Miaohe Lin wrote:
>>>> On 2022/5/11 12:43, Rei Yamamoto wrote:
>>>>> Prevent returning a pfn outside the target zone in case that not
>>>>> aligned with pageblock boundary.
>>>>> Otherwise isolate_migratepages_block() would handle pages not in
>>>>> the target zone.
>>>>>
>>>>
>>>> IIUC, the sole caller isolate_migratepages will ensure the pfn won't outside
>>>> the target zone. So the below code change might not be necessary. Or am I miss
>>>> something ?
>>>
>>> While block_start_pfn is ensured, this variable is not used as the argument for
>>> isolate_migratepages_block():
>>> -----
>>> static isolate_migrate_t isolate_migratepages(struct compact_control *cc)
>>> {
>>> :
>>> low_pfn = fast_find_migrateblock(cc);
>>> block_start_pfn = pageblock_start_pfn(low_pfn);
>>> if (block_start_pfn < cc->zone->zone_start_pfn)
>>> block_start_pfn = cc->zone->zone_start_pfn; <--- block_start_pfn is ensured not outside
>>> the target zone
>>> :
>>> block_end_pfn = pageblock_end_pfn(low_pfn);
>>> :
>>> for (; block_end_pfn <= cc->free_pfn;
>>> fast_find_block = false,
>>> cc->migrate_pfn = low_pfn = block_end_pfn,
>>> block_start_pfn = block_end_pfn,
>>> block_end_pfn += pageblock_nr_pages) {
>>> :
>>> if (isolate_migratepages_block(cc, low_pfn, block_end_pfn, <--- low_pfn is passed as
>>> the argument
>>
>> Sorry, I think you're right. And could you please add the runtime effect of this issue?
>>
>> Anyway, this patch looks good to me now. Thanks!
>
> Thank you for your review.
> The runtime effect is that compaction become unintended behavior.
> For example, pages not in the target zone are added to cc->migratepages list in isolate_migratepages_block().
> As a result, pages migrate between nodes unintentionally.
Many thanks for clarifying. :) Is this worth a Fixes tag or even CC stable?
Thanks!
>
> Thanks,
> Rei
> .
>
