Re: [PATCH] mm: remove migration for HugePage in isolate_single_pageblock()

[Kefeng Wang <wangkefeng.wang@huawei.com>]

On 2024/8/16 12:58, Andrew Morton wrote:
> On Fri, 16 Aug 2024 12:06:25 +0800 Kefeng Wang <wangkefeng.wang@huawei.com> wrote:
> 
>> The gigantic page size may larger than memory block size, so memory
>> offline always fails in this case after commit b2c9e2fbba32 ("mm: make
>> alloc_contig_range work at pageblock granularity"),
>>
>> offline_pages
>>    start_isolate_page_range
>>      start_isolate_page_range(isolate_before=true)
>>        isolate [isolate_start, isolate_start + pageblock_nr_pages)
>>      start_isolate_page_range(isolate_before=false)
>>        isolate [isolate_end - pageblock_nr_pages, isolate_end) pageblock
>>         	__alloc_contig_migrate_range
>>            isolate_migratepages_range
>>              isolate_migratepages_block
>>                isolate_or_dissolve_huge_page
>>                  if (hstate_is_gigantic(h))
>>                      return -ENOMEM;
>>
>> In fact, we don't need to migrate page in page range isolation, for
>> memory offline path, there is do_migrate_range() to move the pages.
>> For contig allocation, there is another __alloc_contig_migrate_range()
>> after isolation to migrate the pages. So fix issue by skipping the
>> __alloc_contig_migrate_range() in isolate_single_pageblock().
>>
>> Fixes: b2c9e2fbba32 ("mm: make alloc_contig_range work at pageblock granularity")
> 
> Should we backport this into -stable kernels?

Better to backport to stable since memory offline always fail in this case.

>