Re: [RFC PATCH 4/4] mm/page_isolation: remove migratetype parameter from more functions.

[Zi Yan <ziy@nvidia.com>]

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On 2 Sep 2024, at 5:06, David Hildenbrand wrote:

> On 28.08.24 22:22, Zi Yan wrote:
>> migratetype is no longer overwritten during pageblock isolation,
>> start_isolate_page_range(), has_unmovable_pages(), and
>> set_migratetype_isolate() no longer need which migratetype to restore
>> during isolation failure. For has_unmoable_pages(), it needs to know if
>> the isolation is for CMA allocation, so adding CMA_ALLOCATION to isolation
>> flags to provide the information.
>>
>> Signed-off-by: Zi Yan <ziy@nvidia.com>
>> ---
>>   include/linux/page-isolation.h |  3 ++-
>>   mm/memory_hotplug.c            |  1 -
>>   mm/page_alloc.c                |  4 +++-
>>   mm/page_isolation.c            | 27 +++++++++++----------------
>>   4 files changed, 16 insertions(+), 19 deletions(-)
>>
>> diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h
>> index c2a1bd621561..e94117101b6c 100644
>> --- a/include/linux/page-isolation.h
>> +++ b/include/linux/page-isolation.h
>> @@ -32,13 +32,14 @@ static inline bool is_migrate_isolate(int migratetype)
>>    #define MEMORY_OFFLINE	0x1
>>   #define REPORT_FAILURE	0x2
>> +#define CMA_ALLOCATION	0x4
>>    void set_pageblock_migratetype(struct page *page, int migratetype);
>>    bool move_freepages_block_isolate(struct zone *zone, struct page *page);
>>    int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
>> -			     int migratetype, int flags, gfp_t gfp_flags);
>> +			     int flags, gfp_t gfp_flags);
>>    void undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn);
>>  diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index 4265272faf4c..fe0b71e0f307 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -1993,7 +1993,6 @@ int offline_pages(unsigned long start_pfn, unsigned long nr_pages,
>>    	/* set above range as isolated */
>>   	ret = start_isolate_page_range(start_pfn, end_pfn,
>> -				       MIGRATE_MOVABLE,
>>   				       MEMORY_OFFLINE | REPORT_FAILURE,
>>   				       GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL);
>>   	if (ret) {
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 4d06932ba69a..c60bb95d7e65 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -6607,7 +6607,9 @@ int alloc_contig_range_noprof(unsigned long start, unsigned long end,
>>   	 * put back to page allocator so that buddy can use them.
>>   	 */
>>  -	ret = start_isolate_page_range(start, end, migratetype, 0, gfp_mask);
>> +	ret = start_isolate_page_range(start, end,
>> +			migratetype == MIGRATE_CMA ? CMA_ALLOCATION : 0,
>
> Can we have flags for alloc_contig_range() instead of passing in a (weird) migratetype?
>
> Then, we should make sure that we warn if we try a CMA allocation on any pageblock that is not of type CMA.

Sure. I will expose the existing isolation flags (MEMORY_OFFLINE, REPORT_FAILURE,
and CMA_ALLOCATION) as alloc_contig_range() parameter to replace migratetype one.

>
> I'm trying to remember what happens if we try offlining a memory region that is of type MIGRATE_CMA right now ... I remember that we fail it. We should make sure that is still the case, otherwise we could seriously break something.

Yes, that fails. That is why I added CMA_ALLOCATION, which is used in
has_unmovable_pages() for this situation.


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Best Regards,
Yan, Zi

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