linux-kernel - Re: [RFC PATCH v2 2/8] migrate: implement migrate_misplaced_folios

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Message-ID: <66b9c552-61f6-46b3-a773-87958429322f@amd.com>
Date: Fri, 3 Oct 2025 16:32:12 +0530
From: Bharata B Rao <bharata@....com>
To: Jonathan Cameron <jonathan.cameron@...wei.com>
CC: <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
	<dave.hansen@...el.com>, <gourry@...rry.net>, <hannes@...xchg.org>,
	<mgorman@...hsingularity.net>, <mingo@...hat.com>, <peterz@...radead.org>,
	<raghavendra.kt@....com>, <riel@...riel.com>, <rientjes@...gle.com>,
	<sj@...nel.org>, <weixugc@...gle.com>, <willy@...radead.org>,
	<ying.huang@...ux.alibaba.com>, <ziy@...dia.com>, <dave@...olabs.net>,
	<nifan.cxl@...il.com>, <xuezhengchu@...wei.com>, <yiannis@...corp.com>,
	<akpm@...ux-foundation.org>, <david@...hat.com>, <byungchul@...com>,
	<kinseyho@...gle.com>, <joshua.hahnjy@...il.com>, <yuanchu@...gle.com>,
	<balbirs@...dia.com>, <alok.rathore@...sung.com>
Subject: Re: [RFC PATCH v2 2/8] migrate: implement
 migrate_misplaced_folios_batch

On 03-Oct-25 4:06 PM, Jonathan Cameron wrote:
> On Wed, 10 Sep 2025 20:16:47 +0530
> Bharata B Rao <bharata@....com> wrote:
> 
>> From: Gregory Price <gourry@...rry.net>
>>
>> A common operation in tiering is to migrate multiple pages at once.
>> The migrate_misplaced_folio function requires one call for each
>> individual folio.  Expose a batch-variant of the same call for use
>> when doing batch migrations.
>>
> I probably missed an earlier discussion of this but what does the
> _batch postfix add over the plural (folios)?

https://lore.kernel.org/linux-mm/15744682-72ea-472f-9af1-50c3494c0b78@redhat.com/

> 
>> Signed-off-by: Gregory Price <gourry@...rry.net>
>> Signed-off-by: Bharata B Rao <bharata@....com>
>> ---
>>  include/linux/migrate.h |  6 ++++++
>>  mm/migrate.c            | 31 +++++++++++++++++++++++++++++++
>>  2 files changed, 37 insertions(+)
>>
>> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
>> index acadd41e0b5c..0593f5869be8 100644
>> --- a/include/linux/migrate.h
>> +++ b/include/linux/migrate.h
>> @@ -107,6 +107,7 @@ static inline int migrate_huge_page_move_mapping(struct address_space *mapping,
>>  int migrate_misplaced_folio_prepare(struct folio *folio,
>>  		struct vm_area_struct *vma, int node);
>>  int migrate_misplaced_folio(struct folio *folio, int node);
>> +int migrate_misplaced_folios_batch(struct list_head *foliolist, int node);
>>  #else
>>  static inline int migrate_misplaced_folio_prepare(struct folio *folio,
>>  		struct vm_area_struct *vma, int node)
>> @@ -117,6 +118,11 @@ static inline int migrate_misplaced_folio(struct folio *folio, int node)
>>  {
>>  	return -EAGAIN; /* can't migrate now */
>>  }
>> +static inline int migrate_misplaced_folios_batch(struct list_head *foliolist,
>> +						 int node)
>> +{
>> +	return -EAGAIN; /* can't migrate now */
>> +}
>>  #endif /* CONFIG_NUMA_BALANCING */
>>  
>>  #ifdef CONFIG_MIGRATION
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index 7e356c0b1b5a..1268a95eda0e 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -2714,5 +2714,36 @@ int migrate_misplaced_folio(struct folio *folio, int node)
>>  	BUG_ON(!list_empty(&migratepages));
>>  	return nr_remaining ? -EAGAIN : 0;
>>  }
>> +
>> +/*
> 
> Kernel-doc perhaps appropriate?

Probably yes, will take care in next iteration.

Thanks for looking into this patchset.

Regards,
Bharata.