linux-kernel - Re: [PATCH v5 6/6] mm/page_isolation: remove migratetype parameter from more functions.

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Message-ID: <B4F06FA4-AEC0-4B2C-AB1C-FA404A81CD9C@nvidia.com>
Date: Tue, 27 May 2025 11:04:24 -0400
From: Zi Yan <ziy@...dia.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: David Hildenbrand <david@...hat.com>,
 Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org,
 Andrew Morton <akpm@...ux-foundation.org>,
 Oscar Salvador <osalvador@...e.de>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>,
 "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
 Mel Gorman <mgorman@...hsingularity.net>,
 Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
 Brendan Jackman <jackmanb@...gle.com>, Richard Chang <richardycc@...gle.com>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 6/6] mm/page_isolation: remove migratetype parameter
 from more functions.

On 27 May 2025, at 8:55, Vlastimil Babka wrote:

> On 5/23/25 21:12, 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 provide the information. At the
>> same time change isolation flags to enum pb_isolate_mode (MEMORY_OFFLINE,
>> CMA_ALLOCATION, and ISOLATE_MODE_OTHERS). Remove REPORT_FAILURE and check
>> MEMORY_OFFLINE instead, since only MEMORY_OFFLINE reports isolation
>> failures.
>>
>> alloc_contig_range() no longer needs migratetype. Replace it with
>> a newly defined acr_flags_t to tell if an allocation is for CMA. So does
>> __alloc_contig_migrate_range().
>>
>> Signed-off-by: Zi Yan <ziy@...dia.com>
>> ---
>>  drivers/virtio/virtio_mem.c    |  3 +-
>>  include/linux/gfp.h            |  6 ++-
>>  include/linux/page-isolation.h | 19 ++++++++--
>>  include/trace/events/kmem.h    | 14 ++++---
>>  mm/cma.c                       |  2 +-
>>  mm/memory_hotplug.c            |  4 +-
>>  mm/page_alloc.c                | 25 ++++++-------
>>  mm/page_isolation.c            | 67 +++++++++++++++-------------------
>>  8 files changed, 72 insertions(+), 68 deletions(-)
>>
>> diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
>> index 56d0dbe62163..8accc0f255a8 100644
>> --- a/drivers/virtio/virtio_mem.c
>> +++ b/drivers/virtio/virtio_mem.c
>> @@ -1243,8 +1243,7 @@ static int virtio_mem_fake_offline(struct virtio_mem *vm, unsigned long pfn,
>>  		if (atomic_read(&vm->config_changed))
>>  			return -EAGAIN;
>>
>> -		rc = alloc_contig_range(pfn, pfn + nr_pages, MIGRATE_MOVABLE,
>> -					GFP_KERNEL);
>> +		rc = alloc_contig_range(pfn, pfn + nr_pages, 0, GFP_KERNEL);
>>  		if (rc == -ENOMEM)
>>  			/* whoops, out of memory */
>>  			return rc;
>> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
>> index be160e8d8bcb..dea27ed24f8e 100644
>> --- a/include/linux/gfp.h
>> +++ b/include/linux/gfp.h
>> @@ -423,9 +423,13 @@ static inline bool gfp_compaction_allowed(gfp_t gfp_mask)
>>  extern gfp_t vma_thp_gfp_mask(struct vm_area_struct *vma);
>>
>>  #ifdef CONFIG_CONTIG_ALLOC
>> +
>> +typedef unsigned int __bitwise acr_flags_t;
>> +#define ACR_CMA		((__force acr_flags_t)BIT(0))	// allocate for CMA
>
> Would it make sense to define ACR_NONE as 0 so it's more descriptive than
> seeing 0 somewhere?

Totally. Will add one.

>
>> +
>>  /* The below functions must be run on a range from a single zone. */
>>  extern int alloc_contig_range_noprof(unsigned long start, unsigned long end,
>> -			      unsigned migratetype, gfp_t gfp_mask);
>> +			      acr_flags_t alloc_flags, gfp_t gfp_mask);
>>  #define alloc_contig_range(...)			alloc_hooks(alloc_contig_range_noprof(__VA_ARGS__))
>>
>>  extern struct page *alloc_contig_pages_noprof(unsigned long nr_pages, gfp_t gfp_mask,
>> diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h
>> index 7a681a49e73c..b61bca909ddc 100644
>> --- a/include/linux/page-isolation.h
>> +++ b/include/linux/page-isolation.h
>> @@ -38,8 +38,19 @@ static inline void set_pageblock_isolate(struct page *page)
>>  }
>>  #endif
>>
>> -#define MEMORY_OFFLINE	0x1
>> -#define REPORT_FAILURE	0x2
>> +/*
>> + * Pageblock isolation modes:
>> + * MEMORY_OFFLINE      - isolate to offline (!allocate) memory e.g., skip over
>> + *		         PageHWPoison() pages and PageOffline() pages.
>> + *		         Unmovable pages will be reported in this mode.
>> + * CMA_ALLOCATION      - isolate for CMA allocations
>> + * ISOLATE_MODE_OTHERS - isolate for other purposes
>> + */
>> +enum pb_isolate_mode {
>> +	MEMORY_OFFLINE,
>> +	CMA_ALLOCATION,
>> +	ISOLATE_MODE_OTHERS,
>
> Since this is in a .h file, I'd prefer more consistent naming, and longer
> names shouldn't hurt as there are not that many users.
>
> Even something like:
> PB_ISOLATE_MODE_OFFLINE
> PB_ISOLATE_MODE_CMA
> PB_ISOLATE_MODE_OTHER
>
> ?

OK. I am going to use more descriptive names below:

PB_ISOLATE_MODE_MEM_OFFLINE
PB_ISOLATE_MODE_CMA_ALLOC
PB_ISOLATE_MODE_OTHER

Thank you for all the suggestions and reviews. :)


Best Regards,
Yan, Zi