linux-kernel - Re: [PATCH v6 6/6] mm/page_isolation: remove migratetype parameter from more functions.

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Message-ID: <8C1EFB3C-0F1C-46DE-878A-3546A86A141F@nvidia.com>
Date: Fri, 30 May 2025 15:58:42 -0400
From: Zi Yan <ziy@...dia.com>
To: David Hildenbrand <david@...hat.com>
Cc: Johannes Weiner <hannes@...xchg.org>, Vlastimil Babka <vbabka@...e.cz>,
 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 v6 6/6] mm/page_isolation: remove migratetype parameter
 from more functions.

On 30 May 2025, at 15:56, David Hildenbrand wrote:

> On 30.05.25 18:22, 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 provide the information. At the
>> same time change isolation flags to enum pb_isolate_mode
>> (PB_ISOLATE_MODE_MEM_OFFLINE, PB_ISOLATE_MODE_CMA_ALLOC,
>> PB_ISOLATE_MODE_OTHER). Remove REPORT_FAILURE and check
>> MEMORY_OFFLINE instead, since only PB_ISOLATE_MODE_MEM_OFFLINE reports
>> isolation failures.
>>
>> alloc_contig_range() no longer needs migratetype. Replace it with
>> enum 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    |  2 +-
>>   include/linux/gfp.h            |  9 ++++-
>>   include/linux/page-isolation.h | 20 ++++++++--
>>   include/trace/events/kmem.h    | 14 ++++---
>>   mm/cma.c                       |  2 +-
>>   mm/memory_hotplug.c            |  6 +--
>>   mm/page_alloc.c                | 27 ++++++-------
>>   mm/page_isolation.c            | 70 +++++++++++++++-------------------
>>   8 files changed, 82 insertions(+), 68 deletions(-)
>>
>> diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
>> index 56d0dbe62163..6bce70b139b2 100644
>> --- a/drivers/virtio/virtio_mem.c
>> +++ b/drivers/virtio/virtio_mem.c
>> @@ -1243,7 +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,
>> +		rc = alloc_contig_range(pfn, pfn + nr_pages, ACR_OTHER,
>>   					GFP_KERNEL);
>>   		if (rc == -ENOMEM)
>>   			/* whoops, out of memory */
>> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
>> index be160e8d8bcb..51990d571e3e 100644
>> --- a/include/linux/gfp.h
>> +++ b/include/linux/gfp.h
>> @@ -423,9 +423,16 @@ 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
>> +
>> +enum acr_flags_t {
>> +	ACR_CMA,	// CMA allocation
>> +	ACR_OTHER,	// other allocation
>> +};
>
> Hm, enum != flags.
>
> If you want to use flags, then just have ACR_CMA. ACR_OTHER is implied if not set.
>
> And ACR_CMA would then have to be "1" etc.

I have a fixup to change acr_flags_t to acr_mode.

>
>> +
>>   /* 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);
>> +				     enum 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..3e2f960e166c 100644
>> --- a/include/linux/page-isolation.h
>> +++ b/include/linux/page-isolation.h
>> @@ -38,8 +38,20 @@ static inline void set_pageblock_isolate(struct page *page)
>>   }
>>   #endif
>>  -#define MEMORY_OFFLINE	0x1
>> -#define REPORT_FAILURE	0x2
>> +/*
>> + * Pageblock isolation modes:
>> + * PB_ISOLATE_MODE_MEM_OFFLINE - isolate to offline (!allocate) memory
>> + *				 e.g., skip over PageHWPoison() pages and
>> + *				 PageOffline() pages. Unmovable pages will be
>> + *				 reported in this mode.
>> + * PB_ISOLATE_MODE_CMA_ALLOC   - isolate for CMA allocations
>> + * PB_ISOLATE_MODE_OTHER       - isolate for other purposes
>> + */
>> +enum pb_isolate_mode {
>> +	PB_ISOLATE_MODE_MEM_OFFLINE,
>> +	PB_ISOLATE_MODE_CMA_ALLOC,
>> +	PB_ISOLATE_MODE_OTHER,
>> +};
>
> It's late on friady, but it looks like we are duplicating things here.
>
> Let me think about that once my brain is recharged :)

Sure. Take your time.

Best Regards,
Yan, Zi