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

[David Hildenbrand <david@redhat.com>]

On 30.05.25 22:46, Zi Yan wrote:
> On 30 May 2025, at 16:08, David Hildenbrand wrote:
> 
>> On 30.05.25 21:58, Zi Yan wrote:
>>> 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@nvidia.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.
>>
>> Could we abstract both settings and use a single one? Then, we could simply reject if MEM_OFFLINE is passed into alloc_contig_range().
>>
>> alloc_contig_pages and page isolation, hmmmm, MEM_OFFLINE is kind-of an allocation. CMA is an allocation.
>>
>> Just an idea, not sure ...
> 
> I think so.
> 
> This is the fixup of removing acr_flags_t. It is on top of the original
> patch. Take your time. I guess I will send V7 with all fixups next week.

Only wondering if we should rename "pb_isolate_mode" to something more 
abstract, that covers both use cases clearer.

Hmmm.

> 
> The one strange part is that in virtio_mem_fake_offline,
> PB_ISOLATE_MODE_OTHER is used instead of PB_ISOLATE_MODE_MEM_OFFLINE.
> I guess you do not want to report failures there.

That's the right thing to do. It's not ordinary memory offlining code.

Thanks and enjoy the weekend!

-- 
Cheers,

David / dhildenb