Re: [PATCH] mm/migrate: skip unsupported ZONE_DEVICE page in migrate_vma_collect_pmd()

[Miaohe Lin <linmiaohe@huawei.com>]

On 2022/6/1 2:05, Andrew Morton wrote:
> On Tue, 31 May 2022 20:25:30 +0800 Miaohe Lin <linmiaohe@huawei.com> wrote:
> 
>> For now we only support migrating to un-addressable device memory. Other
>> types of ZONE_DEVICE pages are not supported yet. So skip those pages in
>> MIGRATE_VMA_SELECT_SYSTEM case to save useless effort.
>>
> 
> https://lkml.kernel.org/r/20220531155629.20057-4-alex.sierra@amd.com
> just made similar-but-different changes here.  Please review those.
> 
> Normally I'm merge your fixlet ahead of the larger changes and redo
> Alex's patchset.  Because Alex's larger patchset might never get
> mainlined, so your fixlet would then get lost.
> 
> But in this case, your fixlet doesn't seem important enough to be
> churning things around in that way?

Yes. Above similar-but-different changes look good to me. I'm fine to drop
this patch.

Thanks!

> 
>> --- a/mm/migrate_device.c
>> +++ b/mm/migrate_device.c
>> @@ -157,6 +157,11 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
>>  				goto next;
>>  			}
>>  			page = vm_normal_page(migrate->vma, addr, pte);
>> +			/*
>> +			 * Other types of ZONE_DEVICE page are not supported.
>> +			 */
>> +			if (page && is_zone_device_page(page))
>> +				goto next;
>>  			mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
>>  			mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
>>  		}
> 
> .
>