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SubjectRe: [RFC PATCH 1/1] x86/mm/pat: Clear VM_PAT if copy_p4d_range failed
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On 2023/2/23 4:03, Dave Hansen wrote:
> On 2/16/23 18:56, Wupeng Ma wrote:
>> dup_mm
>> dup_mmap
>> copy_page_range
>> copy_p4d_range
>> copy_pud_range
>> copy_pmd_range
>> pmd_alloc
>> __pmd_alloc
>> pmd_alloc_one
>> page = alloc_pages(gfp, 0);
>> if (!page)
>> return NULL;
>> mmput
>> exit_mmap
>> unmap_vmas
>> unmap_single_vma
>> untrack_pfn
>> follow_phys
>> WARN_ON_ONCE(1);
>
> What's the point of that warning in the first place? I can certainly
> imagine follow_phys() failing for sparse mappings, for instance. Is
> there some requirement that VM_PFNMAP can't be sparse?

Hi Dave

Thanks for reviewing.

Sorry,I have no idea why warning in the first place.

I think we can delete this WARN_ON_ONCE with another patch?

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