Re: [RFC 2/3] mm: export zap_page_range()

[Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com>]

hi,

> On 22.03.22 14:02, Xiaoguang Wang wrote:
>> hi,
>>
>>> On 18.03.22 10:55, Xiaoguang Wang wrote:
>>>> Module target_core_user will use it to implement zero copy feature.
>>>>
>>>> Signed-off-by: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
>>>> ---
>>>>    mm/memory.c | 1 +
>>>>    1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/mm/memory.c b/mm/memory.c
>>>> index 1f745e4d11c2..9974d0406dad 100644
>>>> --- a/mm/memory.c
>>>> +++ b/mm/memory.c
>>>> @@ -1664,6 +1664,7 @@ void zap_page_range(struct vm_area_struct *vma, unsigned long start,
>>>>    	mmu_notifier_invalidate_range_end(&range);
>>>>    	tlb_finish_mmu(&tlb);
>>>>    }
>>>> +EXPORT_SYMBOL_GPL(zap_page_range);
>>>>    
>>>>    /**
>>>>     * zap_page_range_single - remove user pages in a given range
>>> To which VMAs will you be applying zap_page_range? I assume only to some
>>> special ones where you previously vm_insert_page(s)_mkspecial'ed pages,
>>> not to some otherwise random VMAs, correct?
>> Yes, you're right :)
> I'd suggest exposing a dedicated function that performs sanity checks on
> the vma (VM_PFNMAP ?) and only zaps within a single VMA.
>
> Essentially zap_page_range_single(), excluding "struct zap_details
> *details" and including sanity checks.
>
> Reason is that we don't want anybody to blindly zap_page_range() within
> random VMAs from a kernel module.
OK, I see, thanks. Xu Yu and I will try to implement a new helper in 
following new version patches.

Regards,
Xiaoguang Wang
>