On 1/30/2023 9:53 PM, Matthew Wilcox wrote:
> On Mon, Jan 30, 2023 at 08:55:03PM +0800, Yin Fengwei wrote:
>> +++ b/include/linux/mm.h
>> @@ -1061,6 +1061,8 @@ static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
>>
>> vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page);
>> void do_set_pte(struct vm_fault *vmf, struct page *page, unsigned long addr);
>> +void do_set_pte_entry(struct vm_fault *vmf, struct page *page,
>> + unsigned long addr);
>
> indentation
>
>> -void do_set_pte(struct vm_fault *vmf, struct page *page, unsigned long addr)
>> +void do_set_pte_entry(struct vm_fault *vmf, struct page *page,
>> + unsigned long addr)
>
> ditto
>
>> {
>> struct vm_area_struct *vma = vmf->vma;
>> bool uffd_wp = pte_marker_uffd_wp(vmf->orig_pte);
>> @@ -4276,6 +4277,16 @@ void do_set_pte(struct vm_fault *vmf, struct page *page, unsigned long addr)
>> entry = maybe_mkwrite(pte_mkdirty(entry), vma);
>> if (unlikely(uffd_wp))
>> entry = pte_mkuffd_wp(entry);
>> + set_pte_at(vma->vm_mm, addr, vmf->pte, entry);
>
> I'm not sure this is safe. As soon as you call set_pte_at(), the page
> can be found by GUP. If it is, and it doesn't have rmap set up, aren't
> things going to go horribly wrong?
Thanks a lot for pointing this out. I was not aware of the connection of
the sequence here with GUP. Will take care of this in next version by
putting rmap set up before set_pte_at().
Regards
Yin, Fengwei
>
