On Tue, 2017-03-28 at 15:11 +0200, Michal Hocko wrote:
> On Wed 22-03-17 10:09:43, Jiri Slaby wrote:
> [...]
> > @@ -1245,6 +1254,10 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
> >
> > page = pmd_page(*pmd);
> > VM_BUG_ON(!PageHead(page));
> > +
> > + if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, page, flags))
> > + goto out;
> > +
> > if (flags & FOLL_TOUCH) {
> > pmd_t _pmd;
> > /*
>
> I have just noticed that this patch is not correct fo 3.12 because we
> should return NULL rather than the page in this case. 3.2 is wrong as
> well AFAICS.
Thanks for reporting this. This is the same mistake I made initially
with follow_page() in 3.2. But I had a test case which caught that
before release, and I don't have a test case for this.
Ben.
--
Ben Hutchings
To err is human; to really foul things up requires a computer.
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