On Tue 07-01-14 12:34:34, Wanpeng Li wrote:
> Cced Sasha,
> On Tue, Jan 07, 2014 at 12:26:13PM +0800, Wanpeng Li wrote:
> >Hi Michal,
> >On Mon, Jan 06, 2014 at 03:18:27PM +0100, Michal Hocko wrote:
> >>On Mon 06-01-14 20:45:54, Bob Liu wrote:
> >>[...]
> >>> 544 if (PageAnon(page)) {
> >>> 545 struct anon_vma *page__anon_vma =
> >>> page_anon_vma(page);
> >>> 546 /*
> >>> 547 * Note: swapoff's unuse_vma() is more efficient
> >>> with this
> >>> 548 * check, and needs it to match anon_vma when KSM is
> >>> active.
> >>> 549 */
> >>> 550 if (!vma->anon_vma || !page__anon_vma ||
> >>> 551 vma->anon_vma->root != page__anon_vma->root)
> >>> 552 return -EFAULT;
> >>> 553 } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR))
> >>> {
> >>> 554 if (!vma->vm_file ||
> >>> 555 vma->vm_file->f_mapping != page->mapping)
> >>> 556 return -EFAULT;
> >>> 557 } else
> >>> 558 return -EFAULT;
> >>>
> >>> That's the "other conditions" and the reason why we can't use
> >>> BUG_ON(!vma) in new_vma_page().
> >>
> >>Sorry, I wasn't clear with my question. I was interested in which of
> >>these triggered and why only for hugetlb pages?
> >
> >Not just for hugetlb pages, sorry for do two things in one patch. The change
> >for hugetlb pages is to fix the potential dereference NULL pointer reported
> >by Dan. http://marc.info/?l=linux-mm&m=137689530323257&w=2
> >
> >If we should ask Sasha to add more debug information to dump which condition
> >is failed in page_address_in_vma() for you?
I am always more calm when the removed BUG_ON is properly understood and
justified.
--
Michal Hocko
SUSE Labs
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