Re: [PATCHv5 22/36] mm, hugetlb: switch hugetlbfs to multi-order radix-tree entries

Hillf Danton
2016-12-01T03:10:52Z

On Wednesday, November 30, 2016 9:16 PM Kirill A. Shutemov wrote:
> On Wed, Nov 30, 2016 at 05:48:05PM +0800, Hillf Danton wrote:
> > On Tuesday, November 29, 2016 7:23 PM Kirill A. Shutemov wrote:
> > > @@ -607,10 +605,10 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
> > > }
> > >
> > > /* Set numa allocation policy based on index */
> > > - hugetlb_set_vma_policy(&pseudo_vma, inode, index);
> > > + hugetlb_set_vma_policy(&pseudo_vma, inode, index >> huge_page_order(h));
> > >
> > > /* addr is the offset within the file (zero based) */
> > > - addr = index * hpage_size;
> > > + addr = index << PAGE_SHIFT & ~huge_page_mask(h);
> > >
> > > /* mutex taken here, fault path and hole punch */
> > > hash = hugetlb_fault_mutex_hash(h, mm, &pseudo_vma, mapping,
> >
> > Seems we can't use index in computing hash as long as it isn't in huge page size.
>
> Look at changes in hugetlb_fault_mutex_hash(): we shift the index right by
> huge_page_order(), before calculating the hash. I don't see a problem
> here.
>
You are right. I missed that critical point.

thanks
Hillf