On Tue, 1 Jun 2021, Matthew Wilcox wrote:
> On Tue, Jun 01, 2021 at 02:09:31PM -0700, Hugh Dickins wrote:
> > static inline unsigned long
> > -__vma_address(struct page *page, struct vm_area_struct *vma)
> > +vma_address(struct page *page, struct vm_area_struct *vma)
> > {
> > - pgoff_t pgoff = page_to_pgoff(page);
> > - return vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
> > + pgoff_t pgoff;
> > + unsigned long address;
> > +
> > + VM_BUG_ON_PAGE(PageKsm(page), page); /* KSM page->index unusable */
> > + pgoff = page_to_pgoff(page);
> > + if (pgoff >= vma->vm_pgoff) {
> > + address = vma->vm_start +
> > + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
> > + /* Check for address beyond vma (or wrapped through 0?) */
> > + if (address < vma->vm_start || address >= vma->vm_end)
> > + address = -EFAULT;
> > + } else if (PageHead(page) &&
> > + pgoff + (1UL << compound_order(page)) > vma->vm_pgoff) {
>
> } else if (PageHead(page) &&
> pgoff + compound_nr(page) > vma->vm_pgoff) {
Yes, that's better, thanks.
I was tempted to leave out the preliminary PageHead() test altogether;
but you didn't suggest that, and I've concluded that perhaps it makes
for good documentation, even though not strictly needed.
>
> > +vma_address_end(struct page *page, struct vm_area_struct *vma)
> > {
> > + pgoff_t pgoff;
> > + unsigned long address;
> > +
> > + VM_BUG_ON_PAGE(PageKsm(page), page); /* KSM page->index unusable */
> > + pgoff = page_to_pgoff(page);
> > + if (PageHead(page))
> > + pgoff += 1UL << compound_order(page);
> > + else
> > + pgoff++;
>
> Again, can use compound_nr here. In fact, the whole thing can be:
>
> pgoff += compound_nr(page);
Even nicer; and I've taken the liberty of just saying
pgoff = page_to_pgoff(page) + compound_nr(page);
v2 of this patch coming up now, thanks.
Hugh
