Messages in this thread | | | Date | Thu, 3 Jun 2021 14:36:11 -0700 (PDT) | From | Hugh Dickins <> | Subject | Re: [PATCH 3/7] mm/thp: fix vma_address() if virtual address below file offset |
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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
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