+/*
+ * huge_pages_needed tries to determine the number of new huge pages that
+ * will be required to fully populate this VMA. This will be equal to
+ * the size of the VMA in huge pages minus the number of huge pages
+ * (covered by this VMA) that are found in the page cache.
+ *
+ * Result is in bytes to be compatible with is_hugepage_mem_enough()
+ */
+static unsigned long
+huge_pages_needed(struct address_space *mapping, struct vm_area_struct *vma)
+{
+ int i;
+ struct pagevec pvec;
+ unsigned long start = vma->vm_start;
+ unsigned long end = vma->vm_end;
+ unsigned long hugepages = (end - start) >> HPAGE_SHIFT;
+ pgoff_t next = vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT);
+ pgoff_t endpg = next + hugepages;
+
+ pagevec_init(&pvec, 0);
+ while (next < endpg) {
+ if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE))
+ break;
+ for (i = 0; i < pagevec_count(&pvec); i++) {
+ struct page *page = pvec.pages[i];
+ if (page->index > next)
+ next = page->index;
+ if (page->index >= endpg)
+ break;
+ next++;
+ hugepages--;
+ }
+ huge_pagevec_release(&pvec);
+ }
+ return hugepages << HPAGE_SHIFT;
+}
+