return pfn_to_page(pfn);
}
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
+ pmd_t pmd)
+{
+ unsigned long pfn = pmd_pfn(pmd);
+
+ /*
+ * There is no pmd_special() but there may be special pmds, e.g.
+ * in a direct-access (dax) mapping, so let's just replicate the
+ * !HAVE_PTE_SPECIAL case from vm_normal_page() here.
+ */
+ if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
+ if (vma->vm_flags & VM_MIXEDMAP) {
+ if (!pfn_valid(pfn))
+ return NULL;
+ goto out;
+ } else {
+ unsigned long off;
+ off = (addr - vma->vm_start) >> PAGE_SHIFT;
+ if (pfn == vma->vm_pgoff + off)
+ return NULL;
+ if (!is_cow_mapping(vma->vm_flags))
+ return NULL;
+ }
+ }
+
+ if (is_zero_pfn(pfn))
+ return NULL;
+ if (unlikely(pfn > highest_memmap_pfn))
+ return NULL;
+
+ /*
+ * NOTE! We still have PageReserved() pages in the page tables.
+ * eg. VDSO mappings can cause them to exist.
+ */
+out:
+ return pfn_to_page(pfn);
+}
+#endif
+
/*
* copy one vm_area from one task to the other. Assumes the page tables
* already present in the new task to be cleared in the whole range
if (unlikely(pmd_none(*pmd)) &&
unlikely(__pte_alloc(mm, vma, pmd, address)))
return VM_FAULT_OOM;
- /* if an huge pmd materialized from under us just retry later */
- if (unlikely(pmd_trans_huge(*pmd)))
+ /*
+ * If a huge pmd materialized under us just retry later. Use
+ * pmd_trans_unstable() instead of pmd_trans_huge() to ensure the pmd
+ * didn't become pmd_trans_huge under us and then back to pmd_none, as
+ * a result of MADV_DONTNEED running immediately after a huge pmd fault
+ * in a different thread of this mm, in turn leading to a misleading
+ * pmd_trans_huge() retval. All we have to ensure is that it is a
+ * regular pmd that we can walk with pte_offset_map() and we can do that
+ * through an atomic read in C, which is what pmd_trans_unstable()
+ * provides.
+ */
+ if (unlikely(pmd_trans_unstable(pmd)))
return 0;
/*
* A regular pmd is established and it can't morph into a huge pmd