If would be bad if we actually set PageUptodate with UFFDIO_CONTINUE;
PageUptodate indicates that the page has been zeroed, and we don't want
to give a non-zeroed page to the user.
The reason this change is being made now is because UFFDIO_CONTINUEs on
subpages definitely shouldn't set this page flag on the head page.
Signed-off-by: James Houghton <jthoughton@xxxxxxxxxx>
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 07abcb6eb203..792cb2e67ce5 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6256,7 +6256,16 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
* preceding stores to the page contents become visible before
* the set_pte_at() write.
*/
- __folio_mark_uptodate(folio);
+ if (!is_continue)
+ __folio_mark_uptodate(folio);
+ else if (!folio_test_uptodate(folio)) {
+ /*
+ * This should never happen; HugeTLB pages are always Uptodate
+ * as soon as they are allocated.
+ */
+ ret = -EFAULT;
+ goto out_release_nounlock;
+ }
/* Add shared, newly allocated pages to the page cache. */
if (vm_shared && !is_continue) {
--
2.39.2.637.g21b0678d19-goog
