mm: thp: Return the correct value for change_huge_pmd

The wrong value is being returned by change_huge_pmd since commit
10c1045f ("mm: numa: avoid unnecessary TLB flushes when setting
NUMA hinting entries") which allows a fallthrough that tries to adjust
non-existent PTEs. This patch corrects it.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/huge_memory.c

@@ -1487,6 +1487,7 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 
 	if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
 		pmd_t entry;
+		ret = 1;
 
 		/*
 		 * Avoid trapping faults against the zero page. The read-only
@@ -1495,11 +1496,10 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 		 */
 		if (prot_numa && is_huge_zero_pmd(*pmd)) {
 			spin_unlock(ptl);
-			return 0;
+			return ret;
 		}
 
 		if (!prot_numa || !pmd_protnone(*pmd)) {
-			ret = 1;
 			entry = pmdp_get_and_clear_notify(mm, addr, pmd);
 			entry = pmd_modify(entry, newprot);
 			ret = HPAGE_PMD_NR;