mm, hugetlb, hwpoison: separate branch for free and in-use hugepage

We know that HPageFreed pages should have page refcount 0, so
get_page_unless_zero() always fails and returns 0.  So explicitly separate
the branch based on page state for minor optimization and better
readability.

Link: https://lkml.kernel.org/r/20220415041848.GA3034499@ik1-406-35019.vs.sakura.ne.jpSigned-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Suggested-by: Mike Kravetz <mike.kravetz@oracle.com>
Suggested-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/hugetlb.c

@@ -6776,7 +6776,9 @@ int get_hwpoison_huge_page(struct page *page, bool *hugetlb)
 	spin_lock_irq(&hugetlb_lock);
 	if (PageHeadHuge(page)) {
 		*hugetlb = true;
-		if (HPageFreed(page) || HPageMigratable(page))
+		if (HPageFreed(page))
+			ret = 0;
+		else if (HPageMigratable(page))
 			ret = get_page_unless_zero(page);
 		else
 			ret = -EBUSY;

mm/memory-failure.c

@@ -1517,7 +1517,9 @@ int __get_huge_page_for_hwpoison(unsigned long pfn, int flags)
 	if (flags & MF_COUNT_INCREASED) {
 		ret = 1;
 		count_increased = true;
-	} else if (HPageFreed(head) || HPageMigratable(head)) {
+	} else if (HPageFreed(head)) {
+		ret = 0;
+	} else if (HPageMigratable(head)) {
 		ret = get_page_unless_zero(head);
 		if (ret)
 			count_increased = true;