thp: remove some code depend on CONFIG_NUMA

If NUMA is disabled, hpage is used as page pre-alloc, so there are two
cases for hpage:

- it is !NULL, means the page is not consumed otherwise,
- the page has been consumed

If NUMA is enabled, hpage is just used as alloc-fail indicator which is
not a real page, NULL means not fail triggered.

So, we can release the page only if !IS_ERR_OR_NULL

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/huge_memory.c

@@ -2306,11 +2306,8 @@ static void khugepaged_wait_work(void)
 
 static void khugepaged_loop(void)
 {
-	struct page *hpage;
+	struct page *hpage = NULL;
 
-#ifdef CONFIG_NUMA
-	hpage = NULL;
-#endif
 	while (likely(khugepaged_enabled())) {
 #ifndef CONFIG_NUMA
 		hpage = khugepaged_alloc_hugepage();
@@ -2324,10 +2321,9 @@ static void khugepaged_loop(void)
 #endif
 
 		khugepaged_do_scan(&hpage);
-#ifndef CONFIG_NUMA
-		if (hpage)
+
+		if (!IS_ERR_OR_NULL(hpage))
 			put_page(hpage);
-#endif
 
 		khugepaged_wait_work();
 	}