mm/slub.c: parse slub_debug O option in switch statement

By moving the O option detection into the switch statement, we allow this
parameter to be combined with other options correctly. Previously options
like slub_debug=OFZ would only detect the 'o' and use DEBUG_DEFAULT_FLAGS
to fill in the rest of the flags.

Signed-off-by: Chris J Arges <[e-mail]>
Cc: Christoph Lameter <[e-mail]>
Cc: Pekka Enberg <[e-mail]>
Acked-by: David Rientjes <[e-mail]>
Cc: Joonsoo Kim <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

mm/slub.c

···
 		 */
 		goto check_slabs;
 
-	if (tolower(*str) == 'o') {
-		/*
-		 * Avoid enabling debugging on caches if its minimum order
-		 * would increase as a result.
-		 */
-		disable_higher_order_debug = 1;
-		goto out;
-	}
-
 	slub_debug = 0;
 	if (*str == '-')
 		/*
···
 			break;
 		case 'a':
 			slub_debug |= SLAB_FAILSLAB;
+			break;
+		case 'o':
+			/*
+			 * Avoid enabling debugging on caches if its minimum
+			 * order would increase as a result.
+			 */
+			disable_higher_order_debug = 1;
 			break;
 		default:
 			pr_err("slub_debug option '%c' unknown. skipped\n",