SLUB: support slub_debug on by default

Add a new configuration variable

CONFIG_SLUB_DEBUG_ON

If set then the kernel will be booted by default with slab debugging
switched on. Similar to CONFIG_SLAB_DEBUG. By default slab debugging
is available but must be enabled by specifying "slub_debug" as a
kernel parameter.

Also add support to switch off slab debugging for a kernel that was
built with CONFIG_SLUB_DEBUG_ON. This works by specifying

slub_debug=-

as a kernel parameter.

Dave Jones wanted this feature.
http://marc.info/?l=linux-kernel&m=118072189913045&w=2

[akpm@linux-foundation.org: clean up switch statement]
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 51 insertions, 28 deletions

diff --git a/mm/slub.c b/mm/slub.c
index e0cf6213abc0..6aea48942c29 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -323,7 +323,11 @@ static inline int slab_index(void *p, struct kmem_cache *s, void *addr)
 /*
  * Debug settings:
  */
+#ifdef CONFIG_SLUB_DEBUG_ON
+static int slub_debug = DEBUG_DEFAULT_FLAGS;
+#else
 static int slub_debug;
+#endif
 
 static char *slub_debug_slabs;
 
@@ -888,38 +892,57 @@ fail:
 
 static int __init setup_slub_debug(char *str)
 {
-	if (!str || *str != '=')
-		slub_debug = DEBUG_DEFAULT_FLAGS;
-	else {
-		str++;
-		if (*str == 0 || *str == ',')
-			slub_debug = DEBUG_DEFAULT_FLAGS;
-		else
-		for( ;*str && *str != ','; str++)
-			switch (*str) {
-			case 'f' : case 'F' :
-				slub_debug |= SLAB_DEBUG_FREE;
-				break;
-			case 'z' : case 'Z' :
-				slub_debug |= SLAB_RED_ZONE;
-				break;
-			case 'p' : case 'P' :
-				slub_debug |= SLAB_POISON;
-				break;
-			case 'u' : case 'U' :
-				slub_debug |= SLAB_STORE_USER;
-				break;
-			case 't' : case 'T' :
-				slub_debug |= SLAB_TRACE;
-				break;
-			default:
-				printk(KERN_ERR "slub_debug option '%c' "
-					"unknown. skipped\n",*str);
-			}
+	slub_debug = DEBUG_DEFAULT_FLAGS;
+	if (*str++ != '=' || !*str)
+		/*
+		 * No options specified. Switch on full debugging.
+		 */
+		goto out;
+
+	if (*str == ',')
+		/*
+		 * No options but restriction on slabs. This means full
+		 * debugging for slabs matching a pattern.
+		 */
+		goto check_slabs;
+
+	slub_debug = 0;
+	if (*str == '-')
+		/*
+		 * Switch off all debugging measures.
+		 */
+		goto out;
+
+	/*
+	 * Determine which debug features should be switched on
+	 */
+	for ( ;*str && *str != ','; str++) {
+		switch (tolower(*str)) {
+		case 'f':
+			slub_debug |= SLAB_DEBUG_FREE;
+			break;
+		case 'z':
+			slub_debug |= SLAB_RED_ZONE;
+			break;
+		case 'p':
+			slub_debug |= SLAB_POISON;
+			break;
+		case 'u':
+			slub_debug |= SLAB_STORE_USER;
+			break;
+		case 't':
+			slub_debug |= SLAB_TRACE;
+			break;
+		default:
+			printk(KERN_ERR "slub_debug option '%c' "
+				"unknown. skipped\n",*str);
+		}
 	}
 
+check_slabs:
 	if (*str == ',')
 		slub_debug_slabs = str + 1;
+out:
 	return 1;
 }