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;
 }