SLUB: add CONFIG_SLUB_DEBUG

CONFIG_SLUB_DEBUG can be used to switch off the debugging and sysfs components
of SLUB.  Thus SLUB will be able to replace SLOB.  SLUB can arrange objects in
a denser way than SLOB and the code size should be minimal without debugging
and sysfs support.

Note that CONFIG_SLUB_DEBUG is materially different from CONFIG_SLAB_DEBUG.
CONFIG_SLAB_DEBUG is used to enable slab debugging in SLAB.  SLUB enables
debugging via a boot parameter.  SLUB debug code should always be present.

CONFIG_SLUB_DEBUG can be modified in the embedded config section.

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>

2 files changed, 123 insertions, 75 deletions

diff --git a/init/Kconfig b/init/Kconfig
index d0edf42f4dba..da6a91c4a051 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -504,6 +504,15 @@ config VM_EVENT_COUNTERS
           on EMBEDDED systems.  /proc/vmstat will only show page counts
           if VM event counters are disabled.
 
+config SLUB_DEBUG
+        default y
+        bool "Enable SLUB debugging support" if EMBEDDED
+        help
+          SLUB has extensive debug support features. Disabling these can
+          result in significant savings in code size. This also disables
+          SLUB sysfs support. /sys/slab will not exist and there will be
+          no support for cache validation etc.
+
 choice
         prompt "Choose SLAB allocator"
         default SLAB
diff --git a/mm/slub.c b/mm/slub.c
index b9e05366afda..3e614c1901b7 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -89,17 +89,25 @@
 
 static inline int SlabDebug(struct page *page)
 {
+#ifdef CONFIG_SLUB_DEBUG
         return PageError(page);
+#else
+        return 0;
+#endif
 }
 
 static inline void SetSlabDebug(struct page *page)
 {
+#ifdef CONFIG_SLUB_DEBUG
         SetPageError(page);
+#endif
 }
 
 static inline void ClearSlabDebug(struct page *page)
 {
+#ifdef CONFIG_SLUB_DEBUG
         ClearPageError(page);
+#endif
 }
 
 /*
@@ -207,7 +215,7 @@ struct track {
 
 enum track_item { TRACK_ALLOC, TRACK_FREE };
 
-#ifdef CONFIG_SYSFS
+#if defined(CONFIG_SYSFS) && defined(CONFIG_SLUB_DEBUG)
 static int sysfs_slab_add(struct kmem_cache *);
 static int sysfs_slab_alias(struct kmem_cache *, const char *);
 static void sysfs_slab_remove(struct kmem_cache *);
@@ -284,6 +292,14 @@ static inline int slab_index(void *p, struct kmem_cache *s, void *addr)
         return (p - addr) / s->size;
 }
 
+#ifdef CONFIG_SLUB_DEBUG
+/*
+ * Debug settings:
+ */
+static int slub_debug;
+
+static char *slub_debug_slabs;
+
 /*
  * Object debugging
  */
@@ -821,6 +837,97 @@ static void trace(struct kmem_cache *s, struct page *page, void *object, int all
         }
 }
 
+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);
+                        }
+        }
+
+        if (*str == ',')
+                slub_debug_slabs = str + 1;
+        return 1;
+}
+
+__setup("slub_debug", setup_slub_debug);
+
+static void kmem_cache_open_debug_check(struct kmem_cache *s)
+{
+        /*
+         * The page->offset field is only 16 bit wide. This is an offset
+         * in units of words from the beginning of an object. If the slab
+         * size is bigger then we cannot move the free pointer behind the
+         * object anymore.
+         *
+         * On 32 bit platforms the limit is 256k. On 64bit platforms
+         * the limit is 512k.
+         *
+         * Debugging or ctor/dtors may create a need to move the free
+         * pointer. Fail if this happens.
+         */
+        if (s->size >= 65535 * sizeof(void *)) {
+                BUG_ON(s->flags & (SLAB_RED_ZONE | SLAB_POISON |
+                                SLAB_STORE_USER | SLAB_DESTROY_BY_RCU));
+                BUG_ON(s->ctor || s->dtor);
+        }
+        else
+                /*
+                 * Enable debugging if selected on the kernel commandline.
+                 */
+                if (slub_debug && (!slub_debug_slabs ||
+                    strncmp(slub_debug_slabs, s->name,
+                        strlen(slub_debug_slabs)) == 0))
+                                s->flags |= slub_debug;
+}
+#else
+
+static inline int alloc_object_checks(struct kmem_cache *s,
+                struct page *page, void *object) { return 0; }
+
+static inline int free_object_checks(struct kmem_cache *s,
+                struct page *page, void *object) { return 0; }
+
+static inline void add_full(struct kmem_cache_node *n, struct page *page) {}
+static inline void remove_full(struct kmem_cache *s, struct page *page) {}
+static inline void trace(struct kmem_cache *s, struct page *page,
+                        void *object, int alloc) {}
+static inline void init_object(struct kmem_cache *s,
+                        void *object, int active) {}
+static inline void init_tracking(struct kmem_cache *s, void *object) {}
+static inline int slab_pad_check(struct kmem_cache *s, struct page *page)
+                        { return 1; }
+static inline int check_object(struct kmem_cache *s, struct page *page,
+                        void *object, int active) { return 1; }
+static inline void set_track(struct kmem_cache *s, void *object,
+                        enum track_item alloc, void *addr) {}
+static inline void kmem_cache_open_debug_check(struct kmem_cache *s) {}
+#define slub_debug 0
+#endif
 /*
  * Slab allocation and freeing
  */
@@ -1446,13 +1553,6 @@ static int slub_min_objects = DEFAULT_MIN_OBJECTS;
 static int slub_nomerge;
 
 /*
- * Debug settings:
- */
-static int slub_debug;
-
-static char *slub_debug_slabs;
-
-/*
  * Calculate the order of allocation given an slab object size.
  *
  * The order of allocation has significant impact on performance and other
@@ -1660,6 +1760,7 @@ static int calculate_sizes(struct kmem_cache *s)
          */
         size = ALIGN(size, sizeof(void *));
 
+#ifdef CONFIG_SLUB_DEBUG
         /*
          * If we are Redzoning then check if there is some space between the
          * end of the object and the free pointer. If not then add an
@@ -1667,6 +1768,7 @@ static int calculate_sizes(struct kmem_cache *s)
          */
         if ((flags & SLAB_RED_ZONE) && size == s->objsize)
                 size += sizeof(void *);
+#endif
 
         /*
          * With that we have determined the number of bytes in actual use
@@ -1674,6 +1776,7 @@ static int calculate_sizes(struct kmem_cache *s)
          */
         s->inuse = size;
 
+#ifdef CONFIG_SLUB_DEBUG
         if (((flags & (SLAB_DESTROY_BY_RCU | SLAB_POISON)) ||
                 s->ctor || s->dtor)) {
                 /*
@@ -1704,6 +1807,7 @@ static int calculate_sizes(struct kmem_cache *s)
                  * of the object.
                  */
                 size += sizeof(void *);
+#endif
 
         /*
          * Determine the alignment based on various parameters that the
@@ -1753,32 +1857,7 @@ static int kmem_cache_open(struct kmem_cache *s, gfp_t gfpflags,
         s->objsize = size;
         s->flags = flags;
         s->align = align;
-
-        /*
-         * The page->offset field is only 16 bit wide. This is an offset
-         * in units of words from the beginning of an object. If the slab
-         * size is bigger then we cannot move the free pointer behind the
-         * object anymore.
-         *
-         * On 32 bit platforms the limit is 256k. On 64bit platforms
-         * the limit is 512k.
-         *
-         * Debugging or ctor/dtors may create a need to move the free
-         * pointer. Fail if this happens.
-         */
-        if (s->size >= 65535 * sizeof(void *)) {
-                BUG_ON(flags & (SLAB_RED_ZONE | SLAB_POISON |
-                                SLAB_STORE_USER | SLAB_DESTROY_BY_RCU));
-                BUG_ON(ctor || dtor);
-        }
-        else
-                /*
-                 * Enable debugging if selected on the kernel commandline.
-                 */
-                if (slub_debug && (!slub_debug_slabs ||
-                    strncmp(slub_debug_slabs, name,
-                        strlen(slub_debug_slabs)) == 0))
-                                s->flags |= slub_debug;
+        kmem_cache_open_debug_check(s);
 
         if (!calculate_sizes(s))
                 goto error;
@@ -1949,45 +2028,6 @@ static int __init setup_slub_nomerge(char *str)
 
 __setup("slub_nomerge", setup_slub_nomerge);
 
-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);
-                        }
-        }
-
-        if (*str == ',')
-                slub_debug_slabs = str + 1;
-        return 1;
-}
-
-__setup("slub_debug", setup_slub_debug);
-
 static struct kmem_cache *create_kmalloc_cache(struct kmem_cache *s,
                 const char *name, int size, gfp_t gfp_flags)
 {
@@ -2554,8 +2594,7 @@ void *__kmalloc_node_track_caller(size_t size, gfp_t gfpflags,
         return slab_alloc(s, gfpflags, node, caller);
 }
 
-#ifdef CONFIG_SYSFS
-
+#if defined(CONFIG_SYSFS) && defined(CONFIG_SLUB_DEBUG)
 static int validate_slab(struct kmem_cache *s, struct page *page)
 {
         void *p;