Merge branches 'slab/cleanups' and 'slab/fixes' into for-linus

Documentation/vm/slub.txt

@@ -41,6 +41,8 @@ Possible debug options are
 	P		Poisoning (object and padding)
 	U		User tracking (free and alloc)
 	T		Trace (please only use on single slabs)
+	O		Switch debugging off for caches that would have
+			caused higher minimum slab orders
 	-		Switch all debugging off (useful if the kernel is
 			configured with CONFIG_SLUB_DEBUG_ON)
 
@@ -59,6 +61,14 @@ to the dentry cache with
 
 	slub_debug=F,dentry
 
+Debugging options may require the minimum possible slab order to increase as
+a result of storing the metadata (for example, caches with PAGE_SIZE object
+sizes).  This has a higher liklihood of resulting in slab allocation errors
+in low memory situations or if there's high fragmentation of memory.  To
+switch off debugging for such caches by default, use
+
+	slub_debug=O
+
 In case you forgot to enable debugging on the kernel command line: It is
 possible to enable debugging manually when the kernel is up. Look at the
 contents of:

include/linux/slob_def.h

@@ -34,9 +34,4 @@ static __always_inline void *__kmalloc(size_t size, gfp_t flags)
 	return kmalloc(size, flags);
 }
 
-static inline void kmem_cache_init_late(void)
-{
-	/* Nothing to do */
-}
-
 #endif /* __LINUX_SLOB_DEF_H */

include/linux/slub_def.h

@@ -153,12 +153,10 @@ static __always_inline int kmalloc_index(size_t size)
 	if (size <= KMALLOC_MIN_SIZE)
 		return KMALLOC_SHIFT_LOW;
 
-#if KMALLOC_MIN_SIZE <= 64
-	if (size > 64 && size <= 96)
+	if (KMALLOC_MIN_SIZE <= 32 && size > 64 && size <= 96)
 		return 1;
-	if (size > 128 && size <= 192)
+	if (KMALLOC_MIN_SIZE <= 64 && size > 128 && size <= 192)
 		return 2;
-#endif
 	if (size <=          8) return 3;
 	if (size <=         16) return 4;
 	if (size <=         32) return 5;
@@ -304,6 +302,4 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
 }
 #endif
 
-void __init kmem_cache_init_late(void);
-
 #endif /* _LINUX_SLUB_DEF_H */

mm/slob.c

@@ -692,3 +692,8 @@ void __init kmem_cache_init(void)
 {
 	slob_ready = 1;
 }
+
+void __init kmem_cache_init_late(void)
+{
+	/* Nothing to do */
+}

mm/slub.c

@@ -140,6 +140,13 @@
 #define DEBUG_DEFAULT_FLAGS (SLAB_DEBUG_FREE | SLAB_RED_ZONE | \
 				SLAB_POISON | SLAB_STORE_USER)
 
+/*
+ * Debugging flags that require metadata to be stored in the slab.  These get
+ * disabled when slub_debug=O is used and a cache's min order increases with
+ * metadata.
+ */
+#define DEBUG_METADATA_FLAGS (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER)
+
 /*
  * Set of flags that will prevent slab merging
  */
@@ -325,6 +332,7 @@ static int slub_debug;
 #endif
 
 static char *slub_debug_slabs;
+static int disable_higher_order_debug;
 
 /*
  * Object debugging
@@ -646,7 +654,7 @@ static int slab_pad_check(struct kmem_cache *s, struct page *page)
 	slab_err(s, page, "Padding overwritten. 0x%p-0x%p", fault, end - 1);
 	print_section("Padding", end - remainder, remainder);
 
-	restore_bytes(s, "slab padding", POISON_INUSE, start, end);
+	restore_bytes(s, "slab padding", POISON_INUSE, end - remainder, end);
 	return 0;
 }
 
@@ -976,6 +984,15 @@ static int __init setup_slub_debug(char *str)
 		 */
 		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 == '-')
 		/*
@@ -1026,8 +1043,8 @@ static unsigned long kmem_cache_flags(unsigned long objsize,
 	 * Enable debugging if selected on the kernel commandline.
 	 */
 	if (slub_debug && (!slub_debug_slabs ||
-	    strncmp(slub_debug_slabs, name, strlen(slub_debug_slabs)) == 0))
-			flags |= slub_debug;
+		!strncmp(slub_debug_slabs, name, strlen(slub_debug_slabs))))
+		flags |= slub_debug;
 
 	return flags;
 }
@@ -1109,8 +1126,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 	}
 
 	if (kmemcheck_enabled
-		&& !(s->flags & (SLAB_NOTRACK | DEBUG_DEFAULT_FLAGS)))
-	{
+		&& !(s->flags & (SLAB_NOTRACK | DEBUG_DEFAULT_FLAGS))) {
 		int pages = 1 << oo_order(oo);
 
 		kmemcheck_alloc_shadow(page, oo_order(oo), flags, node);
@@ -1560,6 +1576,10 @@ slab_out_of_memory(struct kmem_cache *s, gfp_t gfpflags, int nid)
 		"default order: %d, min order: %d\n", s->name, s->objsize,
 		s->size, oo_order(s->oo), oo_order(s->min));
 
+	if (oo_order(s->min) > get_order(s->objsize))
+		printk(KERN_WARNING "  %s debugging increased min order, use "
+		       "slub_debug=O to disable.\n", s->name);
+
 	for_each_online_node(node) {
 		struct kmem_cache_node *n = get_node(s, node);
 		unsigned long nr_slabs;
@@ -2001,7 +2021,7 @@ static inline int calculate_order(int size)
 				return order;
 			fraction /= 2;
 		}
-		min_objects --;
+		min_objects--;
 	}
 
 	/*
@@ -2400,6 +2420,7 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order)
 	 * on bootup.
 	 */
 	align = calculate_alignment(flags, align, s->objsize);
+	s->align = align;
 
 	/*
 	 * SLUB stores one object immediately after another beginning from
@@ -2452,6 +2473,18 @@ static int kmem_cache_open(struct kmem_cache *s, gfp_t gfpflags,
 
 	if (!calculate_sizes(s, -1))
 		goto error;
+	if (disable_higher_order_debug) {
+		/*
+		 * Disable debugging flags that store metadata if the min slab
+		 * order increased.
+		 */
+		if (get_order(s->size) > get_order(s->objsize)) {
+			s->flags &= ~DEBUG_METADATA_FLAGS;
+			s->offset = 0;
+			if (!calculate_sizes(s, -1))
+				goto error;
+		}
+	}
 
 	/*
 	 * The larger the object size is, the more pages we want on the partial
@@ -2790,6 +2823,11 @@ static s8 size_index[24] = {
 	2	/* 192 */
 };
 
+static inline int size_index_elem(size_t bytes)
+{
+	return (bytes - 1) / 8;
+}
+
 static struct kmem_cache *get_slab(size_t size, gfp_t flags)
 {
 	int index;
@@ -2798,7 +2836,7 @@ static struct kmem_cache *get_slab(size_t size, gfp_t flags)
 		if (!size)
 			return ZERO_SIZE_PTR;
 
-		index = size_index[(size - 1) / 8];
+		index = size_index[size_index_elem(size)];
 	} else
 		index = fls(size - 1);
 
@@ -3156,10 +3194,12 @@ void __init kmem_cache_init(void)
 	slab_state = PARTIAL;
 
 	/* Caches that are not of the two-to-the-power-of size */
-	if (KMALLOC_MIN_SIZE <= 64) {
+	if (KMALLOC_MIN_SIZE <= 32) {
 		create_kmalloc_cache(&kmalloc_caches[1],
 				"kmalloc-96", 96, GFP_NOWAIT);
 		caches++;
+	}
+	if (KMALLOC_MIN_SIZE <= 64) {
 		create_kmalloc_cache(&kmalloc_caches[2],
 				"kmalloc-192", 192, GFP_NOWAIT);
 		caches++;
@@ -3186,17 +3226,28 @@ void __init kmem_cache_init(void)
 	BUILD_BUG_ON(KMALLOC_MIN_SIZE > 256 ||
 		(KMALLOC_MIN_SIZE & (KMALLOC_MIN_SIZE - 1)));
 
-	for (i = 8; i < KMALLOC_MIN_SIZE; i += 8)
-		size_index[(i - 1) / 8] = KMALLOC_SHIFT_LOW;
+	for (i = 8; i < KMALLOC_MIN_SIZE; i += 8) {
+		int elem = size_index_elem(i);
+		if (elem >= ARRAY_SIZE(size_index))
+			break;
+		size_index[elem] = KMALLOC_SHIFT_LOW;
+	}
 
-	if (KMALLOC_MIN_SIZE == 128) {
+	if (KMALLOC_MIN_SIZE == 64) {
+		/*
+		 * The 96 byte size cache is not used if the alignment
+		 * is 64 byte.
+		 */
+		for (i = 64 + 8; i <= 96; i += 8)
+			size_index[size_index_elem(i)] = 7;
+	} else if (KMALLOC_MIN_SIZE == 128) {
 		/*
 		 * The 192 byte sized cache is not used if the alignment
 		 * is 128 byte. Redirect kmalloc to use the 256 byte cache
 		 * instead.
 		 */
 		for (i = 128 + 8; i <= 192; i += 8)
-			size_index[(i - 1) / 8] = 8;
+			size_index[size_index_elem(i)] = 8;
 	}
 
 	slab_state = UP;
@@ -4543,8 +4594,11 @@ static int sysfs_slab_add(struct kmem_cache *s)
 	}
 
 	err = sysfs_create_group(&s->kobj, &slab_attr_group);
-	if (err)
+	if (err) {
+		kobject_del(&s->kobj);
+		kobject_put(&s->kobj);
 		return err;
+	}
 	kobject_uevent(&s->kobj, KOBJ_ADD);
 	if (!unmergeable) {
 		/* Setup first alias */
@@ -4726,7 +4780,7 @@ static const struct file_operations proc_slabinfo_operations = {
 
 static int __init slab_proc_init(void)
 {
-	proc_create("slabinfo",S_IWUSR|S_IRUGO,NULL,&proc_slabinfo_operations);
+	proc_create("slabinfo", S_IRUGO, NULL, &proc_slabinfo_operations);
 	return 0;
 }
 module_init(slab_proc_init);