[PATCH] Cleanup slab headers / API to allow easy addition of new slab allocators

This is a response to an earlier discussion on linux-mm about splitting
slab.h components per allocator.  Patch is against 2.6.19-git11.  See
http://marc.theaimsgroup.com/?l=linux-mm&m=116469577431008&w=2

This patch cleans up the slab header definitions.  We define the common
functions of slob and slab in slab.h and put the extra definitions needed
for slab's kmalloc implementations in <linux/slab_def.h>.  In order to get
a greater set of common functions we add several empty functions to slob.c
and also rename slob's kmalloc to __kmalloc.

Slob does not need any special definitions since we introduce a fallback
case.  If there is no need for a slab implementation to provide its own
kmalloc mess^H^H^Hacros then we simply fall back to __kmalloc functions.
That is sufficient for SLOB.

Sort the function in slab.h according to their functionality.  First the
functions operating on struct kmem_cache * then the kmalloc related
functions followed by special debug and fallback definitions.

Also redo a lot of comments.

Signed-off-by: Christoph Lameter <clameter@sgi.com>?
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/slab_def.h

+#ifndef _LINUX_SLAB_DEF_H
+#define	_LINUX_SLAB_DEF_H
+
+/*
+ * Definitions unique to the original Linux SLAB allocator.
+ *
+ * What we provide here is a way to optimize the frequent kmalloc
+ * calls in the kernel by selecting the appropriate general cache
+ * if kmalloc was called with a size that can be established at
+ * compile time.
+ */
+
+#include <linux/init.h>
+#include <asm/page.h>		/* kmalloc_sizes.h needs PAGE_SIZE */
+#include <asm/cache.h>		/* kmalloc_sizes.h needs L1_CACHE_BYTES */
+#include <linux/compiler.h>
+
+/* Size description struct for general caches. */
+struct cache_sizes {
+	size_t		 	cs_size;
+	struct kmem_cache	*cs_cachep;
+	struct kmem_cache	*cs_dmacachep;
+};
+extern struct cache_sizes malloc_sizes[];
+
+static inline void *kmalloc(size_t size, gfp_t flags)
+{
+	if (__builtin_constant_p(size)) {
+		int i = 0;
+#define CACHE(x) \
+		if (size <= x) \
+			goto found; \
+		else \
+			i++;
+#include "kmalloc_sizes.h"
+#undef CACHE
+		{
+			extern void __you_cannot_kmalloc_that_much(void);
+			__you_cannot_kmalloc_that_much();
+		}
+found:
+		return kmem_cache_alloc((flags & GFP_DMA) ?
+			malloc_sizes[i].cs_dmacachep :
+			malloc_sizes[i].cs_cachep, flags);
+	}
+	return __kmalloc(size, flags);
+}
+
+static inline void *kzalloc(size_t size, gfp_t flags)
+{
+	if (__builtin_constant_p(size)) {
+		int i = 0;
+#define CACHE(x) \
+		if (size <= x) \
+			goto found; \
+		else \
+			i++;
+#include "kmalloc_sizes.h"
+#undef CACHE
+		{
+			extern void __you_cannot_kzalloc_that_much(void);
+			__you_cannot_kzalloc_that_much();
+		}
+found:
+		return kmem_cache_zalloc((flags & GFP_DMA) ?
+			malloc_sizes[i].cs_dmacachep :
+			malloc_sizes[i].cs_cachep, flags);
+	}
+	return __kzalloc(size, flags);
+}
+
+#ifdef CONFIG_NUMA
+extern void *__kmalloc_node(size_t size, gfp_t flags, int node);
+
+static inline void *kmalloc_node(size_t size, gfp_t flags, int node)
+{
+	if (__builtin_constant_p(size)) {
+		int i = 0;
+#define CACHE(x) \
+		if (size <= x) \
+			goto found; \
+		else \
+			i++;
+#include "kmalloc_sizes.h"
+#undef CACHE
+		{
+			extern void __you_cannot_kmalloc_that_much(void);
+			__you_cannot_kmalloc_that_much();
+		}
+found:
+		return kmem_cache_alloc_node((flags & GFP_DMA) ?
+			malloc_sizes[i].cs_dmacachep :
+			malloc_sizes[i].cs_cachep, flags, node);
+	}
+	return __kmalloc_node(size, flags, node);
+}
+
+#endif	/* CONFIG_NUMA */
+
+#endif	/* _LINUX_SLAB_DEF_H */

mm/slob.c

@@ -157,7 +157,7 @@ static int fastcall find_order(int size)
 	return order;
 }
 
-void *kmalloc(size_t size, gfp_t gfp)
+void *__kmalloc(size_t size, gfp_t gfp)
 {
 	slob_t *m;
 	bigblock_t *bb;
@@ -186,8 +186,7 @@ void *kmalloc(size_t size, gfp_t gfp)
 	slob_free(bb, sizeof(bigblock_t));
 	return 0;
 }
-
-EXPORT_SYMBOL(kmalloc);
+EXPORT_SYMBOL(__kmalloc);
 
 void kfree(const void *block)
 {
@@ -329,6 +328,17 @@ EXPORT_SYMBOL(kmem_cache_name);
 static struct timer_list slob_timer = TIMER_INITIALIZER(
 	(void (*)(unsigned long))kmem_cache_init, 0, 0);
 
+int kmem_cache_shrink(struct kmem_cache *d)
+{
+	return 0;
+}
+EXPORT_SYMBOL(kmem_cache_shrink);
+
+int kmem_ptr_validate(struct kmem_cache *a, void *b)
+{
+	return 0;
+}
+
 void kmem_cache_init(void)
 {
 	void *p = slob_alloc(PAGE_SIZE, 0, PAGE_SIZE-1);