[PATCH] slab: introduce kmem_cache_zalloc allocator

Introduce a memory-zeroing variant of kmem_cache_alloc.  The allocator
already exits in XFS and there are potential users for it so this patch
makes the allocator available for the general public.

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 29 insertions, 0 deletions

diff --git a/include/linux/slab.h b/include/linux/slab.h
index f88e08a..1216b09 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -64,6 +64,7 @@ extern kmem_cache_t *kmem_cache_create(const char *, size_t, size_t, unsigned lo
 extern int kmem_cache_destroy(kmem_cache_t *);
 extern int kmem_cache_shrink(kmem_cache_t *);
 extern void *kmem_cache_alloc(kmem_cache_t *, gfp_t);
+extern void *kmem_cache_zalloc(struct kmem_cache *, gfp_t);
 extern void kmem_cache_free(kmem_cache_t *, void *);
 extern unsigned int kmem_cache_size(kmem_cache_t *);
 extern const char *kmem_cache_name(kmem_cache_t *);
@@ -156,6 +157,7 @@ struct kmem_cache *kmem_cache_create(const char *c, size_t, size_t,
 	void (*)(void *, struct kmem_cache *, unsigned long));
 int kmem_cache_destroy(struct kmem_cache *c);
 void *kmem_cache_alloc(struct kmem_cache *c, gfp_t flags);
+void *kmem_cache_zalloc(struct kmem_cache *, gfp_t);
 void kmem_cache_free(struct kmem_cache *c, void *b);
 const char *kmem_cache_name(struct kmem_cache *);
 void *kmalloc(size_t size, gfp_t flags);
diff --git a/mm/slab.c b/mm/slab.c
index a504716..6f5aeeb 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3108,6 +3108,23 @@ void *kmem_cache_alloc(struct kmem_cache *cachep, gfp_t flags)
 EXPORT_SYMBOL(kmem_cache_alloc);
 
 /**
+ * kmem_cache_alloc - Allocate an object. The memory is set to zero.
+ * @cache: The cache to allocate from.
+ * @flags: See kmalloc().
+ *
+ * Allocate an object from this cache and set the allocated memory to zero.
+ * The flags are only relevant if the cache has no available objects.
+ */
+void *kmem_cache_zalloc(struct kmem_cache *cache, gfp_t flags)
+{
+	void *ret = __cache_alloc(cache, flags, __builtin_return_address(0));
+	if (ret)
+		memset(ret, 0, obj_size(cache));
+	return ret;
+}
+EXPORT_SYMBOL(kmem_cache_zalloc);
+
+/**
  * kmem_ptr_validate - check if an untrusted pointer might
  *	be a slab entry.
  * @cachep: the cache we're checking against
diff --git a/mm/slob.c b/mm/slob.c
index a1f42bd..9bcc7e2 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -294,6 +294,16 @@ void *kmem_cache_alloc(struct kmem_cache *c, gfp_t flags)
 }
 EXPORT_SYMBOL(kmem_cache_alloc);
 
+void *kmem_cache_zalloc(struct kmem_cache *c, gfp_t flags)
+{
+	void *ret = kmem_cache_alloc(c, flags);
+	if (ret)
+		memset(ret, 0, c->size);
+
+	return ret;
+}
+EXPORT_SYMBOL(kmem_cache_zalloc);
+
 void kmem_cache_free(struct kmem_cache *c, void *b)
 {
 	if (c->dtor)