slab: introduce krealloc

This introduce krealloc() that reallocates memory while keeping the contents
unchanged.  The allocator avoids reallocation if the new size fits the
currently used cache.  I also added a simple non-optimized version for
mm/slob.c for compatibility.

[akpm@linux-foundation.org: fix warnings]
Acked-by: Josef Sipek <jsipek@fsl.cs.sunysb.edu>
Acked-by: Matt Mackall <mpm@selenic.com>
Acked-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 1ef822e..2f8f60f 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -72,8 +72,9 @@
  */
 void *__kmalloc(size_t, gfp_t);
 void *__kzalloc(size_t, gfp_t);
+void * __must_check krealloc(const void *, size_t, gfp_t);
 void kfree(const void *);
-unsigned int ksize(const void *);
+size_t ksize(const void *);
 
 /**
  * kcalloc - allocate memory for an array. The memory is set to zero.