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>

1 files changed, 34 insertions, 1 deletions

diff --git a/mm/slob.c b/mm/slob.c
index 5adc29cb58d..03cce3d3d98 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -190,6 +190,39 @@ void *__kmalloc(size_t size, gfp_t gfp)
 }
 EXPORT_SYMBOL(__kmalloc);
 
+/**
+ * krealloc - reallocate memory. The contents will remain unchanged.
+ *
+ * @p: object to reallocate memory for.
+ * @new_size: how many bytes of memory are required.
+ * @flags: the type of memory to allocate.
+ *
+ * The contents of the object pointed to are preserved up to the
+ * lesser of the new and old sizes.  If @p is %NULL, krealloc()
+ * behaves exactly like kmalloc().  If @size is 0 and @p is not a
+ * %NULL pointer, the object pointed to is freed.
+ */
+void *krealloc(const void *p, size_t new_size, gfp_t flags)
+{
+	void *ret;
+
+	if (unlikely(!p))
+		return kmalloc_track_caller(new_size, flags);
+
+	if (unlikely(!new_size)) {
+		kfree(p);
+		return NULL;
+	}
+
+	ret = kmalloc_track_caller(new_size, flags);
+	if (ret) {
+		memcpy(ret, p, min(new_size, ksize(p)));
+		kfree(p);
+	}
+	return ret;
+}
+EXPORT_SYMBOL(krealloc);
+
 void kfree(const void *block)
 {
 	bigblock_t *bb, **last = &bigblocks;
@@ -219,7 +252,7 @@ void kfree(const void *block)
 
 EXPORT_SYMBOL(kfree);
 
-unsigned int ksize(const void *block)
+size_t ksize(const void *block)
 {
 	bigblock_t *bb;
 	unsigned long flags;