Subject: Re: [PATCH] mlx4: Use kernel sizeof and alloc styles

From: Joe Perches <[email-masked]>
Date: Sun, 04 Dec 2016 14:56:32 -0800

On Sun, 2016-12-04 at 12:58 -0800, Eric Dumazet wrote:
> On Sun, 2016-12-04 at 12:11 -0800, Joe Perches wrote:
> > Convert sizeof foo to sizeof(foo) and allocations with multiplications
> > to the appropriate kcalloc/kmalloc_array styles.
> > 
> > Signed-off-by: Joe Perches <[email-masked]>
> > ---
> 
> Gah.
> 
> This is one of the hotest NIC driver on linux at this moment, 
> with XDP and other efforts going on.
> 
> Some kmalloc() are becoming kmalloc_node() in some dev branches, and
> there is no kmalloc_array_node() yet.

Well that kmalloc_array_node, like this patch, is pretty trivial to add.
Something like the attached for kmalloc_array_node and kcalloc_node.

> This kind of patch is making rebases/backports very painful.

That's really not an issue for me.

> Could we wait ~6 months before doing such cleanup/changes please ?

This is certainly a trivial patch that could be
done at almost any time.

> If you believe a bug needs a fix, please send a patch to address it.
> 
> Thanks.

No worries.

 include/linux/slab.h | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 084b12bad198..d98c07713c03 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -647,6 +647,37 @@ static inline void *kzalloc_node(size_t size, gfp_t flags, int node)
 	return kmalloc_node(size, flags | __GFP_ZERO, node);
 }
 
+/**
+ * kmalloc_array_node - allocate memory for an array
+ * from a particular memory node.
+ * @n: number of elements.
+ * @size: element size.
+ * @flags: the type of memory to allocate (see kmalloc).
+ * @node: memory node from which to allocate
+ */
+static inline void *kmalloc_array_node(size_t n, size_t size, gfp_t flags,
+				       int node)
+{
+	if (size != 0 && n > SIZE_MAX / size)
+		return NULL;
+	if (__builtin_constant_p(n) && __builtin_constant_p(size))
+		return kmalloc_node(n * size, flags, node);
+	return __kmalloc_node(n * size, flags, node);
+}
+
+/**
+ * kcalloc_node - allocate memory for an array from a particular memory node.
+ * The memory is set to zero.
+ * @n: number of elements.
+ * @size: element size.
+ * @flags: the type of memory to allocate (see kmalloc).
+ * @node: memory node from which to allocate
+ */
+static inline void *kcalloc_node(size_t n, size_t size, gfp_t flags, int node)
+{
+	return kmalloc_array_node(n, size, flags | __GFP_ZERO, node);
+}
+
 unsigned int kmem_cache_size(struct kmem_cache *s);
 void __init kmem_cache_init_late(void);