[PATCH v1.1 02/40] libxfs: port various kernel apis from 7.0

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

Port more kernel APIs from Linux, as of version 7.0.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
v1.1: add rvb, clarify the commit message
---
 include/kmem.h |   50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/include/kmem.h b/include/kmem.h
index 66f8b1fbea8fdf..2c276e929c4808 100644
--- a/include/kmem.h
+++ b/include/kmem.h
@@ -61,6 +61,56 @@ static inline void *kmalloc(size_t size, gfp_t flags)
 #define kzalloc(size, gfp)	kvmalloc((size), (gfp) | __GFP_ZERO)
 #define kvzalloc(size, gfp)	kzalloc((size), (gfp))
 
+/**
+ * kmalloc_array - allocate memory for an array.
+ * @n: number of elements.
+ * @size: element size.
+ * @flags: the type of memory to allocate (see kmalloc).
+ */
+static inline void *kmalloc_array(size_t n, size_t size, gfp_t flags)
+{
+	size_t bytes;
+
+	if (unlikely(check_mul_overflow(n, size, &bytes)))
+		return NULL;
+	return kmalloc(bytes, flags);
+}
+#define kcalloc(n, size, gfp)	kmalloc_array((n), (size), (gfp) | __GFP_ZERO)
+
+/**
+ * size_mul() - Calculate size_t multiplication with saturation at SIZE_MAX
+ * @factor1: first factor
+ * @factor2: second factor
+ *
+ * Returns: calculate @factor1 * @factor2, both promoted to size_t,
+ * with any overflow causing the return value to be SIZE_MAX. The
+ * lvalue must be size_t to avoid implicit type conversion.
+ */
+static inline size_t __must_check size_mul(size_t factor1, size_t factor2)
+{
+	size_t bytes;
+
+	if (check_mul_overflow(factor1, factor2, &bytes))
+		return SIZE_MAX;
+
+	return bytes;
+}
+
+#define __alloc_objs(KMALLOC, GFP, TYPE, COUNT)				\
+({									\
+	const size_t __obj_size = size_mul(sizeof(TYPE), COUNT);	\
+	(TYPE *)KMALLOC(__obj_size, GFP);				\
+})
+
+/* Helper macro to avoid gfp flags if they are the default one */
+#define __default_gfp(a,b,...) b
+#define default_gfp(...) __default_gfp(,##__VA_ARGS__,GFP_KERNEL)
+
+#define kzalloc_obj(P, ...) \
+	__alloc_objs(kzalloc, default_gfp(__VA_ARGS__), typeof(P), 1)
+#define kmalloc_obj(VAR_OR_TYPE, ...) \
+	__alloc_objs(kmalloc, default_gfp(__VA_ARGS__), typeof(VAR_OR_TYPE), 1)
+
 static inline void kfree(const void *ptr)
 {
 	free((void *)ptr);