mm: vmalloc: introduce array allocation functions

Linux has dozens of occurrences of vmalloc(array_size()) and
vzalloc(array_size()). Allow to simplify the code by providing
vmalloc_array and vcalloc, as well as the underscored variants that let
the caller specify the GFP flags.

Acked-by: Michal Hocko <[e-mail]>
Signed-off-by: Paolo Bonzini <[e-mail]>

include/linux/vmalloc.h

···
 		int node, const void *caller) __alloc_size(1);
 void *vmalloc_no_huge(unsigned long size) __alloc_size(1);
 
+extern void *__vmalloc_array(size_t n, size_t size, gfp_t flags) __alloc_size(1, 2);
+extern void *vmalloc_array(size_t n, size_t size) __alloc_size(1, 2);
+extern void *__vcalloc(size_t n, size_t size, gfp_t flags) __alloc_size(1, 2);
+extern void *vcalloc(size_t n, size_t size) __alloc_size(1, 2);
+
 extern void vfree(const void *addr);
 extern void vfree_atomic(const void *addr);
 

mm/util.c

···
 }
 EXPORT_SYMBOL(kvrealloc);
 
+/**
+ * __vmalloc_array - allocate memory for a virtually contiguous array.
+ * @n: number of elements.
+ * @size: element size.
+ * @flags: the type of memory to allocate (see kmalloc).
+ */
+void *__vmalloc_array(size_t n, size_t size, gfp_t flags)
+{
+	size_t bytes;
+
+	if (unlikely(check_mul_overflow(n, size, &bytes)))
+		return NULL;
+	return __vmalloc(bytes, flags);
+}
+EXPORT_SYMBOL(__vmalloc_array);
+
+/**
+ * vmalloc_array - allocate memory for a virtually contiguous array.
+ * @n: number of elements.
+ * @size: element size.
+ */
+void *vmalloc_array(size_t n, size_t size)
+{
+	return __vmalloc_array(n, size, GFP_KERNEL);
+}
+EXPORT_SYMBOL(vmalloc_array);
+
+/**
+ * __vcalloc - allocate and zero memory for a virtually contiguous array.
+ * @n: number of elements.
+ * @size: element size.
+ * @flags: the type of memory to allocate (see kmalloc).
+ */
+void *__vcalloc(size_t n, size_t size, gfp_t flags)
+{
+	return __vmalloc_array(n, size, flags | __GFP_ZERO);
+}
+EXPORT_SYMBOL(__vcalloc);
+
+/**
+ * vcalloc - allocate and zero memory for a virtually contiguous array.
+ * @n: number of elements.
+ * @size: element size.
+ */
+void *vcalloc(size_t n, size_t size)
+{
+	return __vmalloc_array(n, size, GFP_KERNEL | __GFP_ZERO);
+}
+EXPORT_SYMBOL(vcalloc);
+
 /* Neutral page->mapping pointer to address_space or anon_vma or other */
 void *page_rmapping(struct page *page)
 {