mm: Implement no-MMU variant of vmalloc_user_node_flags

To fix build with !CONFIG_MMU, implement it for no-MMU configurations as well.

Fixes: fc9702273e ("bpf: Add mmap() support for BPF_MAP_TYPE_ARRAY")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20191123220835.1237773-1-andriin@fb.com

mm/nommu.c

@@ -155,11 +155,11 @@ void *__vmalloc_node_flags(unsigned long size, int node, gfp_t flags)
 	return __vmalloc(size, flags, PAGE_KERNEL);
 }
 
-void *vmalloc_user(unsigned long size)
+static void *__vmalloc_user_flags(unsigned long size, gfp_t flags)
 {
 	void *ret;
 
-	ret = __vmalloc(size, GFP_KERNEL | __GFP_ZERO, PAGE_KERNEL);
+	ret = __vmalloc(size, flags, PAGE_KERNEL);
 	if (ret) {
 		struct vm_area_struct *vma;
 
@@ -172,8 +172,19 @@ void *vmalloc_user(unsigned long size)
 
 	return ret;
 }
+
+void *vmalloc_user(unsigned long size)
+{
+	return __vmalloc_user_flags(size, GFP_KERNEL | __GFP_ZERO);
+}
 EXPORT_SYMBOL(vmalloc_user);
 
+void *vmalloc_user_node_flags(unsigned long size, int node, gfp_t flags)
+{
+	return __vmalloc_user_flags(size, flags | __GFP_ZERO);
+}
+EXPORT_SYMBOL(vmalloc_user_node_flags);
+
 struct page *vmalloc_to_page(const void *addr)
 {
 	return virt_to_page(addr);