linux/fs.h: move member alignment check next to definition of struct filename

Instead of doing this compile-time check in some slightly arbitrary user
of struct filename, put it next to the definition.

Link: http://lkml.kernel.org/r/20190208203015.29702-3-linux@rasmusvillemoes.dk
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Kees Cook <keescook@chromium.org>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/namei.c

@@ -39,7 +39,6 @@
 #include <linux/bitops.h>
 #include <linux/init_task.h>
 #include <linux/uaccess.h>
-#include <linux/build_bug.h>
 
 #include "internal.h"
 #include "mount.h"
@@ -131,7 +130,6 @@ getname_flags(const char __user *filename, int flags, int *empty)
 	struct filename *result;
 	char *kname;
 	int len;
-	BUILD_BUG_ON(offsetof(struct filename, iname) % sizeof(long) != 0);
 
 	result = audit_reusename(filename);
 	if (result)

include/linux/fs.h

@@ -37,6 +37,8 @@
 #include <linux/uuid.h>
 #include <linux/errseq.h>
 #include <linux/ioprio.h>
+#include <linux/build_bug.h>
+#include <linux/stddef.h>
 
 #include <asm/byteorder.h>
 #include <uapi/linux/fs.h>
@@ -2493,6 +2495,7 @@ struct filename {
 	struct audit_names	*aname;
 	const char		iname[];
 };
+static_assert(offsetof(struct filename, iname) % sizeof(long) == 0);
 
 extern long vfs_truncate(const struct path *, loff_t);
 extern int do_truncate(struct dentry *, loff_t start, unsigned int time_attrs,