Use alternative, less messy solution to avoid breakage after r223020:

put the snapdata structure between #ifdef _KERNEL guards.

Suggested by:	kib

sys/ufs/ffs/ffs_extern.h

@@ -166,6 +166,7 @@ void	softdep_freework(struct workhead *);
 
 int	ffs_rdonly(struct inode *);
 
+#ifdef _KERNEL
 TAILQ_HEAD(snaphead, inode);
 
 struct snapdata {
@@ -175,5 +176,6 @@ struct snapdata {
 	daddr_t *sn_blklist;
 	struct lock sn_lock;
 };
+#endif /* _KERNEL */
 
 #endif /* !_UFS_FFS_EXTERN_H */

usr.sbin/makefs/ffs/ffs_bswap.c

@@ -34,9 +34,6 @@
 __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
-#include <sys/queue.h>
-#include <sys/lock.h>
-#include <sys/lockmgr.h>
 #if defined(_KERNEL)
 #include <sys/systm.h>
 #endif

usr.sbin/makefs/ffs/ffs_subr.c

@@ -35,9 +35,6 @@
 __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
-#include <sys/queue.h>
-#include <sys/lock.h>
-#include <sys/lockmgr.h>
 
 #include <ufs/ufs/dinode.h>
 #include <ufs/ffs/fs.h>