diff --git a/sys/fs/fuse/fuse_vnops.c.clone b/sys/fs/fuse/fuse_vnops.c
--- a/sys/fs/fuse/fuse_vnops.c.clone
+++ b/sys/fs/fuse/fuse_vnops.c
@@ -877,6 +877,9 @@
 	pid_t pid;
 	int err;
 
+	if ((ap->a_flags & COPY_FILE_RANGE_CLONE) != 0)
+		return (EXTERROR(ENOSYS, "Cannot clone"));
+
 	if (mp == NULL || mp != vnode_mount(outvp))
 		return (EXTERROR(ENOSYS, "Mount points do not match"));
 
diff --git a/sys/kern/vfs_default.c.clone b/sys/kern/vfs_default.c
--- a/sys/kern/vfs_default.c.clone
+++ b/sys/kern/vfs_default.c
@@ -457,6 +457,7 @@
 		case _PC_NAMEDATTR_ENABLED:
 		case _PC_HAS_NAMEDATTR:
 		case _PC_HAS_HIDDENSYSTEM:
+		case _PC_CLONE_BLKSIZE:
 			*ap->a_retval = 0;
 			return (0);
 		default:
diff --git a/sys/kern/vfs_syscalls.c.clone b/sys/kern/vfs_syscalls.c
--- a/sys/kern/vfs_syscalls.c.clone
+++ b/sys/kern/vfs_syscalls.c
@@ -5053,7 +5053,7 @@
 	error = 0;
 	retlen = 0;
 
-	if (flags != 0) {
+	if ((flags & ~COPY_FILE_RANGE_USERFLAGS) != 0) {
 		error = EINVAL;
 		goto out;
 	}
diff --git a/sys/kern/vfs_vnops.c.clone b/sys/kern/vfs_vnops.c
--- a/sys/kern/vfs_vnops.c.clone
+++ b/sys/kern/vfs_vnops.c
@@ -3443,6 +3443,11 @@
 	interrupted = 0;
 	dat = NULL;
 
+	if ((flags & COPY_FILE_RANGE_CLONE) != 0) {
+		error = ENOSYS;
+		goto out;
+	}
+
 	error = vn_lock(invp, LK_SHARED);
 	if (error != 0)
 		goto out;
diff --git a/sys/sys/unistd.h.clone b/sys/sys/unistd.h
--- a/sys/sys/unistd.h.clone
+++ b/sys/sys/unistd.h
@@ -157,6 +157,7 @@
 #define	_PC_NAMEDATTR_ENABLED	66
 #define	_PC_HAS_NAMEDATTR	67
 #define	_PC_HAS_HIDDENSYSTEM	68
+#define	_PC_CLONE_BLKSIZE	69
 #endif
 
 /* From OpenSolaris, used by SEEK_DATA/SEEK_HOLE. */
diff --git a/sys/sys/vnode.h.clone b/sys/sys/vnode.h
--- a/sys/sys/vnode.h.clone
+++ b/sys/sys/vnode.h
@@ -396,8 +396,21 @@
  * LK_TIMELOCK timeout for vnode locks (used mainly by the pageout daemon)
  */
 #define VLKTIMEOUT	(hz / 20 + 1)
+
+/* copy_file_range flags */
+#define	COPY_FILE_RANGE_KFLAGS		0xff000000
 
+/*
+ * copy_file_range flags visible to user space.
+ * Allocate high bits first, to try and avoid conflicting with Linux.
+ */
+#define	COPY_FILE_RANGE_CLONE		0x00800000	/* Require cloning. */
+#define	COPY_FILE_RANGE_USERFLAGS	(COPY_FILE_RANGE_CLONE)
+
 #ifdef _KERNEL
+
+/* copy_file_range flags only usable in the kernel */
+#define	COPY_FILE_RANGE_TIMEO1SEC	0x01000000	/* Return after 1sec. */
 
 #ifdef MALLOC_DECLARE
 MALLOC_DECLARE(M_VNODE);
@@ -620,10 +633,6 @@
 #define	VN_OPEN_NAMECACHE	0x00000004
 #define	VN_OPEN_INVFS		0x00000008
 #define	VN_OPEN_WANTIOCTLCAPS	0x00000010
-
-/* copy_file_range kernel flags */
-#define	COPY_FILE_RANGE_KFLAGS		0xff000000
-#define	COPY_FILE_RANGE_TIMEO1SEC	0x01000000	/* Return after 1sec. */
 
 /*
  * Public vnode manipulation functions.