Index: lib/libc/sys/fspacectl.2
===================================================================
--- lib/libc/sys/fspacectl.2
+++ lib/libc/sys/fspacectl.2
@@ -27,7 +27,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd August 4, 2021
+.Dd August 18, 2021
 .Dt FSPACECTL 2
 .Os
 .Sh NAME
@@ -67,6 +67,12 @@
 .Fa spacectl_range
 structure it points to is updated to contain the unprocessed operation range
 after the system call returns.
+If
+.Fa "rmsr->r_len"
+is zero after the system call returns success,
+.Fa "rmsr->r_offset"
+should be ignored.
+The file descriptor's file offset is not used or modified by the system call.
 Both
 .Fa rqsr
 and
@@ -92,9 +98,9 @@
 .Fa rqsr
 argument.
 The
-.Va "rqsr->r_offset"
+.Fa "rqsr->r_offset"
 has to be a value greater than or equal to 0, and the
-.Va "rqsr->r_len"
+.Fa "rqsr->r_len"
 has to be a value greater than 0.
 .Pp
 If the file system supports hole-punching,
@@ -137,6 +143,12 @@
 .Fa "range->r_len"
 argument was less than or equal to zero.
 .It Bq Er EINVAL
+The value of
+.Fa "range->r_offset" +
+.Fa "range->r_len"
+is greater than
+.Dv OFF_MAX .
+.It Bq Er EINVAL
 An invalid or unsupported flag is included in
 .Fa flags .
 .It Bq Er EINVAL
Index: sys/kern/vfs_default.c
===================================================================
--- sys/kern/vfs_default.c
+++ sys/kern/vfs_default.c
@@ -1186,7 +1186,8 @@
 			break;
 	}
 out:
-	*ap->a_offset = offset;
+	if (error != 0 || len != 0)
+		*ap->a_offset = offset;
 	*ap->a_len = len;
 	return (error);
 }