update write(2)'s iovec limit w/ info about the iosize_max_clamp sysctl...

lib/libc/sys/write.2

@@ -28,7 +28,7 @@
 .\"     @(#)write.2	8.5 (Berkeley) 4/2/94
 .\" $FreeBSD$
 .\"
-.Dd March 30, 2020
+.Dd October 25, 2020
 .Dt WRITE 2
 .Os
 .Sh NAME
@@ -240,9 +240,13 @@ array was negative.
 .It Bq Er EINVAL
 The sum of the
 .Fa iov_len
-values in the
-.Fa iov
-array overflowed a 32-bit integer.
+values is greater than
+.Dv SSIZE_MAX
+(or greater than
+.Dv INT_MAX ,
+if the sysctl
+.Va debug.iosize_max_clamp
+is non-zero).
 .It Bq Er ENOBUFS
 The mbuf pool has been completely exhausted when writing to a socket.
 .El