diff --git a/man2/setfsuid.2 b/man2/setfsuid.2
index 8918af37e..ba6ad7964 100644
--- a/man2/setfsuid.2
+++ b/man2/setfsuid.2
@@ -1,4 +1,5 @@
 .\" Copyright (C) 1995, Thomas K. Dyas <tdyas@eden.rutgers.edu>
+.\" and Copyright (C) 2013, 2019, Michael Kerrisk <mtk.manpages@gmail.com>
 .\"
 .\" %%%LICENSE_START(VERBATIM)
 .\" Permission is granted to make and distribute verbatim copies of this
@@ -36,29 +37,34 @@ setfsuid \- set user identity used for filesystem checks
 .PP
 .BI "int setfsuid(uid_t " fsuid );
 .SH DESCRIPTION
-The system call
+On Linux, a process has both a filesystem user ID and an effective user ID.
+The (Linux-specific) filesystem user ID is used
+for permissions checking when accessing filesystem objects,
+while the effective user ID is used for various other kinds
+of permissions checks (see
+.BR credentials (7)).
+.PP
+Normally, the value of the process's filesystem user ID
+is the same as the value of its effective user ID.
+This is so, because whenever a process's effective user ID is changed,
+the kernel also changes the filesystem user ID to be the same as
+the new value of the effective user ID.
+A process can cause the value of its filesystem user ID to diverge
+from its effective user ID by using
 .BR setfsuid ()
-changes the value of the caller's filesystem user ID\(emthe
-user ID that the Linux kernel uses to check for all accesses
-to the filesystem.
-Normally, the value of
-the filesystem user ID
-will shadow the value of the effective user ID.
-In fact, whenever the
-effective user ID is changed,
-the filesystem user ID
-will also be changed to the new value of the effective user ID.
+to change its filesystem user ID to the value given in
+.IR fsuid .
 .PP
 Explicit calls to
 .BR setfsuid ()
 and
 .BR setfsgid (2)
-are usually used only by programs such as the Linux NFS server that
+are (were) usually used only by programs such as the Linux NFS server that
 need to change what user and group ID is used for file access without a
 corresponding change in the real and effective user and group IDs.
 A change in the normal user IDs for a program such as the NFS server
-is a security hole that can expose it to unwanted signals.
-(But see below.)
+is (was) a security hole that can expose it to unwanted signals.
+(However, this issue is historical; see below.)
 .PP
 .BR setfsuid ()
 will succeed only if the caller is the superuser or if