diff --git a/share/man/man9/vnode_pager_setsize.9 b/share/man/man9/vnode_pager_setsize.9
index c59a01796f20..0dc3b2057930 100644
--- a/share/man/man9/vnode_pager_setsize.9
+++ b/share/man/man9/vnode_pager_setsize.9
@@ -1,74 +1,79 @@
 .\"
 .\" SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 .\"
 .\" Copyright (c) 2021 The FreeBSD Foundation
 .\"
 .\" Portions of this software were developed by Ka Ho Ng
 .\" under sponsorship from the FreeBSD Foundation.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
 .\" modification, are permitted provided that the following conditions
 .\" are met:
 .\" 1. Redistributions of source code must retain the above copyright
 .\"    notice, this list of conditions and the following disclaimer.
 .\" 2. Redistributions in binary form must reproduce the above copyright
 .\"    notice, this list of conditions and the following disclaimer in the
 .\"    documentation and/or other materials provided with the distribution.
 .\"
 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd April 6, 2021
+.Dd April 8, 2021
 .Dt VNODE_PAGER_SETSIZE 9
 .Os
 .Sh NAME
 .Nm vnode_pager_setsize
 .Nd "notify the VM system about updates in the file size"
 .Sh SYNOPSIS
 .In sys/param.h
 .In vm/vm.h
 .In vm/vm_extern.h
 .Ft void
 .Fn vnode_pager_setsize "struct vnode *vp" "vm_ooffset_t nsize"
 .Sh DESCRIPTION
 .Nm
-lets the VM system know about a change in size for a file.
-Content beyond the new EOF specified by the
-.Fa nsize
-argument will be purged from the cache.
-This function is useful for use within file system code to implement
-truncation in
-.Xr VOP_SETATTR 9 .
-.Sh IMPLEMENTATION NOTES
+lets the VM system know about a change in size for a file,
+and updates the object size and vnode pager size of the vm object in
+.Fa vp
+with
+.Fa nsize .
+Page faults on the object mapping with offset beyond the new object
+size results in
+.Va SIGBUS .
+.Pp
+Pages between the old EOF and the new EOF are removed from the object queue
+if the file size shrinks.
 In case the new EOF specified by the
 .Fa nsize
-argument is not aligned to page boundaries,
-partial-page area starting beyond the EOF will be zeroed.
-In partial-page area,
-for content occupying whole blocks within block
-boundaries,
-the dirty bits for the corresponding blocks will be cleared.
-.Sh LOCKING
-Writer lock of the VM object of
+argument is not aligned to page boundary,
+partial-page area starting beyond the EOF is zeroed and marked invalid.
+if the page exists resident.
+.Pp
+In case the vnode
 .Fa vp
-will be held within the function.
+does not have a VM object allocated, the effect of calling this function is no-op.
+.Pp
+This function must be used within file system code to implement truncation
+if the file system allocates vm objects for vnodes.
+.Sh LOCKS
+The vnode should be exclusively locked on entry and will still be locked on exit.
 .Sh SEE ALSO
 .Xr vnode 9
 .Sh HISTORY
 The
 .Nm
 manual page first appeared in
 .Fx 14 .
 .Sh AUTHORS
 This
 manual page was written by
 .An Ka Ho Ng Aq Mt khng@FreeBSD.org .