From c31480a1f66537e59b02e935a547bcfc76715278 Mon Sep 17 00:00:00 2001
From: Konstantin Belousov <kib@FreeBSD.org>
Date: Mon, 15 Feb 2021 05:36:02 +0200
Subject: [PATCH] UFS snapshots: properly set the vm object size.

Citing Kirk:
The previous code [before 8563de2f2799b2cb -- kib] did not call
vnode_pager_setsize() but worked because later in ffs_snapshot() it
does a UFS_WRITE() to output the snaplist. Previously the UFS_WRITE()
allocated the extra block at the end of the file which caused it to do
the needed vnode_pager_setsize(). But the new code had already allocated
the extra block, so UFS_WRITE() did not extend the size and thus did not
do the vnode_pager_setsize().

PR:	253158
Reported by:	Harald Schmalzbauer <bugzilla.freebsd@omnilan.de>
Reviewed by:	mckusick
Tested by:	cy
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
---
 sys/ufs/ffs/ffs_snapshot.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/sys/ufs/ffs/ffs_snapshot.c b/sys/ufs/ffs/ffs_snapshot.c
index 8f0adde6f5e4..6da84fb46bb0 100644
--- a/sys/ufs/ffs/ffs_snapshot.c
+++ b/sys/ufs/ffs/ffs_snapshot.c
@@ -59,6 +59,9 @@ __FBSDID("$FreeBSD$");
 #include <sys/rwlock.h>
 #include <sys/vnode.h>
 
+#include <vm/vm.h>
+#include <vm/vm_extern.h>
+
 #include <geom/geom.h>
 
 #include <ufs/ufs/extattr.h>
@@ -328,6 +331,7 @@ ffs_snapshot(mp, snapfile)
 		goto out;
 	bawrite(bp);
 	ip->i_size = lblktosize(fs, (off_t)(numblks + 1));
+	vnode_pager_setsize(vp, ip->i_size);
 	DIP_SET(ip, i_size, ip->i_size);
 	UFS_INODE_SET_FLAG(ip, IN_SIZEMOD | IN_CHANGE | IN_UPDATE);
 	/*