From 3f6f17ee1e1ea826cd2be78508759063dcb0b9f0 Mon Sep 17 00:00:00 2001
From: Julian Elischer <julian@FreeBSD.org>
Date: Wed, 13 Nov 1996 01:45:56 +0000
Subject: [PATCH] Submitted by: Archie and me.

We encountered an interesting situation where the superblock for
a file system got written to disk with the "fs_fmod" flag set to
one. It appears that this flag is normally supposed to be cleared
during ffs_sync(), but we experienced a crash, or some other weird
occurrence that left it on the disk set to 1.

Later this partition was mounted read-only... and the fs_fmod
field was never cleared, causing ffs_sync() to panic "rofs mod"
when trying to unmount that filesystem (ffs_vfsops.c: line 790).

fix:
set this bit to 0 when you load the superblock from disk.
(see more complete mail on this to hackers)
---
 sys/ufs/ffs/ffs_vfsops.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sys/ufs/ffs/ffs_vfsops.c b/sys/ufs/ffs/ffs_vfsops.c
index a35502a8e0a0..e7850860f9e5 100644
--- a/sys/ufs/ffs/ffs_vfsops.c
+++ b/sys/ufs/ffs/ffs_vfsops.c
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)ffs_vfsops.c	8.8 (Berkeley) 4/18/94
- * $Id: ffs_vfsops.c,v 1.40 1996/08/21 21:56:09 dyson Exp $
+ * $Id: ffs_vfsops.c,v 1.41 1996/09/07 17:34:57 dyson Exp $
  */
 
 #include "opt_quota.h"
@@ -383,6 +383,7 @@ ffs_reload(mp, cred, p)
 	if (error)
 		return (error);
 	fs = (struct fs *)bp->b_data;
+	fs->fs_fmod = 0;
 	if (fs->fs_magic != FS_MAGIC || fs->fs_bsize > MAXBSIZE ||
 	    fs->fs_bsize < sizeof(struct fs)) {
 		brelse(bp);
@@ -511,6 +512,7 @@ ffs_mountfs(devvp, mp, p)
 		error = EINVAL;		/* XXX needs translation */
 		goto out;
 	}
+	fs->fs_fmod = 0;
 	if (!fs->fs_clean) {
 		if (ronly || (mp->mnt_flag & MNT_FORCE)) {
 			printf("WARNING: %s was not properly dismounted.\n",fs->fs_fsmnt);