g_journal_ufs_using_last_sector() needs minor correction (patch included)

[Andreas Longwitz]

On a testdisk created with

  dd if=/dev/zero of=diskfile count=5000 bs=1m
  mdconfig -a -t vnode -f diskfile -u 1

let us create a mirrored and gjournaled filesystem:

gmirror label -b prefer -F gmX md1
gpart create -s GPT mirror/gmX
gpart add -t freebsd-swap -s 4194304 -i 1 mirror/gmX
gpart add -t freebsd-ufs -i 2 mirror/gmX
gjournal label mirror/gmXp2 mirror/gmXp1
newfs -J /dev/mirror/gmXp2.journal
mount /dev/mirror/gmXp2.journal /mnt
...  put some data to /mnt
umount /mnt

The mediasizes in sectors for gjournal consumer and provider:

diskinfo /dev/mirror/gmXp2.journal -->
/dev/mirror/gmXp2.journal     512     3095361024      6045627 0    0

dumpfs -m /dev/mirror/gmXp2.journal -->
# newfs command for /dev/mirror/gmXp2.journal
newfs -O 2 -J -a 8 -b 16384 -d 16384 -e 2048 -f 2048 -g 16384 -h 64
-m 8 -o time -s 6045624 /dev/mirror/gmXp2.journal

The size of the created filesystem is 6045624 and three blocks less than
the size gjournal provides.

Now I had the need to rename gmX to gmY without loosing my data:

gjournal stop mirror/gmXp2.journal
gjournal clear mirror/gmXp2
gjournal clear mirror/gmXp1
gpart delete -i 1 mirror/gmX
gpart delete -i 2 mirror/gmX
gpart destroy mirror/gmX
gmirror stop gmX
gmirror clear /dev/md1
gmirror label -b prefer -F gmY md1
gpart create -s GPT mirror/gmY
gpart add -t freebsd-swap -s 4194304 -i 1 mirror/gmY
gpart add -t freebsd-ufs -i 2 mirror/gmY
gjournal label mirror/gmYp2 mirror/gmYp1

At this point gjournal gives the unjustified error message
"File system on mirror/gmYp2 is using the last
sector and this operation is going to overwrite
it. Use -f if you really want to do it."

the reason for this is an improper size check in the function
g_journal_ufs_using_last_sector() which can be corrected by the
following patch:

--- geom_journal_ufs.c.orig     2009-08-03 10:13:06.000000000 +0200
+++ geom_journal_ufs.c  2013-01-02 23:01:37.000000000 +0100
@@ -73,6 +73,6 @@
        /* Provider size in 512 bytes blocks. */
        psize = g_get_mediasize(prov) / DEV_BSIZE;
        /* File system size in 512 bytes blocks. */
-       fssize = fsbtodb(fs, dbtofsb(fs, psize));
-       return (psize == fssize);
+       fssize = fsbtodb(fs, fs->fs_size);
+       return (psize <= fssize);
 }


-- 
Andreas Longwitz