[dm-devel] 2.6.8.1: try to create snapshot w/o dm-snapshot.ko loaded makes system unusable

[Daniel Risacher]

Minor bug: if one attempts to create a snapshot without the
dm-snapshot module loaded, the system gets "hosed up" rather than just
reporting an error.

I did this: sudo lvcreate --size 100m --snapshot --name snap /dev/vg2/home

I then got an error that I didn't have snapshot support loaded, so I
loaded it (modprobe dm-snapshot) and tried again.  I then got an error
that the 'snap' volume already existed.  Sometime around then, the
/home partition became unusable, and any process that attempted to
access it became unresponsive.   I used Alt-SysRq to reboot.

On reboot, both /dev/vg2/home and /dev/vg2/snap existed and were
inactive.  I vgremove'd /dev/vg2/snap, activated /dev/vg2/home, fsck'd
it, and went on my way.  Snapshot support appears to work great once
the module is loaded.

Dan R
-----

vgdisplay --version
  LVM version:     2.00.16 (2004-05-24)
  Library version: 1.00.19-ioctl (2004-07-03)
  Driver version:  4.1.0

/usr/src/linux/scripts/ver_linux
Linux m5 2.6.8.1 #5 SMP Tue Aug 17 05:33:16 EDT 2004 i686 GNU/Linux
 
Gnu C                  3.3.4
Gnu make               3.80
binutils               2.14.90.0.7
util-linux             2.12
mount                  2.12a
module-init-tools      3.1-pre5
e2fsprogs              1.35
jfsutils               1.1.6
pcmcia-cs              3.2.5
nfs-utils              1.0.6
Linux C Library        2.3.2
Dynamic linker (ldd)   2.3.2
Procps                 3.2.1
Net-tools              1.60
Console-tools          0.2.3
Sh-utils               5.2.1
Modules Loaded         dm_snapshot mga nfsd exportfs ipt_LOG ipt_state ipt_MASQUERADE iptable_nat ipt_TCPMSS iptable_mangle iptable_filter ip_tables ip_conntrack_irc ip_conntrack_ftp ip_conntrack eeprom w83781d i2c_sensor i2c_amd756 i2c_core md5 ipv6 ppp_async crc_ccitt ppp_generic slhc bridge sd_mod usb_storage hci_usb bluetooth eth1394 snd_cmipci snd_pcm_oss snd_mixer_oss snd_pcm snd_page_alloc snd_opl3_lib snd_timer snd_hwdep gameport snd_mpu401_uart snd_rawmidi snd_seq_device snd soundcore ohci1394 ieee1394 ohci_hcd usbcore dm_mod