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[linux-lvm] LVM Bug, or Human Incompetence?



Hi!  I seem to have found a reproducable way to break LVM.  I'm not sure if
its a bug or simply operator error, so I figured make up a transscript and
let you decide.  The transscript isn't very exciting until the vgextend
part...

This is on my desktop machine, which I'm willing to temporarily break for
debugging purposes, if needed.


# cat /proc/lvm/global
LVM module version 0.9.1_beta2 (18/01/2001)

Total:  1 VG  1 PV  3 LVs (3 LVs open 3 times)

Global: 102973 bytes malloced   IOP version: 10   0:04:17 active

VG:  tweet  [1 PV, 3 LV/3 open]  PE Size: 4096 KB
  Usage [KB/PE]: 39079936 /9541 total  25165824 /6144 used  13914112 /3397 free
  PV:  [AA] hdb                   39079936 /9541    25165824 /6144    13914112 /3397
    LVs: [AWDL  ] music                     20971520 /5120     1x open
         [AWDL  ] home                       2097152 /512      1x open
         [AWDL  ] usr                        2097152 /512      1x open
# mount
/dev/hda3 on / type reiserfs (rw)
proc on /proc type proc (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
/dev/hda1 on /boot type reiserfs (rw,notail)
/dev/tweet/usr on /usr type reiserfs (rw)
/dev/tweet/home on /home type reiserfs (rw)
/dev/tweet/music on /music type reiserfs (rw)
# df
Filesystem            Size  Used Avail Use% Mounted on
/dev/hda3             1.4G  259M  1.1G  19% /
/dev/hda1              47M   37M   10M  78% /boot
/dev/tweet/usr        2.0G  1.1G  949M  54% /usr
/dev/tweet/home       2.0G  875M  1.1G  43% /home
/dev/tweet/music       20G   17G  3.7G  82% /music
# dmesg | grep hda
    ide0: BM-DMA at 0xd000-0xd007, BIOS settings: hda:DMA, hdb:pio
hda: Maxtor 52049U4, ATA DISK drive
hda: 40020624 sectors (20491 MB) w/2048KiB Cache, CHS=2491/255/63, UDMA(33)
 hda: hda1 hda2 hda3 hda4
# cfdisk
                                                            cfdisk 2.11g

                                                        Disk Drive: /dev/hda
                                                      Size: 20490559488 bytes
                                        Heads: 255   Sectors per Track: 63   Cylinders: 2491

      Name                Flags              Part Type        FS Type                     [Label]                  Size (MB)
 ----------------------------------------------------------------------------------------------------------------------------------
      hda1                Boot                Primary         Linux                                                    49.36
      hda4                                    Primary         Linux swap                                              164.51
      hda3                                    Primary         Linux                                                  1497.01
      hda2                                    Primary         Linux LVM                                             18778.32
...
# vgscan -v
vgscan -- removing "/etc/lvmtab" and "/etc/lvmtab.d"
vgscan -- reading all physical volumes (this may take a while...)
vgscan -- scanning for all active volume group(s) first
vgscan -- found active volume group "tweet"
vgscan -- reading data of volume group "tweet" from physical volume(s)
vgscan -- inserting "tweet" into lvmtab
vgscan -- backing up volume group "tweet"
vgscan -- checking volume group name "tweet"
vgscan -- checking volume group consistency of "tweet"
vgscan -- checking existence of "/etc/lvmtab.d"
vgscan -- making directory "/etc/lvmtab.d"
vgscan -- storing volume group data of "tweet" in "/etc/lvmtab.d/tweet.tmp"
vgscan -- storing physical volume data of "tweet" in "/etc/lvmtab.d/tweet.tmp"
vgscan -- storing logical volume data of volume group "tweet" in "/etc/lvmtab.d/tweet.tmp"
vgscan -- renaming "/etc/lvmtab.d/tweet.tmp" to "/etc/lvmtab.d/tweet"
vgscan -- removing special files and directory for volume group "tweet"
vgscan -- creating directory and group character special file for "tweet"
vgscan -- creating block device special files for tweet
vgscan -- "/etc/lvmtab" and "/etc/lvmtab.d" successfully created
vgscan -- WARNING: you may not have an actual VGDA backup of your volume group

# pvscan -v
pvscan -- reading all physical volumes (this may take a while...)
pvscan -- walking through all physical volumes found
pvscan -- ACTIVE   PV "/dev/hdb" of VG "tweet" [37.27 GB / 13.27 GB free]
pvscan -- total: 1 [37.27 GB] / in use: 1 [37.27 GB] / in no VG: 0 [0]

# pvcreate -v /dev/hda2
pvcreate -- locking logical volume manager
pvcreate -- checking physical volume name "/dev/hda2"
pvcreate -- getting physical volume size
pvcreate -- checking partition type
pvcreate -- creating new physical volume
pvcreate -- setting up physical volume for /dev/hda2 with 36676395 sectors
pvcreate -- writing physical volume data to disk "/dev/hda2"
pvcreate -- physical volume "/dev/hda2" successfully created
pvcreate -- unlocking logical volume manager

# pvscan -v
pvscan -- reading all physical volumes (this may take a while...)
pvscan -- walking through all physical volumes found
pvscan -- inactive PV "/dev/hda2" is in no VG  [17.49 GB]
pvscan -- ACTIVE   PV "/dev/hdb"  of VG "tweet" [37.27 GB / 13.27 GB free]
pvscan -- total: 2 [54.76 GB] / in use: 1 [37.27 GB] / in no VG: 1 [17.49 GB]

# vgextend tweet /dev/hda2
vgextend -- INFO: maximum logical volume size is 255.99 Gigabyte
vgextend -- doing automatic backup of volume group "tweet"
vgextend -- volume group "tweet" successfully extended

# vgscan -v
vgscan -- removing "/etc/lvmtab" and "/etc/lvmtab.d"
vgscan -- reading all physical volumes (this may take a while...)
vgscan -- scanning for all active volume group(s) first
vgscan -- found active volume group "tweet"
vgscan -- reading data of volume group "tweet" from physical volume(s)
vgscan -- ERROR "vg_read_with_pv_and_lv(): allocated LE of LV" can't get data of volume group "tweet" from physical volume(s)
vgscan -- ERROR "vg_read_with_pv_and_lv(): allocated LE of LV" creating "/etc/lvmtab" and "/etc/lvmtab.d"

# pvscan -v
pvscan -- reading all physical volumes (this may take a while...)
pvscan -- walking through all physical volumes found
pvscan -- ACTIVE   PV "/dev/hda2"  is associated to an unknown VG (run vgscan)
pvscan -- ACTIVE   PV "/dev/hdb"   is associated to an unknown VG (run vgscan)
pvscan -- total: 2 [54.76 GB] / in use: 2 [54.76 GB] / in no VG: 0 [0]







Note that the system is still useable at this point... the kernel LVM is fine,
but none of the userland tools can find their asses (this includes receiving
periodic lvmsadc crontab mouth-frothings about the kernel and /etc/lvmtab DB
mismatch).  After a reboot, however, vgscan still can't find its ass and
everything fails, taking most of the machine's overall competence with it 
(obvious due to lack of /usr).  After a reboot, a sequence like the following
is necessary to bring it back:

cd /etc/lvmconf
mv tweet.conf.1.old tweet.conf
vgcfgrestore -v -n tweet /dev/hdb
vgscan
/etc/init.d/lvm restart
mount /usr
mount /home
mount /music
*start various services manually, reboot, or switch init runlvls*



I'm running stock linux 2.4.6 LVM built as a module, with the debian sid "lvm10"
package userland utilities (debian package version 0.9-1.2).

hda2 used to be a DOS "extended" partition, containing 3 logical drives.  All 3
of these have been migrated successfully to LV's (the VG using hdb as sole PV).
That leaves me (after a bit of cfdisking) with one free partition taking up 80%
of hda.  I'd love to use this partition as a PV and chuck it into the VG, but
it doesn't seem to work, as I've documented above.

Am I doing something wrong?  How outdated is the LVM code in stock 2.4.6?  If this
isn't my fault, is this likely to be a kernel bug or userland bug?  Would a redo
of the transscript, using -d instead of (or in addition to) -v, be useful?

If there's any more info I can provide, please feel free to ask.

-- 
#!/usr/bin/perl
my($r)=shift; die "Usage: $0 perlregex [file(s)]\n"
if!defined($r);@ARGV="."if(! ARGV);while($_=shift){
@F=`find $_ -type f`;chomp F;for$f(@F){open(I,$f)or
next;while(<I>){print"$f:$.:$_" if/$r/;}close(I);}}


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