On Sat, Feb 18 2012 at 9:27pm -0500, Spelic <spelic@xxxxxxxxxxxxx> wrote: > Hello lists, > > Do you have any information about a bug in linux v3.0.3, of LVM > snapshot making a mess at (clean!) reboot? > > Symptoms are: message at boot: > [ 15.668799] device-mapper: table: 252:3: snapshot: Snapshot > cow pairing for exception table handover failed > [ 15.668934] device-mapper: ioctl: error adding target to table > [ 19.388627] device-mapper: table: 252:3: snapshot: Snapshot > cow pairing for exception table handover failed > [ 19.388786] device-mapper: ioctl: error adding target to table > > > and then the volume origin and snapshot come out inactive > lvVM_TP1_d1 vgVM owc-i- 500.00g > ... > tp1d1-snap1 vgVM swi-i- 600.00g lvVM_TP1_d1 100.00 (*) > (other volumes not having snapshot are active and working) > > (*) please note the size occupied in the snapshot is WRONG, it > should be 4.56% and not 100%. > > At this point I did: > > # lvchange --refresh vgVM/tp1d1-snap1 > Couldn't find snapshot origin uuid LVM-WUPTe8bqp25OSeRsFcLpC228A6U0r84T22tfFj4EkWbuB6pP5UDTA7nVRfGSCZW7-real. > # lvs > ... *everything hangs* ..!! > > It hangs in DM code (too bad I lost the stack trace, sorry) > I think the ssh session hanged at uninterruptible sleep, there was > no kernel panic, I could indeed login again, however the DM devices > were hanged bad so AFAIR I had to force a reboot without syncing or > it would not complete the shutdown process. > > > At reboot the situation at lvs is unchanged, with the two LVM > devices (origin and snapshot) still inactive. > > This time I try refresh on the *origin*: > > # lvchange --refresh vgVM/lvVM_TP1_d1 > (no output) > # > > and magically everything starts working! > I can do lvs, dmsetup table is all filled, etc. > Size occupied in snapshot shown in lvs is back to correct value 4.56% > > Then I reboot (clean!) again so to check that problems are solved now... > Surprise!! The problems are back. The two devices, origin and > snapshot, are again inactive. > > This time I think I learned the lesson and I refresh again *the origin* > (I am SURE I used the origin, I triple checked that, I gave > *exactly* the same command of the previous time) > > # lvchange --refresh vgVM/lvVM_TP1_d1 > > Surprise!! everything hangs!! > > Like before, no kernel panic, however ssh session hangs and DM is > unresponsive so I had to force a reboot without sync or it would not > complete. > > > At reboot again devices are inactive. > > At this point I am really fed up of LVM snapshots and I fear for our > data, so I remove the snapshot with lvremove (I don't remember if I > had to do lvchange --refresh on the origin before lvremove or not) > > As soon as I removed the snapshot everything started working flawlessly. > > > I am very worried about this bug... > We would need snapshot at work for performing live backups, but with > this situation I don't know if I am risking more with snapshots or > by not performing backups. > Do you have any information on this bug, e.g. has this been fixed > since 3.0.3? I've never seen this. Which distro are you using? The "Snapshot cow pairing for exception table handover failed" is the error path most commonly associated with the snapshot-merge feature. Are you using snapshot-merge for the root LV (e.g. lvconvert --merge ...)? Mike -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
