On Wed, Sep 30, 2020, 1:00 PM Duncan Townsend wrote: > On Tue, Sep 29, 2020, 10:54 AM Zdenek Kabelac wrote: > >> Dne 29. 09. 20 v 16:33 Duncan Townsend napsal(a): >> > On Sat, Sep 26, 2020, 8:30 AM Duncan Townsend > > > wrote: >> > >> >> > > There were further error messages as further snapshots were >> attempted, >> > > > but I was unable to capture them as my system went down. Upon >> reboot, >> > > > the "transaction_id" message that I referred to in my previous >> message >> > > > was repeated (but with increased transaction IDs). >> > > >> > > For better fix it would need to be better understood what has >> happened >> > > in parallel while 'lvm' inside dmeventd was resizing pool data. >> > >> >> So the lvm2 has been fixed upstream to report more educative messages to >> the user - although it still does require some experience in managing >> thin-pool kernel metadata and lvm2 metadata. >> > > That's good news! However, I believe I lack the requisite experience. Is > there some documentation that I ought to read as a starting point? Or is it > best to just read the source? > > > To the best of my knowledge, no other LVM operations were in flight >> at >> > the time. The script that I use issues LVM commands strictly >> >> In your case - dmeventd did 'unlocked' resize - while other command >> was taking a snapshot - and it happened the sequence with 'snapshot' has >> won - so until the reload of thin-pool - lvm2 has not spotted difference. >> (which is simply a bad race cause due to badly working locking on your >> system) >> > > After reading more about lvm locking, it looks like the original issue > might have been that the locking directory lives on a lv instead of on a > non-lvm-managed block device. (Although, the locking directory is on a > different vg on a different pv from the one that had the error.) > > Is there a way to make dmeventd (or any other lvm program) abort if this > locking fails? Should I switch to using a clustered locking daemon (even > though I have only the single, non-virtualized host)? > > > Would it be reasonable to use vgcfgrestore again on the >> > manually-repaired metadata I used before? I'm not entirely sure what >> >> You will need to vgcfgrestore - but I think you've misused my passed >> recoverd >> piece, where I've specifically asked to only replace specific segments of >> resized thin-pool within your latest VG metadata - since those likely have >> all the proper mappings to thin LVs. >> > > All I did was use vgcfgrestore to apply the metadata file attached to your > previous private email. I had to edit the transaction number, as I noted > previously. That was a single line change. Was that the wrong thing to do? > I lack the experience with lvm/thin metadata, so I am flying a bit blind > here. I apologize if I've made things worse. > > While you have taken the metadata from 'resize' moment - you've lost all >> the thinLV lvm2 metadata for later created one. >> >> I'll try to make one for you. >> > > Thank you very much. I am extremely grateful that you've helped me so much > in repairing my system. > > > to look for while editing the XML from thin_dump, and I would very >> > much like to avoid causing further damage to my system. (Also, FWIW, >> > thin_dump appears to segfault when run with musl-libc instead of >> >> Well - lvm2 is glibc oriented project - so users of those 'esoteric' >> distribution need to be expert on its own. >> >> If you can provide coredump or even better patch for crash - we might >> replace the code with something better usable - but there is zero testing >> with anything else then glibc... >> > > Noted. I believe I'll be switching to glibc because there are a number of > other packages that are broken for this distro. > > If you have an interest, this is the issue I've opened with my distro > about the crash: https://github.com/void-linux/void-packages/issues/25125 > . I despair that this will receive much attention, given that not even gdb > works properly. > Hello! Could somebody advise whether restoring the VG metadata is likely to cause this system's condition to worsen? At this point, all I want is to do is get the data off this drive and then start over with something more stable. Thanks for the help! --Duncan Townsend P.S. This was written on mobile. Please forgive my typos. >