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. Thanks again! --Duncan Townsend P.S. This was written on mobile. Please forgive my typos.