On 09/09/2016 01:51 PM, Chris Murphy wrote: > On Fri, Sep 9, 2016 at 10:12 AM, moparisthebest > <ad...@moparisthebest.com> wrote: >> Hi, >> >> I'm hoping to get some help with mounting my btrfs array which quit >> working yesterday. My array was in the middle of a balance, about 50% >> remaining, when it hit an error and remounted itself read-only [1]. >> btrfs fi show output [2], btrfs df output [3]. >> >> I unmounted the array, and when I tried to mount it again, it locked up >> the whole system so even alt+sysrq would not work. I rebooted, tried to >> mount again, same lockup. This was all kernel 4.5.7. >> >> I rebooted to kernel 4.4.0, tried to mount, crashed again, this time a >> message appeared on the screen and I took a picture [4]. >> >> I rebooted into an arch live system with kernel 4.7.2, tried to mount >> again, got some dmesg output before it crashed [5] and took a picture >> when it crashed [6], says in part 'BUG: unable to handle kernel NULL >> pointer dereference at 00000000000001f0'. >> >> Is there anything I can do to get this in a working state again or >> perhaps even recover some data? >> >> Thanks much for any help >> >> [1]: https://www.moparisthebest.com/btrfs/initial_crash.txt >> [2]: https://www.moparisthebest.com/btrfs/btrfsfishow.txt >> [3]: https://www.moparisthebest.com/btrfs/btrfsdf.txt >> [4]: https://www.moparisthebest.com/btrfsoops.jpg >> [5]: https://www.moparisthebest.com/btrfs/dmsgprecrash.txt >> [6]: https://www.moparisthebest.com/btrfsnulldereference.jpg > > Good report. Try on the 4.7.2 kernel system, two consoles, have one > ready with 'echo w > /proc/sysrq-trigger' as root (sudo doesn't work) > but don't issue it, mount in the other console and then switch back > and issue the sysrq. It'll take a while, minutes maybe even to switch > consoles, and then also for the command itself to issue, and then > minutes before the result actually gets committed to systemd journal > or var/log/messages. If it's a systemd system, and if you have to > force reboot to regain control, you can get the sysrq with 'journalctl > -b-1 -k > outputfile.txt' > > Also btrfs check output is useful to include also (without --repair > for starters). > > The thing that concerns me is this occasional problem that comes up > sometimes with lzo compressed volumes. Duncan knows more about that > one so he may chime in. I would definitely only do default mounts for > the above, don't include the compression option. You could also try -o > ro,recovery and see where that gets you. > >
This is indeed an lzo compressed system, it's always been mounted with that option anyhow. btrfs check has been running for ~6 hours so far, I'll follow up with output on that when it finishes. Hmm, the problem with the 4.7.2/systemd system is it's a live usb system so the log/journal wouldn't be saved anywhere except tmpfs, I'll see what I can rig up unless someone has any amazing ideas? I'm still brand new to systemd... Thanks! -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
