On 2018/8/12 上午8:30, Qu Wenruo wrote:
> On 2018/8/12 上午5:10, Dan Merillat wrote:
>> 19 hours later, still going extremely slowly and taking longer and
>> longer for progress made.  Main symptom is the mount process is
>> spinning at 100% CPU, interspersed with btrfs-transaction spinning at
>> 100% CPU.
>> So far it's racked up 14h45m of CPU time on mount and an additional
>> 3h40m on btrfs-transaction.
>> The current drop key changes every 10-15 minutes when I check it via
>> inspect-internal, so some progress is slowly being made.
>> I built the kernel with ftrace to see what's going on internally, this
>> is the pattern I'm seeing:
> [snip]
> It looks pretty like qgroup, but too many noise.
> The pin point trace event would btrfs_find_all_roots().
>> Repeats indefinitely.  btrace shows basically zero activity on the
>> array while it spins, with the occasional burst when mount &
>> btrfs-transaction swap off.
>> To recap the chain of events leading up to this:
>> 11TB Array got completely full and started fragmenting badly.
>> Ran bedup and it found 600gb of duplicate files that it offline-shared.
>> Reboot for unrelated reasons
> 11T, with highly deduped usage is really the worst scenario case for qgroup.
> Qgroup is not really good at handle hight reflinked files, nor balance.
> When they combines, it goes worse.
>> Enabled quota on all subvolumes to try to track where the new data is
>> coming from
>> Tried to balance metadata due to transaction CPU spikes
>> Force-rebooted after the array was completely lagged out.
>> Now attempting to mount it RW.  Readonly works, but RW has taken well
>> over 24 hours at this point.
> I'll add a new rescue subcommand, 'btrfs rescue disable-quota' for you
> to disable quota offline.

Patch set (from my work mailbox), titled "[PATCH] btrfs-progs: rescue:
Add ability to disable quota offline".
Can also be fetched from github:

Usage is:
# btrfs rescue disable-quota <device>

Tested locally, it would just toggle the ON/OFF flag for quota, so the
modification should be minimal.


> Thanks,
> Qu

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