Re: btrfs ENOSPC "not the usual problem"

[Liu Bo <bo.li.liu@oracle.com>]

On Thu, Jun 02, 2016 at 07:45:49PM +0000, Omari Stephens wrote:
> [Note: not on list; please reply-all]
> 
> I've read everything I can find about running out of space on btrfs, and it
> hasn't helped.  I'm currently dead in the water.
> 
> Everything I do seems to make the problem monotonically worse — I tried
> adding a loopback device to the fs, and now I can't remove it.  Then I tried
> adding a real device (mSATA) to the fs and now I still can't remove the
> loopback device (which is making everything super slow), and I also can't
> remove the mSATA.  I've removed about 100GB from the filesystem and that
> hasn't done anything either.
> 
> Is there anything I can to do even figure out how bad things are, what I
> need to do to make any kind of forward progress?  This is a laptop, so I
> don't want to add an external drive only to find out that I can't remove it
> without corrupting my filesystem.
> 
> ### FILESYSTEM STATE
> 19:23:14> [root{slobol}@/home/xsdg]
> #btrfs fi show /home
> Label: none  uuid: 4776be5b-5058-4248-a1b7-7c213757dfbd
>     Total devices 3 FS bytes used 221.02GiB
>     devid    1 size 418.72GiB used 413.72GiB path /dev/sda3
>     devid    2 size 10.00GiB used 5.00GiB path /dev/loop0
>     devid    3 size 14.91GiB used 3.00GiB path /dev/sdb1
> 
> 
> 19:23:33> [root{slobol}@/home/xsdg]
> #btrfs fi usage /home
> Overall:
>     Device size:         443.63GiB
>     Device allocated:         421.72GiB
>     Device unallocated:          21.91GiB
>     Device missing:             0.00B
>     Used:             221.68GiB
>     Free (estimated):         219.24GiB    (min: 208.29GiB)
>     Data ratio:                  1.00
>     Metadata ratio:              2.00
>     Global reserve:         228.00MiB    (used: 36.00KiB)
> 
> Data,single: Size:417.69GiB, Used:220.36GiB
>    /dev/loop0       5.00GiB
>    /dev/sda3     409.69GiB
>    /dev/sdb1       3.00GiB
> 
> Metadata,single: Size:8.00MiB, Used:0.00B
>    /dev/sda3       8.00MiB
> 
> Metadata,DUP: Size:2.00GiB, Used:674.45MiB
>    /dev/sda3       4.00GiB
> 
> System,single: Size:4.00MiB, Used:0.00B
>    /dev/sda3       4.00MiB
> 
> System,DUP: Size:8.00MiB, Used:56.00KiB
>    /dev/sda3      16.00MiB
> 
> Unallocated:
>    /dev/loop0       5.00GiB
>    /dev/sda3       5.00GiB
>    /dev/sdb1      11.91GiB
> 
> 
> ### BALANCE FAILS, EVEN WITH -dusage=0
> 19:23:02> [root{slobol}@/home/xsdg]
> #btrfs balance start -v -dusage=0 .
> Dumping filters: flags 0x1, state 0x0, force is off
>   DATA (flags 0x2): balancing, usage=0
> ERROR: error during balancing '.': No space left on device
> There may be more info in syslog - try dmesg | tail

1. Could you please show us your `uname -r`?

2. http://git.kernel.org/cgit/linux/kernel/git/kdave/btrfs-progs.git/tree/btrfs-debugfs
We need to know more information about block group in order to take more
fine-grained balance, so there is a tool for developer called
'btrfs-debugfs', you may download it from the above link, it's a python
script, as long as you're able to run it, try btrfs-debugfs -b
/your_partition.

Thanks,

-liubo

> 
> 
> ### CAN'T REMOVE DEVICES -> ENOSPC
> #btrfs device remove /dev/loop0 /home
> ERROR: error removing device '/dev/loop0': No space left on device
> 
> --xsdg
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