Btrfs devel - Mar 2013 - "No space left on device" although df reports only 55% in use

Hi,

I am using a btrfs loopback mounted file with lzo-compression on
Linux-3.7.9, and I ran into "No space left on device" messages,
although df reports only 55% of space is used:

# touch testfile
touch: cannot touch `testfile'': No space left on device

# df
Filesystem     1K-blocks      Used Available Use% Mounted on
/dev/loop0      32768000  17383924  14649172  55% /home/ce/anditest

# btrfs filesystem df .
Data: total=28.22GB, used=14.25GB
System, DUP: total=8.00MB, used=12.00KB
System: total=4.00MB, used=0.00
Metadata, DUP: total=1.50GB, used=1.16GB
Metadata: total=8.00MB, used=0.00

Any ideas what is going wrong here?

Thank you in advance, Clemens
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Hi again,

I wonder if this is the intended behaviour or some known issue?
Otherwise I could provide a tool written by a friend of mine which can
trigger this issue within a few minutes on a a fresh btrfs partition.
Its basically a file-system aging tester, which replays some
real-world logs taken from NFS file servers.

Regards, Clemens
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On Wed, Mar 27, 2013 at 12:28:23AM +0100, Clemens Eisserer
wrote:
> I am using a btrfs loopback mounted file with lzo-compression on
> Linux-3.7.9, and I ran into "No space left on device" messages,
> although df reports only 55% of space is used:
> 
> # touch testfile
> touch: cannot touch `testfile'': No space left on device
> 
> # df
> Filesystem     1K-blocks      Used Available Use% Mounted on
> /dev/loop0      32768000  17383924  14649172  55% /home/ce/anditest
> 
> # btrfs filesystem df .
> Data: total=28.22GB, used=14.25GB
> System, DUP: total=8.00MB, used=12.00KB
> System: total=4.00MB, used=0.00
> Metadata, DUP: total=1.50GB, used=1.16GB
   Your metadata is close to full -- we need quite a lot of working
space to CoW into. You (probably) have the full disk allocated to
chunks, and too much is allocated to data; not enough to metadata. You
need o balance, with a filter for the unused data chunks. See the
section in the FAQ on the wiki about full filesystems. (Sorry for not
finding the link, I''m on a restricted connection right now)

   Hugo.
> Metadata: total=8.00MB, used=0.00
> 
> Any ideas what is going wrong here?
> 
> Thank you in advance, Clemens
-- 
=== Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk ==  PGP
key: 65E74AC0 from wwwkeys.eu.pgp.net or http://www.carfax.org.uk
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On 03/27/2013 10:18 AM, Hugo Mills wrote:
> On Wed, Mar 27, 2013 at 12:28:23AM +0100, Clemens Eisserer wrote:
>> I am using a btrfs loopback mounted file with lzo-compression on
>> Linux-3.7.9, and I ran into "No space left on device"
messages,
>> although df reports only 55% of space is used:
>>
>> # touch testfile
>> touch: cannot touch `testfile'': No space left on device
>>
>> # df
>> Filesystem     1K-blocks      Used Available Use% Mounted on
>> /dev/loop0      32768000  17383924  14649172  55% /home/ce/anditest
>>
>> # btrfs filesystem df .
>> Data: total=28.22GB, used=14.25GB
>> System, DUP: total=8.00MB, used=12.00KB
>> System: total=4.00MB, used=0.00
>> Metadata, DUP: total=1.50GB, used=1.16GB
>
>     Your metadata is close to full -- we need quite a lot of working
Almost 400MB are not sufficient to do simple touch? What is it doing?


Cheers,
Bernd


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Hi Hugo,
>> # btrfs filesystem df .
>> Data: total=28.22GB, used=14.25GB
>> System, DUP: total=8.00MB, used=12.00KB
>> System: total=4.00MB, used=0.00
>> Metadata, DUP: total=1.50GB, used=1.16GB
>
>    Your metadata is close to full -- we need quite a lot of working
> space to CoW into. You (probably) have the full disk allocated to
> chunks, and too much is allocated to data; not enough to metadata. You
> need o balance, with a filter for the unused data chunks. See the
> section in the FAQ on the wiki about full filesystems. (Sorry for not
> finding the link, I''m on a restricted connection right now)
I''ll re-run the test on a filesystem created with -M (metadata and
normal data combined).
As far as I understand it shouldn''t run in the same problem.
> Almost 400MB are not sufficient to do simple touch? What is it doing?
I have to admit that thought occurred to me too ;)

Regards, Clemens
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On Tue, Mar 26, 2013 at 05:28:23PM -0600, Clemens Eisserer
wrote:
> Hi,
> 
> I am using a btrfs loopback mounted file with lzo-compression on
> Linux-3.7.9, and I ran into "No space left on device" messages,
> although df reports only 55% of space is used:
> 
> # touch testfile
> touch: cannot touch `testfile'': No space left on device
> 
> # df
> Filesystem     1K-blocks      Used Available Use% Mounted on
> /dev/loop0      32768000  17383924  14649172  55% /home/ce/anditest
> 
> # btrfs filesystem df .
> Data: total=28.22GB, used=14.25GB
> System, DUP: total=8.00MB, used=12.00KB
> System: total=4.00MB, used=0.00
> Metadata, DUP: total=1.50GB, used=1.16GB
> Metadata: total=8.00MB, used=0.00
> 
> Any ideas what is going wrong here?
> 
Can I see btrfs fi show and try using btrfs-next and see if the problem is
already fixed.  Thanks,

Josef
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