Errors during defragmentation

Errors during defragmentation

[Andrej Podzimek]

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Hello,

I decided to test the 'defragment' feature on my system (after a huge number of system updates and prelinking):

	find /bin /sbin /lib /usr/lib /usr/bin /usr/sbin -type d -exec btrfs filesystem defragment '{}' '+'

I have already defragmented a couple of (very large) directories with no errors at all, so this was expected to work somehow. Surprisingly, this time there were thousands of messages like this:

	ioctl failed on <directory name> ret -1 errno 28

Most of the reported directories had zero files/subdirectories. However, *most* of them were *not* empty...

What does this error message mean? Could someone shed more light on this, please? Should I get ready for a bad crash? ;-) (There seems to be no data loss so far. No new messages in dmesg, no unexpected system behavior.)

Andrej



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Re: Errors during defragmentation

[Hugo Mills]

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On Mon, Nov 29, 2010 at 10:02:56PM +0100, Andrej Podzimek wrote:
> Hello,
> 
> I decided to test the 'defragment' feature on my system (after a huge number of system updates and prelinking):
> 
> 	find /bin /sbin /lib /usr/lib /usr/bin /usr/sbin -type d -exec btrfs filesystem defragment '{}' '+'
> 
> I have already defragmented a couple of (very large) directories with no errors at all, so this was expected to work somehow. Surprisingly, this time there were thousands of messages like this:
> 
> 	ioctl failed on <directory name> ret -1 errno 28

   errno 28 is ENOSPC

   You've run out of disk space. (Or at least, btrfs thinks so).

> Most of the reported directories had zero files/subdirectories. However, *most* of them were *not* empty...

> What does this error message mean? Could someone shed more light on
> this, please? Should I get ready for a bad crash? ;-) (There seems
> to be no data loss so far. No new messages in dmesg, no unexpected
> system behavior.)

   Hugo.

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Re: Errors during defragmentation

[Andrej Podzimek]

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>> Hello,
>>
>> I decided to test the 'defragment' feature on my system (after a huge number of system updates and prelinking):
>>
>> 	find /bin /sbin /lib /usr/lib /usr/bin /usr/sbin -type d -exec btrfs filesystem defragment '{}' '+'
>>
>> I have already defragmented a couple of (very large) directories with no errors at all, so this was expected to work somehow. Surprisingly, this time there were thousands of messages like this:
>>
>> 	ioctl failed on<directory name>  ret -1 errno 28
>
>     errno 28 is ENOSPC
>
>     You've run out of disk space. (Or at least, btrfs thinks so).

Pleased to hear that this is not a fatal error. :-)

The filesystem still has quite a lot of free space. New files can be created. I have just tried to add about 10 GB of data, which worked fine. The output from 'df' indicates that only 71% of the partition (177 GB out of 250 GB) is used.

The "built-in" df shows similar numbers -- if I understand it well, there is plenty of free space left.

	# btrfs filesystem df /
	Data: total=175.01GB, used=169.57GB
	Metadata: total=6.51GB, used=3.64GB
	System: total=12.00MB, used=32.00KB

	# btrfs filesystem show octopus
	failed to read /dev/sdb
	failed to read /dev/sr0
	Label: 'octopus'  uuid: 8576b57b-b934-424e-9a8a-04abc780c963
	        Total devices 1 FS bytes used 173.21GB
	        devid    1 size 249.50GB used 188.04GB path /dev/dm-2

	Btrfs Btrfs v0.19

Does defragmentation have any unexpected (and not yet documented) free space requirements? (Most of the files I was attempting to defragment were smaller than 10 MB, as the directory names suggest.)

Is there a workaround for this issue? Or should I just leave the defragmentation feature alone for the time being?

Andrej


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