>> Hello,
quoted text
>>
>> 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