Re: BTRFS constantly reports "No space left on device" even with a huge unallocated space

[Jeff Mahoney <jeffm@suse.com>]

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On 8/31/16 6:58 PM, Chris Murphy wrote:
> On Wed, Aug 31, 2016 at 4:47 PM, Jeff Mahoney <jeffm@suse.com> wrote:
>> On 8/31/16 5:48 PM, Chris Murphy wrote:
>>> OK it looks like with -w flag I can get a reliable indication of
>>> whether quota is enabled or not:
>>>
>>> [root@f24s ~]# btrfs quota enable /mnt/0
>>> [root@f24s ~]# btrfs quota rescan -w /mnt/0
>>> quota rescan started
>>> [root@f24s ~]# btrfs quota disable /mnt/0
>>> [root@f24s ~]# btrfs quota rescan -w /mnt/0
>>> ERROR: quota rescan failed: Invalid argument
>>>
>>>
>>> So if you did not enable quota support, and aren't sure if it's
>>> enabled you can try 'btrfs quota rescan -w <mp>' but this might
>>> actually be a bad idea, a rescan could take a while if you're actually
>>> using quotas, I have no idea because I don't use them.
>>
>> It can take a while, but the code is smart enough not to get too much in
>> the way of other activity.  It maintains a progress marker and only does
>> live accounting on extents that have already been scanned.
>>
>>> Perhaps someone can point out an easier way to determine whether
>>> quotas are enabled?
>>
>> btrfs qgroup show <path>
> 
> Wow, thanks but that's not obvious at all. man btrfs quota is
> described as "btrfs-quota - control the global quota status of a btrfs
> filesystem" so it stands to reason the state command for whether it's
> enabled or disabled would be in that subcommand not in some other
> subcommand.

Agreed.  The tools interface has some warts.

> But this is sidetracking. Does Ronan's call trace showing
> /fs/btrfs/qgroup.c:2667
>> btrfs_qgroup_free_meta implicate qgroups as a possible source of his problem? That trace would only happen if quotas were enabled, right?
> 

Yeah.  That warning doesn't get checked unless they're enabled.

-Jeff

-- 
Jeff Mahoney
SUSE Labs


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