Re: With Linux 5.5: Filesystem full while still 90 GiB free

[Martin Steigerwald <martin@lichtvoll.de>]

Chris Murphy - 29.01.20, 23:55:06 CET:
> On Wed, Jan 29, 2020 at 2:20 PM Martin Steigerwald 
<martin@lichtvoll.de> wrote:
> > So if its just a cosmetic issue then I can wait for the patch to
> > land in linux-stable. Or does it still need testing?
> 
> I'm not seeing it in linux-next. A reasonable short term work around
> is mount option 'metadata_ratio=1' and that's what needs more testing,
> because it seems decently likely mortal users will need an easy work
> around until a fix gets backported to stable. And that's gonna be a
> while, me thinks.
>
> Is that mount option sufficient? Or does it take a filtered balance?
> What's the most minimal balance needed? I'm hoping -dlimit=1

Does not make a difference. I did:

- mount -o remount,metadata_ratio=1 /daten
- touch /daten/somefile
- dd if=/dev/zero of=/daten/someotherfile bs=1M count=500
- sync
- df still reporting zero space free
 
> I can't figure out a way to trigger this though, otherwise I'd be
> doing more testing.

Sure.

I am doing the balance -dlimit=1 thing next. With metadata_ratio=0 
again.

% btrfs balance start -dlimit=1 /daten
Done, had to relocate 1 out of 312 chunks

% LANG=en df -hT /daten                   
Filesystem             Type   Size  Used Avail Use% Mounted on
/dev/mapper/sata-daten btrfs  400G  311G     0 100% /daten

Okay, doing with metadata_ratio=1:

% mount -o remount,metadata_ratio=1 /daten

% btrfs balance start -dlimit=1 /daten    
Done, had to relocate 1 out of 312 chunks

% LANG=en df -hT /daten                   
Filesystem             Type   Size  Used Avail Use% Mounted on
/dev/mapper/sata-daten btrfs  400G  311G     0 100% /daten


Okay, other suggestions? I'd like to avoid shuffling 311 GiB data around 
using a full balance.

Thanks,
-- 
Martin