Re: ENOSPC at 94% full -- and causing BUGs elsewhere?

[Chris Mason <chris.mason@oracle.com>]

On Mon, Oct 12, 2009 at 03:09:35PM +0100, Hugo Mills wrote:
> On Sun, Oct 04, 2009 at 08:06:30AM -0400, Chris Mason wrote:
> > On Sat, Oct 03, 2009 at 05:55:32PM -0400, Josef Bacik wrote:
> > > On Sat, Oct 03, 2009 at 01:21:09PM +0100, Hugo Mills wrote:
> > > >    I've just had the following on my home server. I believe that it's
> > > > btrfs that's responsible, as the machine wasn't doing much other than
> > > > reading/writing on a btrfs filesystem. The process that was doing so
> > > > is now stuck in D+ state, and can't be killed. The timing of the oops
> > > > at the end is also suggestive of being involved in the same incident.
> > > > This is the only btrfs filesystem on the machine.
> > > 
> > > Patches have gone to Linus to fix the enospc problems.  You can try running the
> > > enospc branch of Chris's git tree and it should behave better for you.  Thanks,
> > 
> > The right tree for this is the master branch of btrfs-unstable for
> > 2.6.31.
> 
>    Thanks, Josef and Chris. I've now found the time to check out and
> build the btrfs-unstable tree, and it is indeed handling the ENOSPC
> condition much more cleanly.
> 
>    However, it seems to have got into a position where I have lots of
> free space reported by df (over 10% of the size of the volume -- 185
> GiB free of 1474 GiB total), but still refuses to write anything to
> the filesystem. Do you have any suggestions for what I could try?

You've probably got most of that 10GB free allocated as metadata.  You
could try btrfs-vol -b.

-chris