Re: btrfs goes readonly + No space left on 4.3

On Tue, May 03, 2016 at 04:06:05AM +0000, Paul Jones wrote:

quoted

-----Original Message-----
From: linux-btrfs-owner@vger.kernel.org [mailto:linux-btrfs-
owner@vger.kernel.org] On Behalf Of Omar Sandoval
Sent: Tuesday, 3 May 2016 8:06 AM
To: Stefan Priebe <redacted>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: btrfs goes readonly + No space left on 4.3

On Fri, Apr 29, 2016 at 10:48:15PM +0200, Stefan Priebe wrote:

quoted

just want to drop a note that all those ENOSPC msg are gone with v4.5
and space_cache=v2. Any plans to make space_cache=v2 default?

Greets,
Stefan

Yup, we want to make space_cache=v2 the default at some point. I'm
running it on my own machines and testing it here at Facebook and haven't
run into any issues yet. Besides stability, I also want to make sure there
aren't any performance regressions versus the old free space cache that we
haven't thought about yet.

Thanks for trying it out :)

I have also been testing it and have had no problems.

One question I have about it: I use Grub2 to boot my systems directly from a BTRFS root partition (i.e. no separate /boot), I assume Grub shouldn't need to care about free space tree/cache as it's only reading data? I don't know enough about either to know if it's an issue or not.

Thanks,
Paul.

Yeah, the free space tree doesn't make a difference when the filesystem
is used read-only. In fact, you can mount a filesystem with
space_cache=v2 enabled read-only on older kernel versions.

-- 
Omar