Re: Which xfsprogs version to which kernel version

Dave Chinner
2015-12-01T20:27:24Z

On Tue, Dec 01, 2015 at 09:30:00AM +0100, Martin Steigerwald wrote:
> Am Dienstag, 1. Dezember 2015, 08:41:04 CET schrieb Dave Chinner:
> > On Thu, Nov 26, 2015 at 11:21:45AM +0100, aluno3@poczta.onet.pl wrote:
> > > Hello,
> > >
> > > I am using kernel 3.10 and would like to update xfsprogs (currently I
> > > have 3.1.5).
> > >
> > > When I tried to use the newest version of xfsprogs 4.3.0 I get the call
> > > trace about detected version 5 of superblock when mounting volume which
> > > was formatted using mkfs.xfs from 4.3.0.
> >
> > More recent xfsprogs versions enable features that are only
> > supported by recent kernels. We tend to wait at least a year before
> > enabling new features by default in xfsprogs so that kernel support
> > is usually picke dup by distros before they update xfsprogs....
> >
> > If you have an old kernel, then you need to turn off the newer
> > features that your kernel does not support. This has always been the
> > case - if you update the xfsprogs yourself, then you need to use the
> > correct options for your kernel. In general, this:
> >
> > # mkfs.xfs -f -m crc=0 -n ftype=0 <dev>
> >
> > will make a filesystem that can be mounted on old kernels. If
> > distros are shipping old kernels with new xfsprogs and are not
> > changing the default behaviour to suit their kernel, then that is a
> > distro problem.
>
> How about just checking running kernel version before enabling this by
> default?

The btrfs solution? No thanks.

Apart from the fact I make filesystems that the kernel does not
support all the time, xfstests does the same thing so that we can
test that the kernel correctly rejects mounts of filesystems with
features it doesn't support. And this fails when a distro installer
or rescue distro has a different kernel to the one the distro
actually uses, too...

And, really, where does this slipperly slope end? Suddenly we have
to maintain a map of every feature in every mainline kernel, then
every distro kernel that does backports (e.g. sles, rhel, etc) and
we end up with something nobody can maintain or test.

> While this is some implementation effort, it may help to reduce questions on
> this mailing list. And as you see distro problem or not: People still ask
> here. :)

The majority of distro's get it right the majority of the time -
there's no point in turning everything upside down just to silence a
very small vocal minority. i.e. It's only when users do their own
package upgrades, or a distro screws up (like gentoo with shipping
3.2.4 on an old kernel) that users end up with a problem.

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com