Re: write barrier over device mapper supported or not?

[Martin Steigerwald <Martin@lichtvoll.de>]

Am Mittwoch 12 Dezember 2007 schrieb Eric Sandeen:
> Martin Steigerwald wrote:
> > Hello!
> >
> > Are write barriers over device mapper supported or not?
>
> Nope.

[...]

> > But back then I also looked at the ext3 / jbd sources and found that
> > jbd issues a warning when barrier support is not available. However I
> > do not find that one either.
>
> in journal_write_commit_record() there is such a warning, but not in
> the mount path:
>
>                 printk(KERN_WARNING
>                         "JBD: barrier-based sync failed on %s - "
>                         "disabling barriers\n",
>                         bdevname(journal->j_dev, b));
>
> and if I set barrier=1 on an lvm-root test box, I do get:
>
> JBD: barrier-based sync failed on dm-0 - disabling barriers

Yes, I get it after actually touching a file and waiting for the kjournald 
commit interval of 5 seconds to occur.

Well I reported a bug about it, lets see what happens:

http://bugzilla.kernel.org/show_bug.cgi?id=9554

One might consider it being a feature wish of course.

-- 
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA  B82F 991B EAAC A599 84C7