Re: [dm-devel] [PATCH] block: silently error unsupported empty barriers too

[Mikulas Patocka <mpatocka redhat com>]

On Thu, 6 Aug 2009, Alasdair G Kergon wrote:

> On Thu, Aug 06, 2009 at 12:14:17PM +0100, Mark McLoughlin wrote:
> > We should error all barriers, even empty barriers, on devices like
> > virtio_blk which don't support them.
>  
> Have you considered whether or not virtio_blk actually needs to
> support empty barriers?
> 
> Alasdair

This is only for request-based drivers, where it is the responsibility of 
blk-core to translate barriers. I think the empty barrier request anyway 
in blk_do_ordered, but with an error message. So the patch changes it to 
discard it early and queitly. It seems ok.

Mikulas