Re: blkback name greater than 16 characters issue

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Mon, Jan 04, 2016 at 04:13:57PM +0000, Ian Jackson wrote:
> Konrad Rzeszutek Wilk writes ("blkback name greater than 16 characters issue"):
> > Way back in the past Jan pointed out this issue
> > http://lists.xenproject.org/archives/html/xen-devel/2015-05/msg03505.html
> > 
> > which is that the device name is "blkback.<domid>.<name>"
> > for exmaple: blkback.8.xvda, blkback.11.hda
> 
> I don't understand in what sense this is the `device name'.
> 
> AFAICT from your references we are talking about what appears in `ps'
> on BSD.  Is that right ?  The lack of uniqueness is a problem for
> admins and for debugging but not for functionality ?

Correct. Just for troubleshooting or such. You can look at 'top'
or 'ps' and see which of the blkback threads is eating CPU cycles or such.

> 
> > My desire is to easily correlate the name of the thread with the
> > guest config. And that means preserving the 'xvda' or 'hda' or whatever
> > the user had in mind.
> > 
> > I believe the domain id is important as well - so we need that.
> > 
> > Which means we are left with the prefix. Should it be 'blkbk' or
> > should it be completely eliminated? Meaning we have:
> 
> Surely this string should have something in it which makes it clear
> that it's a Xen vbd backend.
> 
> I suggest for xvds
> 
>   1234567890123456
>   DOMID.xvdXYNN
> 
> and for the others
> 
>   1234567890123456
>   DOMID.xvd-hdXYNN
> 
> It's a shame that DOMID comes first but I can't think of a sane syntax
> that puts `x', DOMID, type, and XYNN in that order.

OK, let me prep a patch for this shortly.

Thank you!
> 
> Ian.