[lxc-devel] Change rootfs pinning mechnism

[Rob Landley]

On 09/13/2013 10:28:25 AM, Serge Hallyn wrote:
> Quoting Michael H. Warfield (mhw at WittsEnd.com):
> > On Fri, 2013-09-13 at 07:56 -0500, Serge Hallyn wrote:
> > > Quoting Jäkel, Guido (G.Jaekel at dnb.de):
> > > > Hello,
> > > >
> > > > I'm late but I just want to mention that I expect that all this  
> kind
> > > of "unlinking" on a NFS will show up as a stale NFS handle, i.e. a
> > > still visible hidden directory entry  
> (.nfs00??????????????????????).
> > > Therefore, one have to take care of this (i.e. exclude) if he  
> make a
> > > copy of such (for the purpose of cloning or even for backups).  
> This
> > > isn't a LXC-, but a NFS-caveat. An NFS-aware will (should) know  
> about
> > > to deal with this but there he should have to know (by the
> > > documentation) that LXC will use this unlinking mechanism to  
> correlate
> > > this stale handle.
> >
> > > Will it use the same name every time?  Will it eventually go away?
> >
> > > I really don't want a new switch for this.  If we have to do  
> something
> > > I'd rather detect nfs and do something different.
> >
> > Jäkel beat me to the punch on that one but he's absolutely right.   
> The
> > whole delete a file with the file handle still open is known to NOT  
> work
> > properly over NFS.
> 
> So are a lot of other things :)
> 
> > In the back of my mind, I seem to recall some
> > discussion over whether NFS v3 would handle that case properly or  
> not.
> > I could be wrong there but earlier versions would definitely NOT  
> behave
> > as intended.  I have no clue if it works over AFS or SMB but I
> > definitely would not trust it over any network file system.  The  
> results
> > could be unpredictable.
> 
> I don't mind reverting that patch, but we're not putting in a config
> switch for it.  My preference is for lxc to detect a netfs and behave
> differently there.

I note that if the netfs is 9p/v9fs, it _should_ work. (And if it  
doesn't, ping me and I'll try to fix it. I containerized that in the  
first place.)

Unlike nfs and samba, 9p is _not_crazy_.

Rob