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Subject: Re: VFS + path walktrough
From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: viro@ZenIV.linux.org.uk, weigelt@metux.de, linux-kernel@vger.kernel.org
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Date: Mon, 05 May 2008 16:16:39 -0400
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On Mon, 2008-05-05 at 20:31 +0200, Miklos Szeredi wrote:
> > > > >  Take a look at 9P walk - it does *not* give
> > > > > you anything resembling stat, you just get qids of intermediates.
> > > > 
> > > > Which is exactly what's needed to populate the dentry tree, no?
> > > 
> > > No - you need inodes as well (i.e. as the absolute least you want
> > > mode and ownership).  Which is to say, you need to issue stat on
> > > each component in such situation anyway.  Not a win...
> 
> And actually even that *could* be a win, if the network latency is
> large.  Because by doing the lookup first, the stats can be performed
> in parallel.  So a path with an arbitrary number of components could
> be resolved in just 2 RTTs.

...and NFSv4 could do it in a single RPC call (assuming no symlinks or
submounts).

Cheers
  Trond