linux-kernel - Re: VFS + path walktrough

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Date:	Mon, 05 May 2008 16:16:39 -0400
From:	Trond Myklebust <trond.myklebust@....uio.no>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	viro@...IV.linux.org.uk, weigelt@...ux.de,
	linux-kernel@...r.kernel.org
Subject: Re: VFS + path walktrough

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

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