Re: [NFS] Cache flushing

[Timo Sirainen <tss@iki.fi>]

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On Wed, 2007-11-21 at 15:39 -0500, Trond Myklebust wrote:
> On Wed, 2007-11-21 at 22:36 +0200, Timo Sirainen wrote:
> > On 21.11.2007, at 15.56, Trond Myklebust wrote:
> > 
> > > On Wed, 2007-11-21 at 15:14 +0200, Timo Sirainen wrote:
> > >
> > >> Now that I think of it, I guess the reason is that my 2.6.22 setup  
> > >> has
> > >> Linux+ext3 as NFS server and 2.6.17-rc2 setup has NetApp as  
> > >> server. So
> > >> even though open()+close() flushes the directory's attribute  
> > >> cache, it
> > >> doesn't flush the file name -> NFS handle cache unless mtime changes?
> > >
> > > Right. You're hitting the principal limitation of ext3 as an NFS  
> > > backend
> > > filesystem.
> > > As I said in an earlier mail, the resolution on the time is 1  
> > > second, so
> > > client 2 can basically not see any changes that happen within < 1  
> > > second
> > > on client 1. The reason is that the mtime stays the same.
> > 
> > With files it's possible to work around this limitation with fcntl  
> > locking, but directories can't be locked. So back to my original  
> > question: Would it be possible to have chmod(dir, (uid_t)-1,  
> > (gid_t)-1) flush its cache? I don't see what harm there could be in  
> > this, since normally no-one would do it anyway and the change is simple-
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