> > +	error = VOP_GETATTR(vp, &va, curlwp->l_proc->p_ucred,
> > +	    curlwp->l_proc);
> > 
> > VOP_GETATTR with holding pages busy is not safe with
> > the current implementation of nfs client.
> > 
> 
> OK - do we need to put a lock around this, or just unbusy the pages
> while we check the attributes?

nfs VOP_GETATTR sometimes attempts to grab pages.  it causes deadlock
if you already holds the pages.

> > which is your intention?
> 
> Check pages when they are read in.  I previously had a look at this
> but ran into difficulties working out how to get enough information to
> be able to relate the async callback with a particular vnode so that
> we could get the correct page fingerprints to check against.  I will
> have another look at this as it may be easier with the improvements
> that Elad has made.

when pages are read-in is under the control of each filesystems.
you can't hook it without dealing with filesystem internals.

YAMAMOTO Takashi