Re: [PATCH 09/14] NFS: Force server to drop NFSv4 state

["J. Bruce Fields" <bfields@fieldses.org>]

On Mon, May 21, 2012 at 12:11:48PM -0400, Chuck Lever wrote:
> 
> On May 21, 2012, at 12:08 PM, J. Bruce Fields wrote:
> 
> > On Fri, May 18, 2012 at 06:06:33PM -0400, Chuck Lever wrote:
> >> @@ -3937,8 +3937,13 @@ static void nfs4_construct_boot_verifier(struct nfs_client *clp,
> >> {
> >> 	__be32 verf[2];
> >> 
> >> -	verf[0] = (__be32)clp->cl_boot_time.tv_sec;
> >> -	verf[1] = (__be32)clp->cl_boot_time.tv_nsec;
> >> +	if (test_bit(NFS4CLNT_PURGE_STATE, &clp->cl_state)) {
> >> +		verf[0] = (__be32)CURRENT_TIME.tv_sec;
> >> +		verf[1] = (__be32)CURRENT_TIME.tv_nsec;
> > 
> > I suppose it's pretty unlikely this could happen within a jiffy of
> > setting cl_boot_time?
> 
> Boot time has nanosecond resolution.  I'm pretty sure we are safe here.

CURRENT_TIME is only updated every jiffy.  It would still have to happen
ridiculously fast, but I think that's milliseconds rather than
nanoseconds.

> > Would it be simpler to use some special value (all-zeros?) instead?
> 
> We'd have to pick a value that was guaranteed never to be a valid time stamp.

A client that thinks it's currently Jan. 1 1970 probably has bigger
problems.

I dunno, your call.

--b.