On Tue, Apr 03, 2012 at 08:14:39AM -0400, Jeff Layton wrote:
> The main reason for the grace period is to prevent the server from
> allowing an operation that might otherwise be denied once the client has
> reclaimed all of its stateful objects.
>
> Currently, the grace period handling in the nfsd/lockd server code is
> very simple. When the lock managers start, they stick an entry on a list
> and set a timer. When the timers pop, then they remove the entry from
> the list. The locks_in_grace check just looks to see if the list is
> empty. If it is, then the grace period is considered to be over.
>
> This is insufficient for a clustered filesystem that is being served
> from multiple nodes at the same time. In such a configuration, the grace
> period must be coordinated in some fashion, or else one node might hand
> out stateful objects that conflict with those that have not yet been
> reclaimed.
>
> This patch paves the way for fixing this by adding a new export
> operation called locks_in_grace that takes a superblock argument. The
> existing locks_in_grace function is renamed to generic_locks_in_grace,
> and a new locks_in_grace function that takes a superblock arg is added.
> If a filesystem does not have a locks_in_grace export operation then the
> generic version will be used.
Looks more or less OK to me....
> Care has also been taken to reorder calls such that locks_in_grace is
> called last in compound conditional statements. Handling this for
> clustered filesystems may involve upcalls, so we don't want to call it
> unnecessarily.
Even if we're careful to do the check last, we potentially still have to
do it on every otherwise-succesful open and lock operation.
And really I don't think it's too much to ask that this be fast.
> @@ -3183,7 +3183,7 @@ nfs4_laundromat(void)
> nfs4_lock_state();
>
> dprintk("NFSD: laundromat service - starting\n");
> - if (locks_in_grace())
> + if (generic_locks_in_grace())
> nfsd4_end_grace();
Looking at the code.... This is really just checking whether we've ended
our own grace period. The laundromat's scheduled to run a grace period
after startup. So I think we should just make this:
static bool grace_ended = false;
if (!grace_ended) {
grace_ended = true;
nfsd4_end_grace();
}
or something. No reason not to do that now.
(Hm, and maybe there's a reason to: locks_in_grace() could in theory
still return true on a second run of nfs4_laundromat(), but
nfsd4_end_grace() probably shouldn't really be run twice?)
--b.
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
