On Mon, Jun 27, 2016 at 12:07 PM, Jeff Layton <jlayton@xxxxxxxxxx> wrote:
> I'm eyeballing how to make ceph dentry revalidation occur in rcu-walk
> mode in the kernel cephfs client. It looks fairly straightforward, but
> for one thing:
>
> dentry_lease_is_valid queues an asynchronous lease renewal if we're
> halfway to the next lease renewal time:
>
> if (session) {
> ceph_mdsc_lease_send_msg(session, dir, dentry,
> CEPH_MDS_LEASE_RENEW, seq);
> ceph_put_mds_session(session);
> }
>
> That can sleep, so we have to drop out of rcu walk mode in that case.
>
> Is this lease renewal strictly necessary? I can make the code drop out
> of rcuwalk mode and try again in that case, but if this is just an
> opportunistic thing, then it may be better for performance to take a
> pass on renewing the lease early if we're still in RCU walk mode.
I'm just guessing based on the function names (and what I know of the
algorithms), but as long as something *else* will do the renewal, it
shouldn't need to be done here. There's nothing magic about half the
lease time.
-Greg
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