NFSD: Skip sending CB_RECALL_ANY when the backchannel isn't up

NFSD sends CB_RECALL_ANY to clients when the server is low on
memory or that client has a large number of delegations outstanding.

We've seen cases where NFSD attempts to send CB_RECALL_ANY requests
to disconnected clients, and gets confused. These calls never go
anywhere if a backchannel transport to the target client isn't
available. Before the server can send any backchannel operation, the
client has to connect first and then do a BIND_CONN_TO_SESSION.

This patch doesn't address the root cause of the confusion, but
there's no need to queue up these optional operations if they can't
go anywhere.

Fixes: 44df6f439a17 ("NFSD: add delegation reaper to react to low memory condition")
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index cb6baff8abf847becd3c62c4be501b4faf514e1a..b42e2ab7a042239c1809ead5f39195ed8675d088 100644 (file)
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -6861,14 +6861,19 @@ deleg_reaper(struct nfsd_net *nn)
        spin_lock(&nn->client_lock);
        list_for_each_safe(pos, next, &nn->client_lru) {
                clp = list_entry(pos, struct nfs4_client, cl_lru);
-               if (clp->cl_state != NFSD4_ACTIVE ||
-                       list_empty(&clp->cl_delegations) ||
-                       atomic_read(&clp->cl_delegs_in_recall) ||
-                       test_bit(NFSD4_CLIENT_CB_RECALL_ANY, &clp->cl_flags) ||
-                       (ktime_get_boottime_seconds() -
-                               clp->cl_ra_time < 5)) {
+
+               if (clp->cl_state != NFSD4_ACTIVE)
+                       continue;
+               if (list_empty(&clp->cl_delegations))
+                       continue;
+               if (atomic_read(&clp->cl_delegs_in_recall))
+                       continue;
+               if (test_bit(NFSD4_CLIENT_CB_RECALL_ANY, &clp->cl_flags))
+                       continue;
+               if (ktime_get_boottime_seconds() - clp->cl_ra_time < 5)
+                       continue;
+               if (clp->cl_cb_state != NFSD4_CB_UP)
                        continue;
-               }
                list_add(&clp->cl_ra_cblist, &cblist);
 
                /* release in nfsd4_cb_recall_any_release */