nfs41: drain session cleanup

Do not wake up the next slot_tbl_waitq task in nfs4_free_slot because we
may be draining the slot. Either signal the state manager that the session
is drained (the state manager wakes up tasks) OR wake up the next task.

In nfs41_sequence_done, the slot dereference is only needed in the sequence
operation success case.
Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4proc.c

@@ -336,7 +336,6 @@ nfs4_free_slot(struct nfs4_slot_table *tbl, u8 free_slotid)
 		else
 			tbl->highest_used_slotid = -1;
 	}
-	rpc_wake_up_next(&tbl->slot_tbl_waitq);
 	spin_unlock(&tbl->slot_tbl_lock);
 	dprintk("%s: free_slotid %u highest_used_slotid %d\n", __func__,
 		free_slotid, tbl->highest_used_slotid);
@@ -353,14 +352,13 @@ void nfs41_sequence_free_slot(const struct nfs_client *clp,
 	}
 	tbl = &clp->cl_session->fc_slot_table;
 	if (res->sr_slotid == NFS4_MAX_SLOT_TABLE) {
-		dprintk("%s: No slot\n", __func__);
 		/* just wake up the next guy waiting since
 		 * we may have not consumed a slot after all */
-		rpc_wake_up_next(&tbl->slot_tbl_waitq);
-		return;
+		dprintk("%s: No slot\n", __func__);
+	} else {
+		nfs4_free_slot(tbl, res->sr_slotid);
+		res->sr_slotid = NFS4_MAX_SLOT_TABLE;
 	}
-	nfs4_free_slot(tbl, res->sr_slotid);
-	res->sr_slotid = NFS4_MAX_SLOT_TABLE;
 
 	/* Signal state manager thread if session is drained */
 	if (test_bit(NFS4CLNT_SESSION_DRAINING, &clp->cl_state)) {
@@ -370,6 +368,8 @@ void nfs41_sequence_free_slot(const struct nfs_client *clp,
 			complete(&clp->cl_session->complete);
 		}
 		spin_unlock(&tbl->slot_tbl_lock);
+	} else {
+		rpc_wake_up_next(&tbl->slot_tbl_waitq);
 	}
 }
 
@@ -394,10 +394,10 @@ static void nfs41_sequence_done(struct nfs_client *clp,
 	if (res->sr_slotid == NFS4_MAX_SLOT_TABLE)
 		goto out;
 
-	tbl = &clp->cl_session->fc_slot_table;
-	slot = tbl->slots + res->sr_slotid;
-
+	/* Check the SEQUENCE operation status */
 	if (res->sr_status == 0) {
+		tbl = &clp->cl_session->fc_slot_table;
+		slot = tbl->slots + res->sr_slotid;
 		/* Update the slot's sequence and clientid lease timer */
 		++slot->seq_nr;
 		timestamp = res->sr_renewal_time;