NFSv4.1 dereference a disconnected data server client record

When the last DS io is processed, the data server client record will be
freed.
Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4filelayout.c

@@ -196,6 +196,7 @@ static int filelayout_async_handle_error(struct rpc_task *task,
 			_pnfs_return_layout(state->inode);
 		filelayout_mark_devid_invalid(devid);
 		rpc_wake_up(&tbl->slot_tbl_waitq);
+		nfs4_ds_disconnect(clp);
 		/* fall through */
 	default:
 		dprintk("%s Retry through MDS. Error %d\n", __func__,

fs/nfs/nfs4filelayout.h

@@ -146,5 +146,6 @@ extern void nfs4_fl_put_deviceid(struct nfs4_file_layout_dsaddr *dsaddr);
 extern void nfs4_fl_free_deviceid(struct nfs4_file_layout_dsaddr *dsaddr);
 struct nfs4_file_layout_dsaddr *
 get_device_info(struct inode *inode, struct nfs4_deviceid *dev_id, gfp_t gfp_flags);
+void nfs4_ds_disconnect(struct nfs_client *clp);
 
 #endif /* FS_NFS_NFS4FILELAYOUT_H */

fs/nfs/nfs4filelayoutdev.c

@@ -148,6 +148,28 @@ _data_server_lookup_locked(const struct list_head *dsaddrs)
 	return NULL;
 }
 
+/*
+ * Lookup DS by nfs_client pointer. Zero data server client pointer
+ */
+void nfs4_ds_disconnect(struct nfs_client *clp)
+{
+	struct nfs4_pnfs_ds *ds;
+	struct nfs_client *found = NULL;
+
+	dprintk("%s clp %p\n", __func__, clp);
+	spin_lock(&nfs4_ds_cache_lock);
+	list_for_each_entry(ds, &nfs4_data_server_cache, ds_node)
+		if (ds->ds_clp && ds->ds_clp == clp) {
+			found = ds->ds_clp;
+			ds->ds_clp = NULL;
+		}
+	spin_unlock(&nfs4_ds_cache_lock);
+	if (found) {
+		set_bit(NFS_CS_STOP_RENEW, &clp->cl_res_state);
+		nfs_put_client(clp);
+	}
+}
+
 /*
  * Create an rpc connection to the nfs4_pnfs_ds data server
  * Currently only supports IPv4 and IPv6 addresses