NFS: add sysfs shutdown knob

Within each nfs_server sysfs tree, add an entry named "shutdown".  Writing
1 to this file will set the cl_shutdown bit on the rpc_clnt structs
associated with that mount.  If cl_shutdown is set, the task scheduler
immediately returns -EIO for new tasks.
Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/sysfs.c

@@ -12,6 +12,7 @@
 #include <linux/string.h>
 #include <linux/nfs_fs.h>
 #include <linux/rcupdate.h>
+#include <linux/lockd/lockd.h>
 
 #include "nfs4_fs.h"
 #include "netns.h"
@@ -216,6 +217,50 @@ void nfs_netns_sysfs_destroy(struct nfs_net *netns)
 	}
 }
 
+static ssize_t
+shutdown_show(struct kobject *kobj, struct kobj_attribute *attr,
+				char *buf)
+{
+	struct nfs_server *server = container_of(kobj, struct nfs_server, kobj);
+	bool shutdown = server->flags & NFS_MOUNT_SHUTDOWN;
+	return sysfs_emit(buf, "%d\n", shutdown);
+}
+
+static ssize_t
+shutdown_store(struct kobject *kobj, struct kobj_attribute *attr,
+				const char *buf, size_t count)
+{
+	struct nfs_server *server;
+	int ret, val;
+
+	server = container_of(kobj, struct nfs_server, kobj);
+
+	ret = kstrtoint(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	if (val != 1)
+		return -EINVAL;
+
+	/* already shut down? */
+	if (server->flags & NFS_MOUNT_SHUTDOWN)
+		goto out;
+
+	server->flags |= NFS_MOUNT_SHUTDOWN;
+	server->client->cl_shutdown = 1;
+	server->nfs_client->cl_rpcclient->cl_shutdown = 1;
+
+	if (!IS_ERR(server->client_acl))
+		server->client_acl->cl_shutdown = 1;
+
+	if (server->nlm_host)
+		server->nlm_host->h_rpcclnt->cl_shutdown = 1;
+out:
+	return count;
+}
+
+static struct kobj_attribute nfs_sysfs_attr_shutdown = __ATTR_RW(shutdown);
+
 #define RPC_CLIENT_NAME_SIZE 64
 
 void nfs_sysfs_link_rpc_client(struct nfs_server *server,
@@ -259,9 +304,16 @@ void nfs_sysfs_add_server(struct nfs_server *server)
 
 	ret = kobject_init_and_add(&server->kobj, &nfs_sb_ktype,
 				&nfs_kset->kobj, "server-%d", server->s_sysfs_id);
-	if (ret < 0)
+	if (ret < 0) {
 		pr_warn("NFS: nfs sysfs add server-%d failed (%d)\n",
 					server->s_sysfs_id, ret);
+		return;
+	}
+	ret = sysfs_create_file_ns(&server->kobj, &nfs_sysfs_attr_shutdown.attr,
+				nfs_netns_server_namespace(&server->kobj));
+	if (ret < 0)
+		pr_warn("NFS: sysfs_create_file_ns for server-%d failed (%d)\n",
+			server->s_sysfs_id, ret);
 }
 EXPORT_SYMBOL_GPL(nfs_sysfs_add_server);
 

include/linux/nfs_fs_sb.h

@@ -154,6 +154,7 @@ struct nfs_server {
 #define NFS_MOUNT_WRITE_EAGER		0x01000000
 #define NFS_MOUNT_WRITE_WAIT		0x02000000
 #define NFS_MOUNT_TRUNK_DISCOVERY	0x04000000
+#define NFS_MOUNT_SHUTDOWN			0x08000000
 
 	unsigned int		fattr_valid;	/* Valid attributes */
 	unsigned int		caps;		/* server capabilities */

include/linux/sunrpc/clnt.h

@@ -63,7 +63,8 @@ struct rpc_clnt {
 				cl_discrtry : 1,/* disconnect before retry */
 				cl_noretranstimeo: 1,/* No retransmit timeouts */
 				cl_autobind : 1,/* use getport() */
-				cl_chatty   : 1;/* be verbose */
+				cl_chatty   : 1,/* be verbose */
+				cl_shutdown : 1;/* rpc immediate -EIO */
 	struct xprtsec_parms	cl_xprtsec;	/* transport security policy */
 
 	struct rpc_rtt *	cl_rtt;		/* RTO estimator data */

net/sunrpc/clnt.c

@@ -1724,6 +1724,11 @@ call_start(struct rpc_task *task)
 
 	trace_rpc_request(task);
 
+	if (task->tk_client->cl_shutdown) {
+		rpc_call_rpcerror(task, -EIO);
+		return;
+	}
+
 	/* Increment call count (version might not be valid for ping) */
 	if (clnt->cl_program->version[clnt->cl_vers])
 		clnt->cl_program->version[clnt->cl_vers]->counts[idx]++;