sunrpc: add dst_attr attributes to the sysfs xprt directory

Allow to query and set the destination's address of a transport.
Setting of the destination address is allowed only for TCP or RDMA
based connections.
Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

include/linux/sunrpc/xprt.h

@@ -414,6 +414,7 @@ void			xprt_conditional_disconnect(struct rpc_xprt *xprt, unsigned int cookie);
 
 bool			xprt_lock_connect(struct rpc_xprt *, struct rpc_task *, void *);
 void			xprt_unlock_connect(struct rpc_xprt *, void *);
+void			xprt_release_write(struct rpc_xprt *, struct rpc_task *);
 
 /*
  * Reserved bit positions in xprt->state

net/sunrpc/sysfs.c

@@ -4,8 +4,23 @@
  */
 #include <linux/sunrpc/clnt.h>
 #include <linux/kobject.h>
+#include <linux/sunrpc/addr.h>
+
 #include "sysfs.h"
 
+struct xprt_addr {
+	const char *addr;
+	struct rcu_head rcu;
+};
+
+static void free_xprt_addr(struct rcu_head *head)
+{
+	struct xprt_addr *addr = container_of(head, struct xprt_addr, rcu);
+
+	kfree(addr->addr);
+	kfree(addr);
+}
+
 static struct kset *rpc_sunrpc_kset;
 static struct kobject *rpc_sunrpc_client_kobj, *rpc_sunrpc_xprt_switch_kobj;
 
@@ -43,6 +58,87 @@ static struct kobject *rpc_sysfs_object_alloc(const char *name,
 	return NULL;
 }
 
+static inline struct rpc_xprt *
+rpc_sysfs_xprt_kobj_get_xprt(struct kobject *kobj)
+{
+	struct rpc_sysfs_xprt *x = container_of(kobj,
+		struct rpc_sysfs_xprt, kobject);
+
+	return xprt_get(x->xprt);
+}
+
+static ssize_t rpc_sysfs_xprt_dstaddr_show(struct kobject *kobj,
+					   struct kobj_attribute *attr,
+					   char *buf)
+{
+	struct rpc_xprt *xprt = rpc_sysfs_xprt_kobj_get_xprt(kobj);
+	ssize_t ret;
+
+	if (!xprt)
+		return 0;
+	ret = sprintf(buf, "%s\n", xprt->address_strings[RPC_DISPLAY_ADDR]);
+	xprt_put(xprt);
+	return ret + 1;
+}
+
+static ssize_t rpc_sysfs_xprt_dstaddr_store(struct kobject *kobj,
+					    struct kobj_attribute *attr,
+					    const char *buf, size_t count)
+{
+	struct rpc_xprt *xprt = rpc_sysfs_xprt_kobj_get_xprt(kobj);
+	struct sockaddr *saddr;
+	char *dst_addr;
+	int port;
+	struct xprt_addr *saved_addr;
+	size_t buf_len;
+
+	if (!xprt)
+		return 0;
+	if (!(xprt->xprt_class->ident == XPRT_TRANSPORT_TCP ||
+	      xprt->xprt_class->ident == XPRT_TRANSPORT_RDMA)) {
+		xprt_put(xprt);
+		return -EOPNOTSUPP;
+	}
+
+	if (wait_on_bit_lock(&xprt->state, XPRT_LOCKED, TASK_KILLABLE)) {
+		count = -EINTR;
+		goto out_put;
+	}
+	saddr = (struct sockaddr *)&xprt->addr;
+	port = rpc_get_port(saddr);
+
+	/* buf_len is the len until the first occurence of either
+	 * '\n' or '\0'
+	 */
+	buf_len = strcspn(buf, "\n");
+
+	dst_addr = kstrndup(buf, buf_len, GFP_KERNEL);
+	if (!dst_addr)
+		goto out_err;
+	saved_addr = kzalloc(sizeof(*saved_addr), GFP_KERNEL);
+	if (!saved_addr)
+		goto out_err_free;
+	saved_addr->addr =
+		rcu_dereference_raw(xprt->address_strings[RPC_DISPLAY_ADDR]);
+	rcu_assign_pointer(xprt->address_strings[RPC_DISPLAY_ADDR], dst_addr);
+	call_rcu(&saved_addr->rcu, free_xprt_addr);
+	xprt->addrlen = rpc_pton(xprt->xprt_net, buf, buf_len, saddr,
+				 sizeof(*saddr));
+	rpc_set_port(saddr, port);
+
+	xprt_force_disconnect(xprt);
+out:
+	xprt_release_write(xprt, NULL);
+out_put:
+	xprt_put(xprt);
+	return count;
+out_err_free:
+	kfree(dst_addr);
+out_err:
+	count = -ENOMEM;
+	goto out;
+}
+
 int rpc_sysfs_init(void)
 {
 	rpc_sunrpc_kset = kset_create_and_add("sunrpc", NULL, kernel_kobj);
@@ -106,6 +202,14 @@ static const void *rpc_sysfs_xprt_namespace(struct kobject *kobj)
 			    kobject)->xprt->xprt_net;
 }
 
+static struct kobj_attribute rpc_sysfs_xprt_dstaddr = __ATTR(dstaddr,
+	0644, rpc_sysfs_xprt_dstaddr_show, rpc_sysfs_xprt_dstaddr_store);
+
+static struct attribute *rpc_sysfs_xprt_attrs[] = {
+	&rpc_sysfs_xprt_dstaddr.attr,
+	NULL,
+};
+
 static struct kobj_type rpc_sysfs_client_type = {
 	.release = rpc_sysfs_client_release,
 	.sysfs_ops = &kobj_sysfs_ops,
@@ -120,6 +224,7 @@ static struct kobj_type rpc_sysfs_xprt_switch_type = {
 
 static struct kobj_type rpc_sysfs_xprt_type = {
 	.release = rpc_sysfs_xprt_release,
+	.default_attrs = rpc_sysfs_xprt_attrs,
 	.sysfs_ops = &kobj_sysfs_ops,
 	.namespace = rpc_sysfs_xprt_namespace,
 };

net/sunrpc/xprt.c

@@ -55,6 +55,7 @@
 #include <trace/events/sunrpc.h>
 
 #include "sunrpc.h"
+#include "sysfs.h"
 
 /*
  * Local variables
@@ -443,7 +444,7 @@ void xprt_release_xprt_cong(struct rpc_xprt *xprt, struct rpc_task *task)
 }
 EXPORT_SYMBOL_GPL(xprt_release_xprt_cong);
 
-static inline void xprt_release_write(struct rpc_xprt *xprt, struct rpc_task *task)
+void xprt_release_write(struct rpc_xprt *xprt, struct rpc_task *task)
 {
 	if (xprt->snd_task != task)
 		return;
@@ -1812,6 +1813,7 @@ void xprt_free(struct rpc_xprt *xprt)
 	put_net(xprt->xprt_net);
 	xprt_free_all_slots(xprt);
 	xprt_free_id(xprt);
+	rpc_sysfs_xprt_destroy(xprt);
 	kfree_rcu(xprt, rcu);
 }
 EXPORT_SYMBOL_GPL(xprt_free);

net/sunrpc/xprtmultipath.c

@@ -86,7 +86,6 @@ void rpc_xprt_switch_remove_xprt(struct rpc_xprt_switch *xps,
 	spin_lock(&xps->xps_lock);
 	xprt_switch_remove_xprt_locked(xps, xprt);
 	spin_unlock(&xps->xps_lock);
-	rpc_sysfs_xprt_destroy(xprt);
 	xprt_put(xprt);
 }
 
@@ -155,7 +154,6 @@ static void xprt_switch_free_entries(struct rpc_xprt_switch *xps)
 				struct rpc_xprt, xprt_switch);
 		xprt_switch_remove_xprt_locked(xps, xprt);
 		spin_unlock(&xps->xps_lock);
-		rpc_sysfs_xprt_destroy(xprt);
 		xprt_put(xprt);
 		spin_lock(&xps->xps_lock);
 	}