[PATCH v1 1/3] sunrpc: take a xprt offline using sysfs

[Olga Kornievskaia <olga.kornievskaia@gmail.com>]

From: Olga Kornievskaia <kolga@netapp.com>

Using sysfs's xprt_state attribute, mark a particular transport offline.
It will not be picked during the round-robin selection. It's not allowed
to take the main (1st created transport associated with the rpc_client)
offline.

Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
---
 include/linux/sunrpc/xprt.h |  2 ++
 net/sunrpc/clnt.c           |  1 +
 net/sunrpc/sysfs.c          | 42 +++++++++++++++++++++++++++++++++----
 net/sunrpc/xprtmultipath.c  |  3 ++-
 4 files changed, 43 insertions(+), 5 deletions(-)

diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
index 13a4eaf385cf..72a858f032c7 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -293,6 +293,7 @@ struct rpc_xprt {
 	struct rcu_head		rcu;
 	const struct xprt_class	*xprt_class;
 	struct rpc_sysfs_xprt	*xprt_sysfs;
+	bool			main; /* marked if it's the 1st transport */
 };
 
 #if defined(CONFIG_SUNRPC_BACKCHANNEL)
@@ -426,6 +427,7 @@ void			xprt_release_write(struct rpc_xprt *, struct rpc_task *);
 #define XPRT_BOUND		(4)
 #define XPRT_BINDING		(5)
 #define XPRT_CLOSING		(6)
+#define XPRT_OFFLINE		(7)
 #define XPRT_CONGESTED		(9)
 #define XPRT_CWND_WAIT		(10)
 #define XPRT_WRITE_SPACE	(11)
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 9bf820bad84c..408618765aa5 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -412,6 +412,7 @@ static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args,
 	}
 
 	rpc_clnt_set_transport(clnt, xprt, timeout);
+	xprt->main = true;
 	xprt_iter_init(&clnt->cl_xpi, xps);
 	xprt_switch_put(xps);
 
diff --git a/net/sunrpc/sysfs.c b/net/sunrpc/sysfs.c
index ec06c9257c07..02c918c5061b 100644
--- a/net/sunrpc/sysfs.c
+++ b/net/sunrpc/sysfs.c
@@ -118,7 +118,7 @@ static ssize_t rpc_sysfs_xprt_state_show(struct kobject *kobj,
 	struct rpc_xprt *xprt = rpc_sysfs_xprt_kobj_get_xprt(kobj);
 	ssize_t ret;
 	int locked, connected, connecting, close_wait, bound, binding,
-	    closing, congested, cwnd_wait, write_space;
+	    closing, congested, cwnd_wait, write_space, offline;
 
 	if (!xprt)
 		return 0;
@@ -136,8 +136,9 @@ static ssize_t rpc_sysfs_xprt_state_show(struct kobject *kobj,
 		congested = test_bit(XPRT_CONGESTED, &xprt->state);
 		cwnd_wait = test_bit(XPRT_CWND_WAIT, &xprt->state);
 		write_space = test_bit(XPRT_WRITE_SPACE, &xprt->state);
+		offline = test_bit(XPRT_OFFLINE, &xprt->state);
 
-		ret = sprintf(buf, "state=%s %s %s %s %s %s %s %s %s %s\n",
+		ret = sprintf(buf, "state=%s %s %s %s %s %s %s %s %s %s %s\n",
 			      locked ? "LOCKED" : "",
 			      connected ? "CONNECTED" : "",
 			      connecting ? "CONNECTING" : "",
@@ -147,7 +148,8 @@ static ssize_t rpc_sysfs_xprt_state_show(struct kobject *kobj,
 			      closing ? "CLOSING" : "",
 			      congested ? "CONGESTED" : "",
 			      cwnd_wait ? "CWND_WAIT" : "",
-			      write_space ? "WRITE_SPACE" : "");
+			      write_space ? "WRITE_SPACE" : "",
+			      offline ? "OFFLINE" : "");
 	}
 
 	xprt_put(xprt);
@@ -223,6 +225,38 @@ static ssize_t rpc_sysfs_xprt_dstaddr_store(struct kobject *kobj,
 	goto out;
 }
 
+static ssize_t rpc_sysfs_xprt_state_change(struct kobject *kobj,
+					   struct kobj_attribute *attr,
+					   const char *buf, size_t count)
+{
+	struct rpc_xprt *xprt = rpc_sysfs_xprt_kobj_get_xprt(kobj);
+	int offline = 0;
+
+	if (!xprt)
+		return 0;
+
+	if (!strncmp(buf, "offline", 7))
+		offline = 1;
+	else
+		return -EINVAL;
+
+	if (wait_on_bit_lock(&xprt->state, XPRT_LOCKED, TASK_KILLABLE)) {
+		count = -EINTR;
+		goto out_put;
+	}
+	if (offline) {
+		if (xprt->main)
+			count = -EINVAL;
+		else
+			set_bit(XPRT_OFFLINE, &xprt->state);
+	}
+
+	xprt_release_write(xprt, NULL);
+out_put:
+	xprt_put(xprt);
+	return count;
+}
+
 int rpc_sysfs_init(void)
 {
 	rpc_sunrpc_kset = kset_create_and_add("sunrpc", NULL, kernel_kobj);
@@ -293,7 +327,7 @@ static struct kobj_attribute rpc_sysfs_xprt_info = __ATTR(xprt_info,
 	0444, rpc_sysfs_xprt_info_show, NULL);
 
 static struct kobj_attribute rpc_sysfs_xprt_change_state = __ATTR(xprt_state,
-	0644, rpc_sysfs_xprt_state_show, NULL);
+	0644, rpc_sysfs_xprt_state_show, rpc_sysfs_xprt_state_change);
 
 static struct attribute *rpc_sysfs_xprt_attrs[] = {
 	&rpc_sysfs_xprt_dstaddr.attr,
diff --git a/net/sunrpc/xprtmultipath.c b/net/sunrpc/xprtmultipath.c
index 07e76ae1028a..39551b794b80 100644
--- a/net/sunrpc/xprtmultipath.c
+++ b/net/sunrpc/xprtmultipath.c
@@ -230,7 +230,8 @@ void xprt_iter_default_rewind(struct rpc_xprt_iter *xpi)
 static
 bool xprt_is_active(const struct rpc_xprt *xprt)
 {
-	return kref_read(&xprt->kref) != 0;
+	return (kref_read(&xprt->kref) != 0 &&
+		!test_bit(XPRT_OFFLINE, &xprt->state));
 }
 
 static
-- 
2.27.0