ceph: monitor client

The monitor cluster is responsible for managing cluster membership
and state.  The monitor client handles what minimal interaction
the Ceph client has with it: checking for updated versions of the
MDS and OSD maps, getting statfs() information, and unmounting.

Signed-off-by: Sage Weil <sage@newdream.net>

2 files changed, 803 insertions, 0 deletions

diff --git a/fs/ceph/mon_client.c b/fs/ceph/mon_client.c
new file mode 100644
index 000000000000..b0c95cec5df8
--- /dev/null
+++ b/fs/ceph/mon_client.c
@@ -0,0 +1,694 @@
+#include "ceph_debug.h"
+
+#include <linux/types.h>
+#include <linux/random.h>
+#include <linux/sched.h>
+
+#include "mon_client.h"
+#include "super.h"
+#include "decode.h"
+
+/*
+ * Interact with Ceph monitor cluster.  Handle requests for new map
+ * versions, and periodically resend as needed.  Also implement
+ * statfs() and umount().
+ *
+ * A small cluster of Ceph "monitors" are responsible for managing critical
+ * cluster configuration and state information.  An odd number (e.g., 3, 5)
+ * of cmon daemons use a modified version of the Paxos part-time parliament
+ * algorithm to manage the MDS map (mds cluster membership), OSD map, and
+ * list of clients who have mounted the file system.
+ *
+ * We maintain an open, active session with a monitor at all times in order to
+ * receive timely MDSMap updates.  We periodically send a keepalive byte on the
+ * TCP socket to ensure we detect a failure.  If the connection does break, we
+ * randomly hunt for a new monitor.  Once the connection is reestablished, we
+ * resend any outstanding requests.
+ */
+
+const static struct ceph_connection_operations mon_con_ops;
+
+/*
+ * Decode a monmap blob (e.g., during mount).
+ */
+struct ceph_monmap *ceph_monmap_decode(void *p, void *end)
+{
+	struct ceph_monmap *m = NULL;
+	int i, err = -EINVAL;
+	struct ceph_fsid fsid;
+	u32 epoch, num_mon;
+	u16 version;
+
+	dout("monmap_decode %p %p len %d\n", p, end, (int)(end-p));
+
+	ceph_decode_16_safe(&p, end, version, bad);
+
+	ceph_decode_need(&p, end, sizeof(fsid) + 2*sizeof(u32), bad);
+	ceph_decode_copy(&p, &fsid, sizeof(fsid));
+	ceph_decode_32(&p, epoch);
+
+	ceph_decode_32(&p, num_mon);
+	ceph_decode_need(&p, end, num_mon*sizeof(m->mon_inst[0]), bad);
+
+	if (num_mon >= CEPH_MAX_MON)
+		goto bad;
+	m = kmalloc(sizeof(*m) + sizeof(m->mon_inst[0])*num_mon, GFP_NOFS);
+	if (m == NULL)
+		return ERR_PTR(-ENOMEM);
+	m->fsid = fsid;
+	m->epoch = epoch;
+	m->num_mon = num_mon;
+	ceph_decode_copy(&p, m->mon_inst, num_mon*sizeof(m->mon_inst[0]));
+
+	if (p != end)
+		goto bad;
+
+	dout("monmap_decode epoch %d, num_mon %d\n", m->epoch,
+	     m->num_mon);
+	for (i = 0; i < m->num_mon; i++)
+		dout("monmap_decode  mon%d is %s\n", i,
+		     pr_addr(&m->mon_inst[i].addr.in_addr));
+	return m;
+
+bad:
+	dout("monmap_decode failed with %d\n", err);
+	kfree(m);
+	return ERR_PTR(err);
+}
+
+/*
+ * return true if *addr is included in the monmap.
+ */
+int ceph_monmap_contains(struct ceph_monmap *m, struct ceph_entity_addr *addr)
+{
+	int i;
+
+	for (i = 0; i < m->num_mon; i++)
+		if (ceph_entity_addr_equal(addr, &m->mon_inst[i].addr))
+			return 1;
+	return 0;
+}
+
+/*
+ * Close monitor session, if any.
+ */
+static void __close_session(struct ceph_mon_client *monc)
+{
+	if (monc->con) {
+		dout("__close_session closing mon%d\n", monc->cur_mon);
+		ceph_con_close(monc->con);
+		monc->cur_mon = -1;
+	}
+}
+
+/*
+ * Open a session with a (new) monitor.
+ */
+static int __open_session(struct ceph_mon_client *monc)
+{
+	char r;
+
+	if (monc->cur_mon < 0) {
+		get_random_bytes(&r, 1);
+		monc->cur_mon = r % monc->monmap->num_mon;
+		dout("open_session num=%d r=%d -> mon%d\n",
+		     monc->monmap->num_mon, r, monc->cur_mon);
+		monc->sub_sent = 0;
+		monc->sub_renew_after = jiffies;  /* i.e., expired */
+		monc->want_next_osdmap = !!monc->want_next_osdmap;
+
+		dout("open_session mon%d opening\n", monc->cur_mon);
+		monc->con->peer_name.type = CEPH_ENTITY_TYPE_MON;
+		monc->con->peer_name.num = cpu_to_le64(monc->cur_mon);
+		ceph_con_open(monc->con,
+			      &monc->monmap->mon_inst[monc->cur_mon].addr);
+	} else {
+		dout("open_session mon%d already open\n", monc->cur_mon);
+	}
+	return 0;
+}
+
+static bool __sub_expired(struct ceph_mon_client *monc)
+{
+	return time_after_eq(jiffies, monc->sub_renew_after);
+}
+
+/*
+ * Reschedule delayed work timer.
+ */
+static void __schedule_delayed(struct ceph_mon_client *monc)
+{
+	unsigned delay;
+
+	if (monc->cur_mon < 0 || monc->want_mount || __sub_expired(monc))
+		delay = 10 * HZ;
+	else
+		delay = 20 * HZ;
+	dout("__schedule_delayed after %u\n", delay);
+	schedule_delayed_work(&monc->delayed_work, delay);
+}
+
+/*
+ * Send subscribe request for mdsmap and/or osdmap.
+ */
+static void __send_subscribe(struct ceph_mon_client *monc)
+{
+	dout("__send_subscribe sub_sent=%u exp=%u want_osd=%d\n",
+	     (unsigned)monc->sub_sent, __sub_expired(monc),
+	     monc->want_next_osdmap);
+	if ((__sub_expired(monc) && !monc->sub_sent) ||
+	    monc->want_next_osdmap == 1) {
+		struct ceph_msg *msg;
+		struct ceph_mon_subscribe_item *i;
+		void *p, *end;
+
+		msg = ceph_msg_new(CEPH_MSG_MON_SUBSCRIBE, 64, 0, 0, NULL);
+		if (!msg)
+			return;
+
+		p = msg->front.iov_base;
+		end = p + msg->front.iov_len;
+
+		dout("__send_subscribe to 'mdsmap' %u+\n",
+		     (unsigned)monc->have_mdsmap);
+		if (monc->want_next_osdmap) {
+			dout("__send_subscribe to 'osdmap' %u\n",
+			     (unsigned)monc->have_osdmap);
+			ceph_encode_32(&p, 2);
+			ceph_encode_string(&p, end, "osdmap", 6);
+			i = p;
+			i->have = cpu_to_le64(monc->have_osdmap);
+			i->onetime = 1;
+			p += sizeof(*i);
+			monc->want_next_osdmap = 2;  /* requested */
+		} else {
+			ceph_encode_32(&p, 1);
+		}
+		ceph_encode_string(&p, end, "mdsmap", 6);
+		i = p;
+		i->have = cpu_to_le64(monc->have_mdsmap);
+		i->onetime = 0;
+		p += sizeof(*i);
+
+		msg->front.iov_len = p - msg->front.iov_base;
+		msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);
+		ceph_con_send(monc->con, msg);
+
+		monc->sub_sent = jiffies | 1;  /* never 0 */
+	}
+}
+
+static void handle_subscribe_ack(struct ceph_mon_client *monc,
+				 struct ceph_msg *msg)
+{
+	unsigned seconds;
+	void *p = msg->front.iov_base;
+	void *end = p + msg->front.iov_len;
+
+	ceph_decode_32_safe(&p, end, seconds, bad);
+	mutex_lock(&monc->mutex);
+	if (monc->hunting) {
+		pr_info("mon%d %s session established\n",
+			monc->cur_mon, pr_addr(&monc->con->peer_addr.in_addr));
+		monc->hunting = false;
+	}
+	dout("handle_subscribe_ack after %d seconds\n", seconds);
+	monc->sub_renew_after = monc->sub_sent + seconds*HZ - 1;
+	monc->sub_sent = 0;
+	mutex_unlock(&monc->mutex);
+	return;
+bad:
+	pr_err("got corrupt subscribe-ack msg\n");
+}
+
+/*
+ * Keep track of which maps we have
+ */
+int ceph_monc_got_mdsmap(struct ceph_mon_client *monc, u32 got)
+{
+	mutex_lock(&monc->mutex);
+	monc->have_mdsmap = got;
+	mutex_unlock(&monc->mutex);
+	return 0;
+}
+
+int ceph_monc_got_osdmap(struct ceph_mon_client *monc, u32 got)
+{
+	mutex_lock(&monc->mutex);
+	monc->have_osdmap = got;
+	monc->want_next_osdmap = 0;
+	mutex_unlock(&monc->mutex);
+	return 0;
+}
+
+/*
+ * Register interest in the next osdmap
+ */
+void ceph_monc_request_next_osdmap(struct ceph_mon_client *monc)
+{
+	dout("request_next_osdmap have %u\n", monc->have_osdmap);
+	mutex_lock(&monc->mutex);
+	if (!monc->want_next_osdmap)
+		monc->want_next_osdmap = 1;
+	if (monc->want_next_osdmap < 2)
+		__send_subscribe(monc);
+	mutex_unlock(&monc->mutex);
+}
+
+
+/*
+ * mount
+ */
+static void __request_mount(struct ceph_mon_client *monc)
+{
+	struct ceph_msg *msg;
+	struct ceph_client_mount *h;
+	int err;
+
+	dout("__request_mount\n");
+	err = __open_session(monc);
+	if (err)
+		return;
+	msg = ceph_msg_new(CEPH_MSG_CLIENT_MOUNT, sizeof(*h), 0, 0, NULL);
+	if (IS_ERR(msg))
+		return;
+	h = msg->front.iov_base;
+	h->have_version = 0;
+	ceph_con_send(monc->con, msg);
+}
+
+int ceph_monc_request_mount(struct ceph_mon_client *monc)
+{
+	if (!monc->con) {
+		monc->con = kmalloc(sizeof(*monc->con), GFP_KERNEL);
+		if (!monc->con)
+			return -ENOMEM;
+		ceph_con_init(monc->client->msgr, monc->con);
+		monc->con->private = monc;
+		monc->con->ops = &mon_con_ops;
+	}
+
+	mutex_lock(&monc->mutex);
+	__request_mount(monc);
+	__schedule_delayed(monc);
+	mutex_unlock(&monc->mutex);
+	return 0;
+}
+
+/*
+ * The monitor responds with mount ack indicate mount success.  The
+ * included client ticket allows the client to talk to MDSs and OSDs.
+ */
+static void handle_mount_ack(struct ceph_mon_client *monc, struct ceph_msg *msg)
+{
+	struct ceph_client *client = monc->client;
+	struct ceph_monmap *monmap = NULL, *old = monc->monmap;
+	void *p, *end;
+	s32 result;
+	u32 len;
+	s64 cnum;
+	int err = -EINVAL;
+
+	if (client->whoami >= 0) {
+		dout("handle_mount_ack - already mounted\n");
+		return;
+	}
+
+	mutex_lock(&monc->mutex);
+
+	dout("handle_mount_ack\n");
+	p = msg->front.iov_base;
+	end = p + msg->front.iov_len;
+
+	ceph_decode_64_safe(&p, end, cnum, bad);
+	ceph_decode_32_safe(&p, end, result, bad);
+	ceph_decode_32_safe(&p, end, len, bad);
+	if (result) {
+		pr_err("mount denied: %.*s (%d)\n", len, (char *)p,
+		       result);
+		err = result;
+		goto out;
+	}
+	p += len;
+
+	ceph_decode_32_safe(&p, end, len, bad);
+	ceph_decode_need(&p, end, len, bad);
+	monmap = ceph_monmap_decode(p, p + len);
+	if (IS_ERR(monmap)) {
+		pr_err("problem decoding monmap, %d\n",
+		       (int)PTR_ERR(monmap));
+		err = -EINVAL;
+		goto out;
+	}
+	p += len;
+
+	client->monc.monmap = monmap;
+	kfree(old);
+
+	client->signed_ticket = NULL;
+	client->signed_ticket_len = 0;
+
+	monc->want_mount = false;
+
+	client->whoami = cnum;
+	client->msgr->inst.name.type = CEPH_ENTITY_TYPE_CLIENT;
+	client->msgr->inst.name.num = cpu_to_le64(cnum);
+	pr_info("client%lld fsid " FSID_FORMAT "\n",
+		client->whoami, PR_FSID(&client->monc.monmap->fsid));
+
+	ceph_debugfs_client_init(client);
+	__send_subscribe(monc);
+
+	err = 0;
+	goto out;
+
+bad:
+	pr_err("error decoding mount_ack message\n");
+out:
+	client->mount_err = err;
+	mutex_unlock(&monc->mutex);
+	wake_up(&client->mount_wq);
+}
+
+
+
+
+/*
+ * statfs
+ */
+static void handle_statfs_reply(struct ceph_mon_client *monc,
+				struct ceph_msg *msg)
+{
+	struct ceph_mon_statfs_request *req;
+	struct ceph_mon_statfs_reply *reply = msg->front.iov_base;
+	u64 tid;
+
+	if (msg->front.iov_len != sizeof(*reply))
+		goto bad;
+	tid = le64_to_cpu(reply->tid);
+	dout("handle_statfs_reply %p tid %llu\n", msg, tid);
+
+	mutex_lock(&monc->mutex);
+	req = radix_tree_lookup(&monc->statfs_request_tree, tid);
+	if (req) {
+		*req->buf = reply->st;
+		req->result = 0;
+	}
+	mutex_unlock(&monc->mutex);
+	if (req)
+		complete(&req->completion);
+	return;
+
+bad:
+	pr_err("corrupt statfs reply, no tid\n");
+}
+
+/*
+ * (re)send a statfs request
+ */
+static int send_statfs(struct ceph_mon_client *monc,
+		       struct ceph_mon_statfs_request *req)
+{
+	struct ceph_msg *msg;
+	struct ceph_mon_statfs *h;
+	int err;
+
+	dout("send_statfs tid %llu\n", req->tid);
+	err = __open_session(monc);
+	if (err)
+		return err;
+	msg = ceph_msg_new(CEPH_MSG_STATFS, sizeof(*h), 0, 0, NULL);
+	if (IS_ERR(msg))
+		return PTR_ERR(msg);
+	req->request = msg;
+	h = msg->front.iov_base;
+	h->have_version = 0;
+	h->fsid = monc->monmap->fsid;
+	h->tid = cpu_to_le64(req->tid);
+	ceph_con_send(monc->con, msg);
+	return 0;
+}
+
+/*
+ * Do a synchronous statfs().
+ */
+int ceph_monc_do_statfs(struct ceph_mon_client *monc, struct ceph_statfs *buf)
+{
+	struct ceph_mon_statfs_request req;
+	int err;
+
+	req.buf = buf;
+	init_completion(&req.completion);
+
+	/* allocate memory for reply */
+	err = ceph_msgpool_resv(&monc->msgpool_statfs_reply, 1);
+	if (err)
+		return err;
+
+	/* register request */
+	mutex_lock(&monc->mutex);
+	req.tid = ++monc->last_tid;
+	req.last_attempt = jiffies;
+	req.delay = BASE_DELAY_INTERVAL;
+	if (radix_tree_insert(&monc->statfs_request_tree, req.tid, &req) < 0) {
+		mutex_unlock(&monc->mutex);
+		pr_err("ENOMEM in do_statfs\n");
+		return -ENOMEM;
+	}
+	monc->num_statfs_requests++;
+	mutex_unlock(&monc->mutex);
+
+	/* send request and wait */
+	err = send_statfs(monc, &req);
+	if (!err)
+		err = wait_for_completion_interruptible(&req.completion);
+
+	mutex_lock(&monc->mutex);
+	radix_tree_delete(&monc->statfs_request_tree, req.tid);
+	monc->num_statfs_requests--;
+	ceph_msgpool_resv(&monc->msgpool_statfs_reply, -1);
+	mutex_unlock(&monc->mutex);
+
+	if (!err)
+		err = req.result;
+	return err;
+}
+
+/*
+ * Resend pending statfs requests.
+ */
+static void __resend_statfs(struct ceph_mon_client *monc)
+{
+	u64 next_tid = 0;
+	int got;
+	int did = 0;
+	struct ceph_mon_statfs_request *req;
+
+	while (1) {
+		got = radix_tree_gang_lookup(&monc->statfs_request_tree,
+					     (void **)&req,
+					     next_tid, 1);
+		if (got == 0)
+			break;
+		did++;
+		next_tid = req->tid + 1;
+
+		send_statfs(monc, req);
+	}
+}
+
+/*
+ * Delayed work.  If we haven't mounted yet, retry.  Otherwise,
+ * renew/retry subscription as needed (in case it is timing out, or we
+ * got an ENOMEM).  And keep the monitor connection alive.
+ */
+static void delayed_work(struct work_struct *work)
+{
+	struct ceph_mon_client *monc =
+		container_of(work, struct ceph_mon_client, delayed_work.work);
+
+	dout("monc delayed_work\n");
+	mutex_lock(&monc->mutex);
+	if (monc->want_mount) {
+		__request_mount(monc);
+	} else {
+		if (__sub_expired(monc)) {
+			__close_session(monc);
+			__open_session(monc);  /* continue hunting */
+		} else {
+			ceph_con_keepalive(monc->con);
+		}
+	}
+	__send_subscribe(monc);
+	__schedule_delayed(monc);
+	mutex_unlock(&monc->mutex);
+}
+
+int ceph_monc_init(struct ceph_mon_client *monc, struct ceph_client *cl)
+{
+	int err = 0;
+
+	dout("init\n");
+	memset(monc, 0, sizeof(*monc));
+	monc->client = cl;
+	monc->monmap = NULL;
+	mutex_init(&monc->mutex);
+
+	monc->con = NULL;
+
+	/* msg pools */
+	err = ceph_msgpool_init(&monc->msgpool_mount_ack, 4096, 1, false);
+	if (err < 0)
+		goto out;
+	err = ceph_msgpool_init(&monc->msgpool_subscribe_ack, 8, 1, false);
+	if (err < 0)
+		goto out;
+	err = ceph_msgpool_init(&monc->msgpool_statfs_reply,
+				sizeof(struct ceph_mon_statfs_reply), 0, false);
+	if (err < 0)
+		goto out;
+
+	monc->cur_mon = -1;
+	monc->hunting = false;  /* not really */
+	monc->sub_renew_after = jiffies;
+	monc->sub_sent = 0;
+
+	INIT_DELAYED_WORK(&monc->delayed_work, delayed_work);
+	INIT_RADIX_TREE(&monc->statfs_request_tree, GFP_NOFS);
+	monc->num_statfs_requests = 0;
+	monc->last_tid = 0;
+
+	monc->have_mdsmap = 0;
+	monc->have_osdmap = 0;
+	monc->want_next_osdmap = 1;
+	monc->want_mount = true;
+out:
+	return err;
+}
+
+void ceph_monc_stop(struct ceph_mon_client *monc)
+{
+	dout("stop\n");
+	cancel_delayed_work_sync(&monc->delayed_work);
+
+	mutex_lock(&monc->mutex);
+	__close_session(monc);
+	if (monc->con) {
+		monc->con->private = NULL;
+		monc->con->ops->put(monc->con);
+		monc->con = NULL;
+	}
+	mutex_unlock(&monc->mutex);
+
+	ceph_msgpool_destroy(&monc->msgpool_mount_ack);
+	ceph_msgpool_destroy(&monc->msgpool_subscribe_ack);
+	ceph_msgpool_destroy(&monc->msgpool_statfs_reply);
+
+	kfree(monc->monmap);
+}
+
+
+/*
+ * handle incoming message
+ */
+static void dispatch(struct ceph_connection *con, struct ceph_msg *msg)
+{
+	struct ceph_mon_client *monc = con->private;
+	int type = le16_to_cpu(msg->hdr.type);
+
+	if (!monc)
+		return;
+
+	switch (type) {
+	case CEPH_MSG_CLIENT_MOUNT_ACK:
+		handle_mount_ack(monc, msg);
+		break;
+
+	case CEPH_MSG_MON_SUBSCRIBE_ACK:
+		handle_subscribe_ack(monc, msg);
+		break;
+
+	case CEPH_MSG_STATFS_REPLY:
+		handle_statfs_reply(monc, msg);
+		break;
+
+	case CEPH_MSG_MDS_MAP:
+		ceph_mdsc_handle_map(&monc->client->mdsc, msg);
+		break;
+
+	case CEPH_MSG_OSD_MAP:
+		ceph_osdc_handle_map(&monc->client->osdc, msg);
+		break;
+
+	default:
+		pr_err("received unknown message type %d %s\n", type,
+		       ceph_msg_type_name(type));
+	}
+	ceph_msg_put(msg);
+}
+
+/*
+ * Allocate memory for incoming message
+ */
+static struct ceph_msg *mon_alloc_msg(struct ceph_connection *con,
+				      struct ceph_msg_header *hdr)
+{
+	struct ceph_mon_client *monc = con->private;
+	int type = le16_to_cpu(hdr->type);
+
+	switch (type) {
+	case CEPH_MSG_CLIENT_MOUNT_ACK:
+		return ceph_msgpool_get(&monc->msgpool_mount_ack);
+	case CEPH_MSG_MON_SUBSCRIBE_ACK:
+		return ceph_msgpool_get(&monc->msgpool_subscribe_ack);
+	case CEPH_MSG_STATFS_REPLY:
+		return ceph_msgpool_get(&monc->msgpool_statfs_reply);
+	}
+	return ceph_alloc_msg(con, hdr);
+}
+
+/*
+ * If the monitor connection resets, pick a new monitor and resubmit
+ * any pending requests.
+ */
+static void mon_fault(struct ceph_connection *con)
+{
+	struct ceph_mon_client *monc = con->private;
+
+	if (!monc)
+		return;
+
+	dout("mon_fault\n");
+	mutex_lock(&monc->mutex);
+	if (!con->private)
+		goto out;
+
+	if (monc->con && !monc->hunting)
+		pr_info("mon%d %s session lost, "
+			"hunting for new mon\n", monc->cur_mon,
+			pr_addr(&monc->con->peer_addr.in_addr));
+
+	__close_session(monc);
+	if (!monc->hunting) {
+		/* start hunting */
+		monc->hunting = true;
+		if (__open_session(monc) == 0) {
+			__send_subscribe(monc);
+			__resend_statfs(monc);
+		}
+	} else {
+		/* already hunting, let's wait a bit */
+		__schedule_delayed(monc);
+	}
+out:
+	mutex_unlock(&monc->mutex);
+}
+
+const static struct ceph_connection_operations mon_con_ops = {
+	.get = ceph_con_get,
+	.put = ceph_con_put,
+	.dispatch = dispatch,
+	.fault = mon_fault,
+	.alloc_msg = mon_alloc_msg,
+	.alloc_middle = ceph_alloc_middle,
+};
diff --git a/fs/ceph/mon_client.h b/fs/ceph/mon_client.h
new file mode 100644
index 000000000000..5258c5693b03
--- /dev/null
+++ b/fs/ceph/mon_client.h
@@ -0,0 +1,109 @@
+#ifndef _FS_CEPH_MON_CLIENT_H
+#define _FS_CEPH_MON_CLIENT_H
+
+#include <linux/completion.h>
+#include <linux/radix-tree.h>
+
+#include "messenger.h"
+#include "msgpool.h"
+
+struct ceph_client;
+struct ceph_mount_args;
+
+/*
+ * The monitor map enumerates the set of all monitors.
+ */
+struct ceph_monmap {
+	struct ceph_fsid fsid;
+	u32 epoch;
+	u32 num_mon;
+	struct ceph_entity_inst mon_inst[0];
+};
+
+struct ceph_mon_client;
+struct ceph_mon_statfs_request;
+
+
+/*
+ * Generic mechanism for resending monitor requests.
+ */
+typedef void (*ceph_monc_request_func_t)(struct ceph_mon_client *monc,
+					 int newmon);
+
+/* a pending monitor request */
+struct ceph_mon_request {
+	struct ceph_mon_client *monc;
+	struct delayed_work delayed_work;
+	unsigned long delay;
+	ceph_monc_request_func_t do_request;
+};
+
+/*
+ * statfs() is done a bit differently because we need to get data back
+ * to the caller
+ */
+struct ceph_mon_statfs_request {
+	u64 tid;
+	int result;
+	struct ceph_statfs *buf;
+	struct completion completion;
+	unsigned long last_attempt, delay; /* jiffies */
+	struct ceph_msg *request;  /* original request */
+};
+
+struct ceph_mon_client {
+	struct ceph_client *client;
+	struct ceph_monmap *monmap;
+
+	struct mutex mutex;
+	struct delayed_work delayed_work;
+
+	bool hunting;
+	int cur_mon;                       /* last monitor i contacted */
+	unsigned long sub_sent, sub_renew_after;
+	struct ceph_connection *con;
+
+	/* msg pools */
+	struct ceph_msgpool msgpool_mount_ack;
+	struct ceph_msgpool msgpool_subscribe_ack;
+	struct ceph_msgpool msgpool_statfs_reply;
+
+	/* pending statfs requests */
+	struct radix_tree_root statfs_request_tree;
+	int num_statfs_requests;
+	u64 last_tid;
+
+	/* mds/osd map or mount requests */
+	bool want_mount;
+	int want_next_osdmap; /* 1 = want, 2 = want+asked */
+	u32 have_osdmap, have_mdsmap;
+
+	struct dentry *debugfs_file;
+};
+
+extern struct ceph_monmap *ceph_monmap_decode(void *p, void *end);
+extern int ceph_monmap_contains(struct ceph_monmap *m,
+				struct ceph_entity_addr *addr);
+
+extern int ceph_monc_init(struct ceph_mon_client *monc, struct ceph_client *cl);
+extern void ceph_monc_stop(struct ceph_mon_client *monc);
+
+/*
+ * The model here is to indicate that we need a new map of at least
+ * epoch @want, and also call in when we receive a map.  We will
+ * periodically rerequest the map from the monitor cluster until we
+ * get what we want.
+ */
+extern int ceph_monc_got_mdsmap(struct ceph_mon_client *monc, u32 have);
+extern int ceph_monc_got_osdmap(struct ceph_mon_client *monc, u32 have);
+
+extern void ceph_monc_request_next_osdmap(struct ceph_mon_client *monc);
+
+extern int ceph_monc_request_mount(struct ceph_mon_client *monc);
+
+extern int ceph_monc_do_statfs(struct ceph_mon_client *monc,
+			       struct ceph_statfs *buf);
+
+
+
+#endif