Merge commit 'v2.6.34-rc2' into for-2.6.34

1 files changed, 3021 insertions, 0 deletions

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
new file mode 100644
index 0000000..a260010
--- /dev/null
+++ b/fs/ceph/mds_client.c
@@ -0,0 +1,3021 @@
+#include "ceph_debug.h"
+
+#include <linux/wait.h>
+#include <linux/sched.h>
+
+#include "mds_client.h"
+#include "mon_client.h"
+#include "super.h"
+#include "messenger.h"
+#include "decode.h"
+#include "auth.h"
+#include "pagelist.h"
+
+/*
+ * A cluster of MDS (metadata server) daemons is responsible for
+ * managing the file system namespace (the directory hierarchy and
+ * inodes) and for coordinating shared access to storage.  Metadata is
+ * partitioning hierarchically across a number of servers, and that
+ * partition varies over time as the cluster adjusts the distribution
+ * in order to balance load.
+ *
+ * The MDS client is primarily responsible to managing synchronous
+ * metadata requests for operations like open, unlink, and so forth.
+ * If there is a MDS failure, we find out about it when we (possibly
+ * request and) receive a new MDS map, and can resubmit affected
+ * requests.
+ *
+ * For the most part, though, we take advantage of a lossless
+ * communications channel to the MDS, and do not need to worry about
+ * timing out or resubmitting requests.
+ *
+ * We maintain a stateful "session" with each MDS we interact with.
+ * Within each session, we sent periodic heartbeat messages to ensure
+ * any capabilities or leases we have been issues remain valid.  If
+ * the session times out and goes stale, our leases and capabilities
+ * are no longer valid.
+ */
+
+static void __wake_requests(struct ceph_mds_client *mdsc,
+			    struct list_head *head);
+
+const static struct ceph_connection_operations mds_con_ops;
+
+
+/*
+ * mds reply parsing
+ */
+
+/*
+ * parse individual inode info
+ */
+static int parse_reply_info_in(void **p, void *end,
+			       struct ceph_mds_reply_info_in *info)
+{
+	int err = -EIO;
+
+	info->in = *p;
+	*p += sizeof(struct ceph_mds_reply_inode) +
+		sizeof(*info->in->fragtree.splits) *
+		le32_to_cpu(info->in->fragtree.nsplits);
+
+	ceph_decode_32_safe(p, end, info->symlink_len, bad);
+	ceph_decode_need(p, end, info->symlink_len, bad);
+	info->symlink = *p;
+	*p += info->symlink_len;
+
+	ceph_decode_32_safe(p, end, info->xattr_len, bad);
+	ceph_decode_need(p, end, info->xattr_len, bad);
+	info->xattr_data = *p;
+	*p += info->xattr_len;
+	return 0;
+bad:
+	return err;
+}
+
+/*
+ * parse a normal reply, which may contain a (dir+)dentry and/or a
+ * target inode.
+ */
+static int parse_reply_info_trace(void **p, void *end,
+				  struct ceph_mds_reply_info_parsed *info)
+{
+	int err;
+
+	if (info->head->is_dentry) {
+		err = parse_reply_info_in(p, end, &info->diri);
+		if (err < 0)
+			goto out_bad;
+
+		if (unlikely(*p + sizeof(*info->dirfrag) > end))
+			goto bad;
+		info->dirfrag = *p;
+		*p += sizeof(*info->dirfrag) +
+			sizeof(u32)*le32_to_cpu(info->dirfrag->ndist);
+		if (unlikely(*p > end))
+			goto bad;
+
+		ceph_decode_32_safe(p, end, info->dname_len, bad);
+		ceph_decode_need(p, end, info->dname_len, bad);
+		info->dname = *p;
+		*p += info->dname_len;
+		info->dlease = *p;
+		*p += sizeof(*info->dlease);
+	}
+
+	if (info->head->is_target) {
+		err = parse_reply_info_in(p, end, &info->targeti);
+		if (err < 0)
+			goto out_bad;
+	}
+
+	if (unlikely(*p != end))
+		goto bad;
+	return 0;
+
+bad:
+	err = -EIO;
+out_bad:
+	pr_err("problem parsing mds trace %d\n", err);
+	return err;
+}
+
+/*
+ * parse readdir results
+ */
+static int parse_reply_info_dir(void **p, void *end,
+				struct ceph_mds_reply_info_parsed *info)
+{
+	u32 num, i = 0;
+	int err;
+
+	info->dir_dir = *p;
+	if (*p + sizeof(*info->dir_dir) > end)
+		goto bad;
+	*p += sizeof(*info->dir_dir) +
+		sizeof(u32)*le32_to_cpu(info->dir_dir->ndist);
+	if (*p > end)
+		goto bad;
+
+	ceph_decode_need(p, end, sizeof(num) + 2, bad);
+	num = ceph_decode_32(p);
+	info->dir_end = ceph_decode_8(p);
+	info->dir_complete = ceph_decode_8(p);
+	if (num == 0)
+		goto done;
+
+	/* alloc large array */
+	info->dir_nr = num;
+	info->dir_in = kcalloc(num, sizeof(*info->dir_in) +
+			       sizeof(*info->dir_dname) +
+			       sizeof(*info->dir_dname_len) +
+			       sizeof(*info->dir_dlease),
+			       GFP_NOFS);
+	if (info->dir_in == NULL) {
+		err = -ENOMEM;
+		goto out_bad;
+	}
+	info->dir_dname = (void *)(info->dir_in + num);
+	info->dir_dname_len = (void *)(info->dir_dname + num);
+	info->dir_dlease = (void *)(info->dir_dname_len + num);
+
+	while (num) {
+		/* dentry */
+		ceph_decode_need(p, end, sizeof(u32)*2, bad);
+		info->dir_dname_len[i] = ceph_decode_32(p);
+		ceph_decode_need(p, end, info->dir_dname_len[i], bad);
+		info->dir_dname[i] = *p;
+		*p += info->dir_dname_len[i];
+		dout("parsed dir dname '%.*s'\n", info->dir_dname_len[i],
+		     info->dir_dname[i]);
+		info->dir_dlease[i] = *p;
+		*p += sizeof(struct ceph_mds_reply_lease);
+
+		/* inode */
+		err = parse_reply_info_in(p, end, &info->dir_in[i]);
+		if (err < 0)
+			goto out_bad;
+		i++;
+		num--;
+	}
+
+done:
+	if (*p != end)
+		goto bad;
+	return 0;
+
+bad:
+	err = -EIO;
+out_bad:
+	pr_err("problem parsing dir contents %d\n", err);
+	return err;
+}
+
+/*
+ * parse entire mds reply
+ */
+static int parse_reply_info(struct ceph_msg *msg,
+			    struct ceph_mds_reply_info_parsed *info)
+{
+	void *p, *end;
+	u32 len;
+	int err;
+
+	info->head = msg->front.iov_base;
+	p = msg->front.iov_base + sizeof(struct ceph_mds_reply_head);
+	end = p + msg->front.iov_len - sizeof(struct ceph_mds_reply_head);
+
+	/* trace */
+	ceph_decode_32_safe(&p, end, len, bad);
+	if (len > 0) {
+		err = parse_reply_info_trace(&p, p+len, info);
+		if (err < 0)
+			goto out_bad;
+	}
+
+	/* dir content */
+	ceph_decode_32_safe(&p, end, len, bad);
+	if (len > 0) {
+		err = parse_reply_info_dir(&p, p+len, info);
+		if (err < 0)
+			goto out_bad;
+	}
+
+	/* snap blob */
+	ceph_decode_32_safe(&p, end, len, bad);
+	info->snapblob_len = len;
+	info->snapblob = p;
+	p += len;
+
+	if (p != end)
+		goto bad;
+	return 0;
+
+bad:
+	err = -EIO;
+out_bad:
+	pr_err("mds parse_reply err %d\n", err);
+	return err;
+}
+
+static void destroy_reply_info(struct ceph_mds_reply_info_parsed *info)
+{
+	kfree(info->dir_in);
+}
+
+
+/*
+ * sessions
+ */
+static const char *session_state_name(int s)
+{
+	switch (s) {
+	case CEPH_MDS_SESSION_NEW: return "new";
+	case CEPH_MDS_SESSION_OPENING: return "opening";
+	case CEPH_MDS_SESSION_OPEN: return "open";
+	case CEPH_MDS_SESSION_HUNG: return "hung";
+	case CEPH_MDS_SESSION_CLOSING: return "closing";
+	case CEPH_MDS_SESSION_RESTARTING: return "restarting";
+	case CEPH_MDS_SESSION_RECONNECTING: return "reconnecting";
+	default: return "???";
+	}
+}
+
+static struct ceph_mds_session *get_session(struct ceph_mds_session *s)
+{
+	if (atomic_inc_not_zero(&s->s_ref)) {
+		dout("mdsc get_session %p %d -> %d\n", s,
+		     atomic_read(&s->s_ref)-1, atomic_read(&s->s_ref));
+		return s;
+	} else {
+		dout("mdsc get_session %p 0 -- FAIL", s);
+		return NULL;
+	}
+}
+
+void ceph_put_mds_session(struct ceph_mds_session *s)
+{
+	dout("mdsc put_session %p %d -> %d\n", s,
+	     atomic_read(&s->s_ref), atomic_read(&s->s_ref)-1);
+	if (atomic_dec_and_test(&s->s_ref)) {
+		if (s->s_authorizer)
+			s->s_mdsc->client->monc.auth->ops->destroy_authorizer(
+				s->s_mdsc->client->monc.auth, s->s_authorizer);
+		kfree(s);
+	}
+}
+
+/*
+ * called under mdsc->mutex
+ */
+struct ceph_mds_session *__ceph_lookup_mds_session(struct ceph_mds_client *mdsc,
+						   int mds)
+{
+	struct ceph_mds_session *session;
+
+	if (mds >= mdsc->max_sessions || mdsc->sessions[mds] == NULL)
+		return NULL;
+	session = mdsc->sessions[mds];
+	dout("lookup_mds_session %p %d\n", session,
+	     atomic_read(&session->s_ref));
+	get_session(session);
+	return session;
+}
+
+static bool __have_session(struct ceph_mds_client *mdsc, int mds)
+{
+	if (mds >= mdsc->max_sessions)
+		return false;
+	return mdsc->sessions[mds];
+}
+
+static int __verify_registered_session(struct ceph_mds_client *mdsc,
+				       struct ceph_mds_session *s)
+{
+	if (s->s_mds >= mdsc->max_sessions ||
+	    mdsc->sessions[s->s_mds] != s)
+		return -ENOENT;
+	return 0;
+}
+
+/*
+ * create+register a new session for given mds.
+ * called under mdsc->mutex.
+ */
+static struct ceph_mds_session *register_session(struct ceph_mds_client *mdsc,
+						 int mds)
+{
+	struct ceph_mds_session *s;
+
+	s = kzalloc(sizeof(*s), GFP_NOFS);
+	s->s_mdsc = mdsc;
+	s->s_mds = mds;
+	s->s_state = CEPH_MDS_SESSION_NEW;
+	s->s_ttl = 0;
+	s->s_seq = 0;
+	mutex_init(&s->s_mutex);
+
+	ceph_con_init(mdsc->client->msgr, &s->s_con);
+	s->s_con.private = s;
+	s->s_con.ops = &mds_con_ops;
+	s->s_con.peer_name.type = CEPH_ENTITY_TYPE_MDS;
+	s->s_con.peer_name.num = cpu_to_le64(mds);
+
+	spin_lock_init(&s->s_cap_lock);
+	s->s_cap_gen = 0;
+	s->s_cap_ttl = 0;
+	s->s_renew_requested = 0;
+	s->s_renew_seq = 0;
+	INIT_LIST_HEAD(&s->s_caps);
+	s->s_nr_caps = 0;
+	s->s_trim_caps = 0;
+	atomic_set(&s->s_ref, 1);
+	INIT_LIST_HEAD(&s->s_waiting);
+	INIT_LIST_HEAD(&s->s_unsafe);
+	s->s_num_cap_releases = 0;
+	s->s_cap_iterator = NULL;
+	INIT_LIST_HEAD(&s->s_cap_releases);
+	INIT_LIST_HEAD(&s->s_cap_releases_done);
+	INIT_LIST_HEAD(&s->s_cap_flushing);
+	INIT_LIST_HEAD(&s->s_cap_snaps_flushing);
+
+	dout("register_session mds%d\n", mds);
+	if (mds >= mdsc->max_sessions) {
+		int newmax = 1 << get_count_order(mds+1);
+		struct ceph_mds_session **sa;
+
+		dout("register_session realloc to %d\n", newmax);
+		sa = kcalloc(newmax, sizeof(void *), GFP_NOFS);
+		if (sa == NULL)
+			goto fail_realloc;
+		if (mdsc->sessions) {
+			memcpy(sa, mdsc->sessions,
+			       mdsc->max_sessions * sizeof(void *));
+			kfree(mdsc->sessions);
+		}
+		mdsc->sessions = sa;
+		mdsc->max_sessions = newmax;
+	}
+	mdsc->sessions[mds] = s;
+	atomic_inc(&s->s_ref);  /* one ref to sessions[], one to caller */
+
+	ceph_con_open(&s->s_con, ceph_mdsmap_get_addr(mdsc->mdsmap, mds));
+
+	return s;
+
+fail_realloc:
+	kfree(s);
+	return ERR_PTR(-ENOMEM);
+}
+
+/*
+ * called under mdsc->mutex
+ */
+static void __unregister_session(struct ceph_mds_client *mdsc,
+			       struct ceph_mds_session *s)
+{
+	dout("__unregister_session mds%d %p\n", s->s_mds, s);
+	BUG_ON(mdsc->sessions[s->s_mds] != s);
+	mdsc->sessions[s->s_mds] = NULL;
+	ceph_con_close(&s->s_con);
+	ceph_put_mds_session(s);
+}
+
+/*
+ * drop session refs in request.
+ *
+ * should be last request ref, or hold mdsc->mutex
+ */
+static void put_request_session(struct ceph_mds_request *req)
+{
+	if (req->r_session) {
+		ceph_put_mds_session(req->r_session);
+		req->r_session = NULL;
+	}
+}
+
+void ceph_mdsc_release_request(struct kref *kref)
+{
+	struct ceph_mds_request *req = container_of(kref,
+						    struct ceph_mds_request,
+						    r_kref);
+	if (req->r_request)
+		ceph_msg_put(req->r_request);
+	if (req->r_reply) {
+		ceph_msg_put(req->r_reply);
+		destroy_reply_info(&req->r_reply_info);
+	}
+	if (req->r_inode) {
+		ceph_put_cap_refs(ceph_inode(req->r_inode),
+				  CEPH_CAP_PIN);
+		iput(req->r_inode);
+	}
+	if (req->r_locked_dir)
+		ceph_put_cap_refs(ceph_inode(req->r_locked_dir),
+				  CEPH_CAP_PIN);
+	if (req->r_target_inode)
+		iput(req->r_target_inode);
+	if (req->r_dentry)
+		dput(req->r_dentry);
+	if (req->r_old_dentry) {
+		ceph_put_cap_refs(
+			ceph_inode(req->r_old_dentry->d_parent->d_inode),
+			CEPH_CAP_PIN);
+		dput(req->r_old_dentry);
+	}
+	kfree(req->r_path1);
+	kfree(req->r_path2);
+	put_request_session(req);
+	ceph_unreserve_caps(&req->r_caps_reservation);
+	kfree(req);
+}
+
+/*
+ * lookup session, bump ref if found.
+ *
+ * called under mdsc->mutex.
+ */
+static struct ceph_mds_request *__lookup_request(struct ceph_mds_client *mdsc,
+					     u64 tid)
+{
+	struct ceph_mds_request *req;
+	struct rb_node *n = mdsc->request_tree.rb_node;
+
+	while (n) {
+		req = rb_entry(n, struct ceph_mds_request, r_node);
+		if (tid < req->r_tid)
+			n = n->rb_left;
+		else if (tid > req->r_tid)
+			n = n->rb_right;
+		else {
+			ceph_mdsc_get_request(req);
+			return req;
+		}
+	}
+	return NULL;
+}
+
+static void __insert_request(struct ceph_mds_client *mdsc,
+			     struct ceph_mds_request *new)
+{
+	struct rb_node **p = &mdsc->request_tree.rb_node;
+	struct rb_node *parent = NULL;
+	struct ceph_mds_request *req = NULL;
+
+	while (*p) {
+		parent = *p;
+		req = rb_entry(parent, struct ceph_mds_request, r_node);
+		if (new->r_tid < req->r_tid)
+			p = &(*p)->rb_left;
+		else if (new->r_tid > req->r_tid)
+			p = &(*p)->rb_right;
+		else
+			BUG();
+	}
+
+	rb_link_node(&new->r_node, parent, p);
+	rb_insert_color(&new->r_node, &mdsc->request_tree);
+}
+
+/*
+ * Register an in-flight request, and assign a tid.  Link to directory
+ * are modifying (if any).
+ *
+ * Called under mdsc->mutex.
+ */
+static void __register_request(struct ceph_mds_client *mdsc,
+			       struct ceph_mds_request *req,
+			       struct inode *dir)
+{
+	req->r_tid = ++mdsc->last_tid;
+	if (req->r_num_caps)
+		ceph_reserve_caps(&req->r_caps_reservation, req->r_num_caps);
+	dout("__register_request %p tid %lld\n", req, req->r_tid);
+	ceph_mdsc_get_request(req);
+	__insert_request(mdsc, req);
+
+	if (dir) {
+		struct ceph_inode_info *ci = ceph_inode(dir);
+
+		spin_lock(&ci->i_unsafe_lock);
+		req->r_unsafe_dir = dir;
+		list_add_tail(&req->r_unsafe_dir_item, &ci->i_unsafe_dirops);
+		spin_unlock(&ci->i_unsafe_lock);
+	}
+}
+
+static void __unregister_request(struct ceph_mds_client *mdsc,
+				 struct ceph_mds_request *req)
+{
+	dout("__unregister_request %p tid %lld\n", req, req->r_tid);
+	rb_erase(&req->r_node, &mdsc->request_tree);
+	ceph_mdsc_put_request(req);
+
+	if (req->r_unsafe_dir) {
+		struct ceph_inode_info *ci = ceph_inode(req->r_unsafe_dir);
+
+		spin_lock(&ci->i_unsafe_lock);
+		list_del_init(&req->r_unsafe_dir_item);
+		spin_unlock(&ci->i_unsafe_lock);
+	}
+}
+
+/*
+ * Choose mds to send request to next.  If there is a hint set in the
+ * request (e.g., due to a prior forward hint from the mds), use that.
+ * Otherwise, consult frag tree and/or caps to identify the
+ * appropriate mds.  If all else fails, choose randomly.
+ *
+ * Called under mdsc->mutex.
+ */
+static int __choose_mds(struct ceph_mds_client *mdsc,
+			struct ceph_mds_request *req)
+{
+	struct inode *inode;
+	struct ceph_inode_info *ci;
+	struct ceph_cap *cap;
+	int mode = req->r_direct_mode;
+	int mds = -1;
+	u32 hash = req->r_direct_hash;
+	bool is_hash = req->r_direct_is_hash;
+
+	/*
+	 * is there a specific mds we should try?  ignore hint if we have
+	 * no session and the mds is not up (active or recovering).
+	 */
+	if (req->r_resend_mds >= 0 &&
+	    (__have_session(mdsc, req->r_resend_mds) ||
+	     ceph_mdsmap_get_state(mdsc->mdsmap, req->r_resend_mds) > 0)) {
+		dout("choose_mds using resend_mds mds%d\n",
+		     req->r_resend_mds);
+		return req->r_resend_mds;
+	}
+
+	if (mode == USE_RANDOM_MDS)
+		goto random;
+
+	inode = NULL;
+	if (req->r_inode) {
+		inode = req->r_inode;
+	} else if (req->r_dentry) {
+		if (req->r_dentry->d_inode) {
+			inode = req->r_dentry->d_inode;
+		} else {
+			inode = req->r_dentry->d_parent->d_inode;
+			hash = req->r_dentry->d_name.hash;
+			is_hash = true;
+		}
+	}
+	dout("__choose_mds %p is_hash=%d (%d) mode %d\n", inode, (int)is_hash,
+	     (int)hash, mode);
+	if (!inode)
+		goto random;
+	ci = ceph_inode(inode);
+
+	if (is_hash && S_ISDIR(inode->i_mode)) {
+		struct ceph_inode_frag frag;
+		int found;
+
+		ceph_choose_frag(ci, hash, &frag, &found);
+		if (found) {
+			if (mode == USE_ANY_MDS && frag.ndist > 0) {
+				u8 r;
+
+				/* choose a random replica */
+				get_random_bytes(&r, 1);
+				r %= frag.ndist;
+				mds = frag.dist[r];
+				dout("choose_mds %p %llx.%llx "
+				     "frag %u mds%d (%d/%d)\n",
+				     inode, ceph_vinop(inode),
+				     frag.frag, frag.mds,
+				     (int)r, frag.ndist);
+				return mds;
+			}
+
+			/* since this file/dir wasn't known to be
+			 * replicated, then we want to look for the
+			 * authoritative mds. */
+			mode = USE_AUTH_MDS;
+			if (frag.mds >= 0) {
+				/* choose auth mds */
+				mds = frag.mds;
+				dout("choose_mds %p %llx.%llx "
+				     "frag %u mds%d (auth)\n",
+				     inode, ceph_vinop(inode), frag.frag, mds);
+				return mds;
+			}
+		}
+	}
+
+	spin_lock(&inode->i_lock);
+	cap = NULL;
+	if (mode == USE_AUTH_MDS)
+		cap = ci->i_auth_cap;
+	if (!cap && !RB_EMPTY_ROOT(&ci->i_caps))
+		cap = rb_entry(rb_first(&ci->i_caps), struct ceph_cap, ci_node);
+	if (!cap) {
+		spin_unlock(&inode->i_lock);
+		goto random;
+	}
+	mds = cap->session->s_mds;
+	dout("choose_mds %p %llx.%llx mds%d (%scap %p)\n",
+	     inode, ceph_vinop(inode), mds,
+	     cap == ci->i_auth_cap ? "auth " : "", cap);
+	spin_unlock(&inode->i_lock);
+	return mds;
+
+random:
+	mds = ceph_mdsmap_get_random_mds(mdsc->mdsmap);
+	dout("choose_mds chose random mds%d\n", mds);
+	return mds;
+}
+
+
+/*
+ * session messages
+ */
+static struct ceph_msg *create_session_msg(u32 op, u64 seq)
+{
+	struct ceph_msg *msg;
+	struct ceph_mds_session_head *h;
+
+	msg = ceph_msg_new(CEPH_MSG_CLIENT_SESSION, sizeof(*h), 0, 0, NULL);
+	if (IS_ERR(msg)) {
+		pr_err("create_session_msg ENOMEM creating msg\n");
+		return ERR_PTR(PTR_ERR(msg));
+	}
+	h = msg->front.iov_base;
+	h->op = cpu_to_le32(op);
+	h->seq = cpu_to_le64(seq);
+	return msg;
+}
+
+/*
+ * send session open request.
+ *
+ * called under mdsc->mutex
+ */
+static int __open_session(struct ceph_mds_client *mdsc,
+			  struct ceph_mds_session *session)
+{
+	struct ceph_msg *msg;
+	int mstate;
+	int mds = session->s_mds;
+	int err = 0;
+
+	/* wait for mds to go active? */
+	mstate = ceph_mdsmap_get_state(mdsc->mdsmap, mds);
+	dout("open_session to mds%d (%s)\n", mds,
+	     ceph_mds_state_name(mstate));
+	session->s_state = CEPH_MDS_SESSION_OPENING;
+	session->s_renew_requested = jiffies;
+
+	/* send connect message */
+	msg = create_session_msg(CEPH_SESSION_REQUEST_OPEN, session->s_seq);
+	if (IS_ERR(msg)) {
+		err = PTR_ERR(msg);
+		goto out;
+	}
+	ceph_con_send(&session->s_con, msg);
+
+out:
+	return 0;
+}
+
+/*
+ * session caps
+ */
+
+/*
+ * Free preallocated cap messages assigned to this session
+ */
+static void cleanup_cap_releases(struct ceph_mds_session *session)
+{
+	struct ceph_msg *msg;
+
+	spin_lock(&session->s_cap_lock);
+	while (!list_empty(&session->s_cap_releases)) {
+		msg = list_first_entry(&session->s_cap_releases,
+				       struct ceph_msg, list_head);
+		list_del_init(&msg->list_head);
+		ceph_msg_put(msg);
+	}
+	while (!list_empty(&session->s_cap_releases_done)) {
+		msg = list_first_entry(&session->s_cap_releases_done,
+				       struct ceph_msg, list_head);
+		list_del_init(&msg->list_head);
+		ceph_msg_put(msg);
+	}
+	spin_unlock(&session->s_cap_lock);
+}
+
+/*
+ * Helper to safely iterate over all caps associated with a session.
+ *
+ * caller must hold session s_mutex
+ */
+static int iterate_session_caps(struct ceph_mds_session *session,
+				 int (*cb)(struct inode *, struct ceph_cap *,
+					    void *), void *arg)
+{
+	struct list_head *p;
+	struct ceph_cap *cap;
+	struct inode *inode, *last_inode = NULL;
+	struct ceph_cap *old_cap = NULL;
+	int ret;
+
+	dout("iterate_session_caps %p mds%d\n", session, session->s_mds);
+	spin_lock(&session->s_cap_lock);
+	p = session->s_caps.next;
+	while (p != &session->s_caps) {
+		cap = list_entry(p, struct ceph_cap, session_caps);
+		inode = igrab(&cap->ci->vfs_inode);
+		if (!inode) {
+			p = p->next;
+			continue;
+		}
+		session->s_cap_iterator = cap;
+		spin_unlock(&session->s_cap_lock);
+
+		if (last_inode) {
+			iput(last_inode);
+			last_inode = NULL;
+		}
+		if (old_cap) {
+			ceph_put_cap(old_cap);
+			old_cap = NULL;
+		}
+
+		ret = cb(inode, cap, arg);
+		last_inode = inode;
+
+		spin_lock(&session->s_cap_lock);
+		p = p->next;
+		if (cap->ci == NULL) {
+			dout("iterate_session_caps  finishing cap %p removal\n",
+			     cap);
+			BUG_ON(cap->session != session);
+			list_del_init(&cap->session_caps);
+			session->s_nr_caps--;
+			cap->session = NULL;
+			old_cap = cap;  /* put_cap it w/o locks held */
+		}
+		if (ret < 0)
+			goto out;
+	}
+	ret = 0;
+out:
+	session->s_cap_iterator = NULL;
+	spin_unlock(&session->s_cap_lock);
+
+	if (last_inode)
+		iput(last_inode);
+	if (old_cap)
+		ceph_put_cap(old_cap);
+
+	return ret;
+}
+
+static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap,
+				   void *arg)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	dout("removing cap %p, ci is %p, inode is %p\n",
+	     cap, ci, &ci->vfs_inode);
+	ceph_remove_cap(cap);
+	return 0;
+}
+
+/*
+ * caller must hold session s_mutex
+ */
+static void remove_session_caps(struct ceph_mds_session *session)
+{
+	dout("remove_session_caps on %p\n", session);
+	iterate_session_caps(session, remove_session_caps_cb, NULL);
+	BUG_ON(session->s_nr_caps > 0);
+	cleanup_cap_releases(session);
+}
+
+/*
+ * wake up any threads waiting on this session's caps.  if the cap is
+ * old (didn't get renewed on the client reconnect), remove it now.
+ *
+ * caller must hold s_mutex.
+ */
+static int wake_up_session_cb(struct inode *inode, struct ceph_cap *cap,
+			      void *arg)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+
+	wake_up(&ci->i_cap_wq);
+	if (arg) {
+		spin_lock(&inode->i_lock);
+		ci->i_wanted_max_size = 0;
+		ci->i_requested_max_size = 0;
+		spin_unlock(&inode->i_lock);
+	}
+	return 0;
+}
+
+static void wake_up_session_caps(struct ceph_mds_session *session,
+				 int reconnect)
+{
+	dout("wake_up_session_caps %p mds%d\n", session, session->s_mds);
+	iterate_session_caps(session, wake_up_session_cb,
+			     (void *)(unsigned long)reconnect);
+}
+
+/*
+ * Send periodic message to MDS renewing all currently held caps.  The
+ * ack will reset the expiration for all caps from this session.
+ *
+ * caller holds s_mutex
+ */
+static int send_renew_caps(struct ceph_mds_client *mdsc,
+			   struct ceph_mds_session *session)
+{
+	struct ceph_msg *msg;
+	int state;
+
+	if (time_after_eq(jiffies, session->s_cap_ttl) &&
+	    time_after_eq(session->s_cap_ttl, session->s_renew_requested))
+		pr_info("mds%d caps stale\n", session->s_mds);
+
+	/* do not try to renew caps until a recovering mds has reconnected
+	 * with its clients. */
+	state = ceph_mdsmap_get_state(mdsc->mdsmap, session->s_mds);
+	if (state < CEPH_MDS_STATE_RECONNECT) {
+		dout("send_renew_caps ignoring mds%d (%s)\n",
+		     session->s_mds, ceph_mds_state_name(state));
+		return 0;
+	}
+
+	dout("send_renew_caps to mds%d (%s)\n", session->s_mds,
+		ceph_mds_state_name(state));
+	session->s_renew_requested = jiffies;
+	msg = create_session_msg(CEPH_SESSION_REQUEST_RENEWCAPS,
+				 ++session->s_renew_seq);
+	if (IS_ERR(msg))
+		return PTR_ERR(msg);
+	ceph_con_send(&session->s_con, msg);
+	return 0;
+}
+
+/*
+ * Note new cap ttl, and any transition from stale -> not stale (fresh?).
+ *
+ * Called under session->s_mutex
+ */
+static void renewed_caps(struct ceph_mds_client *mdsc,
+			 struct ceph_mds_session *session, int is_renew)
+{
+	int was_stale;
+	int wake = 0;
+
+	spin_lock(&session->s_cap_lock);
+	was_stale = is_renew && (session->s_cap_ttl == 0 ||
+				 time_after_eq(jiffies, session->s_cap_ttl));
+
+	session->s_cap_ttl = session->s_renew_requested +
+		mdsc->mdsmap->m_session_timeout*HZ;
+
+	if (was_stale) {
+		if (time_before(jiffies, session->s_cap_ttl)) {
+			pr_info("mds%d caps renewed\n", session->s_mds);
+			wake = 1;
+		} else {
+			pr_info("mds%d caps still stale\n", session->s_mds);
+		}
+	}
+	dout("renewed_caps mds%d ttl now %lu, was %s, now %s\n",
+	     session->s_mds, session->s_cap_ttl, was_stale ? "stale" : "fresh",
+	     time_before(jiffies, session->s_cap_ttl) ? "stale" : "fresh");
+	spin_unlock(&session->s_cap_lock);
+
+	if (wake)
+		wake_up_session_caps(session, 0);
+}
+
+/*
+ * send a session close request
+ */
+static int request_close_session(struct ceph_mds_client *mdsc,
+				 struct ceph_mds_session *session)
+{
+	struct ceph_msg *msg;
+	int err = 0;
+
+	dout("request_close_session mds%d state %s seq %lld\n",
+	     session->s_mds, session_state_name(session->s_state),
+	     session->s_seq);
+	msg = create_session_msg(CEPH_SESSION_REQUEST_CLOSE, session->s_seq);
+	if (IS_ERR(msg))
+		err = PTR_ERR(msg);
+	else
+		ceph_con_send(&session->s_con, msg);
+	return err;
+}
+
+/*
+ * Called with s_mutex held.
+ */
+static int __close_session(struct ceph_mds_client *mdsc,
+			 struct ceph_mds_session *session)
+{
+	if (session->s_state >= CEPH_MDS_SESSION_CLOSING)
+		return 0;
+	session->s_state = CEPH_MDS_SESSION_CLOSING;
+	return request_close_session(mdsc, session);
+}
+
+/*
+ * Trim old(er) caps.
+ *
+ * Because we can't cache an inode without one or more caps, we do
+ * this indirectly: if a cap is unused, we prune its aliases, at which
+ * point the inode will hopefully get dropped to.
+ *
+ * Yes, this is a bit sloppy.  Our only real goal here is to respond to
+ * memory pressure from the MDS, though, so it needn't be perfect.
+ */
+static int trim_caps_cb(struct inode *inode, struct ceph_cap *cap, void *arg)
+{
+	struct ceph_mds_session *session = arg;
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	int used, oissued, mine;
+
+	if (session->s_trim_caps <= 0)
+		return -1;
+
+	spin_lock(&inode->i_lock);
+	mine = cap->issued | cap->implemented;
+	used = __ceph_caps_used(ci);
+	oissued = __ceph_caps_issued_other(ci, cap);
+
+	dout("trim_caps_cb %p cap %p mine %s oissued %s used %s\n",
+	     inode, cap, ceph_cap_string(mine), ceph_cap_string(oissued),
+	     ceph_cap_string(used));
+	if (ci->i_dirty_caps)
+		goto out;   /* dirty caps */
+	if ((used & ~oissued) & mine)
+		goto out;   /* we need these caps */
+
+	session->s_trim_caps--;
+	if (oissued) {
+		/* we aren't the only cap.. just remove us */
+		__ceph_remove_cap(cap);
+	} else {
+		/* try to drop referring dentries */
+		spin_unlock(&inode->i_lock);
+		d_prune_aliases(inode);
+		dout("trim_caps_cb %p cap %p  pruned, count now %d\n",
+		     inode, cap, atomic_read(&inode->i_count));
+		return 0;
+	}
+
+out:
+	spin_unlock(&inode->i_lock);
+	return 0;
+}
+
+/*
+ * Trim session cap count down to some max number.
+ */
+static int trim_caps(struct ceph_mds_client *mdsc,
+		     struct ceph_mds_session *session,
+		     int max_caps)
+{
+	int trim_caps = session->s_nr_caps - max_caps;
+
+	dout("trim_caps mds%d start: %d / %d, trim %d\n",
+	     session->s_mds, session->s_nr_caps, max_caps, trim_caps);
+	if (trim_caps > 0) {
+		session->s_trim_caps = trim_caps;
+		iterate_session_caps(session, trim_caps_cb, session);
+		dout("trim_caps mds%d done: %d / %d, trimmed %d\n",
+		     session->s_mds, session->s_nr_caps, max_caps,
+			trim_caps - session->s_trim_caps);
+		session->s_trim_caps = 0;
+	}
+	return 0;
+}
+
+/*
+ * Allocate cap_release messages.  If there is a partially full message
+ * in the queue, try to allocate enough to cover it's remainder, so that
+ * we can send it immediately.
+ *
+ * Called under s_mutex.
+ */
+static int add_cap_releases(struct ceph_mds_client *mdsc,
+			    struct ceph_mds_session *session,
+			    int extra)
+{
+	struct ceph_msg *msg;
+	struct ceph_mds_cap_release *head;
+	int err = -ENOMEM;
+
+	if (extra < 0)
+		extra = mdsc->client->mount_args->cap_release_safety;
+
+	spin_lock(&session->s_cap_lock);
+
+	if (!list_empty(&session->s_cap_releases)) {
+		msg = list_first_entry(&session->s_cap_releases,
+				       struct ceph_msg,
+				 list_head);
+		head = msg->front.iov_base;
+		extra += CEPH_CAPS_PER_RELEASE - le32_to_cpu(head->num);
+	}
+
+	while (session->s_num_cap_releases < session->s_nr_caps + extra) {
+		spin_unlock(&session->s_cap_lock);
+		msg = ceph_msg_new(CEPH_MSG_CLIENT_CAPRELEASE, PAGE_CACHE_SIZE,
+				   0, 0, NULL);
+		if (!msg)
+			goto out_unlocked;
+		dout("add_cap_releases %p msg %p now %d\n", session, msg,
+		     (int)msg->front.iov_len);
+		head = msg->front.iov_base;
+		head->num = cpu_to_le32(0);
+		msg->front.iov_len = sizeof(*head);
+		spin_lock(&session->s_cap_lock);
+		list_add(&msg->list_head, &session->s_cap_releases);
+		session->s_num_cap_releases += CEPH_CAPS_PER_RELEASE;
+	}
+
+	if (!list_empty(&session->s_cap_releases)) {
+		msg = list_first_entry(&session->s_cap_releases,
+				       struct ceph_msg,
+				       list_head);
+		head = msg->front.iov_base;
+		if (head->num) {
+			dout(" queueing non-full %p (%d)\n", msg,
+			     le32_to_cpu(head->num));
+			list_move_tail(&msg->list_head,
+				      &session->s_cap_releases_done);
+			session->s_num_cap_releases -=
+				CEPH_CAPS_PER_RELEASE - le32_to_cpu(head->num);
+		}
+	}
+	err = 0;
+	spin_unlock(&session->s_cap_lock);
+out_unlocked:
+	return err;
+}
+
+/*
+ * flush all dirty inode data to disk.
+ *
+ * returns true if we've flushed through want_flush_seq
+ */
+static int check_cap_flush(struct ceph_mds_client *mdsc, u64 want_flush_seq)
+{
+	int mds, ret = 1;
+
+	dout("check_cap_flush want %lld\n", want_flush_seq);
+	mutex_lock(&mdsc->mutex);
+	for (mds = 0; ret && mds < mdsc->max_sessions; mds++) {
+		struct ceph_mds_session *session = mdsc->sessions[mds];
+
+		if (!session)
+			continue;
+		get_session(session);
+		mutex_unlock(&mdsc->mutex);
+
+		mutex_lock(&session->s_mutex);
+		if (!list_empty(&session->s_cap_flushing)) {
+			struct ceph_inode_info *ci =
+				list_entry(session->s_cap_flushing.next,
+					   struct ceph_inode_info,
+					   i_flushing_item);
+			struct inode *inode = &ci->vfs_inode;
+
+			spin_lock(&inode->i_lock);
+			if (ci->i_cap_flush_seq <= want_flush_seq) {
+				dout("check_cap_flush still flushing %p "
+				     "seq %lld <= %lld to mds%d\n", inode,
+				     ci->i_cap_flush_seq, want_flush_seq,
+				     session->s_mds);
+				ret = 0;
+			}
+			spin_unlock(&inode->i_lock);
+		}
+		mutex_unlock(&session->s_mutex);
+		ceph_put_mds_session(session);
+
+		if (!ret)
+			return ret;
+		mutex_lock(&mdsc->mutex);
+	}
+
+	mutex_unlock(&mdsc->mutex);
+	dout("check_cap_flush ok, flushed thru %lld\n", want_flush_seq);
+	return ret;
+}
+
+/*
+ * called under s_mutex
+ */
+static void send_cap_releases(struct ceph_mds_client *mdsc,
+		       struct ceph_mds_session *session)
+{
+	struct ceph_msg *msg;
+
+	dout("send_cap_releases mds%d\n", session->s_mds);
+	while (1) {
+		spin_lock(&session->s_cap_lock);
+		if (list_empty(&session->s_cap_releases_done))
+			break;
+		msg = list_first_entry(&session->s_cap_releases_done,
+				 struct ceph_msg, list_head);
+		list_del_init(&msg->list_head);
+		spin_unlock(&session->s_cap_lock);
+		msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);
+		dout("send_cap_releases mds%d %p\n", session->s_mds, msg);
+		ceph_con_send(&session->s_con, msg);
+	}
+	spin_unlock(&session->s_cap_lock);
+}
+
+/*
+ * requests
+ */
+
+/*
+ * Create an mds request.
+ */
+struct ceph_mds_request *
+ceph_mdsc_create_request(struct ceph_mds_client *mdsc, int op, int mode)
+{
+	struct ceph_mds_request *req = kzalloc(sizeof(*req), GFP_NOFS);
+
+	if (!req)
+		return ERR_PTR(-ENOMEM);
+
+	req->r_started = jiffies;
+	req->r_resend_mds = -1;
+	INIT_LIST_HEAD(&req->r_unsafe_dir_item);
+	req->r_fmode = -1;
+	kref_init(&req->r_kref);
+	INIT_LIST_HEAD(&req->r_wait);
+	init_completion(&req->r_completion);
+	init_completion(&req->r_safe_completion);
+	INIT_LIST_HEAD(&req->r_unsafe_item);
+
+	req->r_op = op;
+	req->r_direct_mode = mode;
+	return req;
+}
+
+/*
+ * return oldest (lowest) request, tid in request tree, 0 if none.
+ *
+ * called under mdsc->mutex.
+ */
+static struct ceph_mds_request *__get_oldest_req(struct ceph_mds_client *mdsc)
+{
+	if (RB_EMPTY_ROOT(&mdsc->request_tree))
+		return NULL;
+	return rb_entry(rb_first(&mdsc->request_tree),
+			struct ceph_mds_request, r_node);
+}
+
+static u64 __get_oldest_tid(struct ceph_mds_client *mdsc)
+{
+	struct ceph_mds_request *req = __get_oldest_req(mdsc);
+
+	if (req)
+		return req->r_tid;
+	return 0;
+}
+
+/*
+ * Build a dentry's path.  Allocate on heap; caller must kfree.  Based
+ * on build_path_from_dentry in fs/cifs/dir.c.
+ *
+ * If @stop_on_nosnap, generate path relative to the first non-snapped
+ * inode.
+ *
+ * Encode hidden .snap dirs as a double /, i.e.
+ *   foo/.snap/bar -> foo//bar
+ */
+char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *base,
+			   int stop_on_nosnap)
+{
+	struct dentry *temp;
+	char *path;
+	int len, pos;
+
+	if (dentry == NULL)
+		return ERR_PTR(-EINVAL);
+
+retry:
+	len = 0;
+	for (temp = dentry; !IS_ROOT(temp);) {
+		struct inode *inode = temp->d_inode;
+		if (inode && ceph_snap(inode) == CEPH_SNAPDIR)
+			len++;  /* slash only */
+		else if (stop_on_nosnap && inode &&
+			 ceph_snap(inode) == CEPH_NOSNAP)
+			break;
+		else
+			len += 1 + temp->d_name.len;
+		temp = temp->d_parent;
+		if (temp == NULL) {
+			pr_err("build_path_dentry corrupt dentry %p\n", dentry);
+			return ERR_PTR(-EINVAL);
+		}
+	}
+	if (len)
+		len--;  /* no leading '/' */
+
+	path = kmalloc(len+1, GFP_NOFS);
+	if (path == NULL)
+		return ERR_PTR(-ENOMEM);
+	pos = len;
+	path[pos] = 0;	/* trailing null */
+	for (temp = dentry; !IS_ROOT(temp) && pos != 0; ) {
+		struct inode *inode = temp->d_inode;
+
+		if (inode && ceph_snap(inode) == CEPH_SNAPDIR) {
+			dout("build_path_dentry path+%d: %p SNAPDIR\n",
+			     pos, temp);
+		} else if (stop_on_nosnap && inode &&
+			   ceph_snap(inode) == CEPH_NOSNAP) {
+			break;
+		} else {
+			pos -= temp->d_name.len;
+			if (pos < 0)
+				break;
+			strncpy(path + pos, temp->d_name.name,
+				temp->d_name.len);
+			dout("build_path_dentry path+%d: %p '%.*s'\n",
+			     pos, temp, temp->d_name.len, path + pos);
+		}
+		if (pos)
+			path[--pos] = '/';
+		temp = temp->d_parent;
+		if (temp == NULL) {
+			pr_err("build_path_dentry corrupt dentry\n");
+			kfree(path);
+			return ERR_PTR(-EINVAL);
+		}
+	}
+	if (pos != 0) {
+		pr_err("build_path_dentry did not end path lookup where "
+		       "expected, namelen is %d, pos is %d\n", len, pos);
+		/* presumably this is only possible if racing with a
+		   rename of one of the parent directories (we can not
+		   lock the dentries above us to prevent this, but
+		   retrying should be harmless) */
+		kfree(path);
+		goto retry;
+	}
+
+	*base = ceph_ino(temp->d_inode);
+	*plen = len;
+	dout("build_path_dentry on %p %d built %llx '%.*s'\n",
+	     dentry, atomic_read(&dentry->d_count), *base, len, path);
+	return path;
+}
+
+static int build_dentry_path(struct dentry *dentry,
+			     const char **ppath, int *ppathlen, u64 *pino,
+			     int *pfreepath)
+{
+	char *path;
+
+	if (ceph_snap(dentry->d_parent->d_inode) == CEPH_NOSNAP) {
+		*pino = ceph_ino(dentry->d_parent->d_inode);
+		*ppath = dentry->d_name.name;
+		*ppathlen = dentry->d_name.len;
+		return 0;
+	}
+	path = ceph_mdsc_build_path(dentry, ppathlen, pino, 1);
+	if (IS_ERR(path))
+		return PTR_ERR(path);
+	*ppath = path;
+	*pfreepath = 1;
+	return 0;
+}
+
+static int build_inode_path(struct inode *inode,
+			    const char **ppath, int *ppathlen, u64 *pino,
+			    int *pfreepath)
+{
+	struct dentry *dentry;
+	char *path;
+
+	if (ceph_snap(inode) == CEPH_NOSNAP) {
+		*pino = ceph_ino(inode);
+		*ppathlen = 0;
+		return 0;
+	}
+	dentry = d_find_alias(inode);
+	path = ceph_mdsc_build_path(dentry, ppathlen, pino, 1);
+	dput(dentry);
+	if (IS_ERR(path))
+		return PTR_ERR(path);
+	*ppath = path;
+	*pfreepath = 1;
+	return 0;
+}
+
+/*
+ * request arguments may be specified via an inode *, a dentry *, or
+ * an explicit ino+path.
+ */
+static int set_request_path_attr(struct inode *rinode, struct dentry *rdentry,
+				  const char *rpath, u64 rino,
+				  const char **ppath, int *pathlen,
+				  u64 *ino, int *freepath)
+{
+	int r = 0;
+
+	if (rinode) {
+		r = build_inode_path(rinode, ppath, pathlen, ino, freepath);
+		dout(" inode %p %llx.%llx\n", rinode, ceph_ino(rinode),
+		     ceph_snap(rinode));
+	} else if (rdentry) {
+		r = build_dentry_path(rdentry, ppath, pathlen, ino, freepath);
+		dout(" dentry %p %llx/%.*s\n", rdentry, *ino, *pathlen,
+		     *ppath);
+	} else if (rpath) {
+		*ino = rino;
+		*ppath = rpath;
+		*pathlen = strlen(rpath);
+		dout(" path %.*s\n", *pathlen, rpath);
+	}
+
+	return r;
+}
+
+/*
+ * called under mdsc->mutex
+ */
+static struct ceph_msg *create_request_message(struct ceph_mds_client *mdsc,
+					       struct ceph_mds_request *req,
+					       int mds)
+{
+	struct ceph_msg *msg;
+	struct ceph_mds_request_head *head;
+	const char *path1 = NULL;
+	const char *path2 = NULL;
+	u64 ino1 = 0, ino2 = 0;
+	int pathlen1 = 0, pathlen2 = 0;
+	int freepath1 = 0, freepath2 = 0;
+	int len;
+	u16 releases;
+	void *p, *end;
+	int ret;
+
+	ret = set_request_path_attr(req->r_inode, req->r_dentry,
+			      req->r_path1, req->r_ino1.ino,
+			      &path1, &pathlen1, &ino1, &freepath1);
+	if (ret < 0) {
+		msg = ERR_PTR(ret);
+		goto out;
+	}
+
+	ret = set_request_path_attr(NULL, req->r_old_dentry,
+			      req->r_path2, req->r_ino2.ino,
+			      &path2, &pathlen2, &ino2, &freepath2);
+	if (ret < 0) {
+		msg = ERR_PTR(ret);
+		goto out_free1;
+	}
+
+	len = sizeof(*head) +
+		pathlen1 + pathlen2 + 2*(1 + sizeof(u32) + sizeof(u64));
+
+	/* calculate (max) length for cap releases */
+	len += sizeof(struct ceph_mds_request_release) *
+		(!!req->r_inode_drop + !!req->r_dentry_drop +
+		 !!req->r_old_inode_drop + !!req->r_old_dentry_drop);
+	if (req->r_dentry_drop)
+		len += req->r_dentry->d_name.len;
+	if (req->r_old_dentry_drop)
+		len += req->r_old_dentry->d_name.len;
+
+	msg = ceph_msg_new(CEPH_MSG_CLIENT_REQUEST, len, 0, 0, NULL);
+	if (IS_ERR(msg))
+		goto out_free2;
+
+	msg->hdr.tid = cpu_to_le64(req->r_tid);
+
+	head = msg->front.iov_base;
+	p = msg->front.iov_base + sizeof(*head);
+	end = msg->front.iov_base + msg->front.iov_len;
+
+	head->mdsmap_epoch = cpu_to_le32(mdsc->mdsmap->m_epoch);
+	head->op = cpu_to_le32(req->r_op);
+	head->caller_uid = cpu_to_le32(current_fsuid());
+	head->caller_gid = cpu_to_le32(current_fsgid());
+	head->args = req->r_args;
+
+	ceph_encode_filepath(&p, end, ino1, path1);
+	ceph_encode_filepath(&p, end, ino2, path2);
+
+	/* cap releases */
+	releases = 0;
+	if (req->r_inode_drop)
+		releases += ceph_encode_inode_release(&p,
+		      req->r_inode ? req->r_inode : req->r_dentry->d_inode,
+		      mds, req->r_inode_drop, req->r_inode_unless, 0);
+	if (req->r_dentry_drop)
+		releases += ceph_encode_dentry_release(&p, req->r_dentry,
+		       mds, req->r_dentry_drop, req->r_dentry_unless);
+	if (req->r_old_dentry_drop)
+		releases += ceph_encode_dentry_release(&p, req->r_old_dentry,
+		       mds, req->r_old_dentry_drop, req->r_old_dentry_unless);
+	if (req->r_old_inode_drop)
+		releases += ceph_encode_inode_release(&p,
+		      req->r_old_dentry->d_inode,
+		      mds, req->r_old_inode_drop, req->r_old_inode_unless, 0);
+	head->num_releases = cpu_to_le16(releases);
+
+	BUG_ON(p > end);
+	msg->front.iov_len = p - msg->front.iov_base;
+	msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);
+
+	msg->pages = req->r_pages;
+	msg->nr_pages = req->r_num_pages;
+	msg->hdr.data_len = cpu_to_le32(req->r_data_len);
+	msg->hdr.data_off = cpu_to_le16(0);
+
+out_free2:
+	if (freepath2)
+		kfree((char *)path2);
+out_free1:
+	if (freepath1)
+		kfree((char *)path1);
+out:
+	return msg;
+}
+
+/*
+ * called under mdsc->mutex if error, under no mutex if
+ * success.
+ */
+static void complete_request(struct ceph_mds_client *mdsc,
+			     struct ceph_mds_request *req)
+{
+	if (req->r_callback)
+		req->r_callback(mdsc, req);
+	else
+		complete(&req->r_completion);
+}
+
+/*
+ * called under mdsc->mutex
+ */
+static int __prepare_send_request(struct ceph_mds_client *mdsc,
+				  struct ceph_mds_request *req,
+				  int mds)
+{
+	struct ceph_mds_request_head *rhead;
+	struct ceph_msg *msg;
+	int flags = 0;
+
+	req->r_mds = mds;
+	req->r_attempts++;
+	dout("prepare_send_request %p tid %lld %s (attempt %d)\n", req,
+	     req->r_tid, ceph_mds_op_name(req->r_op), req->r_attempts);
+
+	if (req->r_request) {
+		ceph_msg_put(req->r_request);
+		req->r_request = NULL;
+	}
+	msg = create_request_message(mdsc, req, mds);
+	if (IS_ERR(msg)) {
+		req->r_reply = ERR_PTR(PTR_ERR(msg));
+		complete_request(mdsc, req);
+		return -PTR_ERR(msg);
+	}
+	req->r_request = msg;
+
+	rhead = msg->front.iov_base;
+	rhead->oldest_client_tid = cpu_to_le64(__get_oldest_tid(mdsc));
+	if (req->r_got_unsafe)
+		flags |= CEPH_MDS_FLAG_REPLAY;
+	if (req->r_locked_dir)
+		flags |= CEPH_MDS_FLAG_WANT_DENTRY;
+	rhead->flags = cpu_to_le32(flags);
+	rhead->num_fwd = req->r_num_fwd;
+	rhead->num_retry = req->r_attempts - 1;
+
+	dout(" r_locked_dir = %p\n", req->r_locked_dir);
+
+	if (req->r_target_inode && req->r_got_unsafe)
+		rhead->ino = cpu_to_le64(ceph_ino(req->r_target_inode));
+	else
+		rhead->ino = 0;
+	return 0;
+}
+
+/*
+ * send request, or put it on the appropriate wait list.
+ */
+static int __do_request(struct ceph_mds_client *mdsc,
+			struct ceph_mds_request *req)
+{
+	struct ceph_mds_session *session = NULL;
+	int mds = -1;
+	int err = -EAGAIN;
+
+	if (req->r_reply)
+		goto out;
+
+	if (req->r_timeout &&
+	    time_after_eq(jiffies, req->r_started + req->r_timeout)) {
+		dout("do_request timed out\n");
+		err = -EIO;
+		goto finish;
+	}
+
+	mds = __choose_mds(mdsc, req);
+	if (mds < 0 ||
+	    ceph_mdsmap_get_state(mdsc->mdsmap, mds) < CEPH_MDS_STATE_ACTIVE) {
+		dout("do_request no mds or not active, waiting for map\n");
+		list_add(&req->r_wait, &mdsc->waiting_for_map);
+		goto out;
+	}
+
+	/* get, open session */
+	session = __ceph_lookup_mds_session(mdsc, mds);
+	if (!session)
+		session = register_session(mdsc, mds);
+	dout("do_request mds%d session %p state %s\n", mds, session,
+	     session_state_name(session->s_state));
+	if (session->s_state != CEPH_MDS_SESSION_OPEN &&
+	    session->s_state != CEPH_MDS_SESSION_HUNG) {
+		if (session->s_state == CEPH_MDS_SESSION_NEW ||
+		    session->s_state == CEPH_MDS_SESSION_CLOSING)
+			__open_session(mdsc, session);
+		list_add(&req->r_wait, &session->s_waiting);
+		goto out_session;
+	}
+
+	/* send request */
+	req->r_session = get_session(session);
+	req->r_resend_mds = -1;   /* forget any previous mds hint */
+
+	if (req->r_request_started == 0)   /* note request start time */
+		req->r_request_started = jiffies;
+
+	err = __prepare_send_request(mdsc, req, mds);
+	if (!err) {
+		ceph_msg_get(req->r_request);
+		ceph_con_send(&session->s_con, req->r_request);
+	}
+
+out_session:
+	ceph_put_mds_session(session);
+out:
+	return err;
+
+finish:
+	req->r_reply = ERR_PTR(err);
+	complete_request(mdsc, req);
+	goto out;
+}
+
+/*
+ * called under mdsc->mutex
+ */
+static void __wake_requests(struct ceph_mds_client *mdsc,
+			    struct list_head *head)
+{
+	struct ceph_mds_request *req, *nreq;
+
+	list_for_each_entry_safe(req, nreq, head, r_wait) {
+		list_del_init(&req->r_wait);
+		__do_request(mdsc, req);
+	}
+}
+
+/*
+ * Wake up threads with requests pending for @mds, so that they can
+ * resubmit their requests to a possibly different mds.  If @all is set,
+ * wake up if their requests has been forwarded to @mds, too.
+ */
+static void kick_requests(struct ceph_mds_client *mdsc, int mds, int all)
+{
+	struct ceph_mds_request *req;
+	struct rb_node *p;
+
+	dout("kick_requests mds%d\n", mds);
+	for (p = rb_first(&mdsc->request_tree); p; p = rb_next(p)) {
+		req = rb_entry(p, struct ceph_mds_request, r_node);
+		if (req->r_got_unsafe)
+			continue;
+		if (req->r_session &&
+		    req->r_session->s_mds == mds) {
+			dout(" kicking tid %llu\n", req->r_tid);
+			put_request_session(req);
+			__do_request(mdsc, req);
+		}
+	}
+}
+
+void ceph_mdsc_submit_request(struct ceph_mds_client *mdsc,
+			      struct ceph_mds_request *req)
+{
+	dout("submit_request on %p\n", req);
+	mutex_lock(&mdsc->mutex);
+	__register_request(mdsc, req, NULL);
+	__do_request(mdsc, req);
+	mutex_unlock(&mdsc->mutex);
+}
+
+/*
+ * Synchrously perform an mds request.  Take care of all of the
+ * session setup, forwarding, retry details.
+ */
+int ceph_mdsc_do_request(struct ceph_mds_client *mdsc,
+			 struct inode *dir,
+			 struct ceph_mds_request *req)
+{
+	int err;
+
+	dout("do_request on %p\n", req);
+
+	/* take CAP_PIN refs for r_inode, r_locked_dir, r_old_dentry */
+	if (req->r_inode)
+		ceph_get_cap_refs(ceph_inode(req->r_inode), CEPH_CAP_PIN);
+	if (req->r_locked_dir)
+		ceph_get_cap_refs(ceph_inode(req->r_locked_dir), CEPH_CAP_PIN);
+	if (req->r_old_dentry)
+		ceph_get_cap_refs(
+			ceph_inode(req->r_old_dentry->d_parent->d_inode),
+			CEPH_CAP_PIN);
+
+	/* issue */
+	mutex_lock(&mdsc->mutex);
+	__register_request(mdsc, req, dir);
+	__do_request(mdsc, req);
+
+	/* wait */
+	if (!req->r_reply) {
+		mutex_unlock(&mdsc->mutex);
+		if (req->r_timeout) {
+			err = (long)wait_for_completion_interruptible_timeout(
+				&req->r_completion, req->r_timeout);
+			if (err == 0)
+				req->r_reply = ERR_PTR(-EIO);
+			else if (err < 0)
+				req->r_reply = ERR_PTR(err);
+		} else {
+                        err = wait_for_completion_interruptible(
+                                &req->r_completion);
+                        if (err)
+                                req->r_reply = ERR_PTR(err);
+		}
+		mutex_lock(&mdsc->mutex);
+	}
+
+	if (IS_ERR(req->r_reply)) {
+		err = PTR_ERR(req->r_reply);
+		req->r_reply = NULL;
+
+		if (err == -ERESTARTSYS) {
+			/* aborted */
+			req->r_aborted = true;
+
+			if (req->r_locked_dir &&
+			    (req->r_op & CEPH_MDS_OP_WRITE)) {
+				struct ceph_inode_info *ci =
+					ceph_inode(req->r_locked_dir);
+
+				dout("aborted, clearing I_COMPLETE on %p\n", 
+				     req->r_locked_dir);
+				spin_lock(&req->r_locked_dir->i_lock);
+				ci->i_ceph_flags &= ~CEPH_I_COMPLETE;
+				ci->i_release_count++;
+				spin_unlock(&req->r_locked_dir->i_lock);
+			}
+		} else {
+			/* clean up this request */
+			__unregister_request(mdsc, req);
+			if (!list_empty(&req->r_unsafe_item))
+				list_del_init(&req->r_unsafe_item);
+			complete(&req->r_safe_completion);
+		}
+	} else if (req->r_err) {
+		err = req->r_err;
+	} else {
+		err = le32_to_cpu(req->r_reply_info.head->result);
+	}
+	mutex_unlock(&mdsc->mutex);
+
+	dout("do_request %p done, result %d\n", req, err);
+	return err;
+}
+
+/*
+ * Handle mds reply.
+ *
+ * We take the session mutex and parse and process the reply immediately.
+ * This preserves the logical ordering of replies, capabilities, etc., sent
+ * by the MDS as they are applied to our local cache.
+ */
+static void handle_reply(struct ceph_mds_session *session, struct ceph_msg *msg)
+{
+	struct ceph_mds_client *mdsc = session->s_mdsc;
+	struct ceph_mds_request *req;
+	struct ceph_mds_reply_head *head = msg->front.iov_base;
+	struct ceph_mds_reply_info_parsed *rinfo;  /* parsed reply info */
+	u64 tid;
+	int err, result;
+	int mds = session->s_mds;
+
+	if (msg->front.iov_len < sizeof(*head)) {
+		pr_err("mdsc_handle_reply got corrupt (short) reply\n");
+		ceph_msg_dump(msg);
+		return;
+	}
+
+	/* get request, session */
+	tid = le64_to_cpu(msg->hdr.tid);
+	mutex_lock(&mdsc->mutex);
+	req = __lookup_request(mdsc, tid);
+	if (!req) {
+		dout("handle_reply on unknown tid %llu\n", tid);
+		mutex_unlock(&mdsc->mutex);
+		return;
+	}
+	dout("handle_reply %p\n", req);
+
+	/* correct session? */
+	if (!req->r_session && req->r_session != session) {
+		pr_err("mdsc_handle_reply got %llu on session mds%d"
+		       " not mds%d\n", tid, session->s_mds,
+		       req->r_session ? req->r_session->s_mds : -1);
+		mutex_unlock(&mdsc->mutex);
+		goto out;
+	}
+
+	/* dup? */
+	if ((req->r_got_unsafe && !head->safe) ||
+	    (req->r_got_safe && head->safe)) {
+		pr_warning("got a dup %s reply on %llu from mds%d\n",
+			   head->safe ? "safe" : "unsafe", tid, mds);
+		mutex_unlock(&mdsc->mutex);
+		goto out;
+	}
+
+	result = le32_to_cpu(head->result);
+
+	/*
+	 * Tolerate 2 consecutive ESTALEs from the same mds.
+	 * FIXME: we should be looking at the cap migrate_seq.
+	 */
+	if (result == -ESTALE) {
+		req->r_direct_mode = USE_AUTH_MDS;
+		req->r_num_stale++;
+		if (req->r_num_stale <= 2) {
+			__do_request(mdsc, req);
+			mutex_unlock(&mdsc->mutex);
+			goto out;
+		}
+	} else {
+		req->r_num_stale = 0;
+	}
+
+	if (head->safe) {
+		req->r_got_safe = true;
+		__unregister_request(mdsc, req);
+		complete(&req->r_safe_completion);
+
+		if (req->r_got_unsafe) {
+			/*
+			 * We already handled the unsafe response, now do the
+			 * cleanup.  No need to examine the response; the MDS
+			 * doesn't include any result info in the safe
+			 * response.  And even if it did, there is nothing
+			 * useful we could do with a revised return value.
+			 */
+			dout("got safe reply %llu, mds%d\n", tid, mds);
+			list_del_init(&req->r_unsafe_item);
+
+			/* last unsafe request during umount? */
+			if (mdsc->stopping && !__get_oldest_req(mdsc))
+				complete(&mdsc->safe_umount_waiters);
+			mutex_unlock(&mdsc->mutex);
+			goto out;
+		}
+	}
+
+	BUG_ON(req->r_reply);
+
+	if (!head->safe) {
+		req->r_got_unsafe = true;
+		list_add_tail(&req->r_unsafe_item, &req->r_session->s_unsafe);
+	}
+
+	dout("handle_reply tid %lld result %d\n", tid, result);
+	rinfo = &req->r_reply_info;
+	err = parse_reply_info(msg, rinfo);
+	mutex_unlock(&mdsc->mutex);
+
+	mutex_lock(&session->s_mutex);
+	if (err < 0) {
+		pr_err("mdsc_handle_reply got corrupt reply mds%d\n", mds);
+		ceph_msg_dump(msg);
+		goto out_err;
+	}
+
+	/* snap trace */
+	if (rinfo->snapblob_len) {
+		down_write(&mdsc->snap_rwsem);
+		ceph_update_snap_trace(mdsc, rinfo->snapblob,
+			       rinfo->snapblob + rinfo->snapblob_len,
+			       le32_to_cpu(head->op) == CEPH_MDS_OP_RMSNAP);
+		downgrade_write(&mdsc->snap_rwsem);
+	} else {
+		down_read(&mdsc->snap_rwsem);
+	}
+
+	/* insert trace into our cache */
+	err = ceph_fill_trace(mdsc->client->sb, req, req->r_session);
+	if (err == 0) {
+		if (result == 0 && rinfo->dir_nr)
+			ceph_readdir_prepopulate(req, req->r_session);
+		ceph_unreserve_caps(&req->r_caps_reservation);
+	}
+
+	up_read(&mdsc->snap_rwsem);
+out_err:
+	if (err) {
+		req->r_err = err;
+	} else {
+		req->r_reply = msg;
+		ceph_msg_get(msg);
+	}
+
+	add_cap_releases(mdsc, req->r_session, -1);
+	mutex_unlock(&session->s_mutex);
+
+	/* kick calling process */
+	complete_request(mdsc, req);
+out:
+	ceph_mdsc_put_request(req);
+	return;
+}
+
+
+
+/*
+ * handle mds notification that our request has been forwarded.
+ */
+static void handle_forward(struct ceph_mds_client *mdsc,
+			   struct ceph_mds_session *session,
+			   struct ceph_msg *msg)
+{
+	struct ceph_mds_request *req;
+	u64 tid = le64_to_cpu(msg->hdr.tid);
+	u32 next_mds;
+	u32 fwd_seq;
+	int err = -EINVAL;
+	void *p = msg->front.iov_base;
+	void *end = p + msg->front.iov_len;
+
+	ceph_decode_need(&p, end, 2*sizeof(u32), bad);
+	next_mds = ceph_decode_32(&p);
+	fwd_seq = ceph_decode_32(&p);
+
+	mutex_lock(&mdsc->mutex);
+	req = __lookup_request(mdsc, tid);
+	if (!req) {
+		dout("forward %llu to mds%d - req dne\n", tid, next_mds);
+		goto out;  /* dup reply? */
+	}
+
+	if (fwd_seq <= req->r_num_fwd) {
+		dout("forward %llu to mds%d - old seq %d <= %d\n",
+		     tid, next_mds, req->r_num_fwd, fwd_seq);
+	} else {
+		/* resend. forward race not possible; mds would drop */
+		dout("forward %llu to mds%d (we resend)\n", tid, next_mds);
+		req->r_num_fwd = fwd_seq;
+		req->r_resend_mds = next_mds;
+		put_request_session(req);
+		__do_request(mdsc, req);
+	}
+	ceph_mdsc_put_request(req);
+out:
+	mutex_unlock(&mdsc->mutex);
+	return;
+
+bad:
+	pr_err("mdsc_handle_forward decode error err=%d\n", err);
+}
+
+/*
+ * handle a mds session control message
+ */
+static void handle_session(struct ceph_mds_session *session,
+			   struct ceph_msg *msg)
+{
+	struct ceph_mds_client *mdsc = session->s_mdsc;
+	u32 op;
+	u64 seq;
+	int mds = session->s_mds;
+	struct ceph_mds_session_head *h = msg->front.iov_base;
+	int wake = 0;
+
+	/* decode */
+	if (msg->front.iov_len != sizeof(*h))
+		goto bad;
+	op = le32_to_cpu(h->op);
+	seq = le64_to_cpu(h->seq);
+
+	mutex_lock(&mdsc->mutex);
+	if (op == CEPH_SESSION_CLOSE)
+		__unregister_session(mdsc, session);
+	/* FIXME: this ttl calculation is generous */
+	session->s_ttl = jiffies + HZ*mdsc->mdsmap->m_session_autoclose;
+	mutex_unlock(&mdsc->mutex);
+
+	mutex_lock(&session->s_mutex);
+
+	dout("handle_session mds%d %s %p state %s seq %llu\n",
+	     mds, ceph_session_op_name(op), session,
+	     session_state_name(session->s_state), seq);
+
+	if (session->s_state == CEPH_MDS_SESSION_HUNG) {
+		session->s_state = CEPH_MDS_SESSION_OPEN;
+		pr_info("mds%d came back\n", session->s_mds);
+	}
+
+	switch (op) {
+	case CEPH_SESSION_OPEN:
+		session->s_state = CEPH_MDS_SESSION_OPEN;
+		renewed_caps(mdsc, session, 0);
+		wake = 1;
+		if (mdsc->stopping)
+			__close_session(mdsc, session);
+		break;
+
+	case CEPH_SESSION_RENEWCAPS:
+		if (session->s_renew_seq == seq)
+			renewed_caps(mdsc, session, 1);
+		break;
+
+	case CEPH_SESSION_CLOSE:
+		remove_session_caps(session);
+		wake = 1; /* for good measure */
+		complete(&mdsc->session_close_waiters);
+		kick_requests(mdsc, mds, 0);      /* cur only */
+		break;
+
+	case CEPH_SESSION_STALE:
+		pr_info("mds%d caps went stale, renewing\n",
+			session->s_mds);
+		spin_lock(&session->s_cap_lock);
+		session->s_cap_gen++;
+		session->s_cap_ttl = 0;
+		spin_unlock(&session->s_cap_lock);
+		send_renew_caps(mdsc, session);
+		break;
+
+	case CEPH_SESSION_RECALL_STATE:
+		trim_caps(mdsc, session, le32_to_cpu(h->max_caps));
+		break;
+
+	default:
+		pr_err("mdsc_handle_session bad op %d mds%d\n", op, mds);
+		WARN_ON(1);
+	}
+
+	mutex_unlock(&session->s_mutex);
+	if (wake) {
+		mutex_lock(&mdsc->mutex);
+		__wake_requests(mdsc, &session->s_waiting);
+		mutex_unlock(&mdsc->mutex);
+	}
+	return;
+
+bad:
+	pr_err("mdsc_handle_session corrupt message mds%d len %d\n", mds,
+	       (int)msg->front.iov_len);
+	ceph_msg_dump(msg);
+	return;
+}
+
+
+/*
+ * called under session->mutex.
+ */
+static void replay_unsafe_requests(struct ceph_mds_client *mdsc,
+				   struct ceph_mds_session *session)
+{
+	struct ceph_mds_request *req, *nreq;
+	int err;
+
+	dout("replay_unsafe_requests mds%d\n", session->s_mds);
+
+	mutex_lock(&mdsc->mutex);
+	list_for_each_entry_safe(req, nreq, &session->s_unsafe, r_unsafe_item) {
+		err = __prepare_send_request(mdsc, req, session->s_mds);
+		if (!err) {
+			ceph_msg_get(req->r_request);
+			ceph_con_send(&session->s_con, req->r_request);
+		}
+	}
+	mutex_unlock(&mdsc->mutex);
+}
+
+/*
+ * Encode information about a cap for a reconnect with the MDS.
+ */
+static int encode_caps_cb(struct inode *inode, struct ceph_cap *cap,
+			  void *arg)
+{
+	struct ceph_mds_cap_reconnect rec;
+	struct ceph_inode_info *ci;
+	struct ceph_pagelist *pagelist = arg;
+	char *path;
+	int pathlen, err;
+	u64 pathbase;
+	struct dentry *dentry;
+
+	ci = cap->ci;
+
+	dout(" adding %p ino %llx.%llx cap %p %lld %s\n",
+	     inode, ceph_vinop(inode), cap, cap->cap_id,
+	     ceph_cap_string(cap->issued));
+	err = ceph_pagelist_encode_64(pagelist, ceph_ino(inode));
+	if (err)
+		return err;
+
+	dentry = d_find_alias(inode);
+	if (dentry) {
+		path = ceph_mdsc_build_path(dentry, &pathlen, &pathbase, 0);
+		if (IS_ERR(path)) {
+			err = PTR_ERR(path);
+			BUG_ON(err);
+		}
+	} else {
+		path = NULL;
+		pathlen = 0;
+	}
+	err = ceph_pagelist_encode_string(pagelist, path, pathlen);
+	if (err)
+		goto out;
+
+	spin_lock(&inode->i_lock);
+	cap->seq = 0;        /* reset cap seq */
+	cap->issue_seq = 0;  /* and issue_seq */
+	rec.cap_id = cpu_to_le64(cap->cap_id);
+	rec.pathbase = cpu_to_le64(pathbase);
+	rec.wanted = cpu_to_le32(__ceph_caps_wanted(ci));
+	rec.issued = cpu_to_le32(cap->issued);
+	rec.size = cpu_to_le64(inode->i_size);
+	ceph_encode_timespec(&rec.mtime, &inode->i_mtime);
+	ceph_encode_timespec(&rec.atime, &inode->i_atime);
+	rec.snaprealm = cpu_to_le64(ci->i_snap_realm->ino);
+	spin_unlock(&inode->i_lock);
+
+	err = ceph_pagelist_append(pagelist, &rec, sizeof(rec));
+
+out:
+	kfree(path);
+	dput(dentry);
+	return err;
+}
+
+
+/*
+ * If an MDS fails and recovers, clients need to reconnect in order to
+ * reestablish shared state.  This includes all caps issued through
+ * this session _and_ the snap_realm hierarchy.  Because it's not
+ * clear which snap realms the mds cares about, we send everything we
+ * know about.. that ensures we'll then get any new info the
+ * recovering MDS might have.
+ *
+ * This is a relatively heavyweight operation, but it's rare.
+ *
+ * called with mdsc->mutex held.
+ */
+static void send_mds_reconnect(struct ceph_mds_client *mdsc, int mds)
+{
+	struct ceph_mds_session *session = NULL;
+	struct ceph_msg *reply;
+	struct rb_node *p;
+	int err;
+	struct ceph_pagelist *pagelist;
+
+	pr_info("reconnect to recovering mds%d\n", mds);
+
+	pagelist = kmalloc(sizeof(*pagelist), GFP_NOFS);
+	if (!pagelist)
+		goto fail_nopagelist;
+	ceph_pagelist_init(pagelist);
+
+	reply = ceph_msg_new(CEPH_MSG_CLIENT_RECONNECT, 0, 0, 0, NULL);
+	if (IS_ERR(reply)) {
+		err = PTR_ERR(reply);
+		goto fail_nomsg;
+	}
+
+	/* find session */
+	session = __ceph_lookup_mds_session(mdsc, mds);
+	mutex_unlock(&mdsc->mutex);    /* drop lock for duration */
+
+	if (session) {
+		mutex_lock(&session->s_mutex);
+
+		session->s_state = CEPH_MDS_SESSION_RECONNECTING;
+		session->s_seq = 0;
+
+		ceph_con_open(&session->s_con,
+			      ceph_mdsmap_get_addr(mdsc->mdsmap, mds));
+
+		/* replay unsafe requests */
+		replay_unsafe_requests(mdsc, session);
+	} else {
+		dout("no session for mds%d, will send short reconnect\n",
+		     mds);
+	}
+
+	down_read(&mdsc->snap_rwsem);
+
+	if (!session)
+		goto send;
+	dout("session %p state %s\n", session,
+	     session_state_name(session->s_state));
+
+	/* traverse this session's caps */
+	err = ceph_pagelist_encode_32(pagelist, session->s_nr_caps);
+	if (err)
+		goto fail;
+	err = iterate_session_caps(session, encode_caps_cb, pagelist);
+	if (err < 0)
+		goto out;
+
+	/*
+	 * snaprealms.  we provide mds with the ino, seq (version), and
+	 * parent for all of our realms.  If the mds has any newer info,
+	 * it will tell us.
+	 */
+	for (p = rb_first(&mdsc->snap_realms); p; p = rb_next(p)) {
+		struct ceph_snap_realm *realm =
+			rb_entry(p, struct ceph_snap_realm, node);
+		struct ceph_mds_snaprealm_reconnect sr_rec;
+
+		dout(" adding snap realm %llx seq %lld parent %llx\n",
+		     realm->ino, realm->seq, realm->parent_ino);
+		sr_rec.ino = cpu_to_le64(realm->ino);
+		sr_rec.seq = cpu_to_le64(realm->seq);
+		sr_rec.parent = cpu_to_le64(realm->parent_ino);
+		err = ceph_pagelist_append(pagelist, &sr_rec, sizeof(sr_rec));
+		if (err)
+			goto fail;
+	}
+
+send:
+	reply->pagelist = pagelist;
+	reply->hdr.data_len = cpu_to_le32(pagelist->length);
+	reply->nr_pages = calc_pages_for(0, pagelist->length);
+	ceph_con_send(&session->s_con, reply);
+
+	if (session) {
+		session->s_state = CEPH_MDS_SESSION_OPEN;
+		__wake_requests(mdsc, &session->s_waiting);
+	}
+
+out:
+	up_read(&mdsc->snap_rwsem);
+	if (session) {
+		mutex_unlock(&session->s_mutex);
+		ceph_put_mds_session(session);
+	}
+	mutex_lock(&mdsc->mutex);
+	return;
+
+fail:
+	ceph_msg_put(reply);
+fail_nomsg:
+	ceph_pagelist_release(pagelist);
+	kfree(pagelist);
+fail_nopagelist:
+	pr_err("ENOMEM preparing reconnect for mds%d\n", mds);
+	goto out;
+}
+
+
+/*
+ * compare old and new mdsmaps, kicking requests
+ * and closing out old connections as necessary
+ *
+ * called under mdsc->mutex.
+ */
+static void check_new_map(struct ceph_mds_client *mdsc,
+			  struct ceph_mdsmap *newmap,
+			  struct ceph_mdsmap *oldmap)
+{
+	int i;
+	int oldstate, newstate;
+	struct ceph_mds_session *s;
+
+	dout("check_new_map new %u old %u\n",
+	     newmap->m_epoch, oldmap->m_epoch);
+
+	for (i = 0; i < oldmap->m_max_mds && i < mdsc->max_sessions; i++) {
+		if (mdsc->sessions[i] == NULL)
+			continue;
+		s = mdsc->sessions[i];
+		oldstate = ceph_mdsmap_get_state(oldmap, i);
+		newstate = ceph_mdsmap_get_state(newmap, i);
+
+		dout("check_new_map mds%d state %s -> %s (session %s)\n",
+		     i, ceph_mds_state_name(oldstate),
+		     ceph_mds_state_name(newstate),
+		     session_state_name(s->s_state));
+
+		if (memcmp(ceph_mdsmap_get_addr(oldmap, i),
+			   ceph_mdsmap_get_addr(newmap, i),
+			   sizeof(struct ceph_entity_addr))) {
+			if (s->s_state == CEPH_MDS_SESSION_OPENING) {
+				/* the session never opened, just close it
+				 * out now */
+				__wake_requests(mdsc, &s->s_waiting);
+				__unregister_session(mdsc, s);
+			} else {
+				/* just close it */
+				mutex_unlock(&mdsc->mutex);
+				mutex_lock(&s->s_mutex);
+				mutex_lock(&mdsc->mutex);
+				ceph_con_close(&s->s_con);
+				mutex_unlock(&s->s_mutex);
+				s->s_state = CEPH_MDS_SESSION_RESTARTING;
+			}
+
+			/* kick any requests waiting on the recovering mds */
+			kick_requests(mdsc, i, 1);
+		} else if (oldstate == newstate) {
+			continue;  /* nothing new with this mds */
+		}
+
+		/*
+		 * send reconnect?
+		 */
+		if (s->s_state == CEPH_MDS_SESSION_RESTARTING &&
+		    newstate >= CEPH_MDS_STATE_RECONNECT)
+			send_mds_reconnect(mdsc, i);
+
+		/*
+		 * kick requests on any mds that has gone active.
+		 *
+		 * kick requests on cur or forwarder: we may have sent
+		 * the request to mds1, mds1 told us it forwarded it
+		 * to mds2, but then we learn mds1 failed and can't be
+		 * sure it successfully forwarded our request before
+		 * it died.
+		 */
+		if (oldstate < CEPH_MDS_STATE_ACTIVE &&
+		    newstate >= CEPH_MDS_STATE_ACTIVE) {
+			pr_info("mds%d reconnect completed\n", s->s_mds);
+			kick_requests(mdsc, i, 1);
+			ceph_kick_flushing_caps(mdsc, s);
+			wake_up_session_caps(s, 1);
+		}
+	}
+}
+
+
+
+/*
+ * leases
+ */
+
+/*
+ * caller must hold session s_mutex, dentry->d_lock
+ */
+void __ceph_mdsc_drop_dentry_lease(struct dentry *dentry)
+{
+	struct ceph_dentry_info *di = ceph_dentry(dentry);
+
+	ceph_put_mds_session(di->lease_session);
+	di->lease_session = NULL;
+}
+
+static void handle_lease(struct ceph_mds_client *mdsc,
+			 struct ceph_mds_session *session,
+			 struct ceph_msg *msg)
+{
+	struct super_block *sb = mdsc->client->sb;
+	struct inode *inode;
+	struct ceph_inode_info *ci;
+	struct dentry *parent, *dentry;
+	struct ceph_dentry_info *di;
+	int mds = session->s_mds;
+	struct ceph_mds_lease *h = msg->front.iov_base;
+	struct ceph_vino vino;
+	int mask;
+	struct qstr dname;
+	int release = 0;
+
+	dout("handle_lease from mds%d\n", mds);
+
+	/* decode */
+	if (msg->front.iov_len < sizeof(*h) + sizeof(u32))
+		goto bad;
+	vino.ino = le64_to_cpu(h->ino);
+	vino.snap = CEPH_NOSNAP;
+	mask = le16_to_cpu(h->mask);
+	dname.name = (void *)h + sizeof(*h) + sizeof(u32);
+	dname.len = msg->front.iov_len - sizeof(*h) - sizeof(u32);
+	if (dname.len != get_unaligned_le32(h+1))
+		goto bad;
+
+	mutex_lock(&session->s_mutex);
+	session->s_seq++;
+
+	/* lookup inode */
+	inode = ceph_find_inode(sb, vino);
+	dout("handle_lease '%s', mask %d, ino %llx %p\n",
+	     ceph_lease_op_name(h->action), mask, vino.ino, inode);
+	if (inode == NULL) {
+		dout("handle_lease no inode %llx\n", vino.ino);
+		goto release;
+	}
+	ci = ceph_inode(inode);
+
+	/* dentry */
+	parent = d_find_alias(inode);
+	if (!parent) {
+		dout("no parent dentry on inode %p\n", inode);
+		WARN_ON(1);
+		goto release;  /* hrm... */
+	}
+	dname.hash = full_name_hash(dname.name, dname.len);
+	dentry = d_lookup(parent, &dname);
+	dput(parent);
+	if (!dentry)
+		goto release;
+
+	spin_lock(&dentry->d_lock);
+	di = ceph_dentry(dentry);
+	switch (h->action) {
+	case CEPH_MDS_LEASE_REVOKE:
+		if (di && di->lease_session == session) {
+			h->seq = cpu_to_le32(di->lease_seq);
+			__ceph_mdsc_drop_dentry_lease(dentry);
+		}
+		release = 1;
+		break;
+
+	case CEPH_MDS_LEASE_RENEW:
+		if (di && di->lease_session == session &&
+		    di->lease_gen == session->s_cap_gen &&
+		    di->lease_renew_from &&
+		    di->lease_renew_after == 0) {
+			unsigned long duration =
+				le32_to_cpu(h->duration_ms) * HZ / 1000;
+
+			di->lease_seq = le32_to_cpu(h->seq);
+			dentry->d_time = di->lease_renew_from + duration;
+			di->lease_renew_after = di->lease_renew_from +
+				(duration >> 1);
+			di->lease_renew_from = 0;
+		}
+		break;
+	}
+	spin_unlock(&dentry->d_lock);
+	dput(dentry);
+
+	if (!release)
+		goto out;
+
+release:
+	/* let's just reuse the same message */
+	h->action = CEPH_MDS_LEASE_REVOKE_ACK;
+	ceph_msg_get(msg);
+	ceph_con_send(&session->s_con, msg);
+
+out:
+	iput(inode);
+	mutex_unlock(&session->s_mutex);
+	return;
+
+bad:
+	pr_err("corrupt lease message\n");
+	ceph_msg_dump(msg);
+}
+
+void ceph_mdsc_lease_send_msg(struct ceph_mds_session *session,
+			      struct inode *inode,
+			      struct dentry *dentry, char action,
+			      u32 seq)
+{
+	struct ceph_msg *msg;
+	struct ceph_mds_lease *lease;
+	int len = sizeof(*lease) + sizeof(u32);
+	int dnamelen = 0;
+
+	dout("lease_send_msg inode %p dentry %p %s to mds%d\n",
+	     inode, dentry, ceph_lease_op_name(action), session->s_mds);
+	dnamelen = dentry->d_name.len;
+	len += dnamelen;
+
+	msg = ceph_msg_new(CEPH_MSG_CLIENT_LEASE, len, 0, 0, NULL);
+	if (IS_ERR(msg))
+		return;
+	lease = msg->front.iov_base;
+	lease->action = action;
+	lease->mask = cpu_to_le16(CEPH_LOCK_DN);
+	lease->ino = cpu_to_le64(ceph_vino(inode).ino);
+	lease->first = lease->last = cpu_to_le64(ceph_vino(inode).snap);
+	lease->seq = cpu_to_le32(seq);
+	put_unaligned_le32(dnamelen, lease + 1);
+	memcpy((void *)(lease + 1) + 4, dentry->d_name.name, dnamelen);
+
+	/*
+	 * if this is a preemptive lease RELEASE, no need to
+	 * flush request stream, since the actual request will
+	 * soon follow.
+	 */
+	msg->more_to_follow = (action == CEPH_MDS_LEASE_RELEASE);
+
+	ceph_con_send(&session->s_con, msg);
+}
+
+/*
+ * Preemptively release a lease we expect to invalidate anyway.
+ * Pass @inode always, @dentry is optional.
+ */
+void ceph_mdsc_lease_release(struct ceph_mds_client *mdsc, struct inode *inode,
+			     struct dentry *dentry, int mask)
+{
+	struct ceph_dentry_info *di;
+	struct ceph_mds_session *session;
+	u32 seq;
+
+	BUG_ON(inode == NULL);
+	BUG_ON(dentry == NULL);
+	BUG_ON(mask != CEPH_LOCK_DN);
+
+	/* is dentry lease valid? */
+	spin_lock(&dentry->d_lock);
+	di = ceph_dentry(dentry);
+	if (!di || !di->lease_session ||
+	    di->lease_session->s_mds < 0 ||
+	    di->lease_gen != di->lease_session->s_cap_gen ||
+	    !time_before(jiffies, dentry->d_time)) {
+		dout("lease_release inode %p dentry %p -- "
+		     "no lease on %d\n",
+		     inode, dentry, mask);
+		spin_unlock(&dentry->d_lock);
+		return;
+	}
+
+	/* we do have a lease on this dentry; note mds and seq */
+	session = ceph_get_mds_session(di->lease_session);
+	seq = di->lease_seq;
+	__ceph_mdsc_drop_dentry_lease(dentry);
+	spin_unlock(&dentry->d_lock);
+
+	dout("lease_release inode %p dentry %p mask %d to mds%d\n",
+	     inode, dentry, mask, session->s_mds);
+	ceph_mdsc_lease_send_msg(session, inode, dentry,
+				 CEPH_MDS_LEASE_RELEASE, seq);
+	ceph_put_mds_session(session);
+}
+
+/*
+ * drop all leases (and dentry refs) in preparation for umount
+ */
+static void drop_leases(struct ceph_mds_client *mdsc)
+{
+	int i;
+
+	dout("drop_leases\n");
+	mutex_lock(&mdsc->mutex);
+	for (i = 0; i < mdsc->max_sessions; i++) {
+		struct ceph_mds_session *s = __ceph_lookup_mds_session(mdsc, i);
+		if (!s)
+			continue;
+		mutex_unlock(&mdsc->mutex);
+		mutex_lock(&s->s_mutex);
+		mutex_unlock(&s->s_mutex);
+		ceph_put_mds_session(s);
+		mutex_lock(&mdsc->mutex);
+	}
+	mutex_unlock(&mdsc->mutex);
+}
+
+
+
+/*
+ * delayed work -- periodically trim expired leases, renew caps with mds
+ */
+static void schedule_delayed(struct ceph_mds_client *mdsc)
+{
+	int delay = 5;
+	unsigned hz = round_jiffies_relative(HZ * delay);
+	schedule_delayed_work(&mdsc->delayed_work, hz);
+}
+
+static void delayed_work(struct work_struct *work)
+{
+	int i;
+	struct ceph_mds_client *mdsc =
+		container_of(work, struct ceph_mds_client, delayed_work.work);
+	int renew_interval;
+	int renew_caps;
+
+	dout("mdsc delayed_work\n");
+	ceph_check_delayed_caps(mdsc);
+
+	mutex_lock(&mdsc->mutex);
+	renew_interval = mdsc->mdsmap->m_session_timeout >> 2;
+	renew_caps = time_after_eq(jiffies, HZ*renew_interval +
+				   mdsc->last_renew_caps);
+	if (renew_caps)
+		mdsc->last_renew_caps = jiffies;
+
+	for (i = 0; i < mdsc->max_sessions; i++) {
+		struct ceph_mds_session *s = __ceph_lookup_mds_session(mdsc, i);
+		if (s == NULL)
+			continue;
+		if (s->s_state == CEPH_MDS_SESSION_CLOSING) {
+			dout("resending session close request for mds%d\n",
+			     s->s_mds);
+			request_close_session(mdsc, s);
+			ceph_put_mds_session(s);
+			continue;
+		}
+		if (s->s_ttl && time_after(jiffies, s->s_ttl)) {
+			if (s->s_state == CEPH_MDS_SESSION_OPEN) {
+				s->s_state = CEPH_MDS_SESSION_HUNG;
+				pr_info("mds%d hung\n", s->s_mds);
+			}
+		}
+		if (s->s_state < CEPH_MDS_SESSION_OPEN) {
+			/* this mds is failed or recovering, just wait */
+			ceph_put_mds_session(s);
+			continue;
+		}
+		mutex_unlock(&mdsc->mutex);
+
+		mutex_lock(&s->s_mutex);
+		if (renew_caps)
+			send_renew_caps(mdsc, s);
+		else
+			ceph_con_keepalive(&s->s_con);
+		add_cap_releases(mdsc, s, -1);
+		send_cap_releases(mdsc, s);
+		mutex_unlock(&s->s_mutex);
+		ceph_put_mds_session(s);
+
+		mutex_lock(&mdsc->mutex);
+	}
+	mutex_unlock(&mdsc->mutex);
+
+	schedule_delayed(mdsc);
+}
+
+
+int ceph_mdsc_init(struct ceph_mds_client *mdsc, struct ceph_client *client)
+{
+	mdsc->client = client;
+	mutex_init(&mdsc->mutex);
+	mdsc->mdsmap = kzalloc(sizeof(*mdsc->mdsmap), GFP_NOFS);
+	init_completion(&mdsc->safe_umount_waiters);
+	init_completion(&mdsc->session_close_waiters);
+	INIT_LIST_HEAD(&mdsc->waiting_for_map);
+	mdsc->sessions = NULL;
+	mdsc->max_sessions = 0;
+	mdsc->stopping = 0;
+	init_rwsem(&mdsc->snap_rwsem);
+	mdsc->snap_realms = RB_ROOT;
+	INIT_LIST_HEAD(&mdsc->snap_empty);
+	spin_lock_init(&mdsc->snap_empty_lock);
+	mdsc->last_tid = 0;
+	mdsc->request_tree = RB_ROOT;
+	INIT_DELAYED_WORK(&mdsc->delayed_work, delayed_work);
+	mdsc->last_renew_caps = jiffies;
+	INIT_LIST_HEAD(&mdsc->cap_delay_list);
+	spin_lock_init(&mdsc->cap_delay_lock);
+	INIT_LIST_HEAD(&mdsc->snap_flush_list);
+	spin_lock_init(&mdsc->snap_flush_lock);
+	mdsc->cap_flush_seq = 0;
+	INIT_LIST_HEAD(&mdsc->cap_dirty);
+	mdsc->num_cap_flushing = 0;
+	spin_lock_init(&mdsc->cap_dirty_lock);
+	init_waitqueue_head(&mdsc->cap_flushing_wq);
+	spin_lock_init(&mdsc->dentry_lru_lock);
+	INIT_LIST_HEAD(&mdsc->dentry_lru);
+	return 0;
+}
+
+/*
+ * Wait for safe replies on open mds requests.  If we time out, drop
+ * all requests from the tree to avoid dangling dentry refs.
+ */
+static void wait_requests(struct ceph_mds_client *mdsc)
+{
+	struct ceph_mds_request *req;
+	struct ceph_client *client = mdsc->client;
+
+	mutex_lock(&mdsc->mutex);
+	if (__get_oldest_req(mdsc)) {
+		mutex_unlock(&mdsc->mutex);
+
+		dout("wait_requests waiting for requests\n");
+		wait_for_completion_timeout(&mdsc->safe_umount_waiters,
+				    client->mount_args->mount_timeout * HZ);
+
+		/* tear down remaining requests */
+		mutex_lock(&mdsc->mutex);
+		while ((req = __get_oldest_req(mdsc))) {
+			dout("wait_requests timed out on tid %llu\n",
+			     req->r_tid);
+			__unregister_request(mdsc, req);
+		}
+	}
+	mutex_unlock(&mdsc->mutex);
+	dout("wait_requests done\n");
+}
+
+/*
+ * called before mount is ro, and before dentries are torn down.
+ * (hmm, does this still race with new lookups?)
+ */
+void ceph_mdsc_pre_umount(struct ceph_mds_client *mdsc)
+{
+	dout("pre_umount\n");
+	mdsc->stopping = 1;
+
+	drop_leases(mdsc);
+	ceph_flush_dirty_caps(mdsc);
+	wait_requests(mdsc);
+}
+
+/*
+ * wait for all write mds requests to flush.
+ */
+static void wait_unsafe_requests(struct ceph_mds_client *mdsc, u64 want_tid)
+{
+	struct ceph_mds_request *req = NULL;
+	struct rb_node *n;
+
+	mutex_lock(&mdsc->mutex);
+	dout("wait_unsafe_requests want %lld\n", want_tid);
+	req = __get_oldest_req(mdsc);
+	while (req && req->r_tid <= want_tid) {
+		if ((req->r_op & CEPH_MDS_OP_WRITE)) {
+			/* write op */
+			ceph_mdsc_get_request(req);
+			mutex_unlock(&mdsc->mutex);
+			dout("wait_unsafe_requests  wait on %llu (want %llu)\n",
+			     req->r_tid, want_tid);
+			wait_for_completion(&req->r_safe_completion);
+			mutex_lock(&mdsc->mutex);
+			n = rb_next(&req->r_node);
+			ceph_mdsc_put_request(req);
+		} else {
+			n = rb_next(&req->r_node);
+		}
+		if (!n)
+			break;
+		req = rb_entry(n, struct ceph_mds_request, r_node);
+	}
+	mutex_unlock(&mdsc->mutex);
+	dout("wait_unsafe_requests done\n");
+}
+
+void ceph_mdsc_sync(struct ceph_mds_client *mdsc)
+{
+	u64 want_tid, want_flush;
+
+	dout("sync\n");
+	mutex_lock(&mdsc->mutex);
+	want_tid = mdsc->last_tid;
+	want_flush = mdsc->cap_flush_seq;
+	mutex_unlock(&mdsc->mutex);
+	dout("sync want tid %lld flush_seq %lld\n", want_tid, want_flush);
+
+	ceph_flush_dirty_caps(mdsc);
+
+	wait_unsafe_requests(mdsc, want_tid);
+	wait_event(mdsc->cap_flushing_wq, check_cap_flush(mdsc, want_flush));
+}
+
+
+/*
+ * called after sb is ro.
+ */
+void ceph_mdsc_close_sessions(struct ceph_mds_client *mdsc)
+{
+	struct ceph_mds_session *session;
+	int i;
+	int n;
+	struct ceph_client *client = mdsc->client;
+	unsigned long started, timeout = client->mount_args->mount_timeout * HZ;
+
+	dout("close_sessions\n");
+
+	mutex_lock(&mdsc->mutex);
+
+	/* close sessions */
+	started = jiffies;
+	while (time_before(jiffies, started + timeout)) {
+		dout("closing sessions\n");
+		n = 0;
+		for (i = 0; i < mdsc->max_sessions; i++) {
+			session = __ceph_lookup_mds_session(mdsc, i);
+			if (!session)
+				continue;
+			mutex_unlock(&mdsc->mutex);
+			mutex_lock(&session->s_mutex);
+			__close_session(mdsc, session);
+			mutex_unlock(&session->s_mutex);
+			ceph_put_mds_session(session);
+			mutex_lock(&mdsc->mutex);
+			n++;
+		}
+		if (n == 0)
+			break;
+
+		if (client->mount_state == CEPH_MOUNT_SHUTDOWN)
+			break;
+
+		dout("waiting for sessions to close\n");
+		mutex_unlock(&mdsc->mutex);
+		wait_for_completion_timeout(&mdsc->session_close_waiters,
+					    timeout);
+		mutex_lock(&mdsc->mutex);
+	}
+
+	/* tear down remaining sessions */
+	for (i = 0; i < mdsc->max_sessions; i++) {
+		if (mdsc->sessions[i]) {
+			session = get_session(mdsc->sessions[i]);
+			__unregister_session(mdsc, session);
+			mutex_unlock(&mdsc->mutex);
+			mutex_lock(&session->s_mutex);
+			remove_session_caps(session);
+			mutex_unlock(&session->s_mutex);
+			ceph_put_mds_session(session);
+			mutex_lock(&mdsc->mutex);
+		}
+	}
+
+	WARN_ON(!list_empty(&mdsc->cap_delay_list));
+
+	mutex_unlock(&mdsc->mutex);
+
+	ceph_cleanup_empty_realms(mdsc);
+
+	cancel_delayed_work_sync(&mdsc->delayed_work); /* cancel timer */
+
+	dout("stopped\n");
+}
+
+void ceph_mdsc_stop(struct ceph_mds_client *mdsc)
+{
+	dout("stop\n");
+	cancel_delayed_work_sync(&mdsc->delayed_work); /* cancel timer */
+	if (mdsc->mdsmap)
+		ceph_mdsmap_destroy(mdsc->mdsmap);
+	kfree(mdsc->sessions);
+}
+
+
+/*
+ * handle mds map update.
+ */
+void ceph_mdsc_handle_map(struct ceph_mds_client *mdsc, struct ceph_msg *msg)
+{
+	u32 epoch;
+	u32 maplen;
+	void *p = msg->front.iov_base;
+	void *end = p + msg->front.iov_len;
+	struct ceph_mdsmap *newmap, *oldmap;
+	struct ceph_fsid fsid;
+	int err = -EINVAL;
+
+	ceph_decode_need(&p, end, sizeof(fsid)+2*sizeof(u32), bad);
+	ceph_decode_copy(&p, &fsid, sizeof(fsid));
+	if (ceph_check_fsid(mdsc->client, &fsid) < 0)
+		return;
+	epoch = ceph_decode_32(&p);
+	maplen = ceph_decode_32(&p);
+	dout("handle_map epoch %u len %d\n", epoch, (int)maplen);
+
+	/* do we need it? */
+	ceph_monc_got_mdsmap(&mdsc->client->monc, epoch);
+	mutex_lock(&mdsc->mutex);
+	if (mdsc->mdsmap && epoch <= mdsc->mdsmap->m_epoch) {
+		dout("handle_map epoch %u <= our %u\n",
+		     epoch, mdsc->mdsmap->m_epoch);
+		mutex_unlock(&mdsc->mutex);
+		return;
+	}
+
+	newmap = ceph_mdsmap_decode(&p, end);
+	if (IS_ERR(newmap)) {
+		err = PTR_ERR(newmap);
+		goto bad_unlock;
+	}
+
+	/* swap into place */
+	if (mdsc->mdsmap) {
+		oldmap = mdsc->mdsmap;
+		mdsc->mdsmap = newmap;
+		check_new_map(mdsc, newmap, oldmap);
+		ceph_mdsmap_destroy(oldmap);
+	} else {
+		mdsc->mdsmap = newmap;  /* first mds map */
+	}
+	mdsc->client->sb->s_maxbytes = mdsc->mdsmap->m_max_file_size;
+
+	__wake_requests(mdsc, &mdsc->waiting_for_map);
+
+	mutex_unlock(&mdsc->mutex);
+	schedule_delayed(mdsc);
+	return;
+
+bad_unlock:
+	mutex_unlock(&mdsc->mutex);
+bad:
+	pr_err("error decoding mdsmap %d\n", err);
+	return;
+}
+
+static struct ceph_connection *con_get(struct ceph_connection *con)
+{
+	struct ceph_mds_session *s = con->private;
+
+	if (get_session(s)) {
+		dout("mdsc con_get %p ok (%d)\n", s, atomic_read(&s->s_ref));
+		return con;
+	}
+	dout("mdsc con_get %p FAIL\n", s);
+	return NULL;
+}
+
+static void con_put(struct ceph_connection *con)
+{
+	struct ceph_mds_session *s = con->private;
+
+	ceph_put_mds_session(s);
+	dout("mdsc con_put %p (%d)\n", s, atomic_read(&s->s_ref));
+}
+
+/*
+ * if the client is unresponsive for long enough, the mds will kill
+ * the session entirely.
+ */
+static void peer_reset(struct ceph_connection *con)
+{
+	struct ceph_mds_session *s = con->private;
+
+	pr_err("mds%d gave us the boot.  IMPLEMENT RECONNECT.\n",
+	       s->s_mds);
+}
+
+static void dispatch(struct ceph_connection *con, struct ceph_msg *msg)
+{
+	struct ceph_mds_session *s = con->private;
+	struct ceph_mds_client *mdsc = s->s_mdsc;
+	int type = le16_to_cpu(msg->hdr.type);
+
+	mutex_lock(&mdsc->mutex);
+	if (__verify_registered_session(mdsc, s) < 0) {
+		mutex_unlock(&mdsc->mutex);
+		goto out;
+	}
+	mutex_unlock(&mdsc->mutex);
+
+	switch (type) {
+	case CEPH_MSG_MDS_MAP:
+		ceph_mdsc_handle_map(mdsc, msg);
+		break;
+	case CEPH_MSG_CLIENT_SESSION:
+		handle_session(s, msg);
+		break;
+	case CEPH_MSG_CLIENT_REPLY:
+		handle_reply(s, msg);
+		break;
+	case CEPH_MSG_CLIENT_REQUEST_FORWARD:
+		handle_forward(mdsc, s, msg);
+		break;
+	case CEPH_MSG_CLIENT_CAPS:
+		ceph_handle_caps(s, msg);
+		break;
+	case CEPH_MSG_CLIENT_SNAP:
+		ceph_handle_snap(mdsc, s, msg);
+		break;
+	case CEPH_MSG_CLIENT_LEASE:
+		handle_lease(mdsc, s, msg);
+		break;
+
+	default:
+		pr_err("received unknown message type %d %s\n", type,
+		       ceph_msg_type_name(type));
+	}
+out:
+	ceph_msg_put(msg);
+}
+
+/*
+ * authentication
+ */
+static int get_authorizer(struct ceph_connection *con,
+			  void **buf, int *len, int *proto,
+			  void **reply_buf, int *reply_len, int force_new)
+{
+	struct ceph_mds_session *s = con->private;
+	struct ceph_mds_client *mdsc = s->s_mdsc;
+	struct ceph_auth_client *ac = mdsc->client->monc.auth;
+	int ret = 0;
+
+	if (force_new && s->s_authorizer) {
+		ac->ops->destroy_authorizer(ac, s->s_authorizer);
+		s->s_authorizer = NULL;
+	}
+	if (s->s_authorizer == NULL) {
+		if (ac->ops->create_authorizer) {
+			ret = ac->ops->create_authorizer(
+				ac, CEPH_ENTITY_TYPE_MDS,
+				&s->s_authorizer,
+				&s->s_authorizer_buf,
+				&s->s_authorizer_buf_len,
+				&s->s_authorizer_reply_buf,
+				&s->s_authorizer_reply_buf_len);
+			if (ret)
+				return ret;
+		}
+	}
+
+	*proto = ac->protocol;
+	*buf = s->s_authorizer_buf;
+	*len = s->s_authorizer_buf_len;
+	*reply_buf = s->s_authorizer_reply_buf;
+	*reply_len = s->s_authorizer_reply_buf_len;
+	return 0;
+}
+
+
+static int verify_authorizer_reply(struct ceph_connection *con, int len)
+{
+	struct ceph_mds_session *s = con->private;
+	struct ceph_mds_client *mdsc = s->s_mdsc;
+	struct ceph_auth_client *ac = mdsc->client->monc.auth;
+
+	return ac->ops->verify_authorizer_reply(ac, s->s_authorizer, len);
+}
+
+static int invalidate_authorizer(struct ceph_connection *con)
+{
+	struct ceph_mds_session *s = con->private;
+	struct ceph_mds_client *mdsc = s->s_mdsc;
+	struct ceph_auth_client *ac = mdsc->client->monc.auth;
+
+	if (ac->ops->invalidate_authorizer)
+		ac->ops->invalidate_authorizer(ac, CEPH_ENTITY_TYPE_MDS);
+
+	return ceph_monc_validate_auth(&mdsc->client->monc);
+}
+
+const static struct ceph_connection_operations mds_con_ops = {
+	.get = con_get,
+	.put = con_put,
+	.dispatch = dispatch,
+	.get_authorizer = get_authorizer,
+	.verify_authorizer_reply = verify_authorizer_reply,
+	.invalidate_authorizer = invalidate_authorizer,
+	.peer_reset = peer_reset,
+};
+
+
+
+
+/* eof */