Initial import

1 files changed, 3871 insertions, 0 deletions

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
new file mode 100644
index 000000000..84f37f34f
--- /dev/null
+++ b/fs/ceph/mds_client.c
@@ -0,0 +1,3871 @@
+#include <linux/ceph/ceph_debug.h>
+
+#include <linux/fs.h>
+#include <linux/wait.h>
+#include <linux/slab.h>
+#include <linux/gfp.h>
+#include <linux/sched.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+#include <linux/utsname.h>
+
+#include "super.h"
+#include "mds_client.h"
+
+#include <linux/ceph/ceph_features.h>
+#include <linux/ceph/messenger.h>
+#include <linux/ceph/decode.h>
+#include <linux/ceph/pagelist.h>
+#include <linux/ceph/auth.h>
+#include <linux/ceph/debugfs.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+ * are no longer valid.
+ */
+
+struct ceph_reconnect_state {
+	int nr_caps;
+	struct ceph_pagelist *pagelist;
+	bool flock;
+};
+
+static void __wake_requests(struct ceph_mds_client *mdsc,
+			    struct list_head *head);
+
+static const 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,
+			       u64 features)
+{
+	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;
+
+	if (features & CEPH_FEATURE_DIRLAYOUTHASH)
+		ceph_decode_copy_safe(p, end, &info->dir_layout,
+				      sizeof(info->dir_layout), bad);
+	else
+		memset(&info->dir_layout, 0, sizeof(info->dir_layout));
+
+	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;
+
+	if (features & CEPH_FEATURE_MDS_INLINE_DATA) {
+		ceph_decode_64_safe(p, end, info->inline_version, bad);
+		ceph_decode_32_safe(p, end, info->inline_len, bad);
+		ceph_decode_need(p, end, info->inline_len, bad);
+		info->inline_data = *p;
+		*p += info->inline_len;
+	} else
+		info->inline_version = CEPH_INLINE_NONE;
+
+	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,
+				  u64 features)
+{
+	int err;
+
+	if (info->head->is_dentry) {
+		err = parse_reply_info_in(p, end, &info->diri, features);
+		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, features);
+		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,
+				u64 features)
+{
+	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;
+
+	BUG_ON(!info->dir_in);
+	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);
+	if ((unsigned long)(info->dir_dlease + num) >
+	    (unsigned long)info->dir_in + info->dir_buf_size) {
+		pr_err("dir contents are larger than expected\n");
+		WARN_ON(1);
+		goto bad;
+	}
+
+	info->dir_nr = 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], features);
+		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 fcntl F_GETLK results
+ */
+static int parse_reply_info_filelock(void **p, void *end,
+				     struct ceph_mds_reply_info_parsed *info,
+				     u64 features)
+{
+	if (*p + sizeof(*info->filelock_reply) > end)
+		goto bad;
+
+	info->filelock_reply = *p;
+	*p += sizeof(*info->filelock_reply);
+
+	if (unlikely(*p != end))
+		goto bad;
+	return 0;
+
+bad:
+	return -EIO;
+}
+
+/*
+ * parse create results
+ */
+static int parse_reply_info_create(void **p, void *end,
+				  struct ceph_mds_reply_info_parsed *info,
+				  u64 features)
+{
+	if (features & CEPH_FEATURE_REPLY_CREATE_INODE) {
+		if (*p == end) {
+			info->has_create_ino = false;
+		} else {
+			info->has_create_ino = true;
+			info->ino = ceph_decode_64(p);
+		}
+	}
+
+	if (unlikely(*p != end))
+		goto bad;
+	return 0;
+
+bad:
+	return -EIO;
+}
+
+/*
+ * parse extra results
+ */
+static int parse_reply_info_extra(void **p, void *end,
+				  struct ceph_mds_reply_info_parsed *info,
+				  u64 features)
+{
+	if (info->head->op == CEPH_MDS_OP_GETFILELOCK)
+		return parse_reply_info_filelock(p, end, info, features);
+	else if (info->head->op == CEPH_MDS_OP_READDIR ||
+		 info->head->op == CEPH_MDS_OP_LSSNAP)
+		return parse_reply_info_dir(p, end, info, features);
+	else if (info->head->op == CEPH_MDS_OP_CREATE)
+		return parse_reply_info_create(p, end, info, features);
+	else
+		return -EIO;
+}
+
+/*
+ * parse entire mds reply
+ */
+static int parse_reply_info(struct ceph_msg *msg,
+			    struct ceph_mds_reply_info_parsed *info,
+			    u64 features)
+{
+	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) {
+		ceph_decode_need(&p, end, len, bad);
+		err = parse_reply_info_trace(&p, p+len, info, features);
+		if (err < 0)
+			goto out_bad;
+	}
+
+	/* extra */
+	ceph_decode_32_safe(&p, end, len, bad);
+	if (len > 0) {
+		ceph_decode_need(&p, end, len, bad);
+		err = parse_reply_info_extra(&p, p+len, info, features);
+		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)
+{
+	if (!info->dir_in)
+		return;
+	free_pages((unsigned long)info->dir_in, get_order(info->dir_buf_size));
+}
+
+
+/*
+ * sessions
+ */
+const char *ceph_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_auth.authorizer)
+			ceph_auth_destroy_authorizer(
+				s->s_mdsc->fsc->client->monc.auth,
+				s->s_auth.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;
+
+	if (mds >= mdsc->mdsmap->m_max_mds)
+		return ERR_PTR(-EINVAL);
+
+	s = kzalloc(sizeof(*s), GFP_NOFS);
+	if (!s)
+		return ERR_PTR(-ENOMEM);
+	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(&s->s_con, s, &mds_con_ops, &mdsc->fsc->client->msgr);
+
+	spin_lock_init(&s->s_gen_ttl_lock);
+	s->s_cap_gen = 0;
+	s->s_cap_ttl = jiffies - 1;
+
+	spin_lock_init(&s->s_cap_lock);
+	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_reconnect = 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(&mdsc->num_sessions);
+	atomic_inc(&s->s_ref);  /* one ref to sessions[], one to caller */
+
+	ceph_con_open(&s->s_con, CEPH_ENTITY_TYPE_MDS, mds,
+		      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);
+	atomic_dec(&mdsc->num_sessions);
+}
+
+/*
+ * 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);
+	destroy_reply_info(&req->r_reply_info);
+	if (req->r_request)
+		ceph_msg_put(req->r_request);
+	if (req->r_reply)
+		ceph_msg_put(req->r_reply);
+	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);
+	iput(req->r_target_inode);
+	if (req->r_dentry)
+		dput(req->r_dentry);
+	if (req->r_old_dentry)
+		dput(req->r_old_dentry);
+	if (req->r_old_dentry_dir) {
+		/*
+		 * track (and drop pins for) r_old_dentry_dir
+		 * separately, since r_old_dentry's d_parent may have
+		 * changed between the dir mutex being dropped and
+		 * this request being freed.
+		 */
+		ceph_put_cap_refs(ceph_inode(req->r_old_dentry_dir),
+				  CEPH_CAP_PIN);
+		iput(req->r_old_dentry_dir);
+	}
+	kfree(req->r_path1);
+	kfree(req->r_path2);
+	if (req->r_pagelist)
+		ceph_pagelist_release(req->r_pagelist);
+	put_request_session(req);
+	ceph_unreserve_caps(req->r_mdsc, &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(mdsc, &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);
+
+	req->r_uid = current_fsuid();
+	req->r_gid = current_fsgid();
+
+	if (dir) {
+		struct ceph_inode_info *ci = ceph_inode(dir);
+
+		ihold(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);
+	RB_CLEAR_NODE(&req->r_node);
+
+	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);
+
+		iput(req->r_unsafe_dir);
+		req->r_unsafe_dir = NULL;
+	}
+
+	complete_all(&req->r_safe_completion);
+
+	ceph_mdsc_put_request(req);
+}
+
+/*
+ * 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 struct dentry *get_nonsnap_parent(struct dentry *dentry)
+{
+	/*
+	 * we don't need to worry about protecting the d_parent access
+	 * here because we never renaming inside the snapped namespace
+	 * except to resplice to another snapdir, and either the old or new
+	 * result is a valid result.
+	 */
+	while (!IS_ROOT(dentry) && ceph_snap(d_inode(dentry)) != CEPH_NOSNAP)
+		dentry = dentry->d_parent;
+	return dentry;
+}
+
+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) {
+		/* ignore race with rename; old or new d_parent is okay */
+		struct dentry *parent = req->r_dentry->d_parent;
+		struct inode *dir = d_inode(parent);
+
+		if (dir->i_sb != mdsc->fsc->sb) {
+			/* not this fs! */
+			inode = d_inode(req->r_dentry);
+		} else if (ceph_snap(dir) != CEPH_NOSNAP) {
+			/* direct snapped/virtual snapdir requests
+			 * based on parent dir inode */
+			struct dentry *dn = get_nonsnap_parent(parent);
+			inode = d_inode(dn);
+			dout("__choose_mds using nonsnap parent %p\n", inode);
+		} else {
+			/* dentry target */
+			inode = d_inode(req->r_dentry);
+			if (!inode || mode == USE_AUTH_MDS) {
+				/* dir + name */
+				inode = dir;
+				hash = ceph_dentry_hash(dir, req->r_dentry);
+				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, mds,
+				     (int)r, frag.ndist);
+				if (ceph_mdsmap_get_state(mdsc->mdsmap, mds) >=
+				    CEPH_MDS_STATE_ACTIVE)
+					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);
+				if (ceph_mdsmap_get_state(mdsc->mdsmap, mds) >=
+				    CEPH_MDS_STATE_ACTIVE)
+					return mds;
+			}
+		}
+	}
+
+	spin_lock(&ci->i_ceph_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(&ci->i_ceph_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(&ci->i_ceph_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), GFP_NOFS,
+			   false);
+	if (!msg) {
+		pr_err("create_session_msg ENOMEM creating msg\n");
+		return NULL;
+	}
+	h = msg->front.iov_base;
+	h->op = cpu_to_le32(op);
+	h->seq = cpu_to_le64(seq);
+
+	return msg;
+}
+
+/*
+ * session message, specialization for CEPH_SESSION_REQUEST_OPEN
+ * to include additional client metadata fields.
+ */
+static struct ceph_msg *create_session_open_msg(struct ceph_mds_client *mdsc, u64 seq)
+{
+	struct ceph_msg *msg;
+	struct ceph_mds_session_head *h;
+	int i = -1;
+	int metadata_bytes = 0;
+	int metadata_key_count = 0;
+	struct ceph_options *opt = mdsc->fsc->client->options;
+	void *p;
+
+	const char* metadata[][2] = {
+		{"hostname", utsname()->nodename},
+		{"kernel_version", utsname()->release},
+		{"entity_id", opt->name ? opt->name : ""},
+		{NULL, NULL}
+	};
+
+	/* Calculate serialized length of metadata */
+	metadata_bytes = 4;  /* map length */
+	for (i = 0; metadata[i][0] != NULL; ++i) {
+		metadata_bytes += 8 + strlen(metadata[i][0]) +
+			strlen(metadata[i][1]);
+		metadata_key_count++;
+	}
+
+	/* Allocate the message */
+	msg = ceph_msg_new(CEPH_MSG_CLIENT_SESSION, sizeof(*h) + metadata_bytes,
+			   GFP_NOFS, false);
+	if (!msg) {
+		pr_err("create_session_msg ENOMEM creating msg\n");
+		return NULL;
+	}
+	h = msg->front.iov_base;
+	h->op = cpu_to_le32(CEPH_SESSION_REQUEST_OPEN);
+	h->seq = cpu_to_le64(seq);
+
+	/*
+	 * Serialize client metadata into waiting buffer space, using
+	 * the format that userspace expects for map<string, string>
+	 *
+	 * ClientSession messages with metadata are v2
+	 */
+	msg->hdr.version = cpu_to_le16(2);
+	msg->hdr.compat_version = cpu_to_le16(1);
+
+	/* The write pointer, following the session_head structure */
+	p = msg->front.iov_base + sizeof(*h);
+
+	/* Number of entries in the map */
+	ceph_encode_32(&p, metadata_key_count);
+
+	/* Two length-prefixed strings for each entry in the map */
+	for (i = 0; metadata[i][0] != NULL; ++i) {
+		size_t const key_len = strlen(metadata[i][0]);
+		size_t const val_len = strlen(metadata[i][1]);
+
+		ceph_encode_32(&p, key_len);
+		memcpy(p, metadata[i][0], key_len);
+		p += key_len;
+		ceph_encode_32(&p, val_len);
+		memcpy(p, metadata[i][1], val_len);
+		p += val_len;
+	}
+
+	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;
+
+	/* 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_open_msg(mdsc, session->s_seq);
+	if (!msg)
+		return -ENOMEM;
+	ceph_con_send(&session->s_con, msg);
+	return 0;
+}
+
+/*
+ * open sessions for any export targets for the given mds
+ *
+ * called under mdsc->mutex
+ */
+static struct ceph_mds_session *
+__open_export_target_session(struct ceph_mds_client *mdsc, int target)
+{
+	struct ceph_mds_session *session;
+
+	session = __ceph_lookup_mds_session(mdsc, target);
+	if (!session) {
+		session = register_session(mdsc, target);
+		if (IS_ERR(session))
+			return session;
+	}
+	if (session->s_state == CEPH_MDS_SESSION_NEW ||
+	    session->s_state == CEPH_MDS_SESSION_CLOSING)
+		__open_session(mdsc, session);
+
+	return session;
+}
+
+struct ceph_mds_session *
+ceph_mdsc_open_export_target_session(struct ceph_mds_client *mdsc, int target)
+{
+	struct ceph_mds_session *session;
+
+	dout("open_export_target_session to mds%d\n", target);
+
+	mutex_lock(&mdsc->mutex);
+	session = __open_export_target_session(mdsc, target);
+	mutex_unlock(&mdsc->mutex);
+
+	return session;
+}
+
+static void __open_export_target_sessions(struct ceph_mds_client *mdsc,
+					  struct ceph_mds_session *session)
+{
+	struct ceph_mds_info *mi;
+	struct ceph_mds_session *ts;
+	int i, mds = session->s_mds;
+
+	if (mds >= mdsc->mdsmap->m_max_mds)
+		return;
+
+	mi = &mdsc->mdsmap->m_info[mds];
+	dout("open_export_target_sessions for mds%d (%d targets)\n",
+	     session->s_mds, mi->num_export_targets);
+
+	for (i = 0; i < mi->num_export_targets; i++) {
+		ts = __open_export_target_session(mdsc, mi->export_targets[i]);
+		if (!IS_ERR(ts))
+			ceph_put_mds_session(ts);
+	}
+}
+
+void ceph_mdsc_open_export_target_sessions(struct ceph_mds_client *mdsc,
+					   struct ceph_mds_session *session)
+{
+	mutex_lock(&mdsc->mutex);
+	__open_export_target_sessions(mdsc, session);
+	mutex_unlock(&mdsc->mutex);
+}
+
+/*
+ * 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);
+}
+
+static void cleanup_session_requests(struct ceph_mds_client *mdsc,
+				     struct ceph_mds_session *session)
+{
+	struct ceph_mds_request *req;
+	struct rb_node *p;
+
+	dout("cleanup_session_requests mds%d\n", session->s_mds);
+	mutex_lock(&mdsc->mutex);
+	while (!list_empty(&session->s_unsafe)) {
+		req = list_first_entry(&session->s_unsafe,
+				       struct ceph_mds_request, r_unsafe_item);
+		list_del_init(&req->r_unsafe_item);
+		pr_info(" dropping unsafe request %llu\n", req->r_tid);
+		__unregister_request(mdsc, req);
+	}
+	/* zero r_attempts, so kick_requests() will re-send requests */
+	p = rb_first(&mdsc->request_tree);
+	while (p) {
+		req = rb_entry(p, struct ceph_mds_request, r_node);
+		p = rb_next(p);
+		if (req->r_session &&
+		    req->r_session->s_mds == session->s_mds)
+			req->r_attempts = 0;
+	}
+	mutex_unlock(&mdsc->mutex);
+}
+
+/*
+ * Helper to safely iterate over all caps associated with a session, with
+ * special care taken to handle a racing __ceph_remove_cap().
+ *
+ * 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(session->s_mdsc, 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);
+
+	iput(last_inode);
+	if (old_cap)
+		ceph_put_cap(session->s_mdsc, 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);
+	int drop = 0;
+
+	dout("removing cap %p, ci is %p, inode is %p\n",
+	     cap, ci, &ci->vfs_inode);
+	spin_lock(&ci->i_ceph_lock);
+	__ceph_remove_cap(cap, false);
+	if (!ci->i_auth_cap) {
+		struct ceph_mds_client *mdsc =
+			ceph_sb_to_client(inode->i_sb)->mdsc;
+
+		spin_lock(&mdsc->cap_dirty_lock);
+		if (!list_empty(&ci->i_dirty_item)) {
+			pr_info(" dropping dirty %s state for %p %lld\n",
+				ceph_cap_string(ci->i_dirty_caps),
+				inode, ceph_ino(inode));
+			ci->i_dirty_caps = 0;
+			list_del_init(&ci->i_dirty_item);
+			drop = 1;
+		}
+		if (!list_empty(&ci->i_flushing_item)) {
+			pr_info(" dropping dirty+flushing %s state for %p %lld\n",
+				ceph_cap_string(ci->i_flushing_caps),
+				inode, ceph_ino(inode));
+			ci->i_flushing_caps = 0;
+			list_del_init(&ci->i_flushing_item);
+			mdsc->num_cap_flushing--;
+			drop = 1;
+		}
+		spin_unlock(&mdsc->cap_dirty_lock);
+	}
+	spin_unlock(&ci->i_ceph_lock);
+	while (drop--)
+		iput(inode);
+	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);
+
+	spin_lock(&session->s_cap_lock);
+	if (session->s_nr_caps > 0) {
+		struct super_block *sb = session->s_mdsc->fsc->sb;
+		struct inode *inode;
+		struct ceph_cap *cap, *prev = NULL;
+		struct ceph_vino vino;
+		/*
+		 * iterate_session_caps() skips inodes that are being
+		 * deleted, we need to wait until deletions are complete.
+		 * __wait_on_freeing_inode() is designed for the job,
+		 * but it is not exported, so use lookup inode function
+		 * to access it.
+		 */
+		while (!list_empty(&session->s_caps)) {
+			cap = list_entry(session->s_caps.next,
+					 struct ceph_cap, session_caps);
+			if (cap == prev)
+				break;
+			prev = cap;
+			vino = cap->ci->i_vino;
+			spin_unlock(&session->s_cap_lock);
+
+			inode = ceph_find_inode(sb, vino);
+			iput(inode);
+
+			spin_lock(&session->s_cap_lock);
+		}
+	}
+	spin_unlock(&session->s_cap_lock);
+
+	BUG_ON(session->s_nr_caps > 0);
+	BUG_ON(!list_empty(&session->s_cap_flushing));
+	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_all(&ci->i_cap_wq);
+	if (arg) {
+		spin_lock(&ci->i_ceph_lock);
+		ci->i_wanted_max_size = 0;
+		ci->i_requested_max_size = 0;
+		spin_unlock(&ci->i_ceph_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);
+	session->s_renew_requested = jiffies;
+
+	/* 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));
+	msg = create_session_msg(CEPH_SESSION_REQUEST_RENEWCAPS,
+				 ++session->s_renew_seq);
+	if (!msg)
+		return -ENOMEM;
+	ceph_con_send(&session->s_con, msg);
+	return 0;
+}
+
+static int send_flushmsg_ack(struct ceph_mds_client *mdsc,
+			     struct ceph_mds_session *session, u64 seq)
+{
+	struct ceph_msg *msg;
+
+	dout("send_flushmsg_ack to mds%d (%s)s seq %lld\n",
+	     session->s_mds, ceph_session_state_name(session->s_state), seq);
+	msg = create_session_msg(CEPH_SESSION_FLUSHMSG_ACK, seq);
+	if (!msg)
+		return -ENOMEM;
+	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 && 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;
+
+	dout("request_close_session mds%d state %s seq %lld\n",
+	     session->s_mds, ceph_session_state_name(session->s_state),
+	     session->s_seq);
+	msg = create_session_msg(CEPH_SESSION_REQUEST_CLOSE, session->s_seq);
+	if (!msg)
+		return -ENOMEM;
+	ceph_con_send(&session->s_con, msg);
+	return 0;
+}
+
+/*
+ * 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, wanted, oissued, mine;
+
+	if (session->s_trim_caps <= 0)
+		return -1;
+
+	spin_lock(&ci->i_ceph_lock);
+	mine = cap->issued | cap->implemented;
+	used = __ceph_caps_used(ci);
+	wanted = __ceph_caps_file_wanted(ci);
+	oissued = __ceph_caps_issued_other(ci, cap);
+
+	dout("trim_caps_cb %p cap %p mine %s oissued %s used %s wanted %s\n",
+	     inode, cap, ceph_cap_string(mine), ceph_cap_string(oissued),
+	     ceph_cap_string(used), ceph_cap_string(wanted));
+	if (cap == ci->i_auth_cap) {
+		if (ci->i_dirty_caps | ci->i_flushing_caps)
+			goto out;
+		if ((used | wanted) & CEPH_CAP_ANY_WR)
+			goto out;
+	}
+	if ((used | wanted) & ~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, true);
+	} else {
+		/* try to drop referring dentries */
+		spin_unlock(&ci->i_ceph_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(&ci->i_ceph_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;
+	}
+
+	ceph_add_cap_releases(mdsc, session);
+	ceph_send_cap_releases(mdsc, session);
+	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.
+ */
+int ceph_add_cap_releases(struct ceph_mds_client *mdsc,
+			  struct ceph_mds_session *session)
+{
+	struct ceph_msg *msg, *partial = NULL;
+	struct ceph_mds_cap_release *head;
+	int err = -ENOMEM;
+	int extra = mdsc->fsc->mount_options->cap_release_safety;
+	int num;
+
+	dout("add_cap_releases %p mds%d extra %d\n", session, session->s_mds,
+	     extra);
+
+	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;
+		num = le32_to_cpu(head->num);
+		if (num) {
+			dout(" partial %p with (%d/%d)\n", msg, num,
+			     (int)CEPH_CAPS_PER_RELEASE);
+			extra += CEPH_CAPS_PER_RELEASE - num;
+			partial = msg;
+		}
+	}
+	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,
+				   GFP_NOFS, false);
+		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 (partial) {
+		head = partial->front.iov_base;
+		num = le32_to_cpu(head->num);
+		dout(" queueing partial %p with %d/%d\n", partial, num,
+		     (int)CEPH_CAPS_PER_RELEASE);
+		list_move_tail(&partial->list_head,
+			       &session->s_cap_releases_done);
+		session->s_num_cap_releases -= CEPH_CAPS_PER_RELEASE - num;
+	}
+	err = 0;
+	spin_unlock(&session->s_cap_lock);
+out_unlocked:
+	return err;
+}
+
+static int check_cap_flush(struct inode *inode, u64 want_flush_seq)
+{
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	int ret;
+	spin_lock(&ci->i_ceph_lock);
+	if (ci->i_flushing_caps)
+		ret = ci->i_cap_flush_seq >= want_flush_seq;
+	else
+		ret = 1;
+	spin_unlock(&ci->i_ceph_lock);
+	return ret;
+}
+
+/*
+ * flush all dirty inode data to disk.
+ *
+ * returns true if we've flushed through want_flush_seq
+ */
+static void wait_caps_flush(struct ceph_mds_client *mdsc, u64 want_flush_seq)
+{
+	int mds;
+
+	dout("check_cap_flush want %lld\n", want_flush_seq);
+	mutex_lock(&mdsc->mutex);
+	for (mds = 0; mds < mdsc->max_sessions; mds++) {
+		struct ceph_mds_session *session = mdsc->sessions[mds];
+		struct inode *inode = NULL;
+
+		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);
+
+			if (!check_cap_flush(&ci->vfs_inode, want_flush_seq)) {
+				dout("check_cap_flush still flushing %p "
+				     "seq %lld <= %lld to mds%d\n",
+				     &ci->vfs_inode, ci->i_cap_flush_seq,
+				     want_flush_seq, session->s_mds);
+				inode = igrab(&ci->vfs_inode);
+			}
+		}
+		mutex_unlock(&session->s_mutex);
+		ceph_put_mds_session(session);
+
+		if (inode) {
+			wait_event(mdsc->cap_flushing_wq,
+				   check_cap_flush(inode, want_flush_seq));
+			iput(inode);
+		}
+
+		mutex_lock(&mdsc->mutex);
+	}
+
+	mutex_unlock(&mdsc->mutex);
+	dout("check_cap_flush ok, flushed thru %lld\n", want_flush_seq);
+}
+
+/*
+ * called under s_mutex
+ */
+void ceph_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);
+	spin_lock(&session->s_cap_lock);
+	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);
+		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_lock(&session->s_cap_lock);
+	}
+	spin_unlock(&session->s_cap_lock);
+}
+
+static void discard_cap_releases(struct ceph_mds_client *mdsc,
+				 struct ceph_mds_session *session)
+{
+	struct ceph_msg *msg;
+	struct ceph_mds_cap_release *head;
+	unsigned num;
+
+	dout("discard_cap_releases mds%d\n", session->s_mds);
+
+	if (!list_empty(&session->s_cap_releases)) {
+		/* zero out the in-progress message */
+		msg = list_first_entry(&session->s_cap_releases,
+					struct ceph_msg, list_head);
+		head = msg->front.iov_base;
+		num = le32_to_cpu(head->num);
+		dout("discard_cap_releases mds%d %p %u\n",
+		     session->s_mds, msg, num);
+		head->num = cpu_to_le32(0);
+		msg->front.iov_len = sizeof(*head);
+		session->s_num_cap_releases += num;
+	}
+
+	/* requeue completed messages */
+	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);
+
+		head = msg->front.iov_base;
+		num = le32_to_cpu(head->num);
+		dout("discard_cap_releases mds%d %p %u\n", session->s_mds, msg,
+		     num);
+		session->s_num_cap_releases += num;
+		head->num = cpu_to_le32(0);
+		msg->front.iov_len = sizeof(*head);
+		list_add(&msg->list_head, &session->s_cap_releases);
+	}
+}
+
+/*
+ * requests
+ */
+
+int ceph_alloc_readdir_reply_buffer(struct ceph_mds_request *req,
+				    struct inode *dir)
+{
+	struct ceph_inode_info *ci = ceph_inode(dir);
+	struct ceph_mds_reply_info_parsed *rinfo = &req->r_reply_info;
+	struct ceph_mount_options *opt = req->r_mdsc->fsc->mount_options;
+	size_t size = sizeof(*rinfo->dir_in) + sizeof(*rinfo->dir_dname_len) +
+		      sizeof(*rinfo->dir_dname) + sizeof(*rinfo->dir_dlease);
+	int order, num_entries;
+
+	spin_lock(&ci->i_ceph_lock);
+	num_entries = ci->i_files + ci->i_subdirs;
+	spin_unlock(&ci->i_ceph_lock);
+	num_entries = max(num_entries, 1);
+	num_entries = min(num_entries, opt->max_readdir);
+
+	order = get_order(size * num_entries);
+	while (order >= 0) {
+		rinfo->dir_in = (void*)__get_free_pages(GFP_NOFS | __GFP_NOWARN,
+							order);
+		if (rinfo->dir_in)
+			break;
+		order--;
+	}
+	if (!rinfo->dir_in)
+		return -ENOMEM;
+
+	num_entries = (PAGE_SIZE << order) / size;
+	num_entries = min(num_entries, opt->max_readdir);
+
+	rinfo->dir_buf_size = PAGE_SIZE << order;
+	req->r_num_caps = num_entries + 1;
+	req->r_args.readdir.max_entries = cpu_to_le32(num_entries);
+	req->r_args.readdir.max_bytes = cpu_to_le32(opt->max_readdir_bytes);
+	return 0;
+}
+
+/*
+ * 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);
+
+	mutex_init(&req->r_fill_mutex);
+	req->r_mdsc = mdsc;
+	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_stamp = CURRENT_TIME;
+
+	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;
+	unsigned seq;
+
+	if (dentry == NULL)
+		return ERR_PTR(-EINVAL);
+
+retry:
+	len = 0;
+	seq = read_seqbegin(&rename_lock);
+	rcu_read_lock();
+	for (temp = dentry; !IS_ROOT(temp);) {
+		struct inode *inode = d_inode(temp);
+		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;
+	}
+	rcu_read_unlock();
+	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 */
+	rcu_read_lock();
+	for (temp = dentry; !IS_ROOT(temp) && pos != 0; ) {
+		struct inode *inode;
+
+		spin_lock(&temp->d_lock);
+		inode = d_inode(temp);
+		if (inode && ceph_snap(inode) == CEPH_SNAPDIR) {
+			dout("build_path path+%d: %p SNAPDIR\n",
+			     pos, temp);
+		} else if (stop_on_nosnap && inode &&
+			   ceph_snap(inode) == CEPH_NOSNAP) {
+			spin_unlock(&temp->d_lock);
+			break;
+		} else {
+			pos -= temp->d_name.len;
+			if (pos < 0) {
+				spin_unlock(&temp->d_lock);
+				break;
+			}
+			strncpy(path + pos, temp->d_name.name,
+				temp->d_name.len);
+		}
+		spin_unlock(&temp->d_lock);
+		if (pos)
+			path[--pos] = '/';
+		temp = temp->d_parent;
+	}
+	rcu_read_unlock();
+	if (pos != 0 || read_seqretry(&rename_lock, seq)) {
+		pr_err("build_path 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(d_inode(temp));
+	*plen = len;
+	dout("build_path on %p %d built %llx '%.*s'\n",
+	     dentry, d_count(dentry), *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(d_inode(dentry->d_parent)) == CEPH_NOSNAP) {
+		*pino = ceph_ino(d_inode(dentry->d_parent));
+		*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 || rino) {
+		*ino = rino;
+		*ppath = rpath;
+		*pathlen = rpath ? strlen(rpath) : 0;
+		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, bool drop_cap_releases)
+{
+	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)) +
+		sizeof(struct timespec);
+
+	/* 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, GFP_NOFS, false);
+	if (!msg) {
+		msg = ERR_PTR(-ENOMEM);
+		goto out_free2;
+	}
+
+	msg->hdr.version = cpu_to_le16(2);
+	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(from_kuid(&init_user_ns, req->r_uid));
+	head->caller_gid = cpu_to_le32(from_kgid(&init_user_ns, req->r_gid));
+	head->args = req->r_args;
+
+	ceph_encode_filepath(&p, end, ino1, path1);
+	ceph_encode_filepath(&p, end, ino2, path2);
+
+	/* make note of release offset, in case we need to replay */
+	req->r_request_release_offset = p - msg->front.iov_base;
+
+	/* cap releases */
+	releases = 0;
+	if (req->r_inode_drop)
+		releases += ceph_encode_inode_release(&p,
+		      req->r_inode ? req->r_inode : d_inode(req->r_dentry),
+		      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,
+		      d_inode(req->r_old_dentry),
+		      mds, req->r_old_inode_drop, req->r_old_inode_unless, 0);
+
+	if (drop_cap_releases) {
+		releases = 0;
+		p = msg->front.iov_base + req->r_request_release_offset;
+	}
+
+	head->num_releases = cpu_to_le16(releases);
+
+	/* time stamp */
+	{
+		struct ceph_timespec ts;
+		ceph_encode_timespec(&ts, &req->r_stamp);
+		ceph_encode_copy(&p, &ts, sizeof(ts));
+	}
+
+	BUG_ON(p > end);
+	msg->front.iov_len = p - msg->front.iov_base;
+	msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);
+
+	if (req->r_pagelist) {
+		struct ceph_pagelist *pagelist = req->r_pagelist;
+		atomic_inc(&pagelist->refcnt);
+		ceph_msg_data_add_pagelist(msg, pagelist);
+		msg->hdr.data_len = cpu_to_le32(pagelist->length);
+	} else {
+		msg->hdr.data_len = 0;
+	}
+
+	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_all(&req->r_completion);
+}
+
+/*
+ * called under mdsc->mutex
+ */
+static int __prepare_send_request(struct ceph_mds_client *mdsc,
+				  struct ceph_mds_request *req,
+				  int mds, bool drop_cap_releases)
+{
+	struct ceph_mds_request_head *rhead;
+	struct ceph_msg *msg;
+	int flags = 0;
+
+	req->r_attempts++;
+	if (req->r_inode) {
+		struct ceph_cap *cap =
+			ceph_get_cap_for_mds(ceph_inode(req->r_inode), mds);
+
+		if (cap)
+			req->r_sent_on_mseq = cap->mseq;
+		else
+			req->r_sent_on_mseq = -1;
+	}
+	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_got_unsafe) {
+		void *p;
+		/*
+		 * Replay.  Do not regenerate message (and rebuild
+		 * paths, etc.); just use the original message.
+		 * Rebuilding paths will break for renames because
+		 * d_move mangles the src name.
+		 */
+		msg = req->r_request;
+		rhead = msg->front.iov_base;
+
+		flags = le32_to_cpu(rhead->flags);
+		flags |= CEPH_MDS_FLAG_REPLAY;
+		rhead->flags = cpu_to_le32(flags);
+
+		if (req->r_target_inode)
+			rhead->ino = cpu_to_le64(ceph_ino(req->r_target_inode));
+
+		rhead->num_retry = req->r_attempts - 1;
+
+		/* remove cap/dentry releases from message */
+		rhead->num_releases = 0;
+
+		/* time stamp */
+		p = msg->front.iov_base + req->r_request_release_offset;
+		{
+			struct ceph_timespec ts;
+			ceph_encode_timespec(&ts, &req->r_stamp);
+			ceph_encode_copy(&p, &ts, sizeof(ts));
+		}
+
+		msg->front.iov_len = p - msg->front.iov_base;
+		msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);
+		return 0;
+	}
+
+	if (req->r_request) {
+		ceph_msg_put(req->r_request);
+		req->r_request = NULL;
+	}
+	msg = create_request_message(mdsc, req, mds, drop_cap_releases);
+	if (IS_ERR(msg)) {
+		req->r_err = 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;
+	rhead->ino = 0;
+
+	dout(" r_locked_dir = %p\n", req->r_locked_dir);
+	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_err || req->r_got_result) {
+		if (req->r_aborted)
+			__unregister_request(mdsc, req);
+		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;
+	}
+
+	put_request_session(req);
+
+	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);
+		if (IS_ERR(session)) {
+			err = PTR_ERR(session);
+			goto finish;
+		}
+	}
+	req->r_session = get_session(session);
+
+	dout("do_request mds%d session %p state %s\n", mds, session,
+	     ceph_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_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, false);
+	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_err = 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;
+	LIST_HEAD(tmp_list);
+
+	list_splice_init(head, &tmp_list);
+
+	while (!list_empty(&tmp_list)) {
+		req = list_entry(tmp_list.next,
+				 struct ceph_mds_request, r_wait);
+		list_del_init(&req->r_wait);
+		dout(" wake request %p tid %llu\n", req, req->r_tid);
+		__do_request(mdsc, req);
+	}
+}
+
+/*
+ * Wake up threads with requests pending for @mds, so that they can
+ * resubmit their requests to a possibly different mds.
+ */
+static void kick_requests(struct ceph_mds_client *mdsc, int mds)
+{
+	struct ceph_mds_request *req;
+	struct rb_node *p = rb_first(&mdsc->request_tree);
+
+	dout("kick_requests mds%d\n", mds);
+	while (p) {
+		req = rb_entry(p, struct ceph_mds_request, r_node);
+		p = rb_next(p);
+		if (req->r_got_unsafe)
+			continue;
+		if (req->r_attempts > 0)
+			continue; /* only new requests */
+		if (req->r_session &&
+		    req->r_session->s_mds == mds) {
+			dout(" kicking tid %llu\n", req->r_tid);
+			list_del_init(&req->r_wait);
+			__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_dir)
+		ceph_get_cap_refs(ceph_inode(req->r_old_dentry_dir),
+				  CEPH_CAP_PIN);
+
+	/* issue */
+	mutex_lock(&mdsc->mutex);
+	__register_request(mdsc, req, dir);
+	__do_request(mdsc, req);
+
+	if (req->r_err) {
+		err = req->r_err;
+		__unregister_request(mdsc, req);
+		dout("do_request early error %d\n", err);
+		goto out;
+	}
+
+	/* wait */
+	mutex_unlock(&mdsc->mutex);
+	dout("do_request waiting\n");
+	if (req->r_timeout) {
+		err = (long)wait_for_completion_killable_timeout(
+			&req->r_completion, req->r_timeout);
+		if (err == 0)
+			err = -EIO;
+	} else if (req->r_wait_for_completion) {
+		err = req->r_wait_for_completion(mdsc, req);
+	} else {
+		err = wait_for_completion_killable(&req->r_completion);
+	}
+	dout("do_request waited, got %d\n", err);
+	mutex_lock(&mdsc->mutex);
+
+	/* only abort if we didn't race with a real reply */
+	if (req->r_got_result) {
+		err = le32_to_cpu(req->r_reply_info.head->result);
+	} else if (err < 0) {
+		dout("aborted request %lld with %d\n", req->r_tid, err);
+
+		/*
+		 * ensure we aren't running concurrently with
+		 * ceph_fill_trace or ceph_readdir_prepopulate, which
+		 * rely on locks (dir mutex) held by our caller.
+		 */
+		mutex_lock(&req->r_fill_mutex);
+		req->r_err = err;
+		req->r_aborted = true;
+		mutex_unlock(&req->r_fill_mutex);
+
+		if (req->r_locked_dir &&
+		    (req->r_op & CEPH_MDS_OP_WRITE))
+			ceph_invalidate_dir_request(req);
+	} else {
+		err = req->r_err;
+	}
+
+out:
+	mutex_unlock(&mdsc->mutex);
+	dout("do_request %p done, result %d\n", req, err);
+	return err;
+}
+
+/*
+ * Invalidate dir's completeness, dentry lease state on an aborted MDS
+ * namespace request.
+ */
+void ceph_invalidate_dir_request(struct ceph_mds_request *req)
+{
+	struct inode *inode = req->r_locked_dir;
+
+	dout("invalidate_dir_request %p (complete, lease(s))\n", inode);
+
+	ceph_dir_clear_complete(inode);
+	if (req->r_dentry)
+		ceph_invalidate_dentry_lease(req->r_dentry);
+	if (req->r_old_dentry)
+		ceph_invalidate_dentry_lease(req->r_old_dentry);
+}
+
+/*
+ * 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 */
+	struct ceph_snap_realm *realm;
+	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 != 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_warn("got a dup %s reply on %llu from mds%d\n",
+			   head->safe ? "safe" : "unsafe", tid, mds);
+		mutex_unlock(&mdsc->mutex);
+		goto out;
+	}
+	if (req->r_got_safe && !head->safe) {
+		pr_warn("got unsafe after safe on %llu from mds%d\n",
+			   tid, mds);
+		mutex_unlock(&mdsc->mutex);
+		goto out;
+	}
+
+	result = le32_to_cpu(head->result);
+
+	/*
+	 * Handle an ESTALE
+	 * if we're not talking to the authority, send to them
+	 * if the authority has changed while we weren't looking,
+	 * send to new authority
+	 * Otherwise we just have to return an ESTALE
+	 */
+	if (result == -ESTALE) {
+		dout("got ESTALE on request %llu", req->r_tid);
+		req->r_resend_mds = -1;
+		if (req->r_direct_mode != USE_AUTH_MDS) {
+			dout("not using auth, setting for that now");
+			req->r_direct_mode = USE_AUTH_MDS;
+			__do_request(mdsc, req);
+			mutex_unlock(&mdsc->mutex);
+			goto out;
+		} else  {
+			int mds = __choose_mds(mdsc, req);
+			if (mds >= 0 && mds != req->r_session->s_mds) {
+				dout("but auth changed, so resending");
+				__do_request(mdsc, req);
+				mutex_unlock(&mdsc->mutex);
+				goto out;
+			}
+		}
+		dout("have to return ESTALE on request %llu", req->r_tid);
+	}
+
+
+	if (head->safe) {
+		req->r_got_safe = true;
+		__unregister_request(mdsc, req);
+
+		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_all(&mdsc->safe_umount_waiters);
+			mutex_unlock(&mdsc->mutex);
+			goto out;
+		}
+	} else {
+		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, session->s_con.peer_features);
+	mutex_unlock(&mdsc->mutex);
+
+	mutex_lock(&session->s_mutex);
+	if (err < 0) {
+		pr_err("mdsc_handle_reply got corrupt reply mds%d(tid:%lld)\n", mds, tid);
+		ceph_msg_dump(msg);
+		goto out_err;
+	}
+
+	/* snap trace */
+	realm = NULL;
+	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,
+				&realm);
+		downgrade_write(&mdsc->snap_rwsem);
+	} else {
+		down_read(&mdsc->snap_rwsem);
+	}
+
+	/* insert trace into our cache */
+	mutex_lock(&req->r_fill_mutex);
+	err = ceph_fill_trace(mdsc->fsc->sb, req, req->r_session);
+	if (err == 0) {
+		if (result == 0 && (req->r_op == CEPH_MDS_OP_READDIR ||
+				    req->r_op == CEPH_MDS_OP_LSSNAP))
+			ceph_readdir_prepopulate(req, req->r_session);
+		ceph_unreserve_caps(mdsc, &req->r_caps_reservation);
+	}
+	mutex_unlock(&req->r_fill_mutex);
+
+	up_read(&mdsc->snap_rwsem);
+	if (realm)
+		ceph_put_snap_realm(mdsc, realm);
+out_err:
+	mutex_lock(&mdsc->mutex);
+	if (!req->r_aborted) {
+		if (err) {
+			req->r_err = err;
+		} else {
+			req->r_reply = msg;
+			ceph_msg_get(msg);
+			req->r_got_result = true;
+		}
+	} else {
+		dout("reply arrived after request %lld was aborted\n", tid);
+	}
+	mutex_unlock(&mdsc->mutex);
+
+	ceph_add_cap_releases(mdsc, req->r_session);
+	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 tid %llu to mds%d - req dne\n", tid, next_mds);
+		goto out;  /* dup reply? */
+	}
+
+	if (req->r_aborted) {
+		dout("forward tid %llu aborted, unregistering\n", tid);
+		__unregister_request(mdsc, req);
+	} else if (fwd_seq <= req->r_num_fwd) {
+		dout("forward tid %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 tid %llu to mds%d (we resend)\n", tid, next_mds);
+		BUG_ON(req->r_err);
+		BUG_ON(req->r_got_result);
+		req->r_attempts = 0;
+		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,
+	     ceph_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:
+		if (session->s_state == CEPH_MDS_SESSION_RECONNECTING)
+			pr_info("mds%d reconnect success\n", session->s_mds);
+		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:
+		if (session->s_state == CEPH_MDS_SESSION_RECONNECTING)
+			pr_info("mds%d reconnect denied\n", session->s_mds);
+		cleanup_session_requests(mdsc, session);
+		remove_session_caps(session);
+		wake = 2; /* for good measure */
+		wake_up_all(&mdsc->session_close_wq);
+		break;
+
+	case CEPH_SESSION_STALE:
+		pr_info("mds%d caps went stale, renewing\n",
+			session->s_mds);
+		spin_lock(&session->s_gen_ttl_lock);
+		session->s_cap_gen++;
+		session->s_cap_ttl = jiffies - 1;
+		spin_unlock(&session->s_gen_ttl_lock);
+		send_renew_caps(mdsc, session);
+		break;
+
+	case CEPH_SESSION_RECALL_STATE:
+		trim_caps(mdsc, session, le32_to_cpu(h->max_caps));
+		break;
+
+	case CEPH_SESSION_FLUSHMSG:
+		send_flushmsg_ack(mdsc, session, seq);
+		break;
+
+	case CEPH_SESSION_FORCE_RO:
+		dout("force_session_readonly %p\n", session);
+		spin_lock(&session->s_cap_lock);
+		session->s_readonly = true;
+		spin_unlock(&session->s_cap_lock);
+		wake_up_session_caps(session, 0);
+		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);
+		if (wake == 2)
+			kick_requests(mdsc, mds);
+		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;
+	struct rb_node *p;
+	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, true);
+		if (!err) {
+			ceph_msg_get(req->r_request);
+			ceph_con_send(&session->s_con, req->r_request);
+		}
+	}
+
+	/*
+	 * also re-send old requests when MDS enters reconnect stage. So that MDS
+	 * can process completed request in clientreplay stage.
+	 */
+	p = rb_first(&mdsc->request_tree);
+	while (p) {
+		req = rb_entry(p, struct ceph_mds_request, r_node);
+		p = rb_next(p);
+		if (req->r_got_unsafe)
+			continue;
+		if (req->r_attempts == 0)
+			continue; /* only old requests */
+		if (req->r_session &&
+		    req->r_session->s_mds == session->s_mds) {
+			err = __prepare_send_request(mdsc, req,
+						     session->s_mds, true);
+			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)
+{
+	union {
+		struct ceph_mds_cap_reconnect v2;
+		struct ceph_mds_cap_reconnect_v1 v1;
+	} rec;
+	size_t reclen;
+	struct ceph_inode_info *ci;
+	struct ceph_reconnect_state *recon_state = arg;
+	struct ceph_pagelist *pagelist = recon_state->pagelist;
+	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);
+			goto out_dput;
+		}
+	} else {
+		path = NULL;
+		pathlen = 0;
+	}
+	err = ceph_pagelist_encode_string(pagelist, path, pathlen);
+	if (err)
+		goto out_free;
+
+	spin_lock(&ci->i_ceph_lock);
+	cap->seq = 0;        /* reset cap seq */
+	cap->issue_seq = 0;  /* and issue_seq */
+	cap->mseq = 0;       /* and migrate_seq */
+	cap->cap_gen = cap->session->s_cap_gen;
+
+	if (recon_state->flock) {
+		rec.v2.cap_id = cpu_to_le64(cap->cap_id);
+		rec.v2.wanted = cpu_to_le32(__ceph_caps_wanted(ci));
+		rec.v2.issued = cpu_to_le32(cap->issued);
+		rec.v2.snaprealm = cpu_to_le64(ci->i_snap_realm->ino);
+		rec.v2.pathbase = cpu_to_le64(pathbase);
+		rec.v2.flock_len = 0;
+		reclen = sizeof(rec.v2);
+	} else {
+		rec.v1.cap_id = cpu_to_le64(cap->cap_id);
+		rec.v1.wanted = cpu_to_le32(__ceph_caps_wanted(ci));
+		rec.v1.issued = cpu_to_le32(cap->issued);
+		rec.v1.size = cpu_to_le64(inode->i_size);
+		ceph_encode_timespec(&rec.v1.mtime, &inode->i_mtime);
+		ceph_encode_timespec(&rec.v1.atime, &inode->i_atime);
+		rec.v1.snaprealm = cpu_to_le64(ci->i_snap_realm->ino);
+		rec.v1.pathbase = cpu_to_le64(pathbase);
+		reclen = sizeof(rec.v1);
+	}
+	spin_unlock(&ci->i_ceph_lock);
+
+	if (recon_state->flock) {
+		int num_fcntl_locks, num_flock_locks;
+		struct ceph_filelock *flocks;
+
+encode_again:
+		ceph_count_locks(inode, &num_fcntl_locks, &num_flock_locks);
+		flocks = kmalloc((num_fcntl_locks+num_flock_locks) *
+				 sizeof(struct ceph_filelock), GFP_NOFS);
+		if (!flocks) {
+			err = -ENOMEM;
+			goto out_free;
+		}
+		err = ceph_encode_locks_to_buffer(inode, flocks,
+						  num_fcntl_locks,
+						  num_flock_locks);
+		if (err) {
+			kfree(flocks);
+			if (err == -ENOSPC)
+				goto encode_again;
+			goto out_free;
+		}
+		/*
+		 * number of encoded locks is stable, so copy to pagelist
+		 */
+		rec.v2.flock_len = cpu_to_le32(2*sizeof(u32) +
+				    (num_fcntl_locks+num_flock_locks) *
+				    sizeof(struct ceph_filelock));
+		err = ceph_pagelist_append(pagelist, &rec, reclen);
+		if (!err)
+			err = ceph_locks_to_pagelist(flocks, pagelist,
+						     num_fcntl_locks,
+						     num_flock_locks);
+		kfree(flocks);
+	} else {
+		err = ceph_pagelist_append(pagelist, &rec, reclen);
+	}
+
+	recon_state->nr_caps++;
+out_free:
+	kfree(path);
+out_dput:
+	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,
+			       struct ceph_mds_session *session)
+{
+	struct ceph_msg *reply;
+	struct rb_node *p;
+	int mds = session->s_mds;
+	int err = -ENOMEM;
+	int s_nr_caps;
+	struct ceph_pagelist *pagelist;
+	struct ceph_reconnect_state recon_state;
+
+	pr_info("mds%d reconnect start\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, GFP_NOFS, false);
+	if (!reply)
+		goto fail_nomsg;
+
+	mutex_lock(&session->s_mutex);
+	session->s_state = CEPH_MDS_SESSION_RECONNECTING;
+	session->s_seq = 0;
+
+	dout("session %p state %s\n", session,
+	     ceph_session_state_name(session->s_state));
+
+	spin_lock(&session->s_gen_ttl_lock);
+	session->s_cap_gen++;
+	spin_unlock(&session->s_gen_ttl_lock);
+
+	spin_lock(&session->s_cap_lock);
+	/* don't know if session is readonly */
+	session->s_readonly = 0;
+	/*
+	 * notify __ceph_remove_cap() that we are composing cap reconnect.
+	 * If a cap get released before being added to the cap reconnect,
+	 * __ceph_remove_cap() should skip queuing cap release.
+	 */
+	session->s_cap_reconnect = 1;
+	/* drop old cap expires; we're about to reestablish that state */
+	discard_cap_releases(mdsc, session);
+	spin_unlock(&session->s_cap_lock);
+
+	/* trim unused caps to reduce MDS's cache rejoin time */
+	if (mdsc->fsc->sb->s_root)
+		shrink_dcache_parent(mdsc->fsc->sb->s_root);
+
+	ceph_con_close(&session->s_con);
+	ceph_con_open(&session->s_con,
+		      CEPH_ENTITY_TYPE_MDS, mds,
+		      ceph_mdsmap_get_addr(mdsc->mdsmap, mds));
+
+	/* replay unsafe requests */
+	replay_unsafe_requests(mdsc, session);
+
+	down_read(&mdsc->snap_rwsem);
+
+	/* traverse this session's caps */
+	s_nr_caps = session->s_nr_caps;
+	err = ceph_pagelist_encode_32(pagelist, s_nr_caps);
+	if (err)
+		goto fail;
+
+	recon_state.nr_caps = 0;
+	recon_state.pagelist = pagelist;
+	recon_state.flock = session->s_con.peer_features & CEPH_FEATURE_FLOCK;
+	err = iterate_session_caps(session, encode_caps_cb, &recon_state);
+	if (err < 0)
+		goto fail;
+
+	spin_lock(&session->s_cap_lock);
+	session->s_cap_reconnect = 0;
+	spin_unlock(&session->s_cap_lock);
+
+	/*
+	 * 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;
+	}
+
+	if (recon_state.flock)
+		reply->hdr.version = cpu_to_le16(2);
+
+	/* raced with cap release? */
+	if (s_nr_caps != recon_state.nr_caps) {
+		struct page *page = list_first_entry(&pagelist->head,
+						     struct page, lru);
+		__le32 *addr = kmap_atomic(page);
+		*addr = cpu_to_le32(recon_state.nr_caps);
+		kunmap_atomic(addr);
+	}
+
+	reply->hdr.data_len = cpu_to_le32(pagelist->length);
+	ceph_msg_data_add_pagelist(reply, pagelist);
+	ceph_con_send(&session->s_con, reply);
+
+	mutex_unlock(&session->s_mutex);
+
+	mutex_lock(&mdsc->mutex);
+	__wake_requests(mdsc, &session->s_waiting);
+	mutex_unlock(&mdsc->mutex);
+
+	up_read(&mdsc->snap_rwsem);
+	return;
+
+fail:
+	ceph_msg_put(reply);
+	up_read(&mdsc->snap_rwsem);
+	mutex_unlock(&session->s_mutex);
+fail_nomsg:
+	ceph_pagelist_release(pagelist);
+fail_nopagelist:
+	pr_err("error %d preparing reconnect for mds%d\n", err, mds);
+	return;
+}
+
+
+/*
+ * 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 -> %s%s (session %s)\n",
+		     i, ceph_mds_state_name(oldstate),
+		     ceph_mdsmap_is_laggy(oldmap, i) ? " (laggy)" : "",
+		     ceph_mds_state_name(newstate),
+		     ceph_mdsmap_is_laggy(newmap, i) ? " (laggy)" : "",
+		     ceph_session_state_name(s->s_state));
+
+		if (i >= newmap->m_max_mds ||
+		    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;
+			}
+		} 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) {
+			mutex_unlock(&mdsc->mutex);
+			send_mds_reconnect(mdsc, s);
+			mutex_lock(&mdsc->mutex);
+		}
+
+		/*
+		 * kick request on any mds that has gone active.
+		 */
+		if (oldstate < CEPH_MDS_STATE_ACTIVE &&
+		    newstate >= CEPH_MDS_STATE_ACTIVE) {
+			if (oldstate != CEPH_MDS_STATE_CREATING &&
+			    oldstate != CEPH_MDS_STATE_STARTING)
+				pr_info("mds%d recovery completed\n", s->s_mds);
+			kick_requests(mdsc, i);
+			ceph_kick_flushing_caps(mdsc, s);
+			wake_up_session_caps(s, 1);
+		}
+	}
+
+	for (i = 0; i < newmap->m_max_mds && i < mdsc->max_sessions; i++) {
+		s = mdsc->sessions[i];
+		if (!s)
+			continue;
+		if (!ceph_mdsmap_is_laggy(newmap, i))
+			continue;
+		if (s->s_state == CEPH_MDS_SESSION_OPEN ||
+		    s->s_state == CEPH_MDS_SESSION_HUNG ||
+		    s->s_state == CEPH_MDS_SESSION_CLOSING) {
+			dout(" connecting to export targets of laggy mds%d\n",
+			     i);
+			__open_export_target_sessions(mdsc, s);
+		}
+	}
+}
+
+
+
+/*
+ * 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->fsc->sb;
+	struct inode *inode;
+	struct dentry *parent, *dentry;
+	struct ceph_dentry_info *di;
+	int mds = session->s_mds;
+	struct ceph_mds_lease *h = msg->front.iov_base;
+	u32 seq;
+	struct ceph_vino vino;
+	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;
+	seq = le32_to_cpu(h->seq);
+	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;
+
+	/* lookup inode */
+	inode = ceph_find_inode(sb, vino);
+	dout("handle_lease %s, ino %llx %p %.*s\n",
+	     ceph_lease_op_name(h->action), vino.ino, inode,
+	     dname.len, dname.name);
+
+	mutex_lock(&session->s_mutex);
+	session->s_seq++;
+
+	if (inode == NULL) {
+		dout("handle_lease no inode %llx\n", vino.ino);
+		goto release;
+	}
+
+	/* 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->lease_session == session) {
+			if (ceph_seq_cmp(di->lease_seq, seq) > 0)
+				h->seq = cpu_to_le32(di->lease_seq);
+			__ceph_mdsc_drop_dentry_lease(dentry);
+		}
+		release = 1;
+		break;
+
+	case CEPH_MDS_LEASE_RENEW:
+		if (di->lease_session == session &&
+		    di->lease_gen == session->s_cap_gen &&
+		    di->lease_renew_from &&
+		    di->lease_renew_after == 0) {
+			unsigned long duration =
+				msecs_to_jiffies(le32_to_cpu(h->duration_ms));
+
+			di->lease_seq = 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, GFP_NOFS, false);
+	if (!msg)
+		return;
+	lease = msg->front.iov_base;
+	lease->action = action;
+	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)
+{
+	struct ceph_dentry_info *di;
+	struct ceph_mds_session *session;
+	u32 seq;
+
+	BUG_ON(inode == NULL);
+	BUG_ON(dentry == NULL);
+
+	/* 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\n",
+		     inode, dentry);
+		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 to mds%d\n",
+	     inode, dentry, 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);
+		ceph_add_cap_releases(mdsc, s);
+		if (s->s_state == CEPH_MDS_SESSION_OPEN ||
+		    s->s_state == CEPH_MDS_SESSION_HUNG)
+			ceph_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_fs_client *fsc)
+
+{
+	struct ceph_mds_client *mdsc;
+
+	mdsc = kzalloc(sizeof(struct ceph_mds_client), GFP_NOFS);
+	if (!mdsc)
+		return -ENOMEM;
+	mdsc->fsc = fsc;
+	fsc->mdsc = mdsc;
+	mutex_init(&mdsc->mutex);
+	mdsc->mdsmap = kzalloc(sizeof(*mdsc->mdsmap), GFP_NOFS);
+	if (mdsc->mdsmap == NULL) {
+		kfree(mdsc);
+		return -ENOMEM;
+	}
+
+	init_completion(&mdsc->safe_umount_waiters);
+	init_waitqueue_head(&mdsc->session_close_wq);
+	INIT_LIST_HEAD(&mdsc->waiting_for_map);
+	mdsc->sessions = NULL;
+	atomic_set(&mdsc->num_sessions, 0);
+	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);
+	INIT_LIST_HEAD(&mdsc->cap_dirty_migrating);
+	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);
+
+	ceph_caps_init(mdsc);
+	ceph_adjust_min_caps(mdsc, fsc->min_caps);
+
+	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_fs_client *fsc = mdsc->fsc;
+
+	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,
+				    fsc->client->options->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 reply handlers to drop their request refs and
+	 * their inode/dcache refs
+	 */
+	ceph_msgr_flush();
+}
+
+/*
+ * 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, *nextreq;
+	struct rb_node *n;
+
+	mutex_lock(&mdsc->mutex);
+	dout("wait_unsafe_requests want %lld\n", want_tid);
+restart:
+	req = __get_oldest_req(mdsc);
+	while (req && req->r_tid <= want_tid) {
+		/* find next request */
+		n = rb_next(&req->r_node);
+		if (n)
+			nextreq = rb_entry(n, struct ceph_mds_request, r_node);
+		else
+			nextreq = NULL;
+		if ((req->r_op & CEPH_MDS_OP_WRITE)) {
+			/* write op */
+			ceph_mdsc_get_request(req);
+			if (nextreq)
+				ceph_mdsc_get_request(nextreq);
+			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);
+			ceph_mdsc_put_request(req);
+			if (!nextreq)
+				break;  /* next dne before, so we're done! */
+			if (RB_EMPTY_NODE(&nextreq->r_node)) {
+				/* next request was removed from tree */
+				ceph_mdsc_put_request(nextreq);
+				goto restart;
+			}
+			ceph_mdsc_put_request(nextreq);  /* won't go away */
+		}
+		req = nextreq;
+	}
+	mutex_unlock(&mdsc->mutex);
+	dout("wait_unsafe_requests done\n");
+}
+
+void ceph_mdsc_sync(struct ceph_mds_client *mdsc)
+{
+	u64 want_tid, want_flush;
+
+	if (mdsc->fsc->mount_state == CEPH_MOUNT_SHUTDOWN)
+		return;
+
+	dout("sync\n");
+	mutex_lock(&mdsc->mutex);
+	want_tid = mdsc->last_tid;
+	mutex_unlock(&mdsc->mutex);
+
+	ceph_flush_dirty_caps(mdsc);
+	spin_lock(&mdsc->cap_dirty_lock);
+	want_flush = mdsc->cap_flush_seq;
+	spin_unlock(&mdsc->cap_dirty_lock);
+
+	dout("sync want tid %lld flush_seq %lld\n", want_tid, want_flush);
+
+	wait_unsafe_requests(mdsc, want_tid);
+	wait_caps_flush(mdsc, want_flush);
+}
+
+/*
+ * true if all sessions are closed, or we force unmount
+ */
+static bool done_closing_sessions(struct ceph_mds_client *mdsc)
+{
+	if (mdsc->fsc->mount_state == CEPH_MOUNT_SHUTDOWN)
+		return true;
+	return atomic_read(&mdsc->num_sessions) == 0;
+}
+
+/*
+ * called after sb is ro.
+ */
+void ceph_mdsc_close_sessions(struct ceph_mds_client *mdsc)
+{
+	struct ceph_mds_session *session;
+	int i;
+	struct ceph_fs_client *fsc = mdsc->fsc;
+	unsigned long timeout = fsc->client->options->mount_timeout * HZ;
+
+	dout("close_sessions\n");
+
+	/* close sessions */
+	mutex_lock(&mdsc->mutex);
+	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);
+	}
+	mutex_unlock(&mdsc->mutex);
+
+	dout("waiting for sessions to close\n");
+	wait_event_timeout(mdsc->session_close_wq, done_closing_sessions(mdsc),
+			   timeout);
+
+	/* tear down remaining sessions */
+	mutex_lock(&mdsc->mutex);
+	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");
+}
+
+static 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);
+	ceph_caps_finalize(mdsc);
+}
+
+void ceph_mdsc_destroy(struct ceph_fs_client *fsc)
+{
+	struct ceph_mds_client *mdsc = fsc->mdsc;
+
+	dout("mdsc_destroy %p\n", mdsc);
+	ceph_mdsc_stop(mdsc);
+
+	/* flush out any connection work with references to us */
+	ceph_msgr_flush();
+
+	fsc->mdsc = NULL;
+	kfree(mdsc);
+	dout("mdsc_destroy %p done\n", mdsc);
+}
+
+
+/*
+ * 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->fsc->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->fsc->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->fsc->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;
+
+	dout("mdsc con_put %p (%d)\n", s, atomic_read(&s->s_ref) - 1);
+	ceph_put_mds_session(s);
+}
+
+/*
+ * 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;
+	struct ceph_mds_client *mdsc = s->s_mdsc;
+
+	pr_warn("mds%d closed our session\n", s->s_mds);
+	send_mds_reconnect(mdsc, s);
+}
+
+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
+ */
+
+/*
+ * Note: returned pointer is the address of a structure that's
+ * managed separately.  Caller must *not* attempt to free it.
+ */
+static struct ceph_auth_handshake *get_authorizer(struct ceph_connection *con,
+					int *proto, int force_new)
+{
+	struct ceph_mds_session *s = con->private;
+	struct ceph_mds_client *mdsc = s->s_mdsc;
+	struct ceph_auth_client *ac = mdsc->fsc->client->monc.auth;
+	struct ceph_auth_handshake *auth = &s->s_auth;
+
+	if (force_new && auth->authorizer) {
+		ceph_auth_destroy_authorizer(ac, auth->authorizer);
+		auth->authorizer = NULL;
+	}
+	if (!auth->authorizer) {
+		int ret = ceph_auth_create_authorizer(ac, CEPH_ENTITY_TYPE_MDS,
+						      auth);
+		if (ret)
+			return ERR_PTR(ret);
+	} else {
+		int ret = ceph_auth_update_authorizer(ac, CEPH_ENTITY_TYPE_MDS,
+						      auth);
+		if (ret)
+			return ERR_PTR(ret);
+	}
+	*proto = ac->protocol;
+
+	return auth;
+}
+
+
+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->fsc->client->monc.auth;
+
+	return ceph_auth_verify_authorizer_reply(ac, s->s_auth.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->fsc->client->monc.auth;
+
+	ceph_auth_invalidate_authorizer(ac, CEPH_ENTITY_TYPE_MDS);
+
+	return ceph_monc_validate_auth(&mdsc->fsc->client->monc);
+}
+
+static struct ceph_msg *mds_alloc_msg(struct ceph_connection *con,
+				struct ceph_msg_header *hdr, int *skip)
+{
+	struct ceph_msg *msg;
+	int type = (int) le16_to_cpu(hdr->type);
+	int front_len = (int) le32_to_cpu(hdr->front_len);
+
+	if (con->in_msg)
+		return con->in_msg;
+
+	*skip = 0;
+	msg = ceph_msg_new(type, front_len, GFP_NOFS, false);
+	if (!msg) {
+		pr_err("unable to allocate msg type %d len %d\n",
+		       type, front_len);
+		return NULL;
+	}
+
+	return msg;
+}
+
+static int sign_message(struct ceph_connection *con, struct ceph_msg *msg)
+{
+       struct ceph_mds_session *s = con->private;
+       struct ceph_auth_handshake *auth = &s->s_auth;
+       return ceph_auth_sign_message(auth, msg);
+}
+
+static int check_message_signature(struct ceph_connection *con, struct ceph_msg *msg)
+{
+       struct ceph_mds_session *s = con->private;
+       struct ceph_auth_handshake *auth = &s->s_auth;
+       return ceph_auth_check_message_signature(auth, msg);
+}
+
+static const 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,
+	.alloc_msg = mds_alloc_msg,
+	.sign_message = sign_message,
+	.check_message_signature = check_message_signature,
+};
+
+/* eof */