#include <linux/ceph/ceph_debug.h>

  #include <linux/fs.h>

  #include <linux/wait.h>

  #include <linux/slab.h>

  #include <linux/sched.h>

  #include <linux/debugfs.h>
  #include <linux/seq_file.h>

  #include "super.h"

  #include "mds_client.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   * are no longer valid.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 {
  	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,
  			       int 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;
  	return 0;
  bad:
  	return err;
  }
  
  /*
   * parse a normal reply, which may contain a (dir+)dentry and/or a
   * target inode.
   */
  static int parse_reply_info_trace(void **p, void *end,

  				  struct ceph_mds_reply_info_parsed *info,
  				  int 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
  ", err);
  	return err;
  }
  
  /*
   * parse readdir results
   */
  static int parse_reply_info_dir(void **p, void *end,

  				struct ceph_mds_reply_info_parsed *info,
  				int 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;
  
  	/* alloc large array */
  	info->dir_nr = num;
  	info->dir_in = kcalloc(num, sizeof(*info->dir_in) +
  			       sizeof(*info->dir_dname) +
  			       sizeof(*info->dir_dname_len) +
  			       sizeof(*info->dir_dlease),
  			       GFP_NOFS);
  	if (info->dir_in == NULL) {
  		err = -ENOMEM;
  		goto out_bad;
  	}
  	info->dir_dname = (void *)(info->dir_in + num);
  	info->dir_dname_len = (void *)(info->dir_dname + num);
  	info->dir_dlease = (void *)(info->dir_dname_len + num);
  
  	while (num) {
  		/* dentry */
  		ceph_decode_need(p, end, sizeof(u32)*2, bad);

  		info->dir_dname_len[i] = ceph_decode_32(p);

  		ceph_decode_need(p, end, info->dir_dname_len[i], bad);
  		info->dir_dname[i] = *p;
  		*p += info->dir_dname_len[i];
  		dout("parsed dir dname '%.*s'
  ", 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
  ", 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,
  				     int 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 extra results
   */
  static int parse_reply_info_extra(void **p, void *end,

  				  struct ceph_mds_reply_info_parsed *info,
  				  int features)

  {
  	if (info->head->op == CEPH_MDS_OP_GETFILELOCK)

  		return parse_reply_info_filelock(p, end, info, features);

  	else

  		return parse_reply_info_dir(p, end, info, features);

  }
  
  /*

   * parse entire mds reply
   */
  static int parse_reply_info(struct ceph_msg *msg,

  			    struct ceph_mds_reply_info_parsed *info,
  			    int 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) {

  		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) {

  		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
  ", err);
  	return err;
  }
  
  static void destroy_reply_info(struct ceph_mds_reply_info_parsed *info)
  {
  	kfree(info->dir_in);
  }
  
  
  /*
   * sessions
   */
  static const char *session_state_name(int s)
  {
  	switch (s) {
  	case CEPH_MDS_SESSION_NEW: return "new";
  	case CEPH_MDS_SESSION_OPENING: return "opening";
  	case CEPH_MDS_SESSION_OPEN: return "open";
  	case CEPH_MDS_SESSION_HUNG: return "hung";
  	case CEPH_MDS_SESSION_CLOSING: return "closing";

  	case CEPH_MDS_SESSION_RESTARTING: return "restarting";

  	case CEPH_MDS_SESSION_RECONNECTING: return "reconnecting";
  	default: return "???";
  	}
  }
  
  static struct ceph_mds_session *get_session(struct ceph_mds_session *s)
  {
  	if (atomic_inc_not_zero(&s->s_ref)) {
  		dout("mdsc get_session %p %d -> %d
  ", 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
  ", s,
  	     atomic_read(&s->s_ref), atomic_read(&s->s_ref)-1);

  	if (atomic_dec_and_test(&s->s_ref)) {
  		if (s->s_authorizer)

  		     s->s_mdsc->fsc->client->monc.auth->ops->destroy_authorizer(
  			     s->s_mdsc->fsc->client->monc.auth,
  			     s->s_authorizer);

  		kfree(s);

  	}

  }
  
  /*
   * called under mdsc->mutex
   */
  struct ceph_mds_session *__ceph_lookup_mds_session(struct ceph_mds_client *mdsc,
  						   int mds)
  {
  	struct ceph_mds_session *session;
  
  	if (mds >= mdsc->max_sessions || mdsc->sessions[mds] == NULL)
  		return NULL;
  	session = mdsc->sessions[mds];
  	dout("lookup_mds_session %p %d
  ", session,
  	     atomic_read(&session->s_ref));
  	get_session(session);
  	return session;
  }
  
  static bool __have_session(struct ceph_mds_client *mdsc, int mds)
  {
  	if (mds >= mdsc->max_sessions)
  		return false;
  	return mdsc->sessions[mds];
  }

  static int __verify_registered_session(struct ceph_mds_client *mdsc,
  				       struct ceph_mds_session *s)
  {
  	if (s->s_mds >= mdsc->max_sessions ||
  	    mdsc->sessions[s->s_mds] != s)
  		return -ENOENT;
  	return 0;
  }

  /*
   * create+register a new session for given mds.
   * called under mdsc->mutex.
   */
  static struct ceph_mds_session *register_session(struct ceph_mds_client *mdsc,
  						 int mds)
  {
  	struct ceph_mds_session *s;
  
  	s = kzalloc(sizeof(*s), GFP_NOFS);

  	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(mdsc->fsc->client->msgr, &s->s_con);

  	s->s_con.private = s;
  	s->s_con.ops = &mds_con_ops;
  	s->s_con.peer_name.type = CEPH_ENTITY_TYPE_MDS;
  	s->s_con.peer_name.num = cpu_to_le64(mds);

  
  	spin_lock_init(&s->s_cap_lock);
  	s->s_cap_gen = 0;
  	s->s_cap_ttl = 0;
  	s->s_renew_requested = 0;
  	s->s_renew_seq = 0;
  	INIT_LIST_HEAD(&s->s_caps);
  	s->s_nr_caps = 0;

  	s->s_trim_caps = 0;

  	atomic_set(&s->s_ref, 1);
  	INIT_LIST_HEAD(&s->s_waiting);
  	INIT_LIST_HEAD(&s->s_unsafe);
  	s->s_num_cap_releases = 0;

  	s->s_cap_iterator = NULL;

  	INIT_LIST_HEAD(&s->s_cap_releases);
  	INIT_LIST_HEAD(&s->s_cap_releases_done);
  	INIT_LIST_HEAD(&s->s_cap_flushing);
  	INIT_LIST_HEAD(&s->s_cap_snaps_flushing);
  
  	dout("register_session mds%d
  ", 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
  ", newmax);
  		sa = kcalloc(newmax, sizeof(void *), GFP_NOFS);
  		if (sa == NULL)

  			goto fail_realloc;

  		if (mdsc->sessions) {
  			memcpy(sa, mdsc->sessions,
  			       mdsc->max_sessions * sizeof(void *));
  			kfree(mdsc->sessions);
  		}
  		mdsc->sessions = sa;
  		mdsc->max_sessions = newmax;
  	}
  	mdsc->sessions[mds] = s;
  	atomic_inc(&s->s_ref);  /* one ref to sessions[], one to caller */

  
  	ceph_con_open(&s->s_con, ceph_mdsmap_get_addr(mdsc->mdsmap, mds));

  	return s;

  
  fail_realloc:
  	kfree(s);
  	return ERR_PTR(-ENOMEM);

  }
  
  /*
   * called under mdsc->mutex
   */

  static void __unregister_session(struct ceph_mds_client *mdsc,

  			       struct ceph_mds_session *s)

  {

  	dout("__unregister_session mds%d %p
  ", s->s_mds, s);
  	BUG_ON(mdsc->sessions[s->s_mds] != s);

  	mdsc->sessions[s->s_mds] = NULL;
  	ceph_con_close(&s->s_con);
  	ceph_put_mds_session(s);

  }
  
  /*
   * drop session refs in request.
   *
   * should be last request ref, or hold mdsc->mutex
   */
  static void put_request_session(struct ceph_mds_request *req)
  {
  	if (req->r_session) {
  		ceph_put_mds_session(req->r_session);
  		req->r_session = NULL;
  	}
  }

  void ceph_mdsc_release_request(struct kref *kref)

  {

  	struct ceph_mds_request *req = container_of(kref,
  						    struct ceph_mds_request,
  						    r_kref);
  	if (req->r_request)
  		ceph_msg_put(req->r_request);
  	if (req->r_reply) {
  		ceph_msg_put(req->r_reply);
  		destroy_reply_info(&req->r_reply_info);
  	}
  	if (req->r_inode) {

  		ceph_put_cap_refs(ceph_inode(req->r_inode), CEPH_CAP_PIN);

  		iput(req->r_inode);
  	}
  	if (req->r_locked_dir)

  		ceph_put_cap_refs(ceph_inode(req->r_locked_dir), CEPH_CAP_PIN);

  	if (req->r_target_inode)
  		iput(req->r_target_inode);
  	if (req->r_dentry)
  		dput(req->r_dentry);
  	if (req->r_old_dentry) {

  		/*
  		 * 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);

  		dput(req->r_old_dentry);

  		iput(req->r_old_dentry_dir);

  	}

  	kfree(req->r_path1);
  	kfree(req->r_path2);
  	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
  ", 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
  ", 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;

  	}

  
  	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(dentry->d_inode) != 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
  ",
  		     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 = parent->d_inode;

  		if (dir->i_sb != mdsc->fsc->sb) {

  			/* not this fs! */
  			inode = req->r_dentry->d_inode;
  		} 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 = dn->d_inode;
  			dout("__choose_mds using nonsnap parent %p
  ", inode);
  		} else if (req->r_dentry->d_inode) {
  			/* dentry target */

  			inode = req->r_dentry->d_inode;
  		} else {

  			/* 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
  ", 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)
  ",
  				     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)
  ",
  				     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)
  ",
  	     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
  ", 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
  ");

  		return NULL;

  	}
  	h = msg->front.iov_base;
  	h->op = cpu_to_le32(op);
  	h->seq = cpu_to_le64(seq);
  	return msg;
  }
  
  /*
   * send session open request.
   *
   * called under mdsc->mutex
   */
  static int __open_session(struct ceph_mds_client *mdsc,
  			  struct ceph_mds_session *session)
  {
  	struct ceph_msg *msg;
  	int mstate;
  	int mds = session->s_mds;

  
  	/* wait for mds to go active? */
  	mstate = ceph_mdsmap_get_state(mdsc->mdsmap, mds);
  	dout("open_session to mds%d (%s)
  ", mds,
  	     ceph_mds_state_name(mstate));
  	session->s_state = CEPH_MDS_SESSION_OPENING;
  	session->s_renew_requested = jiffies;
  
  	/* send connect message */
  	msg = create_session_msg(CEPH_SESSION_REQUEST_OPEN, session->s_seq);

  	if (!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 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;
  	int target;
  
  	if (mds >= mdsc->mdsmap->m_max_mds)
  		return;
  	mi = &mdsc->mdsmap->m_info[mds];
  	dout("open_export_target_sessions for mds%d (%d targets)
  ",
  	     session->s_mds, mi->num_export_targets);
  
  	for (i = 0; i < mi->num_export_targets; i++) {
  		target = mi->export_targets[i];
  		ts = __ceph_lookup_mds_session(mdsc, target);
  		if (!ts) {
  			ts = register_session(mdsc, target);
  			if (IS_ERR(ts))
  				return;
  		}
  		if (session->s_state == CEPH_MDS_SESSION_NEW ||
  		    session->s_state == CEPH_MDS_SESSION_CLOSING)
  			__open_session(mdsc, session);
  		else
  			dout(" mds%d target mds%d %p is %s
  ", session->s_mds,
  			     i, ts, session_state_name(ts->s_state));
  		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);
  }
  
  /*

   * 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
  ", 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
  ",
  			     cap);
  			BUG_ON(cap->session != session);
  			list_del_init(&cap->session_caps);
  			session->s_nr_caps--;
  			cap->session = NULL;
  			old_cap = cap;  /* put_cap it w/o locks held */
  		}

  		if (ret < 0)
  			goto out;

  	}

  	ret = 0;
  out:

  	session->s_cap_iterator = NULL;

  	spin_unlock(&session->s_cap_lock);

  
  	if (last_inode)
  		iput(last_inode);
  	if (old_cap)

  		ceph_put_cap(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
  ",
  	     cap, ci, &ci->vfs_inode);

  	spin_lock(&ci->i_ceph_lock);

  	__ceph_remove_cap(cap);
  	if (!__ceph_is_any_real_caps(ci)) {
  		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
  ",
  				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
  ",
  				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;
  		}
  		if (drop && ci->i_wrbuffer_ref) {
  			pr_info(" dropping dirty data for %p %lld
  ",
  				inode, ceph_ino(inode));
  			ci->i_wrbuffer_ref = 0;
  			ci->i_wrbuffer_ref_head = 0;
  			drop++;
  		}
  		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
  ", session);
  	iterate_session_caps(session, remove_session_caps_cb, NULL);
  	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
  ", 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
  ", 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)
  ",
  		     session->s_mds, ceph_mds_state_name(state));
  		return 0;
  	}
  
  	dout("send_renew_caps to mds%d (%s)
  ", 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;
  }
  
  /*
   * Note new cap ttl, and any transition from stale -> not stale (fresh?).

   *
   * Called under session->s_mutex

   */
  static void renewed_caps(struct ceph_mds_client *mdsc,
  			 struct ceph_mds_session *session, int is_renew)
  {
  	int was_stale;
  	int wake = 0;
  
  	spin_lock(&session->s_cap_lock);
  	was_stale = is_renew && (session->s_cap_ttl == 0 ||
  				 time_after_eq(jiffies, session->s_cap_ttl));
  
  	session->s_cap_ttl = session->s_renew_requested +
  		mdsc->mdsmap->m_session_timeout*HZ;
  
  	if (was_stale) {
  		if (time_before(jiffies, session->s_cap_ttl)) {
  			pr_info("mds%d caps renewed
  ", session->s_mds);
  			wake = 1;
  		} else {
  			pr_info("mds%d caps still stale
  ", session->s_mds);
  		}
  	}
  	dout("renewed_caps mds%d ttl now %lu, was %s, now %s
  ",
  	     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
  ",
  	     session->s_mds, 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, 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);
  	oissued = __ceph_caps_issued_other(ci, cap);
  
  	dout("trim_caps_cb %p cap %p mine %s oissued %s used %s
  ",
  	     inode, cap, ceph_cap_string(mine), ceph_cap_string(oissued),
  	     ceph_cap_string(used));
  	if (ci->i_dirty_caps)
  		goto out;   /* dirty caps */
  	if ((used & ~oissued) & mine)
  		goto out;   /* we need these caps */
  
  	session->s_trim_caps--;
  	if (oissued) {
  		/* we aren't the only cap.. just remove us */

  		__ceph_remove_cap(cap);

  	} else {
  		/* try to drop referring dentries */

  		spin_unlock(&ci->i_ceph_lock);

  		d_prune_aliases(inode);
  		dout("trim_caps_cb %p cap %p  pruned, count now %d
  ",
  		     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
  ",
  	     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
  ",
  		     session->s_mds, session->s_nr_caps, max_caps,
  			trim_caps - session->s_trim_caps);

  		session->s_trim_caps = 0;

  	}
  	return 0;
  }
  
  /*
   * Allocate cap_release messages.  If there is a partially full message
   * in the queue, try to allocate enough to cover it's remainder, so that
   * we can send it immediately.
   *
   * Called under s_mutex.
   */

  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
  ", 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)
  ", 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
  ", 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
  ", 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;
  }
  
  /*
   * flush all dirty inode data to disk.
   *
   * returns true if we've flushed through want_flush_seq
   */
  static int check_cap_flush(struct ceph_mds_client *mdsc, u64 want_flush_seq)
  {
  	int mds, ret = 1;
  
  	dout("check_cap_flush want %lld
  ", want_flush_seq);
  	mutex_lock(&mdsc->mutex);
  	for (mds = 0; ret && mds < mdsc->max_sessions; mds++) {
  		struct ceph_mds_session *session = mdsc->sessions[mds];
  
  		if (!session)
  			continue;
  		get_session(session);
  		mutex_unlock(&mdsc->mutex);
  
  		mutex_lock(&session->s_mutex);
  		if (!list_empty(&session->s_cap_flushing)) {
  			struct ceph_inode_info *ci =
  				list_entry(session->s_cap_flushing.next,
  					   struct ceph_inode_info,
  					   i_flushing_item);
  			struct inode *inode = &ci->vfs_inode;

  			spin_lock(&ci->i_ceph_lock);

  			if (ci->i_cap_flush_seq <= want_flush_seq) {
  				dout("check_cap_flush still flushing %p "
  				     "seq %lld <= %lld to mds%d
  ", inode,
  				     ci->i_cap_flush_seq, want_flush_seq,
  				     session->s_mds);
  				ret = 0;
  			}

  			spin_unlock(&ci->i_ceph_lock);

  		}
  		mutex_unlock(&session->s_mutex);
  		ceph_put_mds_session(session);
  
  		if (!ret)
  			return ret;
  		mutex_lock(&mdsc->mutex);
  	}
  
  	mutex_unlock(&mdsc->mutex);
  	dout("check_cap_flush ok, flushed thru %lld
  ", want_flush_seq);
  	return ret;
  }
  
  /*
   * 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
  ", 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
  ", 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
  ", session->s_mds);
  	spin_lock(&session->s_cap_lock);
  
  	/* 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
  ", session->s_mds, msg, num);
  	head->num = cpu_to_le32(0);
  	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
  ", 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);
  	}
  
  	spin_unlock(&session->s_cap_lock);
  }

  /*
   * requests
   */
  
  /*
   * Create an mds request.
   */
  struct ceph_mds_request *
  ceph_mdsc_create_request(struct ceph_mds_client *mdsc, int op, int mode)
  {
  	struct ceph_mds_request *req = kzalloc(sizeof(*req), GFP_NOFS);
  
  	if (!req)
  		return ERR_PTR(-ENOMEM);

  	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_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 = temp->d_inode;
  		if (inode && ceph_snap(inode) == CEPH_SNAPDIR)
  			len++;  /* slash only */
  		else if (stop_on_nosnap && inode &&
  			 ceph_snap(inode) == CEPH_NOSNAP)
  			break;
  		else
  			len += 1 + temp->d_name.len;
  		temp = temp->d_parent;
  		if (temp == NULL) {

  			rcu_read_unlock();

  			pr_err("build_path corrupt dentry %p
  ", dentry);

  			return ERR_PTR(-EINVAL);
  		}
  	}

  	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 = temp->d_inode;

  		if (inode && ceph_snap(inode) == CEPH_SNAPDIR) {

  			dout("build_path path+%d: %p SNAPDIR
  ",

  			     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;
  		if (temp == NULL) {

  			rcu_read_unlock();

  			pr_err("build_path corrupt dentry
  ");

  			kfree(path);
  			return ERR_PTR(-EINVAL);
  		}
  	}

  	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
  ", len, pos);
  		/* presumably this is only possible if racing with a
  		   rename of one of the parent directories (we can not
  		   lock the dentries above us to prevent this, but
  		   retrying should be harmless) */
  		kfree(path);
  		goto retry;
  	}
  
  	*base = ceph_ino(temp->d_inode);
  	*plen = len;

  	dout("build_path on %p %d built %llx '%.*s'
  ",

  	     dentry, dentry->d_count, *base, len, path);

  	return path;
  }
  
  static int build_dentry_path(struct dentry *dentry,
  			     const char **ppath, int *ppathlen, u64 *pino,
  			     int *pfreepath)
  {
  	char *path;
  
  	if (ceph_snap(dentry->d_parent->d_inode) == CEPH_NOSNAP) {
  		*pino = ceph_ino(dentry->d_parent->d_inode);
  		*ppath = dentry->d_name.name;
  		*ppathlen = dentry->d_name.len;
  		return 0;
  	}
  	path = ceph_mdsc_build_path(dentry, ppathlen, pino, 1);
  	if (IS_ERR(path))
  		return PTR_ERR(path);
  	*ppath = path;
  	*pfreepath = 1;
  	return 0;
  }
  
  static int build_inode_path(struct inode *inode,
  			    const char **ppath, int *ppathlen, u64 *pino,
  			    int *pfreepath)
  {
  	struct dentry *dentry;
  	char *path;
  
  	if (ceph_snap(inode) == CEPH_NOSNAP) {
  		*pino = ceph_ino(inode);
  		*ppathlen = 0;
  		return 0;
  	}
  	dentry = d_find_alias(inode);
  	path = ceph_mdsc_build_path(dentry, ppathlen, pino, 1);
  	dput(dentry);
  	if (IS_ERR(path))
  		return PTR_ERR(path);
  	*ppath = path;
  	*pfreepath = 1;
  	return 0;
  }
  
  /*
   * request arguments may be specified via an inode *, a dentry *, or
   * an explicit ino+path.
   */
  static int set_request_path_attr(struct inode *rinode, struct dentry *rdentry,
  				  const char *rpath, u64 rino,
  				  const char **ppath, int *pathlen,
  				  u64 *ino, int *freepath)
  {
  	int r = 0;
  
  	if (rinode) {
  		r = build_inode_path(rinode, ppath, pathlen, ino, freepath);
  		dout(" inode %p %llx.%llx
  ", rinode, ceph_ino(rinode),
  		     ceph_snap(rinode));
  	} else if (rdentry) {
  		r = build_dentry_path(rdentry, ppath, pathlen, ino, freepath);
  		dout(" dentry %p %llx/%.*s
  ", rdentry, *ino, *pathlen,
  		     *ppath);

  	} else if (rpath || rino) {

  		*ino = rino;
  		*ppath = rpath;
  		*pathlen = strlen(rpath);
  		dout(" path %.*s
  ", *pathlen, rpath);
  	}
  
  	return r;
  }
  
  /*
   * called under mdsc->mutex
   */
  static struct ceph_msg *create_request_message(struct ceph_mds_client *mdsc,
  					       struct ceph_mds_request *req,
  					       int mds)
  {
  	struct ceph_msg *msg;
  	struct ceph_mds_request_head *head;
  	const char *path1 = NULL;
  	const char *path2 = NULL;
  	u64 ino1 = 0, ino2 = 0;
  	int pathlen1 = 0, pathlen2 = 0;
  	int freepath1 = 0, freepath2 = 0;
  	int len;
  	u16 releases;
  	void *p, *end;
  	int ret;
  
  	ret = set_request_path_attr(req->r_inode, req->r_dentry,
  			      req->r_path1, req->r_ino1.ino,
  			      &path1, &pathlen1, &ino1, &freepath1);
  	if (ret < 0) {
  		msg = ERR_PTR(ret);
  		goto out;
  	}
  
  	ret = set_request_path_attr(NULL, req->r_old_dentry,
  			      req->r_path2, req->r_ino2.ino,
  			      &path2, &pathlen2, &ino2, &freepath2);
  	if (ret < 0) {
  		msg = ERR_PTR(ret);
  		goto out_free1;
  	}
  
  	len = sizeof(*head) +

  		pathlen1 + pathlen2 + 2*(1 + sizeof(u32) + sizeof(u64));

  
  	/* calculate (max) length for cap releases */
  	len += sizeof(struct ceph_mds_request_release) *
  		(!!req->r_inode_drop + !!req->r_dentry_drop +
  		 !!req->r_old_inode_drop + !!req->r_old_dentry_drop);
  	if (req->r_dentry_drop)
  		len += req->r_dentry->d_name.len;
  	if (req->r_old_dentry_drop)
  		len += req->r_old_dentry->d_name.len;

  	msg = ceph_msg_new(CEPH_MSG_CLIENT_REQUEST, len, GFP_NOFS, false);

  	if (!msg) {
  		msg = ERR_PTR(-ENOMEM);

  		goto out_free2;

  	}

  	msg->hdr.tid = cpu_to_le64(req->r_tid);

  	head = msg->front.iov_base;
  	p = msg->front.iov_base + sizeof(*head);
  	end = msg->front.iov_base + msg->front.iov_len;
  
  	head->mdsmap_epoch = cpu_to_le32(mdsc->mdsmap->m_epoch);
  	head->op = cpu_to_le32(req->r_op);

  	head->caller_uid = cpu_to_le32(req->r_uid);
  	head->caller_gid = cpu_to_le32(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 : req->r_dentry->d_inode,
  		      mds, req->r_inode_drop, req->r_inode_unless, 0);
  	if (req->r_dentry_drop)
  		releases += ceph_encode_dentry_release(&p, req->r_dentry,
  		       mds, req->r_dentry_drop, req->r_dentry_unless);
  	if (req->r_old_dentry_drop)
  		releases += ceph_encode_dentry_release(&p, req->r_old_dentry,
  		       mds, req->r_old_dentry_drop, req->r_old_dentry_unless);
  	if (req->r_old_inode_drop)
  		releases += ceph_encode_inode_release(&p,
  		      req->r_old_dentry->d_inode,
  		      mds, req->r_old_inode_drop, req->r_old_inode_unless, 0);
  	head->num_releases = cpu_to_le16(releases);
  
  	BUG_ON(p > end);
  	msg->front.iov_len = p - msg->front.iov_base;
  	msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);
  
  	msg->pages = req->r_pages;
  	msg->nr_pages = req->r_num_pages;
  	msg->hdr.data_len = cpu_to_le32(req->r_data_len);
  	msg->hdr.data_off = cpu_to_le16(0);
  
  out_free2:
  	if (freepath2)
  		kfree((char *)path2);
  out_free1:
  	if (freepath1)
  		kfree((char *)path1);
  out:
  	return msg;
  }
  
  /*
   * called under mdsc->mutex if error, under no mutex if
   * success.
   */
  static void complete_request(struct ceph_mds_client *mdsc,
  			     struct ceph_mds_request *req)
  {
  	if (req->r_callback)
  		req->r_callback(mdsc, req);
  	else

  		complete_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)
  {
  	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)
  ", req,
  	     req->r_tid, ceph_mds_op_name(req->r_op), req->r_attempts);

  	if (req->r_got_unsafe) {
  		/*
  		 * 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;
  		msg->hdr.front_len = cpu_to_le32(req->r_request_release_offset);
  		msg->front.iov_len = req->r_request_release_offset;

  		return 0;
  	}

  	if (req->r_request) {
  		ceph_msg_put(req->r_request);
  		req->r_request = NULL;
  	}
  	msg = create_request_message(mdsc, req, mds);
  	if (IS_ERR(msg)) {

  		req->r_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
  ", 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)

  		goto out;
  
  	if (req->r_timeout &&
  	    time_after_eq(jiffies, req->r_started + req->r_timeout)) {
  		dout("do_request timed out
  ");
  		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
  ");
  		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
  ", mds, session,
  	     session_state_name(session->s_state));
  	if (session->s_state != CEPH_MDS_SESSION_OPEN &&
  	    session->s_state != CEPH_MDS_SESSION_HUNG) {
  		if (session->s_state == CEPH_MDS_SESSION_NEW ||
  		    session->s_state == CEPH_MDS_SESSION_CLOSING)
  			__open_session(mdsc, session);
  		list_add(&req->r_wait, &session->s_waiting);
  		goto out_session;
  	}
  
  	/* send request */

  	req->r_resend_mds = -1;   /* forget any previous mds hint */
  
  	if (req->r_request_started == 0)   /* note request start time */
  		req->r_request_started = jiffies;
  
  	err = __prepare_send_request(mdsc, req, mds);
  	if (!err) {
  		ceph_msg_get(req->r_request);
  		ceph_con_send(&session->s_con, req->r_request);
  	}
  
  out_session:
  	ceph_put_mds_session(session);
  out:
  	return err;
  
  finish:

  	req->r_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, *nreq;
  
  	list_for_each_entry_safe(req, nreq, head, r_wait) {
  		list_del_init(&req->r_wait);
  		__do_request(mdsc, req);
  	}
  }
  
  /*
   * Wake up threads with requests pending for @mds, so that they can

   * resubmit their requests to a possibly different mds.

   */

  static void kick_requests(struct ceph_mds_client *mdsc, int mds)

  {

  	struct ceph_mds_request *req;
  	struct rb_node *p;

  
  	dout("kick_requests mds%d
  ", mds);

  	for (p = rb_first(&mdsc->request_tree); p; p = rb_next(p)) {
  		req = rb_entry(p, struct ceph_mds_request, r_node);
  		if (req->r_got_unsafe)
  			continue;
  		if (req->r_session &&
  		    req->r_session->s_mds == mds) {
  			dout(" kicking tid %llu
  ", req->r_tid);

  			__do_request(mdsc, req);

  		}
  	}
  }
  
  void ceph_mdsc_submit_request(struct ceph_mds_client *mdsc,
  			      struct ceph_mds_request *req)
  {
  	dout("submit_request on %p
  ", 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
  ", req);
  
  	/* take CAP_PIN refs for r_inode, r_locked_dir, r_old_dentry */
  	if (req->r_inode)
  		ceph_get_cap_refs(ceph_inode(req->r_inode), CEPH_CAP_PIN);
  	if (req->r_locked_dir)
  		ceph_get_cap_refs(ceph_inode(req->r_locked_dir), CEPH_CAP_PIN);
  	if (req->r_old_dentry)

  		ceph_get_cap_refs(ceph_inode(req->r_old_dentry_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
  ", err);
  		goto out;

  	}

  	/* wait */
  	mutex_unlock(&mdsc->mutex);
  	dout("do_request waiting
  ");
  	if (req->r_timeout) {

  		err = (long)wait_for_completion_killable_timeout(

  			&req->r_completion, req->r_timeout);
  		if (err == 0)
  			err = -EIO;
  	} else {

  		err = wait_for_completion_killable(&req->r_completion);

  	}
  	dout("do_request waited, got %d
  ", 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
  ", 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
  ", req, err);
  	return err;
  }
  
  /*

   * Invalidate dir D_COMPLETE, 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;
  	struct ceph_inode_info *ci = ceph_inode(inode);

  	dout("invalidate_dir_request %p (D_COMPLETE, lease(s))
  ", inode);

  	spin_lock(&ci->i_ceph_lock);

  	ceph_dir_clear_complete(inode);

  	ci->i_release_count++;

  	spin_unlock(&ci->i_ceph_lock);

  
  	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 */
  	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
  ");

  		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
  ", tid);
  		mutex_unlock(&mdsc->mutex);
  		return;
  	}
  	dout("handle_reply %p
  ", req);

  
  	/* correct session? */

  	if (req->r_session != session) {

  		pr_err("mdsc_handle_reply got %llu on session mds%d"
  		       " not mds%d
  ", tid, session->s_mds,
  		       req->r_session ? req->r_session->s_mds : -1);
  		mutex_unlock(&mdsc->mutex);
  		goto out;
  	}
  
  	/* dup? */
  	if ((req->r_got_unsafe && !head->safe) ||
  	    (req->r_got_safe && head->safe)) {
  		pr_warning("got a dup %s reply on %llu from mds%d
  ",
  			   head->safe ? "safe" : "unsafe", tid, mds);
  		mutex_unlock(&mdsc->mutex);
  		goto out;
  	}

  	if (req->r_got_safe && !head->safe) {
  		pr_warning("got unsafe after safe on %llu from mds%d
  ",
  			   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);

  		if (!req->r_inode) {
  			/* do nothing; not an authority problem */
  		} else 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  {
  			struct ceph_inode_info *ci = ceph_inode(req->r_inode);

  			struct ceph_cap *cap = NULL;
  
  			if (req->r_session)
  				cap = ceph_get_cap_for_mds(ci,
  						   req->r_session->s_mds);

  
  			dout("already using auth");
  			if ((!cap || cap != ci->i_auth_cap) ||
  			    (cap->mseq != req->r_sent_on_mseq)) {
  				dout("but cap 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);

  		complete_all(&req->r_safe_completion);

  
  		if (req->r_got_unsafe) {
  			/*
  			 * We already handled the unsafe response, now do the
  			 * cleanup.  No need to examine the response; the MDS
  			 * doesn't include any result info in the safe
  			 * response.  And even if it did, there is nothing
  			 * useful we could do with a revised return value.
  			 */
  			dout("got safe reply %llu, mds%d
  ", 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
  ", 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)
  ", mds, tid);

  		ceph_msg_dump(msg);

  		goto out_err;
  	}
  
  	/* snap trace */
  	if (rinfo->snapblob_len) {
  		down_write(&mdsc->snap_rwsem);
  		ceph_update_snap_trace(mdsc, rinfo->snapblob,
  			       rinfo->snapblob + rinfo->snapblob_len,
  			       le32_to_cpu(head->op) == CEPH_MDS_OP_RMSNAP);
  		downgrade_write(&mdsc->snap_rwsem);
  	} else {
  		down_read(&mdsc->snap_rwsem);
  	}
  
  	/* insert trace into our cache */

  	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_GETFILELOCK &&
  		    rinfo->dir_nr)

  			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);
  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
  ", 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
  ", tid, next_mds);

  		goto out;  /* dup reply? */
  	}

  	if (req->r_aborted) {
  		dout("forward tid %llu aborted, unregistering
  ", tid);
  		__unregister_request(mdsc, req);
  	} else if (fwd_seq <= req->r_num_fwd) {
  		dout("forward tid %llu to mds%d - old seq %d <= %d
  ",

  		     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)
  ", tid, next_mds);
  		BUG_ON(req->r_err);
  		BUG_ON(req->r_got_result);

  		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
  ", 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
  ",
  	     mds, ceph_session_op_name(op), session,
  	     session_state_name(session->s_state), seq);
  
  	if (session->s_state == CEPH_MDS_SESSION_HUNG) {
  		session->s_state = CEPH_MDS_SESSION_OPEN;
  		pr_info("mds%d came back
  ", session->s_mds);
  	}
  
  	switch (op) {
  	case CEPH_SESSION_OPEN:

  		if (session->s_state == CEPH_MDS_SESSION_RECONNECTING)
  			pr_info("mds%d reconnect success
  ", 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
  ", session->s_mds);

  		remove_session_caps(session);
  		wake = 1; /* for good measure */

  		wake_up_all(&mdsc->session_close_wq);

  		kick_requests(mdsc, mds);

  		break;
  
  	case CEPH_SESSION_STALE:
  		pr_info("mds%d caps went stale, renewing
  ",
  			session->s_mds);
  		spin_lock(&session->s_cap_lock);
  		session->s_cap_gen++;
  		session->s_cap_ttl = 0;
  		spin_unlock(&session->s_cap_lock);
  		send_renew_caps(mdsc, session);
  		break;
  
  	case CEPH_SESSION_RECALL_STATE:
  		trim_caps(mdsc, session, le32_to_cpu(h->max_caps));
  		break;
  
  	default:
  		pr_err("mdsc_handle_session bad op %d mds%d
  ", op, mds);
  		WARN_ON(1);
  	}
  
  	mutex_unlock(&session->s_mutex);
  	if (wake) {
  		mutex_lock(&mdsc->mutex);
  		__wake_requests(mdsc, &session->s_waiting);
  		mutex_unlock(&mdsc->mutex);
  	}
  	return;
  
  bad:
  	pr_err("mdsc_handle_session corrupt message mds%d len %d
  ", mds,
  	       (int)msg->front.iov_len);

  	ceph_msg_dump(msg);

  	return;
  }
  
  
  /*
   * called under session->mutex.
   */
  static void replay_unsafe_requests(struct ceph_mds_client *mdsc,
  				   struct ceph_mds_session *session)
  {
  	struct ceph_mds_request *req, *nreq;
  	int err;
  
  	dout("replay_unsafe_requests mds%d
  ", session->s_mds);
  
  	mutex_lock(&mdsc->mutex);
  	list_for_each_entry_safe(req, nreq, &session->s_unsafe, r_unsafe_item) {
  		err = __prepare_send_request(mdsc, req, session->s_mds);
  		if (!err) {
  			ceph_msg_get(req->r_request);
  			ceph_con_send(&session->s_con, req->r_request);
  		}
  	}
  	mutex_unlock(&mdsc->mutex);
  }
  
  /*
   * Encode information about a cap for a reconnect with the MDS.
   */

  static int encode_caps_cb(struct inode *inode, struct ceph_cap *cap,
  			  void *arg)
  {

  	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
  ",
  	     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 */

  
  	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_pagelist_cursor trunc_point;
  
  		ceph_pagelist_set_cursor(pagelist, &trunc_point);
  		do {

  			lock_flocks();

  			ceph_count_locks(inode, &num_fcntl_locks,
  					 &num_flock_locks);
  			rec.v2.flock_len = (2*sizeof(u32) +
  					    (num_fcntl_locks+num_flock_locks) *
  					    sizeof(struct ceph_filelock));

  			unlock_flocks();

  
  			/* pre-alloc pagelist */
  			ceph_pagelist_truncate(pagelist, &trunc_point);
  			err = ceph_pagelist_append(pagelist, &rec, reclen);
  			if (!err)
  				err = ceph_pagelist_reserve(pagelist,
  							    rec.v2.flock_len);
  
  			/* encode locks */
  			if (!err) {

  				lock_flocks();

  				err = ceph_encode_locks(inode,
  							pagelist,
  							num_fcntl_locks,
  							num_flock_locks);

  				unlock_flocks();

  			}
  		} while (err == -ENOSPC);

  	} else {
  		err = ceph_pagelist_append(pagelist, &rec, reclen);

  	}

  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;

  	struct ceph_pagelist *pagelist;

  	struct ceph_reconnect_state recon_state;

  	pr_info("mds%d reconnect start
  ", 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;

  	ceph_con_open(&session->s_con,
  		      ceph_mdsmap_get_addr(mdsc->mdsmap, mds));

  	/* replay unsafe requests */
  	replay_unsafe_requests(mdsc, session);

  
  	down_read(&mdsc->snap_rwsem);

  	dout("session %p state %s
  ", session,
  	     session_state_name(session->s_state));

  	/* drop old cap expires; we're about to reestablish that state */
  	discard_cap_releases(mdsc, session);

  	/* traverse this session's caps */

  	err = ceph_pagelist_encode_32(pagelist, session->s_nr_caps);
  	if (err)
  		goto fail;

  
  	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;

  
  	/*
  	 * 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
  ",
  		     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;

  	}

  	reply->pagelist = pagelist;

  	if (recon_state.flock)
  		reply->hdr.version = cpu_to_le16(2);

  	reply->hdr.data_len = cpu_to_le32(pagelist->length);
  	reply->nr_pages = calc_pages_for(0, pagelist->length);

  	ceph_con_send(&session->s_con, reply);

  	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);
  	kfree(pagelist);
  fail_nopagelist:

  	pr_err("error %d preparing reconnect for mds%d
  ", 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
  ",
  	     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)
  ",

  		     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)" : "",

  		     session_state_name(s->s_state));
  
  		if (memcmp(ceph_mdsmap_get_addr(oldmap, i),
  			   ceph_mdsmap_get_addr(newmap, i),
  			   sizeof(struct ceph_entity_addr))) {
  			if (s->s_state == CEPH_MDS_SESSION_OPENING) {
  				/* the session never opened, just close it
  				 * out now */
  				__wake_requests(mdsc, &s->s_waiting);

  				__unregister_session(mdsc, s);

  			} else {
  				/* just close it */
  				mutex_unlock(&mdsc->mutex);
  				mutex_lock(&s->s_mutex);
  				mutex_lock(&mdsc->mutex);
  				ceph_con_close(&s->s_con);
  				mutex_unlock(&s->s_mutex);
  				s->s_state = CEPH_MDS_SESSION_RESTARTING;
  			}
  
  			/* kick any requests waiting on the recovering mds */

  			kick_requests(mdsc, i);

  		} 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
  ", 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
  ",
  			     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
  ", 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;

  	mutex_lock(&session->s_mutex);
  	session->s_seq++;
  
  	/* lookup inode */
  	inode = ceph_find_inode(sb, vino);

  	dout("handle_lease %s, ino %llx %p %.*s
  ",
  	     ceph_lease_op_name(h->action), vino.ino, inode,

  	     dname.len, dname.name);

  	if (inode == NULL) {
  		dout("handle_lease no inode %llx
  ", vino.ino);
  		goto release;
  	}

  
  	/* dentry */
  	parent = d_find_alias(inode);
  	if (!parent) {
  		dout("no parent dentry on inode %p
  ", 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 =
  				le32_to_cpu(h->duration_ms) * HZ / 1000;

  			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
  ");

  	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
  ",
  	     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
  ",
  		     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
  ",
  	     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
  ");
  	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
  ");

  	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
  ",
  			     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
  ", 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)
  		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;
  	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
  ");
  		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
  ",
  			     req->r_tid);

  			__unregister_request(mdsc, req);

  		}
  	}
  	mutex_unlock(&mdsc->mutex);
  	dout("wait_requests done
  ");
  }
  
  /*
   * 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
  ");
  	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();