text: // SPDX-License-Identifier: GPL-2.0
  #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/ratelimit.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>
  
  #define RECONNECT_MAX_SIZE (INT_MAX - PAGE_SIZE)
  
  /*
   * 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   * are no longer valid.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_mds_session *session;
  	int nr_caps, nr_realms;
  	struct ceph_pagelist *pagelist;
  	unsigned msg_version;
  	bool allow_multi;
  };
  
  static void __wake_requests(struct ceph_mds_client *mdsc,
  			    struct list_head *head);
  static void ceph_cap_release_work(struct work_struct *work);
  static void ceph_cap_reclaim_work(struct work_struct *work);
  
  static const struct ceph_connection_operations mds_con_ops;
  
  
  /*
   * mds reply parsing
   */
  
  static int parse_reply_info_quota(void **p, void *end,
  				  struct ceph_mds_reply_info_in *info)
  {
  	u8 struct_v, struct_compat;
  	u32 struct_len;
  
  	ceph_decode_8_safe(p, end, struct_v, bad);
  	ceph_decode_8_safe(p, end, struct_compat, bad);
  	/* struct_v is expected to be >= 1. we only
  	 * understand encoding with struct_compat == 1. */
  	if (!struct_v || struct_compat != 1)
  		goto bad;
  	ceph_decode_32_safe(p, end, struct_len, bad);
  	ceph_decode_need(p, end, struct_len, bad);
  	end = *p + struct_len;
  	ceph_decode_64_safe(p, end, info->max_bytes, bad);
  	ceph_decode_64_safe(p, end, info->max_files, bad);
  	*p = end;
  	return 0;
  bad:
  	return -EIO;
  }
  
  /*
   * 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 = 0;
  	u8 struct_v = 0;
  
  	if (features == (u64)-1) {
  		u32 struct_len;
  		u8 struct_compat;
  		ceph_decode_8_safe(p, end, struct_v, bad);
  		ceph_decode_8_safe(p, end, struct_compat, bad);
  		/* struct_v is expected to be >= 1. we only understand
  		 * encoding with struct_compat == 1. */
  		if (!struct_v || struct_compat != 1)
  			goto bad;
  		ceph_decode_32_safe(p, end, struct_len, bad);
  		ceph_decode_need(p, end, struct_len, bad);
  		end = *p + struct_len;
  	}
  
  	ceph_decode_need(p, end, sizeof(struct ceph_mds_reply_inode), bad);
  	info->in = *p;
  	*p += sizeof(struct ceph_mds_reply_inode) +
  		sizeof(*info->in->fragtree.splits) *
  		le32_to_cpu(info->in->fragtree.nsplits);
  
  	ceph_decode_32_safe(p, end, info->symlink_len, bad);
  	ceph_decode_need(p, end, info->symlink_len, bad);
  	info->symlink = *p;
  	*p += info->symlink_len;
  
  	ceph_decode_copy_safe(p, end, &info->dir_layout,
  			      sizeof(info->dir_layout), bad);
  	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 == (u64)-1) {
  		/* 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;
  		/* quota */
  		err = parse_reply_info_quota(p, end, info);
  		if (err < 0)
  			goto out_bad;
  		/* pool namespace */
  		ceph_decode_32_safe(p, end, info->pool_ns_len, bad);
  		if (info->pool_ns_len > 0) {
  			ceph_decode_need(p, end, info->pool_ns_len, bad);
  			info->pool_ns_data = *p;
  			*p += info->pool_ns_len;
  		}
  
  		/* btime */
  		ceph_decode_need(p, end, sizeof(info->btime), bad);
  		ceph_decode_copy(p, &info->btime, sizeof(info->btime));
  
  		/* change attribute */
  		ceph_decode_64_safe(p, end, info->change_attr, bad);
  
  		/* dir pin */
  		if (struct_v >= 2) {
  			ceph_decode_32_safe(p, end, info->dir_pin, bad);
  		} else {
  			info->dir_pin = -ENODATA;
  		}
  
  		/* snapshot birth time, remains zero for v<=2 */
  		if (struct_v >= 3) {
  			ceph_decode_need(p, end, sizeof(info->snap_btime), bad);
  			ceph_decode_copy(p, &info->snap_btime,
  					 sizeof(info->snap_btime));
  		} else {
  			memset(&info->snap_btime, 0, sizeof(info->snap_btime));
  		}
  
  		*p = end;
  	} else {
  		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;
  
  		if (features & CEPH_FEATURE_MDS_QUOTA) {
  			err = parse_reply_info_quota(p, end, info);
  			if (err < 0)
  				goto out_bad;
  		} else {
  			info->max_bytes = 0;
  			info->max_files = 0;
  		}
  
  		info->pool_ns_len = 0;
  		info->pool_ns_data = NULL;
  		if (features & CEPH_FEATURE_FS_FILE_LAYOUT_V2) {
  			ceph_decode_32_safe(p, end, info->pool_ns_len, bad);
  			if (info->pool_ns_len > 0) {
  				ceph_decode_need(p, end, info->pool_ns_len, bad);
  				info->pool_ns_data = *p;
  				*p += info->pool_ns_len;
  			}
  		}
  
  		if (features & CEPH_FEATURE_FS_BTIME) {
  			ceph_decode_need(p, end, sizeof(info->btime), bad);
  			ceph_decode_copy(p, &info->btime, sizeof(info->btime));
  			ceph_decode_64_safe(p, end, info->change_attr, bad);
  		}
  
  		info->dir_pin = -ENODATA;
  		/* info->snap_btime remains zero */
  	}
  	return 0;
  bad:
  	err = -EIO;
  out_bad:
  	return err;
  }
  
  static int parse_reply_info_dir(void **p, void *end,
  				struct ceph_mds_reply_dirfrag **dirfrag,
  				u64 features)
  {
  	if (features == (u64)-1) {
  		u8 struct_v, struct_compat;
  		u32 struct_len;
  		ceph_decode_8_safe(p, end, struct_v, bad);
  		ceph_decode_8_safe(p, end, struct_compat, bad);
  		/* struct_v is expected to be >= 1. we only understand
  		 * encoding whose struct_compat == 1. */
  		if (!struct_v || struct_compat != 1)
  			goto bad;
  		ceph_decode_32_safe(p, end, struct_len, bad);
  		ceph_decode_need(p, end, struct_len, bad);
  		end = *p + struct_len;
  	}
  
  	ceph_decode_need(p, end, sizeof(**dirfrag), bad);
  	*dirfrag = *p;
  	*p += sizeof(**dirfrag) + sizeof(u32) * le32_to_cpu((*dirfrag)->ndist);
  	if (unlikely(*p > end))
  		goto bad;
  	if (features == (u64)-1)
  		*p = end;
  	return 0;
  bad:
  	return -EIO;
  }
  
  static int parse_reply_info_lease(void **p, void *end,
  				  struct ceph_mds_reply_lease **lease,
  				  u64 features)
  {
  	if (features == (u64)-1) {
  		u8 struct_v, struct_compat;
  		u32 struct_len;
  		ceph_decode_8_safe(p, end, struct_v, bad);
  		ceph_decode_8_safe(p, end, struct_compat, bad);
  		/* struct_v is expected to be >= 1. we only understand
  		 * encoding whose struct_compat == 1. */
  		if (!struct_v || struct_compat != 1)
  			goto bad;
  		ceph_decode_32_safe(p, end, struct_len, bad);
  		ceph_decode_need(p, end, struct_len, bad);
  		end = *p + struct_len;
  	}
  
  	ceph_decode_need(p, end, sizeof(**lease), bad);
  	*lease = *p;
  	*p += sizeof(**lease);
  	if (features == (u64)-1)
  		*p = end;
  	return 0;
  bad:
  	return -EIO;
  }
  
  /*
   * 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;
  
  		err = parse_reply_info_dir(p, end, &info->dirfrag, features);
  		if (err < 0)
  			goto out_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;
  
  		err = parse_reply_info_lease(p, end, &info->dlease, features);
  		if (err < 0)
  			goto out_bad;
  	}
  
  	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_readdir(void **p, void *end,
  				struct ceph_mds_reply_info_parsed *info,
  				u64 features)
  {
  	u32 num, i = 0;
  	int err;
  
  	err = parse_reply_info_dir(p, end, &info->dir_dir, features);
  	if (err < 0)
  		goto out_bad;
  
  	ceph_decode_need(p, end, sizeof(num) + 2, bad);
  	num = ceph_decode_32(p);
  	{
  		u16 flags = ceph_decode_16(p);
  		info->dir_end = !!(flags & CEPH_READDIR_FRAG_END);
  		info->dir_complete = !!(flags & CEPH_READDIR_FRAG_COMPLETE);
  		info->hash_order = !!(flags & CEPH_READDIR_HASH_ORDER);
  		info->offset_hash = !!(flags & CEPH_READDIR_OFFSET_HASH);
  	}
  	if (num == 0)
  		goto done;
  
  	BUG_ON(!info->dir_entries);
  	if ((unsigned long)(info->dir_entries + num) >
  	    (unsigned long)info->dir_entries + info->dir_buf_size) {
  		pr_err("dir contents are larger than expected\n");
  		WARN_ON(1);
  		goto bad;
  	}
  
  	info->dir_nr = num;
  	while (num) {
  		struct ceph_mds_reply_dir_entry *rde = info->dir_entries + i;
  		/* dentry */
  		ceph_decode_32_safe(p, end, rde->name_len, bad);
  		ceph_decode_need(p, end, rde->name_len, bad);
  		rde->name = *p;
  		*p += rde->name_len;
  		dout("parsed dir dname '%.*s'\n", rde->name_len, rde->name);
  
  		/* dentry lease */
  		err = parse_reply_info_lease(p, end, &rde->lease, features);
  		if (err)
  			goto out_bad;
  		/* inode */
  		err = parse_reply_info_in(p, end, &rde->inode, features);
  		if (err < 0)
  			goto out_bad;
  		/* ceph_readdir_prepopulate() will update it */
  		rde->offset = 0;
  		i++;
  		num--;
  	}
  
  done:
  	/* Skip over any unrecognized fields */
  	*p = end;
  	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;
  
  	/* Skip over any unrecognized fields */
  	*p = end;
  	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 == (u64)-1 ||
  	    (features & CEPH_FEATURE_REPLY_CREATE_INODE)) {
  		/* Malformed reply? */
  		if (*p == end) {
  			info->has_create_ino = false;
  		} else {
  			info->has_create_ino = true;
  			ceph_decode_64_safe(p, end, info->ino, bad);
  		}
  	} else {
  		if (*p != end)
  			goto bad;
  	}
  
  	/* Skip over any unrecognized fields */
  	*p = end;
  	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)
  {
  	u32 op = le32_to_cpu(info->head->op);
  
  	if (op == CEPH_MDS_OP_GETFILELOCK)
  		return parse_reply_info_filelock(p, end, info, features);
  	else if (op == CEPH_MDS_OP_READDIR || op == CEPH_MDS_OP_LSSNAP)
  		return parse_reply_info_readdir(p, end, info, features);
  	else if (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_entries)
  		return;
  	free_pages((unsigned long)info->dir_entries, 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";
  	case CEPH_MDS_SESSION_REJECTED: return "rejected";
  	default: return "???";
  	}
  }
  
  static struct ceph_mds_session *get_session(struct ceph_mds_session *s)
  {
  	if (refcount_inc_not_zero(&s->s_ref)) {
  		dout("mdsc get_session %p %d -> %d\n", s,
  		     refcount_read(&s->s_ref)-1, refcount_read(&s->s_ref));
  		return s;
  	} else {
  		dout("mdsc get_session %p 0 -- FAIL\n", s);
  		return NULL;
  	}
  }
  
  void ceph_put_mds_session(struct ceph_mds_session *s)
  {
  	dout("mdsc put_session %p %d -> %d\n", s,
  	     refcount_read(&s->s_ref), refcount_read(&s->s_ref)-1);
  	if (refcount_dec_and_test(&s->s_ref)) {
  		if (s->s_auth.authorizer)
  			ceph_auth_destroy_authorizer(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)
  {
  	if (mds >= mdsc->max_sessions || !mdsc->sessions[mds])
  		return NULL;
  	return get_session(mdsc->sessions[mds]);
  }
  
  static bool __have_session(struct ceph_mds_client *mdsc, int mds)
  {
  	if (mds >= mdsc->max_sessions || !mdsc->sessions[mds])
  		return false;
  	else
  		return true;
  }
  
  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_num_mds)
  		return ERR_PTR(-EINVAL);
  
  	s = kzalloc(sizeof(*s), GFP_NOFS);
  	if (!s)
  		return ERR_PTR(-ENOMEM);
  
  	if (mds >= mdsc->max_sessions) {
  		int newmax = 1 << get_count_order(mds + 1);
  		struct ceph_mds_session **sa;
  
  		dout("%s: realloc to %d\n", __func__, newmax);
  		sa = kcalloc(newmax, sizeof(void *), GFP_NOFS);
  		if (!sa)
  			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;
  	}
  
  	dout("%s: mds%d\n", __func__, mds);
  	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 = 1;
  	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;
  	refcount_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_WORK(&s->s_cap_release_work, ceph_cap_release_work);
  
  	INIT_LIST_HEAD(&s->s_cap_flushing);
  
  	mdsc->sessions[mds] = s;
  	atomic_inc(&mdsc->num_sessions);
  	refcount_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;
  	s->s_state = 0;
  	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);
  		/* avoid calling iput_final() in mds dispatch threads */
  		ceph_async_iput(req->r_inode);
  	}
  	if (req->r_parent) {
  		ceph_put_cap_refs(ceph_inode(req->r_parent), CEPH_CAP_PIN);
  		ceph_async_iput(req->r_parent);
  	}
  	ceph_async_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);
  		ceph_async_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);
  	WARN_ON_ONCE(!list_empty(&req->r_wait));
  	kfree(req);
  }
  
  DEFINE_RB_FUNCS(request, struct ceph_mds_request, r_tid, r_node)
  
  /*
   * lookup session, bump ref if found.
   *
   * called under mdsc->mutex.
   */
  static struct ceph_mds_request *
  lookup_get_request(struct ceph_mds_client *mdsc, u64 tid)
  {
  	struct ceph_mds_request *req;
  
  	req = lookup_request(&mdsc->request_tree, tid);
  	if (req)
  		ceph_mdsc_get_request(req);
  
  	return req;
  }
  
  /*
   * 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)
  {
  	int ret = 0;
  
  	req->r_tid = ++mdsc->last_tid;
  	if (req->r_num_caps) {
  		ret = ceph_reserve_caps(mdsc, &req->r_caps_reservation,
  					req->r_num_caps);
  		if (ret < 0) {
  			pr_err("__register_request %p "
  			       "failed to reserve caps: %d\n", req, ret);
  			/* set req->r_err to fail early from __do_request */
  			req->r_err = ret;
  			return;
  		}
  	}
  	dout("__register_request %p tid %lld\n", req, req->r_tid);
  	ceph_mdsc_get_request(req);
  	insert_request(&mdsc->request_tree, req);
  
  	req->r_uid = current_fsuid();
  	req->r_gid = current_fsgid();
  
  	if (mdsc->oldest_tid == 0 && req->r_op != CEPH_MDS_OP_SETFILELOCK)
  		mdsc->oldest_tid = req->r_tid;
  
  	if (dir) {
  		ihold(dir);
  		req->r_unsafe_dir = dir;
  	}
  }
  
  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);
  
  	/* Never leave an unregistered request on an unsafe list! */
  	list_del_init(&req->r_unsafe_item);
  
  	if (req->r_tid == mdsc->oldest_tid) {
  		struct rb_node *p = rb_next(&req->r_node);
  		mdsc->oldest_tid = 0;
  		while (p) {
  			struct ceph_mds_request *next_req =
  				rb_entry(p, struct ceph_mds_request, r_node);
  			if (next_req->r_op != CEPH_MDS_OP_SETFILELOCK) {
  				mdsc->oldest_tid = next_req->r_tid;
  				break;
  			}
  			p = rb_next(p);
  		}
  	}
  
  	erase_request(&mdsc->request_tree, req);
  
  	if (req->r_unsafe_dir  &&
  	    test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags)) {
  		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);
  	}
  	if (req->r_target_inode &&
  	    test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags)) {
  		struct ceph_inode_info *ci = ceph_inode(req->r_target_inode);
  		spin_lock(&ci->i_unsafe_lock);
  		list_del_init(&req->r_unsafe_target_item);
  		spin_unlock(&ci->i_unsafe_lock);
  	}
  
  	if (req->r_unsafe_dir) {
  		/* avoid calling iput_final() in mds dispatch threads */
  		ceph_async_iput(req->r_unsafe_dir);
  		req->r_unsafe_dir = NULL;
  	}
  
  	complete_all(&req->r_safe_completion);
  
  	ceph_mdsc_put_request(req);
  }
  
  /*
   * Walk back up the dentry tree until we hit a dentry representing a
   * non-snapshot inode. We do this using the rcu_read_lock (which must be held
   * when calling this) to ensure that the objects won't disappear while we're
   * working with them. Once we hit a candidate dentry, we attempt to take a
   * reference to it, and return that as the result.
   */
  static struct inode *get_nonsnap_parent(struct dentry *dentry)
  {
  	struct inode *inode = NULL;
  
  	while (dentry && !IS_ROOT(dentry)) {
  		inode = d_inode_rcu(dentry);
  		if (!inode || ceph_snap(inode) == CEPH_NOSNAP)
  			break;
  		dentry = dentry->d_parent;
  	}
  	if (inode)
  		inode = igrab(inode);
  	return inode;
  }
  
  /*
   * Choose mds to send request to next.  If there is a hint set in the
   * request (e.g., due to a prior forward hint from the mds), use that.
   * Otherwise, consult frag tree and/or caps to identify the
   * appropriate mds.  If all else fails, choose randomly.
   *
   * Called under mdsc->mutex.
   */
  static int __choose_mds(struct ceph_mds_client *mdsc,
  			struct ceph_mds_request *req)
  {
  	struct inode *inode;
  	struct ceph_inode_info *ci;
  	struct ceph_cap *cap;
  	int mode = req->r_direct_mode;
  	int mds = -1;
  	u32 hash = req->r_direct_hash;
  	bool is_hash = test_bit(CEPH_MDS_R_DIRECT_IS_HASH, &req->r_req_flags);
  
  	/*
  	 * 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) {
  		if (ceph_snap(req->r_inode) != CEPH_SNAPDIR) {
  			inode = req->r_inode;
  			ihold(inode);
  		} else {
  			/* req->r_dentry is non-null for LSSNAP request */
  			rcu_read_lock();
  			inode = get_nonsnap_parent(req->r_dentry);
  			rcu_read_unlock();
  			dout("__choose_mds using snapdir's parent %p\n", inode);
  		}
  	} else if (req->r_dentry) {
  		/* ignore race with rename; old or new d_parent is okay */
  		struct dentry *parent;
  		struct inode *dir;
  
  		rcu_read_lock();
  		parent = READ_ONCE(req->r_dentry->d_parent);
  		dir = req->r_parent ? : d_inode_rcu(parent);
  
  		if (!dir || dir->i_sb != mdsc->fsc->sb) {
  			/*  not this fs or parent went negative */
  			inode = d_inode(req->r_dentry);
  			if (inode)
  				ihold(inode);
  		} else if (ceph_snap(dir) != CEPH_NOSNAP) {
  			/* direct snapped/virtual snapdir requests
  			 * based on parent dir inode */
  			inode = get_nonsnap_parent(parent);
  			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 = igrab(dir);
  				hash = ceph_dentry_hash(dir, req->r_dentry);
  				is_hash = true;
  			} else {
  				ihold(inode);
  			}
  		}
  		rcu_read_unlock();
  	}
  
  	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)
  					goto out;
  			}
  
  			/* 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)
  					goto out;
  			}
  		}
  	}
  
  	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);
  		ceph_async_iput(inode);
  		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);
  out:
  	/* avoid calling iput_final() while holding mdsc->mutex or
  	 * in mds dispatch threads */
  	ceph_async_iput(inode);
  	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;
  }
  
  static void encode_supported_features(void **p, void *end)
  {
  	static const unsigned char bits[] = CEPHFS_FEATURES_CLIENT_SUPPORTED;
  	static const size_t count = ARRAY_SIZE(bits);
  
  	if (count > 0) {
  		size_t i;
  		size_t size = ((size_t)bits[count - 1] + 64) / 64 * 8;
  
  		BUG_ON(*p + 4 + size > end);
  		ceph_encode_32(p, size);
  		memset(*p, 0, size);
  		for (i = 0; i < count; i++)
  			((unsigned char*)(*p))[i / 8] |= 1 << (bits[i] % 8);
  		*p += size;
  	} else {
  		BUG_ON(*p + 4 > end);
  		ceph_encode_32(p, 0);
  	}
  }
  
  /*
   * 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 extra_bytes = 0;
  	int metadata_key_count = 0;
  	struct ceph_options *opt = mdsc->fsc->client->options;
  	struct ceph_mount_options *fsopt = mdsc->fsc->mount_options;
  	void *p, *end;
  
  	const char* metadata[][2] = {
  		{"hostname", mdsc->nodename},
  		{"kernel_version", init_utsname()->release},
  		{"entity_id", opt->name ? : ""},
  		{"root", fsopt->server_path ? : "/"},
  		{NULL, NULL}
  	};
  
  	/* Calculate serialized length of metadata */
  	extra_bytes = 4;  /* map length */
  	for (i = 0; metadata[i][0]; ++i) {
  		extra_bytes += 8 + strlen(metadata[i][0]) +
  			strlen(metadata[i][1]);
  		metadata_key_count++;
  	}
  	/* supported feature */
  	extra_bytes += 4 + 8;
  
  	/* Allocate the message */
  	msg = ceph_msg_new(CEPH_MSG_CLIENT_SESSION, sizeof(*h) + extra_bytes,
  			   GFP_NOFS, false);
  	if (!msg) {
  		pr_err("create_session_msg ENOMEM creating msg\n");
  		return NULL;
  	}
  	p = msg->front.iov_base;
  	end = p + msg->front.iov_len;
  
  	h = p;
  	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(3);
  	msg->hdr.compat_version = cpu_to_le16(1);
  
  	/* The write pointer, following the session_head structure */
  	p += 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]; ++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;
  	}
  
  	encode_supported_features(&p, end);
  	msg->front.iov_len = p - msg->front.iov_base;
  	msg->hdr.front_len = cpu_to_le32(msg->front.iov_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_num_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
   */
  
  static void detach_cap_releases(struct ceph_mds_session *session,
  				struct list_head *target)
  {
  	lockdep_assert_held(&session->s_cap_lock);
  
  	list_splice_init(&session->s_cap_releases, target);
  	session->s_num_cap_releases = 0;
  	dout("dispose_cap_releases mds%d\n", session->s_mds);
  }
  
  static void dispose_cap_releases(struct ceph_mds_client *mdsc,
  				 struct list_head *dispose)
  {
  	while (!list_empty(dispose)) {
  		struct ceph_cap *cap;
  		/* zero out the in-progress message */
  		cap = list_first_entry(dispose, struct ceph_cap, session_caps);
  		list_del(&cap->session_caps);
  		ceph_put_cap(mdsc, cap);
  	}
  }
  
  static void cleanup_session_requests(struct ceph_mds_client *mdsc,
  				     struct ceph_mds_session *session)
  {
  	struct ceph_mds_request *req;
  	struct rb_node *p;
  	struct ceph_inode_info *ci;
  
  	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);
  		pr_warn_ratelimited(" dropping unsafe request %llu\n",
  				    req->r_tid);
  		if (req->r_target_inode) {
  			/* dropping unsafe change of inode's attributes */
  			ci = ceph_inode(req->r_target_inode);
  			errseq_set(&ci->i_meta_err, -EIO);
  		}
  		if (req->r_unsafe_dir) {
  			/* dropping unsafe directory operation */
  			ci = ceph_inode(req->r_unsafe_dir);
  			errseq_set(&ci->i_meta_err, -EIO);
  		}
  		__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.
   */
  int ceph_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) {
  			/* avoid calling iput_final() while holding
  			 * s_mutex or in mds dispatch threads */
  			ceph_async_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) {
  			dout("iterate_session_caps  finishing cap %p removal\n",
  			     cap);
  			BUG_ON(cap->session != session);
  			cap->session = NULL;
  			list_del_init(&cap->session_caps);
  			session->s_nr_caps--;
  			if (cap->queue_release)
  				__ceph_queue_cap_release(session, cap);
  			else
  				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);
  
  	ceph_async_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_fs_client *fsc = (struct ceph_fs_client *)arg;
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	LIST_HEAD(to_remove);
  	bool dirty_dropped = false;
  	bool invalidate = false;
  
  	dout("removing cap %p, ci is %p, inode is %p\n",
  	     cap, ci, &ci->vfs_inode);
  	spin_lock(&ci->i_ceph_lock);
  	if (cap->mds_wanted | cap->issued)
  		ci->i_ceph_flags |= CEPH_I_CAP_DROPPED;
  	__ceph_remove_cap(cap, false);
  	if (!ci->i_auth_cap) {
  		struct ceph_cap_flush *cf;
  		struct ceph_mds_client *mdsc = fsc->mdsc;
  
  		if (READ_ONCE(fsc->mount_state) == CEPH_MOUNT_SHUTDOWN) {
  			if (inode->i_data.nrpages > 0)
  				invalidate = true;
  			if (ci->i_wrbuffer_ref > 0)
  				mapping_set_error(&inode->i_data, -EIO);
  		}
  
  		while (!list_empty(&ci->i_cap_flush_list)) {
  			cf = list_first_entry(&ci->i_cap_flush_list,
  					      struct ceph_cap_flush, i_list);
  			list_move(&cf->i_list, &to_remove);
  		}
  
  		spin_lock(&mdsc->cap_dirty_lock);
  
  		list_for_each_entry(cf, &to_remove, i_list)
  			list_del(&cf->g_list);
  
  		if (!list_empty(&ci->i_dirty_item)) {
  			pr_warn_ratelimited(
  				" 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);
  			dirty_dropped = true;
  		}
  		if (!list_empty(&ci->i_flushing_item)) {
  			pr_warn_ratelimited(
  				" 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--;
  			dirty_dropped = true;
  		}
  		spin_unlock(&mdsc->cap_dirty_lock);
  
  		if (dirty_dropped) {
  			errseq_set(&ci->i_meta_err, -EIO);
  
  			if (ci->i_wrbuffer_ref_head == 0 &&
  			    ci->i_wr_ref == 0 &&
  			    ci->i_dirty_caps == 0 &&
  			    ci->i_flushing_caps == 0) {
  				ceph_put_snap_context(ci->i_head_snapc);
  				ci->i_head_snapc = NULL;
  			}
  		}
  
  		if (atomic_read(&ci->i_filelock_ref) > 0) {
  			/* make further file lock syscall return -EIO */
  			ci->i_ceph_flags |= CEPH_I_ERROR_FILELOCK;
  			pr_warn_ratelimited(" dropping file locks for %p %lld\n",
  					    inode, ceph_ino(inode));
  		}
  
  		if (!ci->i_dirty_caps && ci->i_prealloc_cap_flush) {
  			list_add(&ci->i_prealloc_cap_flush->i_list, &to_remove);
  			ci->i_prealloc_cap_flush = NULL;
  		}
  	}
  	spin_unlock(&ci->i_ceph_lock);
  	while (!list_empty(&to_remove)) {
  		struct ceph_cap_flush *cf;
  		cf = list_first_entry(&to_remove,
  				      struct ceph_cap_flush, i_list);
  		list_del(&cf->i_list);
  		ceph_free_cap_flush(cf);
  	}
  
  	wake_up_all(&ci->i_cap_wq);
  	if (invalidate)
  		ceph_queue_invalidate(inode);
  	if (dirty_dropped)
  		iput(inode);
  	return 0;
  }
  
  /*
   * caller must hold session s_mutex
   */
  static void remove_session_caps(struct ceph_mds_session *session)
  {
  	struct ceph_fs_client *fsc = session->s_mdsc->fsc;
  	struct super_block *sb = fsc->sb;
  	LIST_HEAD(dispose);
  
  	dout("remove_session_caps on %p\n", session);
  	ceph_iterate_session_caps(session, remove_session_caps_cb, fsc);
  
  	wake_up_all(&fsc->mdsc->cap_flushing_wq);
  
  	spin_lock(&session->s_cap_lock);
  	if (session->s_nr_caps > 0) {
  		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);
  			 /* avoid calling iput_final() while holding s_mutex */
  			ceph_async_iput(inode);
  
  			spin_lock(&session->s_cap_lock);
  		}
  	}
  
  	// drop cap expires and unlock s_cap_lock
  	detach_cap_releases(session, &dispose);
  
  	BUG_ON(session->s_nr_caps > 0);
  	BUG_ON(!list_empty(&session->s_cap_flushing));
  	spin_unlock(&session->s_cap_lock);
  	dispose_cap_releases(session->s_mdsc, &dispose);
  }
  
  enum {
  	RECONNECT,
  	RENEWCAPS,
  	FORCE_RO,
  };
  
  /*
   * 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);
  	unsigned long ev = (unsigned long)arg;
  
  	if (ev == RECONNECT) {
  		spin_lock(&ci->i_ceph_lock);
  		ci->i_wanted_max_size = 0;
  		ci->i_requested_max_size = 0;
  		spin_unlock(&ci->i_ceph_lock);
  	} else if (ev == RENEWCAPS) {
  		if (cap->cap_gen < cap->session->s_cap_gen) {
  			/* mds did not re-issue stale cap */
  			spin_lock(&ci->i_ceph_lock);
  			cap->issued = cap->implemented = CEPH_CAP_PIN;
  			/* make sure mds knows what we want */
  			if (__ceph_caps_file_wanted(ci) & ~cap->mds_wanted)
  				ci->i_ceph_flags |= CEPH_I_CAP_DROPPED;
  			spin_unlock(&ci->i_ceph_lock);
  		}
  	} else if (ev == FORCE_RO) {
  	}
  	wake_up_all(&ci->i_cap_wq);
  	return 0;
  }
  
  static void wake_up_session_caps(struct ceph_mds_session *session, int ev)
  {
  	dout("wake_up_session_caps %p mds%d\n", session, session->s_mds);
  	ceph_iterate_session_caps(session, wake_up_session_cb,
  				  (void *)(unsigned long)ev);
  }
  
  /*
   * 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, RENEWCAPS);
  }
  
  /*
   * 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 1;
  }
  
  /*
   * 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);
  }
  
  static bool drop_negative_children(struct dentry *dentry)
  {
  	struct dentry *child;
  	bool all_negative = true;
  
  	if (!d_is_dir(dentry))
  		goto out;
  
  	spin_lock(&dentry->d_lock);
  	list_for_each_entry(child, &dentry->d_subdirs, d_child) {
  		if (d_really_is_positive(child)) {
  			all_negative = false;
  			break;
  		}
  	}
  	spin_unlock(&dentry->d_lock);
  
  	if (all_negative)
  		shrink_dcache_parent(dentry);
  out:
  	return all_negative;
  }
  
  /*
   * 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)
  {
  	int *remaining = arg;
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	int used, wanted, oissued, mine;
  
  	if (*remaining <= 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 ||
  		    !list_empty(&ci->i_cap_snaps))
  			goto out;
  		if ((used | wanted) & CEPH_CAP_ANY_WR)
  			goto out;
  		/* Note: it's possible that i_filelock_ref becomes non-zero
  		 * after dropping auth caps. It doesn't hurt because reply
  		 * of lock mds request will re-add auth caps. */
  		if (atomic_read(&ci->i_filelock_ref) > 0)
  			goto out;
  	}
  	/* The inode has cached pages, but it's no longer used.
  	 * we can safely drop it */
  	if (wanted == 0 && used == CEPH_CAP_FILE_CACHE &&
  	    !(oissued & CEPH_CAP_FILE_CACHE)) {
  	  used = 0;
  	  oissued = 0;
  	}
  	if ((used | wanted) & ~oissued & mine)
  		goto out;   /* we need these caps */
  
  	if (oissued) {
  		/* we aren't the only cap.. just remove us */
  		__ceph_remove_cap(cap, true);
  		(*remaining)--;
  	} else {
  		struct dentry *dentry;
  		/* try dropping referring dentries */
  		spin_unlock(&ci->i_ceph_lock);
  		dentry = d_find_any_alias(inode);
  		if (dentry && drop_negative_children(dentry)) {
  			int count;
  			dput(dentry);
  			d_prune_aliases(inode);
  			count = atomic_read(&inode->i_count);
  			if (count == 1)
  				(*remaining)--;
  			dout("trim_caps_cb %p cap %p pruned, count now %d\n",
  			     inode, cap, count);
  		} else {
  			dput(dentry);
  		}
  		return 0;
  	}
  
  out:
  	spin_unlock(&ci->i_ceph_lock);
  	return 0;
  }
  
  /*
   * Trim session cap count down to some max number.
   */
  int ceph_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) {
  		int remaining = trim_caps;
  
  		ceph_iterate_session_caps(session, trim_caps_cb, &remaining);
  		dout("trim_caps mds%d done: %d / %d, trimmed %d\n",
  		     session->s_mds, session->s_nr_caps, max_caps,
  			trim_caps - remaining);
  	}
  
  	ceph_flush_cap_releases(mdsc, session);
  	return 0;
  }
  
  static int check_caps_flush(struct ceph_mds_client *mdsc,
  			    u64 want_flush_tid)
  {
  	int ret = 1;
  
  	spin_lock(&mdsc->cap_dirty_lock);
  	if (!list_empty(&mdsc->cap_flush_list)) {
  		struct ceph_cap_flush *cf =
  			list_first_entry(&mdsc->cap_flush_list,
  					 struct ceph_cap_flush, g_list);
  		if (cf->tid <= want_flush_tid) {
  			dout("check_caps_flush still flushing tid "
  			     "%llu <= %llu\n", cf->tid, want_flush_tid);
  			ret = 0;
  		}
  	}
  	spin_unlock(&mdsc->cap_dirty_lock);
  	return ret;
  }
  
  /*
   * flush all dirty inode data to disk.
   *
   * returns true if we've flushed through want_flush_tid
   */
  static void wait_caps_flush(struct ceph_mds_client *mdsc,
  			    u64 want_flush_tid)
  {
  	dout("check_caps_flush want %llu\n", want_flush_tid);
  
  	wait_event(mdsc->cap_flushing_wq,
  		   check_caps_flush(mdsc, want_flush_tid));
  
  	dout("check_caps_flush ok, flushed thru %llu\n", want_flush_tid);
  }
  
  /*
   * called under s_mutex
   */
  static void ceph_send_cap_releases(struct ceph_mds_client *mdsc,
  				   struct ceph_mds_session *session)
  {
  	struct ceph_msg *msg = NULL;
  	struct ceph_mds_cap_release *head;
  	struct ceph_mds_cap_item *item;
  	struct ceph_osd_client *osdc = &mdsc->fsc->client->osdc;
  	struct ceph_cap *cap;
  	LIST_HEAD(tmp_list);
  	int num_cap_releases;
  	__le32	barrier, *cap_barrier;
  
  	down_read(&osdc->lock);
  	barrier = cpu_to_le32(osdc->epoch_barrier);
  	up_read(&osdc->lock);
  
  	spin_lock(&session->s_cap_lock);
  again:
  	list_splice_init(&session->s_cap_releases, &tmp_list);
  	num_cap_releases = session->s_num_cap_releases;
  	session->s_num_cap_releases = 0;
  	spin_unlock(&session->s_cap_lock);
  
  	while (!list_empty(&tmp_list)) {
  		if (!msg) {
  			msg = ceph_msg_new(CEPH_MSG_CLIENT_CAPRELEASE,
  					PAGE_SIZE, GFP_NOFS, false);
  			if (!msg)
  				goto out_err;
  			head = msg->front.iov_base;
  			head->num = cpu_to_le32(0);
  			msg->front.iov_len = sizeof(*head);
  
  			msg->hdr.version = cpu_to_le16(2);
  			msg->hdr.compat_version = cpu_to_le16(1);
  		}
  
  		cap = list_first_entry(&tmp_list, struct ceph_cap,
  					session_caps);
  		list_del(&cap->session_caps);
  		num_cap_releases--;
  
  		head = msg->front.iov_base;
  		put_unaligned_le32(get_unaligned_le32(&head->num) + 1,
  				   &head->num);
  		item = msg->front.iov_base + msg->front.iov_len;
  		item->ino = cpu_to_le64(cap->cap_ino);
  		item->cap_id = cpu_to_le64(cap->cap_id);
  		item->migrate_seq = cpu_to_le32(cap->mseq);
  		item->seq = cpu_to_le32(cap->issue_seq);
  		msg->front.iov_len += sizeof(*item);
  
  		ceph_put_cap(mdsc, cap);
  
  		if (le32_to_cpu(head->num) == CEPH_CAPS_PER_RELEASE) {
  			// Append cap_barrier field
  			cap_barrier = msg->front.iov_base + msg->front.iov_len;
  			*cap_barrier = barrier;
  			msg->front.iov_len += sizeof(*cap_barrier);
  
  			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);
  			msg = NULL;
  		}
  	}
  
  	BUG_ON(num_cap_releases != 0);
  
  	spin_lock(&session->s_cap_lock);
  	if (!list_empty(&session->s_cap_releases))
  		goto again;
  	spin_unlock(&session->s_cap_lock);
  
  	if (msg) {
  		// Append cap_barrier field
  		cap_barrier = msg->front.iov_base + msg->front.iov_len;
  		*cap_barrier = barrier;
  		msg->front.iov_len += sizeof(*cap_barrier);
  
  		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);
  	}
  	return;
  out_err:
  	pr_err("send_cap_releases mds%d, failed to allocate message\n",
  		session->s_mds);
  	spin_lock(&session->s_cap_lock);
  	list_splice(&tmp_list, &session->s_cap_releases);
  	session->s_num_cap_releases += num_cap_releases;
  	spin_unlock(&session->s_cap_lock);
  }
  
  static void ceph_cap_release_work(struct work_struct *work)
  {
  	struct ceph_mds_session *session =
  		container_of(work, struct ceph_mds_session, s_cap_release_work);
  
  	mutex_lock(&session->s_mutex);
  	if (session->s_state == CEPH_MDS_SESSION_OPEN ||
  	    session->s_state == CEPH_MDS_SESSION_HUNG)
  		ceph_send_cap_releases(session->s_mdsc, session);
  	mutex_unlock(&session->s_mutex);
  	ceph_put_mds_session(session);
  }
  
  void ceph_flush_cap_releases(struct ceph_mds_client *mdsc,
  		             struct ceph_mds_session *session)
  {
  	if (mdsc->stopping)
  		return;
  
  	get_session(session);
  	if (queue_work(mdsc->fsc->cap_wq,
  		       &session->s_cap_release_work)) {
  		dout("cap release work queued\n");
  	} else {
  		ceph_put_mds_session(session);
  		dout("failed to queue cap release work\n");
  	}
  }
  
  /*
   * caller holds session->s_cap_lock
   */
  void __ceph_queue_cap_release(struct ceph_mds_session *session,
  			      struct ceph_cap *cap)
  {
  	list_add_tail(&cap->session_caps, &session->s_cap_releases);
  	session->s_num_cap_releases++;
  
  	if (!(session->s_num_cap_releases % CEPH_CAPS_PER_RELEASE))
  		ceph_flush_cap_releases(session->s_mdsc, session);
  }
  
  static void ceph_cap_reclaim_work(struct work_struct *work)
  {
  	struct ceph_mds_client *mdsc =
  		container_of(work, struct ceph_mds_client, cap_reclaim_work);
  	int ret = ceph_trim_dentries(mdsc);
  	if (ret == -EAGAIN)
  		ceph_queue_cap_reclaim_work(mdsc);
  }
  
  void ceph_queue_cap_reclaim_work(struct ceph_mds_client *mdsc)
  {
  	if (mdsc->stopping)
  		return;
  
          if (queue_work(mdsc->fsc->cap_wq, &mdsc->cap_reclaim_work)) {
                  dout("caps reclaim work queued\n");
          } else {
                  dout("failed to queue caps release work\n");
          }
  }
  
  void ceph_reclaim_caps_nr(struct ceph_mds_client *mdsc, int nr)
  {
  	int val;
  	if (!nr)
  		return;
  	val = atomic_add_return(nr, &mdsc->cap_reclaim_pending);
  	if (!(val % CEPH_CAPS_PER_RELEASE)) {
  		atomic_set(&mdsc->cap_reclaim_pending, 0);
  		ceph_queue_cap_reclaim_work(mdsc);
  	}
  }
  
  /*
   * 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(struct ceph_mds_reply_dir_entry);
  	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_entries = (void*)__get_free_pages(GFP_KERNEL |
  							     __GFP_NOWARN,
  							     order);
  		if (rinfo->dir_entries)
  			break;
  		order--;
  	}
  	if (!rinfo->dir_entries)
  		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);
  	struct timespec64 ts;
  
  	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);
  	INIT_LIST_HEAD(&req->r_unsafe_target_item);
  	req->r_fmode = -1;
  	kref_init(&req->r_kref);
  	RB_CLEAR_NODE(&req->r_node);
  	INIT_LIST_HEAD(&req->r_wait);
  	init_completion(&req->r_completion);
  	init_completion(&req->r_safe_completion);
  	INIT_LIST_HEAD(&req->r_unsafe_item);
  
  	ktime_get_coarse_real_ts64(&ts);
  	req->r_stamp = timespec64_trunc(ts, mdsc->fsc->sb->s_time_gran);
  
  	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 inline  u64 __get_oldest_tid(struct ceph_mds_client *mdsc)
  {
  	return mdsc->oldest_tid;
  }
  
  /*
   * 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 *pbase,
  			   int stop_on_nosnap)
  {
  	struct dentry *temp;
  	char *path;
  	int pos;
  	unsigned seq;
  	u64 base;
  
  	if (!dentry)
  		return ERR_PTR(-EINVAL);
  
  	path = __getname();
  	if (!path)
  		return ERR_PTR(-ENOMEM);
  retry:
  	pos = PATH_MAX - 1;
  	path[pos] = '\0';
  
  	seq = read_seqbegin(&rename_lock);
  	rcu_read_lock();
  	temp = dentry;
  	for (;;) {
  		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 && dentry != temp &&
  			   ceph_snap(inode) == CEPH_NOSNAP) {
  			spin_unlock(&temp->d_lock);
  			pos++; /* get rid of any prepended '/' */
  			break;
  		} else {
  			pos -= temp->d_name.len;
  			if (pos < 0) {
  				spin_unlock(&temp->d_lock);
  				break;
  			}
  			memcpy(path + pos, temp->d_name.name, temp->d_name.len);
  		}
  		spin_unlock(&temp->d_lock);
  		temp = READ_ONCE(temp->d_parent);
  
  		/* Are we at the root? */
  		if (IS_ROOT(temp))
  			break;
  
  		/* Are we out of buffer? */
  		if (--pos < 0)
  			break;
  
  		path[pos] = '/';
  	}
  	base = ceph_ino(d_inode(temp));
  	rcu_read_unlock();
  	if (pos < 0 || read_seqretry(&rename_lock, seq)) {
  		pr_err("build_path did not end path lookup where "
  		       "expected, pos is %d\n", 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) */
  		goto retry;
  	}
  
  	*pbase = base;
  	*plen = PATH_MAX - 1 - pos;
  	dout("build_path on %p %d built %llx '%.*s'\n",
  	     dentry, d_count(dentry), base, *plen, path + pos);
  	return path + pos;
  }
  
  static int build_dentry_path(struct dentry *dentry, struct inode *dir,
  			     const char **ppath, int *ppathlen, u64 *pino,
  			     bool *pfreepath, bool parent_locked)
  {
  	char *path;
  
  	rcu_read_lock();
  	if (!dir)
  		dir = d_inode_rcu(dentry->d_parent);
  	if (dir && parent_locked && ceph_snap(dir) == CEPH_NOSNAP) {
  		*pino = ceph_ino(dir);
  		rcu_read_unlock();
  		*ppath = dentry->d_name.name;
  		*ppathlen = dentry->d_name.len;
  		return 0;
  	}
  	rcu_read_unlock();
  	path = ceph_mdsc_build_path(dentry, ppathlen, pino, 1);
  	if (IS_ERR(path))
  		return PTR_ERR(path);
  	*ppath = path;
  	*pfreepath = true;
  	return 0;
  }
  
  static int build_inode_path(struct inode *inode,
  			    const char **ppath, int *ppathlen, u64 *pino,
  			    bool *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 = true;
  	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,
  				  struct inode *rdiri, const char *rpath,
  				  u64 rino, const char **ppath, int *pathlen,
  				  u64 *ino, bool *freepath, bool parent_locked)
  {
  	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, rdiri, ppath, pathlen, ino,
  					freepath, parent_locked);
  		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;
  	bool freepath1 = false, freepath2 = false;
  	int len;
  	u16 releases;
  	void *p, *end;
  	int ret;
  
  	ret = set_request_path_attr(req->r_inode, req->r_dentry,
  			      req->r_parent, req->r_path1, req->r_ino1.ino,
  			      &path1, &pathlen1, &ino1, &freepath1,
  			      test_bit(CEPH_MDS_R_PARENT_LOCKED,
  					&req->r_req_flags));
  	if (ret < 0) {
  		msg = ERR_PTR(ret);
  		goto out;
  	}
  
  	/* If r_old_dentry is set, then assume that its parent is locked */
  	ret = set_request_path_attr(NULL, req->r_old_dentry,
  			      req->r_old_dentry_dir,
  			      req->r_path2, req->r_ino2.ino,
  			      &path2, &pathlen2, &ino2, &freepath2, true);
  	if (ret < 0) {
  		msg = ERR_PTR(ret);
  		goto out_free1;
  	}
  
  	len = sizeof(*head) +
  		pathlen1 + pathlen2 + 2*(1 + sizeof(u32) + sizeof(u64)) +
  		sizeof(struct ceph_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 += pathlen1;
  	if (req->r_old_dentry_drop)
  		len += pathlen2;
  
  	msg = ceph_msg_new2(CEPH_MSG_CLIENT_REQUEST, len, 1, 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,
  				req->r_parent, 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,
  				req->r_old_dentry_dir, 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_timespec64(&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;
  		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)
  		ceph_mdsc_free_path((char *)path2, pathlen2);
  out_free1:
  	if (freepath1)
  		ceph_mdsc_free_path((char *)path1, pathlen1);
  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);
  	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 (test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags)) {
  		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_timespec64(&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);
  		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 (test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags))
  		flags |= CEPH_MDS_FLAG_REPLAY;
  	if (req->r_parent)
  		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_parent = %p\n", req->r_parent);
  	return 0;
  }
  
  /*
   * send request, or put it on the appropriate wait list.
   */
  static void __do_request(struct ceph_mds_client *mdsc,
  			struct ceph_mds_request *req)
  {
  	struct ceph_mds_session *session = NULL;
  	int mds = -1;
  	int err = 0;
  
  	if (req->r_err || test_bit(CEPH_MDS_R_GOT_RESULT, &req->r_req_flags)) {
  		if (test_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags))
  			__unregister_request(mdsc, req);
  		return;
  	}
  
  	if (req->r_timeout &&
  	    time_after_eq(jiffies, req->r_started + req->r_timeout)) {
  		dout("do_request timed out\n");
  		err = -EIO;
  		goto finish;
  	}
  	if (READ_ONCE(mdsc->fsc->mount_state) == CEPH_MOUNT_SHUTDOWN) {
  		dout("do_request forced umount\n");
  		err = -EIO;
  		goto finish;
  	}
  	if (READ_ONCE(mdsc->fsc->mount_state) == CEPH_MOUNT_MOUNTING) {
  		if (mdsc->mdsmap_err) {
  			err = mdsc->mdsmap_err;
  			dout("do_request mdsmap err %d\n", err);
  			goto finish;
  		}
  		if (mdsc->mdsmap->m_epoch == 0) {
  			dout("do_request no mdsmap, waiting for map\n");
  			list_add(&req->r_wait, &mdsc->waiting_for_map);
  			return;
  		}
  		if (!(mdsc->fsc->mount_options->flags &
  		      CEPH_MOUNT_OPT_MOUNTWAIT) &&
  		    !ceph_mdsmap_is_cluster_available(mdsc->mdsmap)) {
  			err = -EHOSTUNREACH;
  			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);
  		return;
  	}
  
  	/* 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_REJECTED) {
  			err = -EACCES;
  			goto out_session;
  		}
  		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);
  finish:
  	if (err) {
  		dout("__do_request early error %d\n", err);
  		req->r_err = err;
  		complete_request(mdsc, req);
  		__unregister_request(mdsc, req);
  	}
  	return;
  }
  
  /*
   * 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 (test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags))
  			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);
  		}
  	}
  }
  
  int ceph_mdsc_submit_request(struct ceph_mds_client *mdsc, struct inode *dir,
  			      struct ceph_mds_request *req)
  {
  	int err;
  
  	/* take CAP_PIN refs for r_inode, r_parent, r_old_dentry */
  	if (req->r_inode)
  		ceph_get_cap_refs(ceph_inode(req->r_inode), CEPH_CAP_PIN);
  	if (req->r_parent) {
  		ceph_get_cap_refs(ceph_inode(req->r_parent), CEPH_CAP_PIN);
  		ihold(req->r_parent);
  	}
  	if (req->r_old_dentry_dir)
  		ceph_get_cap_refs(ceph_inode(req->r_old_dentry_dir),
  				  CEPH_CAP_PIN);
  
  	dout("submit_request on %p for inode %p\n", req, dir);
  	mutex_lock(&mdsc->mutex);
  	__register_request(mdsc, req, dir);
  	__do_request(mdsc, req);
  	err = req->r_err;
  	mutex_unlock(&mdsc->mutex);
  	return err;
  }
  
  static int ceph_mdsc_wait_request(struct ceph_mds_client *mdsc,
  				  struct ceph_mds_request *req)
  {
  	int err;
  
  	/* wait */
  	dout("do_request waiting\n");
  	if (!req->r_timeout && req->r_wait_for_completion) {
  		err = req->r_wait_for_completion(mdsc, req);
  	} else {
  		long timeleft = wait_for_completion_killable_timeout(
  					&req->r_completion,
  					ceph_timeout_jiffies(req->r_timeout));
  		if (timeleft > 0)
  			err = 0;
  		else if (!timeleft)
  			err = -EIO;  /* timed out */
  		else
  			err = timeleft;  /* killed */
  	}
  	dout("do_request waited, got %d\n", err);
  	mutex_lock(&mdsc->mutex);
  
  	/* only abort if we didn't race with a real reply */
  	if (test_bit(CEPH_MDS_R_GOT_RESULT, &req->r_req_flags)) {
  		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;
  		set_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags);
  		mutex_unlock(&req->r_fill_mutex);
  
  		if (req->r_parent &&
  		    (req->r_op & CEPH_MDS_OP_WRITE))
  			ceph_invalidate_dir_request(req);
  	} else {
  		err = req->r_err;
  	}
  
  	mutex_unlock(&mdsc->mutex);
  	return err;
  }
  
  /*
   * 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);
  
  	/* issue */
  	err = ceph_mdsc_submit_request(mdsc, dir, req);
  	if (!err)
  		err = ceph_mdsc_wait_request(mdsc, req);
  	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 *dir = req->r_parent;
  	struct inode *old_dir = req->r_old_dentry_dir;
  
  	dout("invalidate_dir_request %p %p (complete, lease(s))\n", dir, old_dir);
  
  	ceph_dir_clear_complete(dir);
  	if (old_dir)
  		ceph_dir_clear_complete(old_dir);
  	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_get_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 ((test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags) && !head->safe) ||
  	    (test_bit(CEPH_MDS_R_GOT_SAFE, &req->r_req_flags) && 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 (test_bit(CEPH_MDS_R_GOT_SAFE, &req->r_req_flags)) {
  		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\n", req->r_tid);
  		req->r_resend_mds = -1;
  		if (req->r_direct_mode != USE_AUTH_MDS) {
  			dout("not using auth, setting for that now\n");
  			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\n");
  				__do_request(mdsc, req);
  				mutex_unlock(&mdsc->mutex);
  				goto out;
  			}
  		}
  		dout("have to return ESTALE on request %llu\n", req->r_tid);
  	}
  
  
  	if (head->safe) {
  		set_bit(CEPH_MDS_R_GOT_SAFE, &req->r_req_flags);
  		__unregister_request(mdsc, req);
  
  		if (test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags)) {
  			/*
  			 * 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);
  
  			/* 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 {
  		set_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags);
  		list_add_tail(&req->r_unsafe_item, &req->r_session->s_unsafe);
  		if (req->r_unsafe_dir) {
  			struct ceph_inode_info *ci =
  					ceph_inode(req->r_unsafe_dir);
  			spin_lock(&ci->i_unsafe_lock);
  			list_add_tail(&req->r_unsafe_dir_item,
  				      &ci->i_unsafe_dirops);
  			spin_unlock(&ci->i_unsafe_lock);
  		}
  	}
  
  	dout("handle_reply tid %lld result %d\n", tid, result);
  	rinfo = &req->r_reply_info;
  	if (test_bit(CEPHFS_FEATURE_REPLY_ENCODING, &session->s_features))
  		err = parse_reply_info(msg, rinfo, (u64)-1);
  	else
  		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);
  	current->journal_info = req;
  	err = ceph_fill_trace(mdsc->fsc->sb, req);
  	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);
  	}
  	current->journal_info = NULL;
  	mutex_unlock(&req->r_fill_mutex);
  
  	up_read(&mdsc->snap_rwsem);
  	if (realm)
  		ceph_put_snap_realm(mdsc, realm);
  
  	if (err == 0) {
  		if (req->r_target_inode &&
  		    test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags)) {
  			struct ceph_inode_info *ci =
  				ceph_inode(req->r_target_inode);
  			spin_lock(&ci->i_unsafe_lock);
  			list_add_tail(&req->r_unsafe_target_item,
  				      &ci->i_unsafe_iops);
  			spin_unlock(&ci->i_unsafe_lock);
  		}
  
  		ceph_unreserve_caps(mdsc, &req->r_caps_reservation);
  	}
  out_err:
  	mutex_lock(&mdsc->mutex);
  	if (!test_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags)) {
  		if (err) {
  			req->r_err = err;
  		} else {
  			req->r_reply =  ceph_msg_get(msg);
  			set_bit(CEPH_MDS_R_GOT_RESULT, &req->r_req_flags);
  		}
  	} else {
  		dout("reply arrived after request %lld was aborted\n", tid);
  	}
  	mutex_unlock(&mdsc->mutex);
  
  	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_get_request(mdsc, tid);
  	if (!req) {
  		dout("forward tid %llu to mds%d - req dne\n", tid, next_mds);
  		goto out;  /* dup reply? */
  	}
  
  	if (test_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags)) {
  		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(test_bit(CEPH_MDS_R_GOT_RESULT, &req->r_req_flags));
  		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);
  }
  
  static int __decode_session_metadata(void **p, void *end,
  				     bool *blacklisted)
  {
  	/* map<string,string> */
  	u32 n;
  	bool err_str;
  	ceph_decode_32_safe(p, end, n, bad);
  	while (n-- > 0) {
  		u32 len;
  		ceph_decode_32_safe(p, end, len, bad);
  		ceph_decode_need(p, end, len, bad);
  		err_str = !strncmp(*p, "error_string", len);
  		*p += len;
  		ceph_decode_32_safe(p, end, len, bad);
  		ceph_decode_need(p, end, len, bad);
  		if (err_str && strnstr(*p, "blacklisted", len))
  			*blacklisted = true;
  		*p += len;
  	}
  	return 0;
  bad:
  	return -1;
  }
  
  /*
   * 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;
  	int mds = session->s_mds;
  	int msg_version = le16_to_cpu(msg->hdr.version);
  	void *p = msg->front.iov_base;
  	void *end = p + msg->front.iov_len;
  	struct ceph_mds_session_head *h;
  	u32 op;
  	u64 seq, features = 0;
  	int wake = 0;
  	bool blacklisted = false;
  
  	/* decode */
  	ceph_decode_need(&p, end, sizeof(*h), bad);
  	h = p;
  	p += sizeof(*h);
  
  	op = le32_to_cpu(h->op);
  	seq = le64_to_cpu(h->seq);
  
  	if (msg_version >= 3) {
  		u32 len;
  		/* version >= 2, metadata */
  		if (__decode_session_metadata(&p, end, &blacklisted) < 0)
  			goto bad;
  		/* version >= 3, feature bits */
  		ceph_decode_32_safe(&p, end, len, bad);
  		ceph_decode_64_safe(&p, end, features, bad);
  		p += len - sizeof(features);
  	}
  
  	mutex_lock(&mdsc->mutex);
  	if (op == CEPH_SESSION_CLOSE) {
  		get_session(session);
  		__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;
  		session->s_features = features;
  		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:
  		ceph_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, FORCE_RO);
  		break;
  
  	case CEPH_SESSION_REJECT:
  		WARN_ON(session->s_state != CEPH_MDS_SESSION_OPENING);
  		pr_info("mds%d rejected session\n", session->s_mds);
  		session->s_state = CEPH_MDS_SESSION_REJECTED;
  		cleanup_session_requests(mdsc, session);
  		remove_session_caps(session);
  		if (blacklisted)
  			mdsc->fsc->blacklisted = true;
  		wake = 2; /* for good measure */
  		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);
  	}
  	if (op == CEPH_SESSION_CLOSE)
  		ceph_put_mds_session(session);
  	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 (test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags))
  			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);
  }
  
  static int send_reconnect_partial(struct ceph_reconnect_state *recon_state)
  {
  	struct ceph_msg *reply;
  	struct ceph_pagelist *_pagelist;
  	struct page *page;
  	__le32 *addr;
  	int err = -ENOMEM;
  
  	if (!recon_state->allow_multi)
  		return -ENOSPC;
  
  	/* can't handle message that contains both caps and realm */
  	BUG_ON(!recon_state->nr_caps == !recon_state->nr_realms);
  
  	/* pre-allocate new pagelist */
  	_pagelist = ceph_pagelist_alloc(GFP_NOFS);
  	if (!_pagelist)
  		return -ENOMEM;
  
  	reply = ceph_msg_new2(CEPH_MSG_CLIENT_RECONNECT, 0, 1, GFP_NOFS, false);
  	if (!reply)
  		goto fail_msg;
  
  	/* placeholder for nr_caps */
  	err = ceph_pagelist_encode_32(_pagelist, 0);
  	if (err < 0)
  		goto fail;
  
  	if (recon_state->nr_caps) {
  		/* currently encoding caps */
  		err = ceph_pagelist_encode_32(recon_state->pagelist, 0);
  		if (err)
  			goto fail;
  	} else {
  		/* placeholder for nr_realms (currently encoding relams) */
  		err = ceph_pagelist_encode_32(_pagelist, 0);
  		if (err < 0)
  			goto fail;
  	}
  
  	err = ceph_pagelist_encode_8(recon_state->pagelist, 1);
  	if (err)
  		goto fail;
  
  	page = list_first_entry(&recon_state->pagelist->head, struct page, lru);
  	addr = kmap_atomic(page);
  	if (recon_state->nr_caps) {
  		/* currently encoding caps */
  		*addr = cpu_to_le32(recon_state->nr_caps);
  	} else {
  		/* currently encoding relams */
  		*(addr + 1) = cpu_to_le32(recon_state->nr_realms);
  	}
  	kunmap_atomic(addr);
  
  	reply->hdr.version = cpu_to_le16(5);
  	reply->hdr.compat_version = cpu_to_le16(4);
  
  	reply->hdr.data_len = cpu_to_le32(recon_state->pagelist->length);
  	ceph_msg_data_add_pagelist(reply, recon_state->pagelist);
  
  	ceph_con_send(&recon_state->session->s_con, reply);
  	ceph_pagelist_release(recon_state->pagelist);
  
  	recon_state->pagelist = _pagelist;
  	recon_state->nr_caps = 0;
  	recon_state->nr_realms = 0;
  	recon_state->msg_version = 5;
  	return 0;
  fail:
  	ceph_msg_put(reply);
  fail_msg:
  	ceph_pagelist_release(_pagelist);
  	return err;
  }
  
  /*
   * 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;
  	struct ceph_inode_info *ci = cap->ci;
  	struct ceph_reconnect_state *recon_state = arg;
  	struct ceph_pagelist *pagelist = recon_state->pagelist;
  	int err;
  	u64 snap_follows;
  
  	dout(" adding %p ino %llx.%llx cap %p %lld %s\n",
  	     inode, ceph_vinop(inode), cap, cap->cap_id,
  	     ceph_cap_string(cap->issued));
  
  	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->msg_version >= 2) {
  		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 = 0;
  		rec.v2.flock_len = (__force __le32)
  			((ci->i_ceph_flags & CEPH_I_ERROR_FILELOCK) ? 0 : 1);
  	} 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_timespec64(&rec.v1.mtime, &inode->i_mtime);
  		ceph_encode_timespec64(&rec.v1.atime, &inode->i_atime);
  		rec.v1.snaprealm = cpu_to_le64(ci->i_snap_realm->ino);
  		rec.v1.pathbase = 0;
  	}
  
  	if (list_empty(&ci->i_cap_snaps)) {
  		snap_follows = ci->i_head_snapc ? ci->i_head_snapc->seq : 0;
  	} else {
  		struct ceph_cap_snap *capsnap =
  			list_first_entry(&ci->i_cap_snaps,
  					 struct ceph_cap_snap, ci_item);
  		snap_follows = capsnap->follows;
  	}
  	spin_unlock(&ci->i_ceph_lock);
  
  	if (recon_state->msg_version >= 2) {
  		int num_fcntl_locks, num_flock_locks;
  		struct ceph_filelock *flocks = NULL;
  		size_t struct_len, total_len = sizeof(u64);
  		u8 struct_v = 0;
  
  encode_again:
  		if (rec.v2.flock_len) {
  			ceph_count_locks(inode, &num_fcntl_locks, &num_flock_locks);
  		} else {
  			num_fcntl_locks = 0;
  			num_flock_locks = 0;
  		}
  		if (num_fcntl_locks + num_flock_locks > 0) {
  			flocks = kmalloc_array(num_fcntl_locks + num_flock_locks,
  					       sizeof(struct ceph_filelock),
  					       GFP_NOFS);
  			if (!flocks) {
  				err = -ENOMEM;
  				goto out_err;
  			}
  			err = ceph_encode_locks_to_buffer(inode, flocks,
  							  num_fcntl_locks,
  							  num_flock_locks);
  			if (err) {
  				kfree(flocks);
  				flocks = NULL;
  				if (err == -ENOSPC)
  					goto encode_again;
  				goto out_err;
  			}
  		} else {
  			kfree(flocks);
  			flocks = NULL;
  		}
  
  		if (recon_state->msg_version >= 3) {
  			/* version, compat_version and struct_len */
  			total_len += 2 * sizeof(u8) + sizeof(u32);
  			struct_v = 2;
  		}
  		/*
  		 * number of encoded locks is stable, so copy to pagelist
  		 */
  		struct_len = 2 * sizeof(u32) +
  			    (num_fcntl_locks + num_flock_locks) *
  			    sizeof(struct ceph_filelock);
  		rec.v2.flock_len = cpu_to_le32(struct_len);
  
  		struct_len += sizeof(u32) + sizeof(rec.v2);
  
  		if (struct_v >= 2)
  			struct_len += sizeof(u64); /* snap_follows */
  
  		total_len += struct_len;
  
  		if (pagelist->length + total_len > RECONNECT_MAX_SIZE) {
  			err = send_reconnect_partial(recon_state);
  			if (err)
  				goto out_freeflocks;
  			pagelist = recon_state->pagelist;
  		}
  
  		err = ceph_pagelist_reserve(pagelist, total_len);
  		if (err)
  			goto out_freeflocks;
  
  		ceph_pagelist_encode_64(pagelist, ceph_ino(inode));
  		if (recon_state->msg_version >= 3) {
  			ceph_pagelist_encode_8(pagelist, struct_v);
  			ceph_pagelist_encode_8(pagelist, 1);
  			ceph_pagelist_encode_32(pagelist, struct_len);
  		}
  		ceph_pagelist_encode_string(pagelist, NULL, 0);
  		ceph_pagelist_append(pagelist, &rec, sizeof(rec.v2));
  		ceph_locks_to_pagelist(flocks, pagelist,
  				       num_fcntl_locks, num_flock_locks);
  		if (struct_v >= 2)
  			ceph_pagelist_encode_64(pagelist, snap_follows);
  out_freeflocks:
  		kfree(flocks);
  	} else {
  		u64 pathbase = 0;
  		int pathlen = 0;
  		char *path = NULL;
  		struct dentry *dentry;
  
  		dentry = d_find_alias(inode);
  		if (dentry) {
  			path = ceph_mdsc_build_path(dentry,
  						&pathlen, &pathbase, 0);
  			dput(dentry);
  			if (IS_ERR(path)) {
  				err = PTR_ERR(path);
  				goto out_err;
  			}
  			rec.v1.pathbase = cpu_to_le64(pathbase);
  		}
  
  		err = ceph_pagelist_reserve(pagelist,
  					    sizeof(u64) + sizeof(u32) +
  					    pathlen + sizeof(rec.v1));
  		if (err) {
  			goto out_freepath;
  		}
  
  		ceph_pagelist_encode_64(pagelist, ceph_ino(inode));
  		ceph_pagelist_encode_string(pagelist, path, pathlen);
  		ceph_pagelist_append(pagelist, &rec, sizeof(rec.v1));
  out_freepath:
  		ceph_mdsc_free_path(path, pathlen);
  	}
  
  out_err:
  	if (err >= 0)
  		recon_state->nr_caps++;
  	return err;
  }
  
  static int encode_snap_realms(struct ceph_mds_client *mdsc,
  			      struct ceph_reconnect_state *recon_state)
  {
  	struct rb_node *p;
  	struct ceph_pagelist *pagelist = recon_state->pagelist;
  	int err = 0;
  
  	if (recon_state->msg_version >= 4) {
  		err = ceph_pagelist_encode_32(pagelist, mdsc->num_snap_realms);
  		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;
  
  		if (recon_state->msg_version >= 4) {
  			size_t need = sizeof(u8) * 2 + sizeof(u32) +
  				      sizeof(sr_rec);
  
  			if (pagelist->length + need > RECONNECT_MAX_SIZE) {
  				err = send_reconnect_partial(recon_state);
  				if (err)
  					goto fail;
  				pagelist = recon_state->pagelist;
  			}
  
  			err = ceph_pagelist_reserve(pagelist, need);
  			if (err)
  				goto fail;
  
  			ceph_pagelist_encode_8(pagelist, 1);
  			ceph_pagelist_encode_8(pagelist, 1);
  			ceph_pagelist_encode_32(pagelist, sizeof(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;
  
  		recon_state->nr_realms++;
  	}
  fail:
  	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;
  	int mds = session->s_mds;
  	int err = -ENOMEM;
  	struct ceph_reconnect_state recon_state = {
  		.session = session,
  	};
  	LIST_HEAD(dispose);
  
  	pr_info("mds%d reconnect start\n", mds);
  
  	recon_state.pagelist = ceph_pagelist_alloc(GFP_NOFS);
  	if (!recon_state.pagelist)
  		goto fail_nopagelist;
  
  	reply = ceph_msg_new2(CEPH_MSG_CLIENT_RECONNECT, 0, 1, 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 */
  	detach_cap_releases(session, &dispose);
  	spin_unlock(&session->s_cap_lock);
  	dispose_cap_releases(mdsc, &dispose);
  
  	/* 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);
  
  	ceph_early_kick_flushing_caps(mdsc, session);
  
  	down_read(&mdsc->snap_rwsem);
  
  	/* placeholder for nr_caps */
  	err = ceph_pagelist_encode_32(recon_state.pagelist, 0);
  	if (err)
  		goto fail;
  
  	if (test_bit(CEPHFS_FEATURE_MULTI_RECONNECT, &session->s_features)) {
  		recon_state.msg_version = 3;
  		recon_state.allow_multi = true;
  	} else if (session->s_con.peer_features & CEPH_FEATURE_MDSENC) {
  		recon_state.msg_version = 3;
  	} else {
  		recon_state.msg_version = 2;
  	}
  	/* trsaverse this session's caps */
  	err = ceph_iterate_session_caps(session, encode_caps_cb, &recon_state);
  
  	spin_lock(&session->s_cap_lock);
  	session->s_cap_reconnect = 0;
  	spin_unlock(&session->s_cap_lock);
  
  	if (err < 0)
  		goto fail;
  
  	/* check if all realms can be encoded into current message */
  	if (mdsc->num_snap_realms) {
  		size_t total_len =
  			recon_state.pagelist->length +
  			mdsc->num_snap_realms *
  			sizeof(struct ceph_mds_snaprealm_reconnect);
  		if (recon_state.msg_version >= 4) {
  			/* number of realms */
  			total_len += sizeof(u32);
  			/* version, compat_version and struct_len */
  			total_len += mdsc->num_snap_realms *
  				     (2 * sizeof(u8) + sizeof(u32));
  		}
  		if (total_len > RECONNECT_MAX_SIZE) {
  			if (!recon_state.allow_multi) {
  				err = -ENOSPC;
  				goto fail;
  			}
  			if (recon_state.nr_caps) {
  				err = send_reconnect_partial(&recon_state);
  				if (err)
  					goto fail;
  			}
  			recon_state.msg_version = 5;
  		}
  	}
  
  	err = encode_snap_realms(mdsc, &recon_state);
  	if (err < 0)
  		goto fail;
  
  	if (recon_state.msg_version >= 5) {
  		err = ceph_pagelist_encode_8(recon_state.pagelist, 0);
  		if (err < 0)
  			goto fail;
  	}
  
  	if (recon_state.nr_caps || recon_state.nr_realms) {
  		struct page *page =
  			list_first_entry(&recon_state.pagelist->head,
  					struct page, lru);
  		__le32 *addr = kmap_atomic(page);
  		if (recon_state.nr_caps) {
  			WARN_ON(recon_state.nr_realms != mdsc->num_snap_realms);
  			*addr = cpu_to_le32(recon_state.nr_caps);
  		} else if (recon_state.msg_version >= 4) {
  			*(addr + 1) = cpu_to_le32(recon_state.nr_realms);
  		}
  		kunmap_atomic(addr);
  	}
  
  	reply->hdr.version = cpu_to_le16(recon_state.msg_version);
  	if (recon_state.msg_version >= 4)
  		reply->hdr.compat_version = cpu_to_le16(4);
  
  	reply->hdr.data_len = cpu_to_le32(recon_state.pagelist->length);
  	ceph_msg_data_add_pagelist(reply, recon_state.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);
  	ceph_pagelist_release(recon_state.pagelist);
  	return;
  
  fail:
  	ceph_msg_put(reply);
  	up_read(&mdsc->snap_rwsem);
  	mutex_unlock(&session->s_mutex);
  fail_nomsg:
  	ceph_pagelist_release(recon_state.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_num_mds && i < mdsc->max_sessions; i++) {
  		if (!mdsc->sessions[i])
  			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_num_mds) {
  			/* force close session for stopped mds */
  			get_session(s);
  			__unregister_session(mdsc, s);
  			__wake_requests(mdsc, &s->s_waiting);
  			mutex_unlock(&mdsc->mutex);
  
  			mutex_lock(&s->s_mutex);
  			cleanup_session_requests(mdsc, s);
  			remove_session_caps(s);
  			mutex_unlock(&s->s_mutex);
  
  			ceph_put_mds_session(s);
  
  			mutex_lock(&mdsc->mutex);
  			kick_requests(mdsc, i);
  			continue;
  		}
  
  		if (memcmp(ceph_mdsmap_get_addr(oldmap, i),
  			   ceph_mdsmap_get_addr(newmap, i),
  			   sizeof(struct ceph_entity_addr))) {
  			/* 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, RECONNECT);
  		}
  	}
  
  	for (i = 0; i < newmap->m_num_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.len = get_unaligned_le32(h + 1);
  	if (msg->front.iov_len < sizeof(*h) + sizeof(u32) + dname.len)
  		goto bad;
  	dname.name = (void *)(h + 1) + sizeof(u32);
  
  	/* 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) {
  		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(parent, 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;
  			di->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:
  	mutex_unlock(&session->s_mutex);
  	/* avoid calling iput_final() in mds dispatch threads */
  	ceph_async_iput(inode);
  	return;
  
  bad:
  	pr_err("corrupt lease message\n");
  	ceph_msg_dump(msg);
  }
  
  void ceph_mdsc_lease_send_msg(struct ceph_mds_session *session,
  			      struct dentry *dentry, char action,
  			      u32 seq)
  {
  	struct ceph_msg *msg;
  	struct ceph_mds_lease *lease;
  	struct inode *dir;
  	int len = sizeof(*lease) + sizeof(u32) + NAME_MAX;
  
  	dout("lease_send_msg identry %p %s to mds%d\n",
  	     dentry, ceph_lease_op_name(action), session->s_mds);
  
  	msg = ceph_msg_new(CEPH_MSG_CLIENT_LEASE, len, GFP_NOFS, false);
  	if (!msg)
  		return;
  	lease = msg->front.iov_base;
  	lease->action = action;
  	lease->seq = cpu_to_le32(seq);
  
  	spin_lock(&dentry->d_lock);
  	dir = d_inode(dentry->d_parent);
  	lease->ino = cpu_to_le64(ceph_ino(dir));
  	lease->first = lease->last = cpu_to_le64(ceph_snap(dir));
  
  	put_unaligned_le32(dentry->d_name.len, lease + 1);
  	memcpy((void *)(lease + 1) + 4,
  	       dentry->d_name.name, dentry->d_name.len);
  	spin_unlock(&dentry->d_lock);
  	/*
  	 * 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);
  }
  
  /*
   * lock unlock sessions, to wait ongoing session activities
   */
  static void lock_unlock_sessions(struct ceph_mds_client *mdsc)
  {
  	int i;
  
  	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);
  }
  
  static void maybe_recover_session(struct ceph_mds_client *mdsc)
  {
  	struct ceph_fs_client *fsc = mdsc->fsc;
  
  	if (!ceph_test_mount_opt(fsc, CLEANRECOVER))
  		return;
  
  	if (READ_ONCE(fsc->mount_state) != CEPH_MOUNT_MOUNTED)
  		return;
  
  	if (!READ_ONCE(fsc->blacklisted))
  		return;
  
  	if (fsc->last_auto_reconnect &&
  	    time_before(jiffies, fsc->last_auto_reconnect + HZ * 60 * 30))
  		return;
  
  	pr_info("auto reconnect after blacklisted\n");
  	fsc->last_auto_reconnect = jiffies;
  	ceph_force_reconnect(fsc->sb);
  }
  
  /*
   * 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");
  
  	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)
  			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_NEW ||
  		    s->s_state == CEPH_MDS_SESSION_RESTARTING ||
  		    s->s_state == CEPH_MDS_SESSION_REJECTED) {
  			/* 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);
  		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);
  
  	ceph_check_delayed_caps(mdsc);
  
  	ceph_queue_cap_reclaim_work(mdsc);
  
  	ceph_trim_snapid_map(mdsc);
  
  	maybe_recover_session(mdsc);
  
  	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;
  	mutex_init(&mdsc->mutex);
  	mdsc->mdsmap = kzalloc(sizeof(*mdsc->mdsmap), GFP_NOFS);
  	if (!mdsc->mdsmap) {
  		kfree(mdsc);
  		return -ENOMEM;
  	}
  
  	fsc->mdsc = mdsc;
  	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;
  	atomic64_set(&mdsc->quotarealms_count, 0);
  	mdsc->quotarealms_inodes = RB_ROOT;
  	mutex_init(&mdsc->quotarealms_inodes_mutex);
  	mdsc->last_snap_seq = 0;
  	init_rwsem(&mdsc->snap_rwsem);
  	mdsc->snap_realms = RB_ROOT;
  	INIT_LIST_HEAD(&mdsc->snap_empty);
  	mdsc->num_snap_realms = 0;
  	spin_lock_init(&mdsc->snap_empty_lock);
  	mdsc->last_tid = 0;
  	mdsc->oldest_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->last_cap_flush_tid = 1;
  	INIT_LIST_HEAD(&mdsc->cap_flush_list);
  	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);
  	INIT_WORK(&mdsc->cap_reclaim_work, ceph_cap_reclaim_work);
  	atomic_set(&mdsc->cap_reclaim_pending, 0);
  
  	spin_lock_init(&mdsc->dentry_list_lock);
  	INIT_LIST_HEAD(&mdsc->dentry_leases);
  	INIT_LIST_HEAD(&mdsc->dentry_dir_leases);
  
  	ceph_caps_init(mdsc);
  	ceph_adjust_caps_max_min(mdsc, fsc->mount_options);
  
  	spin_lock_init(&mdsc->snapid_map_lock);
  	mdsc->snapid_map_tree = RB_ROOT;
  	INIT_LIST_HEAD(&mdsc->snapid_map_lru);
  
  	init_rwsem(&mdsc->pool_perm_rwsem);
  	mdsc->pool_perm_tree = RB_ROOT;
  
  	strscpy(mdsc->nodename, utsname()->nodename,
  		sizeof(mdsc->nodename));
  	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_options *opts = mdsc->fsc->client->options;
  	struct ceph_mds_request *req;
  
  	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,
  				    ceph_timeout_jiffies(opts->mount_timeout));
  
  		/* 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);
  			list_del_init(&req->r_wait);
  			__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;
  
  	lock_unlock_sessions(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();
  
  	ceph_cleanup_quotarealms_inodes(mdsc);
  }
  
  /*
   * wait for all write mds requests to flush.
   */
  static void wait_unsafe_requests(struct ceph_mds_client *mdsc, u64 want_tid)
  {
  	struct ceph_mds_request *req = NULL, *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_SETFILELOCK &&
  		    (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 (READ_ONCE(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->last_cap_flush_tid;
  	if (!list_empty(&mdsc->cap_flush_list)) {
  		struct ceph_cap_flush *cf =
  			list_last_entry(&mdsc->cap_flush_list,
  					struct ceph_cap_flush, g_list);
  		cf->wake = true;
  	}
  	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, int skipped)
  {
  	if (READ_ONCE(mdsc->fsc->mount_state) == CEPH_MOUNT_SHUTDOWN)
  		return true;
  	return atomic_read(&mdsc->num_sessions) <= skipped;
  }
  
  /*
   * called after sb is ro.
   */
  void ceph_mdsc_close_sessions(struct ceph_mds_client *mdsc)
  {
  	struct ceph_options *opts = mdsc->fsc->client->options;
  	struct ceph_mds_session *session;
  	int i;
  	int skipped = 0;
  
  	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);
  		if (__close_session(mdsc, session) <= 0)
  			skipped++;
  		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, skipped),
  			   ceph_timeout_jiffies(opts->mount_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_snapid_map(mdsc);
  	ceph_cleanup_empty_realms(mdsc);
  
  	cancel_work_sync(&mdsc->cap_reclaim_work);
  	cancel_delayed_work_sync(&mdsc->delayed_work); /* cancel timer */
  
  	dout("stopped\n");
  }
  
  void ceph_mdsc_force_umount(struct ceph_mds_client *mdsc)
  {
  	struct ceph_mds_session *session;
  	int mds;
  
  	dout("force umount\n");
  
  	mutex_lock(&mdsc->mutex);
  	for (mds = 0; mds < mdsc->max_sessions; mds++) {
  		session = __ceph_lookup_mds_session(mdsc, mds);
  		if (!session)
  			continue;
  
  		if (session->s_state == CEPH_MDS_SESSION_REJECTED)
  			__unregister_session(mdsc, session);
  		__wake_requests(mdsc, &session->s_waiting);
  		mutex_unlock(&mdsc->mutex);
  
  		mutex_lock(&session->s_mutex);
  		__close_session(mdsc, session);
  		if (session->s_state == CEPH_MDS_SESSION_CLOSING) {
  			cleanup_session_requests(mdsc, session);
  			remove_session_caps(session);
  		}
  		mutex_unlock(&session->s_mutex);
  		ceph_put_mds_session(session);
  
  		mutex_lock(&mdsc->mutex);
  		kick_requests(mdsc, mds);
  	}
  	__wake_requests(mdsc, &mdsc->waiting_for_map);
  	mutex_unlock(&mdsc->mutex);
  }
  
  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);
  	ceph_pool_perm_destroy(mdsc);
  }
  
  void ceph_mdsc_destroy(struct ceph_fs_client *fsc)
  {
  	struct ceph_mds_client *mdsc = fsc->mdsc;
  	dout("mdsc_destroy %p\n", mdsc);
  
  	if (!mdsc)
  		return;
  
  	/* flush out any connection work with references to us */
  	ceph_msgr_flush();
  
  	ceph_mdsc_stop(mdsc);
  
  	fsc->mdsc = NULL;
  	kfree(mdsc);
  	dout("mdsc_destroy %p done\n", mdsc);
  }
  
  void ceph_mdsc_handle_fsmap(struct ceph_mds_client *mdsc, struct ceph_msg *msg)
  {
  	struct ceph_fs_client *fsc = mdsc->fsc;
  	const char *mds_namespace = fsc->mount_options->mds_namespace;
  	void *p = msg->front.iov_base;
  	void *end = p + msg->front.iov_len;
  	u32 epoch;
  	u32 map_len;
  	u32 num_fs;
  	u32 mount_fscid = (u32)-1;
  	u8 struct_v, struct_cv;
  	int err = -EINVAL;
  
  	ceph_decode_need(&p, end, sizeof(u32), bad);
  	epoch = ceph_decode_32(&p);
  
  	dout("handle_fsmap epoch %u\n", epoch);
  
  	ceph_decode_need(&p, end, 2 + sizeof(u32), bad);
  	struct_v = ceph_decode_8(&p);
  	struct_cv = ceph_decode_8(&p);
  	map_len = ceph_decode_32(&p);
  
  	ceph_decode_need(&p, end, sizeof(u32) * 3, bad);
  	p += sizeof(u32) * 2; /* skip epoch and legacy_client_fscid */
  
  	num_fs = ceph_decode_32(&p);
  	while (num_fs-- > 0) {
  		void *info_p, *info_end;
  		u32 info_len;
  		u8 info_v, info_cv;
  		u32 fscid, namelen;
  
  		ceph_decode_need(&p, end, 2 + sizeof(u32), bad);
  		info_v = ceph_decode_8(&p);
  		info_cv = ceph_decode_8(&p);
  		info_len = ceph_decode_32(&p);
  		ceph_decode_need(&p, end, info_len, bad);
  		info_p = p;
  		info_end = p + info_len;
  		p = info_end;
  
  		ceph_decode_need(&info_p, info_end, sizeof(u32) * 2, bad);
  		fscid = ceph_decode_32(&info_p);
  		namelen = ceph_decode_32(&info_p);
  		ceph_decode_need(&info_p, info_end, namelen, bad);
  
  		if (mds_namespace &&
  		    strlen(mds_namespace) == namelen &&
  		    !strncmp(mds_namespace, (char *)info_p, namelen)) {
  			mount_fscid = fscid;
  			break;
  		}
  	}
  
  	ceph_monc_got_map(&fsc->client->monc, CEPH_SUB_FSMAP, epoch);
  	if (mount_fscid != (u32)-1) {
  		fsc->client->monc.fs_cluster_id = mount_fscid;
  		ceph_monc_want_map(&fsc->client->monc, CEPH_SUB_MDSMAP,
  				   0, true);
  		ceph_monc_renew_subs(&fsc->client->monc);
  	} else {
  		err = -ENOENT;
  		goto err_out;
  	}
  	return;
  
  bad:
  	pr_err("error decoding fsmap\n");
  err_out:
  	mutex_lock(&mdsc->mutex);
  	mdsc->mdsmap_err = err;
  	__wake_requests(mdsc, &mdsc->waiting_for_map);
  	mutex_unlock(&mdsc->mutex);
  }
  
  /*
   * handle mds map update.
   */
  void ceph_mdsc_handle_mdsmap(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? */
  	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->max_file_size = min((loff_t)mdsc->mdsmap->m_max_file_size,
  					MAX_LFS_FILESIZE);
  
  	__wake_requests(mdsc, &mdsc->waiting_for_map);
  	ceph_monc_got_map(&mdsc->fsc->client->monc, CEPH_SUB_MDSMAP,
  			  mdsc->mdsmap->m_epoch);
  
  	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, refcount_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, refcount_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_mdsmap(mdsc, msg);
  		break;
  	case CEPH_MSG_FS_MAP_USER:
  		ceph_mdsc_handle_fsmap(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;
  	case CEPH_MSG_CLIENT_QUOTA:
  		ceph_handle_quota(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(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 add_authorizer_challenge(struct ceph_connection *con,
  				    void *challenge_buf, int challenge_buf_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_add_authorizer_challenge(ac, s->s_auth.authorizer,
  					    challenge_buf, challenge_buf_len);
  }
  
  static int verify_authorizer_reply(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;
  
  	return ceph_auth_verify_authorizer_reply(ac, s->s_auth.authorizer);
  }
  
  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 mds_sign_message(struct ceph_msg *msg)
  {
         struct ceph_mds_session *s = msg->con->private;
         struct ceph_auth_handshake *auth = &s->s_auth;
  
         return ceph_auth_sign_message(auth, msg);
  }
  
  static int mds_check_message_signature(struct ceph_msg *msg)
  {
         struct ceph_mds_session *s = msg->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,
  	.add_authorizer_challenge = add_authorizer_challenge,
  	.verify_authorizer_reply = verify_authorizer_reply,
  	.invalidate_authorizer = invalidate_authorizer,
  	.peer_reset = peer_reset,
  	.alloc_msg = mds_alloc_msg,
  	.sign_message = mds_sign_message,
  	.check_message_signature = mds_check_message_signature,
  };
  
  /* eof */
  