#include <linux/ceph/ceph_debug.h>

  
  #include <linux/fs.h>
  #include <linux/kernel.h>
  #include <linux/sched.h>

  #include <linux/slab.h>

  #include <linux/vmalloc.h>
  #include <linux/wait.h>

  #include <linux/writeback.h>

  
  #include "super.h"

  #include "mds_client.h"
  #include <linux/ceph/decode.h>
  #include <linux/ceph/messenger.h>

  
  /*
   * Capability management
   *
   * The Ceph metadata servers control client access to inode metadata
   * and file data by issuing capabilities, granting clients permission
   * to read and/or write both inode field and file data to OSDs
   * (storage nodes).  Each capability consists of a set of bits
   * indicating which operations are allowed.
   *
   * If the client holds a *_SHARED cap, the client has a coherent value
   * that can be safely read from the cached inode.
   *
   * In the case of a *_EXCL (exclusive) or FILE_WR capabilities, the
   * client is allowed to change inode attributes (e.g., file size,
   * mtime), note its dirty state in the ceph_cap, and asynchronously
   * flush that metadata change to the MDS.
   *
   * In the event of a conflicting operation (perhaps by another
   * client), the MDS will revoke the conflicting client capabilities.
   *
   * In order for a client to cache an inode, it must hold a capability
   * with at least one MDS server.  When inodes are released, release
   * notifications are batched and periodically sent en masse to the MDS
   * cluster to release server state.
   */
  
  
  /*
   * Generate readable cap strings for debugging output.
   */
  #define MAX_CAP_STR 20
  static char cap_str[MAX_CAP_STR][40];
  static DEFINE_SPINLOCK(cap_str_lock);
  static int last_cap_str;
  
  static char *gcap_string(char *s, int c)
  {
  	if (c & CEPH_CAP_GSHARED)
  		*s++ = 's';
  	if (c & CEPH_CAP_GEXCL)
  		*s++ = 'x';
  	if (c & CEPH_CAP_GCACHE)
  		*s++ = 'c';
  	if (c & CEPH_CAP_GRD)
  		*s++ = 'r';
  	if (c & CEPH_CAP_GWR)
  		*s++ = 'w';
  	if (c & CEPH_CAP_GBUFFER)
  		*s++ = 'b';
  	if (c & CEPH_CAP_GLAZYIO)
  		*s++ = 'l';
  	return s;
  }
  
  const char *ceph_cap_string(int caps)
  {
  	int i;
  	char *s;
  	int c;
  
  	spin_lock(&cap_str_lock);
  	i = last_cap_str++;
  	if (last_cap_str == MAX_CAP_STR)
  		last_cap_str = 0;
  	spin_unlock(&cap_str_lock);
  
  	s = cap_str[i];
  
  	if (caps & CEPH_CAP_PIN)
  		*s++ = 'p';
  
  	c = (caps >> CEPH_CAP_SAUTH) & 3;
  	if (c) {
  		*s++ = 'A';
  		s = gcap_string(s, c);
  	}
  
  	c = (caps >> CEPH_CAP_SLINK) & 3;
  	if (c) {
  		*s++ = 'L';
  		s = gcap_string(s, c);
  	}
  
  	c = (caps >> CEPH_CAP_SXATTR) & 3;
  	if (c) {
  		*s++ = 'X';
  		s = gcap_string(s, c);
  	}
  
  	c = caps >> CEPH_CAP_SFILE;
  	if (c) {
  		*s++ = 'F';
  		s = gcap_string(s, c);
  	}
  
  	if (s == cap_str[i])
  		*s++ = '-';
  	*s = 0;
  	return cap_str[i];
  }

  void ceph_caps_init(struct ceph_mds_client *mdsc)

  {

  	INIT_LIST_HEAD(&mdsc->caps_list);
  	spin_lock_init(&mdsc->caps_list_lock);

  }

  void ceph_caps_finalize(struct ceph_mds_client *mdsc)

  {
  	struct ceph_cap *cap;

  	spin_lock(&mdsc->caps_list_lock);
  	while (!list_empty(&mdsc->caps_list)) {
  		cap = list_first_entry(&mdsc->caps_list,
  				       struct ceph_cap, caps_item);

  		list_del(&cap->caps_item);
  		kmem_cache_free(ceph_cap_cachep, cap);
  	}

  	mdsc->caps_total_count = 0;
  	mdsc->caps_avail_count = 0;
  	mdsc->caps_use_count = 0;
  	mdsc->caps_reserve_count = 0;
  	mdsc->caps_min_count = 0;
  	spin_unlock(&mdsc->caps_list_lock);

  }

  void ceph_adjust_min_caps(struct ceph_mds_client *mdsc, int delta)

  {

  	spin_lock(&mdsc->caps_list_lock);
  	mdsc->caps_min_count += delta;
  	BUG_ON(mdsc->caps_min_count < 0);
  	spin_unlock(&mdsc->caps_list_lock);

  }

  int ceph_reserve_caps(struct ceph_mds_client *mdsc,
  		      struct ceph_cap_reservation *ctx, int need)

  {
  	int i;
  	struct ceph_cap *cap;
  	int have;
  	int alloc = 0;
  	LIST_HEAD(newcaps);
  	int ret = 0;
  
  	dout("reserve caps ctx=%p need=%d
  ", ctx, need);
  
  	/* first reserve any caps that are already allocated */

  	spin_lock(&mdsc->caps_list_lock);
  	if (mdsc->caps_avail_count >= need)

  		have = need;
  	else

  		have = mdsc->caps_avail_count;
  	mdsc->caps_avail_count -= have;
  	mdsc->caps_reserve_count += have;
  	BUG_ON(mdsc->caps_total_count != mdsc->caps_use_count +
  					 mdsc->caps_reserve_count +
  					 mdsc->caps_avail_count);
  	spin_unlock(&mdsc->caps_list_lock);

  
  	for (i = have; i < need; i++) {
  		cap = kmem_cache_alloc(ceph_cap_cachep, GFP_NOFS);
  		if (!cap) {
  			ret = -ENOMEM;
  			goto out_alloc_count;
  		}
  		list_add(&cap->caps_item, &newcaps);
  		alloc++;
  	}
  	BUG_ON(have + alloc != need);

  	spin_lock(&mdsc->caps_list_lock);
  	mdsc->caps_total_count += alloc;
  	mdsc->caps_reserve_count += alloc;
  	list_splice(&newcaps, &mdsc->caps_list);

  	BUG_ON(mdsc->caps_total_count != mdsc->caps_use_count +
  					 mdsc->caps_reserve_count +
  					 mdsc->caps_avail_count);
  	spin_unlock(&mdsc->caps_list_lock);

  
  	ctx->count = need;
  	dout("reserve caps ctx=%p %d = %d used + %d resv + %d avail
  ",

  	     ctx, mdsc->caps_total_count, mdsc->caps_use_count,
  	     mdsc->caps_reserve_count, mdsc->caps_avail_count);

  	return 0;
  
  out_alloc_count:
  	/* we didn't manage to reserve as much as we needed */
  	pr_warning("reserve caps ctx=%p ENOMEM need=%d got=%d
  ",
  		   ctx, need, have);
  	return ret;
  }

  int ceph_unreserve_caps(struct ceph_mds_client *mdsc,
  			struct ceph_cap_reservation *ctx)

  {
  	dout("unreserve caps ctx=%p count=%d
  ", ctx, ctx->count);
  	if (ctx->count) {

  		spin_lock(&mdsc->caps_list_lock);
  		BUG_ON(mdsc->caps_reserve_count < ctx->count);
  		mdsc->caps_reserve_count -= ctx->count;
  		mdsc->caps_avail_count += ctx->count;

  		ctx->count = 0;
  		dout("unreserve caps %d = %d used + %d resv + %d avail
  ",

  		     mdsc->caps_total_count, mdsc->caps_use_count,
  		     mdsc->caps_reserve_count, mdsc->caps_avail_count);
  		BUG_ON(mdsc->caps_total_count != mdsc->caps_use_count +
  						 mdsc->caps_reserve_count +
  						 mdsc->caps_avail_count);
  		spin_unlock(&mdsc->caps_list_lock);

  	}
  	return 0;
  }

  static struct ceph_cap *get_cap(struct ceph_mds_client *mdsc,
  				struct ceph_cap_reservation *ctx)

  {
  	struct ceph_cap *cap = NULL;
  
  	/* temporary, until we do something about cap import/export */

  	if (!ctx) {
  		cap = kmem_cache_alloc(ceph_cap_cachep, GFP_NOFS);
  		if (cap) {

  			mdsc->caps_use_count++;
  			mdsc->caps_total_count++;

  		}
  		return cap;
  	}

  	spin_lock(&mdsc->caps_list_lock);

  	dout("get_cap ctx=%p (%d) %d = %d used + %d resv + %d avail
  ",

  	     ctx, ctx->count, mdsc->caps_total_count, mdsc->caps_use_count,
  	     mdsc->caps_reserve_count, mdsc->caps_avail_count);

  	BUG_ON(!ctx->count);

  	BUG_ON(ctx->count > mdsc->caps_reserve_count);
  	BUG_ON(list_empty(&mdsc->caps_list));

  
  	ctx->count--;

  	mdsc->caps_reserve_count--;
  	mdsc->caps_use_count++;

  	cap = list_first_entry(&mdsc->caps_list, struct ceph_cap, caps_item);

  	list_del(&cap->caps_item);

  	BUG_ON(mdsc->caps_total_count != mdsc->caps_use_count +
  	       mdsc->caps_reserve_count + mdsc->caps_avail_count);
  	spin_unlock(&mdsc->caps_list_lock);

  	return cap;
  }

  void ceph_put_cap(struct ceph_mds_client *mdsc, struct ceph_cap *cap)

  {

  	spin_lock(&mdsc->caps_list_lock);

  	dout("put_cap %p %d = %d used + %d resv + %d avail
  ",

  	     cap, mdsc->caps_total_count, mdsc->caps_use_count,
  	     mdsc->caps_reserve_count, mdsc->caps_avail_count);
  	mdsc->caps_use_count--;

  	/*

  	 * Keep some preallocated caps around (ceph_min_count), to
  	 * avoid lots of free/alloc churn.

  	 */

  	if (mdsc->caps_avail_count >= mdsc->caps_reserve_count +
  				      mdsc->caps_min_count) {
  		mdsc->caps_total_count--;

  		kmem_cache_free(ceph_cap_cachep, cap);
  	} else {

  		mdsc->caps_avail_count++;
  		list_add(&cap->caps_item, &mdsc->caps_list);

  	}

  	BUG_ON(mdsc->caps_total_count != mdsc->caps_use_count +
  	       mdsc->caps_reserve_count + mdsc->caps_avail_count);
  	spin_unlock(&mdsc->caps_list_lock);

  }

  void ceph_reservation_status(struct ceph_fs_client *fsc,

  			     int *total, int *avail, int *used, int *reserved,
  			     int *min)

  {

  	struct ceph_mds_client *mdsc = fsc->mdsc;

  	if (total)

  		*total = mdsc->caps_total_count;

  	if (avail)

  		*avail = mdsc->caps_avail_count;

  	if (used)

  		*used = mdsc->caps_use_count;

  	if (reserved)

  		*reserved = mdsc->caps_reserve_count;

  	if (min)

  		*min = mdsc->caps_min_count;

  }
  
  /*
   * Find ceph_cap for given mds, if any.
   *

   * Called with i_ceph_lock held.

   */
  static struct ceph_cap *__get_cap_for_mds(struct ceph_inode_info *ci, int mds)
  {
  	struct ceph_cap *cap;
  	struct rb_node *n = ci->i_caps.rb_node;
  
  	while (n) {
  		cap = rb_entry(n, struct ceph_cap, ci_node);
  		if (mds < cap->mds)
  			n = n->rb_left;
  		else if (mds > cap->mds)
  			n = n->rb_right;
  		else
  			return cap;
  	}
  	return NULL;
  }

  struct ceph_cap *ceph_get_cap_for_mds(struct ceph_inode_info *ci, int mds)
  {
  	struct ceph_cap *cap;

  	spin_lock(&ci->i_ceph_lock);

  	cap = __get_cap_for_mds(ci, mds);

  	spin_unlock(&ci->i_ceph_lock);

  	return cap;
  }

  /*

   * Return id of any MDS with a cap, preferably FILE_WR|BUFFER|EXCL, else -1.

   */

  static int __ceph_get_cap_mds(struct ceph_inode_info *ci)

  {
  	struct ceph_cap *cap;
  	int mds = -1;
  	struct rb_node *p;

  	/* prefer mds with WR|BUFFER|EXCL caps */

  	for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
  		cap = rb_entry(p, struct ceph_cap, ci_node);
  		mds = cap->mds;

  		if (cap->issued & (CEPH_CAP_FILE_WR |
  				   CEPH_CAP_FILE_BUFFER |
  				   CEPH_CAP_FILE_EXCL))
  			break;
  	}
  	return mds;
  }
  
  int ceph_get_cap_mds(struct inode *inode)
  {

  	struct ceph_inode_info *ci = ceph_inode(inode);

  	int mds;

  	spin_lock(&ci->i_ceph_lock);

  	mds = __ceph_get_cap_mds(ceph_inode(inode));

  	spin_unlock(&ci->i_ceph_lock);

  	return mds;
  }
  
  /*

   * Called under i_ceph_lock.

   */
  static void __insert_cap_node(struct ceph_inode_info *ci,
  			      struct ceph_cap *new)
  {
  	struct rb_node **p = &ci->i_caps.rb_node;
  	struct rb_node *parent = NULL;
  	struct ceph_cap *cap = NULL;
  
  	while (*p) {
  		parent = *p;
  		cap = rb_entry(parent, struct ceph_cap, ci_node);
  		if (new->mds < cap->mds)
  			p = &(*p)->rb_left;
  		else if (new->mds > cap->mds)
  			p = &(*p)->rb_right;
  		else
  			BUG();
  	}
  
  	rb_link_node(&new->ci_node, parent, p);
  	rb_insert_color(&new->ci_node, &ci->i_caps);
  }
  
  /*
   * (re)set cap hold timeouts, which control the delayed release
   * of unused caps back to the MDS.  Should be called on cap use.
   */
  static void __cap_set_timeouts(struct ceph_mds_client *mdsc,
  			       struct ceph_inode_info *ci)
  {

  	struct ceph_mount_options *ma = mdsc->fsc->mount_options;

  
  	ci->i_hold_caps_min = round_jiffies(jiffies +
  					    ma->caps_wanted_delay_min * HZ);
  	ci->i_hold_caps_max = round_jiffies(jiffies +
  					    ma->caps_wanted_delay_max * HZ);
  	dout("__cap_set_timeouts %p min %lu max %lu
  ", &ci->vfs_inode,
  	     ci->i_hold_caps_min - jiffies, ci->i_hold_caps_max - jiffies);
  }
  
  /*
   * (Re)queue cap at the end of the delayed cap release list.
   *
   * If I_FLUSH is set, leave the inode at the front of the list.
   *

   * Caller holds i_ceph_lock

   *    -> we take mdsc->cap_delay_lock
   */
  static void __cap_delay_requeue(struct ceph_mds_client *mdsc,
  				struct ceph_inode_info *ci)
  {
  	__cap_set_timeouts(mdsc, ci);
  	dout("__cap_delay_requeue %p flags %d at %lu
  ", &ci->vfs_inode,
  	     ci->i_ceph_flags, ci->i_hold_caps_max);
  	if (!mdsc->stopping) {
  		spin_lock(&mdsc->cap_delay_lock);
  		if (!list_empty(&ci->i_cap_delay_list)) {
  			if (ci->i_ceph_flags & CEPH_I_FLUSH)
  				goto no_change;
  			list_del_init(&ci->i_cap_delay_list);
  		}
  		list_add_tail(&ci->i_cap_delay_list, &mdsc->cap_delay_list);
  no_change:
  		spin_unlock(&mdsc->cap_delay_lock);
  	}
  }
  
  /*
   * Queue an inode for immediate writeback.  Mark inode with I_FLUSH,
   * indicating we should send a cap message to flush dirty metadata
   * asap, and move to the front of the delayed cap list.
   */
  static void __cap_delay_requeue_front(struct ceph_mds_client *mdsc,
  				      struct ceph_inode_info *ci)
  {
  	dout("__cap_delay_requeue_front %p
  ", &ci->vfs_inode);
  	spin_lock(&mdsc->cap_delay_lock);
  	ci->i_ceph_flags |= CEPH_I_FLUSH;
  	if (!list_empty(&ci->i_cap_delay_list))
  		list_del_init(&ci->i_cap_delay_list);
  	list_add(&ci->i_cap_delay_list, &mdsc->cap_delay_list);
  	spin_unlock(&mdsc->cap_delay_lock);
  }
  
  /*
   * Cancel delayed work on cap.
   *

   * Caller must hold i_ceph_lock.

   */
  static void __cap_delay_cancel(struct ceph_mds_client *mdsc,
  			       struct ceph_inode_info *ci)
  {
  	dout("__cap_delay_cancel %p
  ", &ci->vfs_inode);
  	if (list_empty(&ci->i_cap_delay_list))
  		return;
  	spin_lock(&mdsc->cap_delay_lock);
  	list_del_init(&ci->i_cap_delay_list);
  	spin_unlock(&mdsc->cap_delay_lock);
  }
  
  /*
   * Common issue checks for add_cap, handle_cap_grant.
   */
  static void __check_cap_issue(struct ceph_inode_info *ci, struct ceph_cap *cap,
  			      unsigned issued)
  {
  	unsigned had = __ceph_caps_issued(ci, NULL);
  
  	/*
  	 * Each time we receive FILE_CACHE anew, we increment
  	 * i_rdcache_gen.
  	 */

  	if ((issued & (CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_LAZYIO)) &&
  	    (had & (CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_LAZYIO)) == 0)

  		ci->i_rdcache_gen++;
  
  	/*

  	 * if we are newly issued FILE_SHARED, clear D_COMPLETE; we

  	 * don't know what happened to this directory while we didn't
  	 * have the cap.
  	 */
  	if ((issued & CEPH_CAP_FILE_SHARED) &&
  	    (had & CEPH_CAP_FILE_SHARED) == 0) {
  		ci->i_shared_gen++;

  		if (S_ISDIR(ci->vfs_inode.i_mode))
  			ceph_dir_clear_complete(&ci->vfs_inode);

  	}
  }
  
  /*
   * Add a capability under the given MDS session.
   *
   * Caller should hold session snap_rwsem (read) and s_mutex.
   *
   * @fmode is the open file mode, if we are opening a file, otherwise
   * it is < 0.  (This is so we can atomically add the cap and add an
   * open file reference to it.)
   */
  int ceph_add_cap(struct inode *inode,
  		 struct ceph_mds_session *session, u64 cap_id,
  		 int fmode, unsigned issued, unsigned wanted,
  		 unsigned seq, unsigned mseq, u64 realmino, int flags,
  		 struct ceph_cap_reservation *caps_reservation)
  {

  	struct ceph_mds_client *mdsc = ceph_inode_to_client(inode)->mdsc;

  	struct ceph_inode_info *ci = ceph_inode(inode);
  	struct ceph_cap *new_cap = NULL;
  	struct ceph_cap *cap;
  	int mds = session->s_mds;
  	int actual_wanted;
  
  	dout("add_cap %p mds%d cap %llx %s seq %d
  ", inode,
  	     session->s_mds, cap_id, ceph_cap_string(issued), seq);
  
  	/*
  	 * If we are opening the file, include file mode wanted bits
  	 * in wanted.
  	 */
  	if (fmode >= 0)
  		wanted |= ceph_caps_for_mode(fmode);
  
  retry:

  	spin_lock(&ci->i_ceph_lock);

  	cap = __get_cap_for_mds(ci, mds);
  	if (!cap) {
  		if (new_cap) {
  			cap = new_cap;
  			new_cap = NULL;
  		} else {

  			spin_unlock(&ci->i_ceph_lock);

  			new_cap = get_cap(mdsc, caps_reservation);

  			if (new_cap == NULL)
  				return -ENOMEM;
  			goto retry;
  		}
  
  		cap->issued = 0;
  		cap->implemented = 0;
  		cap->mds = mds;
  		cap->mds_wanted = 0;
  
  		cap->ci = ci;
  		__insert_cap_node(ci, cap);
  
  		/* clear out old exporting info?  (i.e. on cap import) */
  		if (ci->i_cap_exporting_mds == mds) {
  			ci->i_cap_exporting_issued = 0;
  			ci->i_cap_exporting_mseq = 0;
  			ci->i_cap_exporting_mds = -1;
  		}
  
  		/* add to session cap list */
  		cap->session = session;
  		spin_lock(&session->s_cap_lock);
  		list_add_tail(&cap->session_caps, &session->s_caps);
  		session->s_nr_caps++;
  		spin_unlock(&session->s_cap_lock);

  	} else if (new_cap)
  		ceph_put_cap(mdsc, new_cap);

  
  	if (!ci->i_snap_realm) {
  		/*
  		 * add this inode to the appropriate snap realm
  		 */
  		struct ceph_snap_realm *realm = ceph_lookup_snap_realm(mdsc,
  							       realmino);
  		if (realm) {
  			ceph_get_snap_realm(mdsc, realm);
  			spin_lock(&realm->inodes_with_caps_lock);
  			ci->i_snap_realm = realm;
  			list_add(&ci->i_snap_realm_item,
  				 &realm->inodes_with_caps);
  			spin_unlock(&realm->inodes_with_caps_lock);
  		} else {
  			pr_err("ceph_add_cap: couldn't find snap realm %llx
  ",
  			       realmino);

  			WARN_ON(!realm);

  		}
  	}
  
  	__check_cap_issue(ci, cap, issued);
  
  	/*
  	 * If we are issued caps we don't want, or the mds' wanted
  	 * value appears to be off, queue a check so we'll release
  	 * later and/or update the mds wanted value.
  	 */
  	actual_wanted = __ceph_caps_wanted(ci);
  	if ((wanted & ~actual_wanted) ||
  	    (issued & ~actual_wanted & CEPH_CAP_ANY_WR)) {
  		dout(" issued %s, mds wanted %s, actual %s, queueing
  ",
  		     ceph_cap_string(issued), ceph_cap_string(wanted),
  		     ceph_cap_string(actual_wanted));
  		__cap_delay_requeue(mdsc, ci);
  	}
  
  	if (flags & CEPH_CAP_FLAG_AUTH)
  		ci->i_auth_cap = cap;
  	else if (ci->i_auth_cap == cap)
  		ci->i_auth_cap = NULL;
  
  	dout("add_cap inode %p (%llx.%llx) cap %p %s now %s seq %d mds%d
  ",
  	     inode, ceph_vinop(inode), cap, ceph_cap_string(issued),
  	     ceph_cap_string(issued|cap->issued), seq, mds);
  	cap->cap_id = cap_id;
  	cap->issued = issued;
  	cap->implemented |= issued;
  	cap->mds_wanted |= wanted;
  	cap->seq = seq;
  	cap->issue_seq = seq;
  	cap->mseq = mseq;

  	cap->cap_gen = session->s_cap_gen;

  
  	if (fmode >= 0)
  		__ceph_get_fmode(ci, fmode);

  	spin_unlock(&ci->i_ceph_lock);

  	wake_up_all(&ci->i_cap_wq);

  	return 0;
  }
  
  /*
   * Return true if cap has not timed out and belongs to the current
   * generation of the MDS session (i.e. has not gone 'stale' due to
   * us losing touch with the mds).
   */
  static int __cap_is_valid(struct ceph_cap *cap)
  {
  	unsigned long ttl;

  	u32 gen;

  
  	spin_lock(&cap->session->s_cap_lock);
  	gen = cap->session->s_cap_gen;
  	ttl = cap->session->s_cap_ttl;
  	spin_unlock(&cap->session->s_cap_lock);

  	if (cap->cap_gen < gen || time_after_eq(jiffies, ttl)) {

  		dout("__cap_is_valid %p cap %p issued %s "
  		     "but STALE (gen %u vs %u)
  ", &cap->ci->vfs_inode,

  		     cap, ceph_cap_string(cap->issued), cap->cap_gen, gen);

  		return 0;
  	}
  
  	return 1;
  }
  
  /*
   * Return set of valid cap bits issued to us.  Note that caps time
   * out, and may be invalidated in bulk if the client session times out
   * and session->s_cap_gen is bumped.
   */
  int __ceph_caps_issued(struct ceph_inode_info *ci, int *implemented)
  {

  	int have = ci->i_snap_caps | ci->i_cap_exporting_issued;

  	struct ceph_cap *cap;
  	struct rb_node *p;
  
  	if (implemented)
  		*implemented = 0;
  	for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
  		cap = rb_entry(p, struct ceph_cap, ci_node);
  		if (!__cap_is_valid(cap))
  			continue;
  		dout("__ceph_caps_issued %p cap %p issued %s
  ",
  		     &ci->vfs_inode, cap, ceph_cap_string(cap->issued));
  		have |= cap->issued;
  		if (implemented)
  			*implemented |= cap->implemented;
  	}
  	return have;
  }
  
  /*
   * Get cap bits issued by caps other than @ocap
   */
  int __ceph_caps_issued_other(struct ceph_inode_info *ci, struct ceph_cap *ocap)
  {
  	int have = ci->i_snap_caps;
  	struct ceph_cap *cap;
  	struct rb_node *p;
  
  	for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
  		cap = rb_entry(p, struct ceph_cap, ci_node);
  		if (cap == ocap)
  			continue;
  		if (!__cap_is_valid(cap))
  			continue;
  		have |= cap->issued;
  	}
  	return have;
  }
  
  /*
   * Move a cap to the end of the LRU (oldest caps at list head, newest
   * at list tail).
   */
  static void __touch_cap(struct ceph_cap *cap)
  {
  	struct ceph_mds_session *s = cap->session;

  	spin_lock(&s->s_cap_lock);

  	if (s->s_cap_iterator == NULL) {

  		dout("__touch_cap %p cap %p mds%d
  ", &cap->ci->vfs_inode, cap,
  		     s->s_mds);
  		list_move_tail(&cap->session_caps, &s->s_caps);
  	} else {
  		dout("__touch_cap %p cap %p mds%d NOP, iterating over caps
  ",
  		     &cap->ci->vfs_inode, cap, s->s_mds);
  	}

  	spin_unlock(&s->s_cap_lock);
  }
  
  /*
   * Check if we hold the given mask.  If so, move the cap(s) to the
   * front of their respective LRUs.  (This is the preferred way for
   * callers to check for caps they want.)
   */
  int __ceph_caps_issued_mask(struct ceph_inode_info *ci, int mask, int touch)
  {
  	struct ceph_cap *cap;
  	struct rb_node *p;
  	int have = ci->i_snap_caps;
  
  	if ((have & mask) == mask) {
  		dout("__ceph_caps_issued_mask %p snap issued %s"
  		     " (mask %s)
  ", &ci->vfs_inode,
  		     ceph_cap_string(have),
  		     ceph_cap_string(mask));
  		return 1;
  	}
  
  	for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
  		cap = rb_entry(p, struct ceph_cap, ci_node);
  		if (!__cap_is_valid(cap))
  			continue;
  		if ((cap->issued & mask) == mask) {
  			dout("__ceph_caps_issued_mask %p cap %p issued %s"
  			     " (mask %s)
  ", &ci->vfs_inode, cap,
  			     ceph_cap_string(cap->issued),
  			     ceph_cap_string(mask));
  			if (touch)
  				__touch_cap(cap);
  			return 1;
  		}
  
  		/* does a combination of caps satisfy mask? */
  		have |= cap->issued;
  		if ((have & mask) == mask) {
  			dout("__ceph_caps_issued_mask %p combo issued %s"
  			     " (mask %s)
  ", &ci->vfs_inode,
  			     ceph_cap_string(cap->issued),
  			     ceph_cap_string(mask));
  			if (touch) {
  				struct rb_node *q;

  				/* touch this + preceding caps */

  				__touch_cap(cap);
  				for (q = rb_first(&ci->i_caps); q != p;
  				     q = rb_next(q)) {
  					cap = rb_entry(q, struct ceph_cap,
  						       ci_node);
  					if (!__cap_is_valid(cap))
  						continue;
  					__touch_cap(cap);
  				}
  			}
  			return 1;
  		}
  	}
  
  	return 0;
  }
  
  /*
   * Return true if mask caps are currently being revoked by an MDS.
   */
  int ceph_caps_revoking(struct ceph_inode_info *ci, int mask)
  {
  	struct inode *inode = &ci->vfs_inode;
  	struct ceph_cap *cap;
  	struct rb_node *p;
  	int ret = 0;

  	spin_lock(&ci->i_ceph_lock);

  	for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
  		cap = rb_entry(p, struct ceph_cap, ci_node);
  		if (__cap_is_valid(cap) &&
  		    (cap->implemented & ~cap->issued & mask)) {
  			ret = 1;
  			break;
  		}
  	}

  	spin_unlock(&ci->i_ceph_lock);

  	dout("ceph_caps_revoking %p %s = %d
  ", inode,
  	     ceph_cap_string(mask), ret);
  	return ret;
  }
  
  int __ceph_caps_used(struct ceph_inode_info *ci)
  {
  	int used = 0;
  	if (ci->i_pin_ref)
  		used |= CEPH_CAP_PIN;
  	if (ci->i_rd_ref)
  		used |= CEPH_CAP_FILE_RD;

  	if (ci->i_rdcache_ref || ci->vfs_inode.i_data.nrpages)

  		used |= CEPH_CAP_FILE_CACHE;
  	if (ci->i_wr_ref)
  		used |= CEPH_CAP_FILE_WR;

  	if (ci->i_wb_ref || ci->i_wrbuffer_ref)

  		used |= CEPH_CAP_FILE_BUFFER;
  	return used;
  }
  
  /*
   * wanted, by virtue of open file modes
   */
  int __ceph_caps_file_wanted(struct ceph_inode_info *ci)
  {
  	int want = 0;
  	int mode;

  	for (mode = 0; mode < CEPH_FILE_MODE_NUM; mode++)

  		if (ci->i_nr_by_mode[mode])
  			want |= ceph_caps_for_mode(mode);
  	return want;
  }
  
  /*
   * Return caps we have registered with the MDS(s) as 'wanted'.
   */
  int __ceph_caps_mds_wanted(struct ceph_inode_info *ci)
  {
  	struct ceph_cap *cap;
  	struct rb_node *p;
  	int mds_wanted = 0;
  
  	for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
  		cap = rb_entry(p, struct ceph_cap, ci_node);
  		if (!__cap_is_valid(cap))
  			continue;
  		mds_wanted |= cap->mds_wanted;
  	}
  	return mds_wanted;
  }
  
  /*

   * called under i_ceph_lock

   */
  static int __ceph_is_any_caps(struct ceph_inode_info *ci)
  {
  	return !RB_EMPTY_ROOT(&ci->i_caps) || ci->i_cap_exporting_mds >= 0;
  }
  
  /*

   * Remove a cap.  Take steps to deal with a racing iterate_session_caps.
   *

   * caller should hold i_ceph_lock.

   * caller will not hold session s_mutex if called from destroy_inode.

   */

  void __ceph_remove_cap(struct ceph_cap *cap)

  {
  	struct ceph_mds_session *session = cap->session;
  	struct ceph_inode_info *ci = cap->ci;

  	struct ceph_mds_client *mdsc =

  		ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc;

  	int removed = 0;

  
  	dout("__ceph_remove_cap %p from %p
  ", cap, &ci->vfs_inode);

  	/* remove from session list */
  	spin_lock(&session->s_cap_lock);
  	if (session->s_cap_iterator == cap) {
  		/* not yet, we are iterating over this very cap */
  		dout("__ceph_remove_cap  delaying %p removal from session %p
  ",
  		     cap, cap->session);
  	} else {
  		list_del_init(&cap->session_caps);
  		session->s_nr_caps--;
  		cap->session = NULL;

  		removed = 1;

  	}

  	/* protect backpointer with s_cap_lock: see iterate_session_caps */
  	cap->ci = NULL;

  	spin_unlock(&session->s_cap_lock);

  	/* remove from inode list */
  	rb_erase(&cap->ci_node, &ci->i_caps);
  	if (ci->i_auth_cap == cap)
  		ci->i_auth_cap = NULL;
  
  	if (removed)

  		ceph_put_cap(mdsc, cap);

  
  	if (!__ceph_is_any_caps(ci) && ci->i_snap_realm) {
  		struct ceph_snap_realm *realm = ci->i_snap_realm;
  		spin_lock(&realm->inodes_with_caps_lock);
  		list_del_init(&ci->i_snap_realm_item);
  		ci->i_snap_realm_counter++;
  		ci->i_snap_realm = NULL;
  		spin_unlock(&realm->inodes_with_caps_lock);
  		ceph_put_snap_realm(mdsc, realm);
  	}
  	if (!__ceph_is_any_real_caps(ci))
  		__cap_delay_cancel(mdsc, ci);
  }
  
  /*
   * Build and send a cap message to the given MDS.
   *
   * Caller should be holding s_mutex.
   */
  static int send_cap_msg(struct ceph_mds_session *session,
  			u64 ino, u64 cid, int op,
  			int caps, int wanted, int dirty,
  			u32 seq, u64 flush_tid, u32 issue_seq, u32 mseq,
  			u64 size, u64 max_size,
  			struct timespec *mtime, struct timespec *atime,
  			u64 time_warp_seq,

  			uid_t uid, gid_t gid, umode_t mode,

  			u64 xattr_version,
  			struct ceph_buffer *xattrs_buf,
  			u64 follows)
  {
  	struct ceph_mds_caps *fc;
  	struct ceph_msg *msg;
  
  	dout("send_cap_msg %s %llx %llx caps %s wanted %s dirty %s"
  	     " seq %u/%u mseq %u follows %lld size %llu/%llu"
  	     " xattr_ver %llu xattr_len %d
  ", ceph_cap_op_name(op),
  	     cid, ino, ceph_cap_string(caps), ceph_cap_string(wanted),
  	     ceph_cap_string(dirty),
  	     seq, issue_seq, mseq, follows, size, max_size,
  	     xattr_version, xattrs_buf ? (int)xattrs_buf->vec.iov_len : 0);

  	msg = ceph_msg_new(CEPH_MSG_CLIENT_CAPS, sizeof(*fc), GFP_NOFS, false);

  	if (!msg)
  		return -ENOMEM;

  	msg->hdr.tid = cpu_to_le64(flush_tid);

  	fc = msg->front.iov_base;

  	memset(fc, 0, sizeof(*fc));
  
  	fc->cap_id = cpu_to_le64(cid);
  	fc->op = cpu_to_le32(op);
  	fc->seq = cpu_to_le32(seq);

  	fc->issue_seq = cpu_to_le32(issue_seq);
  	fc->migrate_seq = cpu_to_le32(mseq);
  	fc->caps = cpu_to_le32(caps);
  	fc->wanted = cpu_to_le32(wanted);
  	fc->dirty = cpu_to_le32(dirty);
  	fc->ino = cpu_to_le64(ino);
  	fc->snap_follows = cpu_to_le64(follows);
  
  	fc->size = cpu_to_le64(size);
  	fc->max_size = cpu_to_le64(max_size);
  	if (mtime)
  		ceph_encode_timespec(&fc->mtime, mtime);
  	if (atime)
  		ceph_encode_timespec(&fc->atime, atime);
  	fc->time_warp_seq = cpu_to_le32(time_warp_seq);
  
  	fc->uid = cpu_to_le32(uid);
  	fc->gid = cpu_to_le32(gid);
  	fc->mode = cpu_to_le32(mode);
  
  	fc->xattr_version = cpu_to_le64(xattr_version);
  	if (xattrs_buf) {
  		msg->middle = ceph_buffer_get(xattrs_buf);
  		fc->xattr_len = cpu_to_le32(xattrs_buf->vec.iov_len);
  		msg->hdr.middle_len = cpu_to_le32(xattrs_buf->vec.iov_len);
  	}
  
  	ceph_con_send(&session->s_con, msg);
  	return 0;
  }

  static void __queue_cap_release(struct ceph_mds_session *session,
  				u64 ino, u64 cap_id, u32 migrate_seq,
  				u32 issue_seq)
  {
  	struct ceph_msg *msg;
  	struct ceph_mds_cap_release *head;
  	struct ceph_mds_cap_item *item;
  
  	spin_lock(&session->s_cap_lock);
  	BUG_ON(!session->s_num_cap_releases);
  	msg = list_first_entry(&session->s_cap_releases,
  			       struct ceph_msg, list_head);
  
  	dout(" adding %llx release to mds%d msg %p (%d left)
  ",
  	     ino, session->s_mds, msg, session->s_num_cap_releases);
  
  	BUG_ON(msg->front.iov_len + sizeof(*item) > PAGE_CACHE_SIZE);
  	head = msg->front.iov_base;
  	head->num = cpu_to_le32(le32_to_cpu(head->num) + 1);
  	item = msg->front.iov_base + msg->front.iov_len;
  	item->ino = cpu_to_le64(ino);
  	item->cap_id = cpu_to_le64(cap_id);
  	item->migrate_seq = cpu_to_le32(migrate_seq);
  	item->seq = cpu_to_le32(issue_seq);
  
  	session->s_num_cap_releases--;
  
  	msg->front.iov_len += sizeof(*item);
  	if (le32_to_cpu(head->num) == CEPH_CAPS_PER_RELEASE) {
  		dout(" release msg %p full
  ", msg);
  		list_move_tail(&msg->list_head, &session->s_cap_releases_done);
  	} else {
  		dout(" release msg %p at %d/%d (%d)
  ", msg,
  		     (int)le32_to_cpu(head->num),
  		     (int)CEPH_CAPS_PER_RELEASE,
  		     (int)msg->front.iov_len);
  	}
  	spin_unlock(&session->s_cap_lock);
  }

  /*

   * Queue cap releases when an inode is dropped from our cache.  Since

   * inode is about to be destroyed, there is no need for i_ceph_lock.

   */
  void ceph_queue_caps_release(struct inode *inode)
  {
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	struct rb_node *p;

  	p = rb_first(&ci->i_caps);
  	while (p) {
  		struct ceph_cap *cap = rb_entry(p, struct ceph_cap, ci_node);
  		struct ceph_mds_session *session = cap->session;

  		__queue_cap_release(session, ceph_ino(inode), cap->cap_id,
  				    cap->mseq, cap->issue_seq);

  		p = rb_next(p);

  		__ceph_remove_cap(cap);

  	}

  }
  
  /*
   * Send a cap msg on the given inode.  Update our caps state, then

   * drop i_ceph_lock and send the message.

   *
   * Make note of max_size reported/requested from mds, revoked caps
   * that have now been implemented.
   *
   * Make half-hearted attempt ot to invalidate page cache if we are
   * dropping RDCACHE.  Note that this will leave behind locked pages
   * that we'll then need to deal with elsewhere.
   *
   * Return non-zero if delayed release, or we experienced an error
   * such that the caller should requeue + retry later.
   *

   * called with i_ceph_lock, then drops it.

   * caller should hold snap_rwsem (read), s_mutex.
   */
  static int __send_cap(struct ceph_mds_client *mdsc, struct ceph_cap *cap,
  		      int op, int used, int want, int retain, int flushing,
  		      unsigned *pflush_tid)

  	__releases(cap->ci->i_ceph_lock)

  {
  	struct ceph_inode_info *ci = cap->ci;
  	struct inode *inode = &ci->vfs_inode;
  	u64 cap_id = cap->cap_id;

  	int held, revoking, dropping, keep;

  	u64 seq, issue_seq, mseq, time_warp_seq, follows;
  	u64 size, max_size;
  	struct timespec mtime, atime;
  	int wake = 0;

  	umode_t mode;

  	uid_t uid;
  	gid_t gid;
  	struct ceph_mds_session *session;
  	u64 xattr_version = 0;

  	struct ceph_buffer *xattr_blob = NULL;

  	int delayed = 0;
  	u64 flush_tid = 0;
  	int i;
  	int ret;

  	held = cap->issued | cap->implemented;
  	revoking = cap->implemented & ~cap->issued;
  	retain &= ~revoking;
  	dropping = cap->issued & ~retain;

  	dout("__send_cap %p cap %p session %p %s -> %s (revoking %s)
  ",
  	     inode, cap, cap->session,
  	     ceph_cap_string(held), ceph_cap_string(held & retain),
  	     ceph_cap_string(revoking));
  	BUG_ON((retain & CEPH_CAP_PIN) == 0);
  
  	session = cap->session;
  
  	/* don't release wanted unless we've waited a bit. */
  	if ((ci->i_ceph_flags & CEPH_I_NODELAY) == 0 &&
  	    time_before(jiffies, ci->i_hold_caps_min)) {
  		dout(" delaying issued %s -> %s, wanted %s -> %s on send
  ",
  		     ceph_cap_string(cap->issued),
  		     ceph_cap_string(cap->issued & retain),
  		     ceph_cap_string(cap->mds_wanted),
  		     ceph_cap_string(want));
  		want |= cap->mds_wanted;
  		retain |= cap->issued;
  		delayed = 1;
  	}
  	ci->i_ceph_flags &= ~(CEPH_I_NODELAY | CEPH_I_FLUSH);
  
  	cap->issued &= retain;  /* drop bits we don't want */
  	if (cap->implemented & ~cap->issued) {
  		/*
  		 * Wake up any waiters on wanted -> needed transition.
  		 * This is due to the weird transition from buffered
  		 * to sync IO... we need to flush dirty pages _before_
  		 * allowing sync writes to avoid reordering.
  		 */
  		wake = 1;
  	}
  	cap->implemented &= cap->issued | used;
  	cap->mds_wanted = want;
  
  	if (flushing) {
  		/*
  		 * assign a tid for flush operations so we can avoid
  		 * flush1 -> dirty1 -> flush2 -> flushack1 -> mark
  		 * clean type races.  track latest tid for every bit
  		 * so we can handle flush AxFw, flush Fw, and have the
  		 * first ack clean Ax.
  		 */
  		flush_tid = ++ci->i_cap_flush_last_tid;
  		if (pflush_tid)
  			*pflush_tid = flush_tid;
  		dout(" cap_flush_tid %d
  ", (int)flush_tid);
  		for (i = 0; i < CEPH_CAP_BITS; i++)
  			if (flushing & (1 << i))
  				ci->i_cap_flush_tid[i] = flush_tid;

  
  		follows = ci->i_head_snapc->seq;
  	} else {
  		follows = 0;

  	}
  
  	keep = cap->implemented;
  	seq = cap->seq;
  	issue_seq = cap->issue_seq;
  	mseq = cap->mseq;
  	size = inode->i_size;
  	ci->i_reported_size = size;
  	max_size = ci->i_wanted_max_size;
  	ci->i_requested_max_size = max_size;
  	mtime = inode->i_mtime;
  	atime = inode->i_atime;
  	time_warp_seq = ci->i_time_warp_seq;

  	uid = inode->i_uid;
  	gid = inode->i_gid;
  	mode = inode->i_mode;

  	if (flushing & CEPH_CAP_XATTR_EXCL) {

  		__ceph_build_xattrs_blob(ci);

  		xattr_blob = ci->i_xattrs.blob;
  		xattr_version = ci->i_xattrs.version;

  	}

  	spin_unlock(&ci->i_ceph_lock);

  	ret = send_cap_msg(session, ceph_vino(inode).ino, cap_id,
  		op, keep, want, flushing, seq, flush_tid, issue_seq, mseq,
  		size, max_size, &mtime, &atime, time_warp_seq,

  		uid, gid, mode, xattr_version, xattr_blob,

  		follows);
  	if (ret < 0) {
  		dout("error sending cap msg, must requeue %p
  ", inode);
  		delayed = 1;
  	}
  
  	if (wake)

  		wake_up_all(&ci->i_cap_wq);

  
  	return delayed;
  }
  
  /*
   * When a snapshot is taken, clients accumulate dirty metadata on
   * inodes with capabilities in ceph_cap_snaps to describe the file
   * state at the time the snapshot was taken.  This must be flushed
   * asynchronously back to the MDS once sync writes complete and dirty
   * data is written out.
   *

   * Unless @again is true, skip cap_snaps that were already sent to
   * the MDS (i.e., during this session).
   *

   * Called under i_ceph_lock.  Takes s_mutex as needed.

   */
  void __ceph_flush_snaps(struct ceph_inode_info *ci,

  			struct ceph_mds_session **psession,
  			int again)

  		__releases(ci->i_ceph_lock)
  		__acquires(ci->i_ceph_lock)

  {
  	struct inode *inode = &ci->vfs_inode;
  	int mds;
  	struct ceph_cap_snap *capsnap;
  	u32 mseq;

  	struct ceph_mds_client *mdsc = ceph_inode_to_client(inode)->mdsc;

  	struct ceph_mds_session *session = NULL; /* if session != NULL, we hold
  						    session->s_mutex */
  	u64 next_follows = 0;  /* keep track of how far we've gotten through the
  			     i_cap_snaps list, and skip these entries next time
  			     around to avoid an infinite loop */
  
  	if (psession)
  		session = *psession;
  
  	dout("__flush_snaps %p
  ", inode);
  retry:
  	list_for_each_entry(capsnap, &ci->i_cap_snaps, ci_item) {
  		/* avoid an infiniute loop after retry */
  		if (capsnap->follows < next_follows)
  			continue;
  		/*
  		 * we need to wait for sync writes to complete and for dirty
  		 * pages to be written out.
  		 */
  		if (capsnap->dirty_pages || capsnap->writing)

  			break;

  		/*
  		 * if cap writeback already occurred, we should have dropped
  		 * the capsnap in ceph_put_wrbuffer_cap_refs.
  		 */
  		BUG_ON(capsnap->dirty == 0);

  		/* pick mds, take s_mutex */

  		if (ci->i_auth_cap == NULL) {
  			dout("no auth cap (migrating?), doing nothing
  ");
  			goto out;
  		}

  
  		/* only flush each capsnap once */
  		if (!again && !list_empty(&capsnap->flushing_item)) {
  			dout("already flushed %p, skipping
  ", capsnap);
  			continue;
  		}

  		mds = ci->i_auth_cap->session->s_mds;
  		mseq = ci->i_auth_cap->mseq;

  		if (session && session->s_mds != mds) {
  			dout("oops, wrong session %p mutex
  ", session);
  			mutex_unlock(&session->s_mutex);
  			ceph_put_mds_session(session);
  			session = NULL;
  		}
  		if (!session) {

  			spin_unlock(&ci->i_ceph_lock);

  			mutex_lock(&mdsc->mutex);
  			session = __ceph_lookup_mds_session(mdsc, mds);
  			mutex_unlock(&mdsc->mutex);
  			if (session) {
  				dout("inverting session/ino locks on %p
  ",
  				     session);
  				mutex_lock(&session->s_mutex);
  			}
  			/*
  			 * if session == NULL, we raced against a cap

  			 * deletion or migration.  retry, and we'll
  			 * get a better @mds value next time.

  			 */

  			spin_lock(&ci->i_ceph_lock);

  			goto retry;
  		}
  
  		capsnap->flush_tid = ++ci->i_cap_flush_last_tid;
  		atomic_inc(&capsnap->nref);
  		if (!list_empty(&capsnap->flushing_item))
  			list_del_init(&capsnap->flushing_item);
  		list_add_tail(&capsnap->flushing_item,
  			      &session->s_cap_snaps_flushing);

  		spin_unlock(&ci->i_ceph_lock);

  		dout("flush_snaps %p cap_snap %p follows %lld tid %llu
  ",
  		     inode, capsnap, capsnap->follows, capsnap->flush_tid);

  		send_cap_msg(session, ceph_vino(inode).ino, 0,
  			     CEPH_CAP_OP_FLUSHSNAP, capsnap->issued, 0,
  			     capsnap->dirty, 0, capsnap->flush_tid, 0, mseq,
  			     capsnap->size, 0,
  			     &capsnap->mtime, &capsnap->atime,
  			     capsnap->time_warp_seq,
  			     capsnap->uid, capsnap->gid, capsnap->mode,

  			     capsnap->xattr_version, capsnap->xattr_blob,

  			     capsnap->follows);
  
  		next_follows = capsnap->follows + 1;
  		ceph_put_cap_snap(capsnap);

  		spin_lock(&ci->i_ceph_lock);

  		goto retry;
  	}
  
  	/* we flushed them all; remove this inode from the queue */
  	spin_lock(&mdsc->snap_flush_lock);
  	list_del_init(&ci->i_snap_flush_item);
  	spin_unlock(&mdsc->snap_flush_lock);

  out:

  	if (psession)
  		*psession = session;
  	else if (session) {
  		mutex_unlock(&session->s_mutex);
  		ceph_put_mds_session(session);
  	}
  }
  
  static void ceph_flush_snaps(struct ceph_inode_info *ci)
  {

  	spin_lock(&ci->i_ceph_lock);

  	__ceph_flush_snaps(ci, NULL, 0);

  	spin_unlock(&ci->i_ceph_lock);

  }
  
  /*

   * Mark caps dirty.  If inode is newly dirty, return the dirty flags.
   * Caller is then responsible for calling __mark_inode_dirty with the
   * returned flags value.

   */

  int __ceph_mark_dirty_caps(struct ceph_inode_info *ci, int mask)

  {

  	struct ceph_mds_client *mdsc =

  		ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc;

  	struct inode *inode = &ci->vfs_inode;
  	int was = ci->i_dirty_caps;
  	int dirty = 0;
  
  	dout("__mark_dirty_caps %p %s dirty %s -> %s
  ", &ci->vfs_inode,
  	     ceph_cap_string(mask), ceph_cap_string(was),
  	     ceph_cap_string(was | mask));
  	ci->i_dirty_caps |= mask;
  	if (was == 0) {

  		if (!ci->i_head_snapc)
  			ci->i_head_snapc = ceph_get_snap_context(
  				ci->i_snap_realm->cached_context);
  		dout(" inode %p now dirty snapc %p
  ", &ci->vfs_inode,
  			ci->i_head_snapc);

  		BUG_ON(!list_empty(&ci->i_dirty_item));
  		spin_lock(&mdsc->cap_dirty_lock);
  		list_add(&ci->i_dirty_item, &mdsc->cap_dirty);
  		spin_unlock(&mdsc->cap_dirty_lock);
  		if (ci->i_flushing_caps == 0) {

  			ihold(inode);

  			dirty |= I_DIRTY_SYNC;
  		}
  	}
  	BUG_ON(list_empty(&ci->i_dirty_item));
  	if (((was | ci->i_flushing_caps) & CEPH_CAP_FILE_BUFFER) &&
  	    (mask & CEPH_CAP_FILE_BUFFER))
  		dirty |= I_DIRTY_DATASYNC;

  	__cap_delay_requeue(mdsc, ci);

  	return dirty;

  }
  
  /*

   * Add dirty inode to the flushing list.  Assigned a seq number so we
   * can wait for caps to flush without starving.

   *

   * Called under i_ceph_lock.

   */

  static int __mark_caps_flushing(struct inode *inode,

  				 struct ceph_mds_session *session)
  {

  	struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;

  	struct ceph_inode_info *ci = ceph_inode(inode);

  	int flushing;

  	BUG_ON(ci->i_dirty_caps == 0);

  	BUG_ON(list_empty(&ci->i_dirty_item));

  
  	flushing = ci->i_dirty_caps;
  	dout("__mark_caps_flushing flushing %s, flushing_caps %s -> %s
  ",
  	     ceph_cap_string(flushing),
  	     ceph_cap_string(ci->i_flushing_caps),
  	     ceph_cap_string(ci->i_flushing_caps | flushing));
  	ci->i_flushing_caps |= flushing;
  	ci->i_dirty_caps = 0;

  	dout(" inode %p now !dirty
  ", inode);

  	spin_lock(&mdsc->cap_dirty_lock);

  	list_del_init(&ci->i_dirty_item);
  
  	ci->i_cap_flush_seq = ++mdsc->cap_flush_seq;

  	if (list_empty(&ci->i_flushing_item)) {
  		list_add_tail(&ci->i_flushing_item, &session->s_cap_flushing);
  		mdsc->num_cap_flushing++;

  		dout(" inode %p now flushing seq %lld
  ", inode,
  		     ci->i_cap_flush_seq);
  	} else {
  		list_move_tail(&ci->i_flushing_item, &session->s_cap_flushing);
  		dout(" inode %p now flushing (more) seq %lld
  ", inode,

  		     ci->i_cap_flush_seq);
  	}
  	spin_unlock(&mdsc->cap_dirty_lock);

  
  	return flushing;

  }
  
  /*

   * try to invalidate mapping pages without blocking.
   */

  static int try_nonblocking_invalidate(struct inode *inode)
  {
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	u32 invalidating_gen = ci->i_rdcache_gen;

  	spin_unlock(&ci->i_ceph_lock);

  	invalidate_mapping_pages(&inode->i_data, 0, -1);

  	spin_lock(&ci->i_ceph_lock);

  	if (inode->i_data.nrpages == 0 &&

  	    invalidating_gen == ci->i_rdcache_gen) {
  		/* success. */
  		dout("try_nonblocking_invalidate %p success
  ", inode);

  		/* save any racing async invalidate some trouble */
  		ci->i_rdcache_revoking = ci->i_rdcache_gen - 1;

  		return 0;
  	}
  	dout("try_nonblocking_invalidate %p failed
  ", inode);
  	return -1;
  }
  
  /*

   * Swiss army knife function to examine currently used and wanted
   * versus held caps.  Release, flush, ack revoked caps to mds as
   * appropriate.
   *
   *  CHECK_CAPS_NODELAY - caller is delayed work and we should not delay
   *    cap release further.
   *  CHECK_CAPS_AUTHONLY - we should only check the auth cap
   *  CHECK_CAPS_FLUSH - we should flush any dirty caps immediately, without
   *    further delay.
   */
  void ceph_check_caps(struct ceph_inode_info *ci, int flags,
  		     struct ceph_mds_session *session)
  {

  	struct ceph_fs_client *fsc = ceph_inode_to_client(&ci->vfs_inode);
  	struct ceph_mds_client *mdsc = fsc->mdsc;

  	struct inode *inode = &ci->vfs_inode;
  	struct ceph_cap *cap;
  	int file_wanted, used;
  	int took_snap_rwsem = 0;             /* true if mdsc->snap_rwsem held */

  	int issued, implemented, want, retain, revoking, flushing = 0;

  	int mds = -1;   /* keep track of how far we've gone through i_caps list
  			   to avoid an infinite loop on retry */
  	struct rb_node *p;
  	int tried_invalidate = 0;
  	int delayed = 0, sent = 0, force_requeue = 0, num;

  	int queue_invalidate = 0;

  	int is_delayed = flags & CHECK_CAPS_NODELAY;
  
  	/* if we are unmounting, flush any unused caps immediately. */
  	if (mdsc->stopping)
  		is_delayed = 1;

  	spin_lock(&ci->i_ceph_lock);

  
  	if (ci->i_ceph_flags & CEPH_I_FLUSH)
  		flags |= CHECK_CAPS_FLUSH;
  
  	/* flush snaps first time around only */
  	if (!list_empty(&ci->i_cap_snaps))

  		__ceph_flush_snaps(ci, &session, 0);

  	goto retry_locked;
  retry:

  	spin_lock(&ci->i_ceph_lock);

  retry_locked:
  	file_wanted = __ceph_caps_file_wanted(ci);
  	used = __ceph_caps_used(ci);
  	want = file_wanted | used;

  	issued = __ceph_caps_issued(ci, &implemented);
  	revoking = implemented & ~issued;

  
  	retain = want | CEPH_CAP_PIN;
  	if (!mdsc->stopping && inode->i_nlink > 0) {
  		if (want) {
  			retain |= CEPH_CAP_ANY;       /* be greedy */
  		} else {
  			retain |= CEPH_CAP_ANY_SHARED;
  			/*
  			 * keep RD only if we didn't have the file open RW,
  			 * because then the mds would revoke it anyway to
  			 * journal max_size=0.
  			 */
  			if (ci->i_max_size == 0)
  				retain |= CEPH_CAP_ANY_RD;
  		}
  	}
  
  	dout("check_caps %p file_want %s used %s dirty %s flushing %s"

  	     " issued %s revoking %s retain %s %s%s%s
  ", inode,

  	     ceph_cap_string(file_wanted),
  	     ceph_cap_string(used), ceph_cap_string(ci->i_dirty_caps),
  	     ceph_cap_string(ci->i_flushing_caps),

  	     ceph_cap_string(issued), ceph_cap_string(revoking),

  	     ceph_cap_string(retain),
  	     (flags & CHECK_CAPS_AUTHONLY) ? " AUTHONLY" : "",
  	     (flags & CHECK_CAPS_NODELAY) ? " NODELAY" : "",
  	     (flags & CHECK_CAPS_FLUSH) ? " FLUSH" : "");
  
  	/*
  	 * If we no longer need to hold onto old our caps, and we may
  	 * have cached pages, but don't want them, then try to invalidate.
  	 * If we fail, it's because pages are locked.... try again later.
  	 */
  	if ((!is_delayed || mdsc->stopping) &&
  	    ci->i_wrbuffer_ref == 0 &&               /* no dirty pages... */

  	    inode->i_data.nrpages &&                 /* have cached pages */

  	    (file_wanted == 0 ||                     /* no open files */

  	     (revoking & (CEPH_CAP_FILE_CACHE|
  			  CEPH_CAP_FILE_LAZYIO))) && /*  or revoking cache */

  	    !tried_invalidate) {

  		dout("check_caps trying to invalidate on %p
  ", inode);

  		if (try_nonblocking_invalidate(inode) < 0) {

  			if (revoking & (CEPH_CAP_FILE_CACHE|
  					CEPH_CAP_FILE_LAZYIO)) {

  				dout("check_caps queuing invalidate
  ");
  				queue_invalidate = 1;
  				ci->i_rdcache_revoking = ci->i_rdcache_gen;
  			} else {
  				dout("check_caps failed to invalidate pages
  ");
  				/* we failed to invalidate pages.  check these
  				   caps again later. */
  				force_requeue = 1;
  				__cap_set_timeouts(mdsc, ci);
  			}

  		}
  		tried_invalidate = 1;
  		goto retry_locked;
  	}
  
  	num = 0;
  	for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
  		cap = rb_entry(p, struct ceph_cap, ci_node);
  		num++;
  
  		/* avoid looping forever */
  		if (mds >= cap->mds ||
  		    ((flags & CHECK_CAPS_AUTHONLY) && cap != ci->i_auth_cap))
  			continue;
  
  		/* NOTE: no side-effects allowed, until we take s_mutex */
  
  		revoking = cap->implemented & ~cap->issued;

  		dout(" mds%d cap %p issued %s implemented %s revoking %s
  ",
  		     cap->mds, cap, ceph_cap_string(cap->issued),
  		     ceph_cap_string(cap->implemented),
  		     ceph_cap_string(revoking));

  
  		if (cap == ci->i_auth_cap &&
  		    (cap->issued & CEPH_CAP_FILE_WR)) {
  			/* request larger max_size from MDS? */
  			if (ci->i_wanted_max_size > ci->i_max_size &&
  			    ci->i_wanted_max_size > ci->i_requested_max_size) {
  				dout("requesting new max_size
  ");
  				goto ack;
  			}
  
  			/* approaching file_max? */
  			if ((inode->i_size << 1) >= ci->i_max_size &&
  			    (ci->i_reported_size << 1) < ci->i_max_size) {
  				dout("i_size approaching max_size
  ");
  				goto ack;
  			}
  		}
  		/* flush anything dirty? */
  		if (cap == ci->i_auth_cap && (flags & CHECK_CAPS_FLUSH) &&
  		    ci->i_dirty_caps) {
  			dout("flushing dirty caps
  ");
  			goto ack;
  		}
  
  		/* completed revocation? going down and there are no caps? */
  		if (revoking && (revoking & used) == 0) {
  			dout("completed revocation of %s
  ",
  			     ceph_cap_string(cap->implemented & ~cap->issued));
  			goto ack;
  		}
  
  		/* want more caps from mds? */
  		if (want & ~(cap->mds_wanted | cap->issued))
  			goto ack;
  
  		/* things we might delay */
  		if ((cap->issued & ~retain) == 0 &&
  		    cap->mds_wanted == want)
  			continue;     /* nope, all good */
  
  		if (is_delayed)
  			goto ack;
  
  		/* delay? */
  		if ((ci->i_ceph_flags & CEPH_I_NODELAY) == 0 &&
  		    time_before(jiffies, ci->i_hold_caps_max)) {
  			dout(" delaying issued %s -> %s, wanted %s -> %s
  ",
  			     ceph_cap_string(cap->issued),
  			     ceph_cap_string(cap->issued & retain),
  			     ceph_cap_string(cap->mds_wanted),
  			     ceph_cap_string(want));
  			delayed++;
  			continue;
  		}
  
  ack:

  		if (ci->i_ceph_flags & CEPH_I_NOFLUSH) {
  			dout(" skipping %p I_NOFLUSH set
  ", inode);
  			continue;
  		}

  		if (session && session != cap->session) {
  			dout("oops, wrong session %p mutex
  ", session);
  			mutex_unlock(&session->s_mutex);
  			session = NULL;
  		}
  		if (!session) {
  			session = cap->session;
  			if (mutex_trylock(&session->s_mutex) == 0) {
  				dout("inverting session/ino locks on %p
  ",
  				     session);

  				spin_unlock(&ci->i_ceph_lock);

  				if (took_snap_rwsem) {
  					up_read(&mdsc->snap_rwsem);
  					took_snap_rwsem = 0;
  				}
  				mutex_lock(&session->s_mutex);
  				goto retry;
  			}
  		}
  		/* take snap_rwsem after session mutex */
  		if (!took_snap_rwsem) {
  			if (down_read_trylock(&mdsc->snap_rwsem) == 0) {
  				dout("inverting snap/in locks on %p
  ",
  				     inode);

  				spin_unlock(&ci->i_ceph_lock);

  				down_read(&mdsc->snap_rwsem);
  				took_snap_rwsem = 1;
  				goto retry;
  			}
  			took_snap_rwsem = 1;
  		}

  		if (cap == ci->i_auth_cap && ci->i_dirty_caps)
  			flushing = __mark_caps_flushing(inode, session);

  		else
  			flushing = 0;

  
  		mds = cap->mds;  /* remember mds, so we don't repeat */
  		sent++;

  		/* __send_cap drops i_ceph_lock */

  		delayed += __send_cap(mdsc, cap, CEPH_CAP_OP_UPDATE, used, want,
  				      retain, flushing, NULL);

  		goto retry; /* retake i_ceph_lock and restart our cap scan. */

  	}
  
  	/*
  	 * Reschedule delayed caps release if we delayed anything,
  	 * otherwise cancel.
  	 */
  	if (delayed && is_delayed)
  		force_requeue = 1;   /* __send_cap delayed release; requeue */
  	if (!delayed && !is_delayed)
  		__cap_delay_cancel(mdsc, ci);
  	else if (!is_delayed || force_requeue)
  		__cap_delay_requeue(mdsc, ci);

  	spin_unlock(&ci->i_ceph_lock);

  	if (queue_invalidate)

  		ceph_queue_invalidate(inode);

  	if (session)

  		mutex_unlock(&session->s_mutex);
  	if (took_snap_rwsem)
  		up_read(&mdsc->snap_rwsem);
  }
  
  /*

   * Try to flush dirty caps back to the auth mds.
   */
  static int try_flush_caps(struct inode *inode, struct ceph_mds_session *session,
  			  unsigned *flush_tid)
  {

  	struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;

  	struct ceph_inode_info *ci = ceph_inode(inode);
  	int unlock_session = session ? 0 : 1;
  	int flushing = 0;
  
  retry:

  	spin_lock(&ci->i_ceph_lock);

  	if (ci->i_ceph_flags & CEPH_I_NOFLUSH) {
  		dout("try_flush_caps skipping %p I_NOFLUSH set
  ", inode);
  		goto out;
  	}

  	if (ci->i_dirty_caps && ci->i_auth_cap) {
  		struct ceph_cap *cap = ci->i_auth_cap;
  		int used = __ceph_caps_used(ci);
  		int want = __ceph_caps_wanted(ci);
  		int delayed;
  
  		if (!session) {

  			spin_unlock(&ci->i_ceph_lock);

  			session = cap->session;
  			mutex_lock(&session->s_mutex);
  			goto retry;
  		}
  		BUG_ON(session != cap->session);
  		if (cap->session->s_state < CEPH_MDS_SESSION_OPEN)
  			goto out;

  		flushing = __mark_caps_flushing(inode, session);

  		/* __send_cap drops i_ceph_lock */

  		delayed = __send_cap(mdsc, cap, CEPH_CAP_OP_FLUSH, used, want,
  				     cap->issued | cap->implemented, flushing,
  				     flush_tid);
  		if (!delayed)
  			goto out_unlocked;

  		spin_lock(&ci->i_ceph_lock);

  		__cap_delay_requeue(mdsc, ci);
  	}
  out:

  	spin_unlock(&ci->i_ceph_lock);

  out_unlocked:
  	if (session && unlock_session)
  		mutex_unlock(&session->s_mutex);
  	return flushing;
  }
  
  /*
   * Return true if we've flushed caps through the given flush_tid.
   */
  static int caps_are_flushed(struct inode *inode, unsigned tid)
  {
  	struct ceph_inode_info *ci = ceph_inode(inode);

  	int i, ret = 1;

  	spin_lock(&ci->i_ceph_lock);

  	for (i = 0; i < CEPH_CAP_BITS; i++)
  		if ((ci->i_flushing_caps & (1 << i)) &&
  		    ci->i_cap_flush_tid[i] <= tid) {
  			/* still flushing this bit */
  			ret = 0;
  			break;
  		}

  	spin_unlock(&ci->i_ceph_lock);

  	return ret;
  }
  
  /*
   * Wait on any unsafe replies for the given inode.  First wait on the
   * newest request, and make that the upper bound.  Then, if there are
   * more requests, keep waiting on the oldest as long as it is still older
   * than the original request.
   */
  static void sync_write_wait(struct inode *inode)
  {
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	struct list_head *head = &ci->i_unsafe_writes;
  	struct ceph_osd_request *req;
  	u64 last_tid;
  
  	spin_lock(&ci->i_unsafe_lock);
  	if (list_empty(head))
  		goto out;
  
  	/* set upper bound as _last_ entry in chain */
  	req = list_entry(head->prev, struct ceph_osd_request,
  			 r_unsafe_item);
  	last_tid = req->r_tid;
  
  	do {
  		ceph_osdc_get_request(req);
  		spin_unlock(&ci->i_unsafe_lock);
  		dout("sync_write_wait on tid %llu (until %llu)
  ",
  		     req->r_tid, last_tid);
  		wait_for_completion(&req->r_safe_completion);
  		spin_lock(&ci->i_unsafe_lock);
  		ceph_osdc_put_request(req);
  
  		/*
  		 * from here on look at first entry in chain, since we
  		 * only want to wait for anything older than last_tid
  		 */
  		if (list_empty(head))
  			break;
  		req = list_entry(head->next, struct ceph_osd_request,
  				 r_unsafe_item);
  	} while (req->r_tid < last_tid);
  out:
  	spin_unlock(&ci->i_unsafe_lock);
  }

  int ceph_fsync(struct file *file, loff_t start, loff_t end, int datasync)

  {

  	struct inode *inode = file->f_mapping->host;

  	struct ceph_inode_info *ci = ceph_inode(inode);
  	unsigned flush_tid;
  	int ret;
  	int dirty;
  
  	dout("fsync %p%s
  ", inode, datasync ? " datasync" : "");
  	sync_write_wait(inode);

  	ret = filemap_write_and_wait_range(inode->i_mapping, start, end);

  	if (ret < 0)
  		return ret;

  	mutex_lock(&inode->i_mutex);

  
  	dirty = try_flush_caps(inode, NULL, &flush_tid);
  	dout("fsync dirty caps are %s
  ", ceph_cap_string(dirty));
  
  	/*
  	 * only wait on non-file metadata writeback (the mds
  	 * can recover size and mtime, so we don't need to
  	 * wait for that)
  	 */
  	if (!datasync && (dirty & ~CEPH_CAP_ANY_FILE_WR)) {
  		dout("fsync waiting for flush_tid %u
  ", flush_tid);
  		ret = wait_event_interruptible(ci->i_cap_wq,
  				       caps_are_flushed(inode, flush_tid));
  	}
  
  	dout("fsync %p%s done
  ", inode, datasync ? " datasync" : "");

  	mutex_unlock(&inode->i_mutex);

  	return ret;
  }
  
  /*
   * Flush any dirty caps back to the mds.  If we aren't asked to wait,
   * queue inode for flush but don't do so immediately, because we can
   * get by with fewer MDS messages if we wait for data writeback to
   * complete first.
   */

  int ceph_write_inode(struct inode *inode, struct writeback_control *wbc)

  {
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	unsigned flush_tid;
  	int err = 0;
  	int dirty;

  	int wait = wbc->sync_mode == WB_SYNC_ALL;

  
  	dout("write_inode %p wait=%d
  ", inode, wait);
  	if (wait) {
  		dirty = try_flush_caps(inode, NULL, &flush_tid);
  		if (dirty)
  			err = wait_event_interruptible(ci->i_cap_wq,
  				       caps_are_flushed(inode, flush_tid));
  	} else {

  		struct ceph_mds_client *mdsc =

  			ceph_sb_to_client(inode->i_sb)->mdsc;

  		spin_lock(&ci->i_ceph_lock);

  		if (__ceph_caps_dirty(ci))
  			__cap_delay_requeue_front(mdsc, ci);

  		spin_unlock(&ci->i_ceph_lock);

  	}
  	return err;
  }
  
  /*
   * After a recovering MDS goes active, we need to resend any caps
   * we were flushing.
   *
   * Caller holds session->s_mutex.
   */
  static void kick_flushing_capsnaps(struct ceph_mds_client *mdsc,
  				   struct ceph_mds_session *session)
  {
  	struct ceph_cap_snap *capsnap;
  
  	dout("kick_flushing_capsnaps mds%d
  ", session->s_mds);
  	list_for_each_entry(capsnap, &session->s_cap_snaps_flushing,
  			    flushing_item) {
  		struct ceph_inode_info *ci = capsnap->ci;
  		struct inode *inode = &ci->vfs_inode;
  		struct ceph_cap *cap;

  		spin_lock(&ci->i_ceph_lock);

  		cap = ci->i_auth_cap;
  		if (cap && cap->session == session) {
  			dout("kick_flushing_caps %p cap %p capsnap %p
  ", inode,
  			     cap, capsnap);

  			__ceph_flush_snaps(ci, &session, 1);

  		} else {
  			pr_err("%p auth cap %p not mds%d ???
  ", inode,
  			       cap, session->s_mds);

  		}

  		spin_unlock(&ci->i_ceph_lock);

  	}
  }
  
  void ceph_kick_flushing_caps(struct ceph_mds_client *mdsc,
  			     struct ceph_mds_session *session)
  {
  	struct ceph_inode_info *ci;
  
  	kick_flushing_capsnaps(mdsc, session);
  
  	dout("kick_flushing_caps mds%d
  ", session->s_mds);
  	list_for_each_entry(ci, &session->s_cap_flushing, i_flushing_item) {
  		struct inode *inode = &ci->vfs_inode;
  		struct ceph_cap *cap;
  		int delayed = 0;

  		spin_lock(&ci->i_ceph_lock);

  		cap = ci->i_auth_cap;
  		if (cap && cap->session == session) {
  			dout("kick_flushing_caps %p cap %p %s
  ", inode,
  			     cap, ceph_cap_string(ci->i_flushing_caps));
  			delayed = __send_cap(mdsc, cap, CEPH_CAP_OP_FLUSH,
  					     __ceph_caps_used(ci),
  					     __ceph_caps_wanted(ci),
  					     cap->issued | cap->implemented,
  					     ci->i_flushing_caps, NULL);
  			if (delayed) {

  				spin_lock(&ci->i_ceph_lock);

  				__cap_delay_requeue(mdsc, ci);

  				spin_unlock(&ci->i_ceph_lock);

  			}
  		} else {
  			pr_err("%p auth cap %p not mds%d ???
  ", inode,
  			       cap, session->s_mds);

  			spin_unlock(&ci->i_ceph_lock);

  		}
  	}
  }

  static void kick_flushing_inode_caps(struct ceph_mds_client *mdsc,
  				     struct ceph_mds_session *session,
  				     struct inode *inode)
  {
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	struct ceph_cap *cap;
  	int delayed = 0;

  	spin_lock(&ci->i_ceph_lock);

  	cap = ci->i_auth_cap;
  	dout("kick_flushing_inode_caps %p flushing %s flush_seq %lld
  ", inode,
  	     ceph_cap_string(ci->i_flushing_caps), ci->i_cap_flush_seq);
  	__ceph_flush_snaps(ci, &session, 1);
  	if (ci->i_flushing_caps) {
  		delayed = __send_cap(mdsc, cap, CEPH_CAP_OP_FLUSH,
  				     __ceph_caps_used(ci),
  				     __ceph_caps_wanted(ci),
  				     cap->issued | cap->implemented,
  				     ci->i_flushing_caps, NULL);
  		if (delayed) {

  			spin_lock(&ci->i_ceph_lock);

  			__cap_delay_requeue(mdsc, ci);

  			spin_unlock(&ci->i_ceph_lock);

  		}
  	} else {

  		spin_unlock(&ci->i_ceph_lock);

  	}
  }

  
  /*
   * Take references to capabilities we hold, so that we don't release
   * them to the MDS prematurely.
   *

   * Protected by i_ceph_lock.

   */
  static void __take_cap_refs(struct ceph_inode_info *ci, int got)
  {
  	if (got & CEPH_CAP_PIN)
  		ci->i_pin_ref++;
  	if (got & CEPH_CAP_FILE_RD)
  		ci->i_rd_ref++;
  	if (got & CEPH_CAP_FILE_CACHE)
  		ci->i_rdcache_ref++;
  	if (got & CEPH_CAP_FILE_WR)
  		ci->i_wr_ref++;
  	if (got & CEPH_CAP_FILE_BUFFER) {

  		if (ci->i_wb_ref == 0)

  			ihold(&ci->vfs_inode);

  		ci->i_wb_ref++;
  		dout("__take_cap_refs %p wb %d -> %d (?)
  ",
  		     &ci->vfs_inode, ci->i_wb_ref-1, ci->i_wb_ref);

  	}
  }
  
  /*
   * Try to grab cap references.  Specify those refs we @want, and the
   * minimal set we @need.  Also include the larger offset we are writing
   * to (when applicable), and check against max_size here as well.
   * Note that caller is responsible for ensuring max_size increases are
   * requested from the MDS.
   */
  static int try_get_cap_refs(struct ceph_inode_info *ci, int need, int want,
  			    int *got, loff_t endoff, int *check_max, int *err)
  {
  	struct inode *inode = &ci->vfs_inode;
  	int ret = 0;
  	int have, implemented;

  	int file_wanted;

  
  	dout("get_cap_refs %p need %s want %s
  ", inode,
  	     ceph_cap_string(need), ceph_cap_string(want));

  	spin_lock(&ci->i_ceph_lock);

  	/* make sure file is actually open */
  	file_wanted = __ceph_caps_file_wanted(ci);
  	if ((file_wanted & need) == 0) {
  		dout("try_get_cap_refs need %s file_wanted %s, EBADF
  ",
  		     ceph_cap_string(need), ceph_cap_string(file_wanted));

  		*err = -EBADF;
  		ret = 1;
  		goto out;
  	}
  
  	if (need & CEPH_CAP_FILE_WR) {
  		if (endoff >= 0 && endoff > (loff_t)ci->i_max_size) {
  			dout("get_cap_refs %p endoff %llu > maxsize %llu
  ",
  			     inode, endoff, ci->i_max_size);
  			if (endoff > ci->i_wanted_max_size) {
  				*check_max = 1;
  				ret = 1;
  			}
  			goto out;
  		}
  		/*
  		 * If a sync write is in progress, we must wait, so that we
  		 * can get a final snapshot value for size+mtime.
  		 */
  		if (__ceph_have_pending_cap_snap(ci)) {
  			dout("get_cap_refs %p cap_snap_pending
  ", inode);
  			goto out;
  		}
  	}
  	have = __ceph_caps_issued(ci, &implemented);
  
  	/*
  	 * disallow writes while a truncate is pending
  	 */
  	if (ci->i_truncate_pending)
  		have &= ~CEPH_CAP_FILE_WR;
  
  	if ((have & need) == need) {
  		/*
  		 * Look at (implemented & ~have & not) so that we keep waiting
  		 * on transition from wanted -> needed caps.  This is needed
  		 * for WRBUFFER|WR -> WR to avoid a new WR sync write from
  		 * going before a prior buffered writeback happens.
  		 */
  		int not = want & ~(have & need);
  		int revoking = implemented & ~have;
  		dout("get_cap_refs %p have %s but not %s (revoking %s)
  ",
  		     inode, ceph_cap_string(have), ceph_cap_string(not),
  		     ceph_cap_string(revoking));
  		if ((revoking & not) == 0) {
  			*got = need | (have & want);
  			__take_cap_refs(ci, *got);
  			ret = 1;
  		}
  	} else {
  		dout("get_cap_refs %p have %s needed %s
  ", inode,
  		     ceph_cap_string(have), ceph_cap_string(need));
  	}
  out:

  	spin_unlock(&ci->i_ceph_lock);

  	dout("get_cap_refs %p ret %d got %s
  ", inode,
  	     ret, ceph_cap_string(*got));
  	return ret;
  }
  
  /*
   * Check the offset we are writing up to against our current
   * max_size.  If necessary, tell the MDS we want to write to
   * a larger offset.
   */
  static void check_max_size(struct inode *inode, loff_t endoff)
  {
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	int check = 0;
  
  	/* do we need to explicitly request a larger max_size? */

  	spin_lock(&ci->i_ceph_lock);

  	if ((endoff >= ci->i_max_size ||
  	     endoff > (inode->i_size << 1)) &&
  	    endoff > ci->i_wanted_max_size) {
  		dout("write %p at large endoff %llu, req max_size
  ",
  		     inode, endoff);
  		ci->i_wanted_max_size = endoff;
  		check = 1;
  	}

  	spin_unlock(&ci->i_ceph_lock);

  	if (check)
  		ceph_check_caps(ci, CHECK_CAPS_AUTHONLY, NULL);
  }
  
  /*
   * Wait for caps, and take cap references.  If we can't get a WR cap
   * due to a small max_size, make sure we check_max_size (and possibly
   * ask the mds) so we don't get hung up indefinitely.
   */
  int ceph_get_caps(struct ceph_inode_info *ci, int need, int want, int *got,
  		  loff_t endoff)
  {
  	int check_max, ret, err;
  
  retry:
  	if (endoff > 0)
  		check_max_size(&ci->vfs_inode, endoff);
  	check_max = 0;
  	err = 0;
  	ret = wait_event_interruptible(ci->i_cap_wq,
  				       try_get_cap_refs(ci, need, want,
  							got, endoff,
  							&check_max, &err));
  	if (err)
  		ret = err;
  	if (check_max)
  		goto retry;
  	return ret;
  }
  
  /*
   * Take cap refs.  Caller must already know we hold at least one ref
   * on the caps in question or we don't know this is safe.
   */
  void ceph_get_cap_refs(struct ceph_inode_info *ci, int caps)
  {

  	spin_lock(&ci->i_ceph_lock);

  	__take_cap_refs(ci, caps);

  	spin_unlock(&ci->i_ceph_lock);

  }
  
  /*
   * Release cap refs.
   *
   * If we released the last ref on any given cap, call ceph_check_caps
   * to release (or schedule a release).
   *
   * If we are releasing a WR cap (from a sync write), finalize any affected
   * cap_snap, and wake up any waiters.
   */
  void ceph_put_cap_refs(struct ceph_inode_info *ci, int had)
  {
  	struct inode *inode = &ci->vfs_inode;
  	int last = 0, put = 0, flushsnaps = 0, wake = 0;
  	struct ceph_cap_snap *capsnap;

  	spin_lock(&ci->i_ceph_lock);

  	if (had & CEPH_CAP_PIN)
  		--ci->i_pin_ref;
  	if (had & CEPH_CAP_FILE_RD)
  		if (--ci->i_rd_ref == 0)
  			last++;
  	if (had & CEPH_CAP_FILE_CACHE)
  		if (--ci->i_rdcache_ref == 0)
  			last++;
  	if (had & CEPH_CAP_FILE_BUFFER) {

  		if (--ci->i_wb_ref == 0) {

  			last++;
  			put++;
  		}

  		dout("put_cap_refs %p wb %d -> %d (?)
  ",
  		     inode, ci->i_wb_ref+1, ci->i_wb_ref);

  	}
  	if (had & CEPH_CAP_FILE_WR)
  		if (--ci->i_wr_ref == 0) {
  			last++;
  			if (!list_empty(&ci->i_cap_snaps)) {
  				capsnap = list_first_entry(&ci->i_cap_snaps,
  						     struct ceph_cap_snap,
  						     ci_item);
  				if (capsnap->writing) {
  					capsnap->writing = 0;
  					flushsnaps =
  						__ceph_finish_cap_snap(ci,
  								       capsnap);
  					wake = 1;
  				}
  			}
  		}

  	spin_unlock(&ci->i_ceph_lock);

  	dout("put_cap_refs %p had %s%s%s
  ", inode, ceph_cap_string(had),
  	     last ? " last" : "", put ? " put" : "");

  
  	if (last && !flushsnaps)
  		ceph_check_caps(ci, 0, NULL);
  	else if (flushsnaps)
  		ceph_flush_snaps(ci);
  	if (wake)

  		wake_up_all(&ci->i_cap_wq);

  	if (put)
  		iput(inode);
  }
  
  /*
   * Release @nr WRBUFFER refs on dirty pages for the given @snapc snap
   * context.  Adjust per-snap dirty page accounting as appropriate.
   * Once all dirty data for a cap_snap is flushed, flush snapped file
   * metadata back to the MDS.  If we dropped the last ref, call
   * ceph_check_caps.
   */
  void ceph_put_wrbuffer_cap_refs(struct ceph_inode_info *ci, int nr,
  				struct ceph_snap_context *snapc)
  {
  	struct inode *inode = &ci->vfs_inode;
  	int last = 0;

  	int complete_capsnap = 0;
  	int drop_capsnap = 0;

  	int found = 0;
  	struct ceph_cap_snap *capsnap = NULL;

  	spin_lock(&ci->i_ceph_lock);

  	ci->i_wrbuffer_ref -= nr;
  	last = !ci->i_wrbuffer_ref;
  
  	if (ci->i_head_snapc == snapc) {
  		ci->i_wrbuffer_ref_head -= nr;

  		if (ci->i_wrbuffer_ref_head == 0 &&
  		    ci->i_dirty_caps == 0 && ci->i_flushing_caps == 0) {
  			BUG_ON(!ci->i_head_snapc);

  			ceph_put_snap_context(ci->i_head_snapc);
  			ci->i_head_snapc = NULL;
  		}
  		dout("put_wrbuffer_cap_refs on %p head %d/%d -> %d/%d %s
  ",
  		     inode,
  		     ci->i_wrbuffer_ref+nr, ci->i_wrbuffer_ref_head+nr,
  		     ci->i_wrbuffer_ref, ci->i_wrbuffer_ref_head,
  		     last ? " LAST" : "");
  	} else {
  		list_for_each_entry(capsnap, &ci->i_cap_snaps, ci_item) {
  			if (capsnap->context == snapc) {
  				found = 1;

  				break;
  			}
  		}
  		BUG_ON(!found);

  		capsnap->dirty_pages -= nr;
  		if (capsnap->dirty_pages == 0) {
  			complete_capsnap = 1;
  			if (capsnap->dirty == 0)
  				/* cap writeback completed before we created
  				 * the cap_snap; no FLUSHSNAP is needed */
  				drop_capsnap = 1;
  		}

  		dout("put_wrbuffer_cap_refs on %p cap_snap %p "

  		     " snap %lld %d/%d -> %d/%d %s%s%s
  ",

  		     inode, capsnap, capsnap->context->seq,
  		     ci->i_wrbuffer_ref+nr, capsnap->dirty_pages + nr,
  		     ci->i_wrbuffer_ref, capsnap->dirty_pages,
  		     last ? " (wrbuffer last)" : "",

  		     complete_capsnap ? " (complete capsnap)" : "",
  		     drop_capsnap ? " (drop capsnap)" : "");
  		if (drop_capsnap) {
  			ceph_put_snap_context(capsnap->context);
  			list_del(&capsnap->ci_item);
  			list_del(&capsnap->flushing_item);
  			ceph_put_cap_snap(capsnap);
  		}

  	}

  	spin_unlock(&ci->i_ceph_lock);

  
  	if (last) {
  		ceph_check_caps(ci, CHECK_CAPS_AUTHONLY, NULL);
  		iput(inode);

  	} else if (complete_capsnap) {

  		ceph_flush_snaps(ci);

  		wake_up_all(&ci->i_cap_wq);

  	}

  	if (drop_capsnap)
  		iput(inode);

  }
  
  /*
   * Handle a cap GRANT message from the MDS.  (Note that a GRANT may
   * actually be a revocation if it specifies a smaller cap set.)
   *

   * caller holds s_mutex and i_ceph_lock, we drop both.

   *

   * return value:
   *  0 - ok
   *  1 - check_caps on auth cap only (writeback)
   *  2 - check_caps (ack revoke)
   */

  static void handle_cap_grant(struct inode *inode, struct ceph_mds_caps *grant,
  			     struct ceph_mds_session *session,
  			     struct ceph_cap *cap,
  			     struct ceph_buffer *xattr_buf)

  		__releases(ci->i_ceph_lock)

  {
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	int mds = session->s_mds;

  	int seq = le32_to_cpu(grant->seq);

  	int newcaps = le32_to_cpu(grant->caps);
  	int issued, implemented, used, wanted, dirty;
  	u64 size = le64_to_cpu(grant->size);
  	u64 max_size = le64_to_cpu(grant->max_size);
  	struct timespec mtime, atime, ctime;

  	int check_caps = 0;

  	int wake = 0;
  	int writeback = 0;
  	int revoked_rdcache = 0;

  	int queue_invalidate = 0;

  	dout("handle_cap_grant inode %p cap %p mds%d seq %d %s
  ",
  	     inode, cap, mds, seq, ceph_cap_string(newcaps));

  	dout(" size %llu max_size %llu, i_size %llu
  ", size, max_size,
  		inode->i_size);
  
  	/*
  	 * If CACHE is being revoked, and we have no dirty buffers,
  	 * try to invalidate (once).  (If there are dirty buffers, we
  	 * will invalidate _after_ writeback.)
  	 */

  	if (((cap->issued & ~newcaps) & CEPH_CAP_FILE_CACHE) &&
  	    (newcaps & CEPH_CAP_FILE_LAZYIO) == 0 &&

  	    !ci->i_wrbuffer_ref) {

  		if (try_nonblocking_invalidate(inode) == 0) {
  			revoked_rdcache = 1;
  		} else {

  			/* there were locked pages.. invalidate later
  			   in a separate thread. */
  			if (ci->i_rdcache_revoking != ci->i_rdcache_gen) {

  				queue_invalidate = 1;

  				ci->i_rdcache_revoking = ci->i_rdcache_gen;
  			}

  		}

  	}
  
  	/* side effects now are allowed */
  
  	issued = __ceph_caps_issued(ci, &implemented);
  	issued |= implemented | __ceph_caps_dirty(ci);

  	cap->cap_gen = session->s_cap_gen;

  
  	__check_cap_issue(ci, cap, newcaps);
  
  	if ((issued & CEPH_CAP_AUTH_EXCL) == 0) {
  		inode->i_mode = le32_to_cpu(grant->mode);
  		inode->i_uid = le32_to_cpu(grant->uid);
  		inode->i_gid = le32_to_cpu(grant->gid);
  		dout("%p mode 0%o uid.gid %d.%d
  ", inode, inode->i_mode,
  		     inode->i_uid, inode->i_gid);
  	}
  
  	if ((issued & CEPH_CAP_LINK_EXCL) == 0)

  		set_nlink(inode, le32_to_cpu(grant->nlink));

  
  	if ((issued & CEPH_CAP_XATTR_EXCL) == 0 && grant->xattr_len) {
  		int len = le32_to_cpu(grant->xattr_len);
  		u64 version = le64_to_cpu(grant->xattr_version);
  
  		if (version > ci->i_xattrs.version) {
  			dout(" got new xattrs v%llu on %p len %d
  ",
  			     version, inode, len);
  			if (ci->i_xattrs.blob)
  				ceph_buffer_put(ci->i_xattrs.blob);
  			ci->i_xattrs.blob = ceph_buffer_get(xattr_buf);
  			ci->i_xattrs.version = version;
  		}
  	}
  
  	/* size/ctime/mtime/atime? */
  	ceph_fill_file_size(inode, issued,
  			    le32_to_cpu(grant->truncate_seq),
  			    le64_to_cpu(grant->truncate_size), size);
  	ceph_decode_timespec(&mtime, &grant->mtime);
  	ceph_decode_timespec(&atime, &grant->atime);
  	ceph_decode_timespec(&ctime, &grant->ctime);
  	ceph_fill_file_time(inode, issued,
  			    le32_to_cpu(grant->time_warp_seq), &ctime, &mtime,
  			    &atime);
  
  	/* max size increase? */
  	if (max_size != ci->i_max_size) {
  		dout("max_size %lld -> %llu
  ", ci->i_max_size, max_size);
  		ci->i_max_size = max_size;
  		if (max_size >= ci->i_wanted_max_size) {
  			ci->i_wanted_max_size = 0;  /* reset */
  			ci->i_requested_max_size = 0;
  		}
  		wake = 1;
  	}
  
  	/* check cap bits */
  	wanted = __ceph_caps_wanted(ci);
  	used = __ceph_caps_used(ci);
  	dirty = __ceph_caps_dirty(ci);
  	dout(" my wanted = %s, used = %s, dirty %s
  ",
  	     ceph_cap_string(wanted),
  	     ceph_cap_string(used),
  	     ceph_cap_string(dirty));
  	if (wanted != le32_to_cpu(grant->wanted)) {
  		dout("mds wanted %s -> %s
  ",
  		     ceph_cap_string(le32_to_cpu(grant->wanted)),
  		     ceph_cap_string(wanted));
  		grant->wanted = cpu_to_le32(wanted);
  	}
  
  	cap->seq = seq;
  
  	/* file layout may have changed */
  	ci->i_layout = grant->layout;
  
  	/* revocation, grant, or no-op? */
  	if (cap->issued & ~newcaps) {

  		int revoking = cap->issued & ~newcaps;
  
  		dout("revocation: %s -> %s (revoking %s)
  ",
  		     ceph_cap_string(cap->issued),
  		     ceph_cap_string(newcaps),
  		     ceph_cap_string(revoking));

  		if (revoking & used & CEPH_CAP_FILE_BUFFER)

  			writeback = 1;  /* initiate writeback; will delay ack */
  		else if (revoking == CEPH_CAP_FILE_CACHE &&
  			 (newcaps & CEPH_CAP_FILE_LAZYIO) == 0 &&
  			 queue_invalidate)
  			; /* do nothing yet, invalidation will be queued */
  		else if (cap == ci->i_auth_cap)
  			check_caps = 1; /* check auth cap only */
  		else
  			check_caps = 2; /* check all caps */

  		cap->issued = newcaps;

  		cap->implemented |= newcaps;

  	} else if (cap->issued == newcaps) {
  		dout("caps unchanged: %s -> %s
  ",
  		     ceph_cap_string(cap->issued), ceph_cap_string(newcaps));
  	} else {
  		dout("grant: %s -> %s
  ", ceph_cap_string(cap->issued),
  		     ceph_cap_string(newcaps));
  		cap->issued = newcaps;
  		cap->implemented |= newcaps; /* add bits only, to
  					      * avoid stepping on a
  					      * pending revocation */
  		wake = 1;
  	}

  	BUG_ON(cap->issued & ~cap->implemented);

  	spin_unlock(&ci->i_ceph_lock);

  	if (writeback)

  		/*
  		 * queue inode for writeback: we can't actually call
  		 * filemap_write_and_wait, etc. from message handler
  		 * context.
  		 */

  		ceph_queue_writeback(inode);
  	if (queue_invalidate)
  		ceph_queue_invalidate(inode);

  	if (wake)

  		wake_up_all(&ci->i_cap_wq);

  
  	if (check_caps == 1)
  		ceph_check_caps(ci, CHECK_CAPS_NODELAY|CHECK_CAPS_AUTHONLY,
  				session);
  	else if (check_caps == 2)
  		ceph_check_caps(ci, CHECK_CAPS_NODELAY, session);
  	else
  		mutex_unlock(&session->s_mutex);

  }
  
  /*
   * Handle FLUSH_ACK from MDS, indicating that metadata we sent to the
   * MDS has been safely committed.
   */

  static void handle_cap_flush_ack(struct inode *inode, u64 flush_tid,

  				 struct ceph_mds_caps *m,
  				 struct ceph_mds_session *session,
  				 struct ceph_cap *cap)

  	__releases(ci->i_ceph_lock)

  {
  	struct ceph_inode_info *ci = ceph_inode(inode);

  	struct ceph_mds_client *mdsc = ceph_sb_to_client(inode->i_sb)->mdsc;

  	unsigned seq = le32_to_cpu(m->seq);
  	int dirty = le32_to_cpu(m->dirty);
  	int cleaned = 0;

  	int drop = 0;

  	int i;
  
  	for (i = 0; i < CEPH_CAP_BITS; i++)
  		if ((dirty & (1 << i)) &&
  		    flush_tid == ci->i_cap_flush_tid[i])
  			cleaned |= 1 << i;
  
  	dout("handle_cap_flush_ack inode %p mds%d seq %d on %s cleaned %s,"
  	     " flushing %s -> %s
  ",
  	     inode, session->s_mds, seq, ceph_cap_string(dirty),
  	     ceph_cap_string(cleaned), ceph_cap_string(ci->i_flushing_caps),
  	     ceph_cap_string(ci->i_flushing_caps & ~cleaned));
  
  	if (ci->i_flushing_caps == (ci->i_flushing_caps & ~cleaned))
  		goto out;

  	ci->i_flushing_caps &= ~cleaned;

  
  	spin_lock(&mdsc->cap_dirty_lock);
  	if (ci->i_flushing_caps == 0) {
  		list_del_init(&ci->i_flushing_item);
  		if (!list_empty(&session->s_cap_flushing))
  			dout(" mds%d still flushing cap on %p
  ",
  			     session->s_mds,
  			     &list_entry(session->s_cap_flushing.next,
  					 struct ceph_inode_info,
  					 i_flushing_item)->vfs_inode);
  		mdsc->num_cap_flushing--;

  		wake_up_all(&mdsc->cap_flushing_wq);

  		dout(" inode %p now !flushing
  ", inode);

  
  		if (ci->i_dirty_caps == 0) {
  			dout(" inode %p now clean
  ", inode);
  			BUG_ON(!list_empty(&ci->i_dirty_item));
  			drop = 1;

  			if (ci->i_wrbuffer_ref_head == 0) {
  				BUG_ON(!ci->i_head_snapc);
  				ceph_put_snap_context(ci->i_head_snapc);
  				ci->i_head_snapc = NULL;
  			}

  		} else {
  			BUG_ON(list_empty(&ci->i_dirty_item));

  		}

  	}
  	spin_unlock(&mdsc->cap_dirty_lock);

  	wake_up_all(&ci->i_cap_wq);

  
  out:

  	spin_unlock(&ci->i_ceph_lock);

  	if (drop)

  		iput(inode);
  }
  
  /*
   * Handle FLUSHSNAP_ACK.  MDS has flushed snap data to disk and we can
   * throw away our cap_snap.
   *
   * Caller hold s_mutex.
   */

  static void handle_cap_flushsnap_ack(struct inode *inode, u64 flush_tid,

  				     struct ceph_mds_caps *m,
  				     struct ceph_mds_session *session)
  {
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	u64 follows = le64_to_cpu(m->snap_follows);

  	struct ceph_cap_snap *capsnap;
  	int drop = 0;
  
  	dout("handle_cap_flushsnap_ack inode %p ci %p mds%d follows %lld
  ",
  	     inode, ci, session->s_mds, follows);

  	spin_lock(&ci->i_ceph_lock);

  	list_for_each_entry(capsnap, &ci->i_cap_snaps, ci_item) {
  		if (capsnap->follows == follows) {
  			if (capsnap->flush_tid != flush_tid) {
  				dout(" cap_snap %p follows %lld tid %lld !="
  				     " %lld
  ", capsnap, follows,
  				     flush_tid, capsnap->flush_tid);
  				break;
  			}
  			WARN_ON(capsnap->dirty_pages || capsnap->writing);

  			dout(" removing %p cap_snap %p follows %lld
  ",
  			     inode, capsnap, follows);

  			ceph_put_snap_context(capsnap->context);
  			list_del(&capsnap->ci_item);
  			list_del(&capsnap->flushing_item);
  			ceph_put_cap_snap(capsnap);
  			drop = 1;
  			break;
  		} else {
  			dout(" skipping cap_snap %p follows %lld
  ",
  			     capsnap, capsnap->follows);
  		}
  	}

  	spin_unlock(&ci->i_ceph_lock);

  	if (drop)
  		iput(inode);
  }
  
  /*
   * Handle TRUNC from MDS, indicating file truncation.
   *
   * caller hold s_mutex.
   */
  static void handle_cap_trunc(struct inode *inode,
  			     struct ceph_mds_caps *trunc,
  			     struct ceph_mds_session *session)

  	__releases(ci->i_ceph_lock)

  {
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	int mds = session->s_mds;
  	int seq = le32_to_cpu(trunc->seq);
  	u32 truncate_seq = le32_to_cpu(trunc->truncate_seq);
  	u64 truncate_size = le64_to_cpu(trunc->truncate_size);
  	u64 size = le64_to_cpu(trunc->size);
  	int implemented = 0;
  	int dirty = __ceph_caps_dirty(ci);
  	int issued = __ceph_caps_issued(ceph_inode(inode), &implemented);
  	int queue_trunc = 0;
  
  	issued |= implemented | dirty;
  
  	dout("handle_cap_trunc inode %p mds%d seq %d to %lld seq %d
  ",
  	     inode, mds, seq, truncate_size, truncate_seq);
  	queue_trunc = ceph_fill_file_size(inode, issued,
  					  truncate_seq, truncate_size, size);

  	spin_unlock(&ci->i_ceph_lock);

  
  	if (queue_trunc)

  		ceph_queue_vmtruncate(inode);

  }
  
  /*
   * Handle EXPORT from MDS.  Cap is being migrated _from_ this mds to a
   * different one.  If we are the most recent migration we've seen (as
   * indicated by mseq), make note of the migrating cap bits for the
   * duration (until we see the corresponding IMPORT).
   *
   * caller holds s_mutex
   */
  static void handle_cap_export(struct inode *inode, struct ceph_mds_caps *ex,

  			      struct ceph_mds_session *session,
  			      int *open_target_sessions)

  {

  	struct ceph_mds_client *mdsc = ceph_inode_to_client(inode)->mdsc;

  	struct ceph_inode_info *ci = ceph_inode(inode);
  	int mds = session->s_mds;
  	unsigned mseq = le32_to_cpu(ex->migrate_seq);
  	struct ceph_cap *cap = NULL, *t;
  	struct rb_node *p;
  	int remember = 1;
  
  	dout("handle_cap_export inode %p ci %p mds%d mseq %d
  ",
  	     inode, ci, mds, mseq);

  	spin_lock(&ci->i_ceph_lock);

  
  	/* make sure we haven't seen a higher mseq */
  	for (p = rb_first(&ci->i_caps); p; p = rb_next(p)) {
  		t = rb_entry(p, struct ceph_cap, ci_node);
  		if (ceph_seq_cmp(t->mseq, mseq) > 0) {
  			dout(" higher mseq on cap from mds%d
  ",
  			     t->session->s_mds);
  			remember = 0;
  		}
  		if (t->session->s_mds == mds)
  			cap = t;
  	}
  
  	if (cap) {
  		if (remember) {
  			/* make note */
  			ci->i_cap_exporting_mds = mds;
  			ci->i_cap_exporting_mseq = mseq;
  			ci->i_cap_exporting_issued = cap->issued;

  
  			/*
  			 * make sure we have open sessions with all possible
  			 * export targets, so that we get the matching IMPORT
  			 */
  			*open_target_sessions = 1;

  
  			/*
  			 * we can't flush dirty caps that we've seen the
  			 * EXPORT but no IMPORT for
  			 */
  			spin_lock(&mdsc->cap_dirty_lock);
  			if (!list_empty(&ci->i_dirty_item)) {
  				dout(" moving %p to cap_dirty_migrating
  ",
  				     inode);
  				list_move(&ci->i_dirty_item,
  					  &mdsc->cap_dirty_migrating);
  			}
  			spin_unlock(&mdsc->cap_dirty_lock);

  		}

  		__ceph_remove_cap(cap);

  	}

  	/* else, we already released it */

  	spin_unlock(&ci->i_ceph_lock);

  }
  
  /*
   * Handle cap IMPORT.  If there are temp bits from an older EXPORT,
   * clean them up.
   *
   * caller holds s_mutex.
   */
  static void handle_cap_import(struct ceph_mds_client *mdsc,
  			      struct inode *inode, struct ceph_mds_caps *im,
  			      struct ceph_mds_session *session,
  			      void *snaptrace, int snaptrace_len)
  {
  	struct ceph_inode_info *ci = ceph_inode(inode);
  	int mds = session->s_mds;
  	unsigned issued = le32_to_cpu(im->caps);
  	unsigned wanted = le32_to_cpu(im->wanted);
  	unsigned seq = le32_to_cpu(im->seq);
  	unsigned mseq = le32_to_cpu(im->migrate_seq);
  	u64 realmino = le64_to_cpu(im->realm);
  	u64 cap_id = le64_to_cpu(im->cap_id);
  
  	if (ci->i_cap_exporting_mds >= 0 &&
  	    ceph_seq_cmp(ci->i_cap_exporting_mseq, mseq) < 0) {
  		dout("handle_cap_import inode %p ci %p mds%d mseq %d"
  		     " - cleared exporting from mds%d
  ",
  		     inode, ci, mds, mseq,
  		     ci->i_cap_exporting_mds);
  		ci->i_cap_exporting_issued = 0;
  		ci->i_cap_exporting_mseq = 0;
  		ci->i_cap_exporting_mds = -1;

  
  		spin_lock(&mdsc->cap_dirty_lock);
  		if (!list_empty(&ci->i_dirty_item)) {
  			dout(" moving %p back to cap_dirty
  ", inode);
  			list_move(&ci->i_dirty_item, &mdsc->cap_dirty);
  		}
  		spin_unlock(&mdsc->cap_dirty_lock);

  	} else {
  		dout("handle_cap_import inode %p ci %p mds%d mseq %d
  ",
  		     inode, ci, mds, mseq);
  	}
  
  	down_write(&mdsc->snap_rwsem);
  	ceph_update_snap_trace(mdsc, snaptrace, snaptrace+snaptrace_len,
  			       false);
  	downgrade_write(&mdsc->snap_rwsem);
  	ceph_add_cap(inode, session, cap_id, -1,
  		     issued, wanted, seq, mseq, realmino, CEPH_CAP_FLAG_AUTH,
  		     NULL /* no caps context */);

  	kick_flushing_inode_caps(mdsc, session, inode);

  	up_read(&mdsc->snap_rwsem);

  
  	/* make sure we re-request max_size, if necessary */

  	spin_lock(&ci->i_ceph_lock);

  	ci->i_requested_max_size = 0;

  	spin_unlock(&ci->i_ceph_lock);

  }
  
  /*
   * Handle a caps message from the MDS.
   *
   * Identify the appropriate session, inode, and call the right handler
   * based on the cap op.
   */
  void ceph_handle_caps(struct ceph_mds_session *session,
  		      struct ceph_msg *msg)
  {
  	struct ceph_mds_client *mdsc = session->s_mdsc;

  	struct super_block *sb = mdsc->fsc->sb;

  	struct inode *inode;

  	struct ceph_inode_info *ci;

  	struct ceph_cap *cap;
  	struct ceph_mds_caps *h;

  	int mds = session->s_mds;

  	int op;

  	u32 seq, mseq;

  	struct ceph_vino vino;
  	u64 cap_id;
  	u64 size, max_size;

  	u64 tid;

  	void *snaptrace;

  	size_t snaptrace_len;
  	void *flock;
  	u32 flock_len;

  	int open_target_sessions = 0;

  
  	dout("handle_caps from mds%d
  ", mds);
  
  	/* decode */

  	tid = le64_to_cpu(msg->hdr.tid);

  	if (msg->front.iov_len < sizeof(*h))
  		goto bad;
  	h = msg->front.iov_base;
  	op = le32_to_cpu(h->op);
  	vino.ino = le64_to_cpu(h->ino);
  	vino.snap = CEPH_NOSNAP;
  	cap_id = le64_to_cpu(h->cap_id);
  	seq = le32_to_cpu(h->seq);

  	mseq = le32_to_cpu(h->migrate_seq);

  	size = le64_to_cpu(h->size);
  	max_size = le64_to_cpu(h->max_size);

  	snaptrace = h + 1;
  	snaptrace_len = le32_to_cpu(h->snap_trace_len);
  
  	if (le16_to_cpu(msg->hdr.version) >= 2) {
  		void *p, *end;
  
  		p = snaptrace + snaptrace_len;
  		end = msg->front.iov_base + msg->front.iov_len;
  		ceph_decode_32_safe(&p, end, flock_len, bad);
  		flock = p;
  	} else {
  		flock = NULL;
  		flock_len = 0;
  	}

  	mutex_lock(&session->s_mutex);
  	session->s_seq++;
  	dout(" mds%d seq %lld cap seq %u
  ", session->s_mds, session->s_seq,
  	     (unsigned)seq);
  
  	/* lookup ino */
  	inode = ceph_find_inode(sb, vino);

  	ci = ceph_inode(inode);

  	dout(" op %s ino %llx.%llx inode %p
  ", ceph_cap_op_name(op), vino.ino,
  	     vino.snap, inode);
  	if (!inode) {
  		dout(" i don't have ino %llx
  ", vino.ino);

  
  		if (op == CEPH_CAP_OP_IMPORT)
  			__queue_cap_release(session, vino.ino, cap_id,
  					    mseq, seq);

  		goto flush_cap_releases;

  	}
  
  	/* these will work even if we don't have a cap yet */
  	switch (op) {
  	case CEPH_CAP_OP_FLUSHSNAP_ACK:

  		handle_cap_flushsnap_ack(inode, tid, h, session);

  		goto done;
  
  	case CEPH_CAP_OP_EXPORT:

  		handle_cap_export(inode, h, session, &open_target_sessions);

  		goto done;
  
  	case CEPH_CAP_OP_IMPORT:
  		handle_cap_import(mdsc, inode, h, session,

  				  snaptrace, snaptrace_len);

  		ceph_check_caps(ceph_inode(inode), 0, session);

  		goto done_unlocked;

  	}
  
  	/* the rest require a cap */

  	spin_lock(&ci->i_ceph_lock);

  	cap = __get_cap_for_mds(ceph_inode(inode), mds);
  	if (!cap) {

  		dout(" no cap on %p ino %llx.%llx from mds%d
  ",

  		     inode, ceph_ino(inode), ceph_snap(inode), mds);

  		spin_unlock(&ci->i_ceph_lock);

  		goto flush_cap_releases;

  	}

  	/* note that each of these drops i_ceph_lock for us */

  	switch (op) {
  	case CEPH_CAP_OP_REVOKE:
  	case CEPH_CAP_OP_GRANT:

  		handle_cap_grant(inode, h, session, cap, msg->middle);
  		goto done_unlocked;

  
  	case CEPH_CAP_OP_FLUSH_ACK:

  		handle_cap_flush_ack(inode, tid, h, session, cap);

  		break;
  
  	case CEPH_CAP_OP_TRUNC:
  		handle_cap_trunc(inode, h, session);
  		break;
  
  	default:

  		spin_unlock(&ci->i_ceph_lock);

  		pr_err("ceph_handle_caps: unknown cap op %d %s
  ", op,
  		       ceph_cap_op_name(op));
  	}

  	goto done;
  
  flush_cap_releases:
  	/*
  	 * send any full release message to try to move things
  	 * along for the mds (who clearly thinks we still have this
  	 * cap).
  	 */
  	ceph_add_cap_releases(mdsc, session);
  	ceph_send_cap_releases(mdsc, session);

  done:

  	mutex_unlock(&session->s_mutex);
  done_unlocked:

  	if (inode)
  		iput(inode);

  	if (open_target_sessions)
  		ceph_mdsc_open_export_target_sessions(mdsc, session);

  	return;
  
  bad:
  	pr_err("ceph_handle_caps: corrupt message
  ");

  	ceph_msg_dump(msg);

  	return;
  }
  
  /*
   * Delayed work handler to process end of delayed cap release LRU list.
   */

  void ceph_check_delayed_caps(struct ceph_mds_client *mdsc)

  {
  	struct ceph_inode_info *ci;
  	int flags = CHECK_CAPS_NODELAY;

  	dout("check_delayed_caps
  ");
  	while (1) {
  		spin_lock(&mdsc->cap_delay_lock);
  		if (list_empty(&mdsc->cap_delay_list))
  			break;
  		ci = list_first_entry(&mdsc->cap_delay_list,
  				      struct ceph_inode_info,
  				      i_cap_delay_list);
  		if ((ci->i_ceph_flags & CEPH_I_FLUSH) == 0 &&
  		    time_before(jiffies, ci->i_hold_caps_max))
  			break;
  		list_del_init(&ci->i_cap_delay_list);
  		spin_unlock(&mdsc->cap_delay_lock);
  		dout("check_delayed_caps on %p
  ", &ci->vfs_inode);
  		ceph_check_caps(ci, flags, NULL);
  	}
  	spin_unlock(&mdsc->cap_delay_lock);
  }
  
  /*

   * Flush all dirty caps to the mds
   */
  void ceph_flush_dirty_caps(struct ceph_mds_client *mdsc)
  {

  	struct ceph_inode_info *ci;
  	struct inode *inode;

  
  	dout("flush_dirty_caps
  ");
  	spin_lock(&mdsc->cap_dirty_lock);

  	while (!list_empty(&mdsc->cap_dirty)) {
  		ci = list_first_entry(&mdsc->cap_dirty, struct ceph_inode_info,
  				      i_dirty_item);

  		inode = &ci->vfs_inode;
  		ihold(inode);

  		dout("flush_dirty_caps %p
  ", inode);

  		spin_unlock(&mdsc->cap_dirty_lock);

  		ceph_check_caps(ci, CHECK_CAPS_NODELAY|CHECK_CAPS_FLUSH, NULL);
  		iput(inode);

  		spin_lock(&mdsc->cap_dirty_lock);
  	}
  	spin_unlock(&mdsc->cap_dirty_lock);

  	dout("flush_dirty_caps done
  ");

  }
  
  /*

   * Drop open file reference.  If we were the last open file,
   * we may need to release capabilities to the MDS (or schedule
   * their delayed release).
   */
  void ceph_put_fmode(struct ceph_inode_info *ci, int fmode)
  {
  	struct inode *inode = &ci->vfs_inode;
  	int last = 0;

  	spin_lock(&ci->i_ceph_lock);

  	dout("put_fmode %p fmode %d %d -> %d
  ", inode, fmode,
  	     ci->i_nr_by_mode[fmode], ci->i_nr_by_mode[fmode]-1);
  	BUG_ON(ci->i_nr_by_mode[fmode] == 0);
  	if (--ci->i_nr_by_mode[fmode] == 0)
  		last++;