/* CacheFiles path walking and related routines
   *
   * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public Licence
   * as published by the Free Software Foundation; either version
   * 2 of the Licence, or (at your option) any later version.
   */
  
  #include <linux/module.h>
  #include <linux/sched.h>
  #include <linux/file.h>
  #include <linux/fs.h>
  #include <linux/fsnotify.h>
  #include <linux/quotaops.h>
  #include <linux/xattr.h>
  #include <linux/mount.h>
  #include <linux/namei.h>
  #include <linux/security.h>

  #include <linux/slab.h>

  #include <linux/xattr.h>

  #include "internal.h"

  #define CACHEFILES_KEYBUF_SIZE 512
  
  /*
   * dump debugging info about an object
   */
  static noinline
  void __cachefiles_printk_object(struct cachefiles_object *object,
  				const char *prefix,
  				u8 *keybuf)
  {
  	struct fscache_cookie *cookie;
  	unsigned keylen, loop;

  	pr_err("%sobject: OBJ%x
  ", prefix, object->fscache.debug_id);
  	pr_err("%sobjstate=%s fl=%lx wbusy=%x ev=%lx[%lx]
  ",

  	       prefix, object->fscache.state->name,

  	       object->fscache.flags, work_busy(&object->fscache.work),

  	       object->fscache.events, object->fscache.event_mask);

  	pr_err("%sops=%u inp=%u exc=%u
  ",

  	       prefix, object->fscache.n_ops, object->fscache.n_in_progress,
  	       object->fscache.n_exclusive);

  	pr_err("%sparent=%p
  ",

  	       prefix, object->fscache.parent);
  
  	spin_lock(&object->fscache.lock);
  	cookie = object->fscache.cookie;
  	if (cookie) {

  		pr_err("%scookie=%p [pr=%p nd=%p fl=%lx]
  ",

  		       prefix,
  		       object->fscache.cookie,
  		       object->fscache.cookie->parent,
  		       object->fscache.cookie->netfs_data,
  		       object->fscache.cookie->flags);

  		if (keybuf && cookie->def)

  			keylen = cookie->def->get_key(cookie->netfs_data, keybuf,
  						      CACHEFILES_KEYBUF_SIZE);
  		else
  			keylen = 0;
  	} else {

  		pr_err("%scookie=NULL
  ", prefix);

  		keylen = 0;
  	}
  	spin_unlock(&object->fscache.lock);
  
  	if (keylen) {

  		pr_err("%skey=[%u] '", prefix, keylen);

  		for (loop = 0; loop < keylen; loop++)

  			pr_cont("%02x", keybuf[loop]);
  		pr_cont("'
  ");

  	}
  }
  
  /*
   * dump debugging info about a pair of objects
   */
  static noinline void cachefiles_printk_object(struct cachefiles_object *object,
  					      struct cachefiles_object *xobject)
  {
  	u8 *keybuf;
  
  	keybuf = kmalloc(CACHEFILES_KEYBUF_SIZE, GFP_NOIO);
  	if (object)
  		__cachefiles_printk_object(object, "", keybuf);
  	if (xobject)
  		__cachefiles_printk_object(xobject, "x", keybuf);
  	kfree(keybuf);
  }

  /*

   * mark the owner of a dentry, if there is one, to indicate that that dentry
   * has been preemptively deleted
   * - the caller must hold the i_mutex on the dentry's parent as required to
   *   call vfs_unlink(), vfs_rmdir() or vfs_rename()
   */
  static void cachefiles_mark_object_buried(struct cachefiles_cache *cache,

  					  struct dentry *dentry,
  					  enum fscache_why_object_killed why)

  {
  	struct cachefiles_object *object;
  	struct rb_node *p;

  	_enter(",'%pd'", dentry);

  
  	write_lock(&cache->active_lock);
  
  	p = cache->active_nodes.rb_node;
  	while (p) {
  		object = rb_entry(p, struct cachefiles_object, active_node);
  		if (object->dentry > dentry)
  			p = p->rb_left;
  		else if (object->dentry < dentry)
  			p = p->rb_right;
  		else
  			goto found_dentry;
  	}
  
  	write_unlock(&cache->active_lock);
  	_leave(" [no owner]");
  	return;
  
  	/* found the dentry for  */
  found_dentry:
  	kdebug("preemptive burial: OBJ%x [%s] %p",
  	       object->fscache.debug_id,

  	       object->fscache.state->name,

  	       dentry);

  	if (fscache_object_is_live(&object->fscache)) {

  		pr_err("
  ");

  		pr_err("Error: Can't preemptively bury live object
  ");

  		cachefiles_printk_object(object, NULL);

  	} else {
  		if (why != FSCACHE_OBJECT_IS_STALE)
  			fscache_object_mark_killed(&object->fscache, why);

  	}
  
  	write_unlock(&cache->active_lock);
  	_leave(" [owner marked]");
  }
  
  /*

   * record the fact that an object is now active
   */

  static int cachefiles_mark_object_active(struct cachefiles_cache *cache,
  					 struct cachefiles_object *object)

  {
  	struct cachefiles_object *xobject;
  	struct rb_node **_p, *_parent = NULL;
  	struct dentry *dentry;
  
  	_enter(",%p", object);
  
  try_again:
  	write_lock(&cache->active_lock);

  	if (test_and_set_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags)) {

  		pr_err("Error: Object already active
  ");

  		cachefiles_printk_object(object, NULL);

  		BUG();

  	}

  
  	dentry = object->dentry;
  	_p = &cache->active_nodes.rb_node;
  	while (*_p) {
  		_parent = *_p;
  		xobject = rb_entry(_parent,
  				   struct cachefiles_object, active_node);
  
  		ASSERT(xobject != object);
  
  		if (xobject->dentry > dentry)
  			_p = &(*_p)->rb_left;
  		else if (xobject->dentry < dentry)
  			_p = &(*_p)->rb_right;
  		else
  			goto wait_for_old_object;
  	}
  
  	rb_link_node(&object->active_node, _parent, _p);
  	rb_insert_color(&object->active_node, &cache->active_nodes);
  
  	write_unlock(&cache->active_lock);

  	_leave(" = 0");
  	return 0;

  
  	/* an old object from a previous incarnation is hogging the slot - we
  	 * need to wait for it to be destroyed */
  wait_for_old_object:

  	if (fscache_object_is_live(&xobject->fscache)) {

  		pr_err("
  ");

  		pr_err("Error: Unexpected object collision
  ");

  		cachefiles_printk_object(object, xobject);

  		BUG();
  	}
  	atomic_inc(&xobject->usage);
  	write_unlock(&cache->active_lock);

  	if (test_bit(CACHEFILES_OBJECT_ACTIVE, &xobject->flags)) {
  		wait_queue_head_t *wq;
  
  		signed long timeout = 60 * HZ;
  		wait_queue_t wait;
  		bool requeue;
  
  		/* if the object we're waiting for is queued for processing,
  		 * then just put ourselves on the queue behind it */

  		if (work_pending(&xobject->fscache.work)) {

  			_debug("queue OBJ%x behind OBJ%x immediately",
  			       object->fscache.debug_id,
  			       xobject->fscache.debug_id);
  			goto requeue;
  		}
  
  		/* otherwise we sleep until either the object we're waiting for

  		 * is done, or the fscache_object is congested */

  		wq = bit_waitqueue(&xobject->flags, CACHEFILES_OBJECT_ACTIVE);
  		init_wait(&wait);
  		requeue = false;
  		do {
  			prepare_to_wait(wq, &wait, TASK_UNINTERRUPTIBLE);
  			if (!test_bit(CACHEFILES_OBJECT_ACTIVE, &xobject->flags))
  				break;

  
  			requeue = fscache_object_sleep_till_congested(&timeout);

  		} while (timeout > 0 && !requeue);
  		finish_wait(wq, &wait);
  
  		if (requeue &&
  		    test_bit(CACHEFILES_OBJECT_ACTIVE, &xobject->flags)) {
  			_debug("queue OBJ%x behind OBJ%x after wait",
  			       object->fscache.debug_id,
  			       xobject->fscache.debug_id);
  			goto requeue;
  		}
  
  		if (timeout <= 0) {

  			pr_err("
  ");

  			pr_err("Error: Overlong wait for old active object to go away
  ");

  			cachefiles_printk_object(object, xobject);
  			goto requeue;
  		}
  	}
  
  	ASSERT(!test_bit(CACHEFILES_OBJECT_ACTIVE, &xobject->flags));

  
  	cache->cache.ops->put_object(&xobject->fscache);
  	goto try_again;

  
  requeue:
  	clear_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags);
  	cache->cache.ops->put_object(&xobject->fscache);
  	_leave(" = -ETIMEDOUT");
  	return -ETIMEDOUT;

  }
  
  /*

   * Mark an object as being inactive.
   */
  void cachefiles_mark_object_inactive(struct cachefiles_cache *cache,

  				     struct cachefiles_object *object,
  				     blkcnt_t i_blocks)

  {
  	write_lock(&cache->active_lock);
  	rb_erase(&object->active_node, &cache->active_nodes);
  	clear_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags);
  	write_unlock(&cache->active_lock);
  
  	wake_up_bit(&object->flags, CACHEFILES_OBJECT_ACTIVE);
  
  	/* This object can now be culled, so we need to let the daemon know
  	 * that there is something it can remove if it needs to.
  	 */

  	atomic_long_add(i_blocks, &cache->b_released);

  	if (atomic_inc_return(&cache->f_released))
  		cachefiles_state_changed(cache);
  }
  
  /*

   * delete an object representation from the cache
   * - file backed objects are unlinked
   * - directory backed objects are stuffed into the graveyard for userspace to
   *   delete
   * - unlocks the directory mutex
   */
  static int cachefiles_bury_object(struct cachefiles_cache *cache,
  				  struct dentry *dir,

  				  struct dentry *rep,

  				  bool preemptive,
  				  enum fscache_why_object_killed why)

  {
  	struct dentry *grave, *trap;

  	struct path path, path_to_graveyard;

  	char nbuffer[8 + 8 + 1];
  	int ret;

  	_enter(",'%pd','%pd'", dir, rep);

  	_debug("remove %p from %p", rep, dir);

  	/* non-directories can just be unlinked */

  	if (!d_is_dir(rep)) {

  		_debug("unlink stale object");

  		path.mnt = cache->mnt;
  		path.dentry = dir;
  		ret = security_path_unlink(&path, rep);
  		if (ret < 0) {
  			cachefiles_io_error(cache, "Unlink security error");
  		} else {

  			ret = vfs_unlink(d_inode(dir), rep, NULL);

  
  			if (preemptive)

  				cachefiles_mark_object_buried(cache, rep, why);

  		}

  		inode_unlock(d_inode(dir));

  
  		if (ret == -EIO)
  			cachefiles_io_error(cache, "Unlink failed");
  
  		_leave(" = %d", ret);
  		return ret;
  	}
  
  	/* directories have to be moved to the graveyard */
  	_debug("move stale object to graveyard");

  	inode_unlock(d_inode(dir));

  
  try_again:
  	/* first step is to make up a grave dentry in the graveyard */
  	sprintf(nbuffer, "%08x%08x",
  		(uint32_t) get_seconds(),
  		(uint32_t) atomic_inc_return(&cache->gravecounter));
  
  	/* do the multiway lock magic */
  	trap = lock_rename(cache->graveyard, dir);
  
  	/* do some checks before getting the grave dentry */
  	if (rep->d_parent != dir) {
  		/* the entry was probably culled when we dropped the parent dir
  		 * lock */
  		unlock_rename(cache->graveyard, dir);
  		_leave(" = 0 [culled?]");
  		return 0;
  	}

  	if (!d_can_lookup(cache->graveyard)) {

  		unlock_rename(cache->graveyard, dir);
  		cachefiles_io_error(cache, "Graveyard no longer a directory");
  		return -EIO;
  	}
  
  	if (trap == rep) {
  		unlock_rename(cache->graveyard, dir);
  		cachefiles_io_error(cache, "May not make directory loop");
  		return -EIO;
  	}
  
  	if (d_mountpoint(rep)) {
  		unlock_rename(cache->graveyard, dir);
  		cachefiles_io_error(cache, "Mountpoint in cache");
  		return -EIO;
  	}
  
  	grave = lookup_one_len(nbuffer, cache->graveyard, strlen(nbuffer));
  	if (IS_ERR(grave)) {
  		unlock_rename(cache->graveyard, dir);
  
  		if (PTR_ERR(grave) == -ENOMEM) {
  			_leave(" = -ENOMEM");
  			return -ENOMEM;
  		}
  
  		cachefiles_io_error(cache, "Lookup error %ld",
  				    PTR_ERR(grave));
  		return -EIO;
  	}

  	if (d_is_positive(grave)) {

  		unlock_rename(cache->graveyard, dir);
  		dput(grave);
  		grave = NULL;
  		cond_resched();
  		goto try_again;
  	}
  
  	if (d_mountpoint(grave)) {
  		unlock_rename(cache->graveyard, dir);
  		dput(grave);
  		cachefiles_io_error(cache, "Mountpoint in graveyard");
  		return -EIO;
  	}
  
  	/* target should not be an ancestor of source */
  	if (trap == grave) {
  		unlock_rename(cache->graveyard, dir);
  		dput(grave);
  		cachefiles_io_error(cache, "May not make directory loop");
  		return -EIO;
  	}
  
  	/* attempt the rename */

  	path.mnt = cache->mnt;
  	path.dentry = dir;
  	path_to_graveyard.mnt = cache->mnt;
  	path_to_graveyard.dentry = cache->graveyard;

  	ret = security_path_rename(&path, rep, &path_to_graveyard, grave, 0);

  	if (ret < 0) {
  		cachefiles_io_error(cache, "Rename security error %d", ret);
  	} else {

  		ret = vfs_rename(d_inode(dir), rep,
  				 d_inode(cache->graveyard), grave, NULL, 0);

  		if (ret != 0 && ret != -ENOMEM)
  			cachefiles_io_error(cache,
  					    "Rename failed with error %d", ret);

  		if (preemptive)

  			cachefiles_mark_object_buried(cache, rep, why);

  	}

  	unlock_rename(cache->graveyard, dir);
  	dput(grave);
  	_leave(" = 0");
  	return 0;
  }
  
  /*
   * delete an object representation from the cache
   */
  int cachefiles_delete_object(struct cachefiles_cache *cache,
  			     struct cachefiles_object *object)
  {
  	struct dentry *dir;
  	int ret;

  	_enter(",OBJ%x{%p}", object->fscache.debug_id, object->dentry);

  
  	ASSERT(object->dentry);

  	ASSERT(d_backing_inode(object->dentry));

  	ASSERT(object->dentry->d_parent);
  
  	dir = dget_parent(object->dentry);

  	inode_lock_nested(d_inode(dir), I_MUTEX_PARENT);

  	if (test_bit(FSCACHE_OBJECT_KILLED_BY_CACHE, &object->fscache.flags)) {

  		/* object allocation for the same key preemptively deleted this
  		 * object's file so that it could create its own file */
  		_debug("object preemptively buried");

  		inode_unlock(d_inode(dir));

  		ret = 0;

  	} else {
  		/* we need to check that our parent is _still_ our parent - it
  		 * may have been renamed */
  		if (dir == object->dentry->d_parent) {
  			ret = cachefiles_bury_object(cache, dir,

  						     object->dentry, false,
  						     FSCACHE_OBJECT_WAS_RETIRED);

  		} else {
  			/* it got moved, presumably by cachefilesd culling it,
  			 * so it's no longer in the key path and we can ignore
  			 * it */

  			inode_unlock(d_inode(dir));

  			ret = 0;
  		}

  	}

  
  	dput(dir);
  	_leave(" = %d", ret);
  	return ret;
  }
  
  /*
   * walk from the parent object to the child object through the backing
   * filesystem, creating directories as we go
   */
  int cachefiles_walk_to_object(struct cachefiles_object *parent,
  			      struct cachefiles_object *object,
  			      const char *key,
  			      struct cachefiles_xattr *auxdata)
  {
  	struct cachefiles_cache *cache;
  	struct dentry *dir, *next = NULL;

  	struct path path;

  	unsigned long start;
  	const char *name;
  	int ret, nlen;

  	_enter("OBJ%x{%p},OBJ%x,%s,",
  	       parent->fscache.debug_id, parent->dentry,
  	       object->fscache.debug_id, key);

  
  	cache = container_of(parent->fscache.cache,
  			     struct cachefiles_cache, cache);

  	path.mnt = cache->mnt;

  
  	ASSERT(parent->dentry);

  	ASSERT(d_backing_inode(parent->dentry));

  	if (!(d_is_dir(parent->dentry))) {

  		// TODO: convert file to dir
  		_leave("looking up in none directory");
  		return -ENOBUFS;
  	}
  
  	dir = dget(parent->dentry);
  
  advance:
  	/* attempt to transit the first directory component */
  	name = key;
  	nlen = strlen(key);
  
  	/* key ends in a double NUL */
  	key = key + nlen + 1;
  	if (!*key)
  		key = NULL;
  
  lookup_again:
  	/* search the current directory for the element name */
  	_debug("lookup '%s'", name);

  	inode_lock_nested(d_inode(dir), I_MUTEX_PARENT);

  
  	start = jiffies;
  	next = lookup_one_len(name, dir, nlen);
  	cachefiles_hist(cachefiles_lookup_histogram, start);
  	if (IS_ERR(next))
  		goto lookup_error;

  	_debug("next -> %p %s", next, d_backing_inode(next) ? "positive" : "negative");

  
  	if (!key)

  		object->new = !d_backing_inode(next);

  
  	/* if this element of the path doesn't exist, then the lookup phase
  	 * failed, and we can release any readers in the certain knowledge that
  	 * there's nothing for them to actually read */

  	if (d_is_negative(next))

  		fscache_object_lookup_negative(&object->fscache);
  
  	/* we need to create the object if it's negative */
  	if (key || object->type == FSCACHE_COOKIE_TYPE_INDEX) {
  		/* index objects and intervening tree levels must be subdirs */

  		if (d_is_negative(next)) {

  			ret = cachefiles_has_space(cache, 1, 0);
  			if (ret < 0)

  				goto no_space_error;

  			path.dentry = dir;
  			ret = security_path_mkdir(&path, next, 0);
  			if (ret < 0)
  				goto create_error;

  			start = jiffies;

  			ret = vfs_mkdir(d_inode(dir), next, 0);

  			cachefiles_hist(cachefiles_mkdir_histogram, start);
  			if (ret < 0)
  				goto create_error;

  			ASSERT(d_backing_inode(next));

  
  			_debug("mkdir -> %p{%p{ino=%lu}}",

  			       next, d_backing_inode(next), d_backing_inode(next)->i_ino);

  		} else if (!d_can_lookup(next)) {

  			pr_err("inode %lu is not a directory
  ",

  			       d_backing_inode(next)->i_ino);

  			ret = -ENOBUFS;
  			goto error;
  		}
  
  	} else {
  		/* non-index objects start out life as files */

  		if (d_is_negative(next)) {

  			ret = cachefiles_has_space(cache, 1, 0);
  			if (ret < 0)

  				goto no_space_error;

  			path.dentry = dir;
  			ret = security_path_mknod(&path, next, S_IFREG, 0);
  			if (ret < 0)
  				goto create_error;

  			start = jiffies;

  			ret = vfs_create(d_inode(dir), next, S_IFREG, true);

  			cachefiles_hist(cachefiles_create_histogram, start);
  			if (ret < 0)
  				goto create_error;

  			ASSERT(d_backing_inode(next));

  
  			_debug("create -> %p{%p{ino=%lu}}",

  			       next, d_backing_inode(next), d_backing_inode(next)->i_ino);

  		} else if (!d_can_lookup(next) &&

  			   !d_is_reg(next)

  			   ) {

  			pr_err("inode %lu is not a file or directory
  ",

  			       d_backing_inode(next)->i_ino);

  			ret = -ENOBUFS;
  			goto error;
  		}
  	}
  
  	/* process the next component */
  	if (key) {
  		_debug("advance");

  		inode_unlock(d_inode(dir));

  		dput(dir);
  		dir = next;
  		next = NULL;
  		goto advance;
  	}
  
  	/* we've found the object we were looking for */
  	object->dentry = next;
  
  	/* if we've found that the terminal object exists, then we need to
  	 * check its attributes and delete it if it's out of date */
  	if (!object->new) {

  		_debug("validate '%pd'", next);

  
  		ret = cachefiles_check_object_xattr(object, auxdata);
  		if (ret == -ESTALE) {
  			/* delete the object (the deleter drops the directory
  			 * mutex) */
  			object->dentry = NULL;

  			ret = cachefiles_bury_object(cache, dir, next, true,
  						     FSCACHE_OBJECT_IS_STALE);

  			dput(next);
  			next = NULL;
  
  			if (ret < 0)
  				goto delete_error;
  
  			_debug("redo lookup");

  			fscache_object_retrying_stale(&object->fscache);

  			goto lookup_again;
  		}
  	}
  
  	/* note that we're now using this object */

  	ret = cachefiles_mark_object_active(cache, object);

  	inode_unlock(d_inode(dir));

  	dput(dir);
  	dir = NULL;

  	if (ret == -ETIMEDOUT)
  		goto mark_active_timed_out;

  	_debug("=== OBTAINED_OBJECT ===");
  
  	if (object->new) {
  		/* attach data to a newly constructed terminal object */
  		ret = cachefiles_set_object_xattr(object, auxdata);
  		if (ret < 0)
  			goto check_error;
  	} else {
  		/* always update the atime on an object we've just looked up
  		 * (this is used to keep track of culling, and atimes are only
  		 * updated by read, write and readdir but not lookup or
  		 * open) */

  		path.dentry = next;
  		touch_atime(&path);

  	}
  
  	/* open a file interface onto a data file */
  	if (object->type != FSCACHE_COOKIE_TYPE_INDEX) {

  		if (d_is_reg(object->dentry)) {

  			const struct address_space_operations *aops;
  
  			ret = -EPERM;

  			aops = d_backing_inode(object->dentry)->i_mapping->a_ops;

  			if (!aops->bmap)
  				goto check_error;

  			if (object->dentry->d_sb->s_blocksize > PAGE_SIZE)
  				goto check_error;

  
  			object->backer = object->dentry;
  		} else {
  			BUG(); // TODO: open file in data-class subdir
  		}
  	}
  
  	object->new = 0;
  	fscache_obtained_object(&object->fscache);

  	_leave(" = 0 [%lu]", d_backing_inode(object->dentry)->i_ino);

  	return 0;

  no_space_error:
  	fscache_object_mark_killed(&object->fscache, FSCACHE_OBJECT_NO_SPACE);

  create_error:
  	_debug("create error %d", ret);
  	if (ret == -EIO)
  		cachefiles_io_error(cache, "Create/mkdir failed");
  	goto error;

  mark_active_timed_out:
  	_debug("mark active timed out");
  	goto release_dentry;

  check_error:
  	_debug("check error %d", ret);

  	cachefiles_mark_object_inactive(
  		cache, object, d_backing_inode(object->dentry)->i_blocks);

  release_dentry:

  	dput(object->dentry);
  	object->dentry = NULL;
  	goto error_out;
  
  delete_error:
  	_debug("delete error %d", ret);
  	goto error_out2;
  
  lookup_error:
  	_debug("lookup error %ld", PTR_ERR(next));
  	ret = PTR_ERR(next);
  	if (ret == -EIO)
  		cachefiles_io_error(cache, "Lookup failed");
  	next = NULL;
  error:

  	inode_unlock(d_inode(dir));

  	dput(next);
  error_out2:
  	dput(dir);
  error_out:

  	_leave(" = error %d", -ret);
  	return ret;
  }
  
  /*
   * get a subdirectory
   */
  struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
  					struct dentry *dir,
  					const char *dirname)
  {
  	struct dentry *subdir;
  	unsigned long start;

  	struct path path;

  	int ret;
  
  	_enter(",,%s", dirname);
  
  	/* search the current directory for the element name */

  	inode_lock(d_inode(dir));

  
  	start = jiffies;
  	subdir = lookup_one_len(dirname, dir, strlen(dirname));
  	cachefiles_hist(cachefiles_lookup_histogram, start);
  	if (IS_ERR(subdir)) {
  		if (PTR_ERR(subdir) == -ENOMEM)
  			goto nomem_d_alloc;
  		goto lookup_error;
  	}
  
  	_debug("subdir -> %p %s",

  	       subdir, d_backing_inode(subdir) ? "positive" : "negative");

  
  	/* we need to create the subdir if it doesn't exist yet */

  	if (d_is_negative(subdir)) {

  		ret = cachefiles_has_space(cache, 1, 0);
  		if (ret < 0)
  			goto mkdir_error;
  
  		_debug("attempt mkdir");

  		path.mnt = cache->mnt;
  		path.dentry = dir;
  		ret = security_path_mkdir(&path, subdir, 0700);
  		if (ret < 0)
  			goto mkdir_error;

  		ret = vfs_mkdir(d_inode(dir), subdir, 0700);

  		if (ret < 0)
  			goto mkdir_error;

  		ASSERT(d_backing_inode(subdir));

  
  		_debug("mkdir -> %p{%p{ino=%lu}}",
  		       subdir,

  		       d_backing_inode(subdir),
  		       d_backing_inode(subdir)->i_ino);

  	}

  	inode_unlock(d_inode(dir));

  
  	/* we need to make sure the subdir is a directory */

  	ASSERT(d_backing_inode(subdir));

  	if (!d_can_lookup(subdir)) {

  		pr_err("%s is not a directory
  ", dirname);

  		ret = -EIO;
  		goto check_error;
  	}
  
  	ret = -EPERM;

  	if (!(d_backing_inode(subdir)->i_opflags & IOP_XATTR) ||

  	    !d_backing_inode(subdir)->i_op->lookup ||
  	    !d_backing_inode(subdir)->i_op->mkdir ||
  	    !d_backing_inode(subdir)->i_op->create ||

  	    !d_backing_inode(subdir)->i_op->rename ||

  	    !d_backing_inode(subdir)->i_op->rmdir ||
  	    !d_backing_inode(subdir)->i_op->unlink)

  		goto check_error;

  	_leave(" = [%lu]", d_backing_inode(subdir)->i_ino);

  	return subdir;
  
  check_error:
  	dput(subdir);
  	_leave(" = %d [check]", ret);
  	return ERR_PTR(ret);
  
  mkdir_error:

  	inode_unlock(d_inode(dir));

  	dput(subdir);

  	pr_err("mkdir %s failed with error %d
  ", dirname, ret);

  	return ERR_PTR(ret);
  
  lookup_error:

  	inode_unlock(d_inode(dir));

  	ret = PTR_ERR(subdir);

  	pr_err("Lookup %s failed with error %d
  ", dirname, ret);

  	return ERR_PTR(ret);
  
  nomem_d_alloc:

  	inode_unlock(d_inode(dir));

  	_leave(" = -ENOMEM");
  	return ERR_PTR(-ENOMEM);
  }
  
  /*
   * find out if an object is in use or not
   * - if finds object and it's not in use:
   *   - returns a pointer to the object and a reference on it
   *   - returns with the directory locked
   */
  static struct dentry *cachefiles_check_active(struct cachefiles_cache *cache,
  					      struct dentry *dir,
  					      char *filename)
  {
  	struct cachefiles_object *object;
  	struct rb_node *_n;
  	struct dentry *victim;
  	unsigned long start;
  	int ret;

  	//_enter(",%pd/,%s",
  	//       dir, filename);

  
  	/* look up the victim */

  	inode_lock_nested(d_inode(dir), I_MUTEX_PARENT);

  
  	start = jiffies;
  	victim = lookup_one_len(filename, dir, strlen(filename));
  	cachefiles_hist(cachefiles_lookup_histogram, start);
  	if (IS_ERR(victim))
  		goto lookup_error;
  
  	//_debug("victim -> %p %s",

  	//       victim, d_backing_inode(victim) ? "positive" : "negative");

  
  	/* if the object is no longer there then we probably retired the object
  	 * at the netfs's request whilst the cull was in progress
  	 */

  	if (d_is_negative(victim)) {

  		inode_unlock(d_inode(dir));

  		dput(victim);
  		_leave(" = -ENOENT [absent]");
  		return ERR_PTR(-ENOENT);
  	}
  
  	/* check to see if we're using this object */
  	read_lock(&cache->active_lock);
  
  	_n = cache->active_nodes.rb_node;
  
  	while (_n) {
  		object = rb_entry(_n, struct cachefiles_object, active_node);
  
  		if (object->dentry > victim)
  			_n = _n->rb_left;
  		else if (object->dentry < victim)
  			_n = _n->rb_right;
  		else
  			goto object_in_use;
  	}
  
  	read_unlock(&cache->active_lock);
  
  	//_leave(" = %p", victim);
  	return victim;
  
  object_in_use:
  	read_unlock(&cache->active_lock);

  	inode_unlock(d_inode(dir));

  	dput(victim);
  	//_leave(" = -EBUSY [in use]");
  	return ERR_PTR(-EBUSY);
  
  lookup_error:

  	inode_unlock(d_inode(dir));

  	ret = PTR_ERR(victim);
  	if (ret == -ENOENT) {
  		/* file or dir now absent - probably retired by netfs */
  		_leave(" = -ESTALE [absent]");
  		return ERR_PTR(-ESTALE);
  	}
  
  	if (ret == -EIO) {
  		cachefiles_io_error(cache, "Lookup failed");
  	} else if (ret != -ENOMEM) {

  		pr_err("Internal error: %d
  ", ret);

  		ret = -EIO;
  	}
  
  	_leave(" = %d", ret);
  	return ERR_PTR(ret);
  }
  
  /*
   * cull an object if it's not in use
   * - called only by cache manager daemon
   */
  int cachefiles_cull(struct cachefiles_cache *cache, struct dentry *dir,
  		    char *filename)
  {
  	struct dentry *victim;
  	int ret;

  	_enter(",%pd/,%s", dir, filename);

  
  	victim = cachefiles_check_active(cache, dir, filename);
  	if (IS_ERR(victim))
  		return PTR_ERR(victim);
  
  	_debug("victim -> %p %s",

  	       victim, d_backing_inode(victim) ? "positive" : "negative");

  
  	/* okay... the victim is not being used so we can cull it
  	 * - start by marking it as stale
  	 */
  	_debug("victim is cullable");
  
  	ret = cachefiles_remove_object_xattr(cache, victim);
  	if (ret < 0)
  		goto error_unlock;
  
  	/*  actually remove the victim (drops the dir mutex) */
  	_debug("bury");

  	ret = cachefiles_bury_object(cache, dir, victim, false,
  				     FSCACHE_OBJECT_WAS_CULLED);

  	if (ret < 0)
  		goto error;
  
  	dput(victim);
  	_leave(" = 0");
  	return 0;
  
  error_unlock:

  	inode_unlock(d_inode(dir));

  error:
  	dput(victim);
  	if (ret == -ENOENT) {
  		/* file or dir now absent - probably retired by netfs */
  		_leave(" = -ESTALE [absent]");
  		return -ESTALE;
  	}
  
  	if (ret != -ENOMEM) {

  		pr_err("Internal error: %d
  ", ret);

  		ret = -EIO;
  	}
  
  	_leave(" = %d", ret);
  	return ret;
  }
  
  /*
   * find out if an object is in use or not
   * - called only by cache manager daemon
   * - returns -EBUSY or 0 to indicate whether an object is in use or not
   */
  int cachefiles_check_in_use(struct cachefiles_cache *cache, struct dentry *dir,
  			    char *filename)
  {
  	struct dentry *victim;

  	//_enter(",%pd/,%s",
  	//       dir, filename);

  
  	victim = cachefiles_check_active(cache, dir, filename);
  	if (IS_ERR(victim))
  		return PTR_ERR(victim);

  	inode_unlock(d_inode(dir));

  	dput(victim);
  	//_leave(" = 0");
  	return 0;
  }