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dir.c

/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * dir.c - Operations for configfs directories.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 *
 * Based on sysfs:
 *    sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
 *
 * configfs Copyright (C) 2005 Oracle.  All rights reserved.
 */

#undef DEBUG

#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/module.h>
#include <linux/slab.h>

#include <linux/configfs.h>
#include "configfs_internal.h"

DECLARE_RWSEM(configfs_rename_sem);

static void configfs_d_iput(struct dentry * dentry,
                      struct inode * inode)
{
      struct configfs_dirent * sd = dentry->d_fsdata;

      if (sd) {
            BUG_ON(sd->s_dentry != dentry);
            sd->s_dentry = NULL;
            configfs_put(sd);
      }
      iput(inode);
}

/*
 * We _must_ delete our dentries on last dput, as the chain-to-parent
 * behavior is required to clear the parents of default_groups.
 */
static int configfs_d_delete(struct dentry *dentry)
{
      return 1;
}

static struct dentry_operations configfs_dentry_ops = {
      .d_iput           = configfs_d_iput,
      /* simple_delete_dentry() isn't exported */
      .d_delete   = configfs_d_delete,
};

/*
 * Allocates a new configfs_dirent and links it to the parent configfs_dirent
 */
static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent * parent_sd,
                                    void * element)
{
      struct configfs_dirent * sd;

      sd = kmem_cache_zalloc(configfs_dir_cachep, GFP_KERNEL);
      if (!sd)
            return NULL;

      atomic_set(&sd->s_count, 1);
      INIT_LIST_HEAD(&sd->s_links);
      INIT_LIST_HEAD(&sd->s_children);
      list_add(&sd->s_sibling, &parent_sd->s_children);
      sd->s_element = element;

      return sd;
}

/*
 *
 * Return -EEXIST if there is already a configfs element with the same
 * name for the same parent.
 *
 * called with parent inode's i_mutex held
 */
static int configfs_dirent_exists(struct configfs_dirent *parent_sd,
                          const unsigned char *new)
{
      struct configfs_dirent * sd;

      list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
            if (sd->s_element) {
                  const unsigned char *existing = configfs_get_name(sd);
                  if (strcmp(existing, new))
                        continue;
                  else
                        return -EEXIST;
            }
      }

      return 0;
}


int configfs_make_dirent(struct configfs_dirent * parent_sd,
                   struct dentry * dentry, void * element,
                   umode_t mode, int type)
{
      struct configfs_dirent * sd;

      sd = configfs_new_dirent(parent_sd, element);
      if (!sd)
            return -ENOMEM;

      sd->s_mode = mode;
      sd->s_type = type;
      sd->s_dentry = dentry;
      if (dentry) {
            dentry->d_fsdata = configfs_get(sd);
            dentry->d_op = &configfs_dentry_ops;
      }

      return 0;
}

static int init_dir(struct inode * inode)
{
      inode->i_op = &configfs_dir_inode_operations;
      inode->i_fop = &configfs_dir_operations;

      /* directory inodes start off with i_nlink == 2 (for "." entry) */
      inc_nlink(inode);
      return 0;
}

static int configfs_init_file(struct inode * inode)
{
      inode->i_size = PAGE_SIZE;
      inode->i_fop = &configfs_file_operations;
      return 0;
}

static int init_symlink(struct inode * inode)
{
      inode->i_op = &configfs_symlink_inode_operations;
      return 0;
}

static int create_dir(struct config_item * k, struct dentry * p,
                  struct dentry * d)
{
      int error;
      umode_t mode = S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO;

      error = configfs_dirent_exists(p->d_fsdata, d->d_name.name);
      if (!error)
            error = configfs_make_dirent(p->d_fsdata, d, k, mode,
                                   CONFIGFS_DIR);
      if (!error) {
            error = configfs_create(d, mode, init_dir);
            if (!error) {
                  inc_nlink(p->d_inode);
                  (d)->d_op = &configfs_dentry_ops;
            } else {
                  struct configfs_dirent *sd = d->d_fsdata;
                  if (sd) {
                        list_del_init(&sd->s_sibling);
                        configfs_put(sd);
                  }
            }
      }
      return error;
}


/**
 *    configfs_create_dir - create a directory for an config_item.
 *    @item:            config_itemwe're creating directory for.
 *    @dentry:    config_item's dentry.
 */

static int configfs_create_dir(struct config_item * item, struct dentry *dentry)
{
      struct dentry * parent;
      int error = 0;

      BUG_ON(!item);

      if (item->ci_parent)
            parent = item->ci_parent->ci_dentry;
      else if (configfs_mount && configfs_mount->mnt_sb)
            parent = configfs_mount->mnt_sb->s_root;
      else
            return -EFAULT;

      error = create_dir(item,parent,dentry);
      if (!error)
            item->ci_dentry = dentry;
      return error;
}

int configfs_create_link(struct configfs_symlink *sl,
                   struct dentry *parent,
                   struct dentry *dentry)
{
      int err = 0;
      umode_t mode = S_IFLNK | S_IRWXUGO;

      err = configfs_make_dirent(parent->d_fsdata, dentry, sl, mode,
                           CONFIGFS_ITEM_LINK);
      if (!err) {
            err = configfs_create(dentry, mode, init_symlink);
            if (!err)
                  dentry->d_op = &configfs_dentry_ops;
            else {
                  struct configfs_dirent *sd = dentry->d_fsdata;
                  if (sd) {
                        list_del_init(&sd->s_sibling);
                        configfs_put(sd);
                  }
            }
      }
      return err;
}

static void remove_dir(struct dentry * d)
{
      struct dentry * parent = dget(d->d_parent);
      struct configfs_dirent * sd;

      sd = d->d_fsdata;
      list_del_init(&sd->s_sibling);
      configfs_put(sd);
      if (d->d_inode)
            simple_rmdir(parent->d_inode,d);

      pr_debug(" o %s removing done (%d)\n",d->d_name.name,
             atomic_read(&d->d_count));

      dput(parent);
}

/**
 * configfs_remove_dir - remove an config_item's directory.
 * @item:   config_item we're removing.
 *
 * The only thing special about this is that we remove any files in
 * the directory before we remove the directory, and we've inlined
 * what used to be configfs_rmdir() below, instead of calling separately.
 */

static void configfs_remove_dir(struct config_item * item)
{
      struct dentry * dentry = dget(item->ci_dentry);

      if (!dentry)
            return;

      remove_dir(dentry);
      /**
       * Drop reference from dget() on entrance.
       */
      dput(dentry);
}


/* attaches attribute's configfs_dirent to the dentry corresponding to the
 * attribute file
 */
static int configfs_attach_attr(struct configfs_dirent * sd, struct dentry * dentry)
{
      struct configfs_attribute * attr = sd->s_element;
      int error;

      dentry->d_fsdata = configfs_get(sd);
      sd->s_dentry = dentry;
      error = configfs_create(dentry, (attr->ca_mode & S_IALLUGO) | S_IFREG,
                        configfs_init_file);
      if (error) {
            configfs_put(sd);
            return error;
      }

      dentry->d_op = &configfs_dentry_ops;
      d_rehash(dentry);

      return 0;
}

static struct dentry * configfs_lookup(struct inode *dir,
                               struct dentry *dentry,
                               struct nameidata *nd)
{
      struct configfs_dirent * parent_sd = dentry->d_parent->d_fsdata;
      struct configfs_dirent * sd;
      int found = 0;
      int err = 0;

      list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
            if (sd->s_type & CONFIGFS_NOT_PINNED) {
                  const unsigned char * name = configfs_get_name(sd);

                  if (strcmp(name, dentry->d_name.name))
                        continue;

                  found = 1;
                  err = configfs_attach_attr(sd, dentry);
                  break;
            }
      }

      if (!found) {
            /*
             * If it doesn't exist and it isn't a NOT_PINNED item,
             * it must be negative.
             */
            return simple_lookup(dir, dentry, nd);
      }

      return ERR_PTR(err);
}

/*
 * Only subdirectories count here.  Files (CONFIGFS_NOT_PINNED) are
 * attributes and are removed by rmdir().  We recurse, taking i_mutex
 * on all children that are candidates for default detach.  If the
 * result is clean, then configfs_detach_group() will handle dropping
 * i_mutex.  If there is an error, the caller will clean up the i_mutex
 * holders via configfs_detach_rollback().
 */
static int configfs_detach_prep(struct dentry *dentry)
{
      struct configfs_dirent *parent_sd = dentry->d_fsdata;
      struct configfs_dirent *sd;
      int ret;

      ret = -EBUSY;
      if (!list_empty(&parent_sd->s_links))
            goto out;

      ret = 0;
      list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
            if (sd->s_type & CONFIGFS_NOT_PINNED)
                  continue;
            if (sd->s_type & CONFIGFS_USET_DEFAULT) {
                  mutex_lock(&sd->s_dentry->d_inode->i_mutex);
                  /* Mark that we've taken i_mutex */
                  sd->s_type |= CONFIGFS_USET_DROPPING;

                  /*
                   * Yup, recursive.  If there's a problem, blame
                   * deep nesting of default_groups
                   */
                  ret = configfs_detach_prep(sd->s_dentry);
                  if (!ret)
                        continue;
            } else
                  ret = -ENOTEMPTY;

            break;
      }

out:
      return ret;
}

/*
 * Walk the tree, dropping i_mutex wherever CONFIGFS_USET_DROPPING is
 * set.
 */
static void configfs_detach_rollback(struct dentry *dentry)
{
      struct configfs_dirent *parent_sd = dentry->d_fsdata;
      struct configfs_dirent *sd;

      list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
            if (sd->s_type & CONFIGFS_USET_DEFAULT) {
                  configfs_detach_rollback(sd->s_dentry);

                  if (sd->s_type & CONFIGFS_USET_DROPPING) {
                        sd->s_type &= ~CONFIGFS_USET_DROPPING;
                        mutex_unlock(&sd->s_dentry->d_inode->i_mutex);
                  }
            }
      }
}

static void detach_attrs(struct config_item * item)
{
      struct dentry * dentry = dget(item->ci_dentry);
      struct configfs_dirent * parent_sd;
      struct configfs_dirent * sd, * tmp;

      if (!dentry)
            return;

      pr_debug("configfs %s: dropping attrs for  dir\n",
             dentry->d_name.name);

      parent_sd = dentry->d_fsdata;
      list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) {
            if (!sd->s_element || !(sd->s_type & CONFIGFS_NOT_PINNED))
                  continue;
            list_del_init(&sd->s_sibling);
            configfs_drop_dentry(sd, dentry);
            configfs_put(sd);
      }

      /**
       * Drop reference from dget() on entrance.
       */
      dput(dentry);
}

static int populate_attrs(struct config_item *item)
{
      struct config_item_type *t = item->ci_type;
      struct configfs_attribute *attr;
      int error = 0;
      int i;

      if (!t)
            return -EINVAL;
      if (t->ct_attrs) {
            for (i = 0; (attr = t->ct_attrs[i]) != NULL; i++) {
                  if ((error = configfs_create_file(item, attr)))
                        break;
            }
      }

      if (error)
            detach_attrs(item);

      return error;
}

static int configfs_attach_group(struct config_item *parent_item,
                         struct config_item *item,
                         struct dentry *dentry);
static void configfs_detach_group(struct config_item *item);

static void detach_groups(struct config_group *group)
{
      struct dentry * dentry = dget(group->cg_item.ci_dentry);
      struct dentry *child;
      struct configfs_dirent *parent_sd;
      struct configfs_dirent *sd, *tmp;

      if (!dentry)
            return;

      parent_sd = dentry->d_fsdata;
      list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) {
            if (!sd->s_element ||
                !(sd->s_type & CONFIGFS_USET_DEFAULT))
                  continue;

            child = sd->s_dentry;

            configfs_detach_group(sd->s_element);
            child->d_inode->i_flags |= S_DEAD;

            /*
             * From rmdir/unregister, a configfs_detach_prep() pass
             * has taken our i_mutex for us.  Drop it.
             * From mkdir/register cleanup, there is no sem held.
             */
            if (sd->s_type & CONFIGFS_USET_DROPPING)
                  mutex_unlock(&child->d_inode->i_mutex);

            d_delete(child);
            dput(child);
      }

      /**
       * Drop reference from dget() on entrance.
       */
      dput(dentry);
}

/*
 * This fakes mkdir(2) on a default_groups[] entry.  It
 * creates a dentry, attachs it, and then does fixup
 * on the sd->s_type.
 *
 * We could, perhaps, tweak our parent's ->mkdir for a minute and
 * try using vfs_mkdir.  Just a thought.
 */
static int create_default_group(struct config_group *parent_group,
                        struct config_group *group)
{
      int ret;
      struct qstr name;
      struct configfs_dirent *sd;
      /* We trust the caller holds a reference to parent */
      struct dentry *child, *parent = parent_group->cg_item.ci_dentry;

      if (!group->cg_item.ci_name)
            group->cg_item.ci_name = group->cg_item.ci_namebuf;
      name.name = group->cg_item.ci_name;
      name.len = strlen(name.name);
      name.hash = full_name_hash(name.name, name.len);

      ret = -ENOMEM;
      child = d_alloc(parent, &name);
      if (child) {
            d_add(child, NULL);

            ret = configfs_attach_group(&parent_group->cg_item,
                                  &group->cg_item, child);
            if (!ret) {
                  sd = child->d_fsdata;
                  sd->s_type |= CONFIGFS_USET_DEFAULT;
            } else {
                  d_delete(child);
                  dput(child);
            }
      }

      return ret;
}

static int populate_groups(struct config_group *group)
{
      struct config_group *new_group;
      struct dentry *dentry = group->cg_item.ci_dentry;
      int ret = 0;
      int i;

      if (group->default_groups) {
            /*
             * FYI, we're faking mkdir here
             * I'm not sure we need this semaphore, as we're called
             * from our parent's mkdir.  That holds our parent's
             * i_mutex, so afaik lookup cannot continue through our
             * parent to find us, let alone mess with our tree.
             * That said, taking our i_mutex is closer to mkdir
             * emulation, and shouldn't hurt.
             */
            mutex_lock(&dentry->d_inode->i_mutex);

            for (i = 0; group->default_groups[i]; i++) {
                  new_group = group->default_groups[i];

                  ret = create_default_group(group, new_group);
                  if (ret)
                        break;
            }

            mutex_unlock(&dentry->d_inode->i_mutex);
      }

      if (ret)
            detach_groups(group);

      return ret;
}

/*
 * All of link_obj/unlink_obj/link_group/unlink_group require that
 * subsys->su_mutex is held.
 */

static void unlink_obj(struct config_item *item)
{
      struct config_group *group;

      group = item->ci_group;
      if (group) {
            list_del_init(&item->ci_entry);

            item->ci_group = NULL;
            item->ci_parent = NULL;

            /* Drop the reference for ci_entry */
            config_item_put(item);

            /* Drop the reference for ci_parent */
            config_group_put(group);
      }
}

static void link_obj(struct config_item *parent_item, struct config_item *item)
{
      /*
       * Parent seems redundant with group, but it makes certain
       * traversals much nicer.
       */
      item->ci_parent = parent_item;

      /*
       * We hold a reference on the parent for the child's ci_parent
       * link.
       */
      item->ci_group = config_group_get(to_config_group(parent_item));
      list_add_tail(&item->ci_entry, &item->ci_group->cg_children);

      /*
       * We hold a reference on the child for ci_entry on the parent's
       * cg_children
       */
      config_item_get(item);
}

static void unlink_group(struct config_group *group)
{
      int i;
      struct config_group *new_group;

      if (group->default_groups) {
            for (i = 0; group->default_groups[i]; i++) {
                  new_group = group->default_groups[i];
                  unlink_group(new_group);
            }
      }

      group->cg_subsys = NULL;
      unlink_obj(&group->cg_item);
}

static void link_group(struct config_group *parent_group, struct config_group *group)
{
      int i;
      struct config_group *new_group;
      struct configfs_subsystem *subsys = NULL; /* gcc is a turd */

      link_obj(&parent_group->cg_item, &group->cg_item);

      if (parent_group->cg_subsys)
            subsys = parent_group->cg_subsys;
      else if (configfs_is_root(&parent_group->cg_item))
            subsys = to_configfs_subsystem(group);
      else
            BUG();
      group->cg_subsys = subsys;

      if (group->default_groups) {
            for (i = 0; group->default_groups[i]; i++) {
                  new_group = group->default_groups[i];
                  link_group(group, new_group);
            }
      }
}

/*
 * The goal is that configfs_attach_item() (and
 * configfs_attach_group()) can be called from either the VFS or this
 * module.  That is, they assume that the items have been created,
 * the dentry allocated, and the dcache is all ready to go.
 *
 * If they fail, they must clean up after themselves as if they
 * had never been called.  The caller (VFS or local function) will
 * handle cleaning up the dcache bits.
 *
 * configfs_detach_group() and configfs_detach_item() behave similarly on
 * the way out.  They assume that the proper semaphores are held, they
 * clean up the configfs items, and they expect their callers will
 * handle the dcache bits.
 */
static int configfs_attach_item(struct config_item *parent_item,
                        struct config_item *item,
                        struct dentry *dentry)
{
      int ret;

      ret = configfs_create_dir(item, dentry);
      if (!ret) {
            ret = populate_attrs(item);
            if (ret) {
                  configfs_remove_dir(item);
                  d_delete(dentry);
            }
      }

      return ret;
}

static void configfs_detach_item(struct config_item *item)
{
      detach_attrs(item);
      configfs_remove_dir(item);
}

static int configfs_attach_group(struct config_item *parent_item,
                         struct config_item *item,
                         struct dentry *dentry)
{
      int ret;
      struct configfs_dirent *sd;

      ret = configfs_attach_item(parent_item, item, dentry);
      if (!ret) {
            sd = dentry->d_fsdata;
            sd->s_type |= CONFIGFS_USET_DIR;

            ret = populate_groups(to_config_group(item));
            if (ret) {
                  configfs_detach_item(item);
                  d_delete(dentry);
            }
      }

      return ret;
}

static void configfs_detach_group(struct config_item *item)
{
      detach_groups(to_config_group(item));
      configfs_detach_item(item);
}

/*
 * After the item has been detached from the filesystem view, we are
 * ready to tear it out of the hierarchy.  Notify the client before
 * we do that so they can perform any cleanup that requires
 * navigating the hierarchy.  A client does not need to provide this
 * callback.  The subsystem semaphore MUST be held by the caller, and
 * references must be valid for both items.  It also assumes the
 * caller has validated ci_type.
 */
static void client_disconnect_notify(struct config_item *parent_item,
                             struct config_item *item)
{
      struct config_item_type *type;

      type = parent_item->ci_type;
      BUG_ON(!type);

      if (type->ct_group_ops && type->ct_group_ops->disconnect_notify)
            type->ct_group_ops->disconnect_notify(to_config_group(parent_item),
                                          item);
}

/*
 * Drop the initial reference from make_item()/make_group()
 * This function assumes that reference is held on item
 * and that item holds a valid reference to the parent.  Also, it
 * assumes the caller has validated ci_type.
 */
static void client_drop_item(struct config_item *parent_item,
                       struct config_item *item)
{
      struct config_item_type *type;

      type = parent_item->ci_type;
      BUG_ON(!type);

      /*
       * If ->drop_item() exists, it is responsible for the
       * config_item_put().
       */
      if (type->ct_group_ops && type->ct_group_ops->drop_item)
            type->ct_group_ops->drop_item(to_config_group(parent_item),
                                    item);
      else
            config_item_put(item);
}

#ifdef DEBUG
static void configfs_dump_one(struct configfs_dirent *sd, int level)
{
      printk(KERN_INFO "%*s\"%s\":\n", level, " ", configfs_get_name(sd));

#define type_print(_type) if (sd->s_type & _type) printk(KERN_INFO "%*s %s\n", level, " ", #_type);
      type_print(CONFIGFS_ROOT);
      type_print(CONFIGFS_DIR);
      type_print(CONFIGFS_ITEM_ATTR);
      type_print(CONFIGFS_ITEM_LINK);
      type_print(CONFIGFS_USET_DIR);
      type_print(CONFIGFS_USET_DEFAULT);
      type_print(CONFIGFS_USET_DROPPING);
#undef type_print
}

static int configfs_dump(struct configfs_dirent *sd, int level)
{
      struct configfs_dirent *child_sd;
      int ret = 0;

      configfs_dump_one(sd, level);

      if (!(sd->s_type & (CONFIGFS_DIR|CONFIGFS_ROOT)))
            return 0;

      list_for_each_entry(child_sd, &sd->s_children, s_sibling) {
            ret = configfs_dump(child_sd, level + 2);
            if (ret)
                  break;
      }

      return ret;
}
#endif


/*
 * configfs_depend_item() and configfs_undepend_item()
 *
 * WARNING: Do not call these from a configfs callback!
 *
 * This describes these functions and their helpers.
 *
 * Allow another kernel system to depend on a config_item.  If this
 * happens, the item cannot go away until the dependant can live without
 * it.  The idea is to give client modules as simple an interface as
 * possible.  When a system asks them to depend on an item, they just
 * call configfs_depend_item().  If the item is live and the client
 * driver is in good shape, we'll happily do the work for them.
 *
 * Why is the locking complex?  Because configfs uses the VFS to handle
 * all locking, but this function is called outside the normal
 * VFS->configfs path.  So it must take VFS locks to prevent the
 * VFS->configfs stuff (configfs_mkdir(), configfs_rmdir(), etc).  This is
 * why you can't call these functions underneath configfs callbacks.
 *
 * Note, btw, that this can be called at *any* time, even when a configfs
 * subsystem isn't registered, or when configfs is loading or unloading.
 * Just like configfs_register_subsystem().  So we take the same
 * precautions.  We pin the filesystem.  We lock each i_mutex _in_order_
 * on our way down the tree.  If we can find the target item in the
 * configfs tree, it must be part of the subsystem tree as well, so we
 * do not need the subsystem semaphore.  Holding the i_mutex chain locks
 * out mkdir() and rmdir(), who might be racing us.
 */

/*
 * configfs_depend_prep()
 *
 * Only subdirectories count here.  Files (CONFIGFS_NOT_PINNED) are
 * attributes.  This is similar but not the same to configfs_detach_prep().
 * Note that configfs_detach_prep() expects the parent to be locked when it
 * is called, but we lock the parent *inside* configfs_depend_prep().  We
 * do that so we can unlock it if we find nothing.
 *
 * Here we do a depth-first search of the dentry hierarchy looking for
 * our object.  We take i_mutex on each step of the way down.  IT IS
 * ESSENTIAL THAT i_mutex LOCKING IS ORDERED.  If we come back up a branch,
 * we'll drop the i_mutex.
 *
 * If the target is not found, -ENOENT is bubbled up and we have released
 * all locks.  If the target was found, the locks will be cleared by
 * configfs_depend_rollback().
 *
 * This adds a requirement that all config_items be unique!
 *
 * This is recursive because the locking traversal is tricky.  There isn't
 * much on the stack, though, so folks that need this function - be careful
 * about your stack!  Patches will be accepted to make it iterative.
 */
static int configfs_depend_prep(struct dentry *origin,
                        struct config_item *target)
{
      struct configfs_dirent *child_sd, *sd = origin->d_fsdata;
      int ret = 0;

      BUG_ON(!origin || !sd);

      /* Lock this guy on the way down */
      mutex_lock(&sd->s_dentry->d_inode->i_mutex);
      if (sd->s_element == target)  /* Boo-yah */
            goto out;

      list_for_each_entry(child_sd, &sd->s_children, s_sibling) {
            if (child_sd->s_type & CONFIGFS_DIR) {
                  ret = configfs_depend_prep(child_sd->s_dentry,
                                       target);
                  if (!ret)
                        goto out;  /* Child path boo-yah */
            }
      }

      /* We looped all our children and didn't find target */
      mutex_unlock(&sd->s_dentry->d_inode->i_mutex);
      ret = -ENOENT;

out:
      return ret;
}

/*
 * This is ONLY called if configfs_depend_prep() did its job.  So we can
 * trust the entire path from item back up to origin.
 *
 * We walk backwards from item, unlocking each i_mutex.  We finish by
 * unlocking origin.
 */
static void configfs_depend_rollback(struct dentry *origin,
                             struct config_item *item)
{
      struct dentry *dentry = item->ci_dentry;

      while (dentry != origin) {
            mutex_unlock(&dentry->d_inode->i_mutex);
            dentry = dentry->d_parent;
      }

      mutex_unlock(&origin->d_inode->i_mutex);
}

int configfs_depend_item(struct configfs_subsystem *subsys,
                   struct config_item *target)
{
      int ret;
      struct configfs_dirent *p, *root_sd, *subsys_sd = NULL;
      struct config_item *s_item = &subsys->su_group.cg_item;

      /*
       * Pin the configfs filesystem.  This means we can safely access
       * the root of the configfs filesystem.
       */
      ret = configfs_pin_fs();
      if (ret)
            return ret;

      /*
       * Next, lock the root directory.  We're going to check that the
       * subsystem is really registered, and so we need to lock out
       * configfs_[un]register_subsystem().
       */
      mutex_lock(&configfs_sb->s_root->d_inode->i_mutex);

      root_sd = configfs_sb->s_root->d_fsdata;

      list_for_each_entry(p, &root_sd->s_children, s_sibling) {
            if (p->s_type & CONFIGFS_DIR) {
                  if (p->s_element == s_item) {
                        subsys_sd = p;
                        break;
                  }
            }
      }

      if (!subsys_sd) {
            ret = -ENOENT;
            goto out_unlock_fs;
      }

      /* Ok, now we can trust subsys/s_item */

      /* Scan the tree, locking i_mutex recursively, return 0 if found */
      ret = configfs_depend_prep(subsys_sd->s_dentry, target);
      if (ret)
            goto out_unlock_fs;

      /* We hold all i_mutexes from the subsystem down to the target */
      p = target->ci_dentry->d_fsdata;
      p->s_dependent_count += 1;

      configfs_depend_rollback(subsys_sd->s_dentry, target);

out_unlock_fs:
      mutex_unlock(&configfs_sb->s_root->d_inode->i_mutex);

      /*
       * If we succeeded, the fs is pinned via other methods.  If not,
       * we're done with it anyway.  So release_fs() is always right.
       */
      configfs_release_fs();

      return ret;
}
EXPORT_SYMBOL(configfs_depend_item);

/*
 * Release the dependent linkage.  This is much simpler than
 * configfs_depend_item() because we know that that the client driver is
 * pinned, thus the subsystem is pinned, and therefore configfs is pinned.
 */
void configfs_undepend_item(struct configfs_subsystem *subsys,
                      struct config_item *target)
{
      struct configfs_dirent *sd;

      /*
       * Since we can trust everything is pinned, we just need i_mutex
       * on the item.
       */
      mutex_lock(&target->ci_dentry->d_inode->i_mutex);

      sd = target->ci_dentry->d_fsdata;
      BUG_ON(sd->s_dependent_count < 1);

      sd->s_dependent_count -= 1;

      /*
       * After this unlock, we cannot trust the item to stay alive!
       * DO NOT REFERENCE item after this unlock.
       */
      mutex_unlock(&target->ci_dentry->d_inode->i_mutex);
}
EXPORT_SYMBOL(configfs_undepend_item);

static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
      int ret, module_got = 0;
      struct config_group *group;
      struct config_item *item;
      struct config_item *parent_item;
      struct configfs_subsystem *subsys;
      struct configfs_dirent *sd;
      struct config_item_type *type;
      struct module *owner = NULL;
      char *name;

      if (dentry->d_parent == configfs_sb->s_root) {
            ret = -EPERM;
            goto out;
      }

      sd = dentry->d_parent->d_fsdata;
      if (!(sd->s_type & CONFIGFS_USET_DIR)) {
            ret = -EPERM;
            goto out;
      }

      /* Get a working ref for the duration of this function */
      parent_item = configfs_get_config_item(dentry->d_parent);
      type = parent_item->ci_type;
      subsys = to_config_group(parent_item)->cg_subsys;
      BUG_ON(!subsys);

      if (!type || !type->ct_group_ops ||
          (!type->ct_group_ops->make_group &&
           !type->ct_group_ops->make_item)) {
            ret = -EPERM;  /* Lack-of-mkdir returns -EPERM */
            goto out_put;
      }

      name = kmalloc(dentry->d_name.len + 1, GFP_KERNEL);
      if (!name) {
            ret = -ENOMEM;
            goto out_put;
      }

      snprintf(name, dentry->d_name.len + 1, "%s", dentry->d_name.name);

      mutex_lock(&subsys->su_mutex);
      group = NULL;
      item = NULL;
      if (type->ct_group_ops->make_group) {
            group = type->ct_group_ops->make_group(to_config_group(parent_item), name);
            if (group) {
                  link_group(to_config_group(parent_item), group);
                  item = &group->cg_item;
            }
      } else {
            item = type->ct_group_ops->make_item(to_config_group(parent_item), name);
            if (item)
                  link_obj(parent_item, item);
      }
      mutex_unlock(&subsys->su_mutex);

      kfree(name);
      if (!item) {
            /*
             * If item == NULL, then link_obj() was never called.
             * There are no extra references to clean up.
             */
            ret = -ENOMEM;
            goto out_put;
      }

      /*
       * link_obj() has been called (via link_group() for groups).
       * From here on out, errors must clean that up.
       */

      type = item->ci_type;
      if (!type) {
            ret = -EINVAL;
            goto out_unlink;
      }

      owner = type->ct_owner;
      if (!try_module_get(owner)) {
            ret = -EINVAL;
            goto out_unlink;
      }

      /*
       * I hate doing it this way, but if there is
       * an error,  module_put() probably should
       * happen after any cleanup.
       */
      module_got = 1;

      if (group)
            ret = configfs_attach_group(parent_item, item, dentry);
      else
            ret = configfs_attach_item(parent_item, item, dentry);

out_unlink:
      if (ret) {
            /* Tear down everything we built up */
            mutex_lock(&subsys->su_mutex);

            client_disconnect_notify(parent_item, item);
            if (group)
                  unlink_group(group);
            else
                  unlink_obj(item);
            client_drop_item(parent_item, item);

            mutex_unlock(&subsys->su_mutex);

            if (module_got)
                  module_put(owner);
      }

out_put:
      /*
       * link_obj()/link_group() took a reference from child->parent,
       * so the parent is safely pinned.  We can drop our working
       * reference.
       */
      config_item_put(parent_item);

out:
      return ret;
}

static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
{
      struct config_item *parent_item;
      struct config_item *item;
      struct configfs_subsystem *subsys;
      struct configfs_dirent *sd;
      struct module *owner = NULL;
      int ret;

      if (dentry->d_parent == configfs_sb->s_root)
            return -EPERM;

      sd = dentry->d_fsdata;
      if (sd->s_type & CONFIGFS_USET_DEFAULT)
            return -EPERM;

      /*
       * Here's where we check for dependents.  We're protected by
       * i_mutex.
       */
      if (sd->s_dependent_count)
            return -EBUSY;

      /* Get a working ref until we have the child */
      parent_item = configfs_get_config_item(dentry->d_parent);
      subsys = to_config_group(parent_item)->cg_subsys;
      BUG_ON(!subsys);

      if (!parent_item->ci_type) {
            config_item_put(parent_item);
            return -EINVAL;
      }

      ret = configfs_detach_prep(dentry);
      if (ret) {
            configfs_detach_rollback(dentry);
            config_item_put(parent_item);
            return ret;
      }

      /* Get a working ref for the duration of this function */
      item = configfs_get_config_item(dentry);

      /* Drop reference from above, item already holds one. */
      config_item_put(parent_item);

      if (item->ci_type)
            owner = item->ci_type->ct_owner;

      if (sd->s_type & CONFIGFS_USET_DIR) {
            configfs_detach_group(item);

            mutex_lock(&subsys->su_mutex);
            client_disconnect_notify(parent_item, item);
            unlink_group(to_config_group(item));
      } else {
            configfs_detach_item(item);

            mutex_lock(&subsys->su_mutex);
            client_disconnect_notify(parent_item, item);
            unlink_obj(item);
      }

      client_drop_item(parent_item, item);
      mutex_unlock(&subsys->su_mutex);

      /* Drop our reference from above */
      config_item_put(item);

      module_put(owner);

      return 0;
}

const struct inode_operations configfs_dir_inode_operations = {
      .mkdir            = configfs_mkdir,
      .rmdir            = configfs_rmdir,
      .symlink    = configfs_symlink,
      .unlink           = configfs_unlink,
      .lookup           = configfs_lookup,
      .setattr    = configfs_setattr,
};

#if 0
int configfs_rename_dir(struct config_item * item, const char *new_name)
{
      int error = 0;
      struct dentry * new_dentry, * parent;

      if (!strcmp(config_item_name(item), new_name))
            return -EINVAL;

      if (!item->parent)
            return -EINVAL;

      down_write(&configfs_rename_sem);
      parent = item->parent->dentry;

      mutex_lock(&parent->d_inode->i_mutex);

      new_dentry = lookup_one_len(new_name, parent, strlen(new_name));
      if (!IS_ERR(new_dentry)) {
            if (!new_dentry->d_inode) {
                  error = config_item_set_name(item, "%s", new_name);
                  if (!error) {
                        d_add(new_dentry, NULL);
                        d_move(item->dentry, new_dentry);
                  }
                  else
                        d_delete(new_dentry);
            } else
                  error = -EEXIST;
            dput(new_dentry);
      }
      mutex_unlock(&parent->d_inode->i_mutex);
      up_write(&configfs_rename_sem);

      return error;
}
#endif

static int configfs_dir_open(struct inode *inode, struct file *file)
{
      struct dentry * dentry = file->f_path.dentry;
      struct configfs_dirent * parent_sd = dentry->d_fsdata;

      mutex_lock(&dentry->d_inode->i_mutex);
      file->private_data = configfs_new_dirent(parent_sd, NULL);
      mutex_unlock(&dentry->d_inode->i_mutex);

      return file->private_data ? 0 : -ENOMEM;

}

static int configfs_dir_close(struct inode *inode, struct file *file)
{
      struct dentry * dentry = file->f_path.dentry;
      struct configfs_dirent * cursor = file->private_data;

      mutex_lock(&dentry->d_inode->i_mutex);
      list_del_init(&cursor->s_sibling);
      mutex_unlock(&dentry->d_inode->i_mutex);

      release_configfs_dirent(cursor);

      return 0;
}

/* Relationship between s_mode and the DT_xxx types */
static inline unsigned char dt_type(struct configfs_dirent *sd)
{
      return (sd->s_mode >> 12) & 15;
}

static int configfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
{
      struct dentry *dentry = filp->f_path.dentry;
      struct configfs_dirent * parent_sd = dentry->d_fsdata;
      struct configfs_dirent *cursor = filp->private_data;
      struct list_head *p, *q = &cursor->s_sibling;
      ino_t ino;
      int i = filp->f_pos;

      switch (i) {
            case 0:
                  ino = dentry->d_inode->i_ino;
                  if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
                        break;
                  filp->f_pos++;
                  i++;
                  /* fallthrough */
            case 1:
                  ino = parent_ino(dentry);
                  if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
                        break;
                  filp->f_pos++;
                  i++;
                  /* fallthrough */
            default:
                  if (filp->f_pos == 2) {
                        list_move(q, &parent_sd->s_children);
                  }
                  for (p=q->next; p!= &parent_sd->s_children; p=p->next) {
                        struct configfs_dirent *next;
                        const char * name;
                        int len;

                        next = list_entry(p, struct configfs_dirent,
                                       s_sibling);
                        if (!next->s_element)
                              continue;

                        name = configfs_get_name(next);
                        len = strlen(name);
                        if (next->s_dentry)
                              ino = next->s_dentry->d_inode->i_ino;
                        else
                              ino = iunique(configfs_sb, 2);

                        if (filldir(dirent, name, len, filp->f_pos, ino,
                                     dt_type(next)) < 0)
                              return 0;

                        list_move(q, p);
                        p = q;
                        filp->f_pos++;
                  }
      }
      return 0;
}

static loff_t configfs_dir_lseek(struct file * file, loff_t offset, int origin)
{
      struct dentry * dentry = file->f_path.dentry;

      mutex_lock(&dentry->d_inode->i_mutex);
      switch (origin) {
            case 1:
                  offset += file->f_pos;
            case 0:
                  if (offset >= 0)
                        break;
            default:
                  mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
                  return -EINVAL;
      }
      if (offset != file->f_pos) {
            file->f_pos = offset;
            if (file->f_pos >= 2) {
                  struct configfs_dirent *sd = dentry->d_fsdata;
                  struct configfs_dirent *cursor = file->private_data;
                  struct list_head *p;
                  loff_t n = file->f_pos - 2;

                  list_del(&cursor->s_sibling);
                  p = sd->s_children.next;
                  while (n && p != &sd->s_children) {
                        struct configfs_dirent *next;
                        next = list_entry(p, struct configfs_dirent,
                                       s_sibling);
                        if (next->s_element)
                              n--;
                        p = p->next;
                  }
                  list_add_tail(&cursor->s_sibling, p);
            }
      }
      mutex_unlock(&dentry->d_inode->i_mutex);
      return offset;
}

const struct file_operations configfs_dir_operations = {
      .open       = configfs_dir_open,
      .release    = configfs_dir_close,
      .llseek           = configfs_dir_lseek,
      .read       = generic_read_dir,
      .readdir    = configfs_readdir,
};

int configfs_register_subsystem(struct configfs_subsystem *subsys)
{
      int err;
      struct config_group *group = &subsys->su_group;
      struct qstr name;
      struct dentry *dentry;
      struct configfs_dirent *sd;

      err = configfs_pin_fs();
      if (err)
            return err;

      if (!group->cg_item.ci_name)
            group->cg_item.ci_name = group->cg_item.ci_namebuf;

      sd = configfs_sb->s_root->d_fsdata;
      link_group(to_config_group(sd->s_element), group);

      mutex_lock(&configfs_sb->s_root->d_inode->i_mutex);

      name.name = group->cg_item.ci_name;
      name.len = strlen(name.name);
      name.hash = full_name_hash(name.name, name.len);

      err = -ENOMEM;
      dentry = d_alloc(configfs_sb->s_root, &name);
      if (dentry) {
            d_add(dentry, NULL);

            err = configfs_attach_group(sd->s_element, &group->cg_item,
                                  dentry);
            if (err) {
                  d_delete(dentry);
                  dput(dentry);
            }
      }

      mutex_unlock(&configfs_sb->s_root->d_inode->i_mutex);

      if (err) {
            unlink_group(group);
            configfs_release_fs();
      }

      return err;
}

void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
{
      struct config_group *group = &subsys->su_group;
      struct dentry *dentry = group->cg_item.ci_dentry;

      if (dentry->d_parent != configfs_sb->s_root) {
            printk(KERN_ERR "configfs: Tried to unregister non-subsystem!\n");
            return;
      }

      mutex_lock_nested(&configfs_sb->s_root->d_inode->i_mutex,
                    I_MUTEX_PARENT);
      mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
      if (configfs_detach_prep(dentry)) {
            printk(KERN_ERR "configfs: Tried to unregister non-empty subsystem!\n");
      }
      configfs_detach_group(&group->cg_item);
      dentry->d_inode->i_flags |= S_DEAD;
      mutex_unlock(&dentry->d_inode->i_mutex);

      d_delete(dentry);

      mutex_unlock(&configfs_sb->s_root->d_inode->i_mutex);

      dput(dentry);

      unlink_group(group);
      configfs_release_fs();
}

EXPORT_SYMBOL(configfs_register_subsystem);
EXPORT_SYMBOL(configfs_unregister_subsystem);

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