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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * dir.c - Operations for configfs directories.
  *
  * 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/fsnotify.h>
 #include <linux/mount.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/err.h>
 
 #include <linux/configfs.h>
 #include "configfs_internal.h"
 
 /*
  * Protects mutations of configfs_dirent linkage together with proper i_mutex
  * Also protects mutations of symlinks linkage to target configfs_dirent
  * Mutators of configfs_dirent linkage must *both* have the proper inode locked
  * and configfs_dirent_lock locked, in that order.
  * This allows one to safely traverse configfs_dirent trees and symlinks without
  * having to lock inodes.
  *
  * Protects setting of CONFIGFS_USET_DROPPING: checking the flag
  * unlocked is not reliable unless in detach_groups() called from
  * rmdir()/unregister() and from configfs_attach_group()
  */
 DEFINE_SPINLOCK(configfs_dirent_lock);
 
 /*
  * All of link_obj/unlink_obj/link_group/unlink_group require that
  * subsys->su_mutex is held.
  * But parent configfs_subsystem is NULL when config_item is root.
  * Use this mutex when config_item is root.
  */
 static DEFINE_MUTEX(configfs_subsystem_mutex);
 
 static void configfs_d_iput(struct dentry * dentry,
                 struct inode * inode)
 {
     struct configfs_dirent *sd = dentry->d_fsdata;
 
     if (sd) {
         /* Coordinate with configfs_readdir */
         spin_lock(&configfs_dirent_lock);
         /*
          * Set sd->s_dentry to null only when this dentry is the one
          * that is going to be killed.  Otherwise configfs_d_iput may
          * run just after configfs_lookup and set sd->s_dentry to
          * NULL even it's still in use.
          */
         if (sd->s_dentry == dentry)
             sd->s_dentry = NULL;
 
         spin_unlock(&configfs_dirent_lock);
         configfs_put(sd);
     }
     iput(inode);
 }
 
 const struct dentry_operations configfs_dentry_ops = {
     .d_iput     = configfs_d_iput,
     .d_delete   = always_delete_dentry,
 };
 
 #ifdef CONFIG_LOCKDEP
 
 /*
  * Helpers to make lockdep happy with our recursive locking of default groups'
  * inodes (see configfs_attach_group() and configfs_detach_group()).
  * We put default groups i_mutexes in separate classes according to their depth
  * from the youngest non-default group ancestor.
  *
  * For a non-default group A having default groups A/B, A/C, and A/C/D, default
  * groups A/B and A/C will have their inode's mutex in class
  * default_group_class[0], and default group A/C/D will be in
  * default_group_class[1].
  *
  * The lock classes are declared and assigned in inode.c, according to the
  * s_depth value.
  * The s_depth value is initialized to -1, adjusted to >= 0 when attaching
  * default groups, and reset to -1 when all default groups are attached. During
  * attachment, if configfs_create() sees s_depth > 0, the lock class of the new
  * inode's mutex is set to default_group_class[s_depth - 1].
  */
 
 static void configfs_init_dirent_depth(struct configfs_dirent *sd)
 {
     sd->s_depth = -1;
 }
 
 static void configfs_set_dir_dirent_depth(struct configfs_dirent *parent_sd,
                       struct configfs_dirent *sd)
 {
     int parent_depth = parent_sd->s_depth;
 
     if (parent_depth >= 0)
         sd->s_depth = parent_depth + 1;
 }
 
 static void
 configfs_adjust_dir_dirent_depth_before_populate(struct configfs_dirent *sd)
 {
     /*
      * item's i_mutex class is already setup, so s_depth is now only
      * used to set new sub-directories s_depth, which is always done
      * with item's i_mutex locked.
      */
     /*
      *  sd->s_depth == -1 iff we are a non default group.
      *  else (we are a default group) sd->s_depth > 0 (see
      *  create_dir()).
      */
     if (sd->s_depth == -1)
         /*
          * We are a non default group and we are going to create
          * default groups.
          */
         sd->s_depth = 0;
 }
 
 static void
 configfs_adjust_dir_dirent_depth_after_populate(struct configfs_dirent *sd)
 {
     /* We will not create default groups anymore. */
     sd->s_depth = -1;
 }
 
 #else /* CONFIG_LOCKDEP */
 
 static void configfs_init_dirent_depth(struct configfs_dirent *sd)
 {
 }
 
 static void configfs_set_dir_dirent_depth(struct configfs_dirent *parent_sd,
                       struct configfs_dirent *sd)
 {
 }
 
 static void
 configfs_adjust_dir_dirent_depth_before_populate(struct configfs_dirent *sd)
 {
 }
 
 static void
 configfs_adjust_dir_dirent_depth_after_populate(struct configfs_dirent *sd)
 {
 }
 
 #endif /* CONFIG_LOCKDEP */
 
 static struct configfs_fragment *new_fragment(void)
 {
     struct configfs_fragment *p;
 
     p = kmalloc(sizeof(struct configfs_fragment), GFP_KERNEL);
     if (p) {
         atomic_set(&p->frag_count, 1);
         init_rwsem(&p->frag_sem);
         p->frag_dead = false;
     }
     return p;
 }
 
 void put_fragment(struct configfs_fragment *frag)
 {
     if (frag && atomic_dec_and_test(&frag->frag_count))
         kfree(frag);
 }
 
 struct configfs_fragment *get_fragment(struct configfs_fragment *frag)
 {
     if (likely(frag))
         atomic_inc(&frag->frag_count);
     return frag;
 }
 
 /*
  * 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, int type,
                            struct configfs_fragment *frag)
 {
     struct configfs_dirent * sd;
 
     sd = kmem_cache_zalloc(configfs_dir_cachep, GFP_KERNEL);
     if (!sd)
         return ERR_PTR(-ENOMEM);
 
     atomic_set(&sd->s_count, 1);
     INIT_LIST_HEAD(&sd->s_children);
     sd->s_element = element;
     sd->s_type = type;
     configfs_init_dirent_depth(sd);
     spin_lock(&configfs_dirent_lock);
     if (parent_sd->s_type & CONFIGFS_USET_DROPPING) {
         spin_unlock(&configfs_dirent_lock);
         kmem_cache_free(configfs_dir_cachep, sd);
         return ERR_PTR(-ENOENT);
     }
     sd->s_frag = get_fragment(frag);
     list_add(&sd->s_sibling, &parent_sd->s_children);
     spin_unlock(&configfs_dirent_lock);
 
     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_fragment *frag)
 {
     struct configfs_dirent * sd;
 
     sd = configfs_new_dirent(parent_sd, element, type, frag);
     if (IS_ERR(sd))
         return PTR_ERR(sd);
 
     sd->s_mode = mode;
     sd->s_dentry = dentry;
     if (dentry)
         dentry->d_fsdata = configfs_get(sd);
 
     return 0;
 }
 
 static void configfs_remove_dirent(struct dentry *dentry)
 {
     struct configfs_dirent *sd = dentry->d_fsdata;
 
     if (!sd)
         return;
     spin_lock(&configfs_dirent_lock);
     list_del_init(&sd->s_sibling);
     spin_unlock(&configfs_dirent_lock);
     configfs_put(sd);
 }
 
 /**
  *  configfs_create_dir - create a directory for an config_item.
  *  @item:      config_itemwe're creating directory for.
  *  @dentry:    config_item's dentry.
  *  @frag:      config_item's fragment.
  *
  *  Note: user-created entries won't be allowed under this new directory
  *  until it is validated by configfs_dir_set_ready()
  */
 
 static int configfs_create_dir(struct config_item *item, struct dentry *dentry,
                 struct configfs_fragment *frag)
 {
     int error;
     umode_t mode = S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO;
     struct dentry *p = dentry->d_parent;
     struct inode *inode;
 
     BUG_ON(!item);
 
     error = configfs_dirent_exists(p->d_fsdata, dentry->d_name.name);
     if (unlikely(error))
         return error;
 
     error = configfs_make_dirent(p->d_fsdata, dentry, item, mode,
                      CONFIGFS_DIR | CONFIGFS_USET_CREATING,
                      frag);
     if (unlikely(error))
         return error;
 
     configfs_set_dir_dirent_depth(p->d_fsdata, dentry->d_fsdata);
     inode = configfs_create(dentry, mode);
     if (IS_ERR(inode))
         goto out_remove;
 
     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);
     d_instantiate(dentry, inode);
     /* already hashed */
     dget(dentry);  /* pin directory dentries in core */
     inc_nlink(d_inode(p));
     item->ci_dentry = dentry;
     return 0;
 
 out_remove:
     configfs_remove_dirent(dentry);
     return PTR_ERR(inode);
 }
 
 /*
  * Allow userspace to create new entries under a new directory created with
  * configfs_create_dir(), and under all of its chidlren directories recursively.
  * @sd      configfs_dirent of the new directory to validate
  *
  * Caller must hold configfs_dirent_lock.
  */
 static void configfs_dir_set_ready(struct configfs_dirent *sd)
 {
     struct configfs_dirent *child_sd;
 
     sd->s_type &= ~CONFIGFS_USET_CREATING;
     list_for_each_entry(child_sd, &sd->s_children, s_sibling)
         if (child_sd->s_type & CONFIGFS_USET_CREATING)
             configfs_dir_set_ready(child_sd);
 }
 
 /*
  * Check that a directory does not belong to a directory hierarchy being
  * attached and not validated yet.
  * @sd      configfs_dirent of the directory to check
  *
  * @return  non-zero iff the directory was validated
  *
  * Note: takes configfs_dirent_lock, so the result may change from false to true
  * in two consecutive calls, but never from true to false.
  */
 int configfs_dirent_is_ready(struct configfs_dirent *sd)
 {
     int ret;
 
     spin_lock(&configfs_dirent_lock);
     ret = !(sd->s_type & CONFIGFS_USET_CREATING);
     spin_unlock(&configfs_dirent_lock);
 
     return ret;
 }
 
 int configfs_create_link(struct configfs_dirent *target, struct dentry *parent,
         struct dentry *dentry, char *body)
 {
     int err = 0;
     umode_t mode = S_IFLNK | S_IRWXUGO;
     struct configfs_dirent *p = parent->d_fsdata;
     struct inode *inode;
 
     err = configfs_make_dirent(p, dentry, target, mode, CONFIGFS_ITEM_LINK,
             p->s_frag);
     if (err)
         return err;
 
     inode = configfs_create(dentry, mode);
     if (IS_ERR(inode))
         goto out_remove;
 
     inode->i_link = body;
     inode->i_op = &configfs_symlink_inode_operations;
     d_instantiate(dentry, inode);
     dget(dentry);  /* pin link dentries in core */
     return 0;
 
 out_remove:
     configfs_remove_dirent(dentry);
     return PTR_ERR(inode);
 }
 
 static void remove_dir(struct dentry * d)
 {
     struct dentry * parent = dget(d->d_parent);
 
     configfs_remove_dirent(d);
 
     if (d_really_is_positive(d))
         simple_rmdir(d_inode(parent),d);
 
     pr_debug(" o %pd removing done (%d)\n", d, d_count(d));
 
     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.
  *
  * Caller holds the mutex of the item's inode
  */
 
 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);
 }
 
 static struct dentry * configfs_lookup(struct inode *dir,
                        struct dentry *dentry,
                        unsigned int flags)
 {
     struct configfs_dirent * parent_sd = dentry->d_parent->d_fsdata;
     struct configfs_dirent * sd;
     struct inode *inode = NULL;
 
     if (dentry->d_name.len > NAME_MAX)
         return ERR_PTR(-ENAMETOOLONG);
 
     /*
      * Fake invisibility if dir belongs to a group/default groups hierarchy
      * being attached
      *
      * This forbids userspace to read/write attributes of items which may
      * not complete their initialization, since the dentries of the
      * attributes won't be instantiated.
      */
     if (!configfs_dirent_is_ready(parent_sd))
         return ERR_PTR(-ENOENT);
 
     spin_lock(&configfs_dirent_lock);
     list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
         if ((sd->s_type & CONFIGFS_NOT_PINNED) &&
             !strcmp(configfs_get_name(sd), dentry->d_name.name)) {
             struct configfs_attribute *attr = sd->s_element;
             umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
 
             dentry->d_fsdata = configfs_get(sd);
             sd->s_dentry = dentry;
             spin_unlock(&configfs_dirent_lock);
 
             inode = configfs_create(dentry, mode);
             if (IS_ERR(inode)) {
                 configfs_put(sd);
                 return ERR_CAST(inode);
             }
             if (sd->s_type & CONFIGFS_ITEM_BIN_ATTR) {
                 inode->i_size = 0;
                 inode->i_fop = &configfs_bin_file_operations;
             } else {
                 inode->i_size = PAGE_SIZE;
                 inode->i_fop = &configfs_file_operations;
             }
             goto done;
         }
     }
     spin_unlock(&configfs_dirent_lock);
 done:
     d_add(dentry, inode);
     return NULL;
 }
 
 /*
  * Only subdirectories count here.  Files (CONFIGFS_NOT_PINNED) are
  * attributes and are removed by rmdir().  We recurse, setting
  * CONFIGFS_USET_DROPPING on all children that are candidates for
  * default detach.
  * If there is an error, the caller will reset the flags via
  * configfs_detach_rollback().
  */
 static int configfs_detach_prep(struct dentry *dentry, struct dentry **wait)
 {
     struct configfs_dirent *parent_sd = dentry->d_fsdata;
     struct configfs_dirent *sd;
     int ret;
 
     /* Mark that we're trying to drop the group */
     parent_sd->s_type |= CONFIGFS_USET_DROPPING;
 
     ret = -EBUSY;
     if (parent_sd->s_links)
         goto out;
 
     ret = 0;
     list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
         if (!sd->s_element ||
             (sd->s_type & CONFIGFS_NOT_PINNED))
             continue;
         if (sd->s_type & CONFIGFS_USET_DEFAULT) {
             /* Abort if racing with mkdir() */
             if (sd->s_type & CONFIGFS_USET_IN_MKDIR) {
                 if (wait)
                     *wait= dget(sd->s_dentry);
                 return -EAGAIN;
             }
 
             /*
              * Yup, recursive.  If there's a problem, blame
              * deep nesting of default_groups
              */
             ret = configfs_detach_prep(sd->s_dentry, wait);
             if (!ret)
                 continue;
         } else
             ret = -ENOTEMPTY;
 
         break;
     }
 
 out:
     return ret;
 }
 
 /*
  * Walk the tree, resetting CONFIGFS_USET_DROPPING wherever it was
  * set.
  */
 static void configfs_detach_rollback(struct dentry *dentry)
 {
     struct configfs_dirent *parent_sd = dentry->d_fsdata;
     struct configfs_dirent *sd;
 
     parent_sd->s_type &= ~CONFIGFS_USET_DROPPING;
 
     list_for_each_entry(sd, &parent_sd->s_children, s_sibling)
         if (sd->s_type & CONFIGFS_USET_DEFAULT)
             configfs_detach_rollback(sd->s_dentry);
 }
 
 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;
         spin_lock(&configfs_dirent_lock);
         list_del_init(&sd->s_sibling);
         spin_unlock(&configfs_dirent_lock);
         configfs_drop_dentry(sd, dentry);
         configfs_put(sd);
     }
 
     /**
      * Drop reference from dget() on entrance.
      */
     dput(dentry);
 }
 
 static int populate_attrs(struct config_item *item)
 {
     const struct config_item_type *t = item->ci_type;
     struct configfs_attribute *attr;
     struct configfs_bin_attribute *bin_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 (t->ct_bin_attrs) {
         for (i = 0; (bin_attr = t->ct_bin_attrs[i]) != NULL; i++) {
             error = configfs_create_bin_file(item, bin_attr);
             if (error)
                 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,
                  struct configfs_fragment *frag);
 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;
 
         inode_lock(d_inode(child));
 
         configfs_detach_group(sd->s_element);
         d_inode(child)->i_flags |= S_DEAD;
         dont_mount(child);
 
         inode_unlock(d_inode(child));
 
         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,
                 struct configfs_fragment *frag)
 {
     int ret;
     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;
 
     ret = -ENOMEM;
     child = d_alloc_name(parent, group->cg_item.ci_name);
     if (child) {
         d_add(child, NULL);
 
         ret = configfs_attach_group(&parent_group->cg_item,
                         &group->cg_item, child, frag);
         if (!ret) {
             sd = child->d_fsdata;
             sd->s_type |= CONFIGFS_USET_DEFAULT;
         } else {
             BUG_ON(d_inode(child));
             d_drop(child);
             dput(child);
         }
     }
 
     return ret;
 }
 
 static int populate_groups(struct config_group *group,
                struct configfs_fragment *frag)
 {
     struct config_group *new_group;
     int ret = 0;
 
     list_for_each_entry(new_group, &group->default_groups, group_entry) {
         ret = create_default_group(group, new_group, frag);
         if (ret) {
             detach_groups(group);
             break;
         }
     }
 
     return ret;
 }
 
 void configfs_remove_default_groups(struct config_group *group)
 {
     struct config_group *g, *n;
 
     list_for_each_entry_safe(g, n, &group->default_groups, group_entry) {
         list_del(&g->group_entry);
         config_item_put(&g->cg_item);
     }
 }
 EXPORT_SYMBOL(configfs_remove_default_groups);
 
 /*
  * 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)
 {
     struct config_group *new_group;
 
     list_for_each_entry(new_group, &group->default_groups, group_entry)
         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)
 {
     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;
 
     list_for_each_entry(new_group, &group->default_groups, group_entry)
         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,
                 struct configfs_fragment *frag)
 {
     int ret;
 
     ret = configfs_create_dir(item, dentry, frag);
     if (!ret) {
         ret = populate_attrs(item);
         if (ret) {
             /*
              * We are going to remove an inode and its dentry but
              * the VFS may already have hit and used them. Thus,
              * we must lock them as rmdir() would.
              */
             inode_lock(d_inode(dentry));
             configfs_remove_dir(item);
             d_inode(dentry)->i_flags |= S_DEAD;
             dont_mount(dentry);
             inode_unlock(d_inode(dentry));
             d_delete(dentry);
         }
     }
 
     return ret;
 }
 
 /* Caller holds the mutex of the item's inode */
 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,
                  struct configfs_fragment *frag)
 {
     int ret;
     struct configfs_dirent *sd;
 
     ret = configfs_attach_item(parent_item, item, dentry, frag);
     if (!ret) {
         sd = dentry->d_fsdata;
         sd->s_type |= CONFIGFS_USET_DIR;
 
         /*
          * FYI, we're faking mkdir in populate_groups()
          * We must lock the group's inode to avoid races with the VFS
          * which can already hit the inode and try to add/remove entries
          * under it.
          *
          * We must also lock the inode to remove it safely in case of
          * error, as rmdir() would.
          */
         inode_lock_nested(d_inode(dentry), I_MUTEX_CHILD);
         configfs_adjust_dir_dirent_depth_before_populate(sd);
         ret = populate_groups(to_config_group(item), frag);
         if (ret) {
             configfs_detach_item(item);
             d_inode(dentry)->i_flags |= S_DEAD;
             dont_mount(dentry);
         }
         configfs_adjust_dir_dirent_depth_after_populate(sd);
         inode_unlock(d_inode(dentry));
         if (ret)
             d_delete(dentry);
     }
 
     return ret;
 }
 
 /* Caller holds the mutex of the group's inode */
 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)
 {
     const 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)
 {
     const 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)
 {
     pr_info("%*s\"%s\":\n", level, " ", configfs_get_name(sd));
 
 #define type_print(_type) if (sd->s_type & _type) pr_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 dependent 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 configfs_dirent_lock.
  * 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 configfs_dirent_lock helps
  * locking 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 deliberately ignore items tagged as dropping since they are virtually
  * dead, as well as items in the middle of attachment since they virtually
  * do not exist yet. This completes the locking out of racing mkdir() and
  * rmdir().
  * Note: subdirectories in the middle of attachment start with s_type =
  * CONFIGFS_DIR|CONFIGFS_USET_CREATING set by create_dir().  When
  * CONFIGFS_USET_CREATING is set, we ignore the item.  The actual set of
  * s_type is in configfs_new_dirent(), which has configfs_dirent_lock.
  *
  * If the target is not found, -ENOENT is bubbled up.
  *
  * This adds a requirement that all config_items be unique!
  *
  * This is recursive.  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;
     int ret = 0;
 
     BUG_ON(!origin || !origin->d_fsdata);
     sd = origin->d_fsdata;
 
     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) &&
             !(child_sd->s_type & CONFIGFS_USET_DROPPING) &&
             !(child_sd->s_type & CONFIGFS_USET_CREATING)) {
             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 */
     ret = -ENOENT;
 
 out:
     return ret;
 }
 
 static int configfs_do_depend_item(struct dentry *subsys_dentry,
                    struct config_item *target)
 {
     struct configfs_dirent *p;
     int ret;
 
     spin_lock(&configfs_dirent_lock);
     /* Scan the tree, return 0 if found */
     ret = configfs_depend_prep(subsys_dentry, target);
     if (ret)
         goto out_unlock_dirent_lock;
 
     /*
      * We are sure that the item is not about to be removed by rmdir(), and
      * not in the middle of attachment by mkdir().
      */
     p = target->ci_dentry->d_fsdata;
     p->s_dependent_count += 1;
 
 out_unlock_dirent_lock:
     spin_unlock(&configfs_dirent_lock);
 
     return ret;
 }
 
 static inline struct configfs_dirent *
 configfs_find_subsys_dentry(struct configfs_dirent *root_sd,
                 struct config_item *subsys_item)
 {
     struct configfs_dirent *p;
     struct configfs_dirent *ret = NULL;
 
     list_for_each_entry(p, &root_sd->s_children, s_sibling) {
         if (p->s_type & CONFIGFS_DIR &&
             p->s_element == subsys_item) {
             ret = p;
             break;
         }
     }
 
     return ret;
 }
 
 
 int configfs_depend_item(struct configfs_subsystem *subsys,
              struct config_item *target)
 {
     int ret;
     struct configfs_dirent *subsys_sd;
     struct config_item *s_item = &subsys->su_group.cg_item;
     struct dentry *root;
 
     /*
      * Pin the configfs filesystem.  This means we can safely access
      * the root of the configfs filesystem.
      */
     root = configfs_pin_fs();
     if (IS_ERR(root))
         return PTR_ERR(root);
 
     /*
      * 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().
      */
     inode_lock(d_inode(root));
 
     subsys_sd = configfs_find_subsys_dentry(root->d_fsdata, s_item);
     if (!subsys_sd) {
         ret = -ENOENT;
         goto out_unlock_fs;
     }
 
     /* Ok, now we can trust subsys/s_item */
     ret = configfs_do_depend_item(subsys_sd->s_dentry, target);
 
 out_unlock_fs:
     inode_unlock(d_inode(root));
 
     /*
      * 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 the client driver is
  * pinned, thus the subsystem is pinned, and therefore configfs is pinned.
  */
 void configfs_undepend_item(struct config_item *target)
 {
     struct configfs_dirent *sd;
 
     /*
      * Since we can trust everything is pinned, we just need
      * configfs_dirent_lock.
      */
     spin_lock(&configfs_dirent_lock);
 
     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.
      */
     spin_unlock(&configfs_dirent_lock);
 }
 EXPORT_SYMBOL(configfs_undepend_item);
 
 /*
  * caller_subsys is a caller's subsystem not target's. This is used to
  * determine if we should lock root and check subsys or not. When we are
  * in the same subsystem as our target there is no need to do locking as
  * we know that subsys is valid and is not unregistered during this function
  * as we are called from callback of one of his children and VFS holds a lock
  * on some inode. Otherwise we have to lock our root to  ensure that target's
  * subsystem it is not unregistered during this function.
  */
 int configfs_depend_item_unlocked(struct configfs_subsystem *caller_subsys,
                   struct config_item *target)
 {
     struct configfs_subsystem *target_subsys;
     struct config_group *root, *parent;
     struct configfs_dirent *subsys_sd;
     int ret = -ENOENT;
 
     /* Disallow this function for configfs root */
     if (configfs_is_root(target))
         return -EINVAL;
 
     parent = target->ci_group;
     /*
      * This may happen when someone is trying to depend root
      * directory of some subsystem
      */
     if (configfs_is_root(&parent->cg_item)) {
         target_subsys = to_configfs_subsystem(to_config_group(target));
         root = parent;
     } else {
         target_subsys = parent->cg_subsys;
         /* Find a cofnigfs root as we may need it for locking */
         for (root = parent; !configfs_is_root(&root->cg_item);
              root = root->cg_item.ci_group)
             ;
     }
 
     if (target_subsys != caller_subsys) {
         /*
          * We are in other configfs subsystem, so we have to do
          * additional locking to prevent other subsystem from being
          * unregistered
          */
         inode_lock(d_inode(root->cg_item.ci_dentry));
 
         /*
          * As we are trying to depend item from other subsystem
          * we have to check if this subsystem is still registered
          */
         subsys_sd = configfs_find_subsys_dentry(
                 root->cg_item.ci_dentry->d_fsdata,
                 &target_subsys->su_group.cg_item);
         if (!subsys_sd)
             goto out_root_unlock;
     } else {
         subsys_sd = target_subsys->su_group.cg_item.ci_dentry->d_fsdata;
     }
 
     /* Now we can execute core of depend item */
     ret = configfs_do_depend_item(subsys_sd->s_dentry, target);
 
     if (target_subsys != caller_subsys)
 out_root_unlock:
         /*
          * We were called from subsystem other than our target so we
          * took some locks so now it's time to release them
          */
         inode_unlock(d_inode(root->cg_item.ci_dentry));
 
     return ret;
 }
 EXPORT_SYMBOL(configfs_depend_item_unlocked);
 
 static int configfs_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
               struct dentry *dentry, umode_t mode)
 {
     int ret = 0;
     int module_got = 0;
     struct config_group *group = NULL;
     struct config_item *item = NULL;
     struct config_item *parent_item;
     struct configfs_subsystem *subsys;
     struct configfs_dirent *sd;
     const struct config_item_type *type;
     struct module *subsys_owner = NULL, *new_item_owner = NULL;
     struct configfs_fragment *frag;
     char *name;
 
     sd = dentry->d_parent->d_fsdata;
 
     /*
      * Fake invisibility if dir belongs to a group/default groups hierarchy
      * being attached
      */
     if (!configfs_dirent_is_ready(sd)) {
         ret = -ENOENT;
         goto out;
     }
 
     if (!(sd->s_type & CONFIGFS_USET_DIR)) {
         ret = -EPERM;
         goto out;
     }
 
     frag = new_fragment();
     if (!frag) {
         ret = -ENOMEM;
         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;
     }
 
     /*
      * The subsystem may belong to a different module than the item
      * being created.  We don't want to safely pin the new item but
      * fail to pin the subsystem it sits under.
      */
     if (!subsys->su_group.cg_item.ci_type) {
         ret = -EINVAL;
         goto out_put;
     }
     subsys_owner = subsys->su_group.cg_item.ci_type->ct_owner;
     if (!try_module_get(subsys_owner)) {
         ret = -EINVAL;
         goto out_put;
     }
 
     name = kmalloc(dentry->d_name.len + 1, GFP_KERNEL);
     if (!name) {
         ret = -ENOMEM;
         goto out_subsys_put;
     }
 
     snprintf(name, dentry->d_name.len + 1, "%s", dentry->d_name.name);
 
     mutex_lock(&subsys->su_mutex);
     if (type->ct_group_ops->make_group) {
         group = type->ct_group_ops->make_group(to_config_group(parent_item), name);
         if (!group)
             group = ERR_PTR(-ENOMEM);
         if (!IS_ERR(group)) {
             link_group(to_config_group(parent_item), group);
             item = &group->cg_item;
         } else
             ret = PTR_ERR(group);
     } else {
         item = type->ct_group_ops->make_item(to_config_group(parent_item), name);
         if (!item)
             item = ERR_PTR(-ENOMEM);
         if (!IS_ERR(item))
             link_obj(parent_item, item);
         else
             ret = PTR_ERR(item);
     }
     mutex_unlock(&subsys->su_mutex);
 
     kfree(name);
     if (ret) {
         /*
          * If ret != 0, then link_obj() was never called.
          * There are no extra references to clean up.
          */
         goto out_subsys_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;
     }
 
     new_item_owner = type->ct_owner;
     if (!try_module_get(new_item_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;
 
     /*
      * Make racing rmdir() fail if it did not tag parent with
      * CONFIGFS_USET_DROPPING
      * Note: if CONFIGFS_USET_DROPPING is already set, attach_group() will
      * fail and let rmdir() terminate correctly
      */
     spin_lock(&configfs_dirent_lock);
     /* This will make configfs_detach_prep() fail */
     sd->s_type |= CONFIGFS_USET_IN_MKDIR;
     spin_unlock(&configfs_dirent_lock);
 
     if (group)
         ret = configfs_attach_group(parent_item, item, dentry, frag);
     else
         ret = configfs_attach_item(parent_item, item, dentry, frag);
 
     spin_lock(&configfs_dirent_lock);
     sd->s_type &= ~CONFIGFS_USET_IN_MKDIR;
     if (!ret)
         configfs_dir_set_ready(dentry->d_fsdata);
     spin_unlock(&configfs_dirent_lock);
 
 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(new_item_owner);
     }
 
 out_subsys_put:
     if (ret)
         module_put(subsys_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);
     put_fragment(frag);
 
 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 configfs_fragment *frag;
     struct module *subsys_owner = NULL, *dead_item_owner = NULL;
     int ret;
 
     sd = dentry->d_fsdata;
     if (sd->s_type & CONFIGFS_USET_DEFAULT)
         return -EPERM;
 
     /* 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;
     }
 
     /* configfs_mkdir() shouldn't have allowed this */
     BUG_ON(!subsys->su_group.cg_item.ci_type);
     subsys_owner = subsys->su_group.cg_item.ci_type->ct_owner;
 
     /*
      * Ensure that no racing symlink() will make detach_prep() fail while
      * the new link is temporarily attached
      */
     do {
         struct dentry *wait;
 
         mutex_lock(&configfs_symlink_mutex);
         spin_lock(&configfs_dirent_lock);
         /*
          * Here's where we check for dependents.  We're protected by
          * configfs_dirent_lock.
          * If no dependent, atomically tag the item as dropping.
          */
         ret = sd->s_dependent_count ? -EBUSY : 0;
         if (!ret) {
             ret = configfs_detach_prep(dentry, &wait);
             if (ret)
                 configfs_detach_rollback(dentry);
         }
         spin_unlock(&configfs_dirent_lock);
         mutex_unlock(&configfs_symlink_mutex);
 
         if (ret) {
             if (ret != -EAGAIN) {
                 config_item_put(parent_item);
                 return ret;
             }
 
             /* Wait until the racing operation terminates */
             inode_lock(d_inode(wait));
             inode_unlock(d_inode(wait));
             dput(wait);
         }
     } while (ret == -EAGAIN);
 
     frag = sd->s_frag;
     if (down_write_killable(&frag->frag_sem)) {
         spin_lock(&configfs_dirent_lock);
         configfs_detach_rollback(dentry);
         spin_unlock(&configfs_dirent_lock);
         config_item_put(parent_item);
         return -EINTR;
     }
     frag->frag_dead = true;
     up_write(&frag->frag_sem);
 
     /* 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)
         dead_item_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(dead_item_owner);
     module_put(subsys_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,
 };
 
 const struct inode_operations configfs_root_inode_operations = {
     .lookup     = configfs_lookup,
     .setattr    = configfs_setattr,
 };
 
 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;
     int err;
 
     inode_lock(d_inode(dentry));
     /*
      * Fake invisibility if dir belongs to a group/default groups hierarchy
      * being attached
      */
     err = -ENOENT;
     if (configfs_dirent_is_ready(parent_sd)) {
         file->private_data = configfs_new_dirent(parent_sd, NULL, 0, NULL);
         if (IS_ERR(file->private_data))
             err = PTR_ERR(file->private_data);
         else
             err = 0;
     }
     inode_unlock(d_inode(dentry));
 
     return err;
 }
 
 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;
 
     inode_lock(d_inode(dentry));
     spin_lock(&configfs_dirent_lock);
     list_del_init(&cursor->s_sibling);
     spin_unlock(&configfs_dirent_lock);
     inode_unlock(d_inode(dentry));
 
     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 *file, struct dir_context *ctx)
 {
     struct dentry *dentry = file->f_path.dentry;
     struct super_block *sb = dentry->d_sb;
     struct configfs_dirent * parent_sd = dentry->d_fsdata;
     struct configfs_dirent *cursor = file->private_data;
     struct list_head *p, *q = &cursor->s_sibling;
     ino_t ino = 0;
 
     if (!dir_emit_dots(file, ctx))
         return 0;
     spin_lock(&configfs_dirent_lock);
     if (ctx->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;
         struct inode *inode = NULL;
 
         next = list_entry(p, struct configfs_dirent, s_sibling);
         if (!next->s_element)
             continue;
 
         /*
          * We'll have a dentry and an inode for
          * PINNED items and for open attribute
          * files.  We lock here to prevent a race
          * with configfs_d_iput() clearing
          * s_dentry before calling iput().
          *
          * Why do we go to the trouble?  If
          * someone has an attribute file open,
          * the inode number should match until
          * they close it.  Beyond that, we don't
          * care.
          */
         dentry = next->s_dentry;
         if (dentry)
             inode = d_inode(dentry);
         if (inode)
             ino = inode->i_ino;
         spin_unlock(&configfs_dirent_lock);
         if (!inode)
             ino = iunique(sb, 2);
 
         name = configfs_get_name(next);
         len = strlen(name);
 
         if (!dir_emit(ctx, name, len, ino, dt_type(next)))
             return 0;
 
         spin_lock(&configfs_dirent_lock);
         list_move(q, p);
         p = q;
         ctx->pos++;
     }
     spin_unlock(&configfs_dirent_lock);
     return 0;
 }
 
 static loff_t configfs_dir_lseek(struct file *file, loff_t offset, int whence)
 {
     struct dentry * dentry = file->f_path.dentry;
 
     switch (whence) {
         case 1:
             offset += file->f_pos;
             fallthrough;
         case 0:
             if (offset >= 0)
                 break;
             fallthrough;
         default:
             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;
 
             spin_lock(&configfs_dirent_lock);
             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);
             spin_unlock(&configfs_dirent_lock);
         }
     }
     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,
     .iterate_shared = configfs_readdir,
 };
 
 /**
  * configfs_register_group - creates a parent-child relation between two groups
  * @parent_group:   parent group
  * @group:      child group
  *
  * link groups, creates dentry for the child and attaches it to the
  * parent dentry.
  *
  * Return: 0 on success, negative errno code on error
  */
 int configfs_register_group(struct config_group *parent_group,
                 struct config_group *group)
 {
     struct configfs_subsystem *subsys = parent_group->cg_subsys;
     struct dentry *parent;
     struct configfs_fragment *frag;
     int ret;
 
     frag = new_fragment();
     if (!frag)
         return -ENOMEM;
 
     mutex_lock(&subsys->su_mutex);
     link_group(parent_group, group);
     mutex_unlock(&subsys->su_mutex);
 
     parent = parent_group->cg_item.ci_dentry;
 
     inode_lock_nested(d_inode(parent), I_MUTEX_PARENT);
     ret = create_default_group(parent_group, group, frag);
     if (ret)
         goto err_out;
 
     spin_lock(&configfs_dirent_lock);
     configfs_dir_set_ready(group->cg_item.ci_dentry->d_fsdata);
     spin_unlock(&configfs_dirent_lock);
     inode_unlock(d_inode(parent));
     put_fragment(frag);
     return 0;
 err_out:
     inode_unlock(d_inode(parent));
     mutex_lock(&subsys->su_mutex);
     unlink_group(group);
     mutex_unlock(&subsys->su_mutex);
     put_fragment(frag);
     return ret;
 }
 EXPORT_SYMBOL(configfs_register_group);
 
 /**
  * configfs_unregister_group() - unregisters a child group from its parent
  * @group: parent group to be unregistered
  *
  * Undoes configfs_register_group()
  */
 void configfs_unregister_group(struct config_group *group)
 {
     struct configfs_subsystem *subsys = group->cg_subsys;
     struct dentry *dentry = group->cg_item.ci_dentry;
     struct dentry *parent = group->cg_item.ci_parent->ci_dentry;
     struct configfs_dirent *sd = dentry->d_fsdata;
     struct configfs_fragment *frag = sd->s_frag;
 
     down_write(&frag->frag_sem);
     frag->frag_dead = true;
     up_write(&frag->frag_sem);
 
     inode_lock_nested(d_inode(parent), I_MUTEX_PARENT);
     spin_lock(&configfs_dirent_lock);
     configfs_detach_prep(dentry, NULL);
     spin_unlock(&configfs_dirent_lock);
 
     configfs_detach_group(&group->cg_item);
     d_inode(dentry)->i_flags |= S_DEAD;
     dont_mount(dentry);
     d_drop(dentry);
     fsnotify_rmdir(d_inode(parent), dentry);
     inode_unlock(d_inode(parent));
 
     dput(dentry);
 
     mutex_lock(&subsys->su_mutex);
     unlink_group(group);
     mutex_unlock(&subsys->su_mutex);
 }
 EXPORT_SYMBOL(configfs_unregister_group);
 
 /**
  * configfs_register_default_group() - allocates and registers a child group
  * @parent_group:   parent group
  * @name:       child group name
  * @item_type:      child item type description
  *
  * boilerplate to allocate and register a child group with its parent. We need
  * kzalloc'ed memory because child's default_group is initially empty.
  *
  * Return: allocated config group or ERR_PTR() on error
  */
 struct config_group *
 configfs_register_default_group(struct config_group *parent_group,
                 const char *name,
                 const struct config_item_type *item_type)
 {
     int ret;
     struct config_group *group;
 
     group = kzalloc(sizeof(*group), GFP_KERNEL);
     if (!group)
         return ERR_PTR(-ENOMEM);
     config_group_init_type_name(group, name, item_type);
 
     ret = configfs_register_group(parent_group, group);
     if (ret) {
         kfree(group);
         return ERR_PTR(ret);
     }
     return group;
 }
 EXPORT_SYMBOL(configfs_register_default_group);
 
 /**
  * configfs_unregister_default_group() - unregisters and frees a child group
  * @group:  the group to act on
  */
 void configfs_unregister_default_group(struct config_group *group)
 {
     configfs_unregister_group(group);
     kfree(group);
 }
 EXPORT_SYMBOL(configfs_unregister_default_group);
 
 int configfs_register_subsystem(struct configfs_subsystem *subsys)
 {
     int err;
     struct config_group *group = &subsys->su_group;
     struct dentry *dentry;
     struct dentry *root;
     struct configfs_dirent *sd;
     struct configfs_fragment *frag;
 
     frag = new_fragment();
     if (!frag)
         return -ENOMEM;
 
     root = configfs_pin_fs();
     if (IS_ERR(root)) {
         put_fragment(frag);
         return PTR_ERR(root);
     }
 
     if (!group->cg_item.ci_name)
         group->cg_item.ci_name = group->cg_item.ci_namebuf;
 
     sd = root->d_fsdata;
     mutex_lock(&configfs_subsystem_mutex);
     link_group(to_config_group(sd->s_element), group);
     mutex_unlock(&configfs_subsystem_mutex);
 
     inode_lock_nested(d_inode(root), I_MUTEX_PARENT);
 
     err = -ENOMEM;
     dentry = d_alloc_name(root, group->cg_item.ci_name);
     if (dentry) {
         d_add(dentry, NULL);
 
         err = configfs_attach_group(sd->s_element, &group->cg_item,
                         dentry, frag);
         if (err) {
             BUG_ON(d_inode(dentry));
             d_drop(dentry);
             dput(dentry);
         } else {
             spin_lock(&configfs_dirent_lock);
             configfs_dir_set_ready(dentry->d_fsdata);
             spin_unlock(&configfs_dirent_lock);
         }
     }
 
     inode_unlock(d_inode(root));
 
     if (err) {
         mutex_lock(&configfs_subsystem_mutex);
         unlink_group(group);
         mutex_unlock(&configfs_subsystem_mutex);
         configfs_release_fs();
     }
     put_fragment(frag);
 
     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;
     struct dentry *root = dentry->d_sb->s_root;
     struct configfs_dirent *sd = dentry->d_fsdata;
     struct configfs_fragment *frag = sd->s_frag;
 
     if (dentry->d_parent != root) {
         pr_err("Tried to unregister non-subsystem!\n");
         return;
     }
 
     down_write(&frag->frag_sem);
     frag->frag_dead = true;
     up_write(&frag->frag_sem);
 
     inode_lock_nested(d_inode(root),
               I_MUTEX_PARENT);
     inode_lock_nested(d_inode(dentry), I_MUTEX_CHILD);
     mutex_lock(&configfs_symlink_mutex);
     spin_lock(&configfs_dirent_lock);
     if (configfs_detach_prep(dentry, NULL)) {
         pr_err("Tried to unregister non-empty subsystem!\n");
     }
     spin_unlock(&configfs_dirent_lock);
     mutex_unlock(&configfs_symlink_mutex);
     configfs_detach_group(&group->cg_item);
     d_inode(dentry)->i_flags |= S_DEAD;
     dont_mount(dentry);
     inode_unlock(d_inode(dentry));
 
     d_drop(dentry);
     fsnotify_rmdir(d_inode(root), dentry);
 
     inode_unlock(d_inode(root));
 
     dput(dentry);
 
     mutex_lock(&configfs_subsystem_mutex);
     unlink_group(group);
     mutex_unlock(&configfs_subsystem_mutex);
     configfs_release_fs();
 }
 
 EXPORT_SYMBOL(configfs_register_subsystem);
 EXPORT_SYMBOL(configfs_unregister_subsystem);

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