Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1950 insertions, 0 deletions

diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
new file mode 100644
index 0000000000..18677cd4e6
--- /dev/null
+++ b/fs/configfs/dir.c
@@ -0,0 +1,1950 @@
+// 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_put(dentry->d_fsdata);
+	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_put(dentry->d_fsdata);
+	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 mnt_idmap *idmap, 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;
+}
+
+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,
+			      fs_umode_to_dtype(next->s_mode)))
+			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);