- 根目录:
- fs
- configfs
- dir.c
/* -*- mode: c; c-basic-offset: 8; -*-
* vim: noexpandtab sw=8 ts=8 sts=0:
*
* dir.c - Operations for configfs directories.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public
* License along with this program; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 021110-1307, USA.
*
* Based on sysfs:
* sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
*
* configfs Copyright (C) 2005 Oracle. All rights reserved.
*/
#undef DEBUG
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/configfs.h>
#include "configfs_internal.h"
DECLARE_RWSEM(configfs_rename_sem);
/*
* 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);
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);
/* Coordinate with configfs_attach_attr where will increase
* sd->s_count and update sd->s_dentry to new allocated one.
* Only set sd->dentry to null when this dentry is the only
* sd owner.
* If not do so, configfs_d_iput may run just after
* configfs_attach_attr and set sd->s_dentry to null
* even it's still in use.
*/
if (atomic_read(&sd->s_count) <= 2)
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 */
/*
* 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_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_links);
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);
}
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_dirent * sd;
sd = configfs_new_dirent(parent_sd, element, type);
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 init_dir(struct inode * inode)
{
inode->i_op = &configfs_dir_inode_operations;
inode->i_fop = &configfs_dir_operations;
/* directory inodes start off with i_nlink == 2 (for "." entry) */
inc_nlink(inode);
}
static void configfs_init_file(struct inode * inode)
{
inode->i_size = PAGE_SIZE;
inode->i_fop = &configfs_file_operations;
}
static void init_symlink(struct inode * inode)
{
inode->i_op = &configfs_symlink_inode_operations;
}
/**
* configfs_create_dir - create a directory for an config_item.
* @item: config_itemwe're creating directory for.
* @dentry: config_item's dentry.
*
* 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)
{
int error;
umode_t mode = S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO;
struct dentry *p = dentry->d_parent;
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);
if (unlikely(error))
return error;
configfs_set_dir_dirent_depth(p->d_fsdata, dentry->d_fsdata);
error = configfs_create(dentry, mode, init_dir);
if (!error) {
inc_nlink(d_inode(p));
item->ci_dentry = dentry;
} else {
struct configfs_dirent *sd = dentry->d_fsdata;
if (sd) {
spin_lock(&configfs_dirent_lock);
list_del_init(&sd->s_sibling);
spin_unlock(&configfs_dirent_lock);
configfs_put(sd);
}
}
return error;
}
/*
* 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_symlink *sl,
struct dentry *parent,
struct dentry *dentry)
{
int err = 0;
umode_t mode = S_IFLNK | S_IRWXUGO;
err = configfs_make_dirent(parent->d_fsdata, dentry, sl, mode,
CONFIGFS_ITEM_LINK);
if (!err) {
err = configfs_create(dentry, mode, init_symlink);
if (err) {
struct configfs_dirent *sd = dentry->d_fsdata;
if (sd) {
spin_lock(&configfs_dirent_lock);
list_del_init(&sd->s_sibling);
spin_unlock(&configfs_dirent_lock);
configfs_put(sd);
}
}
}
return err;
}
static void remove_dir(struct dentry * d)
{
struct dentry * parent = dget(d->d_parent);
struct configfs_dirent * sd;
sd = d->d_fsdata;
spin_lock(&configfs_dirent_lock);
list_del_init(&sd->s_sibling);
spin_unlock(&configfs_dirent_lock);
configfs_put(sd);
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);
}
/* attaches attribute's configfs_dirent to the dentry corresponding to the
* attribute file
*/
static int configfs_attach_attr(struct configfs_dirent * sd, struct dentry * dentry)
{
struct configfs_attribute * attr = sd->s_element;
int error;
spin_lock(&configfs_dirent_lock);
dentry->d_fsdata = configfs_get(sd);
sd->s_dentry = dentry;
spin_unlock(&configfs_dirent_lock);
error = configfs_create(dentry, (attr->ca_mode & S_IALLUGO) | S_IFREG,
configfs_init_file);
if (error) {
configfs_put(sd);
return error;
}
d_rehash(dentry);
return 0;
}
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;
int found = 0;
int err;
/*
* 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.
*/
err = -ENOENT;
if (!configfs_dirent_is_ready(parent_sd))
goto out;
list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
if (sd->s_type & CONFIGFS_NOT_PINNED) {
const unsigned char * name = configfs_get_name(sd);
if (strcmp(name, dentry->d_name.name))
continue;
found = 1;
err = configfs_attach_attr(sd, dentry);
break;
}
}
if (!found) {
/*
* If it doesn't exist and it isn't a NOT_PINNED item,
* it must be negative.
*/
if (dentry->d_name.len > NAME_MAX)
return ERR_PTR(-ENAMETOOLONG);
d_add(dentry, NULL);
return NULL;
}
out:
return ERR_PTR(err);
}
/*
* 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 mutex **wait_mutex)
{
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 (!list_empty(&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_mutex)
*wait_mutex = &d_inode(sd->s_dentry)->i_mutex;
return -EAGAIN;
}
/*
* Yup, recursive. If there's a problem, blame
* deep nesting of default_groups
*/
ret = configfs_detach_prep(sd->s_dentry, wait_mutex);
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)
{
struct config_item_type *t = item->ci_type;
struct configfs_attribute *attr;
int error = 0;
int i;
if (!t)
return -EINVAL;
if (t->ct_attrs) {
for (i = 0; (attr = t->ct_attrs[i]) != NULL; i++) {
if ((error = configfs_create_file(item, attr)))
break;
}
}
if (error)
detach_attrs(item);
return error;
}
static int configfs_attach_group(struct config_item *parent_item,
struct config_item *item,
struct dentry *dentry);
static void configfs_detach_group(struct config_item *item);
static void detach_groups(struct config_group *group)
{
struct dentry * dentry = dget(group->cg_item.ci_dentry);
struct dentry *child;
struct configfs_dirent *parent_sd;
struct configfs_dirent *sd, *tmp;
if (!dentry)
return;
parent_sd = dentry->d_fsdata;
list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) {
if (!sd->s_element ||
!(sd->s_type & CONFIGFS_USET_DEFAULT))
continue;
child = sd->s_dentry;
mutex_lock(&d_inode(child)->i_mutex);
configfs_detach_group(sd->s_element);
d_inode(child)->i_flags |= S_DEAD;
dont_mount(child);
mutex_unlock(&d_inode(child)->i_mutex);
d_delete(child);
dput(child);
}
/**
* Drop reference from dget() on entrance.
*/
dput(dentry);
}
/*
* This fakes mkdir(2) on a default_groups[] entry. It
* creates a dentry, attachs it, and then does fixup
* on the sd->s_type.
*
* We could, perhaps, tweak our parent's ->mkdir for a minute and
* try using vfs_mkdir. Just a thought.
*/
static int create_default_group(struct config_group *parent_group,
struct config_group *group)
{
int ret;
struct 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);
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 config_group *new_group;
int ret = 0;
int i;
if (group->default_groups) {
for (i = 0; group->default_groups[i]; i++) {
new_group = group->default_groups[i];
ret = create_default_group(group, new_group);
if (ret) {
detach_groups(group);
break;
}
}
}
return ret;
}
/*
* All of link_obj/unlink_obj/link_group/unlink_group require that
* subsys->su_mutex is held.
*/
static void unlink_obj(struct config_item *item)
{
struct config_group *group;
group = item->ci_group;
if (group) {
list_del_init(&item->ci_entry);
item->ci_group = NULL;
item->ci_parent = NULL;
/* Drop the reference for ci_entry */
config_item_put(item);
/* Drop the reference for ci_parent */
config_group_put(group);
}
}
static void link_obj(struct config_item *parent_item, struct config_item *item)
{
/*
* Parent seems redundant with group, but it makes certain
* traversals much nicer.
*/
item->ci_parent = parent_item;
/*
* We hold a reference on the parent for the child's ci_parent
* link.
*/
item->ci_group = config_group_get(to_config_group(parent_item));
list_add_tail(&item->ci_entry, &item->ci_group->cg_children);
/*
* We hold a reference on the child for ci_entry on the parent's
* cg_children
*/
config_item_get(item);
}
static void unlink_group(struct config_group *group)
{
int i;
struct config_group *new_group;
if (group->default_groups) {
for (i = 0; group->default_groups[i]; i++) {
new_group = group->default_groups[i];
unlink_group(new_group);
}
}
group->cg_subsys = NULL;
unlink_obj(&group->cg_item);
}
static void link_group(struct config_group *parent_group, struct config_group *group)
{
int i;
struct config_group *new_group;
struct configfs_subsystem *subsys = NULL; /* gcc is a turd */
link_obj(&parent_group->cg_item, &group->cg_item);
if (parent_group->cg_subsys)
subsys = parent_group->cg_subsys;
else if (configfs_is_root(&parent_group->cg_item))
subsys = to_configfs_subsystem(group);
else
BUG();
group->cg_subsys = subsys;
if (group->default_groups) {
for (i = 0; group->default_groups[i]; i++) {
new_group = group->default_groups[i];
link_group(group, new_group);
}
}
}
/*
* The goal is that configfs_attach_item() (and
* configfs_attach_group()) can be called from either the VFS or this
* module. That is, they assume that the items have been created,
* the dentry allocated, and the dcache is all ready to go.
*
* If they fail, they must clean up after themselves as if they
* had never been called. The caller (VFS or local function) will
* handle cleaning up the dcache bits.
*
* configfs_detach_group() and configfs_detach_item() behave similarly on
* the way out. They assume that the proper semaphores are held, they
* clean up the configfs items, and they expect their callers will
* handle the dcache bits.
*/
static int configfs_attach_item(struct config_item *parent_item,
struct config_item *item,
struct dentry *dentry)
{
int ret;
ret = configfs_create_dir(item, dentry);
if (!ret) {
ret = populate_attrs(item);
if (ret) {
/*
* 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.
*/
mutex_lock(&d_inode(dentry)->i_mutex);
configfs_remove_dir(item);
d_inode(dentry)->i_flags |= S_DEAD;
dont_mount(dentry);
mutex_unlock(&d_inode(dentry)->i_mutex);
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)
{
int ret;
struct configfs_dirent *sd;
ret = configfs_attach_item(parent_item, item, dentry);
if (!ret) {
sd = dentry->d_fsdata;
sd->s_type |= CONFIGFS_USET_DIR;
/*
* 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.
*/
mutex_lock_nested(&d_inode(dentry)->i_mutex, I_MUTEX_CHILD);
configfs_adjust_dir_dirent_depth_before_populate(sd);
ret = populate_groups(to_config_group(item));
if (ret) {
configfs_detach_item(item);
d_inode(dentry)->i_flags |= S_DEAD;
dont_mount(dentry);
}
configfs_adjust_dir_dirent_depth_after_populate(sd);
mutex_unlock(&d_inode(dentry)->i_mutex);
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)
{
struct config_item_type *type;
type = parent_item->ci_type;
BUG_ON(!type);
if (type->ct_group_ops && type->ct_group_ops->disconnect_notify)
type->ct_group_ops->disconnect_notify(to_config_group(parent_item),
item);
}
/*
* Drop the initial reference from make_item()/make_group()
* This function assumes that reference is held on item
* and that item holds a valid reference to the parent. Also, it
* assumes the caller has validated ci_type.
*/
static void client_drop_item(struct config_item *parent_item,
struct config_item *item)
{
struct config_item_type *type;
type = parent_item->ci_type;
BUG_ON(!type);
/*
* If ->drop_item() exists, it is responsible for the
* config_item_put().
*/
if (type->ct_group_ops && type->ct_group_ops->drop_item)
type->ct_group_ops->drop_item(to_config_group(parent_item),
item);
else
config_item_put(item);
}
#ifdef DEBUG
static void configfs_dump_one(struct configfs_dirent *sd, int level)
{
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;
}
int configfs_depend_item(struct configfs_subsystem *subsys,
struct config_item *target)
{
int ret;
struct configfs_dirent *p, *root_sd, *subsys_sd = NULL;
struct config_item *s_item = &subsys->su_group.cg_item;
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().
*/
mutex_lock(&d_inode(root)->i_mutex);
root_sd = root->d_fsdata;
list_for_each_entry(p, &root_sd->s_children, s_sibling) {
if (p->s_type & CONFIGFS_DIR) {
if (p->s_element == s_item) {
subsys_sd = p;
break;
}
}
}
if (!subsys_sd) {
ret = -ENOENT;
goto out_unlock_fs;
}
/* Ok, now we can trust subsys/s_item */
spin_lock(&configfs_dirent_lock);
/* Scan the tree, return 0 if found */
ret = configfs_depend_prep(subsys_sd->s_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);
out_unlock_fs:
mutex_unlock(&d_inode(root)->i_mutex);
/*
* If we succeeded, the fs is pinned via other methods. If not,
* we're done with it anyway. So release_fs() is always right.
*/
configfs_release_fs();
return ret;
}
EXPORT_SYMBOL(configfs_depend_item);
/*
* Release the dependent linkage. This is much simpler than
* configfs_depend_item() because we know that that the client driver is
* pinned, thus the subsystem is pinned, and therefore configfs is pinned.
*/
void configfs_undepend_item(struct configfs_subsystem *subsys,
struct config_item *target)
{
struct configfs_dirent *sd;
/*
* Since we can trust everything is pinned, we just need
* 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);
static int configfs_mkdir(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;
struct config_item_type *type;
struct module *subsys_owner = NULL, *new_item_owner = NULL;
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;
}
/* 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);
else
ret = configfs_attach_item(parent_item, item, dentry);
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);
out:
return ret;
}
static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
{
struct config_item *parent_item;
struct config_item *item;
struct configfs_subsystem *subsys;
struct configfs_dirent *sd;
struct module *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 mutex *wait_mutex;
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_mutex);
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 */
mutex_lock(wait_mutex);
mutex_unlock(wait_mutex);
}
} while (ret == -EAGAIN);
/* 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,
};
#if 0
int configfs_rename_dir(struct config_item * item, const char *new_name)
{
int error = 0;
struct dentry * new_dentry, * parent;
if (!strcmp(config_item_name(item), new_name))
return -EINVAL;
if (!item->parent)
return -EINVAL;
down_write(&configfs_rename_sem);
parent = item->parent->dentry;
mutex_lock(&d_inode(parent)->i_mutex);
new_dentry = lookup_one_len(new_name, parent, strlen(new_name));
if (!IS_ERR(new_dentry)) {
if (d_really_is_negative(new_dentry)) {
error = config_item_set_name(item, "%s", new_name);
if (!error) {
d_add(new_dentry, NULL);
d_move(item->dentry, new_dentry);
}
else
d_delete(new_dentry);
} else
error = -EEXIST;
dput(new_dentry);
}
mutex_unlock(&d_inode(parent)->i_mutex);
up_write(&configfs_rename_sem);
return error;
}
#endif
static int configfs_dir_open(struct inode *inode, struct file *file)
{
struct dentry * dentry = file->f_path.dentry;
struct configfs_dirent * parent_sd = dentry->d_fsdata;
int err;
mutex_lock(&d_inode(dentry)->i_mutex);
/*
* 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);
if (IS_ERR(file->private_data))
err = PTR_ERR(file->private_data);
else
err = 0;
}
mutex_unlock(&d_inode(dentry)->i_mutex);
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;
mutex_lock(&d_inode(dentry)->i_mutex);
spin_lock(&configfs_dirent_lock);
list_del_init(&cursor->s_sibling);
spin_unlock(&configfs_dirent_lock);
mutex_unlock(&d_inode(dentry)->i_mutex);
release_configfs_dirent(cursor);
return 0;
}
/* Relationship between s_mode and the DT_xxx types */
static inline unsigned char dt_type(struct configfs_dirent *sd)
{
return (sd->s_mode >> 12) & 15;
}
static int configfs_readdir(struct file *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;
if (ctx->pos == 2) {
spin_lock(&configfs_dirent_lock);
list_move(q, &parent_sd->s_children);
spin_unlock(&configfs_dirent_lock);
}
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;
name = configfs_get_name(next);
len = strlen(name);
/*
* 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.
*/
spin_lock(&configfs_dirent_lock);
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);
if (!dir_emit(ctx, name, len, ino, dt_type(next)))
return 0;
spin_lock(&configfs_dirent_lock);
list_move(q, p);
spin_unlock(&configfs_dirent_lock);
p = q;
ctx->pos++;
}
return 0;
}
static loff_t configfs_dir_lseek(struct file *file, loff_t offset, int whence)
{
struct dentry * dentry = file->f_path.dentry;
mutex_lock(&d_inode(dentry)->i_mutex);
switch (whence) {
case 1:
offset += file->f_pos;
case 0:
if (offset >= 0)
break;
default:
mutex_unlock(&d_inode(dentry)->i_mutex);
return -EINVAL;
}
if (offset != file->f_pos) {
file->f_pos = offset;
if (file->f_pos >= 2) {
struct configfs_dirent *sd = dentry->d_fsdata;
struct configfs_dirent *cursor = file->private_data;
struct list_head *p;
loff_t n = file->f_pos - 2;
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);
}
}
mutex_unlock(&d_inode(dentry)->i_mutex);
return offset;
}
const struct file_operations configfs_dir_operations = {
.open = configfs_dir_open,
.release = configfs_dir_close,
.llseek = configfs_dir_lseek,
.read = generic_read_dir,
.iterate = configfs_readdir,
};
/**
* configfs_register_group - creates a parent-child relation between two groups
* _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;
int ret;
mutex_lock(&subsys->su_mutex);
link_group(parent_group, group);
mutex_unlock(&subsys->su_mutex);
parent = parent_group->cg_item.ci_dentry;
mutex_lock_nested(&d_inode(parent)->i_mutex, I_MUTEX_PARENT);
ret = create_default_group(parent_group, group);
if (!ret) {
spin_lock(&configfs_dirent_lock);
configfs_dir_set_ready(group->cg_item.ci_dentry->d_fsdata);
spin_unlock(&configfs_dirent_lock);
}
mutex_unlock(&d_inode(parent)->i_mutex);
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;
mutex_lock_nested(&d_inode(parent)->i_mutex, 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_delete(dentry);
mutex_unlock(&d_inode(parent)->i_mutex);
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
* _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,
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;
root = configfs_pin_fs();
if (IS_ERR(root))
return PTR_ERR(root);
if (!group->cg_item.ci_name)
group->cg_item.ci_name = group->cg_item.ci_namebuf;
sd = root->d_fsdata;
link_group(to_config_group(sd->s_element), group);
mutex_lock_nested(&d_inode(root)->i_mutex, 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);
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);
}
}
mutex_unlock(&d_inode(root)->i_mutex);
if (err) {
unlink_group(group);
configfs_release_fs();
}
return err;
}
void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
{
struct config_group *group = &subsys->su_group;
struct dentry *dentry = group->cg_item.ci_dentry;
struct dentry *root = dentry->d_sb->s_root;
if (dentry->d_parent != root) {
pr_err("Tried to unregister non-subsystem!\n");
return;
}
mutex_lock_nested(&d_inode(root)->i_mutex,
I_MUTEX_PARENT);
mutex_lock_nested(&d_inode(dentry)->i_mutex, 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);
mutex_unlock(&d_inode(dentry)->i_mutex);
d_delete(dentry);
mutex_unlock(&d_inode(root)->i_mutex);
dput(dentry);
unlink_group(group);
configfs_release_fs();
}
EXPORT_SYMBOL(configfs_register_subsystem);
EXPORT_SYMBOL(configfs_unregister_subsystem);