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dir.c
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/* -*- 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) {
BUG_ON(sd->s_dentry != dentry);
sd->s_dentry = NULL;
configfs_put(sd);
}
iput(inode);
}
/*
* We _must_ delete our dentries on last dput, as the chain-to-parent
* behavior is required to clear the parents of default_groups.
*/
static int configfs_d_delete(struct dentry *dentry)
{
return 1;
}
static struct dentry_operations configfs_dentry_ops = {
.d_iput = configfs_d_iput,
/* simple_delete_dentry() isn't exported */
.d_delete = configfs_d_delete,
};
/*
* Allocates a new configfs_dirent and links it to the parent configfs_dirent
*/
static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent * parent_sd,
void * element)
{
struct configfs_dirent * sd;
sd = kmem_cache_zalloc(configfs_dir_cachep, GFP_KERNEL);
if (!sd)
return 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;
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);
if (IS_ERR(sd))
return PTR_ERR(sd);
sd->s_mode = mode;
sd->s_type = type;
sd->s_dentry = dentry;
if (dentry) {
dentry->d_fsdata = configfs_get(sd);
dentry->d_op = &configfs_dentry_ops;
}
return 0;
}
static int init_dir(struct inode * inode)
{
inode->i_op = &configfs_dir_inode_operations;
inode->i_fop = &configfs_dir_operations;
/* directory inodes start off with i_nlink == 2 (for "." entry) */
inc_nlink(inode);
return 0;
}
static int configfs_init_file(struct inode * inode)
{
inode->i_size = PAGE_SIZE;
inode->i_fop = &configfs_file_operations;
return 0;
}
static int init_symlink(struct inode * inode)
{
inode->i_op = &configfs_symlink_inode_operations;
return 0;
}
static int create_dir(struct config_item * k, struct dentry * p,
struct dentry * d)
{
int error;
umode_t mode = S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO;
error = configfs_dirent_exists(p->d_fsdata, d->d_name.name);
if (!error)
error = configfs_make_dirent(p->d_fsdata, d, k, mode,
CONFIGFS_DIR);
if (!error) {
error = configfs_create(d, mode, init_dir);
if (!error) {
inc_nlink(p->d_inode);
(d)->d_op = &configfs_dentry_ops;
} else {
struct configfs_dirent *sd = d->d_fsdata;
if (sd) {
spin_lock(&configfs_dirent_lock);
list_del_init(&sd->s_sibling);
spin_unlock(&configfs_dirent_lock);
configfs_put(sd);
}
}
}
return error;
}
/**
* configfs_create_dir - create a directory for an config_item.
* @item: config_itemwe're creating directory for.
* @dentry: config_item's dentry.
*/
static int configfs_create_dir(struct config_item * item, struct dentry *dentry)
{
struct dentry * parent;
int error = 0;
BUG_ON(!item);
if (item->ci_parent)
parent = item->ci_parent->ci_dentry;
else if (configfs_mount && configfs_mount->mnt_sb)
parent = configfs_mount->mnt_sb->s_root;
else
return -EFAULT;
error = create_dir(item,parent,dentry);
if (!error)
item->ci_dentry = dentry;
return error;
}
int configfs_create_link(struct configfs_symlink *sl,
struct dentry *parent,
struct dentry *dentry)
{
int err = 0;
umode_t mode = S_IFLNK | S_IRWXUGO;
err = configfs_make_dirent(parent->d_fsdata, dentry, sl, mode,
CONFIGFS_ITEM_LINK);
if (!err) {
err = configfs_create(dentry, mode, init_symlink);
if (!err)
dentry->d_op = &configfs_dentry_ops;
else {
struct configfs_dirent *sd = dentry->d_fsdata;
if (sd) {
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->d_inode)
simple_rmdir(parent->d_inode,d);
pr_debug(" o %s removing done (%d)\n",d->d_name.name,
atomic_read(&d->d_count));
dput(parent);
}
/**
* configfs_remove_dir - remove an config_item's directory.
* @item: config_item we're removing.
*
* The only thing special about this is that we remove any files in
* the directory before we remove the directory, and we've inlined
* what used to be configfs_rmdir() below, instead of calling separately.
*/
static void configfs_remove_dir(struct config_item * item)
{
struct dentry * dentry = dget(item->ci_dentry);
if (!dentry)
return;
remove_dir(dentry);
/**
* Drop reference from dget() on entrance.
*/
dput(dentry);
}
/* attaches attribute's configfs_dirent to the dentry corresponding to the
* attribute file
*/
static int configfs_attach_attr(struct configfs_dirent * sd, struct dentry * dentry)
{
struct configfs_attribute * attr = sd->s_element;
int error;
dentry->d_fsdata = configfs_get(sd);
sd->s_dentry = dentry;
error = configfs_create(dentry, (attr->ca_mode & S_IALLUGO) | S_IFREG,
configfs_init_file);
if (error) {
configfs_put(sd);
return error;
}
dentry->d_op = &configfs_dentry_ops;
d_rehash(dentry);
return 0;
}
static struct dentry * configfs_lookup(struct inode *dir,
struct dentry *dentry,
struct nameidata *nd)
{
struct configfs_dirent * parent_sd = dentry->d_parent->d_fsdata;
struct configfs_dirent * sd;
int found = 0;
int err = 0;
list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
if (sd->s_type & CONFIGFS_NOT_PINNED) {
const unsigned char * name = configfs_get_name(sd);
if (strcmp(name, dentry->d_name.name))
continue;
found = 1;
err = configfs_attach_attr(sd, dentry);
break;
}
}
if (!found) {
/*
* If it doesn't exist and it isn't a NOT_PINNED item,
* it must be negative.
*/
return simple_lookup(dir, dentry, nd);
}
return ERR_PTR(err);
}
/*
* Only subdirectories count here. Files (CONFIGFS_NOT_PINNED) are
* attributes and are removed by rmdir(). We recurse, 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;
ret = -EBUSY;
if (!list_empty(&parent_sd->s_links))
goto out;
ret = 0;
list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
if (sd->s_type & CONFIGFS_NOT_PINNED)
continue;
if (sd->s_type & CONFIGFS_USET_DEFAULT) {
/* Abort if racing with mkdir() */
if (sd->s_type & CONFIGFS_USET_IN_MKDIR) {
if (wait_mutex)
*wait_mutex = &sd->s_dentry->d_inode->i_mutex;
return -EAGAIN;
}
/* Mark that we're trying to drop the group */
sd->s_type |= CONFIGFS_USET_DROPPING;
/*
* Yup, recursive. If there's a problem, blame
* deep nesting of default_groups
*/
ret = configfs_detach_prep(sd->s_dentry, 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;
list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
if (sd->s_type & CONFIGFS_USET_DEFAULT) {
configfs_detach_rollback(sd->s_dentry);
sd->s_type &= ~CONFIGFS_USET_DROPPING;
}
}
}
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(&child->d_inode->i_mutex);
configfs_detach_group(sd->s_element);
child->d_inode->i_flags |= S_DEAD;
mutex_unlock(&child->d_inode->i_mutex);
d_delete(child);
dput(child);
}
/**
* Drop reference from dget() on entrance.
*/
dput(dentry);
}
/*
* This fakes mkdir(2) on a default_groups[] entry. It
* creates a dentry, attachs it, and then does fixup
* on the sd->s_type.
*
* We could, perhaps, tweak our parent's ->mkdir for a minute and
* try using vfs_mkdir. Just a thought.
*/
static int create_default_group(struct config_group *parent_group,
struct config_group *group)
{
int ret;
struct qstr name;
struct configfs_dirent *sd;
/* We trust the caller holds a reference to parent */
struct dentry *child, *parent = parent_group->cg_item.ci_dentry;
if (!group->cg_item.ci_name)
group->cg_item.ci_name = group->cg_item.ci_namebuf;
name.name = group->cg_item.ci_name;
name.len = strlen(name.name);
name.hash = full_name_hash(name.name, name.len);
ret = -ENOMEM;
child = d_alloc(parent, &name);
if (child) {
d_add(child, NULL);
ret = configfs_attach_group(&parent_group->cg_item,
&group->cg_item, child);
if (!ret) {
sd = child->d_fsdata;
sd->s_type |= CONFIGFS_USET_DEFAULT;
} else {
d_delete(child);
dput(child);
}
}
return ret;
}
static int populate_groups(struct config_group *group)
{
struct config_group *new_group;
struct dentry *dentry = group->cg_item.ci_dentry;
int ret = 0;
int i;
if (group->default_groups) {
/*
* FYI, we're faking mkdir here
* I'm not sure we need this semaphore, as we're called
* from our parent's mkdir. That holds our parent's
* i_mutex, so afaik lookup cannot continue through our
* parent to find us, let alone mess with our tree.
* That said, taking our i_mutex is closer to mkdir
* emulation, and shouldn't hurt.
*/
mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
for (i = 0; group->default_groups[i]; i++) {
new_group = group->default_groups[i];
ret = create_default_group(group, new_group);
if (ret)
break;
}
mutex_unlock(&dentry->d_inode->i_mutex);
}
if (ret)
detach_groups(group);
return ret;
}
/*
* All of link_obj/unlink_obj/link_group/unlink_group require that
* subsys->su_mutex is held.
*/
static void unlink_obj(struct config_item *item)
{
struct config_group *group;
group = item->ci_group;
if (group) {
list_del_init(&item->ci_entry);
item->ci_group = NULL;
item->ci_parent = NULL;
/* Drop the reference for ci_entry */
config_item_put(item);
/* Drop the reference for ci_parent */
config_group_put(group);
}
}
static void link_obj(struct config_item *parent_item, struct config_item *item)
{
/*
* Parent seems redundant with group, but it makes certain
* traversals much nicer.
*/
item->ci_parent = parent_item;
/*
* We hold a reference on the parent for the child's ci_parent
* link.
*/
item->ci_group = config_group_get(to_config_group(parent_item));
list_add_tail(&item->ci_entry, &item->ci_group->cg_children);
/*
* We hold a reference on the child for ci_entry on the parent's
* cg_children
*/
config_item_get(item);
}
static void unlink_group(struct config_group *group)
{
int i;
struct config_group *new_group;
if (group->default_groups) {
for (i = 0; group->default_groups[i]; i++) {
new_group = group->default_groups[i];
unlink_group(new_group);
}
}
group->cg_subsys = NULL;
unlink_obj(&group->cg_item);
}
static void link_group(struct config_group *parent_group, struct config_group *group)
{
int i;
struct config_group *new_group;
struct configfs_subsystem *subsys = NULL; /* gcc is a turd */
link_obj(&parent_group->cg_item, &group->cg_item);
if (parent_group->cg_subsys)
subsys = parent_group->cg_subsys;
else if (configfs_is_root(&parent_group->cg_item))
subsys = to_configfs_subsystem(group);
else
BUG();
group->cg_subsys = subsys;
if (group->default_groups) {
for (i = 0; group->default_groups[i]; i++) {
new_group = group->default_groups[i];
link_group(group, new_group);
}
}
}
/*
* The goal is that configfs_attach_item() (and
* configfs_attach_group()) can be called from either the VFS or this
* module. That is, they assume that the items have been created,
* the dentry allocated, and the dcache is all ready to go.
*
* If they fail, they must clean up after themselves as if they
* had never been called. The caller (VFS or local function) will
* handle cleaning up the dcache bits.
*
* configfs_detach_group() and configfs_detach_item() behave similarly on
* the way out. They assume that the proper semaphores are held, they
* clean up the configfs items, and they expect their callers will
* handle the dcache bits.
*/
static int configfs_attach_item(struct config_item *parent_item,
struct config_item *item,
struct dentry *dentry)
{
int ret;
ret = configfs_create_dir(item, dentry);
if (!ret) {
ret = populate_attrs(item);
if (ret) {
configfs_remove_dir(item);
d_delete(dentry);
}
}
return ret;
}
static void configfs_detach_item(struct config_item *item)
{
detach_attrs(item);
configfs_remove_dir(item);
}
static int configfs_attach_group(struct config_item *parent_item,
struct config_item *item,
struct dentry *dentry)
{
int ret;
struct configfs_dirent *sd;
ret = configfs_attach_item(parent_item, item, dentry);
if (!ret) {
sd = dentry->d_fsdata;
sd->s_type |= CONFIGFS_USET_DIR;
ret = populate_groups(to_config_group(item));
if (ret) {
configfs_detach_item(item);
d_delete(dentry);
}
}
return ret;
}
static void configfs_detach_group(struct config_item *item)
{
detach_groups(to_config_group(item));
configfs_detach_item(item);
}
/*
* After the item has been detached from the filesystem view, we are
* ready to tear it out of the hierarchy. Notify the client before
* we do that so they can perform any cleanup that requires
* navigating the hierarchy. A client does not need to provide this
* callback. The subsystem semaphore MUST be held by the caller, and
* references must be valid for both items. It also assumes the
* caller has validated ci_type.
*/
static void client_disconnect_notify(struct config_item *parent_item,
struct config_item *item)
{
struct config_item_type *type;
type = parent_item->ci_type;
BUG_ON(!type);
if (type->ct_group_ops && type->ct_group_ops->disconnect_notify)
type->ct_group_ops->disconnect_notify(to_config_group(parent_item),
item);
}
/*
* Drop the initial reference from make_item()/make_group()
* This function assumes that reference is held on item
* and that item holds a valid reference to the parent. Also, it
* assumes the caller has validated ci_type.
*/
static void client_drop_item(struct config_item *parent_item,
struct config_item *item)
{
struct config_item_type *type;
type = parent_item->ci_type;
BUG_ON(!type);
/*
* If ->drop_item() exists, it is responsible for the
* config_item_put().
*/
if (type->ct_group_ops && type->ct_group_ops->drop_item)
type->ct_group_ops->drop_item(to_config_group(parent_item),
item);
else
config_item_put(item);
}
#ifdef DEBUG
static void configfs_dump_one(struct configfs_dirent *sd, int level)
{
printk(KERN_INFO "%*s\"%s\":\n", level, " ", configfs_get_name(sd));
#define type_print(_type) if (sd->s_type & _type) printk(KERN_INFO "%*s %s\n", level, " ", #_type);
type_print(CONFIGFS_ROOT);
type_print(CONFIGFS_DIR);
type_print(CONFIGFS_ITEM_ATTR);
type_print(CONFIGFS_ITEM_LINK);
type_print(CONFIGFS_USET_DIR);
type_print(CONFIGFS_USET_DEFAULT);
type_print(CONFIGFS_USET_DROPPING);
#undef type_print
}
static int configfs_dump(struct configfs_dirent *sd, int level)
{
struct configfs_dirent *child_sd;
int ret = 0;
configfs_dump_one(sd, level);
if (!(sd->s_type & (CONFIGFS_DIR|CONFIGFS_ROOT)))
return 0;
list_for_each_entry(child_sd, &sd->s_children, s_sibling) {
ret = configfs_dump(child_sd, level + 2);
if (ret)
break;
}
return ret;
}
#endif
/*
* configfs_depend_item() and configfs_undepend_item()
*
* WARNING: Do not call these from a configfs callback!
*
* This describes these functions and their helpers.
*
* Allow another kernel system to depend on a config_item. If this
* happens, the item cannot go away until the dependant can live without
* it. The idea is to give client modules as simple an interface as
* possible. When a system asks them to depend on an item, they just
* call configfs_depend_item(). If the item is live and the client
* driver is in good shape, we'll happily do the work for them.
*
* Why is the locking complex? Because configfs uses the VFS to handle
* all locking, but this function is called outside the normal
* VFS->configfs path. So it must take VFS locks to prevent the
* VFS->configfs stuff (configfs_mkdir(), configfs_rmdir(), etc). This is
* why you can't call these functions underneath configfs callbacks.
*
* Note, btw, that this can be called at *any* time, even when a configfs
* subsystem isn't registered, or when configfs is loading or unloading.
* Just like configfs_register_subsystem(). So we take the same
* precautions. We pin the filesystem. We lock each i_mutex _in_order_
* on our way down the tree. If we can find the target item in the
* configfs tree, it must be part of the subsystem tree as well, so we
* do not need the subsystem semaphore. Holding the i_mutex chain locks
* out mkdir() and rmdir(), who might be racing us.
*/
/*
* configfs_depend_prep()
*
* Only subdirectories count here. Files (CONFIGFS_NOT_PINNED) are
* attributes. This is similar but not the same to configfs_detach_prep().
* Note that configfs_detach_prep() expects the parent to be locked when it
* is called, but we lock the parent *inside* configfs_depend_prep(). We
* do that so we can unlock it if we find nothing.
*
* Here we do a depth-first search of the dentry hierarchy looking for
* our object. We take i_mutex on each step of the way down. IT IS
* ESSENTIAL THAT i_mutex LOCKING IS ORDERED. If we come back up a branch,
* we'll drop the i_mutex.
*
* If the target is not found, -ENOENT is bubbled up and we have released
* all locks. If the target was found, the locks will be cleared by
* configfs_depend_rollback().
*
* This adds a requirement that all config_items be unique!
*
* This is recursive because the locking traversal is tricky. There isn't
* much on the stack, though, so folks that need this function - be careful
* about your stack! Patches will be accepted to make it iterative.
*/
static int configfs_depend_prep(struct dentry *origin,
struct config_item *target)
{
struct configfs_dirent *child_sd, *sd = origin->d_fsdata;
int ret = 0;
BUG_ON(!origin || !sd);
/* Lock this guy on the way down */
mutex_lock(&sd->s_dentry->d_inode->i_mutex);
if (sd->s_element == target) /* Boo-yah */
goto out;
list_for_each_entry(child_sd, &sd->s_children, s_sibling) {
if (child_sd->s_type & CONFIGFS_DIR) {
ret = configfs_depend_prep(child_sd->s_dentry,
target);
if (!ret)
goto out; /* Child path boo-yah */
}
}
/* We looped all our children and didn't find target */
mutex_unlock(&sd->s_dentry->d_inode->i_mutex);
ret = -ENOENT;
out:
return ret;
}
/*
* This is ONLY called if configfs_depend_prep() did its job. So we can
* trust the entire path from item back up to origin.
*
* We walk backwards from item, unlocking each i_mutex. We finish by
* unlocking origin.
*/
static void configfs_depend_rollback(struct dentry *origin,
struct config_item *item)
{
struct dentry *dentry = item->ci_dentry;
while (dentry != origin) {
mutex_unlock(&dentry->d_inode->i_mutex);
dentry = dentry->d_parent;
}
mutex_unlock(&origin->d_inode->i_mutex);
}
int configfs_depend_item(struct configfs_subsystem *subsys,
struct config_item *target)
{
int ret;
struct configfs_dirent *p, *root_sd, *subsys_sd = NULL;
struct config_item *s_item = &subsys->su_group.cg_item;
/*
* Pin the configfs filesystem. This means we can safely access
* the root of the configfs filesystem.
*/
ret = configfs_pin_fs();
if (ret)
return ret;
/*
* Next, lock the root directory. We're going to check that the
* subsystem is really registered, and so we need to lock out
* configfs_[un]register_subsystem().
*/
mutex_lock(&configfs_sb->s_root->d_inode->i_mutex);
root_sd = configfs_sb->s_root->d_fsdata;
list_for_each_entry(p, &root_sd->s_children, s_sibling) {
if (p->s_type & CONFIGFS_DIR) {
if (p->s_element == s_item) {
subsys_sd = p;
break;
}
}
}
if (!subsys_sd) {
ret = -ENOENT;
goto out_unlock_fs;
}
/* Ok, now we can trust subsys/s_item */
/* Scan the tree, locking i_mutex recursively, return 0 if found */
ret = configfs_depend_prep(subsys_sd->s_dentry, target);
if (ret)
goto out_unlock_fs;
/* We hold all i_mutexes from the subsystem down to the target */
p = target->ci_dentry->d_fsdata;
p->s_dependent_count += 1;
configfs_depend_rollback(subsys_sd->s_dentry, target);
out_unlock_fs:
mutex_unlock(&configfs_sb->s_root->d_inode->i_mutex);
/*
* If we succeeded, the fs is pinned via other methods. If not,
* we're done with it anyway. So release_fs() is always right.
*/
configfs_release_fs();
return ret;
}
EXPORT_SYMBOL(configfs_depend_item);
/*
* Release the dependent linkage. This is much simpler than