// SPDX-License-Identifier: GPL-2.0-or-later /* -*- mode: c; c-basic-offset: 8; -*- * vim: noexpandtab sw=8 ts=8 sts=0: * * 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); 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_attach_attr 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. * * Note: user-created entries won't be allowed under this new directory * until it is validated by configfs_dir_set_ready() */ static int configfs_create_dir(struct config_item *item, struct dentry *dentry, struct configfs_fragment *frag) { int error; umode_t mode = S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO; struct dentry *p = dentry->d_parent; struct inode *inode; BUG_ON(!item); error = configfs_dirent_exists(p->d_fsdata, dentry->d_name.name); if (unlikely(error)) return error; error = configfs_make_dirent(p->d_fsdata, dentry, item, mode, CONFIGFS_DIR | CONFIGFS_USET_CREATING, frag); if (unlikely(error)) return error; configfs_set_dir_dirent_depth(p->d_fsdata, dentry->d_fsdata); inode = configfs_create(dentry, mode); if (IS_ERR(inode)) goto out_remove; inode->i_op = &configfs_dir_inode_operations; inode->i_fop = &configfs_dir_operations; /* directory inodes start off with i_nlink == 2 (for "." entry) */ inc_nlink(inode); d_instantiate(dentry, inode); /* already hashed */ dget(dentry); /* pin directory dentries in core */ inc_nlink(d_inode(p)); item->ci_dentry = dentry; return 0; out_remove: configfs_remove_dirent(dentry); return PTR_ERR(inode); } /* * Allow userspace to create new entries under a new directory created with * configfs_create_dir(), and under all of its chidlren directories recursively. * @sd configfs_dirent of the new directory to validate * * Caller must hold configfs_dirent_lock. */ static void configfs_dir_set_ready(struct configfs_dirent *sd) { struct configfs_dirent *child_sd; sd->s_type &= ~CONFIGFS_USET_CREATING; list_for_each_entry(child_sd, &sd->s_children, s_sibling) if (child_sd->s_type & CONFIGFS_USET_CREATING) configfs_dir_set_ready(child_sd); } /* * Check that a directory does not belong to a directory hierarchy being * attached and not validated yet. * @sd configfs_dirent of the directory to check * * @return non-zero iff the directory was validated * * Note: takes configfs_dirent_lock, so the result may change from false to true * in two consecutive calls, but never from true to false. */ int configfs_dirent_is_ready(struct configfs_dirent *sd) { int ret; spin_lock(&configfs_dirent_lock); ret = !(sd->s_type & CONFIGFS_USET_CREATING); spin_unlock(&configfs_dirent_lock); return ret; } int configfs_create_link(struct configfs_dirent *target, struct dentry *parent, struct dentry *dentry, char *body) { int err = 0; umode_t mode = S_IFLNK | S_IRWXUGO; struct configfs_dirent *p = parent->d_fsdata; struct inode *inode; err = configfs_make_dirent(p, dentry, target, mode, CONFIGFS_ITEM_LINK, p->s_frag); if (err) return err; inode = configfs_create(dentry, mode); if (IS_ERR(inode)) goto out_remove; inode->i_link = body; inode->i_op = &configfs_symlink_inode_operations; d_instantiate(dentry, inode); dget(dentry); /* pin link dentries in core */ return 0; out_remove: configfs_remove_dirent(dentry); return PTR_ERR(inode); } static void remove_dir(struct dentry * d) { struct dentry * parent = dget(d->d_parent); configfs_remove_dirent(d); if (d_really_is_positive(d)) simple_rmdir(d_inode(parent),d); pr_debug(" o %pd removing done (%d)\n", d, d_count(d)); dput(parent); } /** * configfs_remove_dir - remove an config_item's directory. * @item: config_item we're removing. * * The only thing special about this is that we remove any files in * the directory before we remove the directory, and we've inlined * what used to be configfs_rmdir() below, instead of calling separately. * * Caller holds the mutex of the item's inode */ static void configfs_remove_dir(struct config_item * item) { struct dentry * dentry = dget(item->ci_dentry); if (!dentry) return; remove_dir(dentry); /** * Drop reference from dget() on entrance. */ dput(dentry); } /* 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; struct inode *inode; spin_lock(&configfs_dirent_lock); dentry->d_fsdata = configfs_get(sd); sd->s_dentry = dentry; spin_unlock(&configfs_dirent_lock); inode = configfs_create(dentry, (attr->ca_mode & S_IALLUGO) | S_IFREG); if (IS_ERR(inode)) { configfs_put(sd); return PTR_ERR(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; } d_add(dentry, inode); 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 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 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 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); return -EINTR; } frag->frag_dead = true; up_write(&frag->frag_sem); /* Get a working ref for the duration of this function */ item = configfs_get_config_item(dentry); /* Drop reference from above, item already holds one. */ config_item_put(parent_item); if (item->ci_type) dead_item_owner = item->ci_type->ct_owner; if (sd->s_type & CONFIGFS_USET_DIR) { configfs_detach_group(item); mutex_lock(&subsys->su_mutex); client_disconnect_notify(parent_item, item); unlink_group(to_config_group(item)); } else { configfs_detach_item(item); mutex_lock(&subsys->su_mutex); client_disconnect_notify(parent_item, item); unlink_obj(item); } client_drop_item(parent_item, item); mutex_unlock(&subsys->su_mutex); /* Drop our reference from above */ config_item_put(item); module_put(dead_item_owner); module_put(subsys_owner); return 0; } const struct inode_operations configfs_dir_inode_operations = { .mkdir = configfs_mkdir, .rmdir = configfs_rmdir, .symlink = configfs_symlink, .unlink = configfs_unlink, .lookup = configfs_lookup, .setattr = configfs_setattr, }; const struct inode_operations configfs_root_inode_operations = { .lookup = configfs_lookup, .setattr = configfs_setattr, }; static int configfs_dir_open(struct inode *inode, struct file *file) { struct dentry * dentry = file->f_path.dentry; struct configfs_dirent * parent_sd = dentry->d_fsdata; int err; inode_lock(d_inode(dentry)); /* * Fake invisibility if dir belongs to a group/default groups hierarchy * being attached */ err = -ENOENT; if (configfs_dirent_is_ready(parent_sd)) { file->private_data = configfs_new_dirent(parent_sd, NULL, 0, NULL); if (IS_ERR(file->private_data)) err = PTR_ERR(file->private_data); else err = 0; } inode_unlock(d_inode(dentry)); return err; } static int configfs_dir_close(struct inode *inode, struct file *file) { struct dentry * dentry = file->f_path.dentry; struct configfs_dirent * cursor = file->private_data; inode_lock(d_inode(dentry)); spin_lock(&configfs_dirent_lock); list_del_init(&cursor->s_sibling); spin_unlock(&configfs_dirent_lock); inode_unlock(d_inode(dentry)); release_configfs_dirent(cursor); return 0; } /* Relationship between s_mode and the DT_xxx types */ static inline unsigned char dt_type(struct configfs_dirent *sd) { return (sd->s_mode >> 12) & 15; } static int configfs_readdir(struct file *file, struct dir_context *ctx) { struct dentry *dentry = file->f_path.dentry; struct super_block *sb = dentry->d_sb; struct configfs_dirent * parent_sd = dentry->d_fsdata; struct configfs_dirent *cursor = file->private_data; struct list_head *p, *q = &cursor->s_sibling; ino_t ino = 0; if (!dir_emit_dots(file, ctx)) return 0; spin_lock(&configfs_dirent_lock); if (ctx->pos == 2) list_move(q, &parent_sd->s_children); for (p = q->next; p != &parent_sd->s_children; p = p->next) { struct configfs_dirent *next; const char *name; int len; struct inode *inode = NULL; next = list_entry(p, struct configfs_dirent, s_sibling); if (!next->s_element) continue; /* * We'll have a dentry and an inode for * PINNED items and for open attribute * files. We lock here to prevent a race * with configfs_d_iput() clearing * s_dentry before calling iput(). * * Why do we go to the trouble? If * someone has an attribute file open, * the inode number should match until * they close it. Beyond that, we don't * care. */ dentry = next->s_dentry; if (dentry) inode = d_inode(dentry); if (inode) ino = inode->i_ino; spin_unlock(&configfs_dirent_lock); if (!inode) ino = iunique(sb, 2); name = configfs_get_name(next); len = strlen(name); if (!dir_emit(ctx, name, len, ino, dt_type(next))) return 0; spin_lock(&configfs_dirent_lock); list_move(q, p); p = q; ctx->pos++; } spin_unlock(&configfs_dirent_lock); return 0; } static loff_t configfs_dir_lseek(struct file *file, loff_t offset, int whence) { struct dentry * dentry = file->f_path.dentry; switch (whence) { case 1: offset += file->f_pos; /* fall through */ case 0: if (offset >= 0) break; /* fall through */ 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); fsnotify_rmdir(d_inode(parent), dentry); d_delete(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; link_group(to_config_group(sd->s_element), group); 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) { unlink_group(group); 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); fsnotify_rmdir(d_inode(root), dentry); inode_unlock(d_inode(dentry)); d_delete(dentry); inode_unlock(d_inode(root)); dput(dentry); unlink_group(group); configfs_release_fs(); } EXPORT_SYMBOL(configfs_register_subsystem); EXPORT_SYMBOL(configfs_unregister_subsystem);