diff options
Diffstat (limited to 'fs/kernfs/dir.c')
| -rw-r--r-- | fs/kernfs/dir.c | 1428 |
1 files changed, 1428 insertions, 0 deletions
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c new file mode 100644 index 00000000000..78f3403300a --- /dev/null +++ b/fs/kernfs/dir.c @@ -0,0 +1,1428 @@ +/* + * fs/kernfs/dir.c - kernfs directory implementation + * + * Copyright (c) 2001-3 Patrick Mochel + * Copyright (c) 2007 SUSE Linux Products GmbH + * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org> + * + * This file is released under the GPLv2. + */ + +#include <linux/sched.h> +#include <linux/fs.h> +#include <linux/namei.h> +#include <linux/idr.h> +#include <linux/slab.h> +#include <linux/security.h> +#include <linux/hash.h> + +#include "kernfs-internal.h" + +DEFINE_MUTEX(kernfs_mutex); +static DEFINE_SPINLOCK(kernfs_rename_lock); /* kn->parent and ->name */ +static char kernfs_pr_cont_buf[PATH_MAX]; /* protected by rename_lock */ + +#define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb) + +static bool kernfs_active(struct kernfs_node *kn) +{ + lockdep_assert_held(&kernfs_mutex); + return atomic_read(&kn->active) >= 0; +} + +static bool kernfs_lockdep(struct kernfs_node *kn) +{ +#ifdef CONFIG_DEBUG_LOCK_ALLOC + return kn->flags & KERNFS_LOCKDEP; +#else + return false; +#endif +} + +static int kernfs_name_locked(struct kernfs_node *kn, char *buf, size_t buflen) +{ + return strlcpy(buf, kn->parent ? kn->name : "/", buflen); +} + +static char * __must_check kernfs_path_locked(struct kernfs_node *kn, char *buf, + size_t buflen) +{ + char *p = buf + buflen; + int len; + + *--p = '\0'; + + do { + len = strlen(kn->name); + if (p - buf < len + 1) { + buf[0] = '\0'; + p = NULL; + break; + } + p -= len; + memcpy(p, kn->name, len); + *--p = '/'; + kn = kn->parent; + } while (kn && kn->parent); + + return p; +} + +/** + * kernfs_name - obtain the name of a given node + * @kn: kernfs_node of interest + * @buf: buffer to copy @kn's name into + * @buflen: size of @buf + * + * Copies the name of @kn into @buf of @buflen bytes. The behavior is + * similar to strlcpy(). It returns the length of @kn's name and if @buf + * isn't long enough, it's filled upto @buflen-1 and nul terminated. + * + * This function can be called from any context. + */ +int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen) +{ + unsigned long flags; + int ret; + + spin_lock_irqsave(&kernfs_rename_lock, flags); + ret = kernfs_name_locked(kn, buf, buflen); + spin_unlock_irqrestore(&kernfs_rename_lock, flags); + return ret; +} + +/** + * kernfs_path - build full path of a given node + * @kn: kernfs_node of interest + * @buf: buffer to copy @kn's name into + * @buflen: size of @buf + * + * Builds and returns the full path of @kn in @buf of @buflen bytes. The + * path is built from the end of @buf so the returned pointer usually + * doesn't match @buf. If @buf isn't long enough, @buf is nul terminated + * and %NULL is returned. + */ +char *kernfs_path(struct kernfs_node *kn, char *buf, size_t buflen) +{ + unsigned long flags; + char *p; + + spin_lock_irqsave(&kernfs_rename_lock, flags); + p = kernfs_path_locked(kn, buf, buflen); + spin_unlock_irqrestore(&kernfs_rename_lock, flags); + return p; +} +EXPORT_SYMBOL_GPL(kernfs_path); + +/** + * pr_cont_kernfs_name - pr_cont name of a kernfs_node + * @kn: kernfs_node of interest + * + * This function can be called from any context. + */ +void pr_cont_kernfs_name(struct kernfs_node *kn) +{ + unsigned long flags; + + spin_lock_irqsave(&kernfs_rename_lock, flags); + + kernfs_name_locked(kn, kernfs_pr_cont_buf, sizeof(kernfs_pr_cont_buf)); + pr_cont("%s", kernfs_pr_cont_buf); + + spin_unlock_irqrestore(&kernfs_rename_lock, flags); +} + +/** + * pr_cont_kernfs_path - pr_cont path of a kernfs_node + * @kn: kernfs_node of interest + * + * This function can be called from any context. + */ +void pr_cont_kernfs_path(struct kernfs_node *kn) +{ + unsigned long flags; + char *p; + + spin_lock_irqsave(&kernfs_rename_lock, flags); + + p = kernfs_path_locked(kn, kernfs_pr_cont_buf, + sizeof(kernfs_pr_cont_buf)); + if (p) + pr_cont("%s", p); + else + pr_cont("<name too long>"); + + spin_unlock_irqrestore(&kernfs_rename_lock, flags); +} + +/** + * kernfs_get_parent - determine the parent node and pin it + * @kn: kernfs_node of interest + * + * Determines @kn's parent, pins and returns it. This function can be + * called from any context. + */ +struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn) +{ + struct kernfs_node *parent; + unsigned long flags; + + spin_lock_irqsave(&kernfs_rename_lock, flags); + parent = kn->parent; + kernfs_get(parent); + spin_unlock_irqrestore(&kernfs_rename_lock, flags); + + return parent; +} + +/** + * kernfs_name_hash + * @name: Null terminated string to hash + * @ns: Namespace tag to hash + * + * Returns 31 bit hash of ns + name (so it fits in an off_t ) + */ +static unsigned int kernfs_name_hash(const char *name, const void *ns) +{ + unsigned long hash = init_name_hash(); + unsigned int len = strlen(name); + while (len--) + hash = partial_name_hash(*name++, hash); + hash = (end_name_hash(hash) ^ hash_ptr((void *)ns, 31)); + hash &= 0x7fffffffU; + /* Reserve hash numbers 0, 1 and INT_MAX for magic directory entries */ + if (hash < 2) + hash += 2; + if (hash >= INT_MAX) + hash = INT_MAX - 1; + return hash; +} + +static int kernfs_name_compare(unsigned int hash, const char *name, + const void *ns, const struct kernfs_node *kn) +{ + if (hash != kn->hash) + return hash - kn->hash; + if (ns != kn->ns) + return ns - kn->ns; + return strcmp(name, kn->name); +} + +static int kernfs_sd_compare(const struct kernfs_node *left, + const struct kernfs_node *right) +{ + return kernfs_name_compare(left->hash, left->name, left->ns, right); +} + +/** + * kernfs_link_sibling - link kernfs_node into sibling rbtree + * @kn: kernfs_node of interest + * + * Link @kn into its sibling rbtree which starts from + * @kn->parent->dir.children. + * + * Locking: + * mutex_lock(kernfs_mutex) + * + * RETURNS: + * 0 on susccess -EEXIST on failure. + */ +static int kernfs_link_sibling(struct kernfs_node *kn) +{ + struct rb_node **node = &kn->parent->dir.children.rb_node; + struct rb_node *parent = NULL; + + if (kernfs_type(kn) == KERNFS_DIR) + kn->parent->dir.subdirs++; + + while (*node) { + struct kernfs_node *pos; + int result; + + pos = rb_to_kn(*node); + parent = *node; + result = kernfs_sd_compare(kn, pos); + if (result < 0) + node = &pos->rb.rb_left; + else if (result > 0) + node = &pos->rb.rb_right; + else + return -EEXIST; + } + /* add new node and rebalance the tree */ + rb_link_node(&kn->rb, parent, node); + rb_insert_color(&kn->rb, &kn->parent->dir.children); + return 0; +} + +/** + * kernfs_unlink_sibling - unlink kernfs_node from sibling rbtree + * @kn: kernfs_node of interest + * + * Try to unlink @kn from its sibling rbtree which starts from + * kn->parent->dir.children. Returns %true if @kn was actually + * removed, %false if @kn wasn't on the rbtree. + * + * Locking: + * mutex_lock(kernfs_mutex) + */ +static bool kernfs_unlink_sibling(struct kernfs_node *kn) +{ + if (RB_EMPTY_NODE(&kn->rb)) + return false; + + if (kernfs_type(kn) == KERNFS_DIR) + kn->parent->dir.subdirs--; + + rb_erase(&kn->rb, &kn->parent->dir.children); + RB_CLEAR_NODE(&kn->rb); + return true; +} + +/** + * kernfs_get_active - get an active reference to kernfs_node + * @kn: kernfs_node to get an active reference to + * + * Get an active reference of @kn. This function is noop if @kn + * is NULL. + * + * RETURNS: + * Pointer to @kn on success, NULL on failure. + */ +struct kernfs_node *kernfs_get_active(struct kernfs_node *kn) +{ + if (unlikely(!kn)) + return NULL; + + if (!atomic_inc_unless_negative(&kn->active)) + return NULL; + + if (kernfs_lockdep(kn)) + rwsem_acquire_read(&kn->dep_map, 0, 1, _RET_IP_); + return kn; +} + +/** + * kernfs_put_active - put an active reference to kernfs_node + * @kn: kernfs_node to put an active reference to + * + * Put an active reference to @kn. This function is noop if @kn + * is NULL. + */ +void kernfs_put_active(struct kernfs_node *kn) +{ + struct kernfs_root *root = kernfs_root(kn); + int v; + + if (unlikely(!kn)) + return; + + if (kernfs_lockdep(kn)) + rwsem_release(&kn->dep_map, 1, _RET_IP_); + v = atomic_dec_return(&kn->active); + if (likely(v != KN_DEACTIVATED_BIAS)) + return; + + wake_up_all(&root->deactivate_waitq); +} + +/** + * kernfs_drain - drain kernfs_node + * @kn: kernfs_node to drain + * + * Drain existing usages and nuke all existing mmaps of @kn. Mutiple + * removers may invoke this function concurrently on @kn and all will + * return after draining is complete. + */ +static void kernfs_drain(struct kernfs_node *kn) + __releases(&kernfs_mutex) __acquires(&kernfs_mutex) +{ + struct kernfs_root *root = kernfs_root(kn); + + lockdep_assert_held(&kernfs_mutex); + WARN_ON_ONCE(kernfs_active(kn)); + + mutex_unlock(&kernfs_mutex); + + if (kernfs_lockdep(kn)) { + rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_); + if (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS) + lock_contended(&kn->dep_map, _RET_IP_); + } + + /* but everyone should wait for draining */ + wait_event(root->deactivate_waitq, + atomic_read(&kn->active) == KN_DEACTIVATED_BIAS); + + if (kernfs_lockdep(kn)) { + lock_acquired(&kn->dep_map, _RET_IP_); + rwsem_release(&kn->dep_map, 1, _RET_IP_); + } + + kernfs_unmap_bin_file(kn); + + mutex_lock(&kernfs_mutex); +} + +/** + * kernfs_get - get a reference count on a kernfs_node + * @kn: the target kernfs_node + */ +void kernfs_get(struct kernfs_node *kn) +{ + if (kn) { + WARN_ON(!atomic_read(&kn->count)); + atomic_inc(&kn->count); + } +} +EXPORT_SYMBOL_GPL(kernfs_get); + +/** + * kernfs_put - put a reference count on a kernfs_node + * @kn: the target kernfs_node + * + * Put a reference count of @kn and destroy it if it reached zero. + */ +void kernfs_put(struct kernfs_node *kn) +{ + struct kernfs_node *parent; + struct kernfs_root *root; + + if (!kn || !atomic_dec_and_test(&kn->count)) + return; + root = kernfs_root(kn); + repeat: + /* + * Moving/renaming is always done while holding reference. + * kn->parent won't change beneath us. + */ + parent = kn->parent; + + WARN_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS, + "kernfs_put: %s/%s: released with incorrect active_ref %d\n", + parent ? parent->name : "", kn->name, atomic_read(&kn->active)); + + if (kernfs_type(kn) == KERNFS_LINK) + kernfs_put(kn->symlink.target_kn); + if (!(kn->flags & KERNFS_STATIC_NAME)) + kfree(kn->name); + if (kn->iattr) { + if (kn->iattr->ia_secdata) + security_release_secctx(kn->iattr->ia_secdata, + kn->iattr->ia_secdata_len); + simple_xattrs_free(&kn->iattr->xattrs); + } + kfree(kn->iattr); + ida_simple_remove(&root->ino_ida, kn->ino); + kmem_cache_free(kernfs_node_cache, kn); + + kn = parent; + if (kn) { + if (atomic_dec_and_test(&kn->count)) + goto repeat; + } else { + /* just released the root kn, free @root too */ + ida_destroy(&root->ino_ida); + kfree(root); + } +} +EXPORT_SYMBOL_GPL(kernfs_put); + +static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags) +{ + struct kernfs_node *kn; + + if (flags & LOOKUP_RCU) + return -ECHILD; + + /* Always perform fresh lookup for negatives */ + if (!dentry->d_inode) + goto out_bad_unlocked; + + kn = dentry->d_fsdata; + mutex_lock(&kernfs_mutex); + + /* The kernfs node has been deactivated */ + if (!kernfs_active(kn)) + goto out_bad; + + /* The kernfs node has been moved? */ + if (dentry->d_parent->d_fsdata != kn->parent) + goto out_bad; + + /* The kernfs node has been renamed */ + if (strcmp(dentry->d_name.name, kn->name) != 0) + goto out_bad; + + /* The kernfs node has been moved to a different namespace */ + if (kn->parent && kernfs_ns_enabled(kn->parent) && + kernfs_info(dentry->d_sb)->ns != kn->ns) + goto out_bad; + + mutex_unlock(&kernfs_mutex); +out_valid: + return 1; +out_bad: + mutex_unlock(&kernfs_mutex); +out_bad_unlocked: + /* + * @dentry doesn't match the underlying kernfs node, drop the + * dentry and force lookup. If we have submounts we must allow the + * vfs caches to lie about the state of the filesystem to prevent + * leaks and other nasty things, so use check_submounts_and_drop() + * instead of d_drop(). + */ + if (check_submounts_and_drop(dentry) != 0) + goto out_valid; + + return 0; +} + +static void kernfs_dop_release(struct dentry *dentry) +{ + kernfs_put(dentry->d_fsdata); +} + +const struct dentry_operations kernfs_dops = { + .d_revalidate = kernfs_dop_revalidate, + .d_release = kernfs_dop_release, +}; + +/** + * kernfs_node_from_dentry - determine kernfs_node associated with a dentry + * @dentry: the dentry in question + * + * Return the kernfs_node associated with @dentry. If @dentry is not a + * kernfs one, %NULL is returned. + * + * While the returned kernfs_node will stay accessible as long as @dentry + * is accessible, the returned node can be in any state and the caller is + * fully responsible for determining what's accessible. + */ +struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry) +{ + if (dentry->d_sb->s_op == &kernfs_sops) + return dentry->d_fsdata; + return NULL; +} + +static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root, + const char *name, umode_t mode, + unsigned flags) +{ + char *dup_name = NULL; + struct kernfs_node *kn; + int ret; + + if (!(flags & KERNFS_STATIC_NAME)) { + name = dup_name = kstrdup(name, GFP_KERNEL); + if (!name) + return NULL; + } + + kn = kmem_cache_zalloc(kernfs_node_cache, GFP_KERNEL); + if (!kn) + goto err_out1; + + ret = ida_simple_get(&root->ino_ida, 1, 0, GFP_KERNEL); + if (ret < 0) + goto err_out2; + kn->ino = ret; + + atomic_set(&kn->count, 1); + atomic_set(&kn->active, KN_DEACTIVATED_BIAS); + RB_CLEAR_NODE(&kn->rb); + + kn->name = name; + kn->mode = mode; + kn->flags = flags; + + return kn; + + err_out2: + kmem_cache_free(kernfs_node_cache, kn); + err_out1: + kfree(dup_name); + return NULL; +} + +struct kernfs_node *kernfs_new_node(struct kernfs_node *parent, + const char *name, umode_t mode, + unsigned flags) +{ + struct kernfs_node *kn; + + kn = __kernfs_new_node(kernfs_root(parent), name, mode, flags); + if (kn) { + kernfs_get(parent); + kn->parent = parent; + } + return kn; +} + +/** + * kernfs_add_one - add kernfs_node to parent without warning + * @kn: kernfs_node to be added + * + * The caller must already have initialized @kn->parent. This + * function increments nlink of the parent's inode if @kn is a + * directory and link into the children list of the parent. + * + * RETURNS: + * 0 on success, -EEXIST if entry with the given name already + * exists. + */ +int kernfs_add_one(struct kernfs_node *kn) +{ + struct kernfs_node *parent = kn->parent; + struct kernfs_iattrs *ps_iattr; + bool has_ns; + int ret; + + mutex_lock(&kernfs_mutex); + + ret = -EINVAL; + has_ns = kernfs_ns_enabled(parent); + if (WARN(has_ns != (bool)kn->ns, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n", + has_ns ? "required" : "invalid", parent->name, kn->name)) + goto out_unlock; + + if (kernfs_type(parent) != KERNFS_DIR) + goto out_unlock; + + ret = -ENOENT; + if ((parent->flags & KERNFS_ACTIVATED) && !kernfs_active(parent)) + goto out_unlock; + + kn->hash = kernfs_name_hash(kn->name, kn->ns); + + ret = kernfs_link_sibling(kn); + if (ret) + goto out_unlock; + + /* Update timestamps on the parent */ + ps_iattr = parent->iattr; + if (ps_iattr) { + struct iattr *ps_iattrs = &ps_iattr->ia_iattr; + ps_iattrs->ia_ctime = ps_iattrs->ia_mtime = CURRENT_TIME; + } + + mutex_unlock(&kernfs_mutex); + + /* + * Activate the new node unless CREATE_DEACTIVATED is requested. + * If not activated here, the kernfs user is responsible for + * activating the node with kernfs_activate(). A node which hasn't + * been activated is not visible to userland and its removal won't + * trigger deactivation. + */ + if (!(kernfs_root(kn)->flags & KERNFS_ROOT_CREATE_DEACTIVATED)) + kernfs_activate(kn); + return 0; + +out_unlock: + mutex_unlock(&kernfs_mutex); + return ret; +} + +/** + * kernfs_find_ns - find kernfs_node with the given name + * @parent: kernfs_node to search under + * @name: name to look for + * @ns: the namespace tag to use + * + * Look for kernfs_node with name @name under @parent. Returns pointer to + * the found kernfs_node on success, %NULL on failure. + */ +static struct kernfs_node *kernfs_find_ns(struct kernfs_node *parent, + const unsigned char *name, + const void *ns) +{ + struct rb_node *node = parent->dir.children.rb_node; + bool has_ns = kernfs_ns_enabled(parent); + unsigned int hash; + + lockdep_assert_held(&kernfs_mutex); + + if (has_ns != (bool)ns) { + WARN(1, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n", + has_ns ? "required" : "invalid", parent->name, name); + return NULL; + } + + hash = kernfs_name_hash(name, ns); + while (node) { + struct kernfs_node *kn; + int result; + + kn = rb_to_kn(node); + result = kernfs_name_compare(hash, name, ns, kn); + if (result < 0) + node = node->rb_left; + else if (result > 0) + node = node->rb_right; + else + return kn; + } + return NULL; +} + +/** + * kernfs_find_and_get_ns - find and get kernfs_node with the given name + * @parent: kernfs_node to search under + * @name: name to look for + * @ns: the namespace tag to use + * + * Look for kernfs_node with name @name under @parent and get a reference + * if found. This function may sleep and returns pointer to the found + * kernfs_node on success, %NULL on failure. + */ +struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent, + const char *name, const void *ns) +{ + struct kernfs_node *kn; + + mutex_lock(&kernfs_mutex); + kn = kernfs_find_ns(parent, name, ns); + kernfs_get(kn); + mutex_unlock(&kernfs_mutex); + + return kn; +} +EXPORT_SYMBOL_GPL(kernfs_find_and_get_ns); + +/** + * kernfs_create_root - create a new kernfs hierarchy + * @scops: optional syscall operations for the hierarchy + * @flags: KERNFS_ROOT_* flags + * @priv: opaque data associated with the new directory + * + * Returns the root of the new hierarchy on success, ERR_PTR() value on + * failure. + */ +struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops, + unsigned int flags, void *priv) +{ + struct kernfs_root *root; + struct kernfs_node *kn; + + root = kzalloc(sizeof(*root), GFP_KERNEL); + if (!root) + return ERR_PTR(-ENOMEM); + + ida_init(&root->ino_ida); + + kn = __kernfs_new_node(root, "", S_IFDIR | S_IRUGO | S_IXUGO, + KERNFS_DIR); + if (!kn) { + ida_destroy(&root->ino_ida); + kfree(root); + return ERR_PTR(-ENOMEM); + } + + kn->priv = priv; + kn->dir.root = root; + + root->syscall_ops = scops; + root->flags = flags; + root->kn = kn; + init_waitqueue_head(&root->deactivate_waitq); + + if (!(root->flags & KERNFS_ROOT_CREATE_DEACTIVATED)) + kernfs_activate(kn); + + return root; +} + +/** + * kernfs_destroy_root - destroy a kernfs hierarchy + * @root: root of the hierarchy to destroy + * + * Destroy the hierarchy anchored at @root by removing all existing + * directories and destroying @root. + */ +void kernfs_destroy_root(struct kernfs_root *root) +{ + kernfs_remove(root->kn); /* will also free @root */ +} + +/** + * kernfs_create_dir_ns - create a directory + * @parent: parent in which to create a new directory + * @name: name of the new directory + * @mode: mode of the new directory + * @priv: opaque data associated with the new directory + * @ns: optional namespace tag of the directory + * + * Returns the created node on success, ERR_PTR() value on failure. + */ +struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent, + const char *name, umode_t mode, + void *priv, const void *ns) +{ + struct kernfs_node *kn; + int rc; + + /* allocate */ + kn = kernfs_new_node(parent, name, mode | S_IFDIR, KERNFS_DIR); + if (!kn) + return ERR_PTR(-ENOMEM); + + kn->dir.root = parent->dir.root; + kn->ns = ns; + kn->priv = priv; + + /* link in */ + rc = kernfs_add_one(kn); + if (!rc) + return kn; + + kernfs_put(kn); + return ERR_PTR(rc); +} + +static struct dentry *kernfs_iop_lookup(struct inode *dir, + struct dentry *dentry, + unsigned int flags) +{ + struct dentry *ret; + struct kernfs_node *parent = dentry->d_parent->d_fsdata; + struct kernfs_node *kn; + struct inode *inode; + const void *ns = NULL; + + mutex_lock(&kernfs_mutex); + + if (kernfs_ns_enabled(parent)) + ns = kernfs_info(dir->i_sb)->ns; + + kn = kernfs_find_ns(parent, dentry->d_name.name, ns); + + /* no such entry */ + if (!kn || !kernfs_active(kn)) { + ret = NULL; + goto out_unlock; + } + kernfs_get(kn); + dentry->d_fsdata = kn; + + /* attach dentry and inode */ + inode = kernfs_get_inode(dir->i_sb, kn); + if (!inode) { + ret = ERR_PTR(-ENOMEM); + goto out_unlock; + } + + /* instantiate and hash dentry */ + ret = d_materialise_unique(dentry, inode); + out_unlock: + mutex_unlock(&kernfs_mutex); + return ret; +} + +static int kernfs_iop_mkdir(struct inode *dir, struct dentry *dentry, + umode_t mode) +{ + struct kernfs_node *parent = dir->i_private; + struct kernfs_syscall_ops *scops = kernfs_root(parent)->syscall_ops; + int ret; + + if (!scops || !scops->mkdir) + return -EPERM; + + if (!kernfs_get_active(parent)) + return -ENODEV; + + ret = scops->mkdir(parent, dentry->d_name.name, mode); + + kernfs_put_active(parent); + return ret; +} + +static int kernfs_iop_rmdir(struct inode *dir, struct dentry *dentry) +{ + struct kernfs_node *kn = dentry->d_fsdata; + struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops; + int ret; + + if (!scops || !scops->rmdir) + return -EPERM; + + if (!kernfs_get_active(kn)) + return -ENODEV; + + ret = scops->rmdir(kn); + + kernfs_put_active(kn); + return ret; +} + +static int kernfs_iop_rename(struct inode *old_dir, struct dentry *old_dentry, + struct inode *new_dir, struct dentry *new_dentry) +{ + struct kernfs_node *kn = old_dentry->d_fsdata; + struct kernfs_node *new_parent = new_dir->i_private; + struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops; + int ret; + + if (!scops || !scops->rename) + return -EPERM; + + if (!kernfs_get_active(kn)) + return -ENODEV; + + if (!kernfs_get_active(new_parent)) { + kernfs_put_active(kn); + return -ENODEV; + } + + ret = scops->rename(kn, new_parent, new_dentry->d_name.name); + + kernfs_put_active(new_parent); + kernfs_put_active(kn); + return ret; +} + +const struct inode_operations kernfs_dir_iops = { + .lookup = kernfs_iop_lookup, + .permission = kernfs_iop_permission, + .setattr = kernfs_iop_setattr, + .getattr = kernfs_iop_getattr, + .setxattr = kernfs_iop_setxattr, + .removexattr = kernfs_iop_removexattr, + .getxattr = kernfs_iop_getxattr, + .listxattr = kernfs_iop_listxattr, + + .mkdir = kernfs_iop_mkdir, + .rmdir = kernfs_iop_rmdir, + .rename = kernfs_iop_rename, +}; + +static struct kernfs_node *kernfs_leftmost_descendant(struct kernfs_node *pos) +{ + struct kernfs_node *last; + + while (true) { + struct rb_node *rbn; + + last = pos; + + if (kernfs_type(pos) != KERNFS_DIR) + break; + + rbn = rb_first(&pos->dir.children); + if (!rbn) + break; + + pos = rb_to_kn(rbn); + } + + return last; +} + +/** + * kernfs_next_descendant_post - find the next descendant for post-order walk + * @pos: the current position (%NULL to initiate traversal) + * @root: kernfs_node whose descendants to walk + * + * Find the next descendant to visit for post-order traversal of @root's + * descendants. @root is included in the iteration and the last node to be + * visited. + */ +static struct kernfs_node *kernfs_next_descendant_post(struct kernfs_node *pos, + struct kernfs_node *root) +{ + struct rb_node *rbn; + + lockdep_assert_held(&kernfs_mutex); + + /* if first iteration, visit leftmost descendant which may be root */ + if (!pos) + return kernfs_leftmost_descendant(root); + + /* if we visited @root, we're done */ + if (pos == root) + return NULL; + + /* if there's an unvisited sibling, visit its leftmost descendant */ + rbn = rb_next(&pos->rb); + if (rbn) + return kernfs_leftmost_descendant(rb_to_kn(rbn)); + + /* no sibling left, visit parent */ + return pos->parent; +} + +/** + * kernfs_activate - activate a node which started deactivated + * @kn: kernfs_node whose subtree is to be activated + * + * If the root has KERNFS_ROOT_CREATE_DEACTIVATED set, a newly created node + * needs to be explicitly activated. A node which hasn't been activated + * isn't visible to userland and deactivation is skipped during its + * removal. This is useful to construct atomic init sequences where + * creation of multiple nodes should either succeed or fail atomically. + * + * The caller is responsible for ensuring that this function is not called + * after kernfs_remove*() is invoked on @kn. + */ +void kernfs_activate(struct kernfs_node *kn) +{ + struct kernfs_node *pos; + + mutex_lock(&kernfs_mutex); + + pos = NULL; + while ((pos = kernfs_next_descendant_post(pos, kn))) { + if (!pos || (pos->flags & KERNFS_ACTIVATED)) + continue; + + WARN_ON_ONCE(pos->parent && RB_EMPTY_NODE(&pos->rb)); + WARN_ON_ONCE(atomic_read(&pos->active) != KN_DEACTIVATED_BIAS); + + atomic_sub(KN_DEACTIVATED_BIAS, &pos->active); + pos->flags |= KERNFS_ACTIVATED; + } + + mutex_unlock(&kernfs_mutex); +} + +static void __kernfs_remove(struct kernfs_node *kn) +{ + struct kernfs_node *pos; + + lockdep_assert_held(&kernfs_mutex); + + /* + * Short-circuit if non-root @kn has already finished removal. + * This is for kernfs_remove_self() which plays with active ref + * after removal. + */ + if (!kn || (kn->parent && RB_EMPTY_NODE(&kn->rb))) + return; + + pr_debug("kernfs %s: removing\n", kn->name); + + /* prevent any new usage under @kn by deactivating all nodes */ + pos = NULL; + while ((pos = kernfs_next_descendant_post(pos, kn))) + if (kernfs_active(pos)) + atomic_add(KN_DEACTIVATED_BIAS, &pos->active); + + /* deactivate and unlink the subtree node-by-node */ + do { + pos = kernfs_leftmost_descendant(kn); + + /* + * kernfs_drain() drops kernfs_mutex temporarily and @pos's + * base ref could have been put by someone else by the time + * the function returns. Make sure it doesn't go away + * underneath us. + */ + kernfs_get(pos); + + /* + * Drain iff @kn was activated. This avoids draining and + * its lockdep annotations for nodes which have never been + * activated and allows embedding kernfs_remove() in create + * error paths without worrying about draining. + */ + if (kn->flags & KERNFS_ACTIVATED) + kernfs_drain(pos); + else + WARN_ON_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS); + + /* + * kernfs_unlink_sibling() succeeds once per node. Use it + * to decide who's responsible for cleanups. + */ + if (!pos->parent || kernfs_unlink_sibling(pos)) { + struct kernfs_iattrs *ps_iattr = + pos->parent ? pos->parent->iattr : NULL; + + /* update timestamps on the parent */ + if (ps_iattr) { + ps_iattr->ia_iattr.ia_ctime = CURRENT_TIME; + ps_iattr->ia_iattr.ia_mtime = CURRENT_TIME; + } + + kernfs_put(pos); + } + + kernfs_put(pos); + } while (pos != kn); +} + +/** + * kernfs_remove - remove a kernfs_node recursively + * @kn: the kernfs_node to remove + * + * Remove @kn along with all its subdirectories and files. + */ +void kernfs_remove(struct kernfs_node *kn) +{ + mutex_lock(&kernfs_mutex); + __kernfs_remove(kn); + mutex_unlock(&kernfs_mutex); +} + +/** + * kernfs_break_active_protection - break out of active protection + * @kn: the self kernfs_node + * + * The caller must be running off of a kernfs operation which is invoked + * with an active reference - e.g. one of kernfs_ops. Each invocation of + * this function must also be matched with an invocation of + * kernfs_unbreak_active_protection(). + * + * This function releases the active reference of @kn the caller is + * holding. Once this function is called, @kn may be removed at any point + * and the caller is solely responsible for ensuring that the objects it + * dereferences are accessible. + */ +void kernfs_break_active_protection(struct kernfs_node *kn) +{ + /* + * Take out ourself out of the active ref dependency chain. If + * we're called without an active ref, lockdep will complain. + */ + kernfs_put_active(kn); +} + +/** + * kernfs_unbreak_active_protection - undo kernfs_break_active_protection() + * @kn: the self kernfs_node + * + * If kernfs_break_active_protection() was called, this function must be + * invoked before finishing the kernfs operation. Note that while this + * function restores the active reference, it doesn't and can't actually + * restore the active protection - @kn may already or be in the process of + * being removed. Once kernfs_break_active_protection() is invoked, that + * protection is irreversibly gone for the kernfs operation instance. + * + * While this function may be called at any point after + * kernfs_break_active_protection() is invoked, its most useful location + * would be right before the enclosing kernfs operation returns. + */ +void kernfs_unbreak_active_protection(struct kernfs_node *kn) +{ + /* + * @kn->active could be in any state; however, the increment we do + * here will be undone as soon as the enclosing kernfs operation + * finishes and this temporary bump can't break anything. If @kn + * is alive, nothing changes. If @kn is being deactivated, the + * soon-to-follow put will either finish deactivation or restore + * deactivated state. If @kn is already removed, the temporary + * bump is guaranteed to be gone before @kn is released. + */ + atomic_inc(&kn->active); + if (kernfs_lockdep(kn)) + rwsem_acquire(&kn->dep_map, 0, 1, _RET_IP_); +} + +/** + * kernfs_remove_self - remove a kernfs_node from its own method + * @kn: the self kernfs_node to remove + * + * The caller must be running off of a kernfs operation which is invoked + * with an active reference - e.g. one of kernfs_ops. This can be used to + * implement a file operation which deletes itself. + * + * For example, the "delete" file for a sysfs device directory can be + * implemented by invoking kernfs_remove_self() on the "delete" file + * itself. This function breaks the circular dependency of trying to + * deactivate self while holding an active ref itself. It isn't necessary + * to modify the usual removal path to use kernfs_remove_self(). The + * "delete" implementation can simply invoke kernfs_remove_self() on self + * before proceeding with the usual removal path. kernfs will ignore later + * kernfs_remove() on self. + * + * kernfs_remove_self() can be called multiple times concurrently on the + * same kernfs_node. Only the first one actually performs removal and + * returns %true. All others will wait until the kernfs operation which + * won self-removal finishes and return %false. Note that the losers wait + * for the completion of not only the winning kernfs_remove_self() but also + * the whole kernfs_ops which won the arbitration. This can be used to + * guarantee, for example, all concurrent writes to a "delete" file to + * finish only after the whole operation is complete. + */ +bool kernfs_remove_self(struct kernfs_node *kn) +{ + bool ret; + + mutex_lock(&kernfs_mutex); + kernfs_break_active_protection(kn); + + /* + * SUICIDAL is used to arbitrate among competing invocations. Only + * the first one will actually perform removal. When the removal + * is complete, SUICIDED is set and the active ref is restored + * while holding kernfs_mutex. The ones which lost arbitration + * waits for SUICDED && drained which can happen only after the + * enclosing kernfs operation which executed the winning instance + * of kernfs_remove_self() finished. + */ + if (!(kn->flags & KERNFS_SUICIDAL)) { + kn->flags |= KERNFS_SUICIDAL; + __kernfs_remove(kn); + kn->flags |= KERNFS_SUICIDED; + ret = true; + } else { + wait_queue_head_t *waitq = &kernfs_root(kn)->deactivate_waitq; + DEFINE_WAIT(wait); + + while (true) { + prepare_to_wait(waitq, &wait, TASK_UNINTERRUPTIBLE); + + if ((kn->flags & KERNFS_SUICIDED) && + atomic_read(&kn->active) == KN_DEACTIVATED_BIAS) + break; + + mutex_unlock(&kernfs_mutex); + schedule(); + mutex_lock(&kernfs_mutex); + } + finish_wait(waitq, &wait); + WARN_ON_ONCE(!RB_EMPTY_NODE(&kn->rb)); + ret = false; + } + + /* + * This must be done while holding kernfs_mutex; otherwise, waiting + * for SUICIDED && deactivated could finish prematurely. + */ + kernfs_unbreak_active_protection(kn); + + mutex_unlock(&kernfs_mutex); + return ret; +} + +/** + * kernfs_remove_by_name_ns - find a kernfs_node by name and remove it + * @parent: parent of the target + * @name: name of the kernfs_node to remove + * @ns: namespace tag of the kernfs_node to remove + * + * Look for the kernfs_node with @name and @ns under @parent and remove it. + * Returns 0 on success, -ENOENT if such entry doesn't exist. + */ +int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name, + const void *ns) +{ + struct kernfs_node *kn; + + if (!parent) { + WARN(1, KERN_WARNING "kernfs: can not remove '%s', no directory\n", + name); + return -ENOENT; + } + + mutex_lock(&kernfs_mutex); + + kn = kernfs_find_ns(parent, name, ns); + if (kn) + __kernfs_remove(kn); + + mutex_unlock(&kernfs_mutex); + + if (kn) + return 0; + else + return -ENOENT; +} + +/** + * kernfs_rename_ns - move and rename a kernfs_node + * @kn: target node + * @new_parent: new parent to put @sd under + * @new_name: new name + * @new_ns: new namespace tag + */ +int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent, + const char *new_name, const void *new_ns) +{ + struct kernfs_node *old_parent; + const char *old_name = NULL; + int error; + + /* can't move or rename root */ + if (!kn->parent) + return -EINVAL; + + mutex_lock(&kernfs_mutex); + + error = -ENOENT; + if (!kernfs_active(kn) || !kernfs_active(new_parent)) + goto out; + + error = 0; + if ((kn->parent == new_parent) && (kn->ns == new_ns) && + (strcmp(kn->name, new_name) == 0)) + goto out; /* nothing to rename */ + + error = -EEXIST; + if (kernfs_find_ns(new_parent, new_name, new_ns)) + goto out; + + /* rename kernfs_node */ + if (strcmp(kn->name, new_name) != 0) { + error = -ENOMEM; + new_name = kstrdup(new_name, GFP_KERNEL); + if (!new_name) + goto out; + } else { + new_name = NULL; + } + + /* + * Move to the appropriate place in the appropriate directories rbtree. + */ + kernfs_unlink_sibling(kn); + kernfs_get(new_parent); + + /* rename_lock protects ->parent and ->name accessors */ + spin_lock_irq(&kernfs_rename_lock); + + old_parent = kn->parent; + kn->parent = new_parent; + + kn->ns = new_ns; + if (new_name) { + if (!(kn->flags & KERNFS_STATIC_NAME)) + old_name = kn->name; + kn->flags &= ~KERNFS_STATIC_NAME; + kn->name = new_name; + } + + spin_unlock_irq(&kernfs_rename_lock); + + kn->hash = kernfs_name_hash(kn->name, kn->ns); + kernfs_link_sibling(kn); + + kernfs_put(old_parent); + kfree(old_name); + + error = 0; + out: + mutex_unlock(&kernfs_mutex); + return error; +} + +/* Relationship between s_mode and the DT_xxx types */ +static inline unsigned char dt_type(struct kernfs_node *kn) +{ + return (kn->mode >> 12) & 15; +} + +static int kernfs_dir_fop_release(struct inode *inode, struct file *filp) +{ + kernfs_put(filp->private_data); + return 0; +} + +static struct kernfs_node *kernfs_dir_pos(const void *ns, + struct kernfs_node *parent, loff_t hash, struct kernfs_node *pos) +{ + if (pos) { + int valid = kernfs_active(pos) && + pos->parent == parent && hash == pos->hash; + kernfs_put(pos); + if (!valid) + pos = NULL; + } + if (!pos && (hash > 1) && (hash < INT_MAX)) { + struct rb_node *node = parent->dir.children.rb_node; + while (node) { + pos = rb_to_kn(node); + + if (hash < pos->hash) + node = node->rb_left; + else if (hash > pos->hash) + node = node->rb_right; + else + break; + } + } + /* Skip over entries which are dying/dead or in the wrong namespace */ + while (pos && (!kernfs_active(pos) || pos->ns != ns)) { + struct rb_node *node = rb_next(&pos->rb); + if (!node) + pos = NULL; + else + pos = rb_to_kn(node); + } + return pos; +} + +static struct kernfs_node *kernfs_dir_next_pos(const void *ns, + struct kernfs_node *parent, ino_t ino, struct kernfs_node *pos) +{ + pos = kernfs_dir_pos(ns, parent, ino, pos); + if (pos) { + do { + struct rb_node *node = rb_next(&pos->rb); + if (!node) + pos = NULL; + else + pos = rb_to_kn(node); + } while (pos && (!kernfs_active(pos) || pos->ns != ns)); + } + return pos; +} + +static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx) +{ + struct dentry *dentry = file->f_path.dentry; + struct kernfs_node *parent = dentry->d_fsdata; + struct kernfs_node *pos = file->private_data; + const void *ns = NULL; + + if (!dir_emit_dots(file, ctx)) + return 0; + mutex_lock(&kernfs_mutex); + + if (kernfs_ns_enabled(parent)) + ns = kernfs_info(dentry->d_sb)->ns; + + for (pos = kernfs_dir_pos(ns, parent, ctx->pos, pos); + pos; + pos = kernfs_dir_next_pos(ns, parent, ctx->pos, pos)) { + const char *name = pos->name; + unsigned int type = dt_type(pos); + int len = strlen(name); + ino_t ino = pos->ino; + + ctx->pos = pos->hash; + file->private_data = pos; + kernfs_get(pos); + + mutex_unlock(&kernfs_mutex); + if (!dir_emit(ctx, name, len, ino, type)) + return 0; + mutex_lock(&kernfs_mutex); + } + mutex_unlock(&kernfs_mutex); + file->private_data = NULL; + ctx->pos = INT_MAX; + return 0; +} + +static loff_t kernfs_dir_fop_llseek(struct file *file, loff_t offset, + int whence) +{ + struct inode *inode = file_inode(file); + loff_t ret; + + mutex_lock(&inode->i_mutex); + ret = generic_file_llseek(file, offset, whence); + mutex_unlock(&inode->i_mutex); + + return ret; +} + +const struct file_operations kernfs_dir_fops = { + .read = generic_read_dir, + .iterate = kernfs_fop_readdir, + .release = kernfs_dir_fop_release, + .llseek = kernfs_dir_fop_llseek, +}; 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