1 files changed, 1077 insertions, 0 deletions

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
new file mode 100644
index 000000000000..bd6e18be6e1a
--- /dev/null
+++ b/fs/kernfs/dir.c
@@ -0,0 +1,1077 @@
+/*
+ * 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/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);
+
+#define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb)
+
+/**
+ *      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 < 1)
+                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
+ *
+ *      Unlink @kn from its sibling rbtree which starts from
+ *      kn->parent->dir.children.
+ *
+ *      Locking:
+ *      mutex_lock(kernfs_mutex)
+ */
+static void kernfs_unlink_sibling(struct kernfs_node *kn)
+{
+        if (kernfs_type(kn) == KERNFS_DIR)
+                kn->parent->dir.subdirs--;
+
+        rb_erase(&kn->rb, &kn->parent->dir.children);
+}
+
+/**
+ *      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 (kn->flags & KERNFS_LOCKDEP)
+                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)
+{
+        int v;
+
+        if (unlikely(!kn))
+                return;
+
+        if (kn->flags & KERNFS_LOCKDEP)
+                rwsem_release(&kn->dep_map, 1, _RET_IP_);
+        v = atomic_dec_return(&kn->active);
+        if (likely(v != KN_DEACTIVATED_BIAS))
+                return;
+
+        /*
+         * atomic_dec_return() is a mb(), we'll always see the updated
+         * kn->u.completion.
+         */
+        complete(kn->u.completion);
+}
+
+/**
+ *      kernfs_deactivate - deactivate kernfs_node
+ *      @kn: kernfs_node to deactivate
+ *
+ *      Deny new active references and drain existing ones.
+ */
+static void kernfs_deactivate(struct kernfs_node *kn)
+{
+        DECLARE_COMPLETION_ONSTACK(wait);
+        int v;
+
+        BUG_ON(!(kn->flags & KERNFS_REMOVED));
+
+        if (!(kernfs_type(kn) & KERNFS_ACTIVE_REF))
+                return;
+
+        kn->u.completion = (void *)&wait;
+
+        if (kn->flags & KERNFS_LOCKDEP)
+                rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
+        /* atomic_add_return() is a mb(), put_active() will always see
+         * the updated kn->u.completion.
+         */
+        v = atomic_add_return(KN_DEACTIVATED_BIAS, &kn->active);
+
+        if (v != KN_DEACTIVATED_BIAS) {
+                if (kn->flags & KERNFS_LOCKDEP)
+                        lock_contended(&kn->dep_map, _RET_IP_);
+                wait_for_completion(&wait);
+        }
+
+        if (kn->flags & KERNFS_LOCKDEP) {
+                lock_acquired(&kn->dep_map, _RET_IP_);
+                rwsem_release(&kn->dep_map, 1, _RET_IP_);
+        }
+}
+
+/**
+ * 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(!(kn->flags & KERNFS_REMOVED), "kernfs: free using entry: %s/%s\n",
+             parent ? parent->name : "", kn->name);
+
+        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 deleted */
+        if (kn->flags & KERNFS_REMOVED)
+                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,
+};
+
+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, 0);
+
+        kn->name = name;
+        kn->mode = mode;
+        kn->flags = flags | KERNFS_REMOVED;
+
+        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_addrm_start - prepare for kernfs_node add/remove
+ *      @acxt: pointer to kernfs_addrm_cxt to be used
+ *
+ *      This function is called when the caller is about to add or remove
+ *      kernfs_node.  This function acquires kernfs_mutex.  @acxt is used
+ *      to keep and pass context to other addrm functions.
+ *
+ *      LOCKING:
+ *      Kernel thread context (may sleep).  kernfs_mutex is locked on
+ *      return.
+ */
+void kernfs_addrm_start(struct kernfs_addrm_cxt *acxt)
+        __acquires(kernfs_mutex)
+{
+        memset(acxt, 0, sizeof(*acxt));
+
+        mutex_lock(&kernfs_mutex);
+}
+
+/**
+ *      kernfs_add_one - add kernfs_node to parent without warning
+ *      @acxt: addrm context to use
+ *      @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.
+ *
+ *      This function should be called between calls to
+ *      kernfs_addrm_start() and kernfs_addrm_finish() and should be passed
+ *      the same @acxt as passed to kernfs_addrm_start().
+ *
+ *      LOCKING:
+ *      Determined by kernfs_addrm_start().
+ *
+ *      RETURNS:
+ *      0 on success, -EEXIST if entry with the given name already
+ *      exists.
+ */
+int kernfs_add_one(struct kernfs_addrm_cxt *acxt, struct kernfs_node *kn)
+{
+        struct kernfs_node *parent = kn->parent;
+        bool has_ns = kernfs_ns_enabled(parent);
+        struct kernfs_iattrs *ps_iattr;
+        int ret;
+
+        if (has_ns != (bool)kn->ns) {
+                WARN(1, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
+                     has_ns ? "required" : "invalid", parent->name, kn->name);
+                return -EINVAL;
+        }
+
+        if (kernfs_type(parent) != KERNFS_DIR)
+                return -EINVAL;
+
+        if (parent->flags & KERNFS_REMOVED)
+                return -ENOENT;
+
+        kn->hash = kernfs_name_hash(kn->name, kn->ns);
+
+        ret = kernfs_link_sibling(kn);
+        if (ret)
+                return ret;
+
+        /* 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;
+        }
+
+        /* Mark the entry added into directory tree */
+        kn->flags &= ~KERNFS_REMOVED;
+
+        return 0;
+}
+
+/**
+ *      kernfs_remove_one - remove kernfs_node from parent
+ *      @acxt: addrm context to use
+ *      @kn: kernfs_node to be removed
+ *
+ *      Mark @kn removed and drop nlink of parent inode if @kn is a
+ *      directory.  @kn is unlinked from the children list.
+ *
+ *      This function should be called between calls to
+ *      kernfs_addrm_start() and kernfs_addrm_finish() and should be
+ *      passed the same @acxt as passed to kernfs_addrm_start().
+ *
+ *      LOCKING:
+ *      Determined by kernfs_addrm_start().
+ */
+static void kernfs_remove_one(struct kernfs_addrm_cxt *acxt,
+                              struct kernfs_node *kn)
+{
+        struct kernfs_iattrs *ps_iattr;
+
+        /*
+         * Removal can be called multiple times on the same node.  Only the
+         * first invocation is effective and puts the base ref.
+         */
+        if (kn->flags & KERNFS_REMOVED)
+                return;
+
+        if (kn->parent) {
+                kernfs_unlink_sibling(kn);
+
+                /* Update timestamps on the parent */
+                ps_iattr = kn->parent->iattr;
+                if (ps_iattr) {
+                        ps_iattr->ia_iattr.ia_ctime = CURRENT_TIME;
+                        ps_iattr->ia_iattr.ia_mtime = CURRENT_TIME;
+                }
+        }
+
+        kn->flags |= KERNFS_REMOVED;
+        kn->u.removed_list = acxt->removed;
+        acxt->removed = kn;
+}
+
+/**
+ *      kernfs_addrm_finish - finish up kernfs_node add/remove
+ *      @acxt: addrm context to finish up
+ *
+ *      Finish up kernfs_node add/remove.  Resources acquired by
+ *      kernfs_addrm_start() are released and removed kernfs_nodes are
+ *      cleaned up.
+ *
+ *      LOCKING:
+ *      kernfs_mutex is released.
+ */
+void kernfs_addrm_finish(struct kernfs_addrm_cxt *acxt)
+        __releases(kernfs_mutex)
+{
+        /* release resources acquired by kernfs_addrm_start() */
+        mutex_unlock(&kernfs_mutex);
+
+        /* kill removed kernfs_nodes */
+        while (acxt->removed) {
+                struct kernfs_node *kn = acxt->removed;
+
+                acxt->removed = kn->u.removed_list;
+
+                kernfs_deactivate(kn);
+                kernfs_unmap_bin_file(kn);
+                kernfs_put(kn);
+        }
+}
+
+/**
+ * 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
+ * @kdops: optional directory syscall operations for the hierarchy
+ * @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_dir_ops *kdops, 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->flags &= ~KERNFS_REMOVED;
+        kn->priv = priv;
+        kn->dir.root = root;
+
+        root->dir_ops = kdops;
+        root->kn = 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_addrm_cxt acxt;
+        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 */
+        kernfs_addrm_start(&acxt);
+        rc = kernfs_add_one(&acxt, kn);
+        kernfs_addrm_finish(&acxt);
+
+        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) {
+                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_dir_ops *kdops = kernfs_root(parent)->dir_ops;
+
+        if (!kdops || !kdops->mkdir)
+                return -EPERM;
+
+        return kdops->mkdir(parent, dentry->d_name.name, mode);
+}
+
+static int kernfs_iop_rmdir(struct inode *dir, struct dentry *dentry)
+{
+        struct kernfs_node *kn  = dentry->d_fsdata;
+        struct kernfs_dir_ops *kdops = kernfs_root(kn)->dir_ops;
+
+        if (!kdops || !kdops->rmdir)
+                return -EPERM;
+
+        return kdops->rmdir(kn);
+}
+
+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_dir_ops *kdops = kernfs_root(kn)->dir_ops;
+
+        if (!kdops || !kdops->rename)
+                return -EPERM;
+
+        return kdops->rename(kn, new_parent, new_dentry->d_name.name);
+}
+
+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;
+}
+
+static void __kernfs_remove(struct kernfs_addrm_cxt *acxt,
+                            struct kernfs_node *kn)
+{
+        struct kernfs_node *pos, *next;
+
+        if (!kn)
+                return;
+
+        pr_debug("kernfs %s: removing\n", kn->name);
+
+        next = NULL;
+        do {
+                pos = next;
+                next = kernfs_next_descendant_post(pos, kn);
+                if (pos)
+                        kernfs_remove_one(acxt, pos);
+        } while (next);
+}
+
+/**
+ * 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)
+{
+        struct kernfs_addrm_cxt acxt;
+
+        kernfs_addrm_start(&acxt);
+        __kernfs_remove(&acxt, kn);
+        kernfs_addrm_finish(&acxt);
+}
+
+/**
+ * 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_addrm_cxt acxt;
+        struct kernfs_node *kn;
+
+        if (!parent) {
+                WARN(1, KERN_WARNING "kernfs: can not remove '%s', no directory\n",
+                        name);
+                return -ENOENT;
+        }
+
+        kernfs_addrm_start(&acxt);
+
+        kn = kernfs_find_ns(parent, name, ns);
+        if (kn)
+                __kernfs_remove(&acxt, kn);
+
+        kernfs_addrm_finish(&acxt);
+
+        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)
+{
+        int error;
+
+        mutex_lock(&kernfs_mutex);
+
+        error = -ENOENT;
+        if ((kn->flags | new_parent->flags) & KERNFS_REMOVED)
+                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;
+
+                if (kn->flags & KERNFS_STATIC_NAME)
+                        kn->flags &= ~KERNFS_STATIC_NAME;
+                else
+                        kfree(kn->name);
+
+                kn->name = new_name;
+        }
+
+        /*
+         * Move to the appropriate place in the appropriate directories rbtree.
+         */
+        kernfs_unlink_sibling(kn);
+        kernfs_get(new_parent);
+        kernfs_put(kn->parent);
+        kn->ns = new_ns;
+        kn->hash = kernfs_name_hash(kn->name, kn->ns);
+        kn->parent = new_parent;
+        kernfs_link_sibling(kn);
+
+        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 = !(pos->flags & KERNFS_REMOVED) &&
+                        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 in the wrong namespace */
+        while (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 && 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,
+};