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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * 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>
  */
 
 #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"
 
 static DEFINE_SPINLOCK(kernfs_rename_lock); /* kn->parent and ->name */
 /*
  * Don't use rename_lock to piggy back on pr_cont_buf. We don't want to
  * call pr_cont() while holding rename_lock. Because sometimes pr_cont()
  * will perform wakeups when releasing console_sem. Holding rename_lock
  * will introduce deadlock if the scheduler reads the kernfs_name in the
  * wakeup path.
  */
 static DEFINE_SPINLOCK(kernfs_pr_cont_lock);
 static char kernfs_pr_cont_buf[PATH_MAX];   /* protected by pr_cont_lock */
 static DEFINE_SPINLOCK(kernfs_idr_lock);    /* root->ino_idr */
 
 #define rb_to_kn(X) rb_entry((X), struct kernfs_node, rb)
 
 static bool kernfs_active(struct kernfs_node *kn)
 {
     lockdep_assert_held(&kernfs_root(kn)->kernfs_rwsem);
     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)
 {
     if (!kn)
         return strlcpy(buf, "(null)", buflen);
 
     return strlcpy(buf, kn->parent ? kn->name : "/", buflen);
 }
 
 /* kernfs_node_depth - compute depth from @from to @to */
 static size_t kernfs_depth(struct kernfs_node *from, struct kernfs_node *to)
 {
     size_t depth = 0;
 
     while (to->parent && to != from) {
         depth++;
         to = to->parent;
     }
     return depth;
 }
 
 static struct kernfs_node *kernfs_common_ancestor(struct kernfs_node *a,
                           struct kernfs_node *b)
 {
     size_t da, db;
     struct kernfs_root *ra = kernfs_root(a), *rb = kernfs_root(b);
 
     if (ra != rb)
         return NULL;
 
     da = kernfs_depth(ra->kn, a);
     db = kernfs_depth(rb->kn, b);
 
     while (da > db) {
         a = a->parent;
         da--;
     }
     while (db > da) {
         b = b->parent;
         db--;
     }
 
     /* worst case b and a will be the same at root */
     while (b != a) {
         b = b->parent;
         a = a->parent;
     }
 
     return a;
 }
 
 /**
  * kernfs_path_from_node_locked - find a pseudo-absolute path to @kn_to,
  * where kn_from is treated as root of the path.
  * @kn_from: kernfs node which should be treated as root for the path
  * @kn_to: kernfs node to which path is needed
  * @buf: buffer to copy the path into
  * @buflen: size of @buf
  *
  * We need to handle couple of scenarios here:
  * [1] when @kn_from is an ancestor of @kn_to at some level
  * kn_from: /n1/n2/n3
  * kn_to:   /n1/n2/n3/n4/n5
  * result:  /n4/n5
  *
  * [2] when @kn_from is on a different hierarchy and we need to find common
  * ancestor between @kn_from and @kn_to.
  * kn_from: /n1/n2/n3/n4
  * kn_to:   /n1/n2/n5
  * result:  /../../n5
  * OR
  * kn_from: /n1/n2/n3/n4/n5   [depth=5]
  * kn_to:   /n1/n2/n3         [depth=3]
  * result:  /../..
  *
  * [3] when @kn_to is NULL result will be "(null)"
  *
  * Returns the length of the full path.  If the full length is equal to or
  * greater than @buflen, @buf contains the truncated path with the trailing
  * '\0'.  On error, -errno is returned.
  */
 static int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
                     struct kernfs_node *kn_from,
                     char *buf, size_t buflen)
 {
     struct kernfs_node *kn, *common;
     const char parent_str[] = "/..";
     size_t depth_from, depth_to, len = 0;
     int i, j;
 
     if (!kn_to)
         return strlcpy(buf, "(null)", buflen);
 
     if (!kn_from)
         kn_from = kernfs_root(kn_to)->kn;
 
     if (kn_from == kn_to)
         return strlcpy(buf, "/", buflen);
 
     if (!buf)
         return -EINVAL;
 
     common = kernfs_common_ancestor(kn_from, kn_to);
     if (WARN_ON(!common))
         return -EINVAL;
 
     depth_to = kernfs_depth(common, kn_to);
     depth_from = kernfs_depth(common, kn_from);
 
     buf[0] = '\0';
 
     for (i = 0; i < depth_from; i++)
         len += strlcpy(buf + len, parent_str,
                    len < buflen ? buflen - len : 0);
 
     /* Calculate how many bytes we need for the rest */
     for (i = depth_to - 1; i >= 0; i--) {
         for (kn = kn_to, j = 0; j < i; j++)
             kn = kn->parent;
         len += strlcpy(buf + len, "/",
                    len < buflen ? buflen - len : 0);
         len += strlcpy(buf + len, kn->name,
                    len < buflen ? buflen - len : 0);
     }
 
     return len;
 }
 
 /**
  * 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.
  *
  * Fills buffer with "(null)" if @kn is NULL.
  *
  * 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_from_node - build path of node @to relative to @from.
  * @from: parent kernfs_node relative to which we need to build the path
  * @to: kernfs_node of interest
  * @buf: buffer to copy @to's path into
  * @buflen: size of @buf
  *
  * Builds @to's path relative to @from in @buf. @from and @to must
  * be on the same kernfs-root. If @from is not parent of @to, then a relative
  * path (which includes '..'s) as needed to reach from @from to @to is
  * returned.
  *
  * Returns the length of the full path.  If the full length is equal to or
  * greater than @buflen, @buf contains the truncated path with the trailing
  * '\0'.  On error, -errno is returned.
  */
 int kernfs_path_from_node(struct kernfs_node *to, struct kernfs_node *from,
               char *buf, size_t buflen)
 {
     unsigned long flags;
     int ret;
 
     spin_lock_irqsave(&kernfs_rename_lock, flags);
     ret = kernfs_path_from_node_locked(to, from, buf, buflen);
     spin_unlock_irqrestore(&kernfs_rename_lock, flags);
     return ret;
 }
 EXPORT_SYMBOL_GPL(kernfs_path_from_node);
 
 /**
  * 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_pr_cont_lock, flags);
 
     kernfs_name(kn, kernfs_pr_cont_buf, sizeof(kernfs_pr_cont_buf));
     pr_cont("%s", kernfs_pr_cont_buf);
 
     spin_unlock_irqrestore(&kernfs_pr_cont_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;
     int sz;
 
     spin_lock_irqsave(&kernfs_pr_cont_lock, flags);
 
     sz = kernfs_path_from_node(kn, NULL, kernfs_pr_cont_buf,
                    sizeof(kernfs_pr_cont_buf));
     if (sz < 0) {
         pr_cont("(error)");
         goto out;
     }
 
     if (sz >= sizeof(kernfs_pr_cont_buf)) {
         pr_cont("(name too long)");
         goto out;
     }
 
     pr_cont("%s", kernfs_pr_cont_buf);
 
 out:
     spin_unlock_irqrestore(&kernfs_pr_cont_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(ns);
     unsigned int len = strlen(name);
     while (len--)
         hash = partial_name_hash(*name++, hash);
     hash = end_name_hash(hash);
     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 -1;
     if (hash > kn->hash)
         return 1;
     if (ns < kn->ns)
         return -1;
     if (ns > kn->ns)
         return 1;
     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:
  *  kernfs_rwsem held exclusive
  *
  *  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;
 
     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);
 
     /* successfully added, account subdir number */
     if (kernfs_type(kn) == KERNFS_DIR)
         kn->parent->dir.subdirs++;
     kernfs_inc_rev(kn->parent);
 
     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:
  *  kernfs_rwsem held exclusive
  */
 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--;
     kernfs_inc_rev(kn->parent);
 
     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)
 {
     int v;
 
     if (unlikely(!kn))
         return;
 
     if (kernfs_lockdep(kn))
         rwsem_release(&kn->dep_map, _RET_IP_);
     v = atomic_dec_return(&kn->active);
     if (likely(v != KN_DEACTIVATED_BIAS))
         return;
 
     wake_up_all(&kernfs_root(kn)->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_root(kn)->kernfs_rwsem)
     __acquires(&kernfs_root(kn)->kernfs_rwsem)
 {
     struct kernfs_root *root = kernfs_root(kn);
 
     lockdep_assert_held_write(&root->kernfs_rwsem);
     WARN_ON_ONCE(kernfs_active(kn));
 
     up_write(&root->kernfs_rwsem);
 
     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, _RET_IP_);
     }
 
     kernfs_drain_open_files(kn);
 
     down_write(&root->kernfs_rwsem);
 }
 
 /**
  * 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);
 
     kfree_const(kn->name);
 
     if (kn->iattr) {
         simple_xattrs_free(&kn->iattr->xattrs);
         kmem_cache_free(kernfs_iattrs_cache, kn->iattr);
     }
     spin_lock(&kernfs_idr_lock);
     idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));
     spin_unlock(&kernfs_idr_lock);
     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 */
         idr_destroy(&root->ino_idr);
         kfree(root);
     }
 }
 EXPORT_SYMBOL_GPL(kernfs_put);
 
 /**
  * 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 kernfs_dentry_node(dentry);
     return NULL;
 }
 
 static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
                          struct kernfs_node *parent,
                          const char *name, umode_t mode,
                          kuid_t uid, kgid_t gid,
                          unsigned flags)
 {
     struct kernfs_node *kn;
     u32 id_highbits;
     int ret;
 
     name = kstrdup_const(name, GFP_KERNEL);
     if (!name)
         return NULL;
 
     kn = kmem_cache_zalloc(kernfs_node_cache, GFP_KERNEL);
     if (!kn)
         goto err_out1;
 
     idr_preload(GFP_KERNEL);
     spin_lock(&kernfs_idr_lock);
     ret = idr_alloc_cyclic(&root->ino_idr, kn, 1, 0, GFP_ATOMIC);
     if (ret >= 0 && ret < root->last_id_lowbits)
         root->id_highbits++;
     id_highbits = root->id_highbits;
     root->last_id_lowbits = ret;
     spin_unlock(&kernfs_idr_lock);
     idr_preload_end();
     if (ret < 0)
         goto err_out2;
 
     kn->id = (u64)id_highbits << 32 | 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;
 
     if (!uid_eq(uid, GLOBAL_ROOT_UID) || !gid_eq(gid, GLOBAL_ROOT_GID)) {
         struct iattr iattr = {
             .ia_valid = ATTR_UID | ATTR_GID,
             .ia_uid = uid,
             .ia_gid = gid,
         };
 
         ret = __kernfs_setattr(kn, &iattr);
         if (ret < 0)
             goto err_out3;
     }
 
     if (parent) {
         ret = security_kernfs_init_security(parent, kn);
         if (ret)
             goto err_out3;
     }
 
     return kn;
 
  err_out3:
     idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));
  err_out2:
     kmem_cache_free(kernfs_node_cache, kn);
  err_out1:
     kfree_const(name);
     return NULL;
 }
 
 struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
                     const char *name, umode_t mode,
                     kuid_t uid, kgid_t gid,
                     unsigned flags)
 {
     struct kernfs_node *kn;
 
     kn = __kernfs_new_node(kernfs_root(parent), parent,
                    name, mode, uid, gid, flags);
     if (kn) {
         kernfs_get(parent);
         kn->parent = parent;
     }
     return kn;
 }
 
 /*
  * kernfs_find_and_get_node_by_id - get kernfs_node from node id
  * @root: the kernfs root
  * @id: the target node id
  *
  * @id's lower 32bits encode ino and upper gen.  If the gen portion is
  * zero, all generations are matched.
  *
  * RETURNS:
  * NULL on failure. Return a kernfs node with reference counter incremented
  */
 struct kernfs_node *kernfs_find_and_get_node_by_id(struct kernfs_root *root,
                            u64 id)
 {
     struct kernfs_node *kn;
     ino_t ino = kernfs_id_ino(id);
     u32 gen = kernfs_id_gen(id);
 
     spin_lock(&kernfs_idr_lock);
 
     kn = idr_find(&root->ino_idr, (u32)ino);
     if (!kn)
         goto err_unlock;
 
     if (sizeof(ino_t) >= sizeof(u64)) {
         /* we looked up with the low 32bits, compare the whole */
         if (kernfs_ino(kn) != ino)
             goto err_unlock;
     } else {
         /* 0 matches all generations */
         if (unlikely(gen && kernfs_gen(kn) != gen))
             goto err_unlock;
     }
 
     /*
      * ACTIVATED is protected with kernfs_mutex but it was clear when
      * @kn was added to idr and we just wanna see it set.  No need to
      * grab kernfs_mutex.
      */
     if (unlikely(!(kn->flags & KERNFS_ACTIVATED) ||
              !atomic_inc_not_zero(&kn->count)))
         goto err_unlock;
 
     spin_unlock(&kernfs_idr_lock);
     return kn;
 err_unlock:
     spin_unlock(&kernfs_idr_lock);
     return NULL;
 }
 
 /**
  *  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_root *root = kernfs_root(parent);
     struct kernfs_iattrs *ps_iattr;
     bool has_ns;
     int ret;
 
     down_write(&root->kernfs_rwsem);
 
     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_EMPTY_DIR)
         goto out_unlock;
 
     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) {
         ktime_get_real_ts64(&ps_iattr->ia_ctime);
         ps_iattr->ia_mtime = ps_iattr->ia_ctime;
     }
 
     up_write(&root->kernfs_rwsem);
 
     /*
      * 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:
     up_write(&root->kernfs_rwsem);
     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_root(parent)->kernfs_rwsem);
 
     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;
 }
 
 static struct kernfs_node *kernfs_walk_ns(struct kernfs_node *parent,
                       const unsigned char *path,
                       const void *ns)
 {
     size_t len;
     char *p, *name;
 
     lockdep_assert_held_read(&kernfs_root(parent)->kernfs_rwsem);
 
     spin_lock_irq(&kernfs_pr_cont_lock);
 
     len = strlcpy(kernfs_pr_cont_buf, path, sizeof(kernfs_pr_cont_buf));
 
     if (len >= sizeof(kernfs_pr_cont_buf)) {
         spin_unlock_irq(&kernfs_pr_cont_lock);
         return NULL;
     }
 
     p = kernfs_pr_cont_buf;
 
     while ((name = strsep(&p, "/")) && parent) {
         if (*name == '\0')
             continue;
         parent = kernfs_find_ns(parent, name, ns);
     }
 
     spin_unlock_irq(&kernfs_pr_cont_lock);
 
     return parent;
 }
 
 /**
  * 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;
     struct kernfs_root *root = kernfs_root(parent);
 
     down_read(&root->kernfs_rwsem);
     kn = kernfs_find_ns(parent, name, ns);
     kernfs_get(kn);
     up_read(&root->kernfs_rwsem);
 
     return kn;
 }
 EXPORT_SYMBOL_GPL(kernfs_find_and_get_ns);
 
 /**
  * kernfs_walk_and_get_ns - find and get kernfs_node with the given path
  * @parent: kernfs_node to search under
  * @path: path to look for
  * @ns: the namespace tag to use
  *
  * Look for kernfs_node with path @path 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_walk_and_get_ns(struct kernfs_node *parent,
                        const char *path, const void *ns)
 {
     struct kernfs_node *kn;
     struct kernfs_root *root = kernfs_root(parent);
 
     down_read(&root->kernfs_rwsem);
     kn = kernfs_walk_ns(parent, path, ns);
     kernfs_get(kn);
     up_read(&root->kernfs_rwsem);
 
     return kn;
 }
 
 /**
  * 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);
 
     idr_init(&root->ino_idr);
     init_rwsem(&root->kernfs_rwsem);
     INIT_LIST_HEAD(&root->supers);
 
     /*
      * On 64bit ino setups, id is ino.  On 32bit, low 32bits are ino.
      * High bits generation.  The starting value for both ino and
      * genenration is 1.  Initialize upper 32bit allocation
      * accordingly.
      */
     if (sizeof(ino_t) >= sizeof(u64))
         root->id_highbits = 0;
     else
         root->id_highbits = 1;
 
     kn = __kernfs_new_node(root, NULL, "", S_IFDIR | S_IRUGO | S_IXUGO,
                    GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
                    KERNFS_DIR);
     if (!kn) {
         idr_destroy(&root->ino_idr);
         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 holds kernfs_rwsem from the root so the root
      *  shouldn't be freed during the operation.
      */
     kernfs_get(root->kn);
     kernfs_remove(root->kn);
     kernfs_put(root->kn); /* will also free @root */
 }
 
 /**
  * kernfs_root_to_node - return the kernfs_node associated with a kernfs_root
  * @root: root to use to lookup
  */
 struct kernfs_node *kernfs_root_to_node(struct kernfs_root *root)
 {
     return root->kn;
 }
 
 /**
  * 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
  * @uid: uid of the new directory
  * @gid: gid 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,
                      kuid_t uid, kgid_t gid,
                      void *priv, const void *ns)
 {
     struct kernfs_node *kn;
     int rc;
 
     /* allocate */
     kn = kernfs_new_node(parent, name, mode | S_IFDIR,
                  uid, gid, 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);
 }
 
 /**
  * kernfs_create_empty_dir - create an always empty directory
  * @parent: parent in which to create a new directory
  * @name: name of the new directory
  *
  * Returns the created node on success, ERR_PTR() value on failure.
  */
 struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
                         const char *name)
 {
     struct kernfs_node *kn;
     int rc;
 
     /* allocate */
     kn = kernfs_new_node(parent, name, S_IRUGO|S_IXUGO|S_IFDIR,
                  GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, KERNFS_DIR);
     if (!kn)
         return ERR_PTR(-ENOMEM);
 
     kn->flags |= KERNFS_EMPTY_DIR;
     kn->dir.root = parent->dir.root;
     kn->ns = NULL;
     kn->priv = NULL;
 
     /* link in */
     rc = kernfs_add_one(kn);
     if (!rc)
         return kn;
 
     kernfs_put(kn);
     return ERR_PTR(rc);
 }
 
 static int kernfs_dop_revalidate(struct dentry *dentry, unsigned int flags)
 {
     struct kernfs_node *kn;
     struct kernfs_root *root;
 
     if (flags & LOOKUP_RCU)
         return -ECHILD;
 
     /* Negative hashed dentry? */
     if (d_really_is_negative(dentry)) {
         struct kernfs_node *parent;
 
         /* If the kernfs parent node has changed discard and
          * proceed to ->lookup.
          */
         spin_lock(&dentry->d_lock);
         parent = kernfs_dentry_node(dentry->d_parent);
         if (parent) {
             spin_unlock(&dentry->d_lock);
             root = kernfs_root(parent);
             down_read(&root->kernfs_rwsem);
             if (kernfs_dir_changed(parent, dentry)) {
                 up_read(&root->kernfs_rwsem);
                 return 0;
             }
             up_read(&root->kernfs_rwsem);
         } else
             spin_unlock(&dentry->d_lock);
 
         /* The kernfs parent node hasn't changed, leave the
          * dentry negative and return success.
          */
         return 1;
     }
 
     kn = kernfs_dentry_node(dentry);
     root = kernfs_root(kn);
     down_read(&root->kernfs_rwsem);
 
     /* The kernfs node has been deactivated */
     if (!kernfs_active(kn))
         goto out_bad;
 
     /* The kernfs node has been moved? */
     if (kernfs_dentry_node(dentry->d_parent) != 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;
 
     up_read(&root->kernfs_rwsem);
     return 1;
 out_bad:
     up_read(&root->kernfs_rwsem);
     return 0;
 }
 
 const struct dentry_operations kernfs_dops = {
     .d_revalidate   = kernfs_dop_revalidate,
 };
 
 static struct dentry *kernfs_iop_lookup(struct inode *dir,
                     struct dentry *dentry,
                     unsigned int flags)
 {
     struct kernfs_node *parent = dir->i_private;
     struct kernfs_node *kn;
     struct kernfs_root *root;
     struct inode *inode = NULL;
     const void *ns = NULL;
 
     root = kernfs_root(parent);
     down_read(&root->kernfs_rwsem);
     if (kernfs_ns_enabled(parent))
         ns = kernfs_info(dir->i_sb)->ns;
 
     kn = kernfs_find_ns(parent, dentry->d_name.name, ns);
     /* attach dentry and inode */
     if (kn) {
         /* Inactive nodes are invisible to the VFS so don't
          * create a negative.
          */
         if (!kernfs_active(kn)) {
             up_read(&root->kernfs_rwsem);
             return NULL;
         }
         inode = kernfs_get_inode(dir->i_sb, kn);
         if (!inode)
             inode = ERR_PTR(-ENOMEM);
     }
     /*
      * Needed for negative dentry validation.
      * The negative dentry can be created in kernfs_iop_lookup()
      * or transforms from positive dentry in dentry_unlink_inode()
      * called from vfs_rmdir().
      */
     if (!IS_ERR(inode))
         kernfs_set_rev(parent, dentry);
     up_read(&root->kernfs_rwsem);
 
     /* instantiate and hash (possibly negative) dentry */
     return d_splice_alias(inode, dentry);
 }
 
 static int kernfs_iop_mkdir(struct user_namespace *mnt_userns,
                 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  = kernfs_dentry_node(dentry);
     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 user_namespace *mnt_userns,
                  struct inode *old_dir, struct dentry *old_dentry,
                  struct inode *new_dir, struct dentry *new_dentry,
                  unsigned int flags)
 {
     struct kernfs_node *kn = kernfs_dentry_node(old_dentry);
     struct kernfs_node *new_parent = new_dir->i_private;
     struct kernfs_syscall_ops *scops = kernfs_root(kn)->syscall_ops;
     int ret;
 
     if (flags)
         return -EINVAL;
 
     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,
     .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_write(&kernfs_root(root)->kernfs_rwsem);
 
     /* 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;
     struct kernfs_root *root = kernfs_root(kn);
 
     down_write(&root->kernfs_rwsem);
 
     pos = NULL;
     while ((pos = kernfs_next_descendant_post(pos, kn))) {
         if (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;
     }
 
     up_write(&root->kernfs_rwsem);
 }
 
 static void __kernfs_remove(struct kernfs_node *kn)
 {
     struct kernfs_node *pos;
 
     /* Short-circuit if non-root @kn has already finished removal. */
     if (!kn)
         return;
 
     lockdep_assert_held_write(&kernfs_root(kn)->kernfs_rwsem);
 
     /*
      * This is for kernfs_remove_self() which plays with active ref
      * after removal.
      */
     if (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_rwsem 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) {
                 ktime_get_real_ts64(&ps_iattr->ia_ctime);
                 ps_iattr->ia_mtime = ps_iattr->ia_ctime;
             }
 
             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)
 {
     struct kernfs_root *root;
 
     if (!kn)
         return;
 
     root = kernfs_root(kn);
 
     down_write(&root->kernfs_rwsem);
     __kernfs_remove(kn);
     up_write(&root->kernfs_rwsem);
 }
 
 /**
  * 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;
     struct kernfs_root *root = kernfs_root(kn);
 
     down_write(&root->kernfs_rwsem);
     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 kernfs_rwsem for held exclusive.  The ones which lost
      * arbitration waits for SUICIDED && 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;
 
             up_write(&root->kernfs_rwsem);
             schedule();
             down_write(&root->kernfs_rwsem);
         }
         finish_wait(waitq, &wait);
         WARN_ON_ONCE(!RB_EMPTY_NODE(&kn->rb));
         ret = false;
     }
 
     /*
      * This must be done while kernfs_rwsem held exclusive; otherwise,
      * waiting for SUICIDED && deactivated could finish prematurely.
      */
     kernfs_unbreak_active_protection(kn);
 
     up_write(&root->kernfs_rwsem);
     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;
     struct kernfs_root *root;
 
     if (!parent) {
         WARN(1, KERN_WARNING "kernfs: can not remove '%s', no directory\n",
             name);
         return -ENOENT;
     }
 
     root = kernfs_root(parent);
     down_write(&root->kernfs_rwsem);
 
     kn = kernfs_find_ns(parent, name, ns);
     if (kn)
         __kernfs_remove(kn);
 
     up_write(&root->kernfs_rwsem);
 
     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;
     struct kernfs_root *root;
     const char *old_name = NULL;
     int error;
 
     /* can't move or rename root */
     if (!kn->parent)
         return -EINVAL;
 
     root = kernfs_root(kn);
     down_write(&root->kernfs_rwsem);
 
     error = -ENOENT;
     if (!kernfs_active(kn) || !kernfs_active(new_parent) ||
         (new_parent->flags & KERNFS_EMPTY_DIR))
         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_const(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) {
         old_name = kn->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_const(old_name);
 
     error = 0;
  out:
     up_write(&root->kernfs_rwsem);
     return error;
 }
 
 /* Relationship between 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 = kernfs_dentry_node(dentry);
     struct kernfs_node *pos = file->private_data;
     struct kernfs_root *root;
     const void *ns = NULL;
 
     if (!dir_emit_dots(file, ctx))
         return 0;
 
     root = kernfs_root(parent);
     down_read(&root->kernfs_rwsem);
 
     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 = kernfs_ino(pos);
 
         ctx->pos = pos->hash;
         file->private_data = pos;
         kernfs_get(pos);
 
         up_read(&root->kernfs_rwsem);
         if (!dir_emit(ctx, name, len, ino, type))
             return 0;
         down_read(&root->kernfs_rwsem);
     }
     up_read(&root->kernfs_rwsem);
     file->private_data = NULL;
     ctx->pos = INT_MAX;
     return 0;
 }
 
 const struct file_operations kernfs_dir_fops = {
     .read       = generic_read_dir,
     .iterate_shared = kernfs_fop_readdir,
     .release    = kernfs_dir_fop_release,
     .llseek     = generic_file_llseek,
 };

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