fs/kernfs/mount.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * fs/kernfs/mount.c - kernfs mount 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/fs.h>
 #include <linux/mount.h>
 #include <linux/init.h>
 #include <linux/magic.h>
 #include <linux/slab.h>
 #include <linux/pagemap.h>
 #include <linux/namei.h>
 #include <linux/seq_file.h>
 #include <linux/exportfs.h>

 #include "kernfs-internal.h"

 struct kmem_cache *kernfs_node_cache, *kernfs_iattrs_cache;
 struct kernfs_global_locks *kernfs_locks;

 static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
 {
 	struct kernfs_root *root = kernfs_root(kernfs_dentry_node(dentry));
 	struct kernfs_syscall_ops *scops = root->syscall_ops;

 	if (scops && scops->show_options)
 		return scops->show_options(sf, root);
 	return 0;
 }

 static int kernfs_sop_show_path(struct seq_file *sf, struct dentry *dentry)
 {
 	struct kernfs_node *node = kernfs_dentry_node(dentry);
 	struct kernfs_root *root = kernfs_root(node);
 	struct kernfs_syscall_ops *scops = root->syscall_ops;

 	if (scops && scops->show_path)
 		return scops->show_path(sf, node, root);

 	seq_dentry(sf, dentry, " \t\n\\");
 	return 0;
 }

 const struct super_operations kernfs_sops = {
 	.statfs		= simple_statfs,
 	.drop_inode	= generic_delete_inode,
 	.evict_inode	= kernfs_evict_inode,

 	.show_options	= kernfs_sop_show_options,
 	.show_path	= kernfs_sop_show_path,
 };

 static int kernfs_encode_fh(struct inode *inode, __u32 *fh, int *max_len,
 			    struct inode *parent)
 {
 	struct kernfs_node *kn = inode->i_private;

 	if (*max_len < 2) {
 		*max_len = 2;
 		return FILEID_INVALID;
 	}

 	*max_len = 2;
 	*(u64 *)fh = kn->id;
 	return FILEID_KERNFS;
 }

 static struct dentry *__kernfs_fh_to_dentry(struct super_block *sb,
 					    struct fid *fid, int fh_len,
 					    int fh_type, bool get_parent)
 {
 	struct kernfs_super_info *info = kernfs_info(sb);
 	struct kernfs_node *kn;
 	struct inode *inode;
 	u64 id;

 	if (fh_len < 2)
 		return NULL;

 	switch (fh_type) {
 	case FILEID_KERNFS:
 		id = *(u64 *)fid;
 		break;
 	case FILEID_INO32_GEN:
 	case FILEID_INO32_GEN_PARENT:
 		/*
 		 * blk_log_action() exposes "LOW32,HIGH32" pair without
 		 * type and userland can call us with generic fid
 		 * constructed from them.  Combine it back to ID.  See
 		 * blk_log_action().
 		 */
 		id = ((u64)fid->i32.gen << 32) | fid->i32.ino;
 		break;
 	default:
 		return NULL;
 	}

 	kn = kernfs_find_and_get_node_by_id(info->root, id);
 	if (!kn)
 		return ERR_PTR(-ESTALE);

 	if (get_parent) {
 		struct kernfs_node *parent;

 		parent = kernfs_get_parent(kn);
 		kernfs_put(kn);
 		kn = parent;
 		if (!kn)
 			return ERR_PTR(-ESTALE);
 	}

 	inode = kernfs_get_inode(sb, kn);
 	kernfs_put(kn);
 	if (!inode)
 		return ERR_PTR(-ESTALE);

 	return d_obtain_alias(inode);
 }

 static struct dentry *kernfs_fh_to_dentry(struct super_block *sb,
 					  struct fid *fid, int fh_len,
 					  int fh_type)
 {
 	return __kernfs_fh_to_dentry(sb, fid, fh_len, fh_type, false);
 }

 static struct dentry *kernfs_fh_to_parent(struct super_block *sb,
 					  struct fid *fid, int fh_len,
 					  int fh_type)
 {
 	return __kernfs_fh_to_dentry(sb, fid, fh_len, fh_type, true);
 }

 static struct dentry *kernfs_get_parent_dentry(struct dentry *child)
 {
 	struct kernfs_node *kn = kernfs_dentry_node(child);

 	return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent));
 }

 static const struct export_operations kernfs_export_ops = {
 	.encode_fh	= kernfs_encode_fh,
 	.fh_to_dentry	= kernfs_fh_to_dentry,
 	.fh_to_parent	= kernfs_fh_to_parent,
 	.get_parent	= kernfs_get_parent_dentry,
 };

 /**
  * kernfs_root_from_sb - determine kernfs_root associated with a super_block
  * @sb: the super_block in question
  *
  * Return: the kernfs_root associated with @sb.  If @sb is not a kernfs one,
  * %NULL is returned.
  */
 struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
 {
 	if (sb->s_op == &kernfs_sops)
 		return kernfs_info(sb)->root;
 	return NULL;
 }

 /*
  * find the next ancestor in the path down to @child, where @parent was the
  * ancestor whose descendant we want to find.
  *
  * Say the path is /a/b/c/d.  @child is d, @parent is %NULL.  We return the root
  * node.  If @parent is b, then we return the node for c.
  * Passing in d as @parent is not ok.
  */
 static struct kernfs_node *find_next_ancestor(struct kernfs_node *child,
 					      struct kernfs_node *parent)
 {
 	if (child == parent) {
 		pr_crit_once("BUG in find_next_ancestor: called with parent == child");
 		return NULL;
 	}

 	while (child->parent != parent) {
 		if (!child->parent)
 			return NULL;
 		child = child->parent;
 	}

 	return child;
 }

 /**
  * kernfs_node_dentry - get a dentry for the given kernfs_node
  * @kn: kernfs_node for which a dentry is needed
  * @sb: the kernfs super_block
  *
  * Return: the dentry pointer
  */
 struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
 				  struct super_block *sb)
 {
 	struct dentry *dentry;
 	struct kernfs_node *knparent = NULL;

 	BUG_ON(sb->s_op != &kernfs_sops);

 	dentry = dget(sb->s_root);

 	/* Check if this is the root kernfs_node */
 	if (!kn->parent)
 		return dentry;

 	knparent = find_next_ancestor(kn, NULL);
 	if (WARN_ON(!knparent)) {
 		dput(dentry);
 		return ERR_PTR(-EINVAL);
 	}

 	do {
 		struct dentry *dtmp;
 		struct kernfs_node *kntmp;

 		if (kn == knparent)
 			return dentry;
 		kntmp = find_next_ancestor(kn, knparent);
 		if (WARN_ON(!kntmp)) {
 			dput(dentry);
 			return ERR_PTR(-EINVAL);
 		}
 		dtmp = lookup_positive_unlocked(kntmp->name, dentry,
 					       strlen(kntmp->name));
 		dput(dentry);
 		if (IS_ERR(dtmp))
 			return dtmp;
 		knparent = kntmp;
 		dentry = dtmp;
 	} while (true);
 }

 static int kernfs_fill_super(struct super_block *sb, struct kernfs_fs_context *kfc)
 {
 	struct kernfs_super_info *info = kernfs_info(sb);
 	struct kernfs_root *kf_root = kfc->root;
 	struct inode *inode;
 	struct dentry *root;

 	info->sb = sb;
 	/* Userspace would break if executables or devices appear on sysfs */
 	sb->s_iflags |= SB_I_NOEXEC | SB_I_NODEV;
 	sb->s_blocksize = PAGE_SIZE;
 	sb->s_blocksize_bits = PAGE_SHIFT;
 	sb->s_magic = kfc->magic;
 	sb->s_op = &kernfs_sops;
 	sb->s_xattr = kernfs_xattr_handlers;
 	if (info->root->flags & KERNFS_ROOT_SUPPORT_EXPORTOP)
 		sb->s_export_op = &kernfs_export_ops;
 	sb->s_time_gran = 1;

 	/* sysfs dentries and inodes don't require IO to create */
 	sb->s_shrink.seeks = 0;

 	/* get root inode, initialize and unlock it */
 	down_read(&kf_root->kernfs_rwsem);
 	inode = kernfs_get_inode(sb, info->root->kn);
 	up_read(&kf_root->kernfs_rwsem);
 	if (!inode) {
 		pr_debug("kernfs: could not get root inode\n");
 		return -ENOMEM;
 	}

 	/* instantiate and link root dentry */
 	root = d_make_root(inode);
 	if (!root) {
 		pr_debug("%s: could not get root dentry!\n", __func__);
 		return -ENOMEM;
 	}
 	sb->s_root = root;
 	sb->s_d_op = &kernfs_dops;
 	return 0;
 }

 static int kernfs_test_super(struct super_block *sb, struct fs_context *fc)
 {
 	struct kernfs_super_info *sb_info = kernfs_info(sb);
 	struct kernfs_super_info *info = fc->s_fs_info;

 	return sb_info->root == info->root && sb_info->ns == info->ns;
 }

 static int kernfs_set_super(struct super_block *sb, struct fs_context *fc)
 {
 	struct kernfs_fs_context *kfc = fc->fs_private;

 	kfc->ns_tag = NULL;
 	return set_anon_super_fc(sb, fc);
 }

 /**
  * kernfs_super_ns - determine the namespace tag of a kernfs super_block
  * @sb: super_block of interest
  *
  * Return: the namespace tag associated with kernfs super_block @sb.
  */
 const void *kernfs_super_ns(struct super_block *sb)
 {
 	struct kernfs_super_info *info = kernfs_info(sb);

 	return info->ns;
 }

 /**
  * kernfs_get_tree - kernfs filesystem access/retrieval helper
  * @fc: The filesystem context.
  *
  * This is to be called from each kernfs user's fs_context->ops->get_tree()
  * implementation, which should set the specified ->@fs_type and ->@flags, and
  * specify the hierarchy and namespace tag to mount via ->@root and ->@ns,
  * respectively.
  *
  * Return: %0 on success, -errno on failure.
  */
 int kernfs_get_tree(struct fs_context *fc)
 {
 	struct kernfs_fs_context *kfc = fc->fs_private;
 	struct super_block *sb;
 	struct kernfs_super_info *info;
 	int error;

 	info = kzalloc(sizeof(*info), GFP_KERNEL);
 	if (!info)
 		return -ENOMEM;

 	info->root = kfc->root;
 	info->ns = kfc->ns_tag;
 	INIT_LIST_HEAD(&info->node);

 	fc->s_fs_info = info;
 	sb = sget_fc(fc, kernfs_test_super, kernfs_set_super);
 	if (IS_ERR(sb))
 		return PTR_ERR(sb);

 	if (!sb->s_root) {
 		struct kernfs_super_info *info = kernfs_info(sb);
 		struct kernfs_root *root = kfc->root;

 		kfc->new_sb_created = true;

 		error = kernfs_fill_super(sb, kfc);
 		if (error) {
 			deactivate_locked_super(sb);
 			return error;
 		}
 		sb->s_flags |= SB_ACTIVE;

 		down_write(&root->kernfs_rwsem);
 		list_add(&info->node, &info->root->supers);
 		up_write(&root->kernfs_rwsem);
 	}

 	fc->root = dget(sb->s_root);
 	return 0;
 }

 void kernfs_free_fs_context(struct fs_context *fc)
 {
 	/* Note that we don't deal with kfc->ns_tag here. */
 	kfree(fc->s_fs_info);
 	fc->s_fs_info = NULL;
 }

 /**
  * kernfs_kill_sb - kill_sb for kernfs
  * @sb: super_block being killed
  *
  * This can be used directly for file_system_type->kill_sb().  If a kernfs
  * user needs extra cleanup, it can implement its own kill_sb() and call
  * this function at the end.
  */
 void kernfs_kill_sb(struct super_block *sb)
 {
 	struct kernfs_super_info *info = kernfs_info(sb);
 	struct kernfs_root *root = info->root;

 	down_write(&root->kernfs_rwsem);
 	list_del(&info->node);
 	up_write(&root->kernfs_rwsem);

 	/*
 	 * Remove the superblock from fs_supers/s_instances
 	 * so we can't find it, before freeing kernfs_super_info.
 	 */
 	kill_anon_super(sb);
 	kfree(info);
 }

 static void __init kernfs_mutex_init(void)
 {
 	int count;

 	for (count = 0; count < NR_KERNFS_LOCKS; count++)
 		mutex_init(&kernfs_locks->open_file_mutex[count]);
 }

 static void __init kernfs_lock_init(void)
 {
 	kernfs_locks = kmalloc(sizeof(struct kernfs_global_locks), GFP_KERNEL);
 	WARN_ON(!kernfs_locks);

 	kernfs_mutex_init();
 }

 void __init kernfs_init(void)
 {
 	kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
 					      sizeof(struct kernfs_node),
 					      0, SLAB_PANIC, NULL);

 	/* Creates slab cache for kernfs inode attributes */
 	kernfs_iattrs_cache  = kmem_cache_create("kernfs_iattrs_cache",
 					      sizeof(struct kernfs_iattrs),
 					      0, SLAB_PANIC, NULL);

 	kernfs_lock_init();
 }
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* fs/kernfs/mount.c - kernfs mount 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/fs.h>
	#include <linux/mount.h>
	#include <linux/init.h>
	#include <linux/magic.h>
	#include <linux/slab.h>
	#include <linux/pagemap.h>
	#include <linux/namei.h>
	#include <linux/seq_file.h>
	#include <linux/exportfs.h>

	#include "kernfs-internal.h"

	struct kmem_cache kernfs_node_cache, kernfs_iattrs_cache;
	struct kernfs_global_locks *kernfs_locks;

	static int kernfs_sop_show_options(struct seq_file sf, struct dentry dentry)
	{
	struct kernfs_root *root = kernfs_root(kernfs_dentry_node(dentry));
	struct kernfs_syscall_ops *scops = root->syscall_ops;

	if (scops && scops->show_options)
	return scops->show_options(sf, root);
	return 0;
	}

	static int kernfs_sop_show_path(struct seq_file sf, struct dentry dentry)
	{
	struct kernfs_node *node = kernfs_dentry_node(dentry);
	struct kernfs_root *root = kernfs_root(node);
	struct kernfs_syscall_ops *scops = root->syscall_ops;

	if (scops && scops->show_path)
	return scops->show_path(sf, node, root);

	seq_dentry(sf, dentry, " \t\n\\");
	return 0;
	}

	const struct super_operations kernfs_sops = {
	.statfs = simple_statfs,
	.drop_inode = generic_delete_inode,
	.evict_inode = kernfs_evict_inode,

	.show_options = kernfs_sop_show_options,
	.show_path = kernfs_sop_show_path,
	};

	static int kernfs_encode_fh(struct inode inode, __u32 fh, int *max_len,
	struct inode *parent)
	{
	struct kernfs_node *kn = inode->i_private;

	if (*max_len < 2) {
	*max_len = 2;
	return FILEID_INVALID;
	}

	*max_len = 2;
	(u64 )fh = kn->id;
	return FILEID_KERNFS;
	}

	static struct dentry __kernfs_fh_to_dentry(struct super_block sb,
	struct fid *fid, int fh_len,
	int fh_type, bool get_parent)
	{
	struct kernfs_super_info *info = kernfs_info(sb);
	struct kernfs_node *kn;
	struct inode *inode;
	u64 id;

	if (fh_len < 2)
	return NULL;

	switch (fh_type) {
	case FILEID_KERNFS:
	id = (u64 )fid;
	break;
	case FILEID_INO32_GEN:
	case FILEID_INO32_GEN_PARENT:
	/*
	* blk_log_action() exposes "LOW32,HIGH32" pair without
	* type and userland can call us with generic fid
	* constructed from them. Combine it back to ID. See
	* blk_log_action().
	*/
	id = ((u64)fid->i32.gen << 32) \| fid->i32.ino;
	break;
	default:
	return NULL;
	}

	kn = kernfs_find_and_get_node_by_id(info->root, id);
	if (!kn)
	return ERR_PTR(-ESTALE);

	if (get_parent) {
	struct kernfs_node *parent;

	parent = kernfs_get_parent(kn);
	kernfs_put(kn);
	kn = parent;
	if (!kn)
	return ERR_PTR(-ESTALE);
	}

	inode = kernfs_get_inode(sb, kn);
	kernfs_put(kn);
	if (!inode)
	return ERR_PTR(-ESTALE);

	return d_obtain_alias(inode);
	}

	static struct dentry kernfs_fh_to_dentry(struct super_block sb,
	struct fid *fid, int fh_len,
	int fh_type)
	{
	return __kernfs_fh_to_dentry(sb, fid, fh_len, fh_type, false);
	}

	static struct dentry kernfs_fh_to_parent(struct super_block sb,
	struct fid *fid, int fh_len,
	int fh_type)
	{
	return __kernfs_fh_to_dentry(sb, fid, fh_len, fh_type, true);
	}

	static struct dentry kernfs_get_parent_dentry(struct dentry child)
	{
	struct kernfs_node *kn = kernfs_dentry_node(child);

	return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent));
	}

	static const struct export_operations kernfs_export_ops = {
	.encode_fh = kernfs_encode_fh,
	.fh_to_dentry = kernfs_fh_to_dentry,
	.fh_to_parent = kernfs_fh_to_parent,
	.get_parent = kernfs_get_parent_dentry,
	};

	/**
	* kernfs_root_from_sb - determine kernfs_root associated with a super_block
	* @sb: the super_block in question
	*
	* Return: the kernfs_root associated with @sb. If @sb is not a kernfs one,
	* %NULL is returned.
	*/
	struct kernfs_root kernfs_root_from_sb(struct super_block sb)
	{
	if (sb->s_op == &kernfs_sops)
	return kernfs_info(sb)->root;
	return NULL;
	}

	/*
	* find the next ancestor in the path down to @child, where @parent was the
	* ancestor whose descendant we want to find.
	*
	* Say the path is /a/b/c/d. @child is d, @parent is %NULL. We return the root
	* node. If @parent is b, then we return the node for c.
	* Passing in d as @parent is not ok.
	*/
	static struct kernfs_node find_next_ancestor(struct kernfs_node child,
	struct kernfs_node *parent)
	{
	if (child == parent) {
	pr_crit_once("BUG in find_next_ancestor: called with parent == child");
	return NULL;
	}

	while (child->parent != parent) {
	if (!child->parent)
	return NULL;
	child = child->parent;
	}

	return child;
	}

	/**
	* kernfs_node_dentry - get a dentry for the given kernfs_node
	* @kn: kernfs_node for which a dentry is needed
	* @sb: the kernfs super_block
	*
	* Return: the dentry pointer
	*/
	struct dentry kernfs_node_dentry(struct kernfs_node kn,
	struct super_block *sb)
	{
	struct dentry *dentry;
	struct kernfs_node *knparent = NULL;

	BUG_ON(sb->s_op != &kernfs_sops);

	dentry = dget(sb->s_root);

	/* Check if this is the root kernfs_node */
	if (!kn->parent)
	return dentry;

	knparent = find_next_ancestor(kn, NULL);
	if (WARN_ON(!knparent)) {
	dput(dentry);
	return ERR_PTR(-EINVAL);
	}

	do {
	struct dentry *dtmp;
	struct kernfs_node *kntmp;

	if (kn == knparent)
	return dentry;
	kntmp = find_next_ancestor(kn, knparent);
	if (WARN_ON(!kntmp)) {
	dput(dentry);
	return ERR_PTR(-EINVAL);
	}
	dtmp = lookup_positive_unlocked(kntmp->name, dentry,
	strlen(kntmp->name));
	dput(dentry);
	if (IS_ERR(dtmp))
	return dtmp;
	knparent = kntmp;
	dentry = dtmp;
	} while (true);
	}

	static int kernfs_fill_super(struct super_block sb, struct kernfs_fs_context kfc)
	{
	struct kernfs_super_info *info = kernfs_info(sb);
	struct kernfs_root *kf_root = kfc->root;
	struct inode *inode;
	struct dentry *root;

	info->sb = sb;
	/* Userspace would break if executables or devices appear on sysfs */
	sb->s_iflags \|= SB_I_NOEXEC \| SB_I_NODEV;
	sb->s_blocksize = PAGE_SIZE;
	sb->s_blocksize_bits = PAGE_SHIFT;
	sb->s_magic = kfc->magic;
	sb->s_op = &kernfs_sops;
	sb->s_xattr = kernfs_xattr_handlers;
	if (info->root->flags & KERNFS_ROOT_SUPPORT_EXPORTOP)
	sb->s_export_op = &kernfs_export_ops;
	sb->s_time_gran = 1;

	/* sysfs dentries and inodes don't require IO to create */
	sb->s_shrink.seeks = 0;

	/* get root inode, initialize and unlock it */
	down_read(&kf_root->kernfs_rwsem);
	inode = kernfs_get_inode(sb, info->root->kn);
	up_read(&kf_root->kernfs_rwsem);
	if (!inode) {
	pr_debug("kernfs: could not get root inode\n");
	return -ENOMEM;
	}

	/* instantiate and link root dentry */
	root = d_make_root(inode);
	if (!root) {
	pr_debug("%s: could not get root dentry!\n", __func__);
	return -ENOMEM;
	}
	sb->s_root = root;
	sb->s_d_op = &kernfs_dops;
	return 0;
	}

	static int kernfs_test_super(struct super_block sb, struct fs_context fc)
	{
	struct kernfs_super_info *sb_info = kernfs_info(sb);
	struct kernfs_super_info *info = fc->s_fs_info;

	return sb_info->root == info->root && sb_info->ns == info->ns;
	}

	static int kernfs_set_super(struct super_block sb, struct fs_context fc)
	{
	struct kernfs_fs_context *kfc = fc->fs_private;

	kfc->ns_tag = NULL;
	return set_anon_super_fc(sb, fc);
	}

	/**
	* kernfs_super_ns - determine the namespace tag of a kernfs super_block
	* @sb: super_block of interest
	*
	* Return: the namespace tag associated with kernfs super_block @sb.
	*/
	const void kernfs_super_ns(struct super_block sb)
	{
	struct kernfs_super_info *info = kernfs_info(sb);

	return info->ns;
	}

	/**
	* kernfs_get_tree - kernfs filesystem access/retrieval helper
	* @fc: The filesystem context.
	*
	* This is to be called from each kernfs user's fs_context->ops->get_tree()
	* implementation, which should set the specified ->@fs_type and ->@flags, and
	* specify the hierarchy and namespace tag to mount via ->@root and ->@ns,
	* respectively.
	*
	* Return: %0 on success, -errno on failure.
	*/
	int kernfs_get_tree(struct fs_context *fc)
	{
	struct kernfs_fs_context *kfc = fc->fs_private;
	struct super_block *sb;
	struct kernfs_super_info *info;
	int error;

	info = kzalloc(sizeof(*info), GFP_KERNEL);
	if (!info)
	return -ENOMEM;

	info->root = kfc->root;
	info->ns = kfc->ns_tag;
	INIT_LIST_HEAD(&info->node);

	fc->s_fs_info = info;
	sb = sget_fc(fc, kernfs_test_super, kernfs_set_super);
	if (IS_ERR(sb))
	return PTR_ERR(sb);

	if (!sb->s_root) {
	struct kernfs_super_info *info = kernfs_info(sb);
	struct kernfs_root *root = kfc->root;

	kfc->new_sb_created = true;

	error = kernfs_fill_super(sb, kfc);
	if (error) {
	deactivate_locked_super(sb);
	return error;
	}
	sb->s_flags \|= SB_ACTIVE;

	down_write(&root->kernfs_rwsem);
	list_add(&info->node, &info->root->supers);
	up_write(&root->kernfs_rwsem);
	}

	fc->root = dget(sb->s_root);
	return 0;
	}

	void kernfs_free_fs_context(struct fs_context *fc)
	{
	/* Note that we don't deal with kfc->ns_tag here. */
	kfree(fc->s_fs_info);
	fc->s_fs_info = NULL;
	}

	/**
	* kernfs_kill_sb - kill_sb for kernfs
	* @sb: super_block being killed
	*
	* This can be used directly for file_system_type->kill_sb(). If a kernfs
	* user needs extra cleanup, it can implement its own kill_sb() and call
	* this function at the end.
	*/
	void kernfs_kill_sb(struct super_block *sb)
	{
	struct kernfs_super_info *info = kernfs_info(sb);
	struct kernfs_root *root = info->root;

	down_write(&root->kernfs_rwsem);
	list_del(&info->node);
	up_write(&root->kernfs_rwsem);

	/*
	* Remove the superblock from fs_supers/s_instances
	* so we can't find it, before freeing kernfs_super_info.
	*/
	kill_anon_super(sb);
	kfree(info);
	}

	static void __init kernfs_mutex_init(void)
	{
	int count;

	for (count = 0; count < NR_KERNFS_LOCKS; count++)
	mutex_init(&kernfs_locks->open_file_mutex[count]);
	}

	static void __init kernfs_lock_init(void)
	{
	kernfs_locks = kmalloc(sizeof(struct kernfs_global_locks), GFP_KERNEL);
	WARN_ON(!kernfs_locks);

	kernfs_mutex_init();
	}

	void __init kernfs_init(void)
	{
	kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
	sizeof(struct kernfs_node),
	0, SLAB_PANIC, NULL);

	/* Creates slab cache for kernfs inode attributes */
	kernfs_iattrs_cache = kmem_cache_create("kernfs_iattrs_cache",
	sizeof(struct kernfs_iattrs),
	0, SLAB_PANIC, NULL);

	kernfs_lock_init();
	}