[linux-2.6-block.git] / fs / kernfs / mount.c

// 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;

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,
};

/*
 * Similar to kernfs_fh_get_inode, this one gets kernfs node from inode
 * number and generation
 */
struct kernfs_node *kernfs_get_node_by_id(struct kernfs_root *root,
	const union kernfs_node_id *id)
{
	struct kernfs_node *kn;

	kn = kernfs_find_and_get_node_by_ino(root, id->ino);
	if (!kn)
		return NULL;
	if (kn->id.generation != id->generation) {
		kernfs_put(kn);
		return NULL;
	}
	return kn;
}

static struct inode *kernfs_fh_get_inode(struct super_block *sb,
		u64 ino, u32 generation)
{
	struct kernfs_super_info *info = kernfs_info(sb);
	struct inode *inode;
	struct kernfs_node *kn;

	if (ino == 0)
		return ERR_PTR(-ESTALE);

	kn = kernfs_find_and_get_node_by_ino(info->root, ino);
	if (!kn)
		return ERR_PTR(-ESTALE);
	inode = kernfs_get_inode(sb, kn);
	kernfs_put(kn);
	if (!inode)
		return ERR_PTR(-ESTALE);

	if (generation && inode->i_generation != generation) {
		/* we didn't find the right inode.. */
		iput(inode);
		return ERR_PTR(-ESTALE);
	}
	return inode;
}

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

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

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 = {
	.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
 */
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_one_len_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 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 */
	mutex_lock(&kernfs_mutex);
	inode = kernfs_get_inode(sb, info->root->kn);
	mutex_unlock(&kernfs_mutex);
	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.
 */
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);

		kfc->new_sb_created = true;

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

		mutex_lock(&kernfs_mutex);
		list_add(&info->node, &info->root->supers);
		mutex_unlock(&kernfs_mutex);
	}

	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);

	mutex_lock(&kernfs_mutex);
	list_del(&info->node);
	mutex_unlock(&kernfs_mutex);

	/*
	 * 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);
}

void __init kernfs_init(void)
{

	/*
	 * the slab is freed in RCU context, so kernfs_find_and_get_node_by_ino
	 * can access the slab lock free. This could introduce stale nodes,
	 * please see how kernfs_find_and_get_node_by_ino filters out stale
	 * nodes.
	 */
	kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
					      sizeof(struct kernfs_node),
					      0,
					      SLAB_PANIC | SLAB_TYPESAFE_BY_RCU,
					      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);
}
Commit	Line	Data
55716d26	1	// SPDX-License-Identifier: GPL-2.0-only
b8441ed2 TH	2	/*
	3	* fs/kernfs/mount.c - kernfs mount implementation
	4	*
	5	* Copyright (c) 2001-3 Patrick Mochel
	6	* Copyright (c) 2007 SUSE Linux Products GmbH
	7	* Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
b8441ed2	8	*/
fa736a95 TH	9
	10	#include <linux/fs.h>
	11	#include <linux/mount.h>
	12	#include <linux/init.h>
	13	#include <linux/magic.h>
	14	#include <linux/slab.h>
	15	#include <linux/pagemap.h>
fb3c8315	16	#include <linux/namei.h>
4f41fc59	17	#include <linux/seq_file.h>
aa818825	18	#include <linux/exportfs.h>
fa736a95 TH	19
	20	#include "kernfs-internal.h"
	21
26e28d68	22	struct kmem_cache kernfs_node_cache, kernfs_iattrs_cache;
fa736a95	23
6a7fed4e TH	24	static int kernfs_sop_show_options(struct seq_file sf, struct dentry dentry)
6a7fed4e TH	25	{
319ba91d	26	struct kernfs_root *root = kernfs_root(kernfs_dentry_node(dentry));
6a7fed4e TH	27	struct kernfs_syscall_ops *scops = root->syscall_ops;
	28
	29	if (scops && scops->show_options)
	30	return scops->show_options(sf, root);
	31	return 0;
	32	}
	33
4f41fc59 SH	34	static int kernfs_sop_show_path(struct seq_file sf, struct dentry dentry)
4f41fc59 SH	35	{
319ba91d	36	struct kernfs_node *node = kernfs_dentry_node(dentry);
4f41fc59 SH	37	struct kernfs_root *root = kernfs_root(node);
	38	struct kernfs_syscall_ops *scops = root->syscall_ops;
	39
	40	if (scops && scops->show_path)
	41	return scops->show_path(sf, node, root);
	42
3cc9b23c SH	43	seq_dentry(sf, dentry, " \t\n\\");
3cc9b23c SH	44	return 0;
4f41fc59 SH	45	}
4f41fc59 SH	46
f41c5934	47	const struct super_operations kernfs_sops = {
fa736a95 TH	48	.statfs = simple_statfs,
fa736a95 TH	49	.drop_inode = generic_delete_inode,
c637b8ac	50	.evict_inode = kernfs_evict_inode,
6a7fed4e	51
6a7fed4e	52	.show_options = kernfs_sop_show_options,
4f41fc59	53	.show_path = kernfs_sop_show_path,
fa736a95 TH	54	};
fa736a95 TH	55
69fd5c39 SL	56	/*
	57	* Similar to kernfs_fh_get_inode, this one gets kernfs node from inode
	58	* number and generation
	59	*/
	60	struct kernfs_node kernfs_get_node_by_id(struct kernfs_root root,
	61	const union kernfs_node_id *id)
	62	{
	63	struct kernfs_node *kn;
	64
	65	kn = kernfs_find_and_get_node_by_ino(root, id->ino);
	66	if (!kn)
	67	return NULL;
	68	if (kn->id.generation != id->generation) {
	69	kernfs_put(kn);
	70	return NULL;
	71	}
	72	return kn;
	73	}
	74
aa818825 SL	75	static struct inode kernfs_fh_get_inode(struct super_block sb,
	76	u64 ino, u32 generation)
	77	{
	78	struct kernfs_super_info *info = kernfs_info(sb);
	79	struct inode *inode;
	80	struct kernfs_node *kn;
	81
	82	if (ino == 0)
	83	return ERR_PTR(-ESTALE);
	84
	85	kn = kernfs_find_and_get_node_by_ino(info->root, ino);
	86	if (!kn)
	87	return ERR_PTR(-ESTALE);
	88	inode = kernfs_get_inode(sb, kn);
	89	kernfs_put(kn);
ef13ecbc DC	90	if (!inode)
ef13ecbc DC	91	return ERR_PTR(-ESTALE);
aa818825 SL	92
	93	if (generation && inode->i_generation != generation) {
	94	/* we didn't find the right inode.. */
	95	iput(inode);
	96	return ERR_PTR(-ESTALE);
	97	}
	98	return inode;
	99	}
	100
	101	static struct dentry kernfs_fh_to_dentry(struct super_block sb, struct fid *fid,
	102	int fh_len, int fh_type)
	103	{
	104	return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
	105	kernfs_fh_get_inode);
	106	}
	107
	108	static struct dentry kernfs_fh_to_parent(struct super_block sb, struct fid *fid,
	109	int fh_len, int fh_type)
	110	{
	111	return generic_fh_to_parent(sb, fid, fh_len, fh_type,
	112	kernfs_fh_get_inode);
	113	}
	114
	115	static struct dentry kernfs_get_parent_dentry(struct dentry child)
	116	{
	117	struct kernfs_node *kn = kernfs_dentry_node(child);
	118
	119	return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent));
	120	}
	121
	122	static const struct export_operations kernfs_export_ops = {
	123	.fh_to_dentry = kernfs_fh_to_dentry,
	124	.fh_to_parent = kernfs_fh_to_parent,
	125	.get_parent = kernfs_get_parent_dentry,
	126	};
	127
0c23b225 TH	128	/**
	129	* kernfs_root_from_sb - determine kernfs_root associated with a super_block
	130	* @sb: the super_block in question
	131	*
	132	* Return the kernfs_root associated with @sb. If @sb is not a kernfs one,
	133	* %NULL is returned.
	134	*/
	135	struct kernfs_root kernfs_root_from_sb(struct super_block sb)
	136	{
	137	if (sb->s_op == &kernfs_sops)
	138	return kernfs_info(sb)->root;
	139	return NULL;
	140	}
	141
fb3c8315 AK	142	/*
	143	* find the next ancestor in the path down to @child, where @parent was the
	144	* ancestor whose descendant we want to find.
	145	*
	146	* Say the path is /a/b/c/d. @child is d, @parent is NULL. We return the root
	147	* node. If @parent is b, then we return the node for c.
	148	* Passing in d as @parent is not ok.
	149	*/
	150	static struct kernfs_node find_next_ancestor(struct kernfs_node child,
	151	struct kernfs_node *parent)
	152	{
	153	if (child == parent) {
	154	pr_crit_once("BUG in find_next_ancestor: called with parent == child");
	155	return NULL;
	156	}
	157
	158	while (child->parent != parent) {
	159	if (!child->parent)
	160	return NULL;
	161	child = child->parent;
	162	}
	163
	164	return child;
	165	}
	166
	167	/**
	168	* kernfs_node_dentry - get a dentry for the given kernfs_node
	169	* @kn: kernfs_node for which a dentry is needed
	170	* @sb: the kernfs super_block
	171	*/
	172	struct dentry kernfs_node_dentry(struct kernfs_node kn,
	173	struct super_block *sb)
	174	{
	175	struct dentry *dentry;
	176	struct kernfs_node *knparent = NULL;
	177
	178	BUG_ON(sb->s_op != &kernfs_sops);
	179
	180	dentry = dget(sb->s_root);
	181
	182	/* Check if this is the root kernfs_node */
	183	if (!kn->parent)
	184	return dentry;
	185
	186	knparent = find_next_ancestor(kn, NULL);
399504e2 AV	187	if (WARN_ON(!knparent)) {
399504e2 AV	188	dput(dentry);
fb3c8315	189	return ERR_PTR(-EINVAL);
399504e2	190	}
fb3c8315 AK	191
	192	do {
	193	struct dentry *dtmp;
	194	struct kernfs_node *kntmp;
	195
	196	if (kn == knparent)
	197	return dentry;
	198	kntmp = find_next_ancestor(kn, knparent);
399504e2 AV	199	if (WARN_ON(!kntmp)) {
399504e2 AV	200	dput(dentry);
fb3c8315	201	return ERR_PTR(-EINVAL);
399504e2	202	}
779b8391 AV	203	dtmp = lookup_one_len_unlocked(kntmp->name, dentry,
779b8391 AV	204	strlen(kntmp->name));
fb3c8315 AK	205	dput(dentry);
	206	if (IS_ERR(dtmp))
	207	return dtmp;
	208	knparent = kntmp;
	209	dentry = dtmp;
	210	} while (true);
	211	}
	212
23bf1b6b	213	static int kernfs_fill_super(struct super_block sb, struct kernfs_fs_context kfc)
fa736a95	214	{
c525aadd	215	struct kernfs_super_info *info = kernfs_info(sb);
fa736a95 TH	216	struct inode *inode;
	217	struct dentry *root;
	218
7d568a83	219	info->sb = sb;
a2982cc9 EB	220	/* Userspace would break if executables or devices appear on sysfs */
a2982cc9 EB	221	sb->s_iflags \|= SB_I_NOEXEC \| SB_I_NODEV;
09cbfeaf KS	222	sb->s_blocksize = PAGE_SIZE;
09cbfeaf KS	223	sb->s_blocksize_bits = PAGE_SHIFT;
23bf1b6b	224	sb->s_magic = kfc->magic;
a797bfc3	225	sb->s_op = &kernfs_sops;
e72a1a8b	226	sb->s_xattr = kernfs_xattr_handlers;
aa818825 SL	227	if (info->root->flags & KERNFS_ROOT_SUPPORT_EXPORTOP)
aa818825 SL	228	sb->s_export_op = &kernfs_export_ops;
fa736a95 TH	229	sb->s_time_gran = 1;
fa736a95 TH	230
4b85afbd JW	231	/* sysfs dentries and inodes don't require IO to create */
	232	sb->s_shrink.seeks = 0;
	233
fa736a95	234	/* get root inode, initialize and unlock it */
a797bfc3	235	mutex_lock(&kernfs_mutex);
c637b8ac	236	inode = kernfs_get_inode(sb, info->root->kn);
a797bfc3	237	mutex_unlock(&kernfs_mutex);
fa736a95	238	if (!inode) {
c637b8ac	239	pr_debug("kernfs: could not get root inode\n");
fa736a95 TH	240	return -ENOMEM;
	241	}
	242
	243	/* instantiate and link root dentry */
	244	root = d_make_root(inode);
	245	if (!root) {
	246	pr_debug("%s: could not get root dentry!\n", __func__);
	247	return -ENOMEM;
	248	}
fa736a95	249	sb->s_root = root;
a797bfc3	250	sb->s_d_op = &kernfs_dops;
fa736a95 TH	251	return 0;
	252	}
	253
23bf1b6b	254	static int kernfs_test_super(struct super_block sb, struct fs_context fc)
fa736a95	255	{
c525aadd	256	struct kernfs_super_info *sb_info = kernfs_info(sb);
23bf1b6b	257	struct kernfs_super_info *info = fc->s_fs_info;
fa736a95 TH	258
	259	return sb_info->root == info->root && sb_info->ns == info->ns;
	260	}
	261
23bf1b6b	262	static int kernfs_set_super(struct super_block sb, struct fs_context fc)
fa736a95	263	{
23bf1b6b DH	264	struct kernfs_fs_context *kfc = fc->fs_private;
	265
	266	kfc->ns_tag = NULL;
	267	return set_anon_super_fc(sb, fc);
fa736a95 TH	268	}
	269
	270	/**
	271	* kernfs_super_ns - determine the namespace tag of a kernfs super_block
	272	* @sb: super_block of interest
	273	*
	274	* Return the namespace tag associated with kernfs super_block @sb.
	275	*/
	276	const void kernfs_super_ns(struct super_block sb)
	277	{
c525aadd	278	struct kernfs_super_info *info = kernfs_info(sb);
fa736a95 TH	279
	280	return info->ns;
	281	}
	282
	283	/**
23bf1b6b DH	284	* kernfs_get_tree - kernfs filesystem access/retrieval helper
23bf1b6b DH	285	* @fc: The filesystem context.
fa736a95	286	*
23bf1b6b DH	287	* This is to be called from each kernfs user's fs_context->ops->get_tree()
	288	* implementation, which should set the specified ->@fs_type and ->@flags, and
	289	* specify the hierarchy and namespace tag to mount via ->@root and ->@ns,
	290	* respectively.
fa736a95	291	*/
23bf1b6b	292	int kernfs_get_tree(struct fs_context *fc)
fa736a95	293	{
23bf1b6b	294	struct kernfs_fs_context *kfc = fc->fs_private;
fa736a95	295	struct super_block *sb;
c525aadd	296	struct kernfs_super_info *info;
fa736a95 TH	297	int error;
	298
	299	info = kzalloc(sizeof(*info), GFP_KERNEL);
	300	if (!info)
23bf1b6b	301	return -ENOMEM;
fa736a95	302
23bf1b6b DH	303	info->root = kfc->root;
23bf1b6b DH	304	info->ns = kfc->ns_tag;
82382ace	305	INIT_LIST_HEAD(&info->node);
fa736a95	306
23bf1b6b DH	307	fc->s_fs_info = info;
23bf1b6b DH	308	sb = sget_fc(fc, kernfs_test_super, kernfs_set_super);
fa736a95	309	if (IS_ERR(sb))
23bf1b6b	310	return PTR_ERR(sb);
fed95bab	311
fa736a95	312	if (!sb->s_root) {
7d568a83 TH	313	struct kernfs_super_info *info = kernfs_info(sb);
7d568a83 TH	314
23bf1b6b DH	315	kfc->new_sb_created = true;
	316
	317	error = kernfs_fill_super(sb, kfc);
fa736a95 TH	318	if (error) {
fa736a95 TH	319	deactivate_locked_super(sb);
23bf1b6b	320	return error;
fa736a95	321	}
1751e8a6	322	sb->s_flags \|= SB_ACTIVE;
7d568a83 TH	323
7d568a83 TH	324	mutex_lock(&kernfs_mutex);
23bf1b6b	325	list_add(&info->node, &info->root->supers);
7d568a83	326	mutex_unlock(&kernfs_mutex);
fa736a95 TH	327	}
fa736a95 TH	328
23bf1b6b DH	329	fc->root = dget(sb->s_root);
	330	return 0;
	331	}
	332
	333	void kernfs_free_fs_context(struct fs_context *fc)
	334	{
	335	/* Note that we don't deal with kfc->ns_tag here. */
	336	kfree(fc->s_fs_info);
	337	fc->s_fs_info = NULL;
fa736a95 TH	338	}
	339
	340	/**
	341	* kernfs_kill_sb - kill_sb for kernfs
	342	* @sb: super_block being killed
	343	*
	344	* This can be used directly for file_system_type->kill_sb(). If a kernfs
	345	* user needs extra cleanup, it can implement its own kill_sb() and call
	346	* this function at the end.
	347	*/
	348	void kernfs_kill_sb(struct super_block *sb)
	349	{
c525aadd	350	struct kernfs_super_info *info = kernfs_info(sb);
fa736a95	351
7d568a83 TH	352	mutex_lock(&kernfs_mutex);
	353	list_del(&info->node);
	354	mutex_unlock(&kernfs_mutex);
	355
fa736a95 TH	356	/*
fa736a95 TH	357	* Remove the superblock from fs_supers/s_instances
c525aadd	358	* so we can't find it, before freeing kernfs_super_info.
fa736a95 TH	359	*/
	360	kill_anon_super(sb);
	361	kfree(info);
fa736a95 TH	362	}
	363
	364	void __init kernfs_init(void)
	365	{
ba16b284 SL	366
	367	/*
	368	* the slab is freed in RCU context, so kernfs_find_and_get_node_by_ino
	369	* can access the slab lock free. This could introduce stale nodes,
	370	* please see how kernfs_find_and_get_node_by_ino filters out stale
	371	* nodes.
	372	*/
a797bfc3	373	kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
324a56e1	374	sizeof(struct kernfs_node),
ba16b284 SL	375	0,
	376	SLAB_PANIC \| SLAB_TYPESAFE_BY_RCU,
	377	NULL);
26e28d68 AM	378
	379	/* Creates slab cache for kernfs inode attributes */
	380	kernfs_iattrs_cache = kmem_cache_create("kernfs_iattrs_cache",
	381	sizeof(struct kernfs_iattrs),
	382	0, SLAB_PANIC, NULL);
fa736a95	383	}