[mirror_ubuntu-hirsute-kernel.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,
};

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
 */
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 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)
{
	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);
}
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
33c5ac91 TH	56	static int kernfs_encode_fh(struct inode inode, __u32 fh, int *max_len,
33c5ac91 TH	57	struct inode *parent)
aa818825	58	{
33c5ac91	59	struct kernfs_node *kn = inode->i_private;
aa818825	60
33c5ac91 TH	61	if (*max_len < 2) {
	62	*max_len = 2;
	63	return FILEID_INVALID;
	64	}
aa818825	65
33c5ac91 TH	66	*max_len = 2;
	67	(u64 )fh = kn->id;
	68	return FILEID_KERNFS;
	69	}
	70
	71	static struct dentry __kernfs_fh_to_dentry(struct super_block sb,
	72	struct fid *fid, int fh_len,
	73	int fh_type, bool get_parent)
	74	{
	75	struct kernfs_super_info *info = kernfs_info(sb);
	76	struct kernfs_node *kn;
	77	struct inode *inode;
	78	u64 id;
	79
	80	if (fh_len < 2)
	81	return NULL;
	82
	83	switch (fh_type) {
	84	case FILEID_KERNFS:
	85	id = (u64 )fid;
	86	break;
	87	case FILEID_INO32_GEN:
	88	case FILEID_INO32_GEN_PARENT:
	89	/*
40430452 TH	90	* blk_log_action() exposes "LOW32,HIGH32" pair without
	91	* type and userland can call us with generic fid
	92	* constructed from them. Combine it back to ID. See
	93	* blk_log_action().
33c5ac91 TH	94	*/
	95	id = ((u64)fid->i32.gen << 32) \| fid->i32.ino;
	96	break;
	97	default:
	98	return NULL;
	99	}
	100
	101	kn = kernfs_find_and_get_node_by_id(info->root, id);
aa818825 SL	102	if (!kn)
aa818825 SL	103	return ERR_PTR(-ESTALE);
33c5ac91 TH	104
	105	if (get_parent) {
	106	struct kernfs_node *parent;
	107
	108	parent = kernfs_get_parent(kn);
	109	kernfs_put(kn);
	110	kn = parent;
	111	if (!kn)
	112	return ERR_PTR(-ESTALE);
	113	}
	114
aa818825 SL	115	inode = kernfs_get_inode(sb, kn);
aa818825 SL	116	kernfs_put(kn);
ef13ecbc DC	117	if (!inode)
ef13ecbc DC	118	return ERR_PTR(-ESTALE);
aa818825	119
33c5ac91	120	return d_obtain_alias(inode);
aa818825 SL	121	}
aa818825 SL	122
33c5ac91 TH	123	static struct dentry kernfs_fh_to_dentry(struct super_block sb,
	124	struct fid *fid, int fh_len,
	125	int fh_type)
aa818825	126	{
33c5ac91	127	return __kernfs_fh_to_dentry(sb, fid, fh_len, fh_type, false);
aa818825 SL	128	}
aa818825 SL	129
33c5ac91 TH	130	static struct dentry kernfs_fh_to_parent(struct super_block sb,
	131	struct fid *fid, int fh_len,
	132	int fh_type)
aa818825	133	{
33c5ac91	134	return __kernfs_fh_to_dentry(sb, fid, fh_len, fh_type, true);
aa818825 SL	135	}
	136
	137	static struct dentry kernfs_get_parent_dentry(struct dentry child)
	138	{
	139	struct kernfs_node *kn = kernfs_dentry_node(child);
	140
	141	return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent));
	142	}
	143
	144	static const struct export_operations kernfs_export_ops = {
33c5ac91	145	.encode_fh = kernfs_encode_fh,
aa818825 SL	146	.fh_to_dentry = kernfs_fh_to_dentry,
	147	.fh_to_parent = kernfs_fh_to_parent,
	148	.get_parent = kernfs_get_parent_dentry,
	149	};
	150
0c23b225 TH	151	/**
	152	* kernfs_root_from_sb - determine kernfs_root associated with a super_block
	153	* @sb: the super_block in question
	154	*
	155	* Return the kernfs_root associated with @sb. If @sb is not a kernfs one,
	156	* %NULL is returned.
	157	*/
	158	struct kernfs_root kernfs_root_from_sb(struct super_block sb)
	159	{
	160	if (sb->s_op == &kernfs_sops)
	161	return kernfs_info(sb)->root;
	162	return NULL;
	163	}
	164
fb3c8315 AK	165	/*
	166	* find the next ancestor in the path down to @child, where @parent was the
	167	* ancestor whose descendant we want to find.
	168	*
	169	* Say the path is /a/b/c/d. @child is d, @parent is NULL. We return the root
	170	* node. If @parent is b, then we return the node for c.
	171	* Passing in d as @parent is not ok.
	172	*/
	173	static struct kernfs_node find_next_ancestor(struct kernfs_node child,
	174	struct kernfs_node *parent)
	175	{
	176	if (child == parent) {
	177	pr_crit_once("BUG in find_next_ancestor: called with parent == child");
	178	return NULL;
	179	}
	180
	181	while (child->parent != parent) {
	182	if (!child->parent)
	183	return NULL;
	184	child = child->parent;
	185	}
	186
	187	return child;
	188	}
	189
	190	/**
	191	* kernfs_node_dentry - get a dentry for the given kernfs_node
	192	* @kn: kernfs_node for which a dentry is needed
	193	* @sb: the kernfs super_block
	194	*/
	195	struct dentry kernfs_node_dentry(struct kernfs_node kn,
	196	struct super_block *sb)
	197	{
	198	struct dentry *dentry;
	199	struct kernfs_node *knparent = NULL;
	200
	201	BUG_ON(sb->s_op != &kernfs_sops);
	202
	203	dentry = dget(sb->s_root);
	204
	205	/* Check if this is the root kernfs_node */
	206	if (!kn->parent)
	207	return dentry;
	208
	209	knparent = find_next_ancestor(kn, NULL);
399504e2 AV	210	if (WARN_ON(!knparent)) {
399504e2 AV	211	dput(dentry);
fb3c8315	212	return ERR_PTR(-EINVAL);
399504e2	213	}
fb3c8315 AK	214
	215	do {
	216	struct dentry *dtmp;
	217	struct kernfs_node *kntmp;
	218
	219	if (kn == knparent)
	220	return dentry;
	221	kntmp = find_next_ancestor(kn, knparent);
399504e2 AV	222	if (WARN_ON(!kntmp)) {
399504e2 AV	223	dput(dentry);
fb3c8315	224	return ERR_PTR(-EINVAL);
399504e2	225	}
6c2d4798	226	dtmp = lookup_positive_unlocked(kntmp->name, dentry,
779b8391	227	strlen(kntmp->name));
fb3c8315 AK	228	dput(dentry);
	229	if (IS_ERR(dtmp))
	230	return dtmp;
	231	knparent = kntmp;
	232	dentry = dtmp;
	233	} while (true);
	234	}
	235
23bf1b6b	236	static int kernfs_fill_super(struct super_block sb, struct kernfs_fs_context kfc)
fa736a95	237	{
c525aadd	238	struct kernfs_super_info *info = kernfs_info(sb);
fa736a95 TH	239	struct inode *inode;
	240	struct dentry *root;
	241
7d568a83	242	info->sb = sb;
a2982cc9 EB	243	/* Userspace would break if executables or devices appear on sysfs */
a2982cc9 EB	244	sb->s_iflags \|= SB_I_NOEXEC \| SB_I_NODEV;
09cbfeaf KS	245	sb->s_blocksize = PAGE_SIZE;
09cbfeaf KS	246	sb->s_blocksize_bits = PAGE_SHIFT;
23bf1b6b	247	sb->s_magic = kfc->magic;
a797bfc3	248	sb->s_op = &kernfs_sops;
e72a1a8b	249	sb->s_xattr = kernfs_xattr_handlers;
aa818825 SL	250	if (info->root->flags & KERNFS_ROOT_SUPPORT_EXPORTOP)
aa818825 SL	251	sb->s_export_op = &kernfs_export_ops;
fa736a95 TH	252	sb->s_time_gran = 1;
fa736a95 TH	253
4b85afbd JW	254	/* sysfs dentries and inodes don't require IO to create */
	255	sb->s_shrink.seeks = 0;
	256
fa736a95	257	/* get root inode, initialize and unlock it */
a797bfc3	258	mutex_lock(&kernfs_mutex);
c637b8ac	259	inode = kernfs_get_inode(sb, info->root->kn);
a797bfc3	260	mutex_unlock(&kernfs_mutex);
fa736a95	261	if (!inode) {
c637b8ac	262	pr_debug("kernfs: could not get root inode\n");
fa736a95 TH	263	return -ENOMEM;
	264	}
	265
	266	/* instantiate and link root dentry */
	267	root = d_make_root(inode);
	268	if (!root) {
	269	pr_debug("%s: could not get root dentry!\n", __func__);
	270	return -ENOMEM;
	271	}
fa736a95	272	sb->s_root = root;
a797bfc3	273	sb->s_d_op = &kernfs_dops;
fa736a95 TH	274	return 0;
	275	}
	276
23bf1b6b	277	static int kernfs_test_super(struct super_block sb, struct fs_context fc)
fa736a95	278	{
c525aadd	279	struct kernfs_super_info *sb_info = kernfs_info(sb);
23bf1b6b	280	struct kernfs_super_info *info = fc->s_fs_info;
fa736a95 TH	281
	282	return sb_info->root == info->root && sb_info->ns == info->ns;
	283	}
	284
23bf1b6b	285	static int kernfs_set_super(struct super_block sb, struct fs_context fc)
fa736a95	286	{
23bf1b6b DH	287	struct kernfs_fs_context *kfc = fc->fs_private;
	288
	289	kfc->ns_tag = NULL;
	290	return set_anon_super_fc(sb, fc);
fa736a95 TH	291	}
	292
	293	/**
	294	* kernfs_super_ns - determine the namespace tag of a kernfs super_block
	295	* @sb: super_block of interest
	296	*
	297	* Return the namespace tag associated with kernfs super_block @sb.
	298	*/
	299	const void kernfs_super_ns(struct super_block sb)
	300	{
c525aadd	301	struct kernfs_super_info *info = kernfs_info(sb);
fa736a95 TH	302
	303	return info->ns;
	304	}
	305
	306	/**
23bf1b6b DH	307	* kernfs_get_tree - kernfs filesystem access/retrieval helper
23bf1b6b DH	308	* @fc: The filesystem context.
fa736a95	309	*
23bf1b6b DH	310	* This is to be called from each kernfs user's fs_context->ops->get_tree()
	311	* implementation, which should set the specified ->@fs_type and ->@flags, and
	312	* specify the hierarchy and namespace tag to mount via ->@root and ->@ns,
	313	* respectively.
fa736a95	314	*/
23bf1b6b	315	int kernfs_get_tree(struct fs_context *fc)
fa736a95	316	{
23bf1b6b	317	struct kernfs_fs_context *kfc = fc->fs_private;
fa736a95	318	struct super_block *sb;
c525aadd	319	struct kernfs_super_info *info;
fa736a95 TH	320	int error;
	321
	322	info = kzalloc(sizeof(*info), GFP_KERNEL);
	323	if (!info)
23bf1b6b	324	return -ENOMEM;
fa736a95	325
23bf1b6b DH	326	info->root = kfc->root;
23bf1b6b DH	327	info->ns = kfc->ns_tag;
82382ace	328	INIT_LIST_HEAD(&info->node);
fa736a95	329
23bf1b6b DH	330	fc->s_fs_info = info;
23bf1b6b DH	331	sb = sget_fc(fc, kernfs_test_super, kernfs_set_super);
fa736a95	332	if (IS_ERR(sb))
23bf1b6b	333	return PTR_ERR(sb);
fed95bab	334
fa736a95	335	if (!sb->s_root) {
7d568a83 TH	336	struct kernfs_super_info *info = kernfs_info(sb);
7d568a83 TH	337
23bf1b6b DH	338	kfc->new_sb_created = true;
	339
	340	error = kernfs_fill_super(sb, kfc);
fa736a95 TH	341	if (error) {
fa736a95 TH	342	deactivate_locked_super(sb);
23bf1b6b	343	return error;
fa736a95	344	}
1751e8a6	345	sb->s_flags \|= SB_ACTIVE;
7d568a83 TH	346
7d568a83 TH	347	mutex_lock(&kernfs_mutex);
23bf1b6b	348	list_add(&info->node, &info->root->supers);
7d568a83	349	mutex_unlock(&kernfs_mutex);
fa736a95 TH	350	}
fa736a95 TH	351
23bf1b6b DH	352	fc->root = dget(sb->s_root);
	353	return 0;
	354	}
	355
	356	void kernfs_free_fs_context(struct fs_context *fc)
	357	{
	358	/* Note that we don't deal with kfc->ns_tag here. */
	359	kfree(fc->s_fs_info);
	360	fc->s_fs_info = NULL;
fa736a95 TH	361	}
	362
	363	/**
	364	* kernfs_kill_sb - kill_sb for kernfs
	365	* @sb: super_block being killed
	366	*
	367	* This can be used directly for file_system_type->kill_sb(). If a kernfs
	368	* user needs extra cleanup, it can implement its own kill_sb() and call
	369	* this function at the end.
	370	*/
	371	void kernfs_kill_sb(struct super_block *sb)
	372	{
c525aadd	373	struct kernfs_super_info *info = kernfs_info(sb);
fa736a95	374
7d568a83 TH	375	mutex_lock(&kernfs_mutex);
	376	list_del(&info->node);
	377	mutex_unlock(&kernfs_mutex);
	378
fa736a95 TH	379	/*
fa736a95 TH	380	* Remove the superblock from fs_supers/s_instances
c525aadd	381	* so we can't find it, before freeing kernfs_super_info.
fa736a95 TH	382	*/
	383	kill_anon_super(sb);
	384	kfree(info);
fa736a95 TH	385	}
	386
	387	void __init kernfs_init(void)
	388	{
a797bfc3	389	kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
324a56e1	390	sizeof(struct kernfs_node),
b680b081	391	0, SLAB_PANIC, NULL);
26e28d68 AM	392
	393	/* Creates slab cache for kernfs inode attributes */
	394	kernfs_iattrs_cache = kmem_cache_create("kernfs_iattrs_cache",
	395	sizeof(struct kernfs_iattrs),
	396	0, SLAB_PANIC, NULL);
fa736a95	397	}