[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 <linux/uuid.h>
#include <linux/statfs.h>

#include "kernfs-internal.h"

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

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;
}

static int kernfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
	simple_statfs(dentry, buf);
	buf->f_fsid = uuid_to_fsid(dentry->d_sb->s_uuid.b);
	return 0;
}

const struct super_operations kernfs_sops = {
	.statfs		= kernfs_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);
	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;

		uuid_gen(&sb->s_uuid);

		down_write(&root->kernfs_supers_rwsem);
		list_add(&info->node, &info->root->supers);
		up_write(&root->kernfs_supers_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_supers_rwsem);
	list_del(&info->node);
	up_write(&root->kernfs_supers_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();
}
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>
0ce7c12e IB	19	#include <linux/uuid.h>
0ce7c12e IB	20	#include <linux/statfs.h>
fa736a95 TH	21
	22	#include "kernfs-internal.h"
	23
68279f9c AD	24	struct kmem_cache *kernfs_node_cache __ro_after_init;
	25	struct kmem_cache *kernfs_iattrs_cache __ro_after_init;
	26	struct kernfs_global_locks *kernfs_locks __ro_after_init;
fa736a95	27
6a7fed4e TH	28	static int kernfs_sop_show_options(struct seq_file sf, struct dentry dentry)
6a7fed4e TH	29	{
319ba91d	30	struct kernfs_root *root = kernfs_root(kernfs_dentry_node(dentry));
6a7fed4e TH	31	struct kernfs_syscall_ops *scops = root->syscall_ops;
	32
	33	if (scops && scops->show_options)
	34	return scops->show_options(sf, root);
	35	return 0;
	36	}
	37
4f41fc59 SH	38	static int kernfs_sop_show_path(struct seq_file sf, struct dentry dentry)
4f41fc59 SH	39	{
319ba91d	40	struct kernfs_node *node = kernfs_dentry_node(dentry);
4f41fc59 SH	41	struct kernfs_root *root = kernfs_root(node);
	42	struct kernfs_syscall_ops *scops = root->syscall_ops;
	43
	44	if (scops && scops->show_path)
	45	return scops->show_path(sf, node, root);
	46
3cc9b23c SH	47	seq_dentry(sf, dentry, " \t\n\\");
3cc9b23c SH	48	return 0;
4f41fc59 SH	49	}
4f41fc59 SH	50
0ce7c12e IB	51	static int kernfs_statfs(struct dentry dentry, struct kstatfs buf)
	52	{
	53	simple_statfs(dentry, buf);
	54	buf->f_fsid = uuid_to_fsid(dentry->d_sb->s_uuid.b);
	55	return 0;
	56	}
	57
f41c5934	58	const struct super_operations kernfs_sops = {
0ce7c12e	59	.statfs = kernfs_statfs,
fa736a95	60	.drop_inode = generic_delete_inode,
c637b8ac	61	.evict_inode = kernfs_evict_inode,
6a7fed4e	62
6a7fed4e	63	.show_options = kernfs_sop_show_options,
4f41fc59	64	.show_path = kernfs_sop_show_path,
fa736a95 TH	65	};
fa736a95 TH	66
33c5ac91 TH	67	static int kernfs_encode_fh(struct inode inode, __u32 fh, int *max_len,
33c5ac91 TH	68	struct inode *parent)
aa818825	69	{
33c5ac91	70	struct kernfs_node *kn = inode->i_private;
aa818825	71
33c5ac91 TH	72	if (*max_len < 2) {
	73	*max_len = 2;
	74	return FILEID_INVALID;
	75	}
aa818825	76
33c5ac91 TH	77	*max_len = 2;
	78	(u64 )fh = kn->id;
	79	return FILEID_KERNFS;
	80	}
	81
	82	static struct dentry __kernfs_fh_to_dentry(struct super_block sb,
	83	struct fid *fid, int fh_len,
	84	int fh_type, bool get_parent)
	85	{
	86	struct kernfs_super_info *info = kernfs_info(sb);
	87	struct kernfs_node *kn;
	88	struct inode *inode;
	89	u64 id;
	90
	91	if (fh_len < 2)
	92	return NULL;
	93
	94	switch (fh_type) {
	95	case FILEID_KERNFS:
	96	id = (u64 )fid;
	97	break;
	98	case FILEID_INO32_GEN:
	99	case FILEID_INO32_GEN_PARENT:
	100	/*
40430452 TH	101	* blk_log_action() exposes "LOW32,HIGH32" pair without
	102	* type and userland can call us with generic fid
	103	* constructed from them. Combine it back to ID. See
	104	* blk_log_action().
33c5ac91 TH	105	*/
	106	id = ((u64)fid->i32.gen << 32) \| fid->i32.ino;
	107	break;
	108	default:
	109	return NULL;
	110	}
	111
	112	kn = kernfs_find_and_get_node_by_id(info->root, id);
aa818825 SL	113	if (!kn)
aa818825 SL	114	return ERR_PTR(-ESTALE);
33c5ac91 TH	115
	116	if (get_parent) {
	117	struct kernfs_node *parent;
	118
	119	parent = kernfs_get_parent(kn);
	120	kernfs_put(kn);
	121	kn = parent;
	122	if (!kn)
	123	return ERR_PTR(-ESTALE);
	124	}
	125
aa818825 SL	126	inode = kernfs_get_inode(sb, kn);
aa818825 SL	127	kernfs_put(kn);
33c5ac91	128	return d_obtain_alias(inode);
aa818825 SL	129	}
aa818825 SL	130
33c5ac91 TH	131	static struct dentry kernfs_fh_to_dentry(struct super_block sb,
	132	struct fid *fid, int fh_len,
	133	int fh_type)
aa818825	134	{
33c5ac91	135	return __kernfs_fh_to_dentry(sb, fid, fh_len, fh_type, false);
aa818825 SL	136	}
aa818825 SL	137
33c5ac91 TH	138	static struct dentry kernfs_fh_to_parent(struct super_block sb,
	139	struct fid *fid, int fh_len,
	140	int fh_type)
aa818825	141	{
33c5ac91	142	return __kernfs_fh_to_dentry(sb, fid, fh_len, fh_type, true);
aa818825 SL	143	}
	144
	145	static struct dentry kernfs_get_parent_dentry(struct dentry child)
	146	{
	147	struct kernfs_node *kn = kernfs_dentry_node(child);
	148
	149	return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent));
	150	}
	151
	152	static const struct export_operations kernfs_export_ops = {
33c5ac91	153	.encode_fh = kernfs_encode_fh,
aa818825 SL	154	.fh_to_dentry = kernfs_fh_to_dentry,
	155	.fh_to_parent = kernfs_fh_to_parent,
	156	.get_parent = kernfs_get_parent_dentry,
	157	};
	158
0c23b225 TH	159	/**
	160	* kernfs_root_from_sb - determine kernfs_root associated with a super_block
	161	* @sb: the super_block in question
	162	*
24b3e3dd	163	* Return: the kernfs_root associated with @sb. If @sb is not a kernfs one,
0c23b225 TH	164	* %NULL is returned.
	165	*/
	166	struct kernfs_root kernfs_root_from_sb(struct super_block sb)
	167	{
	168	if (sb->s_op == &kernfs_sops)
	169	return kernfs_info(sb)->root;
	170	return NULL;
	171	}
	172
fb3c8315 AK	173	/*
	174	* find the next ancestor in the path down to @child, where @parent was the
	175	* ancestor whose descendant we want to find.
	176	*
24b3e3dd	177	* Say the path is /a/b/c/d. @child is d, @parent is %NULL. We return the root
fb3c8315 AK	178	* node. If @parent is b, then we return the node for c.
	179	* Passing in d as @parent is not ok.
	180	*/
	181	static struct kernfs_node find_next_ancestor(struct kernfs_node child,
	182	struct kernfs_node *parent)
	183	{
	184	if (child == parent) {
	185	pr_crit_once("BUG in find_next_ancestor: called with parent == child");
	186	return NULL;
	187	}
	188
	189	while (child->parent != parent) {
	190	if (!child->parent)
	191	return NULL;
	192	child = child->parent;
	193	}
	194
	195	return child;
	196	}
	197
	198	/**
	199	* kernfs_node_dentry - get a dentry for the given kernfs_node
	200	* @kn: kernfs_node for which a dentry is needed
	201	* @sb: the kernfs super_block
24b3e3dd RD	202	*
24b3e3dd RD	203	* Return: the dentry pointer
fb3c8315 AK	204	*/
	205	struct dentry kernfs_node_dentry(struct kernfs_node kn,
	206	struct super_block *sb)
	207	{
	208	struct dentry *dentry;
	209	struct kernfs_node *knparent = NULL;
	210
	211	BUG_ON(sb->s_op != &kernfs_sops);
	212
	213	dentry = dget(sb->s_root);
	214
	215	/* Check if this is the root kernfs_node */
	216	if (!kn->parent)
	217	return dentry;
	218
	219	knparent = find_next_ancestor(kn, NULL);
399504e2 AV	220	if (WARN_ON(!knparent)) {
399504e2 AV	221	dput(dentry);
fb3c8315	222	return ERR_PTR(-EINVAL);
399504e2	223	}
fb3c8315 AK	224
	225	do {
	226	struct dentry *dtmp;
	227	struct kernfs_node *kntmp;
	228
	229	if (kn == knparent)
	230	return dentry;
	231	kntmp = find_next_ancestor(kn, knparent);
399504e2 AV	232	if (WARN_ON(!kntmp)) {
399504e2 AV	233	dput(dentry);
fb3c8315	234	return ERR_PTR(-EINVAL);
399504e2	235	}
6c2d4798	236	dtmp = lookup_positive_unlocked(kntmp->name, dentry,
779b8391	237	strlen(kntmp->name));
fb3c8315 AK	238	dput(dentry);
	239	if (IS_ERR(dtmp))
	240	return dtmp;
	241	knparent = kntmp;
	242	dentry = dtmp;
	243	} while (true);
	244	}
	245
23bf1b6b	246	static int kernfs_fill_super(struct super_block sb, struct kernfs_fs_context kfc)
fa736a95	247	{
c525aadd	248	struct kernfs_super_info *info = kernfs_info(sb);
393c3714	249	struct kernfs_root *kf_root = kfc->root;
fa736a95 TH	250	struct inode *inode;
	251	struct dentry *root;
	252
7d568a83	253	info->sb = sb;
a2982cc9 EB	254	/* Userspace would break if executables or devices appear on sysfs */
a2982cc9 EB	255	sb->s_iflags \|= SB_I_NOEXEC \| SB_I_NODEV;
09cbfeaf KS	256	sb->s_blocksize = PAGE_SIZE;
09cbfeaf KS	257	sb->s_blocksize_bits = PAGE_SHIFT;
23bf1b6b	258	sb->s_magic = kfc->magic;
a797bfc3	259	sb->s_op = &kernfs_sops;
e72a1a8b	260	sb->s_xattr = kernfs_xattr_handlers;
aa818825 SL	261	if (info->root->flags & KERNFS_ROOT_SUPPORT_EXPORTOP)
aa818825 SL	262	sb->s_export_op = &kernfs_export_ops;
fa736a95 TH	263	sb->s_time_gran = 1;
fa736a95 TH	264
4b85afbd	265	/* sysfs dentries and inodes don't require IO to create */
1720f5dd	266	sb->s_shrink->seeks = 0;
4b85afbd	267
fa736a95	268	/* get root inode, initialize and unlock it */
393c3714	269	down_read(&kf_root->kernfs_rwsem);
c637b8ac	270	inode = kernfs_get_inode(sb, info->root->kn);
393c3714	271	up_read(&kf_root->kernfs_rwsem);
fa736a95	272	if (!inode) {
c637b8ac	273	pr_debug("kernfs: could not get root inode\n");
fa736a95 TH	274	return -ENOMEM;
	275	}
	276
	277	/* instantiate and link root dentry */
	278	root = d_make_root(inode);
	279	if (!root) {
	280	pr_debug("%s: could not get root dentry!\n", __func__);
	281	return -ENOMEM;
	282	}
fa736a95	283	sb->s_root = root;
a797bfc3	284	sb->s_d_op = &kernfs_dops;
fa736a95 TH	285	return 0;
	286	}
	287
23bf1b6b	288	static int kernfs_test_super(struct super_block sb, struct fs_context fc)
fa736a95	289	{
c525aadd	290	struct kernfs_super_info *sb_info = kernfs_info(sb);
23bf1b6b	291	struct kernfs_super_info *info = fc->s_fs_info;
fa736a95 TH	292
	293	return sb_info->root == info->root && sb_info->ns == info->ns;
	294	}
	295
23bf1b6b	296	static int kernfs_set_super(struct super_block sb, struct fs_context fc)
fa736a95	297	{
23bf1b6b DH	298	struct kernfs_fs_context *kfc = fc->fs_private;
	299
	300	kfc->ns_tag = NULL;
	301	return set_anon_super_fc(sb, fc);
fa736a95 TH	302	}
	303
	304	/**
	305	* kernfs_super_ns - determine the namespace tag of a kernfs super_block
	306	* @sb: super_block of interest
	307	*
24b3e3dd	308	* Return: the namespace tag associated with kernfs super_block @sb.
fa736a95 TH	309	*/
	310	const void kernfs_super_ns(struct super_block sb)
	311	{
c525aadd	312	struct kernfs_super_info *info = kernfs_info(sb);
fa736a95 TH	313
	314	return info->ns;
	315	}
	316
	317	/**
23bf1b6b DH	318	* kernfs_get_tree - kernfs filesystem access/retrieval helper
23bf1b6b DH	319	* @fc: The filesystem context.
fa736a95	320	*
23bf1b6b DH	321	* This is to be called from each kernfs user's fs_context->ops->get_tree()
	322	* implementation, which should set the specified ->@fs_type and ->@flags, and
	323	* specify the hierarchy and namespace tag to mount via ->@root and ->@ns,
	324	* respectively.
24b3e3dd RD	325	*
24b3e3dd RD	326	* Return: %0 on success, -errno on failure.
fa736a95	327	*/
23bf1b6b	328	int kernfs_get_tree(struct fs_context *fc)
fa736a95	329	{
23bf1b6b	330	struct kernfs_fs_context *kfc = fc->fs_private;
fa736a95	331	struct super_block *sb;
c525aadd	332	struct kernfs_super_info *info;
fa736a95 TH	333	int error;
	334
	335	info = kzalloc(sizeof(*info), GFP_KERNEL);
	336	if (!info)
23bf1b6b	337	return -ENOMEM;
fa736a95	338
23bf1b6b DH	339	info->root = kfc->root;
23bf1b6b DH	340	info->ns = kfc->ns_tag;
82382ace	341	INIT_LIST_HEAD(&info->node);
fa736a95	342
23bf1b6b DH	343	fc->s_fs_info = info;
23bf1b6b DH	344	sb = sget_fc(fc, kernfs_test_super, kernfs_set_super);
fa736a95	345	if (IS_ERR(sb))
23bf1b6b	346	return PTR_ERR(sb);
fed95bab	347
fa736a95	348	if (!sb->s_root) {
7d568a83	349	struct kernfs_super_info *info = kernfs_info(sb);
393c3714	350	struct kernfs_root *root = kfc->root;
7d568a83	351
23bf1b6b DH	352	kfc->new_sb_created = true;
	353
	354	error = kernfs_fill_super(sb, kfc);
fa736a95 TH	355	if (error) {
fa736a95 TH	356	deactivate_locked_super(sb);
23bf1b6b	357	return error;
fa736a95	358	}
1751e8a6	359	sb->s_flags \|= SB_ACTIVE;
7d568a83	360
0ce7c12e IB	361	uuid_gen(&sb->s_uuid);
0ce7c12e IB	362
c9f2dfb7	363	down_write(&root->kernfs_supers_rwsem);
23bf1b6b	364	list_add(&info->node, &info->root->supers);
c9f2dfb7	365	up_write(&root->kernfs_supers_rwsem);
fa736a95 TH	366	}
fa736a95 TH	367
23bf1b6b DH	368	fc->root = dget(sb->s_root);
	369	return 0;
	370	}
	371
	372	void kernfs_free_fs_context(struct fs_context *fc)
	373	{
	374	/* Note that we don't deal with kfc->ns_tag here. */
	375	kfree(fc->s_fs_info);
	376	fc->s_fs_info = NULL;
fa736a95 TH	377	}
	378
	379	/**
	380	* kernfs_kill_sb - kill_sb for kernfs
	381	* @sb: super_block being killed
	382	*
	383	* This can be used directly for file_system_type->kill_sb(). If a kernfs
	384	* user needs extra cleanup, it can implement its own kill_sb() and call
	385	* this function at the end.
	386	*/
	387	void kernfs_kill_sb(struct super_block *sb)
	388	{
c525aadd	389	struct kernfs_super_info *info = kernfs_info(sb);
393c3714	390	struct kernfs_root *root = info->root;
fa736a95	391
c9f2dfb7	392	down_write(&root->kernfs_supers_rwsem);
7d568a83	393	list_del(&info->node);
c9f2dfb7	394	up_write(&root->kernfs_supers_rwsem);
7d568a83	395
fa736a95 TH	396	/*
fa736a95 TH	397	* Remove the superblock from fs_supers/s_instances
c525aadd	398	* so we can't find it, before freeing kernfs_super_info.
fa736a95 TH	399	*/
	400	kill_anon_super(sb);
	401	kfree(info);
fa736a95 TH	402	}
fa736a95 TH	403
1d25b84e IK	404	static void __init kernfs_mutex_init(void)
	405	{
	406	int count;
	407
	408	for (count = 0; count < NR_KERNFS_LOCKS; count++)
	409	mutex_init(&kernfs_locks->open_file_mutex[count]);
	410	}
	411
	412	static void __init kernfs_lock_init(void)
	413	{
	414	kernfs_locks = kmalloc(sizeof(struct kernfs_global_locks), GFP_KERNEL);
	415	WARN_ON(!kernfs_locks);
	416
	417	kernfs_mutex_init();
	418	}
	419
fa736a95 TH	420	void __init kernfs_init(void)
fa736a95 TH	421	{
a797bfc3	422	kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
324a56e1	423	sizeof(struct kernfs_node),
b680b081	424	0, SLAB_PANIC, NULL);
26e28d68 AM	425
	426	/* Creates slab cache for kernfs inode attributes */
	427	kernfs_iattrs_cache = kmem_cache_create("kernfs_iattrs_cache",
	428	sizeof(struct kernfs_iattrs),
	429	0, SLAB_PANIC, NULL);
1d25b84e IK	430
1d25b84e IK	431	kernfs_lock_init();
fa736a95	432	}