[linux-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;
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();
}
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;
1d25b84e	23	struct kernfs_global_locks *kernfs_locks;
fa736a95	24
6a7fed4e TH	25	static int kernfs_sop_show_options(struct seq_file sf, struct dentry dentry)
6a7fed4e TH	26	{
319ba91d	27	struct kernfs_root *root = kernfs_root(kernfs_dentry_node(dentry));
6a7fed4e TH	28	struct kernfs_syscall_ops *scops = root->syscall_ops;
	29
	30	if (scops && scops->show_options)
	31	return scops->show_options(sf, root);
	32	return 0;
	33	}
	34
4f41fc59 SH	35	static int kernfs_sop_show_path(struct seq_file sf, struct dentry dentry)
4f41fc59 SH	36	{
319ba91d	37	struct kernfs_node *node = kernfs_dentry_node(dentry);
4f41fc59 SH	38	struct kernfs_root *root = kernfs_root(node);
	39	struct kernfs_syscall_ops *scops = root->syscall_ops;
	40
	41	if (scops && scops->show_path)
	42	return scops->show_path(sf, node, root);
	43
3cc9b23c SH	44	seq_dentry(sf, dentry, " \t\n\\");
3cc9b23c SH	45	return 0;
4f41fc59 SH	46	}
4f41fc59 SH	47
f41c5934	48	const struct super_operations kernfs_sops = {
fa736a95 TH	49	.statfs = simple_statfs,
fa736a95 TH	50	.drop_inode = generic_delete_inode,
c637b8ac	51	.evict_inode = kernfs_evict_inode,
6a7fed4e	52
6a7fed4e	53	.show_options = kernfs_sop_show_options,
4f41fc59	54	.show_path = kernfs_sop_show_path,
fa736a95 TH	55	};
fa736a95 TH	56
33c5ac91 TH	57	static int kernfs_encode_fh(struct inode inode, __u32 fh, int *max_len,
33c5ac91 TH	58	struct inode *parent)
aa818825	59	{
33c5ac91	60	struct kernfs_node *kn = inode->i_private;
aa818825	61
33c5ac91 TH	62	if (*max_len < 2) {
	63	*max_len = 2;
	64	return FILEID_INVALID;
	65	}
aa818825	66
33c5ac91 TH	67	*max_len = 2;
	68	(u64 )fh = kn->id;
	69	return FILEID_KERNFS;
	70	}
	71
	72	static struct dentry __kernfs_fh_to_dentry(struct super_block sb,
	73	struct fid *fid, int fh_len,
	74	int fh_type, bool get_parent)
	75	{
	76	struct kernfs_super_info *info = kernfs_info(sb);
	77	struct kernfs_node *kn;
	78	struct inode *inode;
	79	u64 id;
	80
	81	if (fh_len < 2)
	82	return NULL;
	83
	84	switch (fh_type) {
	85	case FILEID_KERNFS:
	86	id = (u64 )fid;
	87	break;
	88	case FILEID_INO32_GEN:
	89	case FILEID_INO32_GEN_PARENT:
	90	/*
40430452 TH	91	* blk_log_action() exposes "LOW32,HIGH32" pair without
	92	* type and userland can call us with generic fid
	93	* constructed from them. Combine it back to ID. See
	94	* blk_log_action().
33c5ac91 TH	95	*/
	96	id = ((u64)fid->i32.gen << 32) \| fid->i32.ino;
	97	break;
	98	default:
	99	return NULL;
	100	}
	101
	102	kn = kernfs_find_and_get_node_by_id(info->root, id);
aa818825 SL	103	if (!kn)
aa818825 SL	104	return ERR_PTR(-ESTALE);
33c5ac91 TH	105
	106	if (get_parent) {
	107	struct kernfs_node *parent;
	108
	109	parent = kernfs_get_parent(kn);
	110	kernfs_put(kn);
	111	kn = parent;
	112	if (!kn)
	113	return ERR_PTR(-ESTALE);
	114	}
	115
aa818825 SL	116	inode = kernfs_get_inode(sb, kn);
aa818825 SL	117	kernfs_put(kn);
ef13ecbc DC	118	if (!inode)
ef13ecbc DC	119	return ERR_PTR(-ESTALE);
aa818825	120
33c5ac91	121	return d_obtain_alias(inode);
aa818825 SL	122	}
aa818825 SL	123
33c5ac91 TH	124	static struct dentry kernfs_fh_to_dentry(struct super_block sb,
	125	struct fid *fid, int fh_len,
	126	int fh_type)
aa818825	127	{
33c5ac91	128	return __kernfs_fh_to_dentry(sb, fid, fh_len, fh_type, false);
aa818825 SL	129	}
aa818825 SL	130
33c5ac91 TH	131	static struct dentry kernfs_fh_to_parent(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, true);
aa818825 SL	136	}
	137
	138	static struct dentry kernfs_get_parent_dentry(struct dentry child)
	139	{
	140	struct kernfs_node *kn = kernfs_dentry_node(child);
	141
	142	return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent));
	143	}
	144
	145	static const struct export_operations kernfs_export_ops = {
33c5ac91	146	.encode_fh = kernfs_encode_fh,
aa818825 SL	147	.fh_to_dentry = kernfs_fh_to_dentry,
	148	.fh_to_parent = kernfs_fh_to_parent,
	149	.get_parent = kernfs_get_parent_dentry,
	150	};
	151
0c23b225 TH	152	/**
	153	* kernfs_root_from_sb - determine kernfs_root associated with a super_block
	154	* @sb: the super_block in question
	155	*
24b3e3dd	156	* Return: the kernfs_root associated with @sb. If @sb is not a kernfs one,
0c23b225 TH	157	* %NULL is returned.
	158	*/
	159	struct kernfs_root kernfs_root_from_sb(struct super_block sb)
	160	{
	161	if (sb->s_op == &kernfs_sops)
	162	return kernfs_info(sb)->root;
	163	return NULL;
	164	}
	165
fb3c8315 AK	166	/*
	167	* find the next ancestor in the path down to @child, where @parent was the
	168	* ancestor whose descendant we want to find.
	169	*
24b3e3dd	170	* Say the path is /a/b/c/d. @child is d, @parent is %NULL. We return the root
fb3c8315 AK	171	* node. If @parent is b, then we return the node for c.
	172	* Passing in d as @parent is not ok.
	173	*/
	174	static struct kernfs_node find_next_ancestor(struct kernfs_node child,
	175	struct kernfs_node *parent)
	176	{
	177	if (child == parent) {
	178	pr_crit_once("BUG in find_next_ancestor: called with parent == child");
	179	return NULL;
	180	}
	181
	182	while (child->parent != parent) {
	183	if (!child->parent)
	184	return NULL;
	185	child = child->parent;
	186	}
	187
	188	return child;
	189	}
	190
	191	/**
	192	* kernfs_node_dentry - get a dentry for the given kernfs_node
	193	* @kn: kernfs_node for which a dentry is needed
	194	* @sb: the kernfs super_block
24b3e3dd RD	195	*
24b3e3dd RD	196	* Return: the dentry pointer
fb3c8315 AK	197	*/
	198	struct dentry kernfs_node_dentry(struct kernfs_node kn,
	199	struct super_block *sb)
	200	{
	201	struct dentry *dentry;
	202	struct kernfs_node *knparent = NULL;
	203
	204	BUG_ON(sb->s_op != &kernfs_sops);
	205
	206	dentry = dget(sb->s_root);
	207
	208	/* Check if this is the root kernfs_node */
	209	if (!kn->parent)
	210	return dentry;
	211
	212	knparent = find_next_ancestor(kn, NULL);
399504e2 AV	213	if (WARN_ON(!knparent)) {
399504e2 AV	214	dput(dentry);
fb3c8315	215	return ERR_PTR(-EINVAL);
399504e2	216	}
fb3c8315 AK	217
	218	do {
	219	struct dentry *dtmp;
	220	struct kernfs_node *kntmp;
	221
	222	if (kn == knparent)
	223	return dentry;
	224	kntmp = find_next_ancestor(kn, knparent);
399504e2 AV	225	if (WARN_ON(!kntmp)) {
399504e2 AV	226	dput(dentry);
fb3c8315	227	return ERR_PTR(-EINVAL);
399504e2	228	}
6c2d4798	229	dtmp = lookup_positive_unlocked(kntmp->name, dentry,
779b8391	230	strlen(kntmp->name));
fb3c8315 AK	231	dput(dentry);
	232	if (IS_ERR(dtmp))
	233	return dtmp;
	234	knparent = kntmp;
	235	dentry = dtmp;
	236	} while (true);
	237	}
	238
23bf1b6b	239	static int kernfs_fill_super(struct super_block sb, struct kernfs_fs_context kfc)
fa736a95	240	{
c525aadd	241	struct kernfs_super_info *info = kernfs_info(sb);
393c3714	242	struct kernfs_root *kf_root = kfc->root;
fa736a95 TH	243	struct inode *inode;
	244	struct dentry *root;
	245
7d568a83	246	info->sb = sb;
a2982cc9 EB	247	/* Userspace would break if executables or devices appear on sysfs */
a2982cc9 EB	248	sb->s_iflags \|= SB_I_NOEXEC \| SB_I_NODEV;
09cbfeaf KS	249	sb->s_blocksize = PAGE_SIZE;
09cbfeaf KS	250	sb->s_blocksize_bits = PAGE_SHIFT;
23bf1b6b	251	sb->s_magic = kfc->magic;
a797bfc3	252	sb->s_op = &kernfs_sops;
e72a1a8b	253	sb->s_xattr = kernfs_xattr_handlers;
aa818825 SL	254	if (info->root->flags & KERNFS_ROOT_SUPPORT_EXPORTOP)
aa818825 SL	255	sb->s_export_op = &kernfs_export_ops;
fa736a95 TH	256	sb->s_time_gran = 1;
fa736a95 TH	257
4b85afbd JW	258	/* sysfs dentries and inodes don't require IO to create */
	259	sb->s_shrink.seeks = 0;
	260
fa736a95	261	/* get root inode, initialize and unlock it */
393c3714	262	down_read(&kf_root->kernfs_rwsem);
c637b8ac	263	inode = kernfs_get_inode(sb, info->root->kn);
393c3714	264	up_read(&kf_root->kernfs_rwsem);
fa736a95	265	if (!inode) {
c637b8ac	266	pr_debug("kernfs: could not get root inode\n");
fa736a95 TH	267	return -ENOMEM;
	268	}
	269
	270	/* instantiate and link root dentry */
	271	root = d_make_root(inode);
	272	if (!root) {
	273	pr_debug("%s: could not get root dentry!\n", __func__);
	274	return -ENOMEM;
	275	}
fa736a95	276	sb->s_root = root;
a797bfc3	277	sb->s_d_op = &kernfs_dops;
fa736a95 TH	278	return 0;
	279	}
	280
23bf1b6b	281	static int kernfs_test_super(struct super_block sb, struct fs_context fc)
fa736a95	282	{
c525aadd	283	struct kernfs_super_info *sb_info = kernfs_info(sb);
23bf1b6b	284	struct kernfs_super_info *info = fc->s_fs_info;
fa736a95 TH	285
	286	return sb_info->root == info->root && sb_info->ns == info->ns;
	287	}
	288
23bf1b6b	289	static int kernfs_set_super(struct super_block sb, struct fs_context fc)
fa736a95	290	{
23bf1b6b DH	291	struct kernfs_fs_context *kfc = fc->fs_private;
	292
	293	kfc->ns_tag = NULL;
	294	return set_anon_super_fc(sb, fc);
fa736a95 TH	295	}
	296
	297	/**
	298	* kernfs_super_ns - determine the namespace tag of a kernfs super_block
	299	* @sb: super_block of interest
	300	*
24b3e3dd	301	* Return: the namespace tag associated with kernfs super_block @sb.
fa736a95 TH	302	*/
	303	const void kernfs_super_ns(struct super_block sb)
	304	{
c525aadd	305	struct kernfs_super_info *info = kernfs_info(sb);
fa736a95 TH	306
	307	return info->ns;
	308	}
	309
	310	/**
23bf1b6b DH	311	* kernfs_get_tree - kernfs filesystem access/retrieval helper
23bf1b6b DH	312	* @fc: The filesystem context.
fa736a95	313	*
23bf1b6b DH	314	* This is to be called from each kernfs user's fs_context->ops->get_tree()
	315	* implementation, which should set the specified ->@fs_type and ->@flags, and
	316	* specify the hierarchy and namespace tag to mount via ->@root and ->@ns,
	317	* respectively.
24b3e3dd RD	318	*
24b3e3dd RD	319	* Return: %0 on success, -errno on failure.
fa736a95	320	*/
23bf1b6b	321	int kernfs_get_tree(struct fs_context *fc)
fa736a95	322	{
23bf1b6b	323	struct kernfs_fs_context *kfc = fc->fs_private;
fa736a95	324	struct super_block *sb;
c525aadd	325	struct kernfs_super_info *info;
fa736a95 TH	326	int error;
	327
	328	info = kzalloc(sizeof(*info), GFP_KERNEL);
	329	if (!info)
23bf1b6b	330	return -ENOMEM;
fa736a95	331
23bf1b6b DH	332	info->root = kfc->root;
23bf1b6b DH	333	info->ns = kfc->ns_tag;
82382ace	334	INIT_LIST_HEAD(&info->node);
fa736a95	335
23bf1b6b DH	336	fc->s_fs_info = info;
23bf1b6b DH	337	sb = sget_fc(fc, kernfs_test_super, kernfs_set_super);
fa736a95	338	if (IS_ERR(sb))
23bf1b6b	339	return PTR_ERR(sb);
fed95bab	340
fa736a95	341	if (!sb->s_root) {
7d568a83	342	struct kernfs_super_info *info = kernfs_info(sb);
393c3714	343	struct kernfs_root *root = kfc->root;
7d568a83	344
23bf1b6b DH	345	kfc->new_sb_created = true;
	346
	347	error = kernfs_fill_super(sb, kfc);
fa736a95 TH	348	if (error) {
fa736a95 TH	349	deactivate_locked_super(sb);
23bf1b6b	350	return error;
fa736a95	351	}
1751e8a6	352	sb->s_flags \|= SB_ACTIVE;
7d568a83	353
393c3714	354	down_write(&root->kernfs_rwsem);
23bf1b6b	355	list_add(&info->node, &info->root->supers);
393c3714	356	up_write(&root->kernfs_rwsem);
fa736a95 TH	357	}
fa736a95 TH	358
23bf1b6b DH	359	fc->root = dget(sb->s_root);
	360	return 0;
	361	}
	362
	363	void kernfs_free_fs_context(struct fs_context *fc)
	364	{
	365	/* Note that we don't deal with kfc->ns_tag here. */
	366	kfree(fc->s_fs_info);
	367	fc->s_fs_info = NULL;
fa736a95 TH	368	}
	369
	370	/**
	371	* kernfs_kill_sb - kill_sb for kernfs
	372	* @sb: super_block being killed
	373	*
	374	* This can be used directly for file_system_type->kill_sb(). If a kernfs
	375	* user needs extra cleanup, it can implement its own kill_sb() and call
	376	* this function at the end.
	377	*/
	378	void kernfs_kill_sb(struct super_block *sb)
	379	{
c525aadd	380	struct kernfs_super_info *info = kernfs_info(sb);
393c3714	381	struct kernfs_root *root = info->root;
fa736a95	382
393c3714	383	down_write(&root->kernfs_rwsem);
7d568a83	384	list_del(&info->node);
393c3714	385	up_write(&root->kernfs_rwsem);
7d568a83	386
fa736a95 TH	387	/*
fa736a95 TH	388	* Remove the superblock from fs_supers/s_instances
c525aadd	389	* so we can't find it, before freeing kernfs_super_info.
fa736a95 TH	390	*/
	391	kill_anon_super(sb);
	392	kfree(info);
fa736a95 TH	393	}
fa736a95 TH	394
1d25b84e IK	395	static void __init kernfs_mutex_init(void)
	396	{
	397	int count;
	398
	399	for (count = 0; count < NR_KERNFS_LOCKS; count++)
	400	mutex_init(&kernfs_locks->open_file_mutex[count]);
	401	}
	402
	403	static void __init kernfs_lock_init(void)
	404	{
	405	kernfs_locks = kmalloc(sizeof(struct kernfs_global_locks), GFP_KERNEL);
	406	WARN_ON(!kernfs_locks);
	407
	408	kernfs_mutex_init();
	409	}
	410
fa736a95 TH	411	void __init kernfs_init(void)
fa736a95 TH	412	{
a797bfc3	413	kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
324a56e1	414	sizeof(struct kernfs_node),
b680b081	415	0, SLAB_PANIC, NULL);
26e28d68 AM	416
	417	/* Creates slab cache for kernfs inode attributes */
	418	kernfs_iattrs_cache = kmem_cache_create("kernfs_iattrs_cache",
	419	sizeof(struct kernfs_iattrs),
	420	0, SLAB_PANIC, NULL);
1d25b84e IK	421
1d25b84e IK	422	kernfs_lock_init();
fa736a95	423	}