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

/*
 * 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>
 *
 * This file is released under the GPLv2.
 */

#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;

static int kernfs_sop_remount_fs(struct super_block *sb, int *flags, char *data)
{
	struct kernfs_root *root = kernfs_info(sb)->root;
	struct kernfs_syscall_ops *scops = root->syscall_ops;

	if (scops && scops->remount_fs)
		return scops->remount_fs(root, flags, data);
	return 0;
}

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,

	.remount_fs	= kernfs_sop_remount_fs,
	.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))
		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))
			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, unsigned long magic)
{
	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 = 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, void *data)
{
	struct kernfs_super_info *sb_info = kernfs_info(sb);
	struct kernfs_super_info *info = data;

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

static int kernfs_set_super(struct super_block *sb, void *data)
{
	int error;
	error = set_anon_super(sb, data);
	if (!error)
		sb->s_fs_info = data;
	return error;
}

/**
 * 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_mount_ns - kernfs mount helper
 * @fs_type: file_system_type of the fs being mounted
 * @flags: mount flags specified for the mount
 * @root: kernfs_root of the hierarchy being mounted
 * @magic: file system specific magic number
 * @new_sb_created: tell the caller if we allocated a new superblock
 * @ns: optional namespace tag of the mount
 *
 * This is to be called from each kernfs user's file_system_type->mount()
 * implementation, which should pass through the specified @fs_type and
 * @flags, and specify the hierarchy and namespace tag to mount via @root
 * and @ns, respectively.
 *
 * The return value can be passed to the vfs layer verbatim.
 */
struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
				struct kernfs_root *root, unsigned long magic,
				bool *new_sb_created, const void *ns)
{
	struct super_block *sb;
	struct kernfs_super_info *info;
	int error;

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

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

	sb = sget_userns(fs_type, kernfs_test_super, kernfs_set_super, flags,
			 &init_user_ns, info);
	if (IS_ERR(sb) || sb->s_fs_info != info)
		kfree(info);
	if (IS_ERR(sb))
		return ERR_CAST(sb);

	if (new_sb_created)
		*new_sb_created = !sb->s_root;

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

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

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

	return dget(sb->s_root);
}

/**
 * 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);
}

/**
 * kernfs_pin_sb: try to pin the superblock associated with a kernfs_root
 * @kernfs_root: the kernfs_root in question
 * @ns: the namespace tag
 *
 * Pin the superblock so the superblock won't be destroyed in subsequent
 * operations.  This can be used to block ->kill_sb() which may be useful
 * for kernfs users which dynamically manage superblocks.
 *
 * Returns NULL if there's no superblock associated to this kernfs_root, or
 * -EINVAL if the superblock is being freed.
 */
struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns)
{
	struct kernfs_super_info *info;
	struct super_block *sb = NULL;

	mutex_lock(&kernfs_mutex);
	list_for_each_entry(info, &root->supers, node) {
		if (info->ns == ns) {
			sb = info->sb;
			if (!atomic_inc_not_zero(&info->sb->s_active))
				sb = ERR_PTR(-EINVAL);
			break;
		}
	}
	mutex_unlock(&kernfs_mutex);
	return sb;
}

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);
}
Commit	Line	Data
b8441ed2 TH	1	/*
	2	* fs/kernfs/mount.c - kernfs mount implementation
	3	*
	4	* Copyright (c) 2001-3 Patrick Mochel
	5	* Copyright (c) 2007 SUSE Linux Products GmbH
	6	* Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
	7	*
	8	* This file is released under the GPLv2.
	9	*/
fa736a95 TH	10
	11	#include <linux/fs.h>
	12	#include <linux/mount.h>
	13	#include <linux/init.h>
	14	#include <linux/magic.h>
	15	#include <linux/slab.h>
	16	#include <linux/pagemap.h>
fb3c8315	17	#include <linux/namei.h>
4f41fc59	18	#include <linux/seq_file.h>
aa818825	19	#include <linux/exportfs.h>
fa736a95 TH	20
	21	#include "kernfs-internal.h"
	22
a797bfc3	23	struct kmem_cache *kernfs_node_cache;
fa736a95	24
6a7fed4e TH	25	static int kernfs_sop_remount_fs(struct super_block sb, int flags, char *data)
	26	{
	27	struct kernfs_root *root = kernfs_info(sb)->root;
	28	struct kernfs_syscall_ops *scops = root->syscall_ops;
	29
	30	if (scops && scops->remount_fs)
	31	return scops->remount_fs(root, flags, data);
	32	return 0;
	33	}
	34
	35	static int kernfs_sop_show_options(struct seq_file sf, struct dentry dentry)
	36	{
319ba91d	37	struct kernfs_root *root = kernfs_root(kernfs_dentry_node(dentry));
6a7fed4e TH	38	struct kernfs_syscall_ops *scops = root->syscall_ops;
	39
	40	if (scops && scops->show_options)
	41	return scops->show_options(sf, root);
	42	return 0;
	43	}
	44
4f41fc59 SH	45	static int kernfs_sop_show_path(struct seq_file sf, struct dentry dentry)
4f41fc59 SH	46	{
319ba91d	47	struct kernfs_node *node = kernfs_dentry_node(dentry);
4f41fc59 SH	48	struct kernfs_root *root = kernfs_root(node);
	49	struct kernfs_syscall_ops *scops = root->syscall_ops;
	50
	51	if (scops && scops->show_path)
	52	return scops->show_path(sf, node, root);
	53
3cc9b23c SH	54	seq_dentry(sf, dentry, " \t\n\\");
3cc9b23c SH	55	return 0;
4f41fc59 SH	56	}
4f41fc59 SH	57
f41c5934	58	const struct super_operations kernfs_sops = {
fa736a95 TH	59	.statfs = simple_statfs,
fa736a95 TH	60	.drop_inode = generic_delete_inode,
c637b8ac	61	.evict_inode = kernfs_evict_inode,
6a7fed4e TH	62
	63	.remount_fs = kernfs_sop_remount_fs,
	64	.show_options = kernfs_sop_show_options,
4f41fc59	65	.show_path = kernfs_sop_show_path,
fa736a95 TH	66	};
fa736a95 TH	67
69fd5c39 SL	68	/*
	69	* Similar to kernfs_fh_get_inode, this one gets kernfs node from inode
	70	* number and generation
	71	*/
	72	struct kernfs_node kernfs_get_node_by_id(struct kernfs_root root,
	73	const union kernfs_node_id *id)
	74	{
	75	struct kernfs_node *kn;
	76
	77	kn = kernfs_find_and_get_node_by_ino(root, id->ino);
	78	if (!kn)
	79	return NULL;
	80	if (kn->id.generation != id->generation) {
	81	kernfs_put(kn);
	82	return NULL;
	83	}
	84	return kn;
	85	}
	86
aa818825 SL	87	static struct inode kernfs_fh_get_inode(struct super_block sb,
	88	u64 ino, u32 generation)
	89	{
	90	struct kernfs_super_info *info = kernfs_info(sb);
	91	struct inode *inode;
	92	struct kernfs_node *kn;
	93
	94	if (ino == 0)
	95	return ERR_PTR(-ESTALE);
	96
	97	kn = kernfs_find_and_get_node_by_ino(info->root, ino);
	98	if (!kn)
	99	return ERR_PTR(-ESTALE);
	100	inode = kernfs_get_inode(sb, kn);
	101	kernfs_put(kn);
ef13ecbc DC	102	if (!inode)
ef13ecbc DC	103	return ERR_PTR(-ESTALE);
aa818825 SL	104
	105	if (generation && inode->i_generation != generation) {
	106	/* we didn't find the right inode.. */
	107	iput(inode);
	108	return ERR_PTR(-ESTALE);
	109	}
	110	return inode;
	111	}
	112
	113	static struct dentry kernfs_fh_to_dentry(struct super_block sb, struct fid *fid,
	114	int fh_len, int fh_type)
	115	{
	116	return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
	117	kernfs_fh_get_inode);
	118	}
	119
	120	static struct dentry kernfs_fh_to_parent(struct super_block sb, struct fid *fid,
	121	int fh_len, int fh_type)
	122	{
	123	return generic_fh_to_parent(sb, fid, fh_len, fh_type,
	124	kernfs_fh_get_inode);
	125	}
	126
	127	static struct dentry kernfs_get_parent_dentry(struct dentry child)
	128	{
	129	struct kernfs_node *kn = kernfs_dentry_node(child);
	130
	131	return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent));
	132	}
	133
	134	static const struct export_operations kernfs_export_ops = {
	135	.fh_to_dentry = kernfs_fh_to_dentry,
	136	.fh_to_parent = kernfs_fh_to_parent,
	137	.get_parent = kernfs_get_parent_dentry,
	138	};
	139
0c23b225 TH	140	/**
	141	* kernfs_root_from_sb - determine kernfs_root associated with a super_block
	142	* @sb: the super_block in question
	143	*
	144	* Return the kernfs_root associated with @sb. If @sb is not a kernfs one,
	145	* %NULL is returned.
	146	*/
	147	struct kernfs_root kernfs_root_from_sb(struct super_block sb)
	148	{
	149	if (sb->s_op == &kernfs_sops)
	150	return kernfs_info(sb)->root;
	151	return NULL;
	152	}
	153
fb3c8315 AK	154	/*
	155	* find the next ancestor in the path down to @child, where @parent was the
	156	* ancestor whose descendant we want to find.
	157	*
	158	* Say the path is /a/b/c/d. @child is d, @parent is NULL. We return the root
	159	* node. If @parent is b, then we return the node for c.
	160	* Passing in d as @parent is not ok.
	161	*/
	162	static struct kernfs_node find_next_ancestor(struct kernfs_node child,
	163	struct kernfs_node *parent)
	164	{
	165	if (child == parent) {
	166	pr_crit_once("BUG in find_next_ancestor: called with parent == child");
	167	return NULL;
	168	}
	169
	170	while (child->parent != parent) {
	171	if (!child->parent)
	172	return NULL;
	173	child = child->parent;
	174	}
	175
	176	return child;
	177	}
	178
	179	/**
	180	* kernfs_node_dentry - get a dentry for the given kernfs_node
	181	* @kn: kernfs_node for which a dentry is needed
	182	* @sb: the kernfs super_block
	183	*/
	184	struct dentry kernfs_node_dentry(struct kernfs_node kn,
	185	struct super_block *sb)
	186	{
	187	struct dentry *dentry;
	188	struct kernfs_node *knparent = NULL;
	189
	190	BUG_ON(sb->s_op != &kernfs_sops);
	191
	192	dentry = dget(sb->s_root);
	193
	194	/* Check if this is the root kernfs_node */
	195	if (!kn->parent)
	196	return dentry;
	197
	198	knparent = find_next_ancestor(kn, NULL);
	199	if (WARN_ON(!knparent))
	200	return ERR_PTR(-EINVAL);
	201
	202	do {
	203	struct dentry *dtmp;
	204	struct kernfs_node *kntmp;
	205
	206	if (kn == knparent)
	207	return dentry;
	208	kntmp = find_next_ancestor(kn, knparent);
	209	if (WARN_ON(!kntmp))
	210	return ERR_PTR(-EINVAL);
779b8391 AV	211	dtmp = lookup_one_len_unlocked(kntmp->name, dentry,
779b8391 AV	212	strlen(kntmp->name));
fb3c8315 AK	213	dput(dentry);
	214	if (IS_ERR(dtmp))
	215	return dtmp;
	216	knparent = kntmp;
	217	dentry = dtmp;
	218	} while (true);
	219	}
	220
26fc9cd2	221	static int kernfs_fill_super(struct super_block *sb, unsigned long magic)
fa736a95	222	{
c525aadd	223	struct kernfs_super_info *info = kernfs_info(sb);
fa736a95 TH	224	struct inode *inode;
	225	struct dentry *root;
	226
7d568a83	227	info->sb = sb;
a2982cc9 EB	228	/* Userspace would break if executables or devices appear on sysfs */
a2982cc9 EB	229	sb->s_iflags \|= SB_I_NOEXEC \| SB_I_NODEV;
09cbfeaf KS	230	sb->s_blocksize = PAGE_SIZE;
09cbfeaf KS	231	sb->s_blocksize_bits = PAGE_SHIFT;
26fc9cd2	232	sb->s_magic = magic;
a797bfc3	233	sb->s_op = &kernfs_sops;
e72a1a8b	234	sb->s_xattr = kernfs_xattr_handlers;
aa818825 SL	235	if (info->root->flags & KERNFS_ROOT_SUPPORT_EXPORTOP)
aa818825 SL	236	sb->s_export_op = &kernfs_export_ops;
fa736a95 TH	237	sb->s_time_gran = 1;
fa736a95 TH	238
4b85afbd JW	239	/* sysfs dentries and inodes don't require IO to create */
	240	sb->s_shrink.seeks = 0;
	241
fa736a95	242	/* get root inode, initialize and unlock it */
a797bfc3	243	mutex_lock(&kernfs_mutex);
c637b8ac	244	inode = kernfs_get_inode(sb, info->root->kn);
a797bfc3	245	mutex_unlock(&kernfs_mutex);
fa736a95	246	if (!inode) {
c637b8ac	247	pr_debug("kernfs: could not get root inode\n");
fa736a95 TH	248	return -ENOMEM;
	249	}
	250
	251	/* instantiate and link root dentry */
	252	root = d_make_root(inode);
	253	if (!root) {
	254	pr_debug("%s: could not get root dentry!\n", __func__);
	255	return -ENOMEM;
	256	}
fa736a95	257	sb->s_root = root;
a797bfc3	258	sb->s_d_op = &kernfs_dops;
fa736a95 TH	259	return 0;
	260	}
	261
c637b8ac	262	static int kernfs_test_super(struct super_block sb, void data)
fa736a95	263	{
c525aadd TH	264	struct kernfs_super_info *sb_info = kernfs_info(sb);
c525aadd TH	265	struct kernfs_super_info *info = data;
fa736a95 TH	266
	267	return sb_info->root == info->root && sb_info->ns == info->ns;
	268	}
	269
c637b8ac	270	static int kernfs_set_super(struct super_block sb, void data)
fa736a95 TH	271	{
	272	int error;
	273	error = set_anon_super(sb, data);
	274	if (!error)
	275	sb->s_fs_info = data;
	276	return error;
	277	}
	278
	279	/**
	280	* kernfs_super_ns - determine the namespace tag of a kernfs super_block
	281	* @sb: super_block of interest
	282	*
	283	* Return the namespace tag associated with kernfs super_block @sb.
	284	*/
	285	const void kernfs_super_ns(struct super_block sb)
	286	{
c525aadd	287	struct kernfs_super_info *info = kernfs_info(sb);
fa736a95 TH	288
	289	return info->ns;
	290	}
	291
	292	/**
	293	* kernfs_mount_ns - kernfs mount helper
	294	* @fs_type: file_system_type of the fs being mounted
	295	* @flags: mount flags specified for the mount
	296	* @root: kernfs_root of the hierarchy being mounted
26fc9cd2	297	* @magic: file system specific magic number
fed95bab	298	* @new_sb_created: tell the caller if we allocated a new superblock
fa736a95 TH	299	* @ns: optional namespace tag of the mount
	300	*
	301	* This is to be called from each kernfs user's file_system_type->mount()
	302	* implementation, which should pass through the specified @fs_type and
	303	* @flags, and specify the hierarchy and namespace tag to mount via @root
	304	* and @ns, respectively.
	305	*
	306	* The return value can be passed to the vfs layer verbatim.
	307	*/
	308	struct dentry kernfs_mount_ns(struct file_system_type fs_type, int flags,
26fc9cd2 JZ	309	struct kernfs_root *root, unsigned long magic,
26fc9cd2 JZ	310	bool new_sb_created, const void ns)
fa736a95 TH	311	{
fa736a95 TH	312	struct super_block *sb;
c525aadd	313	struct kernfs_super_info *info;
fa736a95 TH	314	int error;
	315
	316	info = kzalloc(sizeof(*info), GFP_KERNEL);
	317	if (!info)
	318	return ERR_PTR(-ENOMEM);
	319
	320	info->root = root;
	321	info->ns = ns;
82382ace	322	INIT_LIST_HEAD(&info->node);
fa736a95	323
6e4eab57 EB	324	sb = sget_userns(fs_type, kernfs_test_super, kernfs_set_super, flags,
6e4eab57 EB	325	&init_user_ns, info);
fa736a95 TH	326	if (IS_ERR(sb) \|\| sb->s_fs_info != info)
	327	kfree(info);
	328	if (IS_ERR(sb))
	329	return ERR_CAST(sb);
fed95bab LZ	330
	331	if (new_sb_created)
	332	*new_sb_created = !sb->s_root;
	333
fa736a95	334	if (!sb->s_root) {
7d568a83 TH	335	struct kernfs_super_info *info = kernfs_info(sb);
7d568a83 TH	336
26fc9cd2	337	error = kernfs_fill_super(sb, magic);
fa736a95 TH	338	if (error) {
	339	deactivate_locked_super(sb);
	340	return ERR_PTR(error);
	341	}
1751e8a6	342	sb->s_flags \|= SB_ACTIVE;
7d568a83 TH	343
	344	mutex_lock(&kernfs_mutex);
	345	list_add(&info->node, &root->supers);
	346	mutex_unlock(&kernfs_mutex);
fa736a95 TH	347	}
	348
	349	return dget(sb->s_root);
	350	}
	351
	352	/**
	353	* kernfs_kill_sb - kill_sb for kernfs
	354	* @sb: super_block being killed
	355	*
	356	* This can be used directly for file_system_type->kill_sb(). If a kernfs
	357	* user needs extra cleanup, it can implement its own kill_sb() and call
	358	* this function at the end.
	359	*/
	360	void kernfs_kill_sb(struct super_block *sb)
	361	{
c525aadd	362	struct kernfs_super_info *info = kernfs_info(sb);
fa736a95	363
7d568a83 TH	364	mutex_lock(&kernfs_mutex);
	365	list_del(&info->node);
	366	mutex_unlock(&kernfs_mutex);
	367
fa736a95 TH	368	/*
fa736a95 TH	369	* Remove the superblock from fs_supers/s_instances
c525aadd	370	* so we can't find it, before freeing kernfs_super_info.
fa736a95 TH	371	*/
	372	kill_anon_super(sb);
	373	kfree(info);
fa736a95 TH	374	}
fa736a95 TH	375
4e26445f LZ	376	/**
	377	* kernfs_pin_sb: try to pin the superblock associated with a kernfs_root
	378	* @kernfs_root: the kernfs_root in question
	379	* @ns: the namespace tag
	380	*
	381	* Pin the superblock so the superblock won't be destroyed in subsequent
	382	* operations. This can be used to block ->kill_sb() which may be useful
	383	* for kernfs users which dynamically manage superblocks.
	384	*
	385	* Returns NULL if there's no superblock associated to this kernfs_root, or
	386	* -EINVAL if the superblock is being freed.
	387	*/
	388	struct super_block kernfs_pin_sb(struct kernfs_root root, const void *ns)
	389	{
	390	struct kernfs_super_info *info;
	391	struct super_block *sb = NULL;
	392
	393	mutex_lock(&kernfs_mutex);
	394	list_for_each_entry(info, &root->supers, node) {
	395	if (info->ns == ns) {
	396	sb = info->sb;
	397	if (!atomic_inc_not_zero(&info->sb->s_active))
	398	sb = ERR_PTR(-EINVAL);
	399	break;
	400	}
	401	}
	402	mutex_unlock(&kernfs_mutex);
	403	return sb;
	404	}
	405
fa736a95 TH	406	void __init kernfs_init(void)
fa736a95 TH	407	{
ba16b284 SL	408
	409	/*
	410	* the slab is freed in RCU context, so kernfs_find_and_get_node_by_ino
	411	* can access the slab lock free. This could introduce stale nodes,
	412	* please see how kernfs_find_and_get_node_by_ino filters out stale
	413	* nodes.
	414	*/
a797bfc3	415	kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
324a56e1	416	sizeof(struct kernfs_node),
ba16b284 SL	417	0,
	418	SLAB_PANIC \| SLAB_TYPESAFE_BY_RCU,
	419	NULL);
fa736a95	420	}