[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 "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(dentry->d_fsdata);
	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 = dentry->d_fsdata;
	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,
};

/**
 * 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);
		mutex_lock(&d_inode(dentry)->i_mutex);
		dtmp = lookup_one_len(kntmp->name, dentry, strlen(kntmp->name));
		mutex_unlock(&d_inode(dentry)->i_mutex);
		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;
	sb->s_blocksize = PAGE_SIZE;
	sb->s_blocksize_bits = PAGE_SHIFT;
	sb->s_magic = magic;
	sb->s_op = &kernfs_sops;
	sb->s_time_gran = 1;

	/* 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;
	}
	kernfs_get(info->root->kn);
	root->d_fsdata = info->root->kn;
	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;

	sb = sget(fs_type, kernfs_test_super, kernfs_set_super, flags, 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 |= MS_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);
	struct kernfs_node *root_kn = sb->s_root->d_fsdata;

	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_put(root_kn);
}

/**
 * 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)
{
	kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
					      sizeof(struct kernfs_node),
					      0, SLAB_PANIC, 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>
fa736a95 TH	19
	20	#include "kernfs-internal.h"
	21
a797bfc3	22	struct kmem_cache *kernfs_node_cache;
fa736a95	23
6a7fed4e TH	24	static int kernfs_sop_remount_fs(struct super_block sb, int flags, char *data)
	25	{
	26	struct kernfs_root *root = kernfs_info(sb)->root;
	27	struct kernfs_syscall_ops *scops = root->syscall_ops;
	28
	29	if (scops && scops->remount_fs)
	30	return scops->remount_fs(root, flags, data);
	31	return 0;
	32	}
	33
	34	static int kernfs_sop_show_options(struct seq_file sf, struct dentry dentry)
	35	{
	36	struct kernfs_root *root = kernfs_root(dentry->d_fsdata);
	37	struct kernfs_syscall_ops *scops = root->syscall_ops;
	38
	39	if (scops && scops->show_options)
	40	return scops->show_options(sf, root);
	41	return 0;
	42	}
	43
4f41fc59 SH	44	static int kernfs_sop_show_path(struct seq_file sf, struct dentry dentry)
	45	{
	46	struct kernfs_node *node = dentry->d_fsdata;
	47	struct kernfs_root *root = kernfs_root(node);
	48	struct kernfs_syscall_ops *scops = root->syscall_ops;
	49
	50	if (scops && scops->show_path)
	51	return scops->show_path(sf, node, root);
	52
3cc9b23c SH	53	seq_dentry(sf, dentry, " \t\n\\");
3cc9b23c SH	54	return 0;
4f41fc59 SH	55	}
4f41fc59 SH	56
f41c5934	57	const struct super_operations kernfs_sops = {
fa736a95 TH	58	.statfs = simple_statfs,
fa736a95 TH	59	.drop_inode = generic_delete_inode,
c637b8ac	60	.evict_inode = kernfs_evict_inode,
6a7fed4e TH	61
	62	.remount_fs = kernfs_sop_remount_fs,
	63	.show_options = kernfs_sop_show_options,
4f41fc59	64	.show_path = kernfs_sop_show_path,
fa736a95 TH	65	};
fa736a95 TH	66
0c23b225 TH	67	/**
	68	* kernfs_root_from_sb - determine kernfs_root associated with a super_block
	69	* @sb: the super_block in question
	70	*
	71	* Return the kernfs_root associated with @sb. If @sb is not a kernfs one,
	72	* %NULL is returned.
	73	*/
	74	struct kernfs_root kernfs_root_from_sb(struct super_block sb)
	75	{
	76	if (sb->s_op == &kernfs_sops)
	77	return kernfs_info(sb)->root;
	78	return NULL;
	79	}
	80
fb3c8315 AK	81	/*
	82	* find the next ancestor in the path down to @child, where @parent was the
	83	* ancestor whose descendant we want to find.
	84	*
	85	* Say the path is /a/b/c/d. @child is d, @parent is NULL. We return the root
	86	* node. If @parent is b, then we return the node for c.
	87	* Passing in d as @parent is not ok.
	88	*/
	89	static struct kernfs_node find_next_ancestor(struct kernfs_node child,
	90	struct kernfs_node *parent)
	91	{
	92	if (child == parent) {
	93	pr_crit_once("BUG in find_next_ancestor: called with parent == child");
	94	return NULL;
	95	}
	96
	97	while (child->parent != parent) {
	98	if (!child->parent)
	99	return NULL;
	100	child = child->parent;
	101	}
	102
	103	return child;
	104	}
	105
	106	/**
	107	* kernfs_node_dentry - get a dentry for the given kernfs_node
	108	* @kn: kernfs_node for which a dentry is needed
	109	* @sb: the kernfs super_block
	110	*/
	111	struct dentry kernfs_node_dentry(struct kernfs_node kn,
	112	struct super_block *sb)
	113	{
	114	struct dentry *dentry;
	115	struct kernfs_node *knparent = NULL;
	116
	117	BUG_ON(sb->s_op != &kernfs_sops);
	118
	119	dentry = dget(sb->s_root);
	120
	121	/* Check if this is the root kernfs_node */
	122	if (!kn->parent)
	123	return dentry;
	124
	125	knparent = find_next_ancestor(kn, NULL);
	126	if (WARN_ON(!knparent))
	127	return ERR_PTR(-EINVAL);
	128
	129	do {
	130	struct dentry *dtmp;
	131	struct kernfs_node *kntmp;
	132
	133	if (kn == knparent)
	134	return dentry;
	135	kntmp = find_next_ancestor(kn, knparent);
	136	if (WARN_ON(!kntmp))
	137	return ERR_PTR(-EINVAL);
	138	mutex_lock(&d_inode(dentry)->i_mutex);
	139	dtmp = lookup_one_len(kntmp->name, dentry, strlen(kntmp->name));
	140	mutex_unlock(&d_inode(dentry)->i_mutex);
	141	dput(dentry);
	142	if (IS_ERR(dtmp))
	143	return dtmp;
	144	knparent = kntmp;
145	dentry = dtmp;
146	} while (true);
147	}
148
26fc9cd2	149	static int kernfs_fill_super(struct super_block *sb, unsigned long magic)
fa736a95	150	{
c525aadd	151	struct kernfs_super_info *info = kernfs_info(sb);
fa736a95 TH	152	struct inode *inode;
	153	struct dentry *root;
	154
7d568a83	155	info->sb = sb;
09cbfeaf KS	156	sb->s_blocksize = PAGE_SIZE;
09cbfeaf KS	157	sb->s_blocksize_bits = PAGE_SHIFT;
26fc9cd2	158	sb->s_magic = magic;
a797bfc3	159	sb->s_op = &kernfs_sops;
fa736a95 TH	160	sb->s_time_gran = 1;
	161
	162	/* get root inode, initialize and unlock it */
a797bfc3	163	mutex_lock(&kernfs_mutex);
c637b8ac	164	inode = kernfs_get_inode(sb, info->root->kn);
a797bfc3	165	mutex_unlock(&kernfs_mutex);
fa736a95	166	if (!inode) {
c637b8ac	167	pr_debug("kernfs: could not get root inode\n");
fa736a95 TH	168	return -ENOMEM;
	169	}
	170
	171	/* instantiate and link root dentry */
	172	root = d_make_root(inode);
	173	if (!root) {
	174	pr_debug("%s: could not get root dentry!\n", __func__);
	175	return -ENOMEM;
	176	}
324a56e1 TH	177	kernfs_get(info->root->kn);
324a56e1 TH	178	root->d_fsdata = info->root->kn;
fa736a95	179	sb->s_root = root;
a797bfc3	180	sb->s_d_op = &kernfs_dops;
fa736a95 TH	181	return 0;
	182	}
	183
c637b8ac	184	static int kernfs_test_super(struct super_block sb, void data)
fa736a95	185	{
c525aadd TH	186	struct kernfs_super_info *sb_info = kernfs_info(sb);
c525aadd TH	187	struct kernfs_super_info *info = data;
fa736a95 TH	188
	189	return sb_info->root == info->root && sb_info->ns == info->ns;
	190	}
	191
c637b8ac	192	static int kernfs_set_super(struct super_block sb, void data)
fa736a95 TH	193	{
	194	int error;
	195	error = set_anon_super(sb, data);
	196	if (!error)
	197	sb->s_fs_info = data;
	198	return error;
	199	}
	200
	201	/**
	202	* kernfs_super_ns - determine the namespace tag of a kernfs super_block
	203	* @sb: super_block of interest
	204	*
	205	* Return the namespace tag associated with kernfs super_block @sb.
	206	*/
	207	const void kernfs_super_ns(struct super_block sb)
	208	{
c525aadd	209	struct kernfs_super_info *info = kernfs_info(sb);
fa736a95 TH	210
	211	return info->ns;
	212	}
	213
	214	/**
	215	* kernfs_mount_ns - kernfs mount helper
	216	* @fs_type: file_system_type of the fs being mounted
	217	* @flags: mount flags specified for the mount
	218	* @root: kernfs_root of the hierarchy being mounted
26fc9cd2	219	* @magic: file system specific magic number
fed95bab	220	* @new_sb_created: tell the caller if we allocated a new superblock
fa736a95 TH	221	* @ns: optional namespace tag of the mount
	222	*
	223	* This is to be called from each kernfs user's file_system_type->mount()
	224	* implementation, which should pass through the specified @fs_type and
	225	* @flags, and specify the hierarchy and namespace tag to mount via @root
	226	* and @ns, respectively.
	227	*
	228	* The return value can be passed to the vfs layer verbatim.
	229	*/
	230	struct dentry kernfs_mount_ns(struct file_system_type fs_type, int flags,
26fc9cd2 JZ	231	struct kernfs_root *root, unsigned long magic,
26fc9cd2 JZ	232	bool new_sb_created, const void ns)
fa736a95 TH	233	{
fa736a95 TH	234	struct super_block *sb;
c525aadd	235	struct kernfs_super_info *info;
fa736a95 TH	236	int error;
	237
	238	info = kzalloc(sizeof(*info), GFP_KERNEL);
	239	if (!info)
	240	return ERR_PTR(-ENOMEM);
	241
	242	info->root = root;
	243	info->ns = ns;
	244
c637b8ac	245	sb = sget(fs_type, kernfs_test_super, kernfs_set_super, flags, info);
fa736a95 TH	246	if (IS_ERR(sb) \|\| sb->s_fs_info != info)
	247	kfree(info);
	248	if (IS_ERR(sb))
	249	return ERR_CAST(sb);
fed95bab LZ	250
	251	if (new_sb_created)
	252	*new_sb_created = !sb->s_root;
	253
fa736a95	254	if (!sb->s_root) {
7d568a83 TH	255	struct kernfs_super_info *info = kernfs_info(sb);
7d568a83 TH	256
26fc9cd2	257	error = kernfs_fill_super(sb, magic);
fa736a95 TH	258	if (error) {
	259	deactivate_locked_super(sb);
	260	return ERR_PTR(error);
	261	}
	262	sb->s_flags \|= MS_ACTIVE;
7d568a83 TH	263
	264	mutex_lock(&kernfs_mutex);
	265	list_add(&info->node, &root->supers);
	266	mutex_unlock(&kernfs_mutex);
fa736a95 TH	267	}
	268
	269	return dget(sb->s_root);
	270	}
	271
	272	/**
	273	* kernfs_kill_sb - kill_sb for kernfs
	274	* @sb: super_block being killed
	275	*
	276	* This can be used directly for file_system_type->kill_sb(). If a kernfs
	277	* user needs extra cleanup, it can implement its own kill_sb() and call
	278	* this function at the end.
	279	*/
	280	void kernfs_kill_sb(struct super_block *sb)
	281	{
c525aadd	282	struct kernfs_super_info *info = kernfs_info(sb);
324a56e1	283	struct kernfs_node *root_kn = sb->s_root->d_fsdata;
fa736a95	284
7d568a83 TH	285	mutex_lock(&kernfs_mutex);
	286	list_del(&info->node);
	287	mutex_unlock(&kernfs_mutex);
	288
fa736a95 TH	289	/*
fa736a95 TH	290	* Remove the superblock from fs_supers/s_instances
c525aadd	291	* so we can't find it, before freeing kernfs_super_info.
fa736a95 TH	292	*/
	293	kill_anon_super(sb);
	294	kfree(info);
324a56e1	295	kernfs_put(root_kn);
fa736a95 TH	296	}
fa736a95 TH	297
4e26445f LZ	298	/**
	299	* kernfs_pin_sb: try to pin the superblock associated with a kernfs_root
	300	* @kernfs_root: the kernfs_root in question
	301	* @ns: the namespace tag
	302	*
	303	* Pin the superblock so the superblock won't be destroyed in subsequent
	304	* operations. This can be used to block ->kill_sb() which may be useful
	305	* for kernfs users which dynamically manage superblocks.
	306	*
	307	* Returns NULL if there's no superblock associated to this kernfs_root, or
	308	* -EINVAL if the superblock is being freed.
	309	*/
	310	struct super_block kernfs_pin_sb(struct kernfs_root root, const void *ns)
	311	{
	312	struct kernfs_super_info *info;
	313	struct super_block *sb = NULL;
	314
	315	mutex_lock(&kernfs_mutex);
	316	list_for_each_entry(info, &root->supers, node) {
	317	if (info->ns == ns) {
	318	sb = info->sb;
	319	if (!atomic_inc_not_zero(&info->sb->s_active))
	320	sb = ERR_PTR(-EINVAL);
	321	break;
	322	}
	323	}
	324	mutex_unlock(&kernfs_mutex);
	325	return sb;
	326	}
	327
fa736a95 TH	328	void __init kernfs_init(void)
fa736a95 TH	329	{
a797bfc3	330	kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
324a56e1	331	sizeof(struct kernfs_node),
fa736a95	332	0, SLAB_PANIC, NULL);
fa736a95	333	}