[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 "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;
}

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,
};

/**
 * 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_CACHE_SIZE;
	sb->s_blocksize_bits = PAGE_CACHE_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>
fa736a95 TH	18
	19	#include "kernfs-internal.h"
	20
a797bfc3	21	struct kmem_cache *kernfs_node_cache;
fa736a95	22
6a7fed4e TH	23	static int kernfs_sop_remount_fs(struct super_block sb, int flags, char *data)
	24	{
	25	struct kernfs_root *root = kernfs_info(sb)->root;
	26	struct kernfs_syscall_ops *scops = root->syscall_ops;
	27
	28	if (scops && scops->remount_fs)
	29	return scops->remount_fs(root, flags, data);
	30	return 0;
	31	}
	32
	33	static int kernfs_sop_show_options(struct seq_file sf, struct dentry dentry)
	34	{
	35	struct kernfs_root *root = kernfs_root(dentry->d_fsdata);
	36	struct kernfs_syscall_ops *scops = root->syscall_ops;
	37
	38	if (scops && scops->show_options)
	39	return scops->show_options(sf, root);
	40	return 0;
	41	}
	42
f41c5934	43	const struct super_operations kernfs_sops = {
fa736a95 TH	44	.statfs = simple_statfs,
fa736a95 TH	45	.drop_inode = generic_delete_inode,
c637b8ac	46	.evict_inode = kernfs_evict_inode,
6a7fed4e TH	47
	48	.remount_fs = kernfs_sop_remount_fs,
	49	.show_options = kernfs_sop_show_options,
fa736a95 TH	50	};
fa736a95 TH	51
0c23b225 TH	52	/**
	53	* kernfs_root_from_sb - determine kernfs_root associated with a super_block
	54	* @sb: the super_block in question
	55	*
	56	* Return the kernfs_root associated with @sb. If @sb is not a kernfs one,
	57	* %NULL is returned.
	58	*/
	59	struct kernfs_root kernfs_root_from_sb(struct super_block sb)
	60	{
	61	if (sb->s_op == &kernfs_sops)
	62	return kernfs_info(sb)->root;
	63	return NULL;
	64	}
	65
fb3c8315 AK	66	/*
	67	* find the next ancestor in the path down to @child, where @parent was the
	68	* ancestor whose descendant we want to find.
	69	*
	70	* Say the path is /a/b/c/d. @child is d, @parent is NULL. We return the root
	71	* node. If @parent is b, then we return the node for c.
	72	* Passing in d as @parent is not ok.
	73	*/
	74	static struct kernfs_node find_next_ancestor(struct kernfs_node child,
	75	struct kernfs_node *parent)
	76	{
	77	if (child == parent) {
	78	pr_crit_once("BUG in find_next_ancestor: called with parent == child");
	79	return NULL;
	80	}
	81
	82	while (child->parent != parent) {
	83	if (!child->parent)
	84	return NULL;
	85	child = child->parent;
	86	}
	87
	88	return child;
	89	}
	90
	91	/**
	92	* kernfs_node_dentry - get a dentry for the given kernfs_node
	93	* @kn: kernfs_node for which a dentry is needed
	94	* @sb: the kernfs super_block
	95	*/
	96	struct dentry kernfs_node_dentry(struct kernfs_node kn,
	97	struct super_block *sb)
	98	{
	99	struct dentry *dentry;
	100	struct kernfs_node *knparent = NULL;
	101
	102	BUG_ON(sb->s_op != &kernfs_sops);
	103
	104	dentry = dget(sb->s_root);
	105
	106	/* Check if this is the root kernfs_node */
	107	if (!kn->parent)
	108	return dentry;
	109
	110	knparent = find_next_ancestor(kn, NULL);
	111	if (WARN_ON(!knparent))
	112	return ERR_PTR(-EINVAL);
	113
	114	do {
	115	struct dentry *dtmp;
	116	struct kernfs_node *kntmp;
	117
	118	if (kn == knparent)
	119	return dentry;
	120	kntmp = find_next_ancestor(kn, knparent);
	121	if (WARN_ON(!kntmp))
	122	return ERR_PTR(-EINVAL);
	123	mutex_lock(&d_inode(dentry)->i_mutex);
	124	dtmp = lookup_one_len(kntmp->name, dentry, strlen(kntmp->name));
	125	mutex_unlock(&d_inode(dentry)->i_mutex);
	126	dput(dentry);
	127	if (IS_ERR(dtmp))
	128	return dtmp;
	129	knparent = kntmp;
130	dentry = dtmp;
131	} while (true);
132	}
133
26fc9cd2	134	static int kernfs_fill_super(struct super_block *sb, unsigned long magic)
fa736a95	135	{
c525aadd	136	struct kernfs_super_info *info = kernfs_info(sb);
fa736a95 TH	137	struct inode *inode;
	138	struct dentry *root;
	139
7d568a83	140	info->sb = sb;
fa736a95 TH	141	sb->s_blocksize = PAGE_CACHE_SIZE;
fa736a95 TH	142	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
26fc9cd2	143	sb->s_magic = magic;
a797bfc3	144	sb->s_op = &kernfs_sops;
fa736a95 TH	145	sb->s_time_gran = 1;
	146
	147	/* get root inode, initialize and unlock it */
a797bfc3	148	mutex_lock(&kernfs_mutex);
c637b8ac	149	inode = kernfs_get_inode(sb, info->root->kn);
a797bfc3	150	mutex_unlock(&kernfs_mutex);
fa736a95	151	if (!inode) {
c637b8ac	152	pr_debug("kernfs: could not get root inode\n");
fa736a95 TH	153	return -ENOMEM;
	154	}
	155
	156	/* instantiate and link root dentry */
	157	root = d_make_root(inode);
	158	if (!root) {
	159	pr_debug("%s: could not get root dentry!\n", __func__);
	160	return -ENOMEM;
	161	}
324a56e1 TH	162	kernfs_get(info->root->kn);
324a56e1 TH	163	root->d_fsdata = info->root->kn;
fa736a95	164	sb->s_root = root;
a797bfc3	165	sb->s_d_op = &kernfs_dops;
fa736a95 TH	166	return 0;
	167	}
	168
c637b8ac	169	static int kernfs_test_super(struct super_block sb, void data)
fa736a95	170	{
c525aadd TH	171	struct kernfs_super_info *sb_info = kernfs_info(sb);
c525aadd TH	172	struct kernfs_super_info *info = data;
fa736a95 TH	173
	174	return sb_info->root == info->root && sb_info->ns == info->ns;
	175	}
	176
c637b8ac	177	static int kernfs_set_super(struct super_block sb, void data)
fa736a95 TH	178	{
	179	int error;
	180	error = set_anon_super(sb, data);
	181	if (!error)
	182	sb->s_fs_info = data;
	183	return error;
	184	}
	185
	186	/**
	187	* kernfs_super_ns - determine the namespace tag of a kernfs super_block
	188	* @sb: super_block of interest
	189	*
	190	* Return the namespace tag associated with kernfs super_block @sb.
	191	*/
	192	const void kernfs_super_ns(struct super_block sb)
	193	{
c525aadd	194	struct kernfs_super_info *info = kernfs_info(sb);
fa736a95 TH	195
	196	return info->ns;
	197	}
	198
	199	/**
	200	* kernfs_mount_ns - kernfs mount helper
	201	* @fs_type: file_system_type of the fs being mounted
	202	* @flags: mount flags specified for the mount
	203	* @root: kernfs_root of the hierarchy being mounted
26fc9cd2	204	* @magic: file system specific magic number
fed95bab	205	* @new_sb_created: tell the caller if we allocated a new superblock
fa736a95 TH	206	* @ns: optional namespace tag of the mount
	207	*
	208	* This is to be called from each kernfs user's file_system_type->mount()
	209	* implementation, which should pass through the specified @fs_type and
	210	* @flags, and specify the hierarchy and namespace tag to mount via @root
	211	* and @ns, respectively.
	212	*
	213	* The return value can be passed to the vfs layer verbatim.
	214	*/
	215	struct dentry kernfs_mount_ns(struct file_system_type fs_type, int flags,
26fc9cd2 JZ	216	struct kernfs_root *root, unsigned long magic,
26fc9cd2 JZ	217	bool new_sb_created, const void ns)
fa736a95 TH	218	{
fa736a95 TH	219	struct super_block *sb;
c525aadd	220	struct kernfs_super_info *info;
fa736a95 TH	221	int error;
	222
	223	info = kzalloc(sizeof(*info), GFP_KERNEL);
	224	if (!info)
	225	return ERR_PTR(-ENOMEM);
	226
	227	info->root = root;
	228	info->ns = ns;
	229
c637b8ac	230	sb = sget(fs_type, kernfs_test_super, kernfs_set_super, flags, info);
fa736a95 TH	231	if (IS_ERR(sb) \|\| sb->s_fs_info != info)
	232	kfree(info);
	233	if (IS_ERR(sb))
	234	return ERR_CAST(sb);
fed95bab LZ	235
	236	if (new_sb_created)
	237	*new_sb_created = !sb->s_root;
	238
fa736a95	239	if (!sb->s_root) {
7d568a83 TH	240	struct kernfs_super_info *info = kernfs_info(sb);
7d568a83 TH	241
26fc9cd2	242	error = kernfs_fill_super(sb, magic);
fa736a95 TH	243	if (error) {
	244	deactivate_locked_super(sb);
	245	return ERR_PTR(error);
	246	}
	247	sb->s_flags \|= MS_ACTIVE;
7d568a83 TH	248
	249	mutex_lock(&kernfs_mutex);
	250	list_add(&info->node, &root->supers);
	251	mutex_unlock(&kernfs_mutex);
fa736a95 TH	252	}
	253
	254	return dget(sb->s_root);
	255	}
	256
	257	/**
	258	* kernfs_kill_sb - kill_sb for kernfs
	259	* @sb: super_block being killed
	260	*
	261	* This can be used directly for file_system_type->kill_sb(). If a kernfs
	262	* user needs extra cleanup, it can implement its own kill_sb() and call
	263	* this function at the end.
	264	*/
	265	void kernfs_kill_sb(struct super_block *sb)
	266	{
c525aadd	267	struct kernfs_super_info *info = kernfs_info(sb);
324a56e1	268	struct kernfs_node *root_kn = sb->s_root->d_fsdata;
fa736a95	269
7d568a83 TH	270	mutex_lock(&kernfs_mutex);
	271	list_del(&info->node);
	272	mutex_unlock(&kernfs_mutex);
	273
fa736a95 TH	274	/*
fa736a95 TH	275	* Remove the superblock from fs_supers/s_instances
c525aadd	276	* so we can't find it, before freeing kernfs_super_info.
fa736a95 TH	277	*/
	278	kill_anon_super(sb);
	279	kfree(info);
324a56e1	280	kernfs_put(root_kn);
fa736a95 TH	281	}
fa736a95 TH	282
4e26445f LZ	283	/**
	284	* kernfs_pin_sb: try to pin the superblock associated with a kernfs_root
	285	* @kernfs_root: the kernfs_root in question
	286	* @ns: the namespace tag
	287	*
	288	* Pin the superblock so the superblock won't be destroyed in subsequent
	289	* operations. This can be used to block ->kill_sb() which may be useful
	290	* for kernfs users which dynamically manage superblocks.
	291	*
	292	* Returns NULL if there's no superblock associated to this kernfs_root, or
	293	* -EINVAL if the superblock is being freed.
	294	*/
	295	struct super_block kernfs_pin_sb(struct kernfs_root root, const void *ns)
	296	{
	297	struct kernfs_super_info *info;
	298	struct super_block *sb = NULL;
	299
	300	mutex_lock(&kernfs_mutex);
	301	list_for_each_entry(info, &root->supers, node) {
	302	if (info->ns == ns) {
	303	sb = info->sb;
	304	if (!atomic_inc_not_zero(&info->sb->s_active))
	305	sb = ERR_PTR(-EINVAL);
	306	break;
	307	}
	308	}
	309	mutex_unlock(&kernfs_mutex);
	310	return sb;
	311	}
	312
fa736a95 TH	313	void __init kernfs_init(void)
fa736a95 TH	314	{
a797bfc3	315	kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
324a56e1	316	sizeof(struct kernfs_node),
fa736a95	317	0, SLAB_PANIC, NULL);
fa736a95	318	}