[linux.git] / fs / fs_struct.c

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/path.h>
#include <linux/slab.h>
#include <linux/fs_struct.h>

/*
 * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
 * It can block.
 */
void set_fs_root(struct fs_struct *fs, struct path *path)
{
	struct path old_root;

	write_lock(&fs->lock);
	old_root = fs->root;
	fs->root = *path;
	path_get(path);
	write_unlock(&fs->lock);
	if (old_root.dentry)
		path_put(&old_root);
}

/*
 * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
 * It can block.
 */
void set_fs_pwd(struct fs_struct *fs, struct path *path)
{
	struct path old_pwd;

	write_lock(&fs->lock);
	old_pwd = fs->pwd;
	fs->pwd = *path;
	path_get(path);
	write_unlock(&fs->lock);

	if (old_pwd.dentry)
		path_put(&old_pwd);
}

void chroot_fs_refs(struct path *old_root, struct path *new_root)
{
	struct task_struct *g, *p;
	struct fs_struct *fs;
	int count = 0;

	read_lock(&tasklist_lock);
	do_each_thread(g, p) {
		task_lock(p);
		fs = p->fs;
		if (fs) {
			write_lock(&fs->lock);
			if (fs->root.dentry == old_root->dentry
			    && fs->root.mnt == old_root->mnt) {
				path_get(new_root);
				fs->root = *new_root;
				count++;
			}
			if (fs->pwd.dentry == old_root->dentry
			    && fs->pwd.mnt == old_root->mnt) {
				path_get(new_root);
				fs->pwd = *new_root;
				count++;
			}
			write_unlock(&fs->lock);
		}
		task_unlock(p);
	} while_each_thread(g, p);
	read_unlock(&tasklist_lock);
	while (count--)
		path_put(old_root);
}

void free_fs_struct(struct fs_struct *fs)
{
	path_put(&fs->root);
	path_put(&fs->pwd);
	kmem_cache_free(fs_cachep, fs);
}

void exit_fs(struct task_struct *tsk)
{
	struct fs_struct *fs = tsk->fs;

	if (fs) {
		int kill;
		task_lock(tsk);
		write_lock(&fs->lock);
		tsk->fs = NULL;
		kill = !--fs->users;
		write_unlock(&fs->lock);
		task_unlock(tsk);
		if (kill)
			free_fs_struct(fs);
	}
}

struct fs_struct *copy_fs_struct(struct fs_struct *old)
{
	struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
	/* We don't need to lock fs - think why ;-) */
	if (fs) {
		fs->users = 1;
		fs->in_exec = 0;
		rwlock_init(&fs->lock);
		fs->umask = old->umask;
		read_lock(&old->lock);
		fs->root = old->root;
		path_get(&old->root);
		fs->pwd = old->pwd;
		path_get(&old->pwd);
		read_unlock(&old->lock);
	}
	return fs;
}

int unshare_fs_struct(void)
{
	struct fs_struct *fs = current->fs;
	struct fs_struct *new_fs = copy_fs_struct(fs);
	int kill;

	if (!new_fs)
		return -ENOMEM;

	task_lock(current);
	write_lock(&fs->lock);
	kill = !--fs->users;
	current->fs = new_fs;
	write_unlock(&fs->lock);
	task_unlock(current);

	if (kill)
		free_fs_struct(fs);

	return 0;
}
EXPORT_SYMBOL_GPL(unshare_fs_struct);

int current_umask(void)
{
	return current->fs->umask;
}
EXPORT_SYMBOL(current_umask);

/* to be mentioned only in INIT_TASK */
struct fs_struct init_fs = {
	.users		= 1,
	.lock		= __RW_LOCK_UNLOCKED(init_fs.lock),
	.umask		= 0022,
};

void daemonize_fs_struct(void)
{
	struct fs_struct *fs = current->fs;

	if (fs) {
		int kill;

		task_lock(current);

		write_lock(&init_fs.lock);
		init_fs.users++;
		write_unlock(&init_fs.lock);

		write_lock(&fs->lock);
		current->fs = &init_fs;
		kill = !--fs->users;
		write_unlock(&fs->lock);

		task_unlock(current);
		if (kill)
			free_fs_struct(fs);
	}
}
Commit	Line	Data
3e93cd67 AV	1	#include <linux/module.h>
	2	#include <linux/sched.h>
	3	#include <linux/fs.h>
	4	#include <linux/path.h>
	5	#include <linux/slab.h>
5ad4e53b	6	#include <linux/fs_struct.h>
3e93cd67 AV	7
	8	/*
	9	* Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
	10	* It can block.
	11	*/
	12	void set_fs_root(struct fs_struct fs, struct path path)
	13	{
	14	struct path old_root;
	15
	16	write_lock(&fs->lock);
	17	old_root = fs->root;
	18	fs->root = *path;
	19	path_get(path);
	20	write_unlock(&fs->lock);
	21	if (old_root.dentry)
	22	path_put(&old_root);
	23	}
	24
	25	/*
	26	* Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
	27	* It can block.
	28	*/
	29	void set_fs_pwd(struct fs_struct fs, struct path path)
	30	{
	31	struct path old_pwd;
	32
	33	write_lock(&fs->lock);
	34	old_pwd = fs->pwd;
	35	fs->pwd = *path;
	36	path_get(path);
	37	write_unlock(&fs->lock);
	38
	39	if (old_pwd.dentry)
	40	path_put(&old_pwd);
	41	}
	42
	43	void chroot_fs_refs(struct path old_root, struct path new_root)
	44	{
	45	struct task_struct g, p;
	46	struct fs_struct *fs;
	47	int count = 0;
	48
	49	read_lock(&tasklist_lock);
	50	do_each_thread(g, p) {
	51	task_lock(p);
	52	fs = p->fs;
	53	if (fs) {
	54	write_lock(&fs->lock);
	55	if (fs->root.dentry == old_root->dentry
	56	&& fs->root.mnt == old_root->mnt) {
	57	path_get(new_root);
	58	fs->root = *new_root;
	59	count++;
	60	}
	61	if (fs->pwd.dentry == old_root->dentry
	62	&& fs->pwd.mnt == old_root->mnt) {
	63	path_get(new_root);
	64	fs->pwd = *new_root;
	65	count++;
	66	}
	67	write_unlock(&fs->lock);
	68	}
	69	task_unlock(p);
	70	} while_each_thread(g, p);
71	read_unlock(&tasklist_lock);
72	while (count--)
73	path_put(old_root);
74	}
75
498052bb	76	void free_fs_struct(struct fs_struct *fs)
3e93cd67	77	{
498052bb AV	78	path_put(&fs->root);
	79	path_put(&fs->pwd);
	80	kmem_cache_free(fs_cachep, fs);
3e93cd67 AV	81	}
	82
	83	void exit_fs(struct task_struct *tsk)
	84	{
498052bb	85	struct fs_struct *fs = tsk->fs;
3e93cd67 AV	86
3e93cd67 AV	87	if (fs) {
498052bb	88	int kill;
3e93cd67	89	task_lock(tsk);
498052bb	90	write_lock(&fs->lock);
3e93cd67	91	tsk->fs = NULL;
498052bb AV	92	kill = !--fs->users;
498052bb AV	93	write_unlock(&fs->lock);
3e93cd67	94	task_unlock(tsk);
498052bb AV	95	if (kill)
498052bb AV	96	free_fs_struct(fs);
3e93cd67 AV	97	}
	98	}
	99
	100	struct fs_struct copy_fs_struct(struct fs_struct old)
	101	{
	102	struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
	103	/* We don't need to lock fs - think why ;-) */
	104	if (fs) {
498052bb AV	105	fs->users = 1;
498052bb AV	106	fs->in_exec = 0;
3e93cd67 AV	107	rwlock_init(&fs->lock);
	108	fs->umask = old->umask;
	109	read_lock(&old->lock);
	110	fs->root = old->root;
	111	path_get(&old->root);
	112	fs->pwd = old->pwd;
	113	path_get(&old->pwd);
	114	read_unlock(&old->lock);
	115	}
	116	return fs;
	117	}
	118
	119	int unshare_fs_struct(void)
	120	{
498052bb AV	121	struct fs_struct *fs = current->fs;
	122	struct fs_struct *new_fs = copy_fs_struct(fs);
	123	int kill;
	124
	125	if (!new_fs)
3e93cd67	126	return -ENOMEM;
498052bb AV	127
	128	task_lock(current);
	129	write_lock(&fs->lock);
	130	kill = !--fs->users;
	131	current->fs = new_fs;
	132	write_unlock(&fs->lock);
	133	task_unlock(current);
	134
	135	if (kill)
	136	free_fs_struct(fs);
	137
3e93cd67 AV	138	return 0;
	139	}
	140	EXPORT_SYMBOL_GPL(unshare_fs_struct);
	141
ce3b0f8d AV	142	int current_umask(void)
	143	{
	144	return current->fs->umask;
	145	}
	146	EXPORT_SYMBOL(current_umask);
	147
3e93cd67 AV	148	/* to be mentioned only in INIT_TASK */
3e93cd67 AV	149	struct fs_struct init_fs = {
498052bb	150	.users = 1,
3e93cd67 AV	151	.lock = __RW_LOCK_UNLOCKED(init_fs.lock),
	152	.umask = 0022,
	153	};
	154
	155	void daemonize_fs_struct(void)
	156	{
498052bb AV	157	struct fs_struct *fs = current->fs;
	158
	159	if (fs) {
	160	int kill;
	161
	162	task_lock(current);
3e93cd67	163
498052bb AV	164	write_lock(&init_fs.lock);
	165	init_fs.users++;
	166	write_unlock(&init_fs.lock);
	167
	168	write_lock(&fs->lock);
	169	current->fs = &init_fs;
	170	kill = !--fs->users;
	171	write_unlock(&fs->lock);
	172
	173	task_unlock(current);
	174	if (kill)
	175	free_fs_struct(fs);
	176	}
3e93cd67	177	}