[linux-2.6-block.git] / fs / fs_struct.c

#include <linux/export.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/path.h>
#include <linux/slab.h>
#include <linux/fs_struct.h>
#include "internal.h"

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

	path_get(path);
	spin_lock(&fs->lock);
	write_seqcount_begin(&fs->seq);
	old_root = fs->root;
	fs->root = *path;
	write_seqcount_end(&fs->seq);
	spin_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, const struct path *path)
{
	struct path old_pwd;

	path_get(path);
	spin_lock(&fs->lock);
	write_seqcount_begin(&fs->seq);
	old_pwd = fs->pwd;
	fs->pwd = *path;
	write_seqcount_end(&fs->seq);
	spin_unlock(&fs->lock);

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

static inline int replace_path(struct path *p, const struct path *old, const struct path *new)
{
	if (likely(p->dentry != old->dentry || p->mnt != old->mnt))
		return 0;
	*p = *new;
	return 1;
}

void chroot_fs_refs(const struct path *old_root, const 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) {
			int hits = 0;
			spin_lock(&fs->lock);
			write_seqcount_begin(&fs->seq);
			hits += replace_path(&fs->root, old_root, new_root);
			hits += replace_path(&fs->pwd, old_root, new_root);
			write_seqcount_end(&fs->seq);
			while (hits--) {
				count++;
				path_get(new_root);
			}
			spin_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);
		spin_lock(&fs->lock);
		tsk->fs = NULL;
		kill = !--fs->users;
		spin_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;
		spin_lock_init(&fs->lock);
		seqcount_init(&fs->seq);
		fs->umask = old->umask;

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