namespace.c 44.4 KB
Newer Older
L
Linus Torvalds 已提交
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
/*
 *  linux/fs/namespace.c
 *
 * (C) Copyright Al Viro 2000, 2001
 *	Released under GPL v2.
 *
 * Based on code from fs/super.c, copyright Linus Torvalds and others.
 * Heavily rewritten.
 */

#include <linux/config.h>
#include <linux/syscalls.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/smp_lock.h>
#include <linux/init.h>
#include <linux/quotaops.h>
#include <linux/acct.h>
19
#include <linux/capability.h>
L
Linus Torvalds 已提交
20 21 22 23 24 25 26 27
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/namespace.h>
#include <linux/namei.h>
#include <linux/security.h>
#include <linux/mount.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
28
#include "pnode.h"
L
Linus Torvalds 已提交
29 30 31 32 33 34 35 36 37 38 39 40 41

extern int __init init_rootfs(void);

#ifdef CONFIG_SYSFS
extern int __init sysfs_init(void);
#else
static inline int sysfs_init(void)
{
	return 0;
}
#endif

/* spinlock for vfsmount related operations, inplace of dcache_lock */
A
Al Viro 已提交
42 43 44
__cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock);

static int event;
L
Linus Torvalds 已提交
45 46

static struct list_head *mount_hashtable;
47
static int hash_mask __read_mostly, hash_bits __read_mostly;
R
Ram Pai 已提交
48
static kmem_cache_t *mnt_cache;
R
Ram Pai 已提交
49
static struct rw_semaphore namespace_sem;
L
Linus Torvalds 已提交
50

M
Miklos Szeredi 已提交
51 52 53 54
/* /sys/fs */
decl_subsys(fs, NULL, NULL);
EXPORT_SYMBOL_GPL(fs_subsys);

L
Linus Torvalds 已提交
55 56
static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry)
{
R
Ram Pai 已提交
57 58
	unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
	tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
L
Linus Torvalds 已提交
59 60 61 62 63 64
	tmp = tmp + (tmp >> hash_bits);
	return tmp & hash_mask;
}

struct vfsmount *alloc_vfsmnt(const char *name)
{
R
Ram Pai 已提交
65
	struct vfsmount *mnt = kmem_cache_alloc(mnt_cache, GFP_KERNEL);
L
Linus Torvalds 已提交
66 67
	if (mnt) {
		memset(mnt, 0, sizeof(struct vfsmount));
R
Ram Pai 已提交
68
		atomic_set(&mnt->mnt_count, 1);
L
Linus Torvalds 已提交
69 70 71 72
		INIT_LIST_HEAD(&mnt->mnt_hash);
		INIT_LIST_HEAD(&mnt->mnt_child);
		INIT_LIST_HEAD(&mnt->mnt_mounts);
		INIT_LIST_HEAD(&mnt->mnt_list);
73
		INIT_LIST_HEAD(&mnt->mnt_expire);
R
Ram Pai 已提交
74
		INIT_LIST_HEAD(&mnt->mnt_share);
R
Ram Pai 已提交
75 76
		INIT_LIST_HEAD(&mnt->mnt_slave_list);
		INIT_LIST_HEAD(&mnt->mnt_slave);
L
Linus Torvalds 已提交
77
		if (name) {
R
Ram Pai 已提交
78
			int size = strlen(name) + 1;
L
Linus Torvalds 已提交
79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95
			char *newname = kmalloc(size, GFP_KERNEL);
			if (newname) {
				memcpy(newname, name, size);
				mnt->mnt_devname = newname;
			}
		}
	}
	return mnt;
}

void free_vfsmnt(struct vfsmount *mnt)
{
	kfree(mnt->mnt_devname);
	kmem_cache_free(mnt_cache, mnt);
}

/*
R
Ram Pai 已提交
96 97
 * find the first or last mount at @dentry on vfsmount @mnt depending on
 * @dir. If @dir is set return the first mount else return the last mount.
L
Linus Torvalds 已提交
98
 */
R
Ram Pai 已提交
99 100
struct vfsmount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry,
			      int dir)
L
Linus Torvalds 已提交
101
{
R
Ram Pai 已提交
102 103
	struct list_head *head = mount_hashtable + hash(mnt, dentry);
	struct list_head *tmp = head;
L
Linus Torvalds 已提交
104 105 106
	struct vfsmount *p, *found = NULL;

	for (;;) {
R
Ram Pai 已提交
107
		tmp = dir ? tmp->next : tmp->prev;
L
Linus Torvalds 已提交
108 109 110 111 112
		p = NULL;
		if (tmp == head)
			break;
		p = list_entry(tmp, struct vfsmount, mnt_hash);
		if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) {
R
Ram Pai 已提交
113
			found = p;
L
Linus Torvalds 已提交
114 115 116 117 118 119
			break;
		}
	}
	return found;
}

R
Ram Pai 已提交
120 121 122 123 124 125 126 127 128 129 130 131 132 133
/*
 * lookup_mnt increments the ref count before returning
 * the vfsmount struct.
 */
struct vfsmount *lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
{
	struct vfsmount *child_mnt;
	spin_lock(&vfsmount_lock);
	if ((child_mnt = __lookup_mnt(mnt, dentry, 1)))
		mntget(child_mnt);
	spin_unlock(&vfsmount_lock);
	return child_mnt;
}

L
Linus Torvalds 已提交
134 135 136 137 138
static inline int check_mnt(struct vfsmount *mnt)
{
	return mnt->mnt_namespace == current->namespace;
}

A
Al Viro 已提交
139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154
static void touch_namespace(struct namespace *ns)
{
	if (ns) {
		ns->event = ++event;
		wake_up_interruptible(&ns->poll);
	}
}

static void __touch_namespace(struct namespace *ns)
{
	if (ns && ns->event != event) {
		ns->event = event;
		wake_up_interruptible(&ns->poll);
	}
}

L
Linus Torvalds 已提交
155 156 157 158 159 160 161 162 163 164 165
static void detach_mnt(struct vfsmount *mnt, struct nameidata *old_nd)
{
	old_nd->dentry = mnt->mnt_mountpoint;
	old_nd->mnt = mnt->mnt_parent;
	mnt->mnt_parent = mnt;
	mnt->mnt_mountpoint = mnt->mnt_root;
	list_del_init(&mnt->mnt_child);
	list_del_init(&mnt->mnt_hash);
	old_nd->dentry->d_mounted--;
}

166 167 168 169 170 171 172 173
void mnt_set_mountpoint(struct vfsmount *mnt, struct dentry *dentry,
			struct vfsmount *child_mnt)
{
	child_mnt->mnt_parent = mntget(mnt);
	child_mnt->mnt_mountpoint = dget(dentry);
	dentry->d_mounted++;
}

L
Linus Torvalds 已提交
174 175
static void attach_mnt(struct vfsmount *mnt, struct nameidata *nd)
{
176 177 178
	mnt_set_mountpoint(nd->mnt, nd->dentry, mnt);
	list_add_tail(&mnt->mnt_hash, mount_hashtable +
			hash(nd->mnt, nd->dentry));
L
Linus Torvalds 已提交
179
	list_add_tail(&mnt->mnt_child, &nd->mnt->mnt_mounts);
180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202
}

/*
 * the caller must hold vfsmount_lock
 */
static void commit_tree(struct vfsmount *mnt)
{
	struct vfsmount *parent = mnt->mnt_parent;
	struct vfsmount *m;
	LIST_HEAD(head);
	struct namespace *n = parent->mnt_namespace;

	BUG_ON(parent == mnt);

	list_add_tail(&head, &mnt->mnt_list);
	list_for_each_entry(m, &head, mnt_list)
		m->mnt_namespace = n;
	list_splice(&head, n->list.prev);

	list_add_tail(&mnt->mnt_hash, mount_hashtable +
				hash(parent, mnt->mnt_mountpoint));
	list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
	touch_namespace(n);
L
Linus Torvalds 已提交
203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220
}

static struct vfsmount *next_mnt(struct vfsmount *p, struct vfsmount *root)
{
	struct list_head *next = p->mnt_mounts.next;
	if (next == &p->mnt_mounts) {
		while (1) {
			if (p == root)
				return NULL;
			next = p->mnt_child.next;
			if (next != &p->mnt_parent->mnt_mounts)
				break;
			p = p->mnt_parent;
		}
	}
	return list_entry(next, struct vfsmount, mnt_child);
}

R
Ram Pai 已提交
221 222 223 224 225 226 227 228 229 230
static struct vfsmount *skip_mnt_tree(struct vfsmount *p)
{
	struct list_head *prev = p->mnt_mounts.prev;
	while (prev != &p->mnt_mounts) {
		p = list_entry(prev, struct vfsmount, mnt_child);
		prev = p->mnt_mounts.prev;
	}
	return p;
}

R
Ram Pai 已提交
231 232
static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root,
					int flag)
L
Linus Torvalds 已提交
233 234 235 236 237 238 239 240 241 242 243
{
	struct super_block *sb = old->mnt_sb;
	struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname);

	if (mnt) {
		mnt->mnt_flags = old->mnt_flags;
		atomic_inc(&sb->s_active);
		mnt->mnt_sb = sb;
		mnt->mnt_root = dget(root);
		mnt->mnt_mountpoint = mnt->mnt_root;
		mnt->mnt_parent = mnt;
244

R
Ram Pai 已提交
245 246 247 248 249 250 251 252 253 254 255
		if (flag & CL_SLAVE) {
			list_add(&mnt->mnt_slave, &old->mnt_slave_list);
			mnt->mnt_master = old;
			CLEAR_MNT_SHARED(mnt);
		} else {
			if ((flag & CL_PROPAGATION) || IS_MNT_SHARED(old))
				list_add(&mnt->mnt_share, &old->mnt_share);
			if (IS_MNT_SLAVE(old))
				list_add(&mnt->mnt_slave, &old->mnt_slave);
			mnt->mnt_master = old->mnt_master;
		}
256 257
		if (flag & CL_MAKE_SHARED)
			set_mnt_shared(mnt);
L
Linus Torvalds 已提交
258 259 260

		/* stick the duplicate mount on the same expiry list
		 * as the original if that was on one */
R
Ram Pai 已提交
261 262 263 264 265 266
		if (flag & CL_EXPIRE) {
			spin_lock(&vfsmount_lock);
			if (!list_empty(&old->mnt_expire))
				list_add(&mnt->mnt_expire, &old->mnt_expire);
			spin_unlock(&vfsmount_lock);
		}
L
Linus Torvalds 已提交
267 268 269 270
	}
	return mnt;
}

271
static inline void __mntput(struct vfsmount *mnt)
L
Linus Torvalds 已提交
272 273 274 275 276 277 278
{
	struct super_block *sb = mnt->mnt_sb;
	dput(mnt->mnt_root);
	free_vfsmnt(mnt);
	deactivate_super(sb);
}

279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318
void mntput_no_expire(struct vfsmount *mnt)
{
repeat:
	if (atomic_dec_and_lock(&mnt->mnt_count, &vfsmount_lock)) {
		if (likely(!mnt->mnt_pinned)) {
			spin_unlock(&vfsmount_lock);
			__mntput(mnt);
			return;
		}
		atomic_add(mnt->mnt_pinned + 1, &mnt->mnt_count);
		mnt->mnt_pinned = 0;
		spin_unlock(&vfsmount_lock);
		acct_auto_close_mnt(mnt);
		security_sb_umount_close(mnt);
		goto repeat;
	}
}

EXPORT_SYMBOL(mntput_no_expire);

void mnt_pin(struct vfsmount *mnt)
{
	spin_lock(&vfsmount_lock);
	mnt->mnt_pinned++;
	spin_unlock(&vfsmount_lock);
}

EXPORT_SYMBOL(mnt_pin);

void mnt_unpin(struct vfsmount *mnt)
{
	spin_lock(&vfsmount_lock);
	if (mnt->mnt_pinned) {
		atomic_inc(&mnt->mnt_count);
		mnt->mnt_pinned--;
	}
	spin_unlock(&vfsmount_lock);
}

EXPORT_SYMBOL(mnt_unpin);
L
Linus Torvalds 已提交
319 320 321 322 323 324 325 326

/* iterator */
static void *m_start(struct seq_file *m, loff_t *pos)
{
	struct namespace *n = m->private;
	struct list_head *p;
	loff_t l = *pos;

R
Ram Pai 已提交
327
	down_read(&namespace_sem);
L
Linus Torvalds 已提交
328 329 330 331 332 333 334 335 336 337 338
	list_for_each(p, &n->list)
		if (!l--)
			return list_entry(p, struct vfsmount, mnt_list);
	return NULL;
}

static void *m_next(struct seq_file *m, void *v, loff_t *pos)
{
	struct namespace *n = m->private;
	struct list_head *p = ((struct vfsmount *)v)->mnt_list.next;
	(*pos)++;
R
Ram Pai 已提交
339
	return p == &n->list ? NULL : list_entry(p, struct vfsmount, mnt_list);
L
Linus Torvalds 已提交
340 341 342 343
}

static void m_stop(struct seq_file *m, void *v)
{
R
Ram Pai 已提交
344
	up_read(&namespace_sem);
L
Linus Torvalds 已提交
345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368
}

static inline void mangle(struct seq_file *m, const char *s)
{
	seq_escape(m, s, " \t\n\\");
}

static int show_vfsmnt(struct seq_file *m, void *v)
{
	struct vfsmount *mnt = v;
	int err = 0;
	static struct proc_fs_info {
		int flag;
		char *str;
	} fs_info[] = {
		{ MS_SYNCHRONOUS, ",sync" },
		{ MS_DIRSYNC, ",dirsync" },
		{ MS_MANDLOCK, ",mand" },
		{ 0, NULL }
	};
	static struct proc_fs_info mnt_info[] = {
		{ MNT_NOSUID, ",nosuid" },
		{ MNT_NODEV, ",nodev" },
		{ MNT_NOEXEC, ",noexec" },
369 370
		{ MNT_NOATIME, ",noatime" },
		{ MNT_NODIRATIME, ",nodiratime" },
L
Linus Torvalds 已提交
371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411
		{ 0, NULL }
	};
	struct proc_fs_info *fs_infop;

	mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
	seq_putc(m, ' ');
	seq_path(m, mnt, mnt->mnt_root, " \t\n\\");
	seq_putc(m, ' ');
	mangle(m, mnt->mnt_sb->s_type->name);
	seq_puts(m, mnt->mnt_sb->s_flags & MS_RDONLY ? " ro" : " rw");
	for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
		if (mnt->mnt_sb->s_flags & fs_infop->flag)
			seq_puts(m, fs_infop->str);
	}
	for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {
		if (mnt->mnt_flags & fs_infop->flag)
			seq_puts(m, fs_infop->str);
	}
	if (mnt->mnt_sb->s_op->show_options)
		err = mnt->mnt_sb->s_op->show_options(m, mnt);
	seq_puts(m, " 0 0\n");
	return err;
}

struct seq_operations mounts_op = {
	.start	= m_start,
	.next	= m_next,
	.stop	= m_stop,
	.show	= show_vfsmnt
};

/**
 * may_umount_tree - check if a mount tree is busy
 * @mnt: root of mount tree
 *
 * This is called to check if a tree of mounts has any
 * open files, pwds, chroots or sub mounts that are
 * busy.
 */
int may_umount_tree(struct vfsmount *mnt)
{
R
Ram Pai 已提交
412 413 414
	int actual_refs = 0;
	int minimum_refs = 0;
	struct vfsmount *p;
L
Linus Torvalds 已提交
415 416

	spin_lock(&vfsmount_lock);
R
Ram Pai 已提交
417
	for (p = mnt; p; p = next_mnt(p, mnt)) {
L
Linus Torvalds 已提交
418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445
		actual_refs += atomic_read(&p->mnt_count);
		minimum_refs += 2;
	}
	spin_unlock(&vfsmount_lock);

	if (actual_refs > minimum_refs)
		return -EBUSY;

	return 0;
}

EXPORT_SYMBOL(may_umount_tree);

/**
 * may_umount - check if a mount point is busy
 * @mnt: root of mount
 *
 * This is called to check if a mount point has any
 * open files, pwds, chroots or sub mounts. If the
 * mount has sub mounts this will return busy
 * regardless of whether the sub mounts are busy.
 *
 * Doesn't take quota and stuff into account. IOW, in some cases it will
 * give false negatives. The main reason why it's here is that we need
 * a non-destructive way to look for easily umountable filesystems.
 */
int may_umount(struct vfsmount *mnt)
{
R
Ram Pai 已提交
446 447 448 449 450 451
	int ret = 0;
	spin_lock(&vfsmount_lock);
	if (propagate_mount_busy(mnt, 2))
		ret = -EBUSY;
	spin_unlock(&vfsmount_lock);
	return ret;
L
Linus Torvalds 已提交
452 453 454 455
}

EXPORT_SYMBOL(may_umount);

456
void release_mounts(struct list_head *head)
R
Ram Pai 已提交
457 458
{
	struct vfsmount *mnt;
M
Miklos Szeredi 已提交
459
	while (!list_empty(head)) {
R
Ram Pai 已提交
460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477
		mnt = list_entry(head->next, struct vfsmount, mnt_hash);
		list_del_init(&mnt->mnt_hash);
		if (mnt->mnt_parent != mnt) {
			struct dentry *dentry;
			struct vfsmount *m;
			spin_lock(&vfsmount_lock);
			dentry = mnt->mnt_mountpoint;
			m = mnt->mnt_parent;
			mnt->mnt_mountpoint = mnt->mnt_root;
			mnt->mnt_parent = mnt;
			spin_unlock(&vfsmount_lock);
			dput(dentry);
			mntput(m);
		}
		mntput(mnt);
	}
}

R
Ram Pai 已提交
478
void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill)
L
Linus Torvalds 已提交
479 480 481 482
{
	struct vfsmount *p;

	for (p = mnt; p; p = next_mnt(p, mnt)) {
R
Ram Pai 已提交
483 484
		list_del(&p->mnt_hash);
		list_add(&p->mnt_hash, kill);
L
Linus Torvalds 已提交
485 486
	}

R
Ram Pai 已提交
487 488 489
	if (propagate)
		propagate_umount(kill);

R
Ram Pai 已提交
490 491 492 493 494 495 496 497
	list_for_each_entry(p, kill, mnt_hash) {
		list_del_init(&p->mnt_expire);
		list_del_init(&p->mnt_list);
		__touch_namespace(p->mnt_namespace);
		p->mnt_namespace = NULL;
		list_del_init(&p->mnt_child);
		if (p->mnt_parent != p)
			mnt->mnt_mountpoint->d_mounted--;
R
Ram Pai 已提交
498
		change_mnt_propagation(p, MS_PRIVATE);
L
Linus Torvalds 已提交
499 500 501 502 503
	}
}

static int do_umount(struct vfsmount *mnt, int flags)
{
R
Ram Pai 已提交
504
	struct super_block *sb = mnt->mnt_sb;
L
Linus Torvalds 已提交
505
	int retval;
R
Ram Pai 已提交
506
	LIST_HEAD(umount_list);
L
Linus Torvalds 已提交
507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540

	retval = security_sb_umount(mnt, flags);
	if (retval)
		return retval;

	/*
	 * Allow userspace to request a mountpoint be expired rather than
	 * unmounting unconditionally. Unmount only happens if:
	 *  (1) the mark is already set (the mark is cleared by mntput())
	 *  (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
	 */
	if (flags & MNT_EXPIRE) {
		if (mnt == current->fs->rootmnt ||
		    flags & (MNT_FORCE | MNT_DETACH))
			return -EINVAL;

		if (atomic_read(&mnt->mnt_count) != 2)
			return -EBUSY;

		if (!xchg(&mnt->mnt_expiry_mark, 1))
			return -EAGAIN;
	}

	/*
	 * If we may have to abort operations to get out of this
	 * mount, and they will themselves hold resources we must
	 * allow the fs to do things. In the Unix tradition of
	 * 'Gee thats tricky lets do it in userspace' the umount_begin
	 * might fail to complete on the first run through as other tasks
	 * must return, and the like. Thats for the mount program to worry
	 * about for the moment.
	 */

	lock_kernel();
R
Ram Pai 已提交
541
	if ((flags & MNT_FORCE) && sb->s_op->umount_begin)
L
Linus Torvalds 已提交
542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569
		sb->s_op->umount_begin(sb);
	unlock_kernel();

	/*
	 * No sense to grab the lock for this test, but test itself looks
	 * somewhat bogus. Suggestions for better replacement?
	 * Ho-hum... In principle, we might treat that as umount + switch
	 * to rootfs. GC would eventually take care of the old vfsmount.
	 * Actually it makes sense, especially if rootfs would contain a
	 * /reboot - static binary that would close all descriptors and
	 * call reboot(9). Then init(8) could umount root and exec /reboot.
	 */
	if (mnt == current->fs->rootmnt && !(flags & MNT_DETACH)) {
		/*
		 * Special case for "unmounting" root ...
		 * we just try to remount it readonly.
		 */
		down_write(&sb->s_umount);
		if (!(sb->s_flags & MS_RDONLY)) {
			lock_kernel();
			DQUOT_OFF(sb);
			retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
			unlock_kernel();
		}
		up_write(&sb->s_umount);
		return retval;
	}

R
Ram Pai 已提交
570
	down_write(&namespace_sem);
L
Linus Torvalds 已提交
571
	spin_lock(&vfsmount_lock);
A
Al Viro 已提交
572
	event++;
L
Linus Torvalds 已提交
573 574

	retval = -EBUSY;
R
Ram Pai 已提交
575
	if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) {
L
Linus Torvalds 已提交
576
		if (!list_empty(&mnt->mnt_list))
R
Ram Pai 已提交
577
			umount_tree(mnt, 1, &umount_list);
L
Linus Torvalds 已提交
578 579 580 581 582
		retval = 0;
	}
	spin_unlock(&vfsmount_lock);
	if (retval)
		security_sb_umount_busy(mnt);
R
Ram Pai 已提交
583
	up_write(&namespace_sem);
R
Ram Pai 已提交
584
	release_mounts(&umount_list);
L
Linus Torvalds 已提交
585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623
	return retval;
}

/*
 * Now umount can handle mount points as well as block devices.
 * This is important for filesystems which use unnamed block devices.
 *
 * We now support a flag for forced unmount like the other 'big iron'
 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
 */

asmlinkage long sys_umount(char __user * name, int flags)
{
	struct nameidata nd;
	int retval;

	retval = __user_walk(name, LOOKUP_FOLLOW, &nd);
	if (retval)
		goto out;
	retval = -EINVAL;
	if (nd.dentry != nd.mnt->mnt_root)
		goto dput_and_out;
	if (!check_mnt(nd.mnt))
		goto dput_and_out;

	retval = -EPERM;
	if (!capable(CAP_SYS_ADMIN))
		goto dput_and_out;

	retval = do_umount(nd.mnt, flags);
dput_and_out:
	path_release_on_umount(&nd);
out:
	return retval;
}

#ifdef __ARCH_WANT_SYS_OLDUMOUNT

/*
R
Ram Pai 已提交
624
 *	The 2.0 compatible umount. No flags.
L
Linus Torvalds 已提交
625 626 627
 */
asmlinkage long sys_oldumount(char __user * name)
{
R
Ram Pai 已提交
628
	return sys_umount(name, 0);
L
Linus Torvalds 已提交
629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644
}

#endif

static int mount_is_safe(struct nameidata *nd)
{
	if (capable(CAP_SYS_ADMIN))
		return 0;
	return -EPERM;
#ifdef notyet
	if (S_ISLNK(nd->dentry->d_inode->i_mode))
		return -EPERM;
	if (nd->dentry->d_inode->i_mode & S_ISVTX) {
		if (current->uid != nd->dentry->d_inode->i_uid)
			return -EPERM;
	}
645
	if (vfs_permission(nd, MAY_WRITE))
L
Linus Torvalds 已提交
646 647 648 649 650
		return -EPERM;
	return 0;
#endif
}

R
Ram Pai 已提交
651
static int lives_below_in_same_fs(struct dentry *d, struct dentry *dentry)
L
Linus Torvalds 已提交
652 653 654 655 656 657 658 659 660 661
{
	while (1) {
		if (d == dentry)
			return 1;
		if (d == NULL || d == d->d_parent)
			return 0;
		d = d->d_parent;
	}
}

662
struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry,
R
Ram Pai 已提交
663
					int flag)
L
Linus Torvalds 已提交
664 665 666 667
{
	struct vfsmount *res, *p, *q, *r, *s;
	struct nameidata nd;

R
Ram Pai 已提交
668 669 670
	if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt))
		return NULL;

R
Ram Pai 已提交
671
	res = q = clone_mnt(mnt, dentry, flag);
L
Linus Torvalds 已提交
672 673 674 675 676
	if (!q)
		goto Enomem;
	q->mnt_mountpoint = mnt->mnt_mountpoint;

	p = mnt;
677
	list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
L
Linus Torvalds 已提交
678 679 680 681
		if (!lives_below_in_same_fs(r->mnt_mountpoint, dentry))
			continue;

		for (s = r; s; s = next_mnt(s, r)) {
R
Ram Pai 已提交
682 683 684 685
			if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) {
				s = skip_mnt_tree(s);
				continue;
			}
L
Linus Torvalds 已提交
686 687 688 689 690 691 692
			while (p != s->mnt_parent) {
				p = p->mnt_parent;
				q = q->mnt_parent;
			}
			p = s;
			nd.mnt = q;
			nd.dentry = p->mnt_mountpoint;
R
Ram Pai 已提交
693
			q = clone_mnt(p, p->mnt_root, flag);
L
Linus Torvalds 已提交
694 695 696 697 698 699 700 701 702
			if (!q)
				goto Enomem;
			spin_lock(&vfsmount_lock);
			list_add_tail(&q->mnt_list, &res->mnt_list);
			attach_mnt(q, &nd);
			spin_unlock(&vfsmount_lock);
		}
	}
	return res;
R
Ram Pai 已提交
703
Enomem:
L
Linus Torvalds 已提交
704
	if (res) {
R
Ram Pai 已提交
705
		LIST_HEAD(umount_list);
L
Linus Torvalds 已提交
706
		spin_lock(&vfsmount_lock);
R
Ram Pai 已提交
707
		umount_tree(res, 0, &umount_list);
L
Linus Torvalds 已提交
708
		spin_unlock(&vfsmount_lock);
R
Ram Pai 已提交
709
		release_mounts(&umount_list);
L
Linus Torvalds 已提交
710 711 712 713
	}
	return NULL;
}

714 715
/*
 *  @source_mnt : mount tree to be attached
R
Ram Pai 已提交
716 717 718 719
 *  @nd         : place the mount tree @source_mnt is attached
 *  @parent_nd  : if non-null, detach the source_mnt from its parent and
 *  		   store the parent mount and mountpoint dentry.
 *  		   (done when source_mnt is moved)
720 721 722
 *
 *  NOTE: in the table below explains the semantics when a source mount
 *  of a given type is attached to a destination mount of a given type.
R
Ram Pai 已提交
723 724 725 726 727 728 729 730 731 732 733 734
 * ---------------------------------------------------------------------------
 * |         BIND MOUNT OPERATION                                            |
 * |**************************************************************************
 * | source-->| shared        |       private  |       slave    | unbindable |
 * | dest     |               |                |                |            |
 * |   |      |               |                |                |            |
 * |   v      |               |                |                |            |
 * |**************************************************************************
 * |  shared  | shared (++)   |     shared (+) |     shared(+++)|  invalid   |
 * |          |               |                |                |            |
 * |non-shared| shared (+)    |      private   |      slave (*) |  invalid   |
 * ***************************************************************************
735 736 737 738 739 740 741 742 743
 * A bind operation clones the source mount and mounts the clone on the
 * destination mount.
 *
 * (++)  the cloned mount is propagated to all the mounts in the propagation
 * 	 tree of the destination mount and the cloned mount is added to
 * 	 the peer group of the source mount.
 * (+)   the cloned mount is created under the destination mount and is marked
 *       as shared. The cloned mount is added to the peer group of the source
 *       mount.
R
Ram Pai 已提交
744 745 746 747 748 749 750
 * (+++) the mount is propagated to all the mounts in the propagation tree
 *       of the destination mount and the cloned mount is made slave
 *       of the same master as that of the source mount. The cloned mount
 *       is marked as 'shared and slave'.
 * (*)   the cloned mount is made a slave of the same master as that of the
 * 	 source mount.
 *
R
Ram Pai 已提交
751 752 753 754 755 756 757 758 759 760 761 762
 * ---------------------------------------------------------------------------
 * |         		MOVE MOUNT OPERATION                                 |
 * |**************************************************************************
 * | source-->| shared        |       private  |       slave    | unbindable |
 * | dest     |               |                |                |            |
 * |   |      |               |                |                |            |
 * |   v      |               |                |                |            |
 * |**************************************************************************
 * |  shared  | shared (+)    |     shared (+) |    shared(+++) |  invalid   |
 * |          |               |                |                |            |
 * |non-shared| shared (+*)   |      private   |    slave (*)   | unbindable |
 * ***************************************************************************
R
Ram Pai 已提交
763 764 765
 *
 * (+)  the mount is moved to the destination. And is then propagated to
 * 	all the mounts in the propagation tree of the destination mount.
R
Ram Pai 已提交
766
 * (+*)  the mount is moved to the destination.
R
Ram Pai 已提交
767 768 769 770
 * (+++)  the mount is moved to the destination and is then propagated to
 * 	all the mounts belonging to the destination mount's propagation tree.
 * 	the mount is marked as 'shared and slave'.
 * (*)	the mount continues to be a slave at the new location.
771 772 773 774 775 776 777
 *
 * if the source mount is a tree, the operations explained above is
 * applied to each mount in the tree.
 * Must be called without spinlocks held, since this function can sleep
 * in allocations.
 */
static int attach_recursive_mnt(struct vfsmount *source_mnt,
R
Ram Pai 已提交
778
			struct nameidata *nd, struct nameidata *parent_nd)
779 780 781 782 783 784 785 786 787 788 789 790 791 792 793
{
	LIST_HEAD(tree_list);
	struct vfsmount *dest_mnt = nd->mnt;
	struct dentry *dest_dentry = nd->dentry;
	struct vfsmount *child, *p;

	if (propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list))
		return -EINVAL;

	if (IS_MNT_SHARED(dest_mnt)) {
		for (p = source_mnt; p; p = next_mnt(p, source_mnt))
			set_mnt_shared(p);
	}

	spin_lock(&vfsmount_lock);
R
Ram Pai 已提交
794 795 796 797 798 799 800 801
	if (parent_nd) {
		detach_mnt(source_mnt, parent_nd);
		attach_mnt(source_mnt, nd);
		touch_namespace(current->namespace);
	} else {
		mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt);
		commit_tree(source_mnt);
	}
802 803 804 805 806 807 808 809 810

	list_for_each_entry_safe(child, p, &tree_list, mnt_hash) {
		list_del_init(&child->mnt_hash);
		commit_tree(child);
	}
	spin_unlock(&vfsmount_lock);
	return 0;
}

L
Linus Torvalds 已提交
811 812 813 814 815 816 817 818 819 820 821
static int graft_tree(struct vfsmount *mnt, struct nameidata *nd)
{
	int err;
	if (mnt->mnt_sb->s_flags & MS_NOUSER)
		return -EINVAL;

	if (S_ISDIR(nd->dentry->d_inode->i_mode) !=
	      S_ISDIR(mnt->mnt_root->d_inode->i_mode))
		return -ENOTDIR;

	err = -ENOENT;
822
	mutex_lock(&nd->dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
823 824 825 826 827 828 829 830
	if (IS_DEADDIR(nd->dentry->d_inode))
		goto out_unlock;

	err = security_sb_check_sb(mnt, nd);
	if (err)
		goto out_unlock;

	err = -ENOENT;
831
	if (IS_ROOT(nd->dentry) || !d_unhashed(nd->dentry))
R
Ram Pai 已提交
832
		err = attach_recursive_mnt(mnt, nd, NULL);
L
Linus Torvalds 已提交
833
out_unlock:
834
	mutex_unlock(&nd->dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
835 836 837 838 839
	if (!err)
		security_sb_post_addmount(mnt, nd);
	return err;
}

840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860
/*
 * recursively change the type of the mountpoint.
 */
static int do_change_type(struct nameidata *nd, int flag)
{
	struct vfsmount *m, *mnt = nd->mnt;
	int recurse = flag & MS_REC;
	int type = flag & ~MS_REC;

	if (nd->dentry != nd->mnt->mnt_root)
		return -EINVAL;

	down_write(&namespace_sem);
	spin_lock(&vfsmount_lock);
	for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
		change_mnt_propagation(m, type);
	spin_unlock(&vfsmount_lock);
	up_write(&namespace_sem);
	return 0;
}

L
Linus Torvalds 已提交
861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876
/*
 * do loopback mount.
 */
static int do_loopback(struct nameidata *nd, char *old_name, int recurse)
{
	struct nameidata old_nd;
	struct vfsmount *mnt = NULL;
	int err = mount_is_safe(nd);
	if (err)
		return err;
	if (!old_name || !*old_name)
		return -EINVAL;
	err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd);
	if (err)
		return err;

R
Ram Pai 已提交
877
	down_write(&namespace_sem);
L
Linus Torvalds 已提交
878
	err = -EINVAL;
R
Ram Pai 已提交
879 880 881
	if (IS_MNT_UNBINDABLE(old_nd.mnt))
 		goto out;

882 883
	if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt))
		goto out;
L
Linus Torvalds 已提交
884

885 886
	err = -ENOMEM;
	if (recurse)
R
Ram Pai 已提交
887
		mnt = copy_tree(old_nd.mnt, old_nd.dentry, 0);
888
	else
R
Ram Pai 已提交
889
		mnt = clone_mnt(old_nd.mnt, old_nd.dentry, 0);
890 891 892 893 894 895

	if (!mnt)
		goto out;

	err = graft_tree(mnt, nd);
	if (err) {
R
Ram Pai 已提交
896
		LIST_HEAD(umount_list);
L
Linus Torvalds 已提交
897
		spin_lock(&vfsmount_lock);
R
Ram Pai 已提交
898
		umount_tree(mnt, 0, &umount_list);
L
Linus Torvalds 已提交
899
		spin_unlock(&vfsmount_lock);
R
Ram Pai 已提交
900
		release_mounts(&umount_list);
901
	}
L
Linus Torvalds 已提交
902

903
out:
R
Ram Pai 已提交
904
	up_write(&namespace_sem);
L
Linus Torvalds 已提交
905 906 907 908 909 910 911 912 913 914 915 916 917
	path_release(&old_nd);
	return err;
}

/*
 * change filesystem flags. dir should be a physical root of filesystem.
 * If you've mounted a non-root directory somewhere and want to do remount
 * on it - tough luck.
 */
static int do_remount(struct nameidata *nd, int flags, int mnt_flags,
		      void *data)
{
	int err;
R
Ram Pai 已提交
918
	struct super_block *sb = nd->mnt->mnt_sb;
L
Linus Torvalds 已提交
919 920 921 922 923 924 925 926 927 928 929 930 931

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	if (!check_mnt(nd->mnt))
		return -EINVAL;

	if (nd->dentry != nd->mnt->mnt_root)
		return -EINVAL;

	down_write(&sb->s_umount);
	err = do_remount_sb(sb, flags, data, 0);
	if (!err)
R
Ram Pai 已提交
932
		nd->mnt->mnt_flags = mnt_flags;
L
Linus Torvalds 已提交
933 934 935 936 937 938
	up_write(&sb->s_umount);
	if (!err)
		security_sb_post_remount(nd->mnt, flags, data);
	return err;
}

R
Ram Pai 已提交
939 940 941 942 943 944 945 946 947 948
static inline int tree_contains_unbindable(struct vfsmount *mnt)
{
	struct vfsmount *p;
	for (p = mnt; p; p = next_mnt(p, mnt)) {
		if (IS_MNT_UNBINDABLE(p))
			return 1;
	}
	return 0;
}

L
Linus Torvalds 已提交
949 950 951 952 953 954 955 956 957 958 959 960 961
static int do_move_mount(struct nameidata *nd, char *old_name)
{
	struct nameidata old_nd, parent_nd;
	struct vfsmount *p;
	int err = 0;
	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;
	if (!old_name || !*old_name)
		return -EINVAL;
	err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd);
	if (err)
		return err;

R
Ram Pai 已提交
962
	down_write(&namespace_sem);
R
Ram Pai 已提交
963
	while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
L
Linus Torvalds 已提交
964 965 966 967 968 969
		;
	err = -EINVAL;
	if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt))
		goto out;

	err = -ENOENT;
970
	mutex_lock(&nd->dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
971 972 973 974
	if (IS_DEADDIR(nd->dentry->d_inode))
		goto out1;

	if (!IS_ROOT(nd->dentry) && d_unhashed(nd->dentry))
R
Ram Pai 已提交
975
		goto out1;
L
Linus Torvalds 已提交
976 977 978

	err = -EINVAL;
	if (old_nd.dentry != old_nd.mnt->mnt_root)
R
Ram Pai 已提交
979
		goto out1;
L
Linus Torvalds 已提交
980 981

	if (old_nd.mnt == old_nd.mnt->mnt_parent)
R
Ram Pai 已提交
982
		goto out1;
L
Linus Torvalds 已提交
983 984 985

	if (S_ISDIR(nd->dentry->d_inode->i_mode) !=
	      S_ISDIR(old_nd.dentry->d_inode->i_mode))
R
Ram Pai 已提交
986 987 988 989 990 991
		goto out1;
	/*
	 * Don't move a mount residing in a shared parent.
	 */
	if (old_nd.mnt->mnt_parent && IS_MNT_SHARED(old_nd.mnt->mnt_parent))
		goto out1;
R
Ram Pai 已提交
992 993 994 995 996 997
	/*
	 * Don't move a mount tree containing unbindable mounts to a destination
	 * mount which is shared.
	 */
	if (IS_MNT_SHARED(nd->mnt) && tree_contains_unbindable(old_nd.mnt))
		goto out1;
L
Linus Torvalds 已提交
998
	err = -ELOOP;
R
Ram Pai 已提交
999
	for (p = nd->mnt; p->mnt_parent != p; p = p->mnt_parent)
L
Linus Torvalds 已提交
1000
		if (p == old_nd.mnt)
R
Ram Pai 已提交
1001
			goto out1;
L
Linus Torvalds 已提交
1002

R
Ram Pai 已提交
1003 1004
	if ((err = attach_recursive_mnt(old_nd.mnt, nd, &parent_nd)))
		goto out1;
L
Linus Torvalds 已提交
1005

R
Ram Pai 已提交
1006
	spin_lock(&vfsmount_lock);
L
Linus Torvalds 已提交
1007 1008
	/* if the mount is moved, it should no longer be expire
	 * automatically */
1009
	list_del_init(&old_nd.mnt->mnt_expire);
L
Linus Torvalds 已提交
1010 1011
	spin_unlock(&vfsmount_lock);
out1:
1012
	mutex_unlock(&nd->dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
1013
out:
R
Ram Pai 已提交
1014
	up_write(&namespace_sem);
L
Linus Torvalds 已提交
1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052
	if (!err)
		path_release(&parent_nd);
	path_release(&old_nd);
	return err;
}

/*
 * create a new mount for userspace and request it to be added into the
 * namespace's tree
 */
static int do_new_mount(struct nameidata *nd, char *type, int flags,
			int mnt_flags, char *name, void *data)
{
	struct vfsmount *mnt;

	if (!type || !memchr(type, 0, PAGE_SIZE))
		return -EINVAL;

	/* we need capabilities... */
	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	mnt = do_kern_mount(type, flags, name, data);
	if (IS_ERR(mnt))
		return PTR_ERR(mnt);

	return do_add_mount(mnt, nd, mnt_flags, NULL);
}

/*
 * add a mount into a namespace's mount tree
 * - provide the option of adding the new mount to an expiration list
 */
int do_add_mount(struct vfsmount *newmnt, struct nameidata *nd,
		 int mnt_flags, struct list_head *fslist)
{
	int err;

R
Ram Pai 已提交
1053
	down_write(&namespace_sem);
L
Linus Torvalds 已提交
1054
	/* Something was mounted here while we slept */
R
Ram Pai 已提交
1055
	while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
L
Linus Torvalds 已提交
1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071
		;
	err = -EINVAL;
	if (!check_mnt(nd->mnt))
		goto unlock;

	/* Refuse the same filesystem on the same mount point */
	err = -EBUSY;
	if (nd->mnt->mnt_sb == newmnt->mnt_sb &&
	    nd->mnt->mnt_root == nd->dentry)
		goto unlock;

	err = -EINVAL;
	if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode))
		goto unlock;

	newmnt->mnt_flags = mnt_flags;
1072 1073
	if ((err = graft_tree(newmnt, nd)))
		goto unlock;
L
Linus Torvalds 已提交
1074

1075
	if (fslist) {
L
Linus Torvalds 已提交
1076 1077
		/* add to the specified expiration list */
		spin_lock(&vfsmount_lock);
1078
		list_add_tail(&newmnt->mnt_expire, fslist);
L
Linus Torvalds 已提交
1079 1080
		spin_unlock(&vfsmount_lock);
	}
R
Ram Pai 已提交
1081
	up_write(&namespace_sem);
1082
	return 0;
L
Linus Torvalds 已提交
1083 1084

unlock:
R
Ram Pai 已提交
1085
	up_write(&namespace_sem);
L
Linus Torvalds 已提交
1086 1087 1088 1089 1090 1091
	mntput(newmnt);
	return err;
}

EXPORT_SYMBOL_GPL(do_add_mount);

R
Ram Pai 已提交
1092 1093
static void expire_mount(struct vfsmount *mnt, struct list_head *mounts,
				struct list_head *umounts)
1094 1095 1096
{
	spin_lock(&vfsmount_lock);

1097 1098 1099 1100 1101 1102 1103 1104 1105
	/*
	 * Check if mount is still attached, if not, let whoever holds it deal
	 * with the sucker
	 */
	if (mnt->mnt_parent == mnt) {
		spin_unlock(&vfsmount_lock);
		return;
	}

1106 1107 1108 1109
	/*
	 * Check that it is still dead: the count should now be 2 - as
	 * contributed by the vfsmount parent and the mntget above
	 */
R
Ram Pai 已提交
1110
	if (!propagate_mount_busy(mnt, 2)) {
1111
		/* delete from the namespace */
A
Al Viro 已提交
1112
		touch_namespace(mnt->mnt_namespace);
1113
		list_del_init(&mnt->mnt_list);
1114
		mnt->mnt_namespace = NULL;
R
Ram Pai 已提交
1115
		umount_tree(mnt, 1, umounts);
1116 1117 1118 1119 1120 1121
		spin_unlock(&vfsmount_lock);
	} else {
		/*
		 * Someone brought it back to life whilst we didn't have any
		 * locks held so return it to the expiration list
		 */
1122
		list_add_tail(&mnt->mnt_expire, mounts);
1123 1124 1125 1126
		spin_unlock(&vfsmount_lock);
	}
}

L
Linus Torvalds 已提交
1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148
/*
 * process a list of expirable mountpoints with the intent of discarding any
 * mountpoints that aren't in use and haven't been touched since last we came
 * here
 */
void mark_mounts_for_expiry(struct list_head *mounts)
{
	struct namespace *namespace;
	struct vfsmount *mnt, *next;
	LIST_HEAD(graveyard);

	if (list_empty(mounts))
		return;

	spin_lock(&vfsmount_lock);

	/* extract from the expiration list every vfsmount that matches the
	 * following criteria:
	 * - only referenced by its parent vfsmount
	 * - still marked for expiry (marked on the last call here; marks are
	 *   cleared by mntput())
	 */
1149
	list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
L
Linus Torvalds 已提交
1150 1151 1152 1153 1154
		if (!xchg(&mnt->mnt_expiry_mark, 1) ||
		    atomic_read(&mnt->mnt_count) != 1)
			continue;

		mntget(mnt);
1155
		list_move(&mnt->mnt_expire, &graveyard);
L
Linus Torvalds 已提交
1156 1157 1158 1159 1160 1161 1162 1163 1164
	}

	/*
	 * go through the vfsmounts we've just consigned to the graveyard to
	 * - check that they're still dead
	 * - delete the vfsmount from the appropriate namespace under lock
	 * - dispose of the corpse
	 */
	while (!list_empty(&graveyard)) {
R
Ram Pai 已提交
1165
		LIST_HEAD(umounts);
1166 1167
		mnt = list_entry(graveyard.next, struct vfsmount, mnt_expire);
		list_del_init(&mnt->mnt_expire);
L
Linus Torvalds 已提交
1168 1169 1170 1171

		/* don't do anything if the namespace is dead - all the
		 * vfsmounts from it are going away anyway */
		namespace = mnt->mnt_namespace;
1172
		if (!namespace || !namespace->root)
L
Linus Torvalds 已提交
1173 1174 1175 1176
			continue;
		get_namespace(namespace);

		spin_unlock(&vfsmount_lock);
R
Ram Pai 已提交
1177
		down_write(&namespace_sem);
R
Ram Pai 已提交
1178
		expire_mount(mnt, mounts, &umounts);
R
Ram Pai 已提交
1179
		up_write(&namespace_sem);
R
Ram Pai 已提交
1180
		release_mounts(&umounts);
L
Linus Torvalds 已提交
1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196
		mntput(mnt);
		put_namespace(namespace);
		spin_lock(&vfsmount_lock);
	}

	spin_unlock(&vfsmount_lock);
}

EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);

/*
 * Some copy_from_user() implementations do not return the exact number of
 * bytes remaining to copy on a fault.  But copy_mount_options() requires that.
 * Note that this function differs from copy_from_user() in that it will oops
 * on bad values of `to', rather than returning a short copy.
 */
R
Ram Pai 已提交
1197 1198
static long exact_copy_from_user(void *to, const void __user * from,
				 unsigned long n)
L
Linus Torvalds 已提交
1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218
{
	char *t = to;
	const char __user *f = from;
	char c;

	if (!access_ok(VERIFY_READ, from, n))
		return n;

	while (n) {
		if (__get_user(c, f)) {
			memset(t, 0, n);
			break;
		}
		*t++ = c;
		f++;
		n--;
	}
	return n;
}

R
Ram Pai 已提交
1219
int copy_mount_options(const void __user * data, unsigned long *where)
L
Linus Torvalds 已提交
1220 1221 1222 1223
{
	int i;
	unsigned long page;
	unsigned long size;
R
Ram Pai 已提交
1224

L
Linus Torvalds 已提交
1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242
	*where = 0;
	if (!data)
		return 0;

	if (!(page = __get_free_page(GFP_KERNEL)))
		return -ENOMEM;

	/* We only care that *some* data at the address the user
	 * gave us is valid.  Just in case, we'll zero
	 * the remainder of the page.
	 */
	/* copy_from_user cannot cross TASK_SIZE ! */
	size = TASK_SIZE - (unsigned long)data;
	if (size > PAGE_SIZE)
		size = PAGE_SIZE;

	i = size - exact_copy_from_user((void *)page, data, size);
	if (!i) {
R
Ram Pai 已提交
1243
		free_page(page);
L
Linus Torvalds 已提交
1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265
		return -EFAULT;
	}
	if (i != PAGE_SIZE)
		memset((char *)page + i, 0, PAGE_SIZE - i);
	*where = page;
	return 0;
}

/*
 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
 *
 * data is a (void *) that can point to any structure up to
 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
 * information (or be NULL).
 *
 * Pre-0.97 versions of mount() didn't have a flags word.
 * When the flags word was introduced its top half was required
 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
 * Therefore, if this magic number is present, it carries no information
 * and must be discarded.
 */
R
Ram Pai 已提交
1266
long do_mount(char *dev_name, char *dir_name, char *type_page,
L
Linus Torvalds 已提交
1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293
		  unsigned long flags, void *data_page)
{
	struct nameidata nd;
	int retval = 0;
	int mnt_flags = 0;

	/* Discard magic */
	if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
		flags &= ~MS_MGC_MSK;

	/* Basic sanity checks */

	if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE))
		return -EINVAL;
	if (dev_name && !memchr(dev_name, 0, PAGE_SIZE))
		return -EINVAL;

	if (data_page)
		((char *)data_page)[PAGE_SIZE - 1] = 0;

	/* Separate the per-mountpoint flags */
	if (flags & MS_NOSUID)
		mnt_flags |= MNT_NOSUID;
	if (flags & MS_NODEV)
		mnt_flags |= MNT_NODEV;
	if (flags & MS_NOEXEC)
		mnt_flags |= MNT_NOEXEC;
1294 1295 1296 1297 1298 1299 1300
	if (flags & MS_NOATIME)
		mnt_flags |= MNT_NOATIME;
	if (flags & MS_NODIRATIME)
		mnt_flags |= MNT_NODIRATIME;

	flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE |
		   MS_NOATIME | MS_NODIRATIME);
L
Linus Torvalds 已提交
1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315

	/* ... and get the mountpoint */
	retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd);
	if (retval)
		return retval;

	retval = security_sb_mount(dev_name, &nd, type_page, flags, data_page);
	if (retval)
		goto dput_out;

	if (flags & MS_REMOUNT)
		retval = do_remount(&nd, flags & ~MS_REMOUNT, mnt_flags,
				    data_page);
	else if (flags & MS_BIND)
		retval = do_loopback(&nd, dev_name, flags & MS_REC);
R
Ram Pai 已提交
1316
	else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
1317
		retval = do_change_type(&nd, flags);
L
Linus Torvalds 已提交
1318 1319 1320 1321 1322 1323 1324 1325 1326 1327
	else if (flags & MS_MOVE)
		retval = do_move_mount(&nd, dev_name);
	else
		retval = do_new_mount(&nd, type_page, flags, mnt_flags,
				      dev_name, data_page);
dput_out:
	path_release(&nd);
	return retval;
}

1328 1329 1330 1331 1332
/*
 * Allocate a new namespace structure and populate it with contents
 * copied from the namespace of the passed in task structure.
 */
struct namespace *dup_namespace(struct task_struct *tsk, struct fs_struct *fs)
L
Linus Torvalds 已提交
1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344
{
	struct namespace *namespace = tsk->namespace;
	struct namespace *new_ns;
	struct vfsmount *rootmnt = NULL, *pwdmnt = NULL, *altrootmnt = NULL;
	struct vfsmount *p, *q;

	new_ns = kmalloc(sizeof(struct namespace), GFP_KERNEL);
	if (!new_ns)
		goto out;

	atomic_set(&new_ns->count, 1);
	INIT_LIST_HEAD(&new_ns->list);
A
Al Viro 已提交
1345 1346
	init_waitqueue_head(&new_ns->poll);
	new_ns->event = 0;
L
Linus Torvalds 已提交
1347

R
Ram Pai 已提交
1348
	down_write(&namespace_sem);
L
Linus Torvalds 已提交
1349
	/* First pass: copy the tree topology */
R
Ram Pai 已提交
1350
	new_ns->root = copy_tree(namespace->root, namespace->root->mnt_root,
R
Ram Pai 已提交
1351
					CL_COPY_ALL | CL_EXPIRE);
L
Linus Torvalds 已提交
1352
	if (!new_ns->root) {
R
Ram Pai 已提交
1353
		up_write(&namespace_sem);
L
Linus Torvalds 已提交
1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386
		kfree(new_ns);
		goto out;
	}
	spin_lock(&vfsmount_lock);
	list_add_tail(&new_ns->list, &new_ns->root->mnt_list);
	spin_unlock(&vfsmount_lock);

	/*
	 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
	 * as belonging to new namespace.  We have already acquired a private
	 * fs_struct, so tsk->fs->lock is not needed.
	 */
	p = namespace->root;
	q = new_ns->root;
	while (p) {
		q->mnt_namespace = new_ns;
		if (fs) {
			if (p == fs->rootmnt) {
				rootmnt = p;
				fs->rootmnt = mntget(q);
			}
			if (p == fs->pwdmnt) {
				pwdmnt = p;
				fs->pwdmnt = mntget(q);
			}
			if (p == fs->altrootmnt) {
				altrootmnt = p;
				fs->altrootmnt = mntget(q);
			}
		}
		p = next_mnt(p, namespace->root);
		q = next_mnt(q, new_ns->root);
	}
R
Ram Pai 已提交
1387
	up_write(&namespace_sem);
L
Linus Torvalds 已提交
1388 1389 1390 1391 1392 1393 1394 1395

	if (rootmnt)
		mntput(rootmnt);
	if (pwdmnt)
		mntput(pwdmnt);
	if (altrootmnt)
		mntput(altrootmnt);

1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425
out:
	return new_ns;
}

int copy_namespace(int flags, struct task_struct *tsk)
{
	struct namespace *namespace = tsk->namespace;
	struct namespace *new_ns;
	int err = 0;

	if (!namespace)
		return 0;

	get_namespace(namespace);

	if (!(flags & CLONE_NEWNS))
		return 0;

	if (!capable(CAP_SYS_ADMIN)) {
		err = -EPERM;
		goto out;
	}

	new_ns = dup_namespace(tsk, tsk->fs);
	if (!new_ns) {
		err = -ENOMEM;
		goto out;
	}

	tsk->namespace = new_ns;
L
Linus Torvalds 已提交
1426 1427 1428

out:
	put_namespace(namespace);
1429
	return err;
L
Linus Torvalds 已提交
1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441
}

asmlinkage long sys_mount(char __user * dev_name, char __user * dir_name,
			  char __user * type, unsigned long flags,
			  void __user * data)
{
	int retval;
	unsigned long data_page;
	unsigned long type_page;
	unsigned long dev_page;
	char *dir_page;

R
Ram Pai 已提交
1442
	retval = copy_mount_options(type, &type_page);
L
Linus Torvalds 已提交
1443 1444 1445 1446 1447 1448 1449 1450
	if (retval < 0)
		return retval;

	dir_page = getname(dir_name);
	retval = PTR_ERR(dir_page);
	if (IS_ERR(dir_page))
		goto out1;

R
Ram Pai 已提交
1451
	retval = copy_mount_options(dev_name, &dev_page);
L
Linus Torvalds 已提交
1452 1453 1454
	if (retval < 0)
		goto out2;

R
Ram Pai 已提交
1455
	retval = copy_mount_options(data, &data_page);
L
Linus Torvalds 已提交
1456 1457 1458 1459
	if (retval < 0)
		goto out3;

	lock_kernel();
R
Ram Pai 已提交
1460 1461
	retval = do_mount((char *)dev_page, dir_page, (char *)type_page,
			  flags, (void *)data_page);
L
Linus Torvalds 已提交
1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529
	unlock_kernel();
	free_page(data_page);

out3:
	free_page(dev_page);
out2:
	putname(dir_page);
out1:
	free_page(type_page);
	return retval;
}

/*
 * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
 * It can block. Requires the big lock held.
 */
void set_fs_root(struct fs_struct *fs, struct vfsmount *mnt,
		 struct dentry *dentry)
{
	struct dentry *old_root;
	struct vfsmount *old_rootmnt;
	write_lock(&fs->lock);
	old_root = fs->root;
	old_rootmnt = fs->rootmnt;
	fs->rootmnt = mntget(mnt);
	fs->root = dget(dentry);
	write_unlock(&fs->lock);
	if (old_root) {
		dput(old_root);
		mntput(old_rootmnt);
	}
}

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

	write_lock(&fs->lock);
	old_pwd = fs->pwd;
	old_pwdmnt = fs->pwdmnt;
	fs->pwdmnt = mntget(mnt);
	fs->pwd = dget(dentry);
	write_unlock(&fs->lock);

	if (old_pwd) {
		dput(old_pwd);
		mntput(old_pwdmnt);
	}
}

static void chroot_fs_refs(struct nameidata *old_nd, struct nameidata *new_nd)
{
	struct task_struct *g, *p;
	struct fs_struct *fs;

	read_lock(&tasklist_lock);
	do_each_thread(g, p) {
		task_lock(p);
		fs = p->fs;
		if (fs) {
			atomic_inc(&fs->count);
			task_unlock(p);
R
Ram Pai 已提交
1530 1531
			if (fs->root == old_nd->dentry
			    && fs->rootmnt == old_nd->mnt)
L
Linus Torvalds 已提交
1532
				set_fs_root(fs, new_nd->mnt, new_nd->dentry);
R
Ram Pai 已提交
1533 1534
			if (fs->pwd == old_nd->dentry
			    && fs->pwdmnt == old_nd->mnt)
L
Linus Torvalds 已提交
1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555
				set_fs_pwd(fs, new_nd->mnt, new_nd->dentry);
			put_fs_struct(fs);
		} else
			task_unlock(p);
	} while_each_thread(g, p);
	read_unlock(&tasklist_lock);
}

/*
 * pivot_root Semantics:
 * Moves the root file system of the current process to the directory put_old,
 * makes new_root as the new root file system of the current process, and sets
 * root/cwd of all processes which had them on the current root to new_root.
 *
 * Restrictions:
 * The new_root and put_old must be directories, and  must not be on the
 * same file  system as the current process root. The put_old  must  be
 * underneath new_root,  i.e. adding a non-zero number of /.. to the string
 * pointed to by put_old must yield the same directory as new_root. No other
 * file system may be mounted on put_old. After all, new_root is a mountpoint.
 *
N
Neil Brown 已提交
1556 1557 1558 1559
 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
 * in this situation.
 *
L
Linus Torvalds 已提交
1560 1561 1562 1563 1564 1565 1566 1567
 * Notes:
 *  - we don't move root/cwd if they are not at the root (reason: if something
 *    cared enough to change them, it's probably wrong to force them elsewhere)
 *  - it's okay to pick a root that isn't the root of a file system, e.g.
 *    /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
 *    though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
 *    first.
 */
R
Ram Pai 已提交
1568 1569
asmlinkage long sys_pivot_root(const char __user * new_root,
			       const char __user * put_old)
L
Linus Torvalds 已提交
1570 1571 1572 1573 1574 1575 1576 1577 1578 1579
{
	struct vfsmount *tmp;
	struct nameidata new_nd, old_nd, parent_nd, root_parent, user_nd;
	int error;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	lock_kernel();

R
Ram Pai 已提交
1580 1581
	error = __user_walk(new_root, LOOKUP_FOLLOW | LOOKUP_DIRECTORY,
			    &new_nd);
L
Linus Torvalds 已提交
1582 1583 1584 1585 1586 1587
	if (error)
		goto out0;
	error = -EINVAL;
	if (!check_mnt(new_nd.mnt))
		goto out1;

R
Ram Pai 已提交
1588
	error = __user_walk(put_old, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old_nd);
L
Linus Torvalds 已提交
1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601
	if (error)
		goto out1;

	error = security_sb_pivotroot(&old_nd, &new_nd);
	if (error) {
		path_release(&old_nd);
		goto out1;
	}

	read_lock(&current->fs->lock);
	user_nd.mnt = mntget(current->fs->rootmnt);
	user_nd.dentry = dget(current->fs->root);
	read_unlock(&current->fs->lock);
R
Ram Pai 已提交
1602
	down_write(&namespace_sem);
1603
	mutex_lock(&old_nd.dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
1604
	error = -EINVAL;
R
Ram Pai 已提交
1605 1606 1607 1608
	if (IS_MNT_SHARED(old_nd.mnt) ||
		IS_MNT_SHARED(new_nd.mnt->mnt_parent) ||
		IS_MNT_SHARED(user_nd.mnt->mnt_parent))
		goto out2;
L
Linus Torvalds 已提交
1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623
	if (!check_mnt(user_nd.mnt))
		goto out2;
	error = -ENOENT;
	if (IS_DEADDIR(new_nd.dentry->d_inode))
		goto out2;
	if (d_unhashed(new_nd.dentry) && !IS_ROOT(new_nd.dentry))
		goto out2;
	if (d_unhashed(old_nd.dentry) && !IS_ROOT(old_nd.dentry))
		goto out2;
	error = -EBUSY;
	if (new_nd.mnt == user_nd.mnt || old_nd.mnt == user_nd.mnt)
		goto out2; /* loop, on the same file system  */
	error = -EINVAL;
	if (user_nd.mnt->mnt_root != user_nd.dentry)
		goto out2; /* not a mountpoint */
1624 1625
	if (user_nd.mnt->mnt_parent == user_nd.mnt)
		goto out2; /* not attached */
L
Linus Torvalds 已提交
1626 1627
	if (new_nd.mnt->mnt_root != new_nd.dentry)
		goto out2; /* not a mountpoint */
1628 1629
	if (new_nd.mnt->mnt_parent == new_nd.mnt)
		goto out2; /* not attached */
L
Linus Torvalds 已提交
1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647
	tmp = old_nd.mnt; /* make sure we can reach put_old from new_root */
	spin_lock(&vfsmount_lock);
	if (tmp != new_nd.mnt) {
		for (;;) {
			if (tmp->mnt_parent == tmp)
				goto out3; /* already mounted on put_old */
			if (tmp->mnt_parent == new_nd.mnt)
				break;
			tmp = tmp->mnt_parent;
		}
		if (!is_subdir(tmp->mnt_mountpoint, new_nd.dentry))
			goto out3;
	} else if (!is_subdir(old_nd.dentry, new_nd.dentry))
		goto out3;
	detach_mnt(new_nd.mnt, &parent_nd);
	detach_mnt(user_nd.mnt, &root_parent);
	attach_mnt(user_nd.mnt, &old_nd);     /* mount old root on put_old */
	attach_mnt(new_nd.mnt, &root_parent); /* mount new_root on / */
A
Al Viro 已提交
1648
	touch_namespace(current->namespace);
L
Linus Torvalds 已提交
1649 1650 1651 1652 1653 1654 1655
	spin_unlock(&vfsmount_lock);
	chroot_fs_refs(&user_nd, &new_nd);
	security_sb_post_pivotroot(&user_nd, &new_nd);
	error = 0;
	path_release(&root_parent);
	path_release(&parent_nd);
out2:
1656
	mutex_unlock(&old_nd.dentry->d_inode->i_mutex);
R
Ram Pai 已提交
1657
	up_write(&namespace_sem);
L
Linus Torvalds 已提交
1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683
	path_release(&user_nd);
	path_release(&old_nd);
out1:
	path_release(&new_nd);
out0:
	unlock_kernel();
	return error;
out3:
	spin_unlock(&vfsmount_lock);
	goto out2;
}

static void __init init_mount_tree(void)
{
	struct vfsmount *mnt;
	struct namespace *namespace;
	struct task_struct *g, *p;

	mnt = do_kern_mount("rootfs", 0, "rootfs", NULL);
	if (IS_ERR(mnt))
		panic("Can't create rootfs");
	namespace = kmalloc(sizeof(*namespace), GFP_KERNEL);
	if (!namespace)
		panic("Can't allocate initial namespace");
	atomic_set(&namespace->count, 1);
	INIT_LIST_HEAD(&namespace->list);
A
Al Viro 已提交
1684 1685
	init_waitqueue_head(&namespace->poll);
	namespace->event = 0;
L
Linus Torvalds 已提交
1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707
	list_add(&mnt->mnt_list, &namespace->list);
	namespace->root = mnt;
	mnt->mnt_namespace = namespace;

	init_task.namespace = namespace;
	read_lock(&tasklist_lock);
	do_each_thread(g, p) {
		get_namespace(namespace);
		p->namespace = namespace;
	} while_each_thread(g, p);
	read_unlock(&tasklist_lock);

	set_fs_pwd(current->fs, namespace->root, namespace->root->mnt_root);
	set_fs_root(current->fs, namespace->root, namespace->root->mnt_root);
}

void __init mnt_init(unsigned long mempages)
{
	struct list_head *d;
	unsigned int nr_hash;
	int i;

R
Ram Pai 已提交
1708 1709
	init_rwsem(&namespace_sem);

L
Linus Torvalds 已提交
1710
	mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount),
R
Ram Pai 已提交
1711
			0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL, NULL);
L
Linus Torvalds 已提交
1712

R
Ram Pai 已提交
1713
	mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);
L
Linus Torvalds 已提交
1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734

	if (!mount_hashtable)
		panic("Failed to allocate mount hash table\n");

	/*
	 * Find the power-of-two list-heads that can fit into the allocation..
	 * We don't guarantee that "sizeof(struct list_head)" is necessarily
	 * a power-of-two.
	 */
	nr_hash = PAGE_SIZE / sizeof(struct list_head);
	hash_bits = 0;
	do {
		hash_bits++;
	} while ((nr_hash >> hash_bits) != 0);
	hash_bits--;

	/*
	 * Re-calculate the actual number of entries and the mask
	 * from the number of bits we can fit.
	 */
	nr_hash = 1UL << hash_bits;
R
Ram Pai 已提交
1735
	hash_mask = nr_hash - 1;
L
Linus Torvalds 已提交
1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747

	printk("Mount-cache hash table entries: %d\n", nr_hash);

	/* And initialize the newly allocated array */
	d = mount_hashtable;
	i = nr_hash;
	do {
		INIT_LIST_HEAD(d);
		d++;
		i--;
	} while (i);
	sysfs_init();
M
Miklos Szeredi 已提交
1748
	subsystem_register(&fs_subsys);
L
Linus Torvalds 已提交
1749 1750 1751 1752 1753 1754
	init_rootfs();
	init_mount_tree();
}

void __put_namespace(struct namespace *namespace)
{
1755
	struct vfsmount *root = namespace->root;
R
Ram Pai 已提交
1756
	LIST_HEAD(umount_list);
1757 1758
	namespace->root = NULL;
	spin_unlock(&vfsmount_lock);
R
Ram Pai 已提交
1759
	down_write(&namespace_sem);
L
Linus Torvalds 已提交
1760
	spin_lock(&vfsmount_lock);
R
Ram Pai 已提交
1761
	umount_tree(root, 0, &umount_list);
L
Linus Torvalds 已提交
1762
	spin_unlock(&vfsmount_lock);
R
Ram Pai 已提交
1763
	up_write(&namespace_sem);
R
Ram Pai 已提交
1764
	release_mounts(&umount_list);
L
Linus Torvalds 已提交
1765 1766
	kfree(namespace);
}