ia64/linux-2.6.18-xen.hg

view fs/namespace.c @ 452:c7ed6fe5dca0

kexec: dont initialise regions in reserve_memory()

There is no need to initialise efi_memmap_res and boot_param_res in
reserve_memory() for the initial xen domain as it is done in
machine_kexec_setup_resources() using values from the kexec hypercall.

Signed-off-by: Simon Horman <horms@verge.net.au>
author Keir Fraser <keir.fraser@citrix.com>
date Thu Feb 28 10:55:18 2008 +0000 (2008-02-28)
parents 831230e53067
children
line source
1 /*
2 * linux/fs/namespace.c
3 *
4 * (C) Copyright Al Viro 2000, 2001
5 * Released under GPL v2.
6 *
7 * Based on code from fs/super.c, copyright Linus Torvalds and others.
8 * Heavily rewritten.
9 */
11 #include <linux/syscalls.h>
12 #include <linux/slab.h>
13 #include <linux/sched.h>
14 #include <linux/smp_lock.h>
15 #include <linux/init.h>
16 #include <linux/quotaops.h>
17 #include <linux/acct.h>
18 #include <linux/capability.h>
19 #include <linux/module.h>
20 #include <linux/seq_file.h>
21 #include <linux/namespace.h>
22 #include <linux/namei.h>
23 #include <linux/security.h>
24 #include <linux/mount.h>
25 #include <asm/uaccess.h>
26 #include <asm/unistd.h>
27 #include "pnode.h"
29 extern int __init init_rootfs(void);
31 #ifdef CONFIG_SYSFS
32 extern int __init sysfs_init(void);
33 #else
34 static inline int sysfs_init(void)
35 {
36 return 0;
37 }
38 #endif
40 /* spinlock for vfsmount related operations, inplace of dcache_lock */
41 __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock);
43 static int event;
45 static struct list_head *mount_hashtable __read_mostly;
46 static int hash_mask __read_mostly, hash_bits __read_mostly;
47 static kmem_cache_t *mnt_cache __read_mostly;
48 static struct rw_semaphore namespace_sem;
50 /* /sys/fs */
51 decl_subsys(fs, NULL, NULL);
52 EXPORT_SYMBOL_GPL(fs_subsys);
54 static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry)
55 {
56 unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
57 tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
58 tmp = tmp + (tmp >> hash_bits);
59 return tmp & hash_mask;
60 }
62 struct vfsmount *alloc_vfsmnt(const char *name)
63 {
64 struct vfsmount *mnt = kmem_cache_alloc(mnt_cache, GFP_KERNEL);
65 if (mnt) {
66 memset(mnt, 0, sizeof(struct vfsmount));
67 atomic_set(&mnt->mnt_count, 1);
68 INIT_LIST_HEAD(&mnt->mnt_hash);
69 INIT_LIST_HEAD(&mnt->mnt_child);
70 INIT_LIST_HEAD(&mnt->mnt_mounts);
71 INIT_LIST_HEAD(&mnt->mnt_list);
72 INIT_LIST_HEAD(&mnt->mnt_expire);
73 INIT_LIST_HEAD(&mnt->mnt_share);
74 INIT_LIST_HEAD(&mnt->mnt_slave_list);
75 INIT_LIST_HEAD(&mnt->mnt_slave);
76 if (name) {
77 int size = strlen(name) + 1;
78 char *newname = kmalloc(size, GFP_KERNEL);
79 if (newname) {
80 memcpy(newname, name, size);
81 mnt->mnt_devname = newname;
82 }
83 }
84 }
85 return mnt;
86 }
88 int simple_set_mnt(struct vfsmount *mnt, struct super_block *sb)
89 {
90 mnt->mnt_sb = sb;
91 mnt->mnt_root = dget(sb->s_root);
92 return 0;
93 }
95 EXPORT_SYMBOL(simple_set_mnt);
97 void free_vfsmnt(struct vfsmount *mnt)
98 {
99 kfree(mnt->mnt_devname);
100 kmem_cache_free(mnt_cache, mnt);
101 }
103 /*
104 * find the first or last mount at @dentry on vfsmount @mnt depending on
105 * @dir. If @dir is set return the first mount else return the last mount.
106 */
107 struct vfsmount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry,
108 int dir)
109 {
110 struct list_head *head = mount_hashtable + hash(mnt, dentry);
111 struct list_head *tmp = head;
112 struct vfsmount *p, *found = NULL;
114 for (;;) {
115 tmp = dir ? tmp->next : tmp->prev;
116 p = NULL;
117 if (tmp == head)
118 break;
119 p = list_entry(tmp, struct vfsmount, mnt_hash);
120 if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) {
121 found = p;
122 break;
123 }
124 }
125 return found;
126 }
128 /*
129 * lookup_mnt increments the ref count before returning
130 * the vfsmount struct.
131 */
132 struct vfsmount *lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
133 {
134 struct vfsmount *child_mnt;
135 spin_lock(&vfsmount_lock);
136 if ((child_mnt = __lookup_mnt(mnt, dentry, 1)))
137 mntget(child_mnt);
138 spin_unlock(&vfsmount_lock);
139 return child_mnt;
140 }
142 static inline int check_mnt(struct vfsmount *mnt)
143 {
144 return mnt->mnt_namespace == current->namespace;
145 }
147 static void touch_namespace(struct namespace *ns)
148 {
149 if (ns) {
150 ns->event = ++event;
151 wake_up_interruptible(&ns->poll);
152 }
153 }
155 static void __touch_namespace(struct namespace *ns)
156 {
157 if (ns && ns->event != event) {
158 ns->event = event;
159 wake_up_interruptible(&ns->poll);
160 }
161 }
163 static void detach_mnt(struct vfsmount *mnt, struct nameidata *old_nd)
164 {
165 old_nd->dentry = mnt->mnt_mountpoint;
166 old_nd->mnt = mnt->mnt_parent;
167 mnt->mnt_parent = mnt;
168 mnt->mnt_mountpoint = mnt->mnt_root;
169 list_del_init(&mnt->mnt_child);
170 list_del_init(&mnt->mnt_hash);
171 old_nd->dentry->d_mounted--;
172 }
174 void mnt_set_mountpoint(struct vfsmount *mnt, struct dentry *dentry,
175 struct vfsmount *child_mnt)
176 {
177 child_mnt->mnt_parent = mntget(mnt);
178 child_mnt->mnt_mountpoint = dget(dentry);
179 dentry->d_mounted++;
180 }
182 static void attach_mnt(struct vfsmount *mnt, struct nameidata *nd)
183 {
184 mnt_set_mountpoint(nd->mnt, nd->dentry, mnt);
185 list_add_tail(&mnt->mnt_hash, mount_hashtable +
186 hash(nd->mnt, nd->dentry));
187 list_add_tail(&mnt->mnt_child, &nd->mnt->mnt_mounts);
188 }
190 /*
191 * the caller must hold vfsmount_lock
192 */
193 static void commit_tree(struct vfsmount *mnt)
194 {
195 struct vfsmount *parent = mnt->mnt_parent;
196 struct vfsmount *m;
197 LIST_HEAD(head);
198 struct namespace *n = parent->mnt_namespace;
200 BUG_ON(parent == mnt);
202 list_add_tail(&head, &mnt->mnt_list);
203 list_for_each_entry(m, &head, mnt_list)
204 m->mnt_namespace = n;
205 list_splice(&head, n->list.prev);
207 list_add_tail(&mnt->mnt_hash, mount_hashtable +
208 hash(parent, mnt->mnt_mountpoint));
209 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
210 touch_namespace(n);
211 }
213 static struct vfsmount *next_mnt(struct vfsmount *p, struct vfsmount *root)
214 {
215 struct list_head *next = p->mnt_mounts.next;
216 if (next == &p->mnt_mounts) {
217 while (1) {
218 if (p == root)
219 return NULL;
220 next = p->mnt_child.next;
221 if (next != &p->mnt_parent->mnt_mounts)
222 break;
223 p = p->mnt_parent;
224 }
225 }
226 return list_entry(next, struct vfsmount, mnt_child);
227 }
229 static struct vfsmount *skip_mnt_tree(struct vfsmount *p)
230 {
231 struct list_head *prev = p->mnt_mounts.prev;
232 while (prev != &p->mnt_mounts) {
233 p = list_entry(prev, struct vfsmount, mnt_child);
234 prev = p->mnt_mounts.prev;
235 }
236 return p;
237 }
239 static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root,
240 int flag)
241 {
242 struct super_block *sb = old->mnt_sb;
243 struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname);
245 if (mnt) {
246 mnt->mnt_flags = old->mnt_flags;
247 atomic_inc(&sb->s_active);
248 mnt->mnt_sb = sb;
249 mnt->mnt_root = dget(root);
250 mnt->mnt_mountpoint = mnt->mnt_root;
251 mnt->mnt_parent = mnt;
253 if (flag & CL_SLAVE) {
254 list_add(&mnt->mnt_slave, &old->mnt_slave_list);
255 mnt->mnt_master = old;
256 CLEAR_MNT_SHARED(mnt);
257 } else {
258 if ((flag & CL_PROPAGATION) || IS_MNT_SHARED(old))
259 list_add(&mnt->mnt_share, &old->mnt_share);
260 if (IS_MNT_SLAVE(old))
261 list_add(&mnt->mnt_slave, &old->mnt_slave);
262 mnt->mnt_master = old->mnt_master;
263 }
264 if (flag & CL_MAKE_SHARED)
265 set_mnt_shared(mnt);
267 /* stick the duplicate mount on the same expiry list
268 * as the original if that was on one */
269 if (flag & CL_EXPIRE) {
270 spin_lock(&vfsmount_lock);
271 if (!list_empty(&old->mnt_expire))
272 list_add(&mnt->mnt_expire, &old->mnt_expire);
273 spin_unlock(&vfsmount_lock);
274 }
275 }
276 return mnt;
277 }
279 static inline void __mntput(struct vfsmount *mnt)
280 {
281 struct super_block *sb = mnt->mnt_sb;
282 dput(mnt->mnt_root);
283 free_vfsmnt(mnt);
284 deactivate_super(sb);
285 }
287 void mntput_no_expire(struct vfsmount *mnt)
288 {
289 repeat:
290 if (atomic_dec_and_lock(&mnt->mnt_count, &vfsmount_lock)) {
291 if (likely(!mnt->mnt_pinned)) {
292 spin_unlock(&vfsmount_lock);
293 __mntput(mnt);
294 return;
295 }
296 atomic_add(mnt->mnt_pinned + 1, &mnt->mnt_count);
297 mnt->mnt_pinned = 0;
298 spin_unlock(&vfsmount_lock);
299 acct_auto_close_mnt(mnt);
300 security_sb_umount_close(mnt);
301 goto repeat;
302 }
303 }
305 EXPORT_SYMBOL(mntput_no_expire);
307 void mnt_pin(struct vfsmount *mnt)
308 {
309 spin_lock(&vfsmount_lock);
310 mnt->mnt_pinned++;
311 spin_unlock(&vfsmount_lock);
312 }
314 EXPORT_SYMBOL(mnt_pin);
316 void mnt_unpin(struct vfsmount *mnt)
317 {
318 spin_lock(&vfsmount_lock);
319 if (mnt->mnt_pinned) {
320 atomic_inc(&mnt->mnt_count);
321 mnt->mnt_pinned--;
322 }
323 spin_unlock(&vfsmount_lock);
324 }
326 EXPORT_SYMBOL(mnt_unpin);
328 /* iterator */
329 static void *m_start(struct seq_file *m, loff_t *pos)
330 {
331 struct namespace *n = m->private;
332 struct list_head *p;
333 loff_t l = *pos;
335 down_read(&namespace_sem);
336 list_for_each(p, &n->list)
337 if (!l--)
338 return list_entry(p, struct vfsmount, mnt_list);
339 return NULL;
340 }
342 static void *m_next(struct seq_file *m, void *v, loff_t *pos)
343 {
344 struct namespace *n = m->private;
345 struct list_head *p = ((struct vfsmount *)v)->mnt_list.next;
346 (*pos)++;
347 return p == &n->list ? NULL : list_entry(p, struct vfsmount, mnt_list);
348 }
350 static void m_stop(struct seq_file *m, void *v)
351 {
352 up_read(&namespace_sem);
353 }
355 static inline void mangle(struct seq_file *m, const char *s)
356 {
357 seq_escape(m, s, " \t\n\\");
358 }
360 static int show_vfsmnt(struct seq_file *m, void *v)
361 {
362 struct vfsmount *mnt = v;
363 int err = 0;
364 static struct proc_fs_info {
365 int flag;
366 char *str;
367 } fs_info[] = {
368 { MS_SYNCHRONOUS, ",sync" },
369 { MS_DIRSYNC, ",dirsync" },
370 { MS_MANDLOCK, ",mand" },
371 { 0, NULL }
372 };
373 static struct proc_fs_info mnt_info[] = {
374 { MNT_NOSUID, ",nosuid" },
375 { MNT_NODEV, ",nodev" },
376 { MNT_NOEXEC, ",noexec" },
377 { MNT_NOATIME, ",noatime" },
378 { MNT_NODIRATIME, ",nodiratime" },
379 { 0, NULL }
380 };
381 struct proc_fs_info *fs_infop;
383 mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
384 seq_putc(m, ' ');
385 seq_path(m, mnt, mnt->mnt_root, " \t\n\\");
386 seq_putc(m, ' ');
387 mangle(m, mnt->mnt_sb->s_type->name);
388 seq_puts(m, mnt->mnt_sb->s_flags & MS_RDONLY ? " ro" : " rw");
389 for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
390 if (mnt->mnt_sb->s_flags & fs_infop->flag)
391 seq_puts(m, fs_infop->str);
392 }
393 for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {
394 if (mnt->mnt_flags & fs_infop->flag)
395 seq_puts(m, fs_infop->str);
396 }
397 if (mnt->mnt_sb->s_op->show_options)
398 err = mnt->mnt_sb->s_op->show_options(m, mnt);
399 seq_puts(m, " 0 0\n");
400 return err;
401 }
403 struct seq_operations mounts_op = {
404 .start = m_start,
405 .next = m_next,
406 .stop = m_stop,
407 .show = show_vfsmnt
408 };
410 static int show_vfsstat(struct seq_file *m, void *v)
411 {
412 struct vfsmount *mnt = v;
413 int err = 0;
415 /* device */
416 if (mnt->mnt_devname) {
417 seq_puts(m, "device ");
418 mangle(m, mnt->mnt_devname);
419 } else
420 seq_puts(m, "no device");
422 /* mount point */
423 seq_puts(m, " mounted on ");
424 seq_path(m, mnt, mnt->mnt_root, " \t\n\\");
425 seq_putc(m, ' ');
427 /* file system type */
428 seq_puts(m, "with fstype ");
429 mangle(m, mnt->mnt_sb->s_type->name);
431 /* optional statistics */
432 if (mnt->mnt_sb->s_op->show_stats) {
433 seq_putc(m, ' ');
434 err = mnt->mnt_sb->s_op->show_stats(m, mnt);
435 }
437 seq_putc(m, '\n');
438 return err;
439 }
441 struct seq_operations mountstats_op = {
442 .start = m_start,
443 .next = m_next,
444 .stop = m_stop,
445 .show = show_vfsstat,
446 };
448 /**
449 * may_umount_tree - check if a mount tree is busy
450 * @mnt: root of mount tree
451 *
452 * This is called to check if a tree of mounts has any
453 * open files, pwds, chroots or sub mounts that are
454 * busy.
455 */
456 int may_umount_tree(struct vfsmount *mnt)
457 {
458 int actual_refs = 0;
459 int minimum_refs = 0;
460 struct vfsmount *p;
462 spin_lock(&vfsmount_lock);
463 for (p = mnt; p; p = next_mnt(p, mnt)) {
464 actual_refs += atomic_read(&p->mnt_count);
465 minimum_refs += 2;
466 }
467 spin_unlock(&vfsmount_lock);
469 if (actual_refs > minimum_refs)
470 return 0;
472 return 1;
473 }
475 EXPORT_SYMBOL(may_umount_tree);
477 /**
478 * may_umount - check if a mount point is busy
479 * @mnt: root of mount
480 *
481 * This is called to check if a mount point has any
482 * open files, pwds, chroots or sub mounts. If the
483 * mount has sub mounts this will return busy
484 * regardless of whether the sub mounts are busy.
485 *
486 * Doesn't take quota and stuff into account. IOW, in some cases it will
487 * give false negatives. The main reason why it's here is that we need
488 * a non-destructive way to look for easily umountable filesystems.
489 */
490 int may_umount(struct vfsmount *mnt)
491 {
492 int ret = 1;
493 spin_lock(&vfsmount_lock);
494 if (propagate_mount_busy(mnt, 2))
495 ret = 0;
496 spin_unlock(&vfsmount_lock);
497 return ret;
498 }
500 EXPORT_SYMBOL(may_umount);
502 void release_mounts(struct list_head *head)
503 {
504 struct vfsmount *mnt;
505 while (!list_empty(head)) {
506 mnt = list_entry(head->next, struct vfsmount, mnt_hash);
507 list_del_init(&mnt->mnt_hash);
508 if (mnt->mnt_parent != mnt) {
509 struct dentry *dentry;
510 struct vfsmount *m;
511 spin_lock(&vfsmount_lock);
512 dentry = mnt->mnt_mountpoint;
513 m = mnt->mnt_parent;
514 mnt->mnt_mountpoint = mnt->mnt_root;
515 mnt->mnt_parent = mnt;
516 spin_unlock(&vfsmount_lock);
517 dput(dentry);
518 mntput(m);
519 }
520 mntput(mnt);
521 }
522 }
524 void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill)
525 {
526 struct vfsmount *p;
528 for (p = mnt; p; p = next_mnt(p, mnt))
529 list_move(&p->mnt_hash, kill);
531 if (propagate)
532 propagate_umount(kill);
534 list_for_each_entry(p, kill, mnt_hash) {
535 list_del_init(&p->mnt_expire);
536 list_del_init(&p->mnt_list);
537 __touch_namespace(p->mnt_namespace);
538 p->mnt_namespace = NULL;
539 list_del_init(&p->mnt_child);
540 if (p->mnt_parent != p)
541 p->mnt_mountpoint->d_mounted--;
542 change_mnt_propagation(p, MS_PRIVATE);
543 }
544 }
546 static int do_umount(struct vfsmount *mnt, int flags)
547 {
548 struct super_block *sb = mnt->mnt_sb;
549 int retval;
550 LIST_HEAD(umount_list);
552 retval = security_sb_umount(mnt, flags);
553 if (retval)
554 return retval;
556 /*
557 * Allow userspace to request a mountpoint be expired rather than
558 * unmounting unconditionally. Unmount only happens if:
559 * (1) the mark is already set (the mark is cleared by mntput())
560 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
561 */
562 if (flags & MNT_EXPIRE) {
563 if (mnt == current->fs->rootmnt ||
564 flags & (MNT_FORCE | MNT_DETACH))
565 return -EINVAL;
567 if (atomic_read(&mnt->mnt_count) != 2)
568 return -EBUSY;
570 if (!xchg(&mnt->mnt_expiry_mark, 1))
571 return -EAGAIN;
572 }
574 /*
575 * If we may have to abort operations to get out of this
576 * mount, and they will themselves hold resources we must
577 * allow the fs to do things. In the Unix tradition of
578 * 'Gee thats tricky lets do it in userspace' the umount_begin
579 * might fail to complete on the first run through as other tasks
580 * must return, and the like. Thats for the mount program to worry
581 * about for the moment.
582 */
584 lock_kernel();
585 if (sb->s_op->umount_begin)
586 sb->s_op->umount_begin(mnt, flags);
587 unlock_kernel();
589 /*
590 * No sense to grab the lock for this test, but test itself looks
591 * somewhat bogus. Suggestions for better replacement?
592 * Ho-hum... In principle, we might treat that as umount + switch
593 * to rootfs. GC would eventually take care of the old vfsmount.
594 * Actually it makes sense, especially if rootfs would contain a
595 * /reboot - static binary that would close all descriptors and
596 * call reboot(9). Then init(8) could umount root and exec /reboot.
597 */
598 if (mnt == current->fs->rootmnt && !(flags & MNT_DETACH)) {
599 /*
600 * Special case for "unmounting" root ...
601 * we just try to remount it readonly.
602 */
603 down_write(&sb->s_umount);
604 if (!(sb->s_flags & MS_RDONLY)) {
605 lock_kernel();
606 DQUOT_OFF(sb);
607 retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
608 unlock_kernel();
609 }
610 up_write(&sb->s_umount);
611 return retval;
612 }
614 down_write(&namespace_sem);
615 spin_lock(&vfsmount_lock);
616 event++;
618 retval = -EBUSY;
619 if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) {
620 if (!list_empty(&mnt->mnt_list))
621 umount_tree(mnt, 1, &umount_list);
622 retval = 0;
623 }
624 spin_unlock(&vfsmount_lock);
625 if (retval)
626 security_sb_umount_busy(mnt);
627 up_write(&namespace_sem);
628 release_mounts(&umount_list);
629 return retval;
630 }
632 /*
633 * Now umount can handle mount points as well as block devices.
634 * This is important for filesystems which use unnamed block devices.
635 *
636 * We now support a flag for forced unmount like the other 'big iron'
637 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
638 */
640 asmlinkage long sys_umount(char __user * name, int flags)
641 {
642 struct nameidata nd;
643 int retval;
645 retval = __user_walk(name, LOOKUP_FOLLOW, &nd);
646 if (retval)
647 goto out;
648 retval = -EINVAL;
649 if (nd.dentry != nd.mnt->mnt_root)
650 goto dput_and_out;
651 if (!check_mnt(nd.mnt))
652 goto dput_and_out;
654 retval = -EPERM;
655 if (!capable(CAP_SYS_ADMIN))
656 goto dput_and_out;
658 retval = do_umount(nd.mnt, flags);
659 dput_and_out:
660 path_release_on_umount(&nd);
661 out:
662 return retval;
663 }
665 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
667 /*
668 * The 2.0 compatible umount. No flags.
669 */
670 asmlinkage long sys_oldumount(char __user * name)
671 {
672 return sys_umount(name, 0);
673 }
675 #endif
677 static int mount_is_safe(struct nameidata *nd)
678 {
679 if (capable(CAP_SYS_ADMIN))
680 return 0;
681 return -EPERM;
682 #ifdef notyet
683 if (S_ISLNK(nd->dentry->d_inode->i_mode))
684 return -EPERM;
685 if (nd->dentry->d_inode->i_mode & S_ISVTX) {
686 if (current->uid != nd->dentry->d_inode->i_uid)
687 return -EPERM;
688 }
689 if (vfs_permission(nd, MAY_WRITE))
690 return -EPERM;
691 return 0;
692 #endif
693 }
695 static int lives_below_in_same_fs(struct dentry *d, struct dentry *dentry)
696 {
697 while (1) {
698 if (d == dentry)
699 return 1;
700 if (d == NULL || d == d->d_parent)
701 return 0;
702 d = d->d_parent;
703 }
704 }
706 struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry,
707 int flag)
708 {
709 struct vfsmount *res, *p, *q, *r, *s;
710 struct nameidata nd;
712 if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt))
713 return NULL;
715 res = q = clone_mnt(mnt, dentry, flag);
716 if (!q)
717 goto Enomem;
718 q->mnt_mountpoint = mnt->mnt_mountpoint;
720 p = mnt;
721 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
722 if (!lives_below_in_same_fs(r->mnt_mountpoint, dentry))
723 continue;
725 for (s = r; s; s = next_mnt(s, r)) {
726 if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) {
727 s = skip_mnt_tree(s);
728 continue;
729 }
730 while (p != s->mnt_parent) {
731 p = p->mnt_parent;
732 q = q->mnt_parent;
733 }
734 p = s;
735 nd.mnt = q;
736 nd.dentry = p->mnt_mountpoint;
737 q = clone_mnt(p, p->mnt_root, flag);
738 if (!q)
739 goto Enomem;
740 spin_lock(&vfsmount_lock);
741 list_add_tail(&q->mnt_list, &res->mnt_list);
742 attach_mnt(q, &nd);
743 spin_unlock(&vfsmount_lock);
744 }
745 }
746 return res;
747 Enomem:
748 if (res) {
749 LIST_HEAD(umount_list);
750 spin_lock(&vfsmount_lock);
751 umount_tree(res, 0, &umount_list);
752 spin_unlock(&vfsmount_lock);
753 release_mounts(&umount_list);
754 }
755 return NULL;
756 }
758 /*
759 * @source_mnt : mount tree to be attached
760 * @nd : place the mount tree @source_mnt is attached
761 * @parent_nd : if non-null, detach the source_mnt from its parent and
762 * store the parent mount and mountpoint dentry.
763 * (done when source_mnt is moved)
764 *
765 * NOTE: in the table below explains the semantics when a source mount
766 * of a given type is attached to a destination mount of a given type.
767 * ---------------------------------------------------------------------------
768 * | BIND MOUNT OPERATION |
769 * |**************************************************************************
770 * | source-->| shared | private | slave | unbindable |
771 * | dest | | | | |
772 * | | | | | | |
773 * | v | | | | |
774 * |**************************************************************************
775 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
776 * | | | | | |
777 * |non-shared| shared (+) | private | slave (*) | invalid |
778 * ***************************************************************************
779 * A bind operation clones the source mount and mounts the clone on the
780 * destination mount.
781 *
782 * (++) the cloned mount is propagated to all the mounts in the propagation
783 * tree of the destination mount and the cloned mount is added to
784 * the peer group of the source mount.
785 * (+) the cloned mount is created under the destination mount and is marked
786 * as shared. The cloned mount is added to the peer group of the source
787 * mount.
788 * (+++) the mount is propagated to all the mounts in the propagation tree
789 * of the destination mount and the cloned mount is made slave
790 * of the same master as that of the source mount. The cloned mount
791 * is marked as 'shared and slave'.
792 * (*) the cloned mount is made a slave of the same master as that of the
793 * source mount.
794 *
795 * ---------------------------------------------------------------------------
796 * | MOVE MOUNT OPERATION |
797 * |**************************************************************************
798 * | source-->| shared | private | slave | unbindable |
799 * | dest | | | | |
800 * | | | | | | |
801 * | v | | | | |
802 * |**************************************************************************
803 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
804 * | | | | | |
805 * |non-shared| shared (+*) | private | slave (*) | unbindable |
806 * ***************************************************************************
807 *
808 * (+) the mount is moved to the destination. And is then propagated to
809 * all the mounts in the propagation tree of the destination mount.
810 * (+*) the mount is moved to the destination.
811 * (+++) the mount is moved to the destination and is then propagated to
812 * all the mounts belonging to the destination mount's propagation tree.
813 * the mount is marked as 'shared and slave'.
814 * (*) the mount continues to be a slave at the new location.
815 *
816 * if the source mount is a tree, the operations explained above is
817 * applied to each mount in the tree.
818 * Must be called without spinlocks held, since this function can sleep
819 * in allocations.
820 */
821 static int attach_recursive_mnt(struct vfsmount *source_mnt,
822 struct nameidata *nd, struct nameidata *parent_nd)
823 {
824 LIST_HEAD(tree_list);
825 struct vfsmount *dest_mnt = nd->mnt;
826 struct dentry *dest_dentry = nd->dentry;
827 struct vfsmount *child, *p;
829 if (propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list))
830 return -EINVAL;
832 if (IS_MNT_SHARED(dest_mnt)) {
833 for (p = source_mnt; p; p = next_mnt(p, source_mnt))
834 set_mnt_shared(p);
835 }
837 spin_lock(&vfsmount_lock);
838 if (parent_nd) {
839 detach_mnt(source_mnt, parent_nd);
840 attach_mnt(source_mnt, nd);
841 touch_namespace(current->namespace);
842 } else {
843 mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt);
844 commit_tree(source_mnt);
845 }
847 list_for_each_entry_safe(child, p, &tree_list, mnt_hash) {
848 list_del_init(&child->mnt_hash);
849 commit_tree(child);
850 }
851 spin_unlock(&vfsmount_lock);
852 return 0;
853 }
855 static int graft_tree(struct vfsmount *mnt, struct nameidata *nd)
856 {
857 int err;
858 if (mnt->mnt_sb->s_flags & MS_NOUSER)
859 return -EINVAL;
861 if (S_ISDIR(nd->dentry->d_inode->i_mode) !=
862 S_ISDIR(mnt->mnt_root->d_inode->i_mode))
863 return -ENOTDIR;
865 err = -ENOENT;
866 mutex_lock(&nd->dentry->d_inode->i_mutex);
867 if (IS_DEADDIR(nd->dentry->d_inode))
868 goto out_unlock;
870 err = security_sb_check_sb(mnt, nd);
871 if (err)
872 goto out_unlock;
874 err = -ENOENT;
875 if (IS_ROOT(nd->dentry) || !d_unhashed(nd->dentry))
876 err = attach_recursive_mnt(mnt, nd, NULL);
877 out_unlock:
878 mutex_unlock(&nd->dentry->d_inode->i_mutex);
879 if (!err)
880 security_sb_post_addmount(mnt, nd);
881 return err;
882 }
884 /*
885 * recursively change the type of the mountpoint.
886 */
887 static int do_change_type(struct nameidata *nd, int flag)
888 {
889 struct vfsmount *m, *mnt = nd->mnt;
890 int recurse = flag & MS_REC;
891 int type = flag & ~MS_REC;
893 if (nd->dentry != nd->mnt->mnt_root)
894 return -EINVAL;
896 down_write(&namespace_sem);
897 spin_lock(&vfsmount_lock);
898 for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
899 change_mnt_propagation(m, type);
900 spin_unlock(&vfsmount_lock);
901 up_write(&namespace_sem);
902 return 0;
903 }
905 /*
906 * do loopback mount.
907 */
908 static int do_loopback(struct nameidata *nd, char *old_name, int recurse)
909 {
910 struct nameidata old_nd;
911 struct vfsmount *mnt = NULL;
912 int err = mount_is_safe(nd);
913 if (err)
914 return err;
915 if (!old_name || !*old_name)
916 return -EINVAL;
917 err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd);
918 if (err)
919 return err;
921 down_write(&namespace_sem);
922 err = -EINVAL;
923 if (IS_MNT_UNBINDABLE(old_nd.mnt))
924 goto out;
926 if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt))
927 goto out;
929 err = -ENOMEM;
930 if (recurse)
931 mnt = copy_tree(old_nd.mnt, old_nd.dentry, 0);
932 else
933 mnt = clone_mnt(old_nd.mnt, old_nd.dentry, 0);
935 if (!mnt)
936 goto out;
938 err = graft_tree(mnt, nd);
939 if (err) {
940 LIST_HEAD(umount_list);
941 spin_lock(&vfsmount_lock);
942 umount_tree(mnt, 0, &umount_list);
943 spin_unlock(&vfsmount_lock);
944 release_mounts(&umount_list);
945 }
947 out:
948 up_write(&namespace_sem);
949 path_release(&old_nd);
950 return err;
951 }
953 /*
954 * change filesystem flags. dir should be a physical root of filesystem.
955 * If you've mounted a non-root directory somewhere and want to do remount
956 * on it - tough luck.
957 */
958 static int do_remount(struct nameidata *nd, int flags, int mnt_flags,
959 void *data)
960 {
961 int err;
962 struct super_block *sb = nd->mnt->mnt_sb;
964 if (!capable(CAP_SYS_ADMIN))
965 return -EPERM;
967 if (!check_mnt(nd->mnt))
968 return -EINVAL;
970 if (nd->dentry != nd->mnt->mnt_root)
971 return -EINVAL;
973 down_write(&sb->s_umount);
974 err = do_remount_sb(sb, flags, data, 0);
975 if (!err)
976 nd->mnt->mnt_flags = mnt_flags;
977 up_write(&sb->s_umount);
978 if (!err)
979 security_sb_post_remount(nd->mnt, flags, data);
980 return err;
981 }
983 static inline int tree_contains_unbindable(struct vfsmount *mnt)
984 {
985 struct vfsmount *p;
986 for (p = mnt; p; p = next_mnt(p, mnt)) {
987 if (IS_MNT_UNBINDABLE(p))
988 return 1;
989 }
990 return 0;
991 }
993 static int do_move_mount(struct nameidata *nd, char *old_name)
994 {
995 struct nameidata old_nd, parent_nd;
996 struct vfsmount *p;
997 int err = 0;
998 if (!capable(CAP_SYS_ADMIN))
999 return -EPERM;
1000 if (!old_name || !*old_name)
1001 return -EINVAL;
1002 err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd);
1003 if (err)
1004 return err;
1006 down_write(&namespace_sem);
1007 while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
1009 err = -EINVAL;
1010 if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt))
1011 goto out;
1013 err = -ENOENT;
1014 mutex_lock(&nd->dentry->d_inode->i_mutex);
1015 if (IS_DEADDIR(nd->dentry->d_inode))
1016 goto out1;
1018 if (!IS_ROOT(nd->dentry) && d_unhashed(nd->dentry))
1019 goto out1;
1021 err = -EINVAL;
1022 if (old_nd.dentry != old_nd.mnt->mnt_root)
1023 goto out1;
1025 if (old_nd.mnt == old_nd.mnt->mnt_parent)
1026 goto out1;
1028 if (S_ISDIR(nd->dentry->d_inode->i_mode) !=
1029 S_ISDIR(old_nd.dentry->d_inode->i_mode))
1030 goto out1;
1031 /*
1032 * Don't move a mount residing in a shared parent.
1033 */
1034 if (old_nd.mnt->mnt_parent && IS_MNT_SHARED(old_nd.mnt->mnt_parent))
1035 goto out1;
1036 /*
1037 * Don't move a mount tree containing unbindable mounts to a destination
1038 * mount which is shared.
1039 */
1040 if (IS_MNT_SHARED(nd->mnt) && tree_contains_unbindable(old_nd.mnt))
1041 goto out1;
1042 err = -ELOOP;
1043 for (p = nd->mnt; p->mnt_parent != p; p = p->mnt_parent)
1044 if (p == old_nd.mnt)
1045 goto out1;
1047 if ((err = attach_recursive_mnt(old_nd.mnt, nd, &parent_nd)))
1048 goto out1;
1050 spin_lock(&vfsmount_lock);
1051 /* if the mount is moved, it should no longer be expire
1052 * automatically */
1053 list_del_init(&old_nd.mnt->mnt_expire);
1054 spin_unlock(&vfsmount_lock);
1055 out1:
1056 mutex_unlock(&nd->dentry->d_inode->i_mutex);
1057 out:
1058 up_write(&namespace_sem);
1059 if (!err)
1060 path_release(&parent_nd);
1061 path_release(&old_nd);
1062 return err;
1065 /*
1066 * create a new mount for userspace and request it to be added into the
1067 * namespace's tree
1068 */
1069 static int do_new_mount(struct nameidata *nd, char *type, int flags,
1070 int mnt_flags, char *name, void *data)
1072 struct vfsmount *mnt;
1074 if (!type || !memchr(type, 0, PAGE_SIZE))
1075 return -EINVAL;
1077 /* we need capabilities... */
1078 if (!capable(CAP_SYS_ADMIN))
1079 return -EPERM;
1081 mnt = do_kern_mount(type, flags, name, data);
1082 if (IS_ERR(mnt))
1083 return PTR_ERR(mnt);
1085 return do_add_mount(mnt, nd, mnt_flags, NULL);
1088 /*
1089 * add a mount into a namespace's mount tree
1090 * - provide the option of adding the new mount to an expiration list
1091 */
1092 int do_add_mount(struct vfsmount *newmnt, struct nameidata *nd,
1093 int mnt_flags, struct list_head *fslist)
1095 int err;
1097 down_write(&namespace_sem);
1098 /* Something was mounted here while we slept */
1099 while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
1101 err = -EINVAL;
1102 if (!check_mnt(nd->mnt))
1103 goto unlock;
1105 /* Refuse the same filesystem on the same mount point */
1106 err = -EBUSY;
1107 if (nd->mnt->mnt_sb == newmnt->mnt_sb &&
1108 nd->mnt->mnt_root == nd->dentry)
1109 goto unlock;
1111 err = -EINVAL;
1112 if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode))
1113 goto unlock;
1115 newmnt->mnt_flags = mnt_flags;
1116 if ((err = graft_tree(newmnt, nd)))
1117 goto unlock;
1119 if (fslist) {
1120 /* add to the specified expiration list */
1121 spin_lock(&vfsmount_lock);
1122 list_add_tail(&newmnt->mnt_expire, fslist);
1123 spin_unlock(&vfsmount_lock);
1125 up_write(&namespace_sem);
1126 return 0;
1128 unlock:
1129 up_write(&namespace_sem);
1130 mntput(newmnt);
1131 return err;
1134 EXPORT_SYMBOL_GPL(do_add_mount);
1136 static void expire_mount(struct vfsmount *mnt, struct list_head *mounts,
1137 struct list_head *umounts)
1139 spin_lock(&vfsmount_lock);
1141 /*
1142 * Check if mount is still attached, if not, let whoever holds it deal
1143 * with the sucker
1144 */
1145 if (mnt->mnt_parent == mnt) {
1146 spin_unlock(&vfsmount_lock);
1147 return;
1150 /*
1151 * Check that it is still dead: the count should now be 2 - as
1152 * contributed by the vfsmount parent and the mntget above
1153 */
1154 if (!propagate_mount_busy(mnt, 2)) {
1155 /* delete from the namespace */
1156 touch_namespace(mnt->mnt_namespace);
1157 list_del_init(&mnt->mnt_list);
1158 mnt->mnt_namespace = NULL;
1159 umount_tree(mnt, 1, umounts);
1160 spin_unlock(&vfsmount_lock);
1161 } else {
1162 /*
1163 * Someone brought it back to life whilst we didn't have any
1164 * locks held so return it to the expiration list
1165 */
1166 list_add_tail(&mnt->mnt_expire, mounts);
1167 spin_unlock(&vfsmount_lock);
1171 /*
1172 * go through the vfsmounts we've just consigned to the graveyard to
1173 * - check that they're still dead
1174 * - delete the vfsmount from the appropriate namespace under lock
1175 * - dispose of the corpse
1176 */
1177 static void expire_mount_list(struct list_head *graveyard, struct list_head *mounts)
1179 struct namespace *namespace;
1180 struct vfsmount *mnt;
1182 while (!list_empty(graveyard)) {
1183 LIST_HEAD(umounts);
1184 mnt = list_entry(graveyard->next, struct vfsmount, mnt_expire);
1185 list_del_init(&mnt->mnt_expire);
1187 /* don't do anything if the namespace is dead - all the
1188 * vfsmounts from it are going away anyway */
1189 namespace = mnt->mnt_namespace;
1190 if (!namespace || !namespace->root)
1191 continue;
1192 get_namespace(namespace);
1194 spin_unlock(&vfsmount_lock);
1195 down_write(&namespace_sem);
1196 expire_mount(mnt, mounts, &umounts);
1197 up_write(&namespace_sem);
1198 release_mounts(&umounts);
1199 mntput(mnt);
1200 put_namespace(namespace);
1201 spin_lock(&vfsmount_lock);
1205 /*
1206 * process a list of expirable mountpoints with the intent of discarding any
1207 * mountpoints that aren't in use and haven't been touched since last we came
1208 * here
1209 */
1210 void mark_mounts_for_expiry(struct list_head *mounts)
1212 struct vfsmount *mnt, *next;
1213 LIST_HEAD(graveyard);
1215 if (list_empty(mounts))
1216 return;
1218 spin_lock(&vfsmount_lock);
1220 /* extract from the expiration list every vfsmount that matches the
1221 * following criteria:
1222 * - only referenced by its parent vfsmount
1223 * - still marked for expiry (marked on the last call here; marks are
1224 * cleared by mntput())
1225 */
1226 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
1227 if (!xchg(&mnt->mnt_expiry_mark, 1) ||
1228 atomic_read(&mnt->mnt_count) != 1)
1229 continue;
1231 mntget(mnt);
1232 list_move(&mnt->mnt_expire, &graveyard);
1235 expire_mount_list(&graveyard, mounts);
1237 spin_unlock(&vfsmount_lock);
1240 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
1242 /*
1243 * Ripoff of 'select_parent()'
1245 * search the list of submounts for a given mountpoint, and move any
1246 * shrinkable submounts to the 'graveyard' list.
1247 */
1248 static int select_submounts(struct vfsmount *parent, struct list_head *graveyard)
1250 struct vfsmount *this_parent = parent;
1251 struct list_head *next;
1252 int found = 0;
1254 repeat:
1255 next = this_parent->mnt_mounts.next;
1256 resume:
1257 while (next != &this_parent->mnt_mounts) {
1258 struct list_head *tmp = next;
1259 struct vfsmount *mnt = list_entry(tmp, struct vfsmount, mnt_child);
1261 next = tmp->next;
1262 if (!(mnt->mnt_flags & MNT_SHRINKABLE))
1263 continue;
1264 /*
1265 * Descend a level if the d_mounts list is non-empty.
1266 */
1267 if (!list_empty(&mnt->mnt_mounts)) {
1268 this_parent = mnt;
1269 goto repeat;
1272 if (!propagate_mount_busy(mnt, 1)) {
1273 mntget(mnt);
1274 list_move_tail(&mnt->mnt_expire, graveyard);
1275 found++;
1278 /*
1279 * All done at this level ... ascend and resume the search
1280 */
1281 if (this_parent != parent) {
1282 next = this_parent->mnt_child.next;
1283 this_parent = this_parent->mnt_parent;
1284 goto resume;
1286 return found;
1289 /*
1290 * process a list of expirable mountpoints with the intent of discarding any
1291 * submounts of a specific parent mountpoint
1292 */
1293 void shrink_submounts(struct vfsmount *mountpoint, struct list_head *mounts)
1295 LIST_HEAD(graveyard);
1296 int found;
1298 spin_lock(&vfsmount_lock);
1300 /* extract submounts of 'mountpoint' from the expiration list */
1301 while ((found = select_submounts(mountpoint, &graveyard)) != 0)
1302 expire_mount_list(&graveyard, mounts);
1304 spin_unlock(&vfsmount_lock);
1307 EXPORT_SYMBOL_GPL(shrink_submounts);
1309 /*
1310 * Some copy_from_user() implementations do not return the exact number of
1311 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
1312 * Note that this function differs from copy_from_user() in that it will oops
1313 * on bad values of `to', rather than returning a short copy.
1314 */
1315 static long exact_copy_from_user(void *to, const void __user * from,
1316 unsigned long n)
1318 char *t = to;
1319 const char __user *f = from;
1320 char c;
1322 if (!access_ok(VERIFY_READ, from, n))
1323 return n;
1325 while (n) {
1326 if (__get_user(c, f)) {
1327 memset(t, 0, n);
1328 break;
1330 *t++ = c;
1331 f++;
1332 n--;
1334 return n;
1337 int copy_mount_options(const void __user * data, unsigned long *where)
1339 int i;
1340 unsigned long page;
1341 unsigned long size;
1343 *where = 0;
1344 if (!data)
1345 return 0;
1347 if (!(page = __get_free_page(GFP_KERNEL)))
1348 return -ENOMEM;
1350 /* We only care that *some* data at the address the user
1351 * gave us is valid. Just in case, we'll zero
1352 * the remainder of the page.
1353 */
1354 /* copy_from_user cannot cross TASK_SIZE ! */
1355 size = TASK_SIZE - (unsigned long)data;
1356 if (size > PAGE_SIZE)
1357 size = PAGE_SIZE;
1359 i = size - exact_copy_from_user((void *)page, data, size);
1360 if (!i) {
1361 free_page(page);
1362 return -EFAULT;
1364 if (i != PAGE_SIZE)
1365 memset((char *)page + i, 0, PAGE_SIZE - i);
1366 *where = page;
1367 return 0;
1370 /*
1371 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
1372 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
1374 * data is a (void *) that can point to any structure up to
1375 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
1376 * information (or be NULL).
1378 * Pre-0.97 versions of mount() didn't have a flags word.
1379 * When the flags word was introduced its top half was required
1380 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
1381 * Therefore, if this magic number is present, it carries no information
1382 * and must be discarded.
1383 */
1384 long do_mount(char *dev_name, char *dir_name, char *type_page,
1385 unsigned long flags, void *data_page)
1387 struct nameidata nd;
1388 int retval = 0;
1389 int mnt_flags = 0;
1391 /* Discard magic */
1392 if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
1393 flags &= ~MS_MGC_MSK;
1395 /* Basic sanity checks */
1397 if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE))
1398 return -EINVAL;
1399 if (dev_name && !memchr(dev_name, 0, PAGE_SIZE))
1400 return -EINVAL;
1402 if (data_page)
1403 ((char *)data_page)[PAGE_SIZE - 1] = 0;
1405 /* Separate the per-mountpoint flags */
1406 if (flags & MS_NOSUID)
1407 mnt_flags |= MNT_NOSUID;
1408 if (flags & MS_NODEV)
1409 mnt_flags |= MNT_NODEV;
1410 if (flags & MS_NOEXEC)
1411 mnt_flags |= MNT_NOEXEC;
1412 if (flags & MS_NOATIME)
1413 mnt_flags |= MNT_NOATIME;
1414 if (flags & MS_NODIRATIME)
1415 mnt_flags |= MNT_NODIRATIME;
1417 flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE |
1418 MS_NOATIME | MS_NODIRATIME);
1420 /* ... and get the mountpoint */
1421 retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd);
1422 if (retval)
1423 return retval;
1425 retval = security_sb_mount(dev_name, &nd, type_page, flags, data_page);
1426 if (retval)
1427 goto dput_out;
1429 if (flags & MS_REMOUNT)
1430 retval = do_remount(&nd, flags & ~MS_REMOUNT, mnt_flags,
1431 data_page);
1432 else if (flags & MS_BIND)
1433 retval = do_loopback(&nd, dev_name, flags & MS_REC);
1434 else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
1435 retval = do_change_type(&nd, flags);
1436 else if (flags & MS_MOVE)
1437 retval = do_move_mount(&nd, dev_name);
1438 else
1439 retval = do_new_mount(&nd, type_page, flags, mnt_flags,
1440 dev_name, data_page);
1441 dput_out:
1442 path_release(&nd);
1443 return retval;
1446 /*
1447 * Allocate a new namespace structure and populate it with contents
1448 * copied from the namespace of the passed in task structure.
1449 */
1450 struct namespace *dup_namespace(struct task_struct *tsk, struct fs_struct *fs)
1452 struct namespace *namespace = tsk->namespace;
1453 struct namespace *new_ns;
1454 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL, *altrootmnt = NULL;
1455 struct vfsmount *p, *q;
1457 new_ns = kmalloc(sizeof(struct namespace), GFP_KERNEL);
1458 if (!new_ns)
1459 return NULL;
1461 atomic_set(&new_ns->count, 1);
1462 INIT_LIST_HEAD(&new_ns->list);
1463 init_waitqueue_head(&new_ns->poll);
1464 new_ns->event = 0;
1466 down_write(&namespace_sem);
1467 /* First pass: copy the tree topology */
1468 new_ns->root = copy_tree(namespace->root, namespace->root->mnt_root,
1469 CL_COPY_ALL | CL_EXPIRE);
1470 if (!new_ns->root) {
1471 up_write(&namespace_sem);
1472 kfree(new_ns);
1473 return NULL;
1475 spin_lock(&vfsmount_lock);
1476 list_add_tail(&new_ns->list, &new_ns->root->mnt_list);
1477 spin_unlock(&vfsmount_lock);
1479 /*
1480 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
1481 * as belonging to new namespace. We have already acquired a private
1482 * fs_struct, so tsk->fs->lock is not needed.
1483 */
1484 p = namespace->root;
1485 q = new_ns->root;
1486 while (p) {
1487 q->mnt_namespace = new_ns;
1488 if (fs) {
1489 if (p == fs->rootmnt) {
1490 rootmnt = p;
1491 fs->rootmnt = mntget(q);
1493 if (p == fs->pwdmnt) {
1494 pwdmnt = p;
1495 fs->pwdmnt = mntget(q);
1497 if (p == fs->altrootmnt) {
1498 altrootmnt = p;
1499 fs->altrootmnt = mntget(q);
1502 p = next_mnt(p, namespace->root);
1503 q = next_mnt(q, new_ns->root);
1505 up_write(&namespace_sem);
1507 if (rootmnt)
1508 mntput(rootmnt);
1509 if (pwdmnt)
1510 mntput(pwdmnt);
1511 if (altrootmnt)
1512 mntput(altrootmnt);
1514 return new_ns;
1517 int copy_namespace(int flags, struct task_struct *tsk)
1519 struct namespace *namespace = tsk->namespace;
1520 struct namespace *new_ns;
1521 int err = 0;
1523 if (!namespace)
1524 return 0;
1526 get_namespace(namespace);
1528 if (!(flags & CLONE_NEWNS))
1529 return 0;
1531 if (!capable(CAP_SYS_ADMIN)) {
1532 err = -EPERM;
1533 goto out;
1536 new_ns = dup_namespace(tsk, tsk->fs);
1537 if (!new_ns) {
1538 err = -ENOMEM;
1539 goto out;
1542 tsk->namespace = new_ns;
1544 out:
1545 put_namespace(namespace);
1546 return err;
1549 asmlinkage long sys_mount(char __user * dev_name, char __user * dir_name,
1550 char __user * type, unsigned long flags,
1551 void __user * data)
1553 int retval;
1554 unsigned long data_page;
1555 unsigned long type_page;
1556 unsigned long dev_page;
1557 char *dir_page;
1559 retval = copy_mount_options(type, &type_page);
1560 if (retval < 0)
1561 return retval;
1563 dir_page = getname(dir_name);
1564 retval = PTR_ERR(dir_page);
1565 if (IS_ERR(dir_page))
1566 goto out1;
1568 retval = copy_mount_options(dev_name, &dev_page);
1569 if (retval < 0)
1570 goto out2;
1572 retval = copy_mount_options(data, &data_page);
1573 if (retval < 0)
1574 goto out3;
1576 lock_kernel();
1577 retval = do_mount((char *)dev_page, dir_page, (char *)type_page,
1578 flags, (void *)data_page);
1579 unlock_kernel();
1580 free_page(data_page);
1582 out3:
1583 free_page(dev_page);
1584 out2:
1585 putname(dir_page);
1586 out1:
1587 free_page(type_page);
1588 return retval;
1591 /*
1592 * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
1593 * It can block. Requires the big lock held.
1594 */
1595 void set_fs_root(struct fs_struct *fs, struct vfsmount *mnt,
1596 struct dentry *dentry)
1598 struct dentry *old_root;
1599 struct vfsmount *old_rootmnt;
1600 write_lock(&fs->lock);
1601 old_root = fs->root;
1602 old_rootmnt = fs->rootmnt;
1603 fs->rootmnt = mntget(mnt);
1604 fs->root = dget(dentry);
1605 write_unlock(&fs->lock);
1606 if (old_root) {
1607 dput(old_root);
1608 mntput(old_rootmnt);
1612 /*
1613 * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
1614 * It can block. Requires the big lock held.
1615 */
1616 void set_fs_pwd(struct fs_struct *fs, struct vfsmount *mnt,
1617 struct dentry *dentry)
1619 struct dentry *old_pwd;
1620 struct vfsmount *old_pwdmnt;
1622 write_lock(&fs->lock);
1623 old_pwd = fs->pwd;
1624 old_pwdmnt = fs->pwdmnt;
1625 fs->pwdmnt = mntget(mnt);
1626 fs->pwd = dget(dentry);
1627 write_unlock(&fs->lock);
1629 if (old_pwd) {
1630 dput(old_pwd);
1631 mntput(old_pwdmnt);
1635 static void chroot_fs_refs(struct nameidata *old_nd, struct nameidata *new_nd)
1637 struct task_struct *g, *p;
1638 struct fs_struct *fs;
1640 read_lock(&tasklist_lock);
1641 do_each_thread(g, p) {
1642 task_lock(p);
1643 fs = p->fs;
1644 if (fs) {
1645 atomic_inc(&fs->count);
1646 task_unlock(p);
1647 if (fs->root == old_nd->dentry
1648 && fs->rootmnt == old_nd->mnt)
1649 set_fs_root(fs, new_nd->mnt, new_nd->dentry);
1650 if (fs->pwd == old_nd->dentry
1651 && fs->pwdmnt == old_nd->mnt)
1652 set_fs_pwd(fs, new_nd->mnt, new_nd->dentry);
1653 put_fs_struct(fs);
1654 } else
1655 task_unlock(p);
1656 } while_each_thread(g, p);
1657 read_unlock(&tasklist_lock);
1660 /*
1661 * pivot_root Semantics:
1662 * Moves the root file system of the current process to the directory put_old,
1663 * makes new_root as the new root file system of the current process, and sets
1664 * root/cwd of all processes which had them on the current root to new_root.
1666 * Restrictions:
1667 * The new_root and put_old must be directories, and must not be on the
1668 * same file system as the current process root. The put_old must be
1669 * underneath new_root, i.e. adding a non-zero number of /.. to the string
1670 * pointed to by put_old must yield the same directory as new_root. No other
1671 * file system may be mounted on put_old. After all, new_root is a mountpoint.
1673 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
1674 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
1675 * in this situation.
1677 * Notes:
1678 * - we don't move root/cwd if they are not at the root (reason: if something
1679 * cared enough to change them, it's probably wrong to force them elsewhere)
1680 * - it's okay to pick a root that isn't the root of a file system, e.g.
1681 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
1682 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
1683 * first.
1684 */
1685 asmlinkage long sys_pivot_root(const char __user * new_root,
1686 const char __user * put_old)
1688 struct vfsmount *tmp;
1689 struct nameidata new_nd, old_nd, parent_nd, root_parent, user_nd;
1690 int error;
1692 if (!capable(CAP_SYS_ADMIN))
1693 return -EPERM;
1695 lock_kernel();
1697 error = __user_walk(new_root, LOOKUP_FOLLOW | LOOKUP_DIRECTORY,
1698 &new_nd);
1699 if (error)
1700 goto out0;
1701 error = -EINVAL;
1702 if (!check_mnt(new_nd.mnt))
1703 goto out1;
1705 error = __user_walk(put_old, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old_nd);
1706 if (error)
1707 goto out1;
1709 error = security_sb_pivotroot(&old_nd, &new_nd);
1710 if (error) {
1711 path_release(&old_nd);
1712 goto out1;
1715 read_lock(&current->fs->lock);
1716 user_nd.mnt = mntget(current->fs->rootmnt);
1717 user_nd.dentry = dget(current->fs->root);
1718 read_unlock(&current->fs->lock);
1719 down_write(&namespace_sem);
1720 mutex_lock(&old_nd.dentry->d_inode->i_mutex);
1721 error = -EINVAL;
1722 if (IS_MNT_SHARED(old_nd.mnt) ||
1723 IS_MNT_SHARED(new_nd.mnt->mnt_parent) ||
1724 IS_MNT_SHARED(user_nd.mnt->mnt_parent))
1725 goto out2;
1726 if (!check_mnt(user_nd.mnt))
1727 goto out2;
1728 error = -ENOENT;
1729 if (IS_DEADDIR(new_nd.dentry->d_inode))
1730 goto out2;
1731 if (d_unhashed(new_nd.dentry) && !IS_ROOT(new_nd.dentry))
1732 goto out2;
1733 if (d_unhashed(old_nd.dentry) && !IS_ROOT(old_nd.dentry))
1734 goto out2;
1735 error = -EBUSY;
1736 if (new_nd.mnt == user_nd.mnt || old_nd.mnt == user_nd.mnt)
1737 goto out2; /* loop, on the same file system */
1738 error = -EINVAL;
1739 if (user_nd.mnt->mnt_root != user_nd.dentry)
1740 goto out2; /* not a mountpoint */
1741 if (user_nd.mnt->mnt_parent == user_nd.mnt)
1742 goto out2; /* not attached */
1743 if (new_nd.mnt->mnt_root != new_nd.dentry)
1744 goto out2; /* not a mountpoint */
1745 if (new_nd.mnt->mnt_parent == new_nd.mnt)
1746 goto out2; /* not attached */
1747 tmp = old_nd.mnt; /* make sure we can reach put_old from new_root */
1748 spin_lock(&vfsmount_lock);
1749 if (tmp != new_nd.mnt) {
1750 for (;;) {
1751 if (tmp->mnt_parent == tmp)
1752 goto out3; /* already mounted on put_old */
1753 if (tmp->mnt_parent == new_nd.mnt)
1754 break;
1755 tmp = tmp->mnt_parent;
1757 if (!is_subdir(tmp->mnt_mountpoint, new_nd.dentry))
1758 goto out3;
1759 } else if (!is_subdir(old_nd.dentry, new_nd.dentry))
1760 goto out3;
1761 detach_mnt(new_nd.mnt, &parent_nd);
1762 detach_mnt(user_nd.mnt, &root_parent);
1763 attach_mnt(user_nd.mnt, &old_nd); /* mount old root on put_old */
1764 attach_mnt(new_nd.mnt, &root_parent); /* mount new_root on / */
1765 touch_namespace(current->namespace);
1766 spin_unlock(&vfsmount_lock);
1767 chroot_fs_refs(&user_nd, &new_nd);
1768 security_sb_post_pivotroot(&user_nd, &new_nd);
1769 error = 0;
1770 path_release(&root_parent);
1771 path_release(&parent_nd);
1772 out2:
1773 mutex_unlock(&old_nd.dentry->d_inode->i_mutex);
1774 up_write(&namespace_sem);
1775 path_release(&user_nd);
1776 path_release(&old_nd);
1777 out1:
1778 path_release(&new_nd);
1779 out0:
1780 unlock_kernel();
1781 return error;
1782 out3:
1783 spin_unlock(&vfsmount_lock);
1784 goto out2;
1787 static void __init init_mount_tree(void)
1789 struct vfsmount *mnt;
1790 struct namespace *namespace;
1791 struct task_struct *g, *p;
1793 mnt = do_kern_mount("rootfs", 0, "rootfs", NULL);
1794 if (IS_ERR(mnt))
1795 panic("Can't create rootfs");
1796 namespace = kmalloc(sizeof(*namespace), GFP_KERNEL);
1797 if (!namespace)
1798 panic("Can't allocate initial namespace");
1799 atomic_set(&namespace->count, 1);
1800 INIT_LIST_HEAD(&namespace->list);
1801 init_waitqueue_head(&namespace->poll);
1802 namespace->event = 0;
1803 list_add(&mnt->mnt_list, &namespace->list);
1804 namespace->root = mnt;
1805 mnt->mnt_namespace = namespace;
1807 init_task.namespace = namespace;
1808 read_lock(&tasklist_lock);
1809 do_each_thread(g, p) {
1810 get_namespace(namespace);
1811 p->namespace = namespace;
1812 } while_each_thread(g, p);
1813 read_unlock(&tasklist_lock);
1815 set_fs_pwd(current->fs, namespace->root, namespace->root->mnt_root);
1816 set_fs_root(current->fs, namespace->root, namespace->root->mnt_root);
1819 void __init mnt_init(unsigned long mempages)
1821 struct list_head *d;
1822 unsigned int nr_hash;
1823 int i;
1825 init_rwsem(&namespace_sem);
1827 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount),
1828 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL, NULL);
1830 mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);
1832 if (!mount_hashtable)
1833 panic("Failed to allocate mount hash table\n");
1835 /*
1836 * Find the power-of-two list-heads that can fit into the allocation..
1837 * We don't guarantee that "sizeof(struct list_head)" is necessarily
1838 * a power-of-two.
1839 */
1840 nr_hash = PAGE_SIZE / sizeof(struct list_head);
1841 hash_bits = 0;
1842 do {
1843 hash_bits++;
1844 } while ((nr_hash >> hash_bits) != 0);
1845 hash_bits--;
1847 /*
1848 * Re-calculate the actual number of entries and the mask
1849 * from the number of bits we can fit.
1850 */
1851 nr_hash = 1UL << hash_bits;
1852 hash_mask = nr_hash - 1;
1854 printk("Mount-cache hash table entries: %d\n", nr_hash);
1856 /* And initialize the newly allocated array */
1857 d = mount_hashtable;
1858 i = nr_hash;
1859 do {
1860 INIT_LIST_HEAD(d);
1861 d++;
1862 i--;
1863 } while (i);
1864 sysfs_init();
1865 subsystem_register(&fs_subsys);
1866 init_rootfs();
1867 init_mount_tree();
1870 void __put_namespace(struct namespace *namespace)
1872 struct vfsmount *root = namespace->root;
1873 LIST_HEAD(umount_list);
1874 namespace->root = NULL;
1875 spin_unlock(&vfsmount_lock);
1876 down_write(&namespace_sem);
1877 spin_lock(&vfsmount_lock);
1878 umount_tree(root, 0, &umount_list);
1879 spin_unlock(&vfsmount_lock);
1880 up_write(&namespace_sem);
1881 release_mounts(&umount_list);
1882 kfree(namespace);