4 * (C) Copyright Al Viro 2000, 2001
5 * Released under GPL v2.
7 * Based on code from fs/super.c, copyright Linus Torvalds and others.
11 #include <linux/config.h>
12 #include <linux/syscalls.h>
13 #include <linux/slab.h>
14 #include <linux/sched.h>
15 #include <linux/smp_lock.h>
16 #include <linux/init.h>
17 #include <linux/quotaops.h>
18 #include <linux/acct.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>
28 extern int __init init_rootfs(void);
31 extern int __init sysfs_init(void);
33 static inline int sysfs_init(void)
39 /* spinlock for vfsmount related operations, inplace of dcache_lock */
40 __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock);
44 static struct list_head *mount_hashtable;
45 static int hash_mask __read_mostly, hash_bits __read_mostly;
46 static kmem_cache_t *mnt_cache;
48 static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry)
50 unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
51 tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
52 tmp = tmp + (tmp >> hash_bits);
53 return tmp & hash_mask;
56 struct vfsmount *alloc_vfsmnt(const char *name)
58 struct vfsmount *mnt = kmem_cache_alloc(mnt_cache, GFP_KERNEL);
60 memset(mnt, 0, sizeof(struct vfsmount));
61 atomic_set(&mnt->mnt_count, 1);
62 INIT_LIST_HEAD(&mnt->mnt_hash);
63 INIT_LIST_HEAD(&mnt->mnt_child);
64 INIT_LIST_HEAD(&mnt->mnt_mounts);
65 INIT_LIST_HEAD(&mnt->mnt_list);
66 INIT_LIST_HEAD(&mnt->mnt_expire);
68 int size = strlen(name) + 1;
69 char *newname = kmalloc(size, GFP_KERNEL);
71 memcpy(newname, name, size);
72 mnt->mnt_devname = newname;
79 void free_vfsmnt(struct vfsmount *mnt)
81 kfree(mnt->mnt_devname);
82 kmem_cache_free(mnt_cache, mnt);
86 * Now, lookup_mnt increments the ref count before returning
87 * the vfsmount struct.
89 struct vfsmount *lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
91 struct list_head *head = mount_hashtable + hash(mnt, dentry);
92 struct list_head *tmp = head;
93 struct vfsmount *p, *found = NULL;
95 spin_lock(&vfsmount_lock);
101 p = list_entry(tmp, struct vfsmount, mnt_hash);
102 if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) {
107 spin_unlock(&vfsmount_lock);
111 static inline int check_mnt(struct vfsmount *mnt)
113 return mnt->mnt_namespace == current->namespace;
116 static void touch_namespace(struct namespace *ns)
120 wake_up_interruptible(&ns->poll);
124 static void __touch_namespace(struct namespace *ns)
126 if (ns && ns->event != event) {
128 wake_up_interruptible(&ns->poll);
132 static void detach_mnt(struct vfsmount *mnt, struct nameidata *old_nd)
134 old_nd->dentry = mnt->mnt_mountpoint;
135 old_nd->mnt = mnt->mnt_parent;
136 mnt->mnt_parent = mnt;
137 mnt->mnt_mountpoint = mnt->mnt_root;
138 list_del_init(&mnt->mnt_child);
139 list_del_init(&mnt->mnt_hash);
140 old_nd->dentry->d_mounted--;
143 static void attach_mnt(struct vfsmount *mnt, struct nameidata *nd)
145 mnt->mnt_parent = mntget(nd->mnt);
146 mnt->mnt_mountpoint = dget(nd->dentry);
147 list_add(&mnt->mnt_hash, mount_hashtable + hash(nd->mnt, nd->dentry));
148 list_add_tail(&mnt->mnt_child, &nd->mnt->mnt_mounts);
149 nd->dentry->d_mounted++;
152 static struct vfsmount *next_mnt(struct vfsmount *p, struct vfsmount *root)
154 struct list_head *next = p->mnt_mounts.next;
155 if (next == &p->mnt_mounts) {
159 next = p->mnt_child.next;
160 if (next != &p->mnt_parent->mnt_mounts)
165 return list_entry(next, struct vfsmount, mnt_child);
168 static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root)
170 struct super_block *sb = old->mnt_sb;
171 struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname);
174 mnt->mnt_flags = old->mnt_flags;
175 atomic_inc(&sb->s_active);
177 mnt->mnt_root = dget(root);
178 mnt->mnt_mountpoint = mnt->mnt_root;
179 mnt->mnt_parent = mnt;
180 mnt->mnt_namespace = current->namespace;
182 /* stick the duplicate mount on the same expiry list
183 * as the original if that was on one */
184 spin_lock(&vfsmount_lock);
185 if (!list_empty(&old->mnt_expire))
186 list_add(&mnt->mnt_expire, &old->mnt_expire);
187 spin_unlock(&vfsmount_lock);
192 static inline void __mntput(struct vfsmount *mnt)
194 struct super_block *sb = mnt->mnt_sb;
197 deactivate_super(sb);
200 void mntput_no_expire(struct vfsmount *mnt)
203 if (atomic_dec_and_lock(&mnt->mnt_count, &vfsmount_lock)) {
204 if (likely(!mnt->mnt_pinned)) {
205 spin_unlock(&vfsmount_lock);
209 atomic_add(mnt->mnt_pinned + 1, &mnt->mnt_count);
211 spin_unlock(&vfsmount_lock);
212 acct_auto_close_mnt(mnt);
213 security_sb_umount_close(mnt);
218 EXPORT_SYMBOL(mntput_no_expire);
220 void mnt_pin(struct vfsmount *mnt)
222 spin_lock(&vfsmount_lock);
224 spin_unlock(&vfsmount_lock);
227 EXPORT_SYMBOL(mnt_pin);
229 void mnt_unpin(struct vfsmount *mnt)
231 spin_lock(&vfsmount_lock);
232 if (mnt->mnt_pinned) {
233 atomic_inc(&mnt->mnt_count);
236 spin_unlock(&vfsmount_lock);
239 EXPORT_SYMBOL(mnt_unpin);
242 static void *m_start(struct seq_file *m, loff_t *pos)
244 struct namespace *n = m->private;
249 list_for_each(p, &n->list)
251 return list_entry(p, struct vfsmount, mnt_list);
255 static void *m_next(struct seq_file *m, void *v, loff_t *pos)
257 struct namespace *n = m->private;
258 struct list_head *p = ((struct vfsmount *)v)->mnt_list.next;
260 return p == &n->list ? NULL : list_entry(p, struct vfsmount, mnt_list);
263 static void m_stop(struct seq_file *m, void *v)
265 struct namespace *n = m->private;
269 static inline void mangle(struct seq_file *m, const char *s)
271 seq_escape(m, s, " \t\n\\");
274 static int show_vfsmnt(struct seq_file *m, void *v)
276 struct vfsmount *mnt = v;
278 static struct proc_fs_info {
282 { MS_SYNCHRONOUS, ",sync" },
283 { MS_DIRSYNC, ",dirsync" },
284 { MS_MANDLOCK, ",mand" },
285 { MS_NOATIME, ",noatime" },
286 { MS_NODIRATIME, ",nodiratime" },
289 static struct proc_fs_info mnt_info[] = {
290 { MNT_NOSUID, ",nosuid" },
291 { MNT_NODEV, ",nodev" },
292 { MNT_NOEXEC, ",noexec" },
295 struct proc_fs_info *fs_infop;
297 mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
299 seq_path(m, mnt, mnt->mnt_root, " \t\n\\");
301 mangle(m, mnt->mnt_sb->s_type->name);
302 seq_puts(m, mnt->mnt_sb->s_flags & MS_RDONLY ? " ro" : " rw");
303 for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
304 if (mnt->mnt_sb->s_flags & fs_infop->flag)
305 seq_puts(m, fs_infop->str);
307 for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {
308 if (mnt->mnt_flags & fs_infop->flag)
309 seq_puts(m, fs_infop->str);
311 if (mnt->mnt_sb->s_op->show_options)
312 err = mnt->mnt_sb->s_op->show_options(m, mnt);
313 seq_puts(m, " 0 0\n");
317 struct seq_operations mounts_op = {
325 * may_umount_tree - check if a mount tree is busy
326 * @mnt: root of mount tree
328 * This is called to check if a tree of mounts has any
329 * open files, pwds, chroots or sub mounts that are
332 int may_umount_tree(struct vfsmount *mnt)
334 struct list_head *next;
335 struct vfsmount *this_parent = mnt;
339 spin_lock(&vfsmount_lock);
340 actual_refs = atomic_read(&mnt->mnt_count);
343 next = this_parent->mnt_mounts.next;
345 while (next != &this_parent->mnt_mounts) {
347 list_entry(next, struct vfsmount, mnt_child);
351 actual_refs += atomic_read(&p->mnt_count);
354 if (!list_empty(&p->mnt_mounts)) {
360 if (this_parent != mnt) {
361 next = this_parent->mnt_child.next;
362 this_parent = this_parent->mnt_parent;
365 spin_unlock(&vfsmount_lock);
367 if (actual_refs > minimum_refs)
373 EXPORT_SYMBOL(may_umount_tree);
376 * may_umount - check if a mount point is busy
377 * @mnt: root of mount
379 * This is called to check if a mount point has any
380 * open files, pwds, chroots or sub mounts. If the
381 * mount has sub mounts this will return busy
382 * regardless of whether the sub mounts are busy.
384 * Doesn't take quota and stuff into account. IOW, in some cases it will
385 * give false negatives. The main reason why it's here is that we need
386 * a non-destructive way to look for easily umountable filesystems.
388 int may_umount(struct vfsmount *mnt)
390 if (atomic_read(&mnt->mnt_count) > 2)
395 EXPORT_SYMBOL(may_umount);
397 static void release_mounts(struct list_head *head)
399 struct vfsmount *mnt;
400 while(!list_empty(head)) {
401 mnt = list_entry(head->next, struct vfsmount, mnt_hash);
402 list_del_init(&mnt->mnt_hash);
403 if (mnt->mnt_parent != mnt) {
404 struct dentry *dentry;
406 spin_lock(&vfsmount_lock);
407 dentry = mnt->mnt_mountpoint;
409 mnt->mnt_mountpoint = mnt->mnt_root;
410 mnt->mnt_parent = mnt;
411 spin_unlock(&vfsmount_lock);
419 static void umount_tree(struct vfsmount *mnt, struct list_head *kill)
423 for (p = mnt; p; p = next_mnt(p, mnt)) {
424 list_del(&p->mnt_hash);
425 list_add(&p->mnt_hash, kill);
428 list_for_each_entry(p, kill, mnt_hash) {
429 list_del_init(&p->mnt_expire);
430 list_del_init(&p->mnt_list);
431 __touch_namespace(p->mnt_namespace);
432 p->mnt_namespace = NULL;
433 list_del_init(&p->mnt_child);
434 if (p->mnt_parent != p)
435 mnt->mnt_mountpoint->d_mounted--;
439 static int do_umount(struct vfsmount *mnt, int flags)
441 struct super_block *sb = mnt->mnt_sb;
443 LIST_HEAD(umount_list);
445 retval = security_sb_umount(mnt, flags);
450 * Allow userspace to request a mountpoint be expired rather than
451 * unmounting unconditionally. Unmount only happens if:
452 * (1) the mark is already set (the mark is cleared by mntput())
453 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
455 if (flags & MNT_EXPIRE) {
456 if (mnt == current->fs->rootmnt ||
457 flags & (MNT_FORCE | MNT_DETACH))
460 if (atomic_read(&mnt->mnt_count) != 2)
463 if (!xchg(&mnt->mnt_expiry_mark, 1))
468 * If we may have to abort operations to get out of this
469 * mount, and they will themselves hold resources we must
470 * allow the fs to do things. In the Unix tradition of
471 * 'Gee thats tricky lets do it in userspace' the umount_begin
472 * might fail to complete on the first run through as other tasks
473 * must return, and the like. Thats for the mount program to worry
474 * about for the moment.
478 if ((flags & MNT_FORCE) && sb->s_op->umount_begin)
479 sb->s_op->umount_begin(sb);
483 * No sense to grab the lock for this test, but test itself looks
484 * somewhat bogus. Suggestions for better replacement?
485 * Ho-hum... In principle, we might treat that as umount + switch
486 * to rootfs. GC would eventually take care of the old vfsmount.
487 * Actually it makes sense, especially if rootfs would contain a
488 * /reboot - static binary that would close all descriptors and
489 * call reboot(9). Then init(8) could umount root and exec /reboot.
491 if (mnt == current->fs->rootmnt && !(flags & MNT_DETACH)) {
493 * Special case for "unmounting" root ...
494 * we just try to remount it readonly.
496 down_write(&sb->s_umount);
497 if (!(sb->s_flags & MS_RDONLY)) {
500 retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
503 up_write(&sb->s_umount);
507 down_write(¤t->namespace->sem);
508 spin_lock(&vfsmount_lock);
512 if (atomic_read(&mnt->mnt_count) == 2 || flags & MNT_DETACH) {
513 if (!list_empty(&mnt->mnt_list))
514 umount_tree(mnt, &umount_list);
517 spin_unlock(&vfsmount_lock);
519 security_sb_umount_busy(mnt);
520 up_write(¤t->namespace->sem);
521 release_mounts(&umount_list);
526 * Now umount can handle mount points as well as block devices.
527 * This is important for filesystems which use unnamed block devices.
529 * We now support a flag for forced unmount like the other 'big iron'
530 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
533 asmlinkage long sys_umount(char __user * name, int flags)
538 retval = __user_walk(name, LOOKUP_FOLLOW, &nd);
542 if (nd.dentry != nd.mnt->mnt_root)
544 if (!check_mnt(nd.mnt))
548 if (!capable(CAP_SYS_ADMIN))
551 retval = do_umount(nd.mnt, flags);
553 path_release_on_umount(&nd);
558 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
561 * The 2.0 compatible umount. No flags.
563 asmlinkage long sys_oldumount(char __user * name)
565 return sys_umount(name, 0);
570 static int mount_is_safe(struct nameidata *nd)
572 if (capable(CAP_SYS_ADMIN))
576 if (S_ISLNK(nd->dentry->d_inode->i_mode))
578 if (nd->dentry->d_inode->i_mode & S_ISVTX) {
579 if (current->uid != nd->dentry->d_inode->i_uid)
582 if (permission(nd->dentry->d_inode, MAY_WRITE, nd))
588 static int lives_below_in_same_fs(struct dentry *d, struct dentry *dentry)
593 if (d == NULL || d == d->d_parent)
599 static struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry)
601 struct vfsmount *res, *p, *q, *r, *s;
604 res = q = clone_mnt(mnt, dentry);
607 q->mnt_mountpoint = mnt->mnt_mountpoint;
610 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
611 if (!lives_below_in_same_fs(r->mnt_mountpoint, dentry))
614 for (s = r; s; s = next_mnt(s, r)) {
615 while (p != s->mnt_parent) {
621 nd.dentry = p->mnt_mountpoint;
622 q = clone_mnt(p, p->mnt_root);
625 spin_lock(&vfsmount_lock);
626 list_add_tail(&q->mnt_list, &res->mnt_list);
628 spin_unlock(&vfsmount_lock);
634 LIST_HEAD(umount_list);
635 spin_lock(&vfsmount_lock);
636 umount_tree(res, &umount_list);
637 spin_unlock(&vfsmount_lock);
638 release_mounts(&umount_list);
643 static int graft_tree(struct vfsmount *mnt, struct nameidata *nd)
646 if (mnt->mnt_sb->s_flags & MS_NOUSER)
649 if (S_ISDIR(nd->dentry->d_inode->i_mode) !=
650 S_ISDIR(mnt->mnt_root->d_inode->i_mode))
654 down(&nd->dentry->d_inode->i_sem);
655 if (IS_DEADDIR(nd->dentry->d_inode))
658 err = security_sb_check_sb(mnt, nd);
663 spin_lock(&vfsmount_lock);
664 if (IS_ROOT(nd->dentry) || !d_unhashed(nd->dentry)) {
665 struct list_head head;
668 list_add_tail(&head, &mnt->mnt_list);
669 list_splice(&head, current->namespace->list.prev);
671 touch_namespace(current->namespace);
673 spin_unlock(&vfsmount_lock);
675 up(&nd->dentry->d_inode->i_sem);
677 security_sb_post_addmount(mnt, nd);
684 static int do_loopback(struct nameidata *nd, char *old_name, int recurse)
686 struct nameidata old_nd;
687 struct vfsmount *mnt = NULL;
688 int err = mount_is_safe(nd);
691 if (!old_name || !*old_name)
693 err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd);
697 down_write(¤t->namespace->sem);
699 if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt))
704 mnt = copy_tree(old_nd.mnt, old_nd.dentry);
706 mnt = clone_mnt(old_nd.mnt, old_nd.dentry);
711 /* stop bind mounts from expiring */
712 spin_lock(&vfsmount_lock);
713 list_del_init(&mnt->mnt_expire);
714 spin_unlock(&vfsmount_lock);
716 err = graft_tree(mnt, nd);
718 LIST_HEAD(umount_list);
719 spin_lock(&vfsmount_lock);
720 umount_tree(mnt, &umount_list);
721 spin_unlock(&vfsmount_lock);
722 release_mounts(&umount_list);
726 up_write(¤t->namespace->sem);
727 path_release(&old_nd);
732 * change filesystem flags. dir should be a physical root of filesystem.
733 * If you've mounted a non-root directory somewhere and want to do remount
734 * on it - tough luck.
736 static int do_remount(struct nameidata *nd, int flags, int mnt_flags,
740 struct super_block *sb = nd->mnt->mnt_sb;
742 if (!capable(CAP_SYS_ADMIN))
745 if (!check_mnt(nd->mnt))
748 if (nd->dentry != nd->mnt->mnt_root)
751 down_write(&sb->s_umount);
752 err = do_remount_sb(sb, flags, data, 0);
754 nd->mnt->mnt_flags = mnt_flags;
755 up_write(&sb->s_umount);
757 security_sb_post_remount(nd->mnt, flags, data);
761 static int do_move_mount(struct nameidata *nd, char *old_name)
763 struct nameidata old_nd, parent_nd;
766 if (!capable(CAP_SYS_ADMIN))
768 if (!old_name || !*old_name)
770 err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd);
774 down_write(¤t->namespace->sem);
775 while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
778 if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt))
782 down(&nd->dentry->d_inode->i_sem);
783 if (IS_DEADDIR(nd->dentry->d_inode))
786 spin_lock(&vfsmount_lock);
787 if (!IS_ROOT(nd->dentry) && d_unhashed(nd->dentry))
791 if (old_nd.dentry != old_nd.mnt->mnt_root)
794 if (old_nd.mnt == old_nd.mnt->mnt_parent)
797 if (S_ISDIR(nd->dentry->d_inode->i_mode) !=
798 S_ISDIR(old_nd.dentry->d_inode->i_mode))
802 for (p = nd->mnt; p->mnt_parent != p; p = p->mnt_parent)
807 detach_mnt(old_nd.mnt, &parent_nd);
808 attach_mnt(old_nd.mnt, nd);
809 touch_namespace(current->namespace);
811 /* if the mount is moved, it should no longer be expire
813 list_del_init(&old_nd.mnt->mnt_expire);
815 spin_unlock(&vfsmount_lock);
817 up(&nd->dentry->d_inode->i_sem);
819 up_write(¤t->namespace->sem);
821 path_release(&parent_nd);
822 path_release(&old_nd);
827 * create a new mount for userspace and request it to be added into the
830 static int do_new_mount(struct nameidata *nd, char *type, int flags,
831 int mnt_flags, char *name, void *data)
833 struct vfsmount *mnt;
835 if (!type || !memchr(type, 0, PAGE_SIZE))
838 /* we need capabilities... */
839 if (!capable(CAP_SYS_ADMIN))
842 mnt = do_kern_mount(type, flags, name, data);
846 return do_add_mount(mnt, nd, mnt_flags, NULL);
850 * add a mount into a namespace's mount tree
851 * - provide the option of adding the new mount to an expiration list
853 int do_add_mount(struct vfsmount *newmnt, struct nameidata *nd,
854 int mnt_flags, struct list_head *fslist)
858 down_write(¤t->namespace->sem);
859 /* Something was mounted here while we slept */
860 while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
863 if (!check_mnt(nd->mnt))
866 /* Refuse the same filesystem on the same mount point */
868 if (nd->mnt->mnt_sb == newmnt->mnt_sb &&
869 nd->mnt->mnt_root == nd->dentry)
873 if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode))
876 newmnt->mnt_flags = mnt_flags;
877 if ((err = graft_tree(newmnt, nd)))
881 /* add to the specified expiration list */
882 spin_lock(&vfsmount_lock);
883 list_add_tail(&newmnt->mnt_expire, fslist);
884 spin_unlock(&vfsmount_lock);
886 up_write(¤t->namespace->sem);
890 up_write(¤t->namespace->sem);
895 EXPORT_SYMBOL_GPL(do_add_mount);
897 static void expire_mount(struct vfsmount *mnt, struct list_head *mounts,
898 struct list_head *umounts)
900 spin_lock(&vfsmount_lock);
903 * Check if mount is still attached, if not, let whoever holds it deal
906 if (mnt->mnt_parent == mnt) {
907 spin_unlock(&vfsmount_lock);
912 * Check that it is still dead: the count should now be 2 - as
913 * contributed by the vfsmount parent and the mntget above
915 if (atomic_read(&mnt->mnt_count) == 2) {
916 /* delete from the namespace */
917 touch_namespace(mnt->mnt_namespace);
918 list_del_init(&mnt->mnt_list);
919 mnt->mnt_namespace = NULL;
920 umount_tree(mnt, umounts);
921 spin_unlock(&vfsmount_lock);
924 * Someone brought it back to life whilst we didn't have any
925 * locks held so return it to the expiration list
927 list_add_tail(&mnt->mnt_expire, mounts);
928 spin_unlock(&vfsmount_lock);
933 * process a list of expirable mountpoints with the intent of discarding any
934 * mountpoints that aren't in use and haven't been touched since last we came
937 void mark_mounts_for_expiry(struct list_head *mounts)
939 struct namespace *namespace;
940 struct vfsmount *mnt, *next;
941 LIST_HEAD(graveyard);
943 if (list_empty(mounts))
946 spin_lock(&vfsmount_lock);
948 /* extract from the expiration list every vfsmount that matches the
949 * following criteria:
950 * - only referenced by its parent vfsmount
951 * - still marked for expiry (marked on the last call here; marks are
952 * cleared by mntput())
954 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
955 if (!xchg(&mnt->mnt_expiry_mark, 1) ||
956 atomic_read(&mnt->mnt_count) != 1)
960 list_move(&mnt->mnt_expire, &graveyard);
964 * go through the vfsmounts we've just consigned to the graveyard to
965 * - check that they're still dead
966 * - delete the vfsmount from the appropriate namespace under lock
967 * - dispose of the corpse
969 while (!list_empty(&graveyard)) {
971 mnt = list_entry(graveyard.next, struct vfsmount, mnt_expire);
972 list_del_init(&mnt->mnt_expire);
974 /* don't do anything if the namespace is dead - all the
975 * vfsmounts from it are going away anyway */
976 namespace = mnt->mnt_namespace;
977 if (!namespace || !namespace->root)
979 get_namespace(namespace);
981 spin_unlock(&vfsmount_lock);
982 down_write(&namespace->sem);
983 expire_mount(mnt, mounts, &umounts);
984 up_write(&namespace->sem);
985 release_mounts(&umounts);
987 put_namespace(namespace);
988 spin_lock(&vfsmount_lock);
991 spin_unlock(&vfsmount_lock);
994 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
997 * Some copy_from_user() implementations do not return the exact number of
998 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
999 * Note that this function differs from copy_from_user() in that it will oops
1000 * on bad values of `to', rather than returning a short copy.
1002 static long exact_copy_from_user(void *to, const void __user * from,
1006 const char __user *f = from;
1009 if (!access_ok(VERIFY_READ, from, n))
1013 if (__get_user(c, f)) {
1024 int copy_mount_options(const void __user * data, unsigned long *where)
1034 if (!(page = __get_free_page(GFP_KERNEL)))
1037 /* We only care that *some* data at the address the user
1038 * gave us is valid. Just in case, we'll zero
1039 * the remainder of the page.
1041 /* copy_from_user cannot cross TASK_SIZE ! */
1042 size = TASK_SIZE - (unsigned long)data;
1043 if (size > PAGE_SIZE)
1046 i = size - exact_copy_from_user((void *)page, data, size);
1052 memset((char *)page + i, 0, PAGE_SIZE - i);
1058 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
1059 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
1061 * data is a (void *) that can point to any structure up to
1062 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
1063 * information (or be NULL).
1065 * Pre-0.97 versions of mount() didn't have a flags word.
1066 * When the flags word was introduced its top half was required
1067 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
1068 * Therefore, if this magic number is present, it carries no information
1069 * and must be discarded.
1071 long do_mount(char *dev_name, char *dir_name, char *type_page,
1072 unsigned long flags, void *data_page)
1074 struct nameidata nd;
1079 if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
1080 flags &= ~MS_MGC_MSK;
1082 /* Basic sanity checks */
1084 if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE))
1086 if (dev_name && !memchr(dev_name, 0, PAGE_SIZE))
1090 ((char *)data_page)[PAGE_SIZE - 1] = 0;
1092 /* Separate the per-mountpoint flags */
1093 if (flags & MS_NOSUID)
1094 mnt_flags |= MNT_NOSUID;
1095 if (flags & MS_NODEV)
1096 mnt_flags |= MNT_NODEV;
1097 if (flags & MS_NOEXEC)
1098 mnt_flags |= MNT_NOEXEC;
1099 flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE);
1101 /* ... and get the mountpoint */
1102 retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd);
1106 retval = security_sb_mount(dev_name, &nd, type_page, flags, data_page);
1110 if (flags & MS_REMOUNT)
1111 retval = do_remount(&nd, flags & ~MS_REMOUNT, mnt_flags,
1113 else if (flags & MS_BIND)
1114 retval = do_loopback(&nd, dev_name, flags & MS_REC);
1115 else if (flags & MS_MOVE)
1116 retval = do_move_mount(&nd, dev_name);
1118 retval = do_new_mount(&nd, type_page, flags, mnt_flags,
1119 dev_name, data_page);
1125 int copy_namespace(int flags, struct task_struct *tsk)
1127 struct namespace *namespace = tsk->namespace;
1128 struct namespace *new_ns;
1129 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL, *altrootmnt = NULL;
1130 struct fs_struct *fs = tsk->fs;
1131 struct vfsmount *p, *q;
1136 get_namespace(namespace);
1138 if (!(flags & CLONE_NEWNS))
1141 if (!capable(CAP_SYS_ADMIN)) {
1142 put_namespace(namespace);
1146 new_ns = kmalloc(sizeof(struct namespace), GFP_KERNEL);
1150 atomic_set(&new_ns->count, 1);
1151 init_rwsem(&new_ns->sem);
1152 INIT_LIST_HEAD(&new_ns->list);
1153 init_waitqueue_head(&new_ns->poll);
1156 down_write(&tsk->namespace->sem);
1157 /* First pass: copy the tree topology */
1158 new_ns->root = copy_tree(namespace->root, namespace->root->mnt_root);
1159 if (!new_ns->root) {
1160 up_write(&tsk->namespace->sem);
1164 spin_lock(&vfsmount_lock);
1165 list_add_tail(&new_ns->list, &new_ns->root->mnt_list);
1166 spin_unlock(&vfsmount_lock);
1169 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
1170 * as belonging to new namespace. We have already acquired a private
1171 * fs_struct, so tsk->fs->lock is not needed.
1173 p = namespace->root;
1176 q->mnt_namespace = new_ns;
1178 if (p == fs->rootmnt) {
1180 fs->rootmnt = mntget(q);
1182 if (p == fs->pwdmnt) {
1184 fs->pwdmnt = mntget(q);
1186 if (p == fs->altrootmnt) {
1188 fs->altrootmnt = mntget(q);
1191 p = next_mnt(p, namespace->root);
1192 q = next_mnt(q, new_ns->root);
1194 up_write(&tsk->namespace->sem);
1196 tsk->namespace = new_ns;
1205 put_namespace(namespace);
1209 put_namespace(namespace);
1213 asmlinkage long sys_mount(char __user * dev_name, char __user * dir_name,
1214 char __user * type, unsigned long flags,
1218 unsigned long data_page;
1219 unsigned long type_page;
1220 unsigned long dev_page;
1223 retval = copy_mount_options(type, &type_page);
1227 dir_page = getname(dir_name);
1228 retval = PTR_ERR(dir_page);
1229 if (IS_ERR(dir_page))
1232 retval = copy_mount_options(dev_name, &dev_page);
1236 retval = copy_mount_options(data, &data_page);
1241 retval = do_mount((char *)dev_page, dir_page, (char *)type_page,
1242 flags, (void *)data_page);
1244 free_page(data_page);
1247 free_page(dev_page);
1251 free_page(type_page);
1256 * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
1257 * It can block. Requires the big lock held.
1259 void set_fs_root(struct fs_struct *fs, struct vfsmount *mnt,
1260 struct dentry *dentry)
1262 struct dentry *old_root;
1263 struct vfsmount *old_rootmnt;
1264 write_lock(&fs->lock);
1265 old_root = fs->root;
1266 old_rootmnt = fs->rootmnt;
1267 fs->rootmnt = mntget(mnt);
1268 fs->root = dget(dentry);
1269 write_unlock(&fs->lock);
1272 mntput(old_rootmnt);
1277 * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
1278 * It can block. Requires the big lock held.
1280 void set_fs_pwd(struct fs_struct *fs, struct vfsmount *mnt,
1281 struct dentry *dentry)
1283 struct dentry *old_pwd;
1284 struct vfsmount *old_pwdmnt;
1286 write_lock(&fs->lock);
1288 old_pwdmnt = fs->pwdmnt;
1289 fs->pwdmnt = mntget(mnt);
1290 fs->pwd = dget(dentry);
1291 write_unlock(&fs->lock);
1299 static void chroot_fs_refs(struct nameidata *old_nd, struct nameidata *new_nd)
1301 struct task_struct *g, *p;
1302 struct fs_struct *fs;
1304 read_lock(&tasklist_lock);
1305 do_each_thread(g, p) {
1309 atomic_inc(&fs->count);
1311 if (fs->root == old_nd->dentry
1312 && fs->rootmnt == old_nd->mnt)
1313 set_fs_root(fs, new_nd->mnt, new_nd->dentry);
1314 if (fs->pwd == old_nd->dentry
1315 && fs->pwdmnt == old_nd->mnt)
1316 set_fs_pwd(fs, new_nd->mnt, new_nd->dentry);
1320 } while_each_thread(g, p);
1321 read_unlock(&tasklist_lock);
1325 * pivot_root Semantics:
1326 * Moves the root file system of the current process to the directory put_old,
1327 * makes new_root as the new root file system of the current process, and sets
1328 * root/cwd of all processes which had them on the current root to new_root.
1331 * The new_root and put_old must be directories, and must not be on the
1332 * same file system as the current process root. The put_old must be
1333 * underneath new_root, i.e. adding a non-zero number of /.. to the string
1334 * pointed to by put_old must yield the same directory as new_root. No other
1335 * file system may be mounted on put_old. After all, new_root is a mountpoint.
1338 * - we don't move root/cwd if they are not at the root (reason: if something
1339 * cared enough to change them, it's probably wrong to force them elsewhere)
1340 * - it's okay to pick a root that isn't the root of a file system, e.g.
1341 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
1342 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
1345 asmlinkage long sys_pivot_root(const char __user * new_root,
1346 const char __user * put_old)
1348 struct vfsmount *tmp;
1349 struct nameidata new_nd, old_nd, parent_nd, root_parent, user_nd;
1352 if (!capable(CAP_SYS_ADMIN))
1357 error = __user_walk(new_root, LOOKUP_FOLLOW | LOOKUP_DIRECTORY,
1362 if (!check_mnt(new_nd.mnt))
1365 error = __user_walk(put_old, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old_nd);
1369 error = security_sb_pivotroot(&old_nd, &new_nd);
1371 path_release(&old_nd);
1375 read_lock(¤t->fs->lock);
1376 user_nd.mnt = mntget(current->fs->rootmnt);
1377 user_nd.dentry = dget(current->fs->root);
1378 read_unlock(¤t->fs->lock);
1379 down_write(¤t->namespace->sem);
1380 down(&old_nd.dentry->d_inode->i_sem);
1382 if (!check_mnt(user_nd.mnt))
1385 if (IS_DEADDIR(new_nd.dentry->d_inode))
1387 if (d_unhashed(new_nd.dentry) && !IS_ROOT(new_nd.dentry))
1389 if (d_unhashed(old_nd.dentry) && !IS_ROOT(old_nd.dentry))
1392 if (new_nd.mnt == user_nd.mnt || old_nd.mnt == user_nd.mnt)
1393 goto out2; /* loop, on the same file system */
1395 if (user_nd.mnt->mnt_root != user_nd.dentry)
1396 goto out2; /* not a mountpoint */
1397 if (user_nd.mnt->mnt_parent == user_nd.mnt)
1398 goto out2; /* not attached */
1399 if (new_nd.mnt->mnt_root != new_nd.dentry)
1400 goto out2; /* not a mountpoint */
1401 if (new_nd.mnt->mnt_parent == new_nd.mnt)
1402 goto out2; /* not attached */
1403 tmp = old_nd.mnt; /* make sure we can reach put_old from new_root */
1404 spin_lock(&vfsmount_lock);
1405 if (tmp != new_nd.mnt) {
1407 if (tmp->mnt_parent == tmp)
1408 goto out3; /* already mounted on put_old */
1409 if (tmp->mnt_parent == new_nd.mnt)
1411 tmp = tmp->mnt_parent;
1413 if (!is_subdir(tmp->mnt_mountpoint, new_nd.dentry))
1415 } else if (!is_subdir(old_nd.dentry, new_nd.dentry))
1417 detach_mnt(new_nd.mnt, &parent_nd);
1418 detach_mnt(user_nd.mnt, &root_parent);
1419 attach_mnt(user_nd.mnt, &old_nd); /* mount old root on put_old */
1420 attach_mnt(new_nd.mnt, &root_parent); /* mount new_root on / */
1421 touch_namespace(current->namespace);
1422 spin_unlock(&vfsmount_lock);
1423 chroot_fs_refs(&user_nd, &new_nd);
1424 security_sb_post_pivotroot(&user_nd, &new_nd);
1426 path_release(&root_parent);
1427 path_release(&parent_nd);
1429 up(&old_nd.dentry->d_inode->i_sem);
1430 up_write(¤t->namespace->sem);
1431 path_release(&user_nd);
1432 path_release(&old_nd);
1434 path_release(&new_nd);
1439 spin_unlock(&vfsmount_lock);
1443 static void __init init_mount_tree(void)
1445 struct vfsmount *mnt;
1446 struct namespace *namespace;
1447 struct task_struct *g, *p;
1449 mnt = do_kern_mount("rootfs", 0, "rootfs", NULL);
1451 panic("Can't create rootfs");
1452 namespace = kmalloc(sizeof(*namespace), GFP_KERNEL);
1454 panic("Can't allocate initial namespace");
1455 atomic_set(&namespace->count, 1);
1456 INIT_LIST_HEAD(&namespace->list);
1457 init_rwsem(&namespace->sem);
1458 init_waitqueue_head(&namespace->poll);
1459 namespace->event = 0;
1460 list_add(&mnt->mnt_list, &namespace->list);
1461 namespace->root = mnt;
1462 mnt->mnt_namespace = namespace;
1464 init_task.namespace = namespace;
1465 read_lock(&tasklist_lock);
1466 do_each_thread(g, p) {
1467 get_namespace(namespace);
1468 p->namespace = namespace;
1469 } while_each_thread(g, p);
1470 read_unlock(&tasklist_lock);
1472 set_fs_pwd(current->fs, namespace->root, namespace->root->mnt_root);
1473 set_fs_root(current->fs, namespace->root, namespace->root->mnt_root);
1476 void __init mnt_init(unsigned long mempages)
1478 struct list_head *d;
1479 unsigned int nr_hash;
1482 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount),
1483 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL, NULL);
1485 mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);
1487 if (!mount_hashtable)
1488 panic("Failed to allocate mount hash table\n");
1491 * Find the power-of-two list-heads that can fit into the allocation..
1492 * We don't guarantee that "sizeof(struct list_head)" is necessarily
1495 nr_hash = PAGE_SIZE / sizeof(struct list_head);
1499 } while ((nr_hash >> hash_bits) != 0);
1503 * Re-calculate the actual number of entries and the mask
1504 * from the number of bits we can fit.
1506 nr_hash = 1UL << hash_bits;
1507 hash_mask = nr_hash - 1;
1509 printk("Mount-cache hash table entries: %d\n", nr_hash);
1511 /* And initialize the newly allocated array */
1512 d = mount_hashtable;
1524 void __put_namespace(struct namespace *namespace)
1526 struct vfsmount *root = namespace->root;
1527 LIST_HEAD(umount_list);
1528 namespace->root = NULL;
1529 spin_unlock(&vfsmount_lock);
1530 down_write(&namespace->sem);
1531 spin_lock(&vfsmount_lock);
1532 umount_tree(root, &umount_list);
1533 spin_unlock(&vfsmount_lock);
1534 up_write(&namespace->sem);
1535 release_mounts(&umount_list);