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/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/kernel.h>
17 #include <linux/acct.h>
18 #include <linux/capability.h>
19 #include <linux/cpumask.h>
20 #include <linux/module.h>
21 #include <linux/sysfs.h>
22 #include <linux/seq_file.h>
23 #include <linux/mnt_namespace.h>
24 #include <linux/namei.h>
25 #include <linux/security.h>
26 #include <linux/mount.h>
27 #include <linux/ramfs.h>
28 #include <linux/log2.h>
29 #include <linux/idr.h>
30 #include <linux/fs_struct.h>
31 #include <asm/uaccess.h>
32 #include <asm/unistd.h>
36 #define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head))
37 #define HASH_SIZE (1UL << HASH_SHIFT)
39 /* spinlock for vfsmount related operations, inplace of dcache_lock */
40 __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock);
43 static DEFINE_IDA(mnt_id_ida);
44 static DEFINE_IDA(mnt_group_ida);
46 static struct list_head *mount_hashtable __read_mostly;
47 static struct kmem_cache *mnt_cache __read_mostly;
48 static struct rw_semaphore namespace_sem;
51 struct kobject *fs_kobj;
52 EXPORT_SYMBOL_GPL(fs_kobj);
54 static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry)
56 unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
57 tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
58 tmp = tmp + (tmp >> HASH_SHIFT);
59 return tmp & (HASH_SIZE - 1);
62 #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16)
64 /* allocation is serialized by namespace_sem */
65 static int mnt_alloc_id(struct vfsmount *mnt)
70 ida_pre_get(&mnt_id_ida, GFP_KERNEL);
71 spin_lock(&vfsmount_lock);
72 res = ida_get_new(&mnt_id_ida, &mnt->mnt_id);
73 spin_unlock(&vfsmount_lock);
80 static void mnt_free_id(struct vfsmount *mnt)
82 spin_lock(&vfsmount_lock);
83 ida_remove(&mnt_id_ida, mnt->mnt_id);
84 spin_unlock(&vfsmount_lock);
88 * Allocate a new peer group ID
90 * mnt_group_ida is protected by namespace_sem
92 static int mnt_alloc_group_id(struct vfsmount *mnt)
94 if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
97 return ida_get_new_above(&mnt_group_ida, 1, &mnt->mnt_group_id);
101 * Release a peer group ID
103 void mnt_release_group_id(struct vfsmount *mnt)
105 ida_remove(&mnt_group_ida, mnt->mnt_group_id);
106 mnt->mnt_group_id = 0;
109 struct vfsmount *alloc_vfsmnt(const char *name)
111 struct vfsmount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
115 err = mnt_alloc_id(mnt);
120 mnt->mnt_devname = kstrdup(name, GFP_KERNEL);
121 if (!mnt->mnt_devname)
125 atomic_set(&mnt->mnt_count, 1);
126 INIT_LIST_HEAD(&mnt->mnt_hash);
127 INIT_LIST_HEAD(&mnt->mnt_child);
128 INIT_LIST_HEAD(&mnt->mnt_mounts);
129 INIT_LIST_HEAD(&mnt->mnt_list);
130 INIT_LIST_HEAD(&mnt->mnt_expire);
131 INIT_LIST_HEAD(&mnt->mnt_share);
132 INIT_LIST_HEAD(&mnt->mnt_slave_list);
133 INIT_LIST_HEAD(&mnt->mnt_slave);
134 atomic_set(&mnt->__mnt_writers, 0);
141 kmem_cache_free(mnt_cache, mnt);
146 * Most r/o checks on a fs are for operations that take
147 * discrete amounts of time, like a write() or unlink().
148 * We must keep track of when those operations start
149 * (for permission checks) and when they end, so that
150 * we can determine when writes are able to occur to
154 * __mnt_is_readonly: check whether a mount is read-only
155 * @mnt: the mount to check for its write status
157 * This shouldn't be used directly ouside of the VFS.
158 * It does not guarantee that the filesystem will stay
159 * r/w, just that it is right *now*. This can not and
160 * should not be used in place of IS_RDONLY(inode).
161 * mnt_want/drop_write() will _keep_ the filesystem
164 int __mnt_is_readonly(struct vfsmount *mnt)
166 if (mnt->mnt_flags & MNT_READONLY)
168 if (mnt->mnt_sb->s_flags & MS_RDONLY)
172 EXPORT_SYMBOL_GPL(__mnt_is_readonly);
176 * If holding multiple instances of this lock, they
177 * must be ordered by cpu number.
180 struct lock_class_key lock_class; /* compiles out with !lockdep */
182 struct vfsmount *mnt;
183 } ____cacheline_aligned_in_smp;
184 static DEFINE_PER_CPU(struct mnt_writer, mnt_writers);
186 static int __init init_mnt_writers(void)
189 for_each_possible_cpu(cpu) {
190 struct mnt_writer *writer = &per_cpu(mnt_writers, cpu);
191 spin_lock_init(&writer->lock);
192 lockdep_set_class(&writer->lock, &writer->lock_class);
197 fs_initcall(init_mnt_writers);
199 static void unlock_mnt_writers(void)
202 struct mnt_writer *cpu_writer;
204 for_each_possible_cpu(cpu) {
205 cpu_writer = &per_cpu(mnt_writers, cpu);
206 spin_unlock(&cpu_writer->lock);
210 static inline void __clear_mnt_count(struct mnt_writer *cpu_writer)
212 if (!cpu_writer->mnt)
215 * This is in case anyone ever leaves an invalid,
216 * old ->mnt and a count of 0.
218 if (!cpu_writer->count)
220 atomic_add(cpu_writer->count, &cpu_writer->mnt->__mnt_writers);
221 cpu_writer->count = 0;
224 * must hold cpu_writer->lock
226 static inline void use_cpu_writer_for_mount(struct mnt_writer *cpu_writer,
227 struct vfsmount *mnt)
229 if (cpu_writer->mnt == mnt)
231 __clear_mnt_count(cpu_writer);
232 cpu_writer->mnt = mnt;
236 * Most r/o checks on a fs are for operations that take
237 * discrete amounts of time, like a write() or unlink().
238 * We must keep track of when those operations start
239 * (for permission checks) and when they end, so that
240 * we can determine when writes are able to occur to
244 * mnt_want_write - get write access to a mount
245 * @mnt: the mount on which to take a write
247 * This tells the low-level filesystem that a write is
248 * about to be performed to it, and makes sure that
249 * writes are allowed before returning success. When
250 * the write operation is finished, mnt_drop_write()
251 * must be called. This is effectively a refcount.
253 int mnt_want_write(struct vfsmount *mnt)
256 struct mnt_writer *cpu_writer;
258 cpu_writer = &get_cpu_var(mnt_writers);
259 spin_lock(&cpu_writer->lock);
260 if (__mnt_is_readonly(mnt)) {
264 use_cpu_writer_for_mount(cpu_writer, mnt);
267 spin_unlock(&cpu_writer->lock);
268 put_cpu_var(mnt_writers);
271 EXPORT_SYMBOL_GPL(mnt_want_write);
273 static void lock_mnt_writers(void)
276 struct mnt_writer *cpu_writer;
278 for_each_possible_cpu(cpu) {
279 cpu_writer = &per_cpu(mnt_writers, cpu);
280 spin_lock(&cpu_writer->lock);
281 __clear_mnt_count(cpu_writer);
282 cpu_writer->mnt = NULL;
287 * These per-cpu write counts are not guaranteed to have
288 * matched increments and decrements on any given cpu.
289 * A file open()ed for write on one cpu and close()d on
290 * another cpu will imbalance this count. Make sure it
291 * does not get too far out of whack.
293 static void handle_write_count_underflow(struct vfsmount *mnt)
295 if (atomic_read(&mnt->__mnt_writers) >=
296 MNT_WRITER_UNDERFLOW_LIMIT)
299 * It isn't necessary to hold all of the locks
300 * at the same time, but doing it this way makes
301 * us share a lot more code.
305 * vfsmount_lock is for mnt_flags.
307 spin_lock(&vfsmount_lock);
309 * If coalescing the per-cpu writer counts did not
310 * get us back to a positive writer count, we have
313 if ((atomic_read(&mnt->__mnt_writers) < 0) &&
314 !(mnt->mnt_flags & MNT_IMBALANCED_WRITE_COUNT)) {
315 WARN(1, KERN_DEBUG "leak detected on mount(%p) writers "
317 mnt, atomic_read(&mnt->__mnt_writers));
318 /* use the flag to keep the dmesg spam down */
319 mnt->mnt_flags |= MNT_IMBALANCED_WRITE_COUNT;
321 spin_unlock(&vfsmount_lock);
322 unlock_mnt_writers();
326 * mnt_drop_write - give up write access to a mount
327 * @mnt: the mount on which to give up write access
329 * Tells the low-level filesystem that we are done
330 * performing writes to it. Must be matched with
331 * mnt_want_write() call above.
333 void mnt_drop_write(struct vfsmount *mnt)
335 int must_check_underflow = 0;
336 struct mnt_writer *cpu_writer;
338 cpu_writer = &get_cpu_var(mnt_writers);
339 spin_lock(&cpu_writer->lock);
341 use_cpu_writer_for_mount(cpu_writer, mnt);
342 if (cpu_writer->count > 0) {
345 must_check_underflow = 1;
346 atomic_dec(&mnt->__mnt_writers);
349 spin_unlock(&cpu_writer->lock);
351 * Logically, we could call this each time,
352 * but the __mnt_writers cacheline tends to
353 * be cold, and makes this expensive.
355 if (must_check_underflow)
356 handle_write_count_underflow(mnt);
358 * This could be done right after the spinlock
359 * is taken because the spinlock keeps us on
360 * the cpu, and disables preemption. However,
361 * putting it here bounds the amount that
362 * __mnt_writers can underflow. Without it,
363 * we could theoretically wrap __mnt_writers.
365 put_cpu_var(mnt_writers);
367 EXPORT_SYMBOL_GPL(mnt_drop_write);
369 static int mnt_make_readonly(struct vfsmount *mnt)
375 * With all the locks held, this value is stable
377 if (atomic_read(&mnt->__mnt_writers) > 0) {
382 * nobody can do a successful mnt_want_write() with all
383 * of the counts in MNT_DENIED_WRITE and the locks held.
385 spin_lock(&vfsmount_lock);
387 mnt->mnt_flags |= MNT_READONLY;
388 spin_unlock(&vfsmount_lock);
390 unlock_mnt_writers();
394 static void __mnt_unmake_readonly(struct vfsmount *mnt)
396 spin_lock(&vfsmount_lock);
397 mnt->mnt_flags &= ~MNT_READONLY;
398 spin_unlock(&vfsmount_lock);
401 void simple_set_mnt(struct vfsmount *mnt, struct super_block *sb)
404 mnt->mnt_root = dget(sb->s_root);
407 EXPORT_SYMBOL(simple_set_mnt);
409 void free_vfsmnt(struct vfsmount *mnt)
411 kfree(mnt->mnt_devname);
413 kmem_cache_free(mnt_cache, mnt);
417 * find the first or last mount at @dentry on vfsmount @mnt depending on
418 * @dir. If @dir is set return the first mount else return the last mount.
420 struct vfsmount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry,
423 struct list_head *head = mount_hashtable + hash(mnt, dentry);
424 struct list_head *tmp = head;
425 struct vfsmount *p, *found = NULL;
428 tmp = dir ? tmp->next : tmp->prev;
432 p = list_entry(tmp, struct vfsmount, mnt_hash);
433 if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) {
442 * lookup_mnt increments the ref count before returning
443 * the vfsmount struct.
445 struct vfsmount *lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
447 struct vfsmount *child_mnt;
448 spin_lock(&vfsmount_lock);
449 if ((child_mnt = __lookup_mnt(mnt, dentry, 1)))
451 spin_unlock(&vfsmount_lock);
455 static inline int check_mnt(struct vfsmount *mnt)
457 return mnt->mnt_ns == current->nsproxy->mnt_ns;
460 static void touch_mnt_namespace(struct mnt_namespace *ns)
464 wake_up_interruptible(&ns->poll);
468 static void __touch_mnt_namespace(struct mnt_namespace *ns)
470 if (ns && ns->event != event) {
472 wake_up_interruptible(&ns->poll);
476 static void detach_mnt(struct vfsmount *mnt, struct path *old_path)
478 old_path->dentry = mnt->mnt_mountpoint;
479 old_path->mnt = mnt->mnt_parent;
480 mnt->mnt_parent = mnt;
481 mnt->mnt_mountpoint = mnt->mnt_root;
482 list_del_init(&mnt->mnt_child);
483 list_del_init(&mnt->mnt_hash);
484 old_path->dentry->d_mounted--;
487 void mnt_set_mountpoint(struct vfsmount *mnt, struct dentry *dentry,
488 struct vfsmount *child_mnt)
490 child_mnt->mnt_parent = mntget(mnt);
491 child_mnt->mnt_mountpoint = dget(dentry);
495 static void attach_mnt(struct vfsmount *mnt, struct path *path)
497 mnt_set_mountpoint(path->mnt, path->dentry, mnt);
498 list_add_tail(&mnt->mnt_hash, mount_hashtable +
499 hash(path->mnt, path->dentry));
500 list_add_tail(&mnt->mnt_child, &path->mnt->mnt_mounts);
504 * the caller must hold vfsmount_lock
506 static void commit_tree(struct vfsmount *mnt)
508 struct vfsmount *parent = mnt->mnt_parent;
511 struct mnt_namespace *n = parent->mnt_ns;
513 BUG_ON(parent == mnt);
515 list_add_tail(&head, &mnt->mnt_list);
516 list_for_each_entry(m, &head, mnt_list)
518 list_splice(&head, n->list.prev);
520 list_add_tail(&mnt->mnt_hash, mount_hashtable +
521 hash(parent, mnt->mnt_mountpoint));
522 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
523 touch_mnt_namespace(n);
526 static struct vfsmount *next_mnt(struct vfsmount *p, struct vfsmount *root)
528 struct list_head *next = p->mnt_mounts.next;
529 if (next == &p->mnt_mounts) {
533 next = p->mnt_child.next;
534 if (next != &p->mnt_parent->mnt_mounts)
539 return list_entry(next, struct vfsmount, mnt_child);
542 static struct vfsmount *skip_mnt_tree(struct vfsmount *p)
544 struct list_head *prev = p->mnt_mounts.prev;
545 while (prev != &p->mnt_mounts) {
546 p = list_entry(prev, struct vfsmount, mnt_child);
547 prev = p->mnt_mounts.prev;
552 static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root,
555 struct super_block *sb = old->mnt_sb;
556 struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname);
559 if (flag & (CL_SLAVE | CL_PRIVATE))
560 mnt->mnt_group_id = 0; /* not a peer of original */
562 mnt->mnt_group_id = old->mnt_group_id;
564 if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
565 int err = mnt_alloc_group_id(mnt);
570 mnt->mnt_flags = old->mnt_flags;
571 atomic_inc(&sb->s_active);
573 mnt->mnt_root = dget(root);
574 mnt->mnt_mountpoint = mnt->mnt_root;
575 mnt->mnt_parent = mnt;
577 if (flag & CL_SLAVE) {
578 list_add(&mnt->mnt_slave, &old->mnt_slave_list);
579 mnt->mnt_master = old;
580 CLEAR_MNT_SHARED(mnt);
581 } else if (!(flag & CL_PRIVATE)) {
582 if ((flag & CL_PROPAGATION) || IS_MNT_SHARED(old))
583 list_add(&mnt->mnt_share, &old->mnt_share);
584 if (IS_MNT_SLAVE(old))
585 list_add(&mnt->mnt_slave, &old->mnt_slave);
586 mnt->mnt_master = old->mnt_master;
588 if (flag & CL_MAKE_SHARED)
591 /* stick the duplicate mount on the same expiry list
592 * as the original if that was on one */
593 if (flag & CL_EXPIRE) {
594 if (!list_empty(&old->mnt_expire))
595 list_add(&mnt->mnt_expire, &old->mnt_expire);
605 static inline void __mntput(struct vfsmount *mnt)
608 struct super_block *sb = mnt->mnt_sb;
610 * We don't have to hold all of the locks at the
611 * same time here because we know that we're the
612 * last reference to mnt and that no new writers
615 for_each_possible_cpu(cpu) {
616 struct mnt_writer *cpu_writer = &per_cpu(mnt_writers, cpu);
617 spin_lock(&cpu_writer->lock);
618 if (cpu_writer->mnt != mnt) {
619 spin_unlock(&cpu_writer->lock);
622 atomic_add(cpu_writer->count, &mnt->__mnt_writers);
623 cpu_writer->count = 0;
625 * Might as well do this so that no one
626 * ever sees the pointer and expects
629 cpu_writer->mnt = NULL;
630 spin_unlock(&cpu_writer->lock);
633 * This probably indicates that somebody messed
634 * up a mnt_want/drop_write() pair. If this
635 * happens, the filesystem was probably unable
636 * to make r/w->r/o transitions.
638 WARN_ON(atomic_read(&mnt->__mnt_writers));
641 deactivate_super(sb);
644 void mntput_no_expire(struct vfsmount *mnt)
647 if (atomic_dec_and_lock(&mnt->mnt_count, &vfsmount_lock)) {
648 if (likely(!mnt->mnt_pinned)) {
649 spin_unlock(&vfsmount_lock);
653 atomic_add(mnt->mnt_pinned + 1, &mnt->mnt_count);
655 spin_unlock(&vfsmount_lock);
656 acct_auto_close_mnt(mnt);
657 security_sb_umount_close(mnt);
662 EXPORT_SYMBOL(mntput_no_expire);
664 void mnt_pin(struct vfsmount *mnt)
666 spin_lock(&vfsmount_lock);
668 spin_unlock(&vfsmount_lock);
671 EXPORT_SYMBOL(mnt_pin);
673 void mnt_unpin(struct vfsmount *mnt)
675 spin_lock(&vfsmount_lock);
676 if (mnt->mnt_pinned) {
677 atomic_inc(&mnt->mnt_count);
680 spin_unlock(&vfsmount_lock);
683 EXPORT_SYMBOL(mnt_unpin);
685 static inline void mangle(struct seq_file *m, const char *s)
687 seq_escape(m, s, " \t\n\\");
691 * Simple .show_options callback for filesystems which don't want to
692 * implement more complex mount option showing.
694 * See also save_mount_options().
696 int generic_show_options(struct seq_file *m, struct vfsmount *mnt)
698 const char *options = mnt->mnt_sb->s_options;
700 if (options != NULL && options[0]) {
707 EXPORT_SYMBOL(generic_show_options);
710 * If filesystem uses generic_show_options(), this function should be
711 * called from the fill_super() callback.
713 * The .remount_fs callback usually needs to be handled in a special
714 * way, to make sure, that previous options are not overwritten if the
717 * Also note, that if the filesystem's .remount_fs function doesn't
718 * reset all options to their default value, but changes only newly
719 * given options, then the displayed options will not reflect reality
722 void save_mount_options(struct super_block *sb, char *options)
724 kfree(sb->s_options);
725 sb->s_options = kstrdup(options, GFP_KERNEL);
727 EXPORT_SYMBOL(save_mount_options);
729 #ifdef CONFIG_PROC_FS
731 static void *m_start(struct seq_file *m, loff_t *pos)
733 struct proc_mounts *p = m->private;
735 down_read(&namespace_sem);
736 return seq_list_start(&p->ns->list, *pos);
739 static void *m_next(struct seq_file *m, void *v, loff_t *pos)
741 struct proc_mounts *p = m->private;
743 return seq_list_next(v, &p->ns->list, pos);
746 static void m_stop(struct seq_file *m, void *v)
748 up_read(&namespace_sem);
751 struct proc_fs_info {
756 static int show_sb_opts(struct seq_file *m, struct super_block *sb)
758 static const struct proc_fs_info fs_info[] = {
759 { MS_SYNCHRONOUS, ",sync" },
760 { MS_DIRSYNC, ",dirsync" },
761 { MS_MANDLOCK, ",mand" },
764 const struct proc_fs_info *fs_infop;
766 for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
767 if (sb->s_flags & fs_infop->flag)
768 seq_puts(m, fs_infop->str);
771 return security_sb_show_options(m, sb);
774 static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt)
776 static const struct proc_fs_info mnt_info[] = {
777 { MNT_NOSUID, ",nosuid" },
778 { MNT_NODEV, ",nodev" },
779 { MNT_NOEXEC, ",noexec" },
780 { MNT_NOATIME, ",noatime" },
781 { MNT_NODIRATIME, ",nodiratime" },
782 { MNT_RELATIME, ",relatime" },
783 { MNT_STRICTATIME, ",strictatime" },
786 const struct proc_fs_info *fs_infop;
788 for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {
789 if (mnt->mnt_flags & fs_infop->flag)
790 seq_puts(m, fs_infop->str);
794 static void show_type(struct seq_file *m, struct super_block *sb)
796 mangle(m, sb->s_type->name);
797 if (sb->s_subtype && sb->s_subtype[0]) {
799 mangle(m, sb->s_subtype);
803 static int show_vfsmnt(struct seq_file *m, void *v)
805 struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);
807 struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
809 mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
811 seq_path(m, &mnt_path, " \t\n\\");
813 show_type(m, mnt->mnt_sb);
814 seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw");
815 err = show_sb_opts(m, mnt->mnt_sb);
818 show_mnt_opts(m, mnt);
819 if (mnt->mnt_sb->s_op->show_options)
820 err = mnt->mnt_sb->s_op->show_options(m, mnt);
821 seq_puts(m, " 0 0\n");
826 const struct seq_operations mounts_op = {
833 static int show_mountinfo(struct seq_file *m, void *v)
835 struct proc_mounts *p = m->private;
836 struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);
837 struct super_block *sb = mnt->mnt_sb;
838 struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
839 struct path root = p->root;
842 seq_printf(m, "%i %i %u:%u ", mnt->mnt_id, mnt->mnt_parent->mnt_id,
843 MAJOR(sb->s_dev), MINOR(sb->s_dev));
844 seq_dentry(m, mnt->mnt_root, " \t\n\\");
846 seq_path_root(m, &mnt_path, &root, " \t\n\\");
847 if (root.mnt != p->root.mnt || root.dentry != p->root.dentry) {
849 * Mountpoint is outside root, discard that one. Ugly,
850 * but less so than trying to do that in iterator in a
851 * race-free way (due to renames).
855 seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw");
856 show_mnt_opts(m, mnt);
858 /* Tagged fields ("foo:X" or "bar") */
859 if (IS_MNT_SHARED(mnt))
860 seq_printf(m, " shared:%i", mnt->mnt_group_id);
861 if (IS_MNT_SLAVE(mnt)) {
862 int master = mnt->mnt_master->mnt_group_id;
863 int dom = get_dominating_id(mnt, &p->root);
864 seq_printf(m, " master:%i", master);
865 if (dom && dom != master)
866 seq_printf(m, " propagate_from:%i", dom);
868 if (IS_MNT_UNBINDABLE(mnt))
869 seq_puts(m, " unbindable");
871 /* Filesystem specific data */
875 mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
876 seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw");
877 err = show_sb_opts(m, sb);
880 if (sb->s_op->show_options)
881 err = sb->s_op->show_options(m, mnt);
887 const struct seq_operations mountinfo_op = {
891 .show = show_mountinfo,
894 static int show_vfsstat(struct seq_file *m, void *v)
896 struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);
897 struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
901 if (mnt->mnt_devname) {
902 seq_puts(m, "device ");
903 mangle(m, mnt->mnt_devname);
905 seq_puts(m, "no device");
908 seq_puts(m, " mounted on ");
909 seq_path(m, &mnt_path, " \t\n\\");
912 /* file system type */
913 seq_puts(m, "with fstype ");
914 show_type(m, mnt->mnt_sb);
916 /* optional statistics */
917 if (mnt->mnt_sb->s_op->show_stats) {
919 err = mnt->mnt_sb->s_op->show_stats(m, mnt);
926 const struct seq_operations mountstats_op = {
930 .show = show_vfsstat,
932 #endif /* CONFIG_PROC_FS */
935 * may_umount_tree - check if a mount tree is busy
936 * @mnt: root of mount tree
938 * This is called to check if a tree of mounts has any
939 * open files, pwds, chroots or sub mounts that are
942 int may_umount_tree(struct vfsmount *mnt)
945 int minimum_refs = 0;
948 spin_lock(&vfsmount_lock);
949 for (p = mnt; p; p = next_mnt(p, mnt)) {
950 actual_refs += atomic_read(&p->mnt_count);
953 spin_unlock(&vfsmount_lock);
955 if (actual_refs > minimum_refs)
961 EXPORT_SYMBOL(may_umount_tree);
964 * may_umount - check if a mount point is busy
965 * @mnt: root of mount
967 * This is called to check if a mount point has any
968 * open files, pwds, chroots or sub mounts. If the
969 * mount has sub mounts this will return busy
970 * regardless of whether the sub mounts are busy.
972 * Doesn't take quota and stuff into account. IOW, in some cases it will
973 * give false negatives. The main reason why it's here is that we need
974 * a non-destructive way to look for easily umountable filesystems.
976 int may_umount(struct vfsmount *mnt)
979 spin_lock(&vfsmount_lock);
980 if (propagate_mount_busy(mnt, 2))
982 spin_unlock(&vfsmount_lock);
986 EXPORT_SYMBOL(may_umount);
988 void release_mounts(struct list_head *head)
990 struct vfsmount *mnt;
991 while (!list_empty(head)) {
992 mnt = list_first_entry(head, struct vfsmount, mnt_hash);
993 list_del_init(&mnt->mnt_hash);
994 if (mnt->mnt_parent != mnt) {
995 struct dentry *dentry;
997 spin_lock(&vfsmount_lock);
998 dentry = mnt->mnt_mountpoint;
1000 mnt->mnt_mountpoint = mnt->mnt_root;
1001 mnt->mnt_parent = mnt;
1003 spin_unlock(&vfsmount_lock);
1011 void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill)
1015 for (p = mnt; p; p = next_mnt(p, mnt))
1016 list_move(&p->mnt_hash, kill);
1019 propagate_umount(kill);
1021 list_for_each_entry(p, kill, mnt_hash) {
1022 list_del_init(&p->mnt_expire);
1023 list_del_init(&p->mnt_list);
1024 __touch_mnt_namespace(p->mnt_ns);
1026 list_del_init(&p->mnt_child);
1027 if (p->mnt_parent != p) {
1028 p->mnt_parent->mnt_ghosts++;
1029 p->mnt_mountpoint->d_mounted--;
1031 change_mnt_propagation(p, MS_PRIVATE);
1035 static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts);
1037 static int do_umount(struct vfsmount *mnt, int flags)
1039 struct super_block *sb = mnt->mnt_sb;
1041 LIST_HEAD(umount_list);
1043 retval = security_sb_umount(mnt, flags);
1048 * Allow userspace to request a mountpoint be expired rather than
1049 * unmounting unconditionally. Unmount only happens if:
1050 * (1) the mark is already set (the mark is cleared by mntput())
1051 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1053 if (flags & MNT_EXPIRE) {
1054 if (mnt == current->fs->root.mnt ||
1055 flags & (MNT_FORCE | MNT_DETACH))
1058 if (atomic_read(&mnt->mnt_count) != 2)
1061 if (!xchg(&mnt->mnt_expiry_mark, 1))
1066 * If we may have to abort operations to get out of this
1067 * mount, and they will themselves hold resources we must
1068 * allow the fs to do things. In the Unix tradition of
1069 * 'Gee thats tricky lets do it in userspace' the umount_begin
1070 * might fail to complete on the first run through as other tasks
1071 * must return, and the like. Thats for the mount program to worry
1072 * about for the moment.
1075 if (flags & MNT_FORCE && sb->s_op->umount_begin) {
1077 sb->s_op->umount_begin(sb);
1082 * No sense to grab the lock for this test, but test itself looks
1083 * somewhat bogus. Suggestions for better replacement?
1084 * Ho-hum... In principle, we might treat that as umount + switch
1085 * to rootfs. GC would eventually take care of the old vfsmount.
1086 * Actually it makes sense, especially if rootfs would contain a
1087 * /reboot - static binary that would close all descriptors and
1088 * call reboot(9). Then init(8) could umount root and exec /reboot.
1090 if (mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
1092 * Special case for "unmounting" root ...
1093 * we just try to remount it readonly.
1095 down_write(&sb->s_umount);
1096 if (!(sb->s_flags & MS_RDONLY)) {
1098 retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
1101 up_write(&sb->s_umount);
1105 down_write(&namespace_sem);
1106 spin_lock(&vfsmount_lock);
1109 if (!(flags & MNT_DETACH))
1110 shrink_submounts(mnt, &umount_list);
1113 if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) {
1114 if (!list_empty(&mnt->mnt_list))
1115 umount_tree(mnt, 1, &umount_list);
1118 spin_unlock(&vfsmount_lock);
1120 security_sb_umount_busy(mnt);
1121 up_write(&namespace_sem);
1122 release_mounts(&umount_list);
1127 * Now umount can handle mount points as well as block devices.
1128 * This is important for filesystems which use unnamed block devices.
1130 * We now support a flag for forced unmount like the other 'big iron'
1131 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1134 SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
1139 retval = user_path(name, &path);
1143 if (path.dentry != path.mnt->mnt_root)
1145 if (!check_mnt(path.mnt))
1149 if (!capable(CAP_SYS_ADMIN))
1152 retval = do_umount(path.mnt, flags);
1154 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1156 mntput_no_expire(path.mnt);
1161 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1164 * The 2.0 compatible umount. No flags.
1166 SYSCALL_DEFINE1(oldumount, char __user *, name)
1168 return sys_umount(name, 0);
1173 static int mount_is_safe(struct path *path)
1175 if (capable(CAP_SYS_ADMIN))
1179 if (S_ISLNK(path->dentry->d_inode->i_mode))
1181 if (path->dentry->d_inode->i_mode & S_ISVTX) {
1182 if (current_uid() != path->dentry->d_inode->i_uid)
1185 if (inode_permission(path->dentry->d_inode, MAY_WRITE))
1191 struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry,
1194 struct vfsmount *res, *p, *q, *r, *s;
1197 if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt))
1200 res = q = clone_mnt(mnt, dentry, flag);
1203 q->mnt_mountpoint = mnt->mnt_mountpoint;
1206 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
1207 if (!is_subdir(r->mnt_mountpoint, dentry))
1210 for (s = r; s; s = next_mnt(s, r)) {
1211 if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) {
1212 s = skip_mnt_tree(s);
1215 while (p != s->mnt_parent) {
1221 path.dentry = p->mnt_mountpoint;
1222 q = clone_mnt(p, p->mnt_root, flag);
1225 spin_lock(&vfsmount_lock);
1226 list_add_tail(&q->mnt_list, &res->mnt_list);
1227 attach_mnt(q, &path);
1228 spin_unlock(&vfsmount_lock);
1234 LIST_HEAD(umount_list);
1235 spin_lock(&vfsmount_lock);
1236 umount_tree(res, 0, &umount_list);
1237 spin_unlock(&vfsmount_lock);
1238 release_mounts(&umount_list);
1243 struct vfsmount *collect_mounts(struct vfsmount *mnt, struct dentry *dentry)
1245 struct vfsmount *tree;
1246 down_write(&namespace_sem);
1247 tree = copy_tree(mnt, dentry, CL_COPY_ALL | CL_PRIVATE);
1248 up_write(&namespace_sem);
1252 void drop_collected_mounts(struct vfsmount *mnt)
1254 LIST_HEAD(umount_list);
1255 down_write(&namespace_sem);
1256 spin_lock(&vfsmount_lock);
1257 umount_tree(mnt, 0, &umount_list);
1258 spin_unlock(&vfsmount_lock);
1259 up_write(&namespace_sem);
1260 release_mounts(&umount_list);
1263 static void cleanup_group_ids(struct vfsmount *mnt, struct vfsmount *end)
1267 for (p = mnt; p != end; p = next_mnt(p, mnt)) {
1268 if (p->mnt_group_id && !IS_MNT_SHARED(p))
1269 mnt_release_group_id(p);
1273 static int invent_group_ids(struct vfsmount *mnt, bool recurse)
1277 for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
1278 if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
1279 int err = mnt_alloc_group_id(p);
1281 cleanup_group_ids(mnt, p);
1291 * @source_mnt : mount tree to be attached
1292 * @nd : place the mount tree @source_mnt is attached
1293 * @parent_nd : if non-null, detach the source_mnt from its parent and
1294 * store the parent mount and mountpoint dentry.
1295 * (done when source_mnt is moved)
1297 * NOTE: in the table below explains the semantics when a source mount
1298 * of a given type is attached to a destination mount of a given type.
1299 * ---------------------------------------------------------------------------
1300 * | BIND MOUNT OPERATION |
1301 * |**************************************************************************
1302 * | source-->| shared | private | slave | unbindable |
1306 * |**************************************************************************
1307 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1309 * |non-shared| shared (+) | private | slave (*) | invalid |
1310 * ***************************************************************************
1311 * A bind operation clones the source mount and mounts the clone on the
1312 * destination mount.
1314 * (++) the cloned mount is propagated to all the mounts in the propagation
1315 * tree of the destination mount and the cloned mount is added to
1316 * the peer group of the source mount.
1317 * (+) the cloned mount is created under the destination mount and is marked
1318 * as shared. The cloned mount is added to the peer group of the source
1320 * (+++) the mount is propagated to all the mounts in the propagation tree
1321 * of the destination mount and the cloned mount is made slave
1322 * of the same master as that of the source mount. The cloned mount
1323 * is marked as 'shared and slave'.
1324 * (*) the cloned mount is made a slave of the same master as that of the
1327 * ---------------------------------------------------------------------------
1328 * | MOVE MOUNT OPERATION |
1329 * |**************************************************************************
1330 * | source-->| shared | private | slave | unbindable |
1334 * |**************************************************************************
1335 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
1337 * |non-shared| shared (+*) | private | slave (*) | unbindable |
1338 * ***************************************************************************
1340 * (+) the mount is moved to the destination. And is then propagated to
1341 * all the mounts in the propagation tree of the destination mount.
1342 * (+*) the mount is moved to the destination.
1343 * (+++) the mount is moved to the destination and is then propagated to
1344 * all the mounts belonging to the destination mount's propagation tree.
1345 * the mount is marked as 'shared and slave'.
1346 * (*) the mount continues to be a slave at the new location.
1348 * if the source mount is a tree, the operations explained above is
1349 * applied to each mount in the tree.
1350 * Must be called without spinlocks held, since this function can sleep
1353 static int attach_recursive_mnt(struct vfsmount *source_mnt,
1354 struct path *path, struct path *parent_path)
1356 LIST_HEAD(tree_list);
1357 struct vfsmount *dest_mnt = path->mnt;
1358 struct dentry *dest_dentry = path->dentry;
1359 struct vfsmount *child, *p;
1362 if (IS_MNT_SHARED(dest_mnt)) {
1363 err = invent_group_ids(source_mnt, true);
1367 err = propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list);
1369 goto out_cleanup_ids;
1371 if (IS_MNT_SHARED(dest_mnt)) {
1372 for (p = source_mnt; p; p = next_mnt(p, source_mnt))
1376 spin_lock(&vfsmount_lock);
1378 detach_mnt(source_mnt, parent_path);
1379 attach_mnt(source_mnt, path);
1380 touch_mnt_namespace(current->nsproxy->mnt_ns);
1382 mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt);
1383 commit_tree(source_mnt);
1386 list_for_each_entry_safe(child, p, &tree_list, mnt_hash) {
1387 list_del_init(&child->mnt_hash);
1390 spin_unlock(&vfsmount_lock);
1394 if (IS_MNT_SHARED(dest_mnt))
1395 cleanup_group_ids(source_mnt, NULL);
1400 static int graft_tree(struct vfsmount *mnt, struct path *path)
1403 if (mnt->mnt_sb->s_flags & MS_NOUSER)
1406 if (S_ISDIR(path->dentry->d_inode->i_mode) !=
1407 S_ISDIR(mnt->mnt_root->d_inode->i_mode))
1411 mutex_lock(&path->dentry->d_inode->i_mutex);
1412 if (IS_DEADDIR(path->dentry->d_inode))
1415 err = security_sb_check_sb(mnt, path);
1420 if (IS_ROOT(path->dentry) || !d_unhashed(path->dentry))
1421 err = attach_recursive_mnt(mnt, path, NULL);
1423 mutex_unlock(&path->dentry->d_inode->i_mutex);
1425 security_sb_post_addmount(mnt, path);
1430 * recursively change the type of the mountpoint.
1432 static int do_change_type(struct path *path, int flag)
1434 struct vfsmount *m, *mnt = path->mnt;
1435 int recurse = flag & MS_REC;
1436 int type = flag & ~MS_REC;
1439 if (!capable(CAP_SYS_ADMIN))
1442 if (path->dentry != path->mnt->mnt_root)
1445 down_write(&namespace_sem);
1446 if (type == MS_SHARED) {
1447 err = invent_group_ids(mnt, recurse);
1452 spin_lock(&vfsmount_lock);
1453 for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
1454 change_mnt_propagation(m, type);
1455 spin_unlock(&vfsmount_lock);
1458 up_write(&namespace_sem);
1463 * do loopback mount.
1465 static int do_loopback(struct path *path, char *old_name,
1468 struct path old_path;
1469 struct vfsmount *mnt = NULL;
1470 int err = mount_is_safe(path);
1473 if (!old_name || !*old_name)
1475 err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
1479 down_write(&namespace_sem);
1481 if (IS_MNT_UNBINDABLE(old_path.mnt))
1484 if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt))
1489 mnt = copy_tree(old_path.mnt, old_path.dentry, 0);
1491 mnt = clone_mnt(old_path.mnt, old_path.dentry, 0);
1496 err = graft_tree(mnt, path);
1498 LIST_HEAD(umount_list);
1499 spin_lock(&vfsmount_lock);
1500 umount_tree(mnt, 0, &umount_list);
1501 spin_unlock(&vfsmount_lock);
1502 release_mounts(&umount_list);
1506 up_write(&namespace_sem);
1507 path_put(&old_path);
1511 static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
1514 int readonly_request = 0;
1516 if (ms_flags & MS_RDONLY)
1517 readonly_request = 1;
1518 if (readonly_request == __mnt_is_readonly(mnt))
1521 if (readonly_request)
1522 error = mnt_make_readonly(mnt);
1524 __mnt_unmake_readonly(mnt);
1529 * change filesystem flags. dir should be a physical root of filesystem.
1530 * If you've mounted a non-root directory somewhere and want to do remount
1531 * on it - tough luck.
1533 static int do_remount(struct path *path, int flags, int mnt_flags,
1537 struct super_block *sb = path->mnt->mnt_sb;
1539 if (!capable(CAP_SYS_ADMIN))
1542 if (!check_mnt(path->mnt))
1545 if (path->dentry != path->mnt->mnt_root)
1548 down_write(&sb->s_umount);
1549 if (flags & MS_BIND)
1550 err = change_mount_flags(path->mnt, flags);
1552 err = do_remount_sb(sb, flags, data, 0);
1554 path->mnt->mnt_flags = mnt_flags;
1555 up_write(&sb->s_umount);
1557 security_sb_post_remount(path->mnt, flags, data);
1559 spin_lock(&vfsmount_lock);
1560 touch_mnt_namespace(path->mnt->mnt_ns);
1561 spin_unlock(&vfsmount_lock);
1566 static inline int tree_contains_unbindable(struct vfsmount *mnt)
1569 for (p = mnt; p; p = next_mnt(p, mnt)) {
1570 if (IS_MNT_UNBINDABLE(p))
1576 static int do_move_mount(struct path *path, char *old_name)
1578 struct path old_path, parent_path;
1581 if (!capable(CAP_SYS_ADMIN))
1583 if (!old_name || !*old_name)
1585 err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
1589 down_write(&namespace_sem);
1590 while (d_mountpoint(path->dentry) &&
1591 follow_down(&path->mnt, &path->dentry))
1594 if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt))
1598 mutex_lock(&path->dentry->d_inode->i_mutex);
1599 if (IS_DEADDIR(path->dentry->d_inode))
1602 if (!IS_ROOT(path->dentry) && d_unhashed(path->dentry))
1606 if (old_path.dentry != old_path.mnt->mnt_root)
1609 if (old_path.mnt == old_path.mnt->mnt_parent)
1612 if (S_ISDIR(path->dentry->d_inode->i_mode) !=
1613 S_ISDIR(old_path.dentry->d_inode->i_mode))
1616 * Don't move a mount residing in a shared parent.
1618 if (old_path.mnt->mnt_parent &&
1619 IS_MNT_SHARED(old_path.mnt->mnt_parent))
1622 * Don't move a mount tree containing unbindable mounts to a destination
1623 * mount which is shared.
1625 if (IS_MNT_SHARED(path->mnt) &&
1626 tree_contains_unbindable(old_path.mnt))
1629 for (p = path->mnt; p->mnt_parent != p; p = p->mnt_parent)
1630 if (p == old_path.mnt)
1633 err = attach_recursive_mnt(old_path.mnt, path, &parent_path);
1637 /* if the mount is moved, it should no longer be expire
1639 list_del_init(&old_path.mnt->mnt_expire);
1641 mutex_unlock(&path->dentry->d_inode->i_mutex);
1643 up_write(&namespace_sem);
1645 path_put(&parent_path);
1646 path_put(&old_path);
1651 * create a new mount for userspace and request it to be added into the
1654 static int do_new_mount(struct path *path, char *type, int flags,
1655 int mnt_flags, char *name, void *data)
1657 struct vfsmount *mnt;
1659 if (!type || !memchr(type, 0, PAGE_SIZE))
1662 /* we need capabilities... */
1663 if (!capable(CAP_SYS_ADMIN))
1666 mnt = do_kern_mount(type, flags, name, data);
1668 return PTR_ERR(mnt);
1670 return do_add_mount(mnt, path, mnt_flags, NULL);
1674 * add a mount into a namespace's mount tree
1675 * - provide the option of adding the new mount to an expiration list
1677 int do_add_mount(struct vfsmount *newmnt, struct path *path,
1678 int mnt_flags, struct list_head *fslist)
1682 down_write(&namespace_sem);
1683 /* Something was mounted here while we slept */
1684 while (d_mountpoint(path->dentry) &&
1685 follow_down(&path->mnt, &path->dentry))
1688 if (!check_mnt(path->mnt))
1691 /* Refuse the same filesystem on the same mount point */
1693 if (path->mnt->mnt_sb == newmnt->mnt_sb &&
1694 path->mnt->mnt_root == path->dentry)
1698 if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode))
1701 newmnt->mnt_flags = mnt_flags;
1702 if ((err = graft_tree(newmnt, path)))
1705 if (fslist) /* add to the specified expiration list */
1706 list_add_tail(&newmnt->mnt_expire, fslist);
1708 up_write(&namespace_sem);
1712 up_write(&namespace_sem);
1717 EXPORT_SYMBOL_GPL(do_add_mount);
1720 * process a list of expirable mountpoints with the intent of discarding any
1721 * mountpoints that aren't in use and haven't been touched since last we came
1724 void mark_mounts_for_expiry(struct list_head *mounts)
1726 struct vfsmount *mnt, *next;
1727 LIST_HEAD(graveyard);
1730 if (list_empty(mounts))
1733 down_write(&namespace_sem);
1734 spin_lock(&vfsmount_lock);
1736 /* extract from the expiration list every vfsmount that matches the
1737 * following criteria:
1738 * - only referenced by its parent vfsmount
1739 * - still marked for expiry (marked on the last call here; marks are
1740 * cleared by mntput())
1742 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
1743 if (!xchg(&mnt->mnt_expiry_mark, 1) ||
1744 propagate_mount_busy(mnt, 1))
1746 list_move(&mnt->mnt_expire, &graveyard);
1748 while (!list_empty(&graveyard)) {
1749 mnt = list_first_entry(&graveyard, struct vfsmount, mnt_expire);
1750 touch_mnt_namespace(mnt->mnt_ns);
1751 umount_tree(mnt, 1, &umounts);
1753 spin_unlock(&vfsmount_lock);
1754 up_write(&namespace_sem);
1756 release_mounts(&umounts);
1759 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
1762 * Ripoff of 'select_parent()'
1764 * search the list of submounts for a given mountpoint, and move any
1765 * shrinkable submounts to the 'graveyard' list.
1767 static int select_submounts(struct vfsmount *parent, struct list_head *graveyard)
1769 struct vfsmount *this_parent = parent;
1770 struct list_head *next;
1774 next = this_parent->mnt_mounts.next;
1776 while (next != &this_parent->mnt_mounts) {
1777 struct list_head *tmp = next;
1778 struct vfsmount *mnt = list_entry(tmp, struct vfsmount, mnt_child);
1781 if (!(mnt->mnt_flags & MNT_SHRINKABLE))
1784 * Descend a level if the d_mounts list is non-empty.
1786 if (!list_empty(&mnt->mnt_mounts)) {
1791 if (!propagate_mount_busy(mnt, 1)) {
1792 list_move_tail(&mnt->mnt_expire, graveyard);
1797 * All done at this level ... ascend and resume the search
1799 if (this_parent != parent) {
1800 next = this_parent->mnt_child.next;
1801 this_parent = this_parent->mnt_parent;
1808 * process a list of expirable mountpoints with the intent of discarding any
1809 * submounts of a specific parent mountpoint
1811 static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts)
1813 LIST_HEAD(graveyard);
1816 /* extract submounts of 'mountpoint' from the expiration list */
1817 while (select_submounts(mnt, &graveyard)) {
1818 while (!list_empty(&graveyard)) {
1819 m = list_first_entry(&graveyard, struct vfsmount,
1821 touch_mnt_namespace(m->mnt_ns);
1822 umount_tree(m, 1, umounts);
1828 * Some copy_from_user() implementations do not return the exact number of
1829 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
1830 * Note that this function differs from copy_from_user() in that it will oops
1831 * on bad values of `to', rather than returning a short copy.
1833 static long exact_copy_from_user(void *to, const void __user * from,
1837 const char __user *f = from;
1840 if (!access_ok(VERIFY_READ, from, n))
1844 if (__get_user(c, f)) {
1855 int copy_mount_options(const void __user * data, unsigned long *where)
1865 if (!(page = __get_free_page(GFP_KERNEL)))
1868 /* We only care that *some* data at the address the user
1869 * gave us is valid. Just in case, we'll zero
1870 * the remainder of the page.
1872 /* copy_from_user cannot cross TASK_SIZE ! */
1873 size = TASK_SIZE - (unsigned long)data;
1874 if (size > PAGE_SIZE)
1877 i = size - exact_copy_from_user((void *)page, data, size);
1883 memset((char *)page + i, 0, PAGE_SIZE - i);
1889 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
1890 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
1892 * data is a (void *) that can point to any structure up to
1893 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
1894 * information (or be NULL).
1896 * Pre-0.97 versions of mount() didn't have a flags word.
1897 * When the flags word was introduced its top half was required
1898 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
1899 * Therefore, if this magic number is present, it carries no information
1900 * and must be discarded.
1902 long do_mount(char *dev_name, char *dir_name, char *type_page,
1903 unsigned long flags, void *data_page)
1910 if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
1911 flags &= ~MS_MGC_MSK;
1913 /* Basic sanity checks */
1915 if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE))
1917 if (dev_name && !memchr(dev_name, 0, PAGE_SIZE))
1921 ((char *)data_page)[PAGE_SIZE - 1] = 0;
1923 /* Default to relatime */
1924 mnt_flags |= MNT_RELATIME;
1926 /* Separate the per-mountpoint flags */
1927 if (flags & MS_NOSUID)
1928 mnt_flags |= MNT_NOSUID;
1929 if (flags & MS_NODEV)
1930 mnt_flags |= MNT_NODEV;
1931 if (flags & MS_NOEXEC)
1932 mnt_flags |= MNT_NOEXEC;
1933 if (flags & MS_NOATIME)
1934 mnt_flags |= MNT_NOATIME;
1935 if (flags & MS_NODIRATIME)
1936 mnt_flags |= MNT_NODIRATIME;
1937 if (flags & MS_STRICTATIME)
1938 mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
1939 if (flags & MS_RDONLY)
1940 mnt_flags |= MNT_READONLY;
1942 flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE |
1943 MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
1946 /* ... and get the mountpoint */
1947 retval = kern_path(dir_name, LOOKUP_FOLLOW, &path);
1951 retval = security_sb_mount(dev_name, &path,
1952 type_page, flags, data_page);
1956 if (flags & MS_REMOUNT)
1957 retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
1959 else if (flags & MS_BIND)
1960 retval = do_loopback(&path, dev_name, flags & MS_REC);
1961 else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
1962 retval = do_change_type(&path, flags);
1963 else if (flags & MS_MOVE)
1964 retval = do_move_mount(&path, dev_name);
1966 retval = do_new_mount(&path, type_page, flags, mnt_flags,
1967 dev_name, data_page);
1974 * Allocate a new namespace structure and populate it with contents
1975 * copied from the namespace of the passed in task structure.
1977 static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
1978 struct fs_struct *fs)
1980 struct mnt_namespace *new_ns;
1981 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
1982 struct vfsmount *p, *q;
1984 new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
1986 return ERR_PTR(-ENOMEM);
1988 atomic_set(&new_ns->count, 1);
1989 INIT_LIST_HEAD(&new_ns->list);
1990 init_waitqueue_head(&new_ns->poll);
1993 down_write(&namespace_sem);
1994 /* First pass: copy the tree topology */
1995 new_ns->root = copy_tree(mnt_ns->root, mnt_ns->root->mnt_root,
1996 CL_COPY_ALL | CL_EXPIRE);
1997 if (!new_ns->root) {
1998 up_write(&namespace_sem);
2000 return ERR_PTR(-ENOMEM);
2002 spin_lock(&vfsmount_lock);
2003 list_add_tail(&new_ns->list, &new_ns->root->mnt_list);
2004 spin_unlock(&vfsmount_lock);
2007 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
2008 * as belonging to new namespace. We have already acquired a private
2009 * fs_struct, so tsk->fs->lock is not needed.
2016 if (p == fs->root.mnt) {
2018 fs->root.mnt = mntget(q);
2020 if (p == fs->pwd.mnt) {
2022 fs->pwd.mnt = mntget(q);
2025 p = next_mnt(p, mnt_ns->root);
2026 q = next_mnt(q, new_ns->root);
2028 up_write(&namespace_sem);
2038 struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
2039 struct fs_struct *new_fs)
2041 struct mnt_namespace *new_ns;
2046 if (!(flags & CLONE_NEWNS))
2049 new_ns = dup_mnt_ns(ns, new_fs);
2055 SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
2056 char __user *, type, unsigned long, flags, void __user *, data)
2059 unsigned long data_page;
2060 unsigned long type_page;
2061 unsigned long dev_page;
2064 retval = copy_mount_options(type, &type_page);
2068 dir_page = getname(dir_name);
2069 retval = PTR_ERR(dir_page);
2070 if (IS_ERR(dir_page))
2073 retval = copy_mount_options(dev_name, &dev_page);
2077 retval = copy_mount_options(data, &data_page);
2082 retval = do_mount((char *)dev_page, dir_page, (char *)type_page,
2083 flags, (void *)data_page);
2085 free_page(data_page);
2088 free_page(dev_page);
2092 free_page(type_page);
2097 * pivot_root Semantics:
2098 * Moves the root file system of the current process to the directory put_old,
2099 * makes new_root as the new root file system of the current process, and sets
2100 * root/cwd of all processes which had them on the current root to new_root.
2103 * The new_root and put_old must be directories, and must not be on the
2104 * same file system as the current process root. The put_old must be
2105 * underneath new_root, i.e. adding a non-zero number of /.. to the string
2106 * pointed to by put_old must yield the same directory as new_root. No other
2107 * file system may be mounted on put_old. After all, new_root is a mountpoint.
2109 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
2110 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
2111 * in this situation.
2114 * - we don't move root/cwd if they are not at the root (reason: if something
2115 * cared enough to change them, it's probably wrong to force them elsewhere)
2116 * - it's okay to pick a root that isn't the root of a file system, e.g.
2117 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
2118 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
2121 SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
2122 const char __user *, put_old)
2124 struct vfsmount *tmp;
2125 struct path new, old, parent_path, root_parent, root;
2128 if (!capable(CAP_SYS_ADMIN))
2131 error = user_path_dir(new_root, &new);
2135 if (!check_mnt(new.mnt))
2138 error = user_path_dir(put_old, &old);
2142 error = security_sb_pivotroot(&old, &new);
2148 read_lock(¤t->fs->lock);
2149 root = current->fs->root;
2150 path_get(¤t->fs->root);
2151 read_unlock(¤t->fs->lock);
2152 down_write(&namespace_sem);
2153 mutex_lock(&old.dentry->d_inode->i_mutex);
2155 if (IS_MNT_SHARED(old.mnt) ||
2156 IS_MNT_SHARED(new.mnt->mnt_parent) ||
2157 IS_MNT_SHARED(root.mnt->mnt_parent))
2159 if (!check_mnt(root.mnt))
2162 if (IS_DEADDIR(new.dentry->d_inode))
2164 if (d_unhashed(new.dentry) && !IS_ROOT(new.dentry))
2166 if (d_unhashed(old.dentry) && !IS_ROOT(old.dentry))
2169 if (new.mnt == root.mnt ||
2170 old.mnt == root.mnt)
2171 goto out2; /* loop, on the same file system */
2173 if (root.mnt->mnt_root != root.dentry)
2174 goto out2; /* not a mountpoint */
2175 if (root.mnt->mnt_parent == root.mnt)
2176 goto out2; /* not attached */
2177 if (new.mnt->mnt_root != new.dentry)
2178 goto out2; /* not a mountpoint */
2179 if (new.mnt->mnt_parent == new.mnt)
2180 goto out2; /* not attached */
2181 /* make sure we can reach put_old from new_root */
2183 spin_lock(&vfsmount_lock);
2184 if (tmp != new.mnt) {
2186 if (tmp->mnt_parent == tmp)
2187 goto out3; /* already mounted on put_old */
2188 if (tmp->mnt_parent == new.mnt)
2190 tmp = tmp->mnt_parent;
2192 if (!is_subdir(tmp->mnt_mountpoint, new.dentry))
2194 } else if (!is_subdir(old.dentry, new.dentry))
2196 detach_mnt(new.mnt, &parent_path);
2197 detach_mnt(root.mnt, &root_parent);
2198 /* mount old root on put_old */
2199 attach_mnt(root.mnt, &old);
2200 /* mount new_root on / */
2201 attach_mnt(new.mnt, &root_parent);
2202 touch_mnt_namespace(current->nsproxy->mnt_ns);
2203 spin_unlock(&vfsmount_lock);
2204 chroot_fs_refs(&root, &new);
2205 security_sb_post_pivotroot(&root, &new);
2207 path_put(&root_parent);
2208 path_put(&parent_path);
2210 mutex_unlock(&old.dentry->d_inode->i_mutex);
2211 up_write(&namespace_sem);
2219 spin_unlock(&vfsmount_lock);
2223 static void __init init_mount_tree(void)
2225 struct vfsmount *mnt;
2226 struct mnt_namespace *ns;
2229 mnt = do_kern_mount("rootfs", 0, "rootfs", NULL);
2231 panic("Can't create rootfs");
2232 ns = kmalloc(sizeof(*ns), GFP_KERNEL);
2234 panic("Can't allocate initial namespace");
2235 atomic_set(&ns->count, 1);
2236 INIT_LIST_HEAD(&ns->list);
2237 init_waitqueue_head(&ns->poll);
2239 list_add(&mnt->mnt_list, &ns->list);
2243 init_task.nsproxy->mnt_ns = ns;
2246 root.mnt = ns->root;
2247 root.dentry = ns->root->mnt_root;
2249 set_fs_pwd(current->fs, &root);
2250 set_fs_root(current->fs, &root);
2253 void __init mnt_init(void)
2258 init_rwsem(&namespace_sem);
2260 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount),
2261 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
2263 mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);
2265 if (!mount_hashtable)
2266 panic("Failed to allocate mount hash table\n");
2268 printk("Mount-cache hash table entries: %lu\n", HASH_SIZE);
2270 for (u = 0; u < HASH_SIZE; u++)
2271 INIT_LIST_HEAD(&mount_hashtable[u]);
2275 printk(KERN_WARNING "%s: sysfs_init error: %d\n",
2277 fs_kobj = kobject_create_and_add("fs", NULL);
2279 printk(KERN_WARNING "%s: kobj create error\n", __func__);
2284 void __put_mnt_ns(struct mnt_namespace *ns)
2286 struct vfsmount *root = ns->root;
2287 LIST_HEAD(umount_list);
2289 spin_unlock(&vfsmount_lock);
2290 down_write(&namespace_sem);
2291 spin_lock(&vfsmount_lock);
2292 umount_tree(root, 0, &umount_list);
2293 spin_unlock(&vfsmount_lock);
2294 up_write(&namespace_sem);
2295 release_mounts(&umount_list);