/* *  linux/fs/pnode.c * * (C) Copyright IBM Corporation 2005. *	Released under GPL v2. *	Author : Ram Pai (linuxram@us.ibm.com) * */#include <linux/mnt_namespace.h>#include <linux/mount.h>#include <linux/fs.h>#include <linux/nsproxy.h>#include "internal.h"#include "pnode.h" /* return the next shared peer mount of @p */static inline struct mount *next_peer(struct mount *p){	return list_entry(p->mnt_share.next, struct mount, mnt_share);} static inline struct mount *first_slave(struct mount *p){	return list_entry(p->mnt_slave_list.next, struct mount, mnt_slave);} static inline struct mount *next_slave(struct mount *p){	return list_entry(p->mnt_slave.next, struct mount, mnt_slave);} static struct mount *get_peer_under_root(struct mount *mnt,					 struct mnt_namespace *ns,					 const struct path *root){	struct mount *m = mnt; 	do {		/* Check the namespace first for optimization */		if (m->mnt_ns == ns && is_path_reachable(m, m->mnt.mnt_root, root))			return m; 		m = next_peer(m);	} while (m != mnt); 	return NULL;} /* * Get ID of closest dominating peer group having a representative * under the given root. * * Caller must hold namespace_sem */int get_dominating_id(struct mount *mnt, const struct path *root){	struct mount *m; 	for (m = mnt->mnt_master; m != NULL; m = m->mnt_master) {		struct mount *d = get_peer_under_root(m, mnt->mnt_ns, root);		if (d)			return d->mnt_group_id;	} 	return 0;} static int do_make_slave(struct mount *mnt){	struct mount *peer_mnt = mnt, *master = mnt->mnt_master;	struct mount *slave_mnt; 	/*	 * slave 'mnt' to a peer mount that has the	 * same root dentry. If none is available then	 * slave it to anything that is available.	 */	while ((peer_mnt = next_peer(peer_mnt)) != mnt &&	       peer_mnt->mnt.mnt_root != mnt->mnt.mnt_root) ; 	if (peer_mnt == mnt) {		peer_mnt = next_peer(mnt);		if (peer_mnt == mnt)			peer_mnt = NULL;	}	if (mnt->mnt_group_id && IS_MNT_SHARED(mnt) &&	    list_empty(&mnt->mnt_share))		mnt_release_group_id(mnt); 	list_del_init(&mnt->mnt_share);	mnt->mnt_group_id = 0; 	if (peer_mnt)		master = peer_mnt; 	if (master) {		list_for_each_entry(slave_mnt, &mnt->mnt_slave_list, mnt_slave)			slave_mnt->mnt_master = master;		list_move(&mnt->mnt_slave, &master->mnt_slave_list);		list_splice(&mnt->mnt_slave_list, master->mnt_slave_list.prev);		INIT_LIST_HEAD(&mnt->mnt_slave_list);	} else {		struct list_head *p = &mnt->mnt_slave_list;		while (!list_empty(p)) {                        slave_mnt = list_first_entry(p,					struct mount, mnt_slave);			list_del_init(&slave_mnt->mnt_slave);			slave_mnt->mnt_master = NULL;		}	}	mnt->mnt_master = master;	CLEAR_MNT_SHARED(mnt);	return 0;} /* * vfsmount lock must be held for write */void change_mnt_propagation(struct mount *mnt, int type){	if (type == MS_SHARED) {		set_mnt_shared(mnt);		return;	}	do_make_slave(mnt);	if (type != MS_SLAVE) {		list_del_init(&mnt->mnt_slave);		mnt->mnt_master = NULL;		if (type == MS_UNBINDABLE)			mnt->mnt.mnt_flags |= MNT_UNBINDABLE;		else			mnt->mnt.mnt_flags &= ~MNT_UNBINDABLE;	}} /* * get the next mount in the propagation tree. * @m: the mount seen last * @origin: the original mount from where the tree walk initiated * * Note that peer groups form contiguous segments of slave lists. * We rely on that in get_source() to be able to find out if * vfsmount found while iterating with propagation_next() is * a peer of one we'd found earlier. */static struct mount *propagation_next(struct mount *m,					 struct mount *origin){	/* are there any slaves of this mount? */	if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))		return first_slave(m); 	while (1) {		struct mount *master = m->mnt_master; 		if (master == origin->mnt_master) {			struct mount *next = next_peer(m);			return (next == origin) ? NULL : next;		} else if (m->mnt_slave.next != &master->mnt_slave_list)			return next_slave(m); 		/* back at master */		m = master;	}} static struct mount *next_group(struct mount *m, struct mount *origin){	while (1) {		while (1) {			struct mount *next;			if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))				return first_slave(m);			next = next_peer(m);			if (m->mnt_group_id == origin->mnt_group_id) {				if (next == origin)					return NULL;			} else if (m->mnt_slave.next != &next->mnt_slave)				break;			m = next;		}		/* m is the last peer */		while (1) {			struct mount *master = m->mnt_master;			if (m->mnt_slave.next != &master->mnt_slave_list)				return next_slave(m);			m = next_peer(master);			if (master->mnt_group_id == origin->mnt_group_id)				break;			if (master->mnt_slave.next == &m->mnt_slave)				break;			m = master;		}		if (m == origin)			return NULL;	}} /* all accesses are serialized by namespace_sem */static struct user_namespace *user_ns;static struct mount *last_dest, *first_source, *last_source, *dest_master;static struct mountpoint *mp;static struct hlist_head *list; static inline bool peers(struct mount *m1, struct mount *m2){	return m1->mnt_group_id == m2->mnt_group_id && m1->mnt_group_id;} static int propagate_one(struct mount *m){	struct mount *child;	int type;	/* skip ones added by this propagate_mnt() */	if (IS_MNT_NEW(m))		return 0;	/* skip if mountpoint isn't covered by it */	if (!is_subdir(mp->m_dentry, m->mnt.mnt_root))		return 0;	if (peers(m, last_dest)) {		type = CL_MAKE_SHARED;	} else {		struct mount *n, *p;		bool done;		for (n = m; ; n = p) {			p = n->mnt_master;			if (p == dest_master || IS_MNT_MARKED(p))				break;		}		do {			struct mount *parent = last_source->mnt_parent;			if (last_source == first_source)				break;			done = parent->mnt_master == p;			if (done && peers(n, parent))				break;			last_source = last_source->mnt_master;		} while (!done); 		type = CL_SLAVE;		/* beginning of peer group among the slaves? */		if (IS_MNT_SHARED(m))			type |= CL_MAKE_SHARED;	}			/* Notice when we are propagating across user namespaces */	if (m->mnt_ns->user_ns != user_ns)		type |= CL_UNPRIVILEGED;	child = copy_tree(last_source, last_source->mnt.mnt_root, type);	if (IS_ERR(child))		return PTR_ERR(child);	child->mnt.mnt_flags &= ~MNT_LOCKED;	mnt_set_mountpoint(m, mp, child);	last_dest = m;	last_source = child;	if (m->mnt_master != dest_master) {		read_seqlock_excl(&mount_lock);		SET_MNT_MARK(m->mnt_master);		read_sequnlock_excl(&mount_lock);	}	hlist_add_head(&child->mnt_hash, list);	return count_mounts(m->mnt_ns, child);} /* * mount 'source_mnt' under the destination 'dest_mnt' at * dentry 'dest_dentry'. And propagate that mount to * all the peer and slave mounts of 'dest_mnt'. * Link all the new mounts into a propagation tree headed at * source_mnt. Also link all the new mounts using ->mnt_list * headed at source_mnt's ->mnt_list * * @dest_mnt: destination mount. * @dest_dentry: destination dentry. * @source_mnt: source mount. * @tree_list : list of heads of trees to be attached. */int propagate_mnt(struct mount *dest_mnt, struct mountpoint *dest_mp,		    struct mount *source_mnt, struct hlist_head *tree_list){	struct mount *m, *n;	int ret = 0; 	/*	 * we don't want to bother passing tons of arguments to	 * propagate_one(); everything is serialized by namespace_sem,	 * so globals will do just fine.	 */	user_ns = current->nsproxy->mnt_ns->user_ns;	last_dest = dest_mnt;	first_source = source_mnt;	last_source = source_mnt;	mp = dest_mp;	list = tree_list;	dest_master = dest_mnt->mnt_master; 	/* all peers of dest_mnt, except dest_mnt itself */	for (n = next_peer(dest_mnt); n != dest_mnt; n = next_peer(n)) {		ret = propagate_one(n);		if (ret)			goto out;	} 	/* all slave groups */	for (m = next_group(dest_mnt, dest_mnt); m;			m = next_group(m, dest_mnt)) {		/* everything in that slave group */		n = m;		do {			ret = propagate_one(n);			if (ret)				goto out;			n = next_peer(n);		} while (n != m);	}out:	read_seqlock_excl(&mount_lock);	hlist_for_each_entry(n, tree_list, mnt_hash) {		m = n->mnt_parent;		if (m->mnt_master != dest_mnt->mnt_master)			CLEAR_MNT_MARK(m->mnt_master);	}	read_sequnlock_excl(&mount_lock);	return ret;} /* * return true if the refcount is greater than count */static inline int do_refcount_check(struct mount *mnt, int count){	return mnt_get_count(mnt) > count;} /* * check if the mount 'mnt' can be unmounted successfully. * @mnt: the mount to be checked for unmount * NOTE: unmounting 'mnt' would naturally propagate to all * other mounts its parent propagates to. * Check if any of these mounts that **do not have submounts** * have more references than 'refcnt'. If so return busy. * * vfsmount lock must be held for write */int propagate_mount_busy(struct mount *mnt, int refcnt){	struct mount *m, *child;	struct mount *parent = mnt->mnt_parent;	int ret = 0; 	if (mnt == parent)		return do_refcount_check(mnt, refcnt); 	/*	 * quickly check if the current mount can be unmounted.	 * If not, we don't have to go checking for all other	 * mounts	 */	if (!list_empty(&mnt->mnt_mounts) || do_refcount_check(mnt, refcnt))		return 1; 	for (m = propagation_next(parent, parent); m;	     		m = propagation_next(m, parent)) {		child = __lookup_mnt_last(&m->mnt, mnt->mnt_mountpoint);		if (child && list_empty(&child->mnt_mounts) &&		    (ret = do_refcount_check(child, 1)))			break;	}	return ret;} /* * Clear MNT_LOCKED when it can be shown to be safe. * * mount_lock lock must be held for write */void propagate_mount_unlock(struct mount *mnt){	struct mount *parent = mnt->mnt_parent;	struct mount *m, *child; 	BUG_ON(parent == mnt); 	for (m = propagation_next(parent, parent); m;			m = propagation_next(m, parent)) {		child = __lookup_mnt_last(&m->mnt, mnt->mnt_mountpoint);		if (child)			child->mnt.mnt_flags &= ~MNT_LOCKED;	}} /* * Mark all mounts that the MNT_LOCKED logic will allow to be unmounted. */static void mark_umount_candidates(struct mount *mnt){	struct mount *parent = mnt->mnt_parent;	struct mount *m; 	BUG_ON(parent == mnt); 	for (m = propagation_next(parent, parent); m;			m = propagation_next(m, parent)) {		struct mount *child = __lookup_mnt_last(&m->mnt,						mnt->mnt_mountpoint);		if (child && (!IS_MNT_LOCKED(child) || IS_MNT_MARKED(m))) {			SET_MNT_MARK(child);		}	}} /* * NOTE: unmounting 'mnt' naturally propagates to all other mounts its * parent propagates to. */static void __propagate_umount(struct mount *mnt){	struct mount *parent = mnt->mnt_parent;	struct mount *m; 	BUG_ON(parent == mnt); 	for (m = propagation_next(parent, parent); m;			m = propagation_next(m, parent)) { 		struct mount *child = __lookup_mnt_last(&m->mnt,						mnt->mnt_mountpoint);		/*		 * umount the child only if the child has no children		 * and the child is marked safe to unmount.		 */		if (!child || !IS_MNT_MARKED(child))			continue;		CLEAR_MNT_MARK(child);		if (list_empty(&child->mnt_mounts)) {			list_del_init(&child->mnt_child);			child->mnt.mnt_flags |= MNT_UMOUNT;			list_move_tail(&child->mnt_list, &mnt->mnt_list);		}	}} /* * collect all mounts that receive propagation from the mount in @list, * and return these additional mounts in the same list. * @list: the list of mounts to be unmounted. * * vfsmount lock must be held for write */int propagate_umount(struct list_head *list){	struct mount *mnt; 	list_for_each_entry_reverse(mnt, list, mnt_list)		mark_umount_candidates(mnt); 	list_for_each_entry(mnt, list, mnt_list)		__propagate_umount(mnt);	return 0;}