/* *  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 "internal.h"#include "pnode.h" /* return the next shared peer mount of @p */static inline struct vfsmount *next_peer(struct vfsmount *p){	return list_entry(p->mnt_share.next, struct vfsmount, mnt_share);} static inline struct vfsmount *first_slave(struct vfsmount *p){	return list_entry(p->mnt_slave_list.next, struct vfsmount, mnt_slave);} static inline struct vfsmount *next_slave(struct vfsmount *p){	return list_entry(p->mnt_slave.next, struct vfsmount, mnt_slave);} /* * Return true if path is reachable from root * * namespace_sem is held, and mnt is attached */static bool is_path_reachable(struct vfsmount *mnt, struct dentry *dentry,			 const struct path *root){	while (mnt != root->mnt && mnt->mnt_parent != mnt) {		dentry = mnt->mnt_mountpoint;		mnt = mnt->mnt_parent;	}	return mnt == root->mnt && is_subdir(dentry, root->dentry);} static struct vfsmount *get_peer_under_root(struct vfsmount *mnt,					    struct mnt_namespace *ns,					    const struct path *root){	struct vfsmount *m = mnt; 	do {		/* Check the namespace first for optimization */		if (m->mnt_ns == ns && is_path_reachable(m, m->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 vfsmount *mnt, const struct path *root){	struct vfsmount *m; 	for (m = mnt->mnt_master; m != NULL; m = m->mnt_master) {		struct vfsmount *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 vfsmount *mnt){	struct vfsmount *peer_mnt = mnt, *master = mnt->mnt_master;	struct vfsmount *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_root != mnt->mnt_root) ; 	if (peer_mnt == mnt) {		peer_mnt = next_peer(mnt);		if (peer_mnt == mnt)			peer_mnt = NULL;	}	if (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 vfsmount, mnt_slave);			list_del_init(&slave_mnt->mnt_slave);			slave_mnt->mnt_master = NULL;		}	}	mnt->mnt_master = master;	CLEAR_MNT_SHARED(mnt);	return 0;} void change_mnt_propagation(struct vfsmount *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_flags |= MNT_UNBINDABLE;		else			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 vfsmount *propagation_next(struct vfsmount *m,					 struct vfsmount *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 vfsmount *next;		struct vfsmount *master = m->mnt_master; 		if (master == origin->mnt_master) {			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;	}} /* * return the source mount to be used for cloning * * @dest 	the current destination mount * @last_dest  	the last seen destination mount * @last_src  	the last seen source mount * @type	return CL_SLAVE if the new mount has to be * 		cloned as a slave. */static struct vfsmount *get_source(struct vfsmount *dest,					struct vfsmount *last_dest,					struct vfsmount *last_src,					int *type){	struct vfsmount *p_last_src = NULL;	struct vfsmount *p_last_dest = NULL; 	while (last_dest != dest->mnt_master) {		p_last_dest = last_dest;		p_last_src = last_src;		last_dest = last_dest->mnt_master;		last_src = last_src->mnt_master;	} 	if (p_last_dest) {		do {			p_last_dest = next_peer(p_last_dest);		} while (IS_MNT_NEW(p_last_dest));		/* is that a peer of the earlier? */		if (dest == p_last_dest) {			*type = CL_MAKE_SHARED;			return p_last_src;		}	}	/* slave of the earlier, then */	*type = CL_SLAVE;	/* beginning of peer group among the slaves? */	if (IS_MNT_SHARED(dest))		*type |= CL_MAKE_SHARED;	return last_src;} /* * 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 vfsmount *dest_mnt, struct dentry *dest_dentry,		    struct vfsmount *source_mnt, struct list_head *tree_list){	struct vfsmount *m, *child;	int ret = 0;	struct vfsmount *prev_dest_mnt = dest_mnt;	struct vfsmount *prev_src_mnt  = source_mnt;	LIST_HEAD(tmp_list);	LIST_HEAD(umount_list); 	for (m = propagation_next(dest_mnt, dest_mnt); m;			m = propagation_next(m, dest_mnt)) {		int type;		struct vfsmount *source; 		if (IS_MNT_NEW(m))			continue; 		source =  get_source(m, prev_dest_mnt, prev_src_mnt, &type); 		if (!(child = copy_tree(source, source->mnt_root, type))) {			ret = -ENOMEM;			list_splice(tree_list, tmp_list.prev);			goto out;		} 		if (is_subdir(dest_dentry, m->mnt_root)) {			mnt_set_mountpoint(m, dest_dentry, child);			list_add_tail(&child->mnt_hash, tree_list);		} else {			/*			 * This can happen if the parent mount was bind mounted			 * on some subdirectory of a shared/slave mount.			 */			list_add_tail(&child->mnt_hash, &tmp_list);		}		prev_dest_mnt = m;		prev_src_mnt  = child;	}out:	spin_lock(&vfsmount_lock);	while (!list_empty(&tmp_list)) {		child = list_first_entry(&tmp_list, struct vfsmount, mnt_hash);		umount_tree(child, 0, &umount_list);	}	spin_unlock(&vfsmount_lock);	release_mounts(&umount_list);	return ret;} /* * return true if the refcount is greater than count */static inline int do_refcount_check(struct vfsmount *mnt, int count){	int mycount = atomic_read(&mnt->mnt_count) - mnt->mnt_ghosts;	return (mycount > 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. */int propagate_mount_busy(struct vfsmount *mnt, int refcnt){	struct vfsmount *m, *child;	struct vfsmount *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(m, mnt->mnt_mountpoint, 0);		if (child && list_empty(&child->mnt_mounts) &&		    (ret = do_refcount_check(child, 1)))			break;	}	return ret;} /* * NOTE: unmounting 'mnt' naturally propagates to all other mounts its * parent propagates to. */static void __propagate_umount(struct vfsmount *mnt){	struct vfsmount *parent = mnt->mnt_parent;	struct vfsmount *m; 	BUG_ON(parent == mnt); 	for (m = propagation_next(parent, parent); m;			m = propagation_next(m, parent)) { 		struct vfsmount *child = __lookup_mnt(m,					mnt->mnt_mountpoint, 0);		/*		 * umount the child only if the child has no		 * other children		 */		if (child && list_empty(&child->mnt_mounts))			list_move_tail(&child->mnt_hash, &mnt->mnt_hash);	}} /* * 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. */int propagate_umount(struct list_head *list){	struct vfsmount *mnt; 	list_for_each_entry(mnt, list, mnt_hash)		__propagate_umount(mnt);	return 0;}