| /* |
| * 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 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.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.mnt_ns, root); |
| if (d) |
| return d->mnt.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 (IS_MNT_SHARED(&mnt->mnt) && list_empty(&mnt->mnt_share)) |
| mnt_release_group_id(mnt); |
| |
| list_del_init(&mnt->mnt_share); |
| mnt->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->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->mnt) && !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; |
| } |
| } |
| |
| /* |
| * 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 mount *get_source(struct mount *dest, |
| struct mount *last_dest, |
| struct mount *last_src, |
| int *type) |
| { |
| struct mount *p_last_src = NULL; |
| struct mount *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->mnt)); |
| /* 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->mnt)) |
| *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 mount *dest_mnt, struct dentry *dest_dentry, |
| struct mount *source_mnt, struct list_head *tree_list) |
| { |
| struct mount *m, *child; |
| int ret = 0; |
| struct mount *prev_dest_mnt = dest_mnt; |
| struct mount *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 mount *source; |
| |
| if (IS_MNT_NEW(&m->mnt)) |
| continue; |
| |
| source = get_source(m, prev_dest_mnt, prev_src_mnt, &type); |
| |
| if (!(child = copy_tree(source, source->mnt.mnt_root, type))) { |
| ret = -ENOMEM; |
| list_splice(tree_list, tmp_list.prev); |
| goto out; |
| } |
| |
| if (is_subdir(dest_dentry, m->mnt.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: |
| br_write_lock(vfsmount_lock); |
| while (!list_empty(&tmp_list)) { |
| child = list_first_entry(&tmp_list, struct mount, mnt_hash); |
| umount_tree(child, 0, &umount_list); |
| } |
| br_write_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 mount *mnt, int count) |
| { |
| int mycount = mnt_get_count(mnt) - mnt->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. |
| * |
| * 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(&m->mnt, 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 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(&m->mnt, |
| 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. |
| * |
| * vfsmount lock must be held for write |
| */ |
| int propagate_umount(struct list_head *list) |
| { |
| struct mount *mnt; |
| |
| list_for_each_entry(mnt, list, mnt_hash) |
| __propagate_umount(mnt); |
| return 0; |
| } |