| /* |
| * 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 *master, *slave_mnt; |
| |
| if (list_empty(&mnt->mnt_share)) { |
| if (IS_MNT_SHARED(mnt)) { |
| mnt_release_group_id(mnt); |
| CLEAR_MNT_SHARED(mnt); |
| } |
| master = mnt->mnt_master; |
| if (!master) { |
| 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; |
| } |
| return 0; |
| } |
| } else { |
| struct mount *m; |
| /* |
| * slave 'mnt' to a peer mount that has the |
| * same root dentry. If none is available then |
| * slave it to anything that is available. |
| */ |
| for (m = master = next_peer(mnt); m != mnt; m = next_peer(m)) { |
| if (m->mnt.mnt_root == mnt->mnt.mnt_root) { |
| master = m; |
| break; |
| } |
| } |
| list_del_init(&mnt->mnt_share); |
| mnt->mnt_group_id = 0; |
| CLEAR_MNT_SHARED(mnt); |
| } |
| 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); |
| mnt->mnt_master = master; |
| 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; |
| } |
| |
| static struct mount *find_topper(struct mount *mnt) |
| { |
| /* If there is exactly one mount covering mnt completely return it. */ |
| struct mount *child; |
| |
| if (!list_is_singular(&mnt->mnt_mounts)) |
| return NULL; |
| |
| child = list_first_entry(&mnt->mnt_mounts, struct mount, mnt_child); |
| if (child->mnt_mountpoint != mnt->mnt.mnt_root) |
| return NULL; |
| |
| return child; |
| } |
| |
| /* |
| * 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, *topper; |
| struct mount *parent = mnt->mnt_parent; |
| |
| 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)) { |
| int count = 1; |
| child = __lookup_mnt(&m->mnt, mnt->mnt_mountpoint); |
| if (!child) |
| continue; |
| |
| /* Is there exactly one mount on the child that covers |
| * it completely whose reference should be ignored? |
| */ |
| topper = find_topper(child); |
| if (topper) |
| count += 1; |
| else if (!list_empty(&child->mnt_mounts)) |
| continue; |
| |
| if (do_refcount_check(child, count)) |
| return 1; |
| } |
| return 0; |
| } |
| |
| /* |
| * 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(&m->mnt, mnt->mnt_mountpoint); |
| if (child) |
| child->mnt.mnt_flags &= ~MNT_LOCKED; |
| } |
| } |
| |
| static void umount_one(struct mount *mnt, struct list_head *to_umount) |
| { |
| CLEAR_MNT_MARK(mnt); |
| mnt->mnt.mnt_flags |= MNT_UMOUNT; |
| list_del_init(&mnt->mnt_child); |
| list_del_init(&mnt->mnt_umounting); |
| list_move_tail(&mnt->mnt_list, to_umount); |
| } |
| |
| /* |
| * NOTE: unmounting 'mnt' naturally propagates to all other mounts its |
| * parent propagates to. |
| */ |
| static bool __propagate_umount(struct mount *mnt, |
| struct list_head *to_umount, |
| struct list_head *to_restore) |
| { |
| bool progress = false; |
| struct mount *child; |
| |
| /* |
| * The state of the parent won't change if this mount is |
| * already unmounted or marked as without children. |
| */ |
| if (mnt->mnt.mnt_flags & (MNT_UMOUNT | MNT_MARKED)) |
| goto out; |
| |
| /* Verify topper is the only grandchild that has not been |
| * speculatively unmounted. |
| */ |
| list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { |
| if (child->mnt_mountpoint == mnt->mnt.mnt_root) |
| continue; |
| if (!list_empty(&child->mnt_umounting) && IS_MNT_MARKED(child)) |
| continue; |
| /* Found a mounted child */ |
| goto children; |
| } |
| |
| /* Mark mounts that can be unmounted if not locked */ |
| SET_MNT_MARK(mnt); |
| progress = true; |
| |
| /* If a mount is without children and not locked umount it. */ |
| if (!IS_MNT_LOCKED(mnt)) { |
| umount_one(mnt, to_umount); |
| } else { |
| children: |
| list_move_tail(&mnt->mnt_umounting, to_restore); |
| } |
| out: |
| return progress; |
| } |
| |
| static void umount_list(struct list_head *to_umount, |
| struct list_head *to_restore) |
| { |
| struct mount *mnt, *child, *tmp; |
| list_for_each_entry(mnt, to_umount, mnt_list) { |
| list_for_each_entry_safe(child, tmp, &mnt->mnt_mounts, mnt_child) { |
| /* topper? */ |
| if (child->mnt_mountpoint == mnt->mnt.mnt_root) |
| list_move_tail(&child->mnt_umounting, to_restore); |
| else |
| umount_one(child, to_umount); |
| } |
| } |
| } |
| |
| static void restore_mounts(struct list_head *to_restore) |
| { |
| /* Restore mounts to a clean working state */ |
| while (!list_empty(to_restore)) { |
| struct mount *mnt, *parent; |
| struct mountpoint *mp; |
| |
| mnt = list_first_entry(to_restore, struct mount, mnt_umounting); |
| CLEAR_MNT_MARK(mnt); |
| list_del_init(&mnt->mnt_umounting); |
| |
| /* Should this mount be reparented? */ |
| mp = mnt->mnt_mp; |
| parent = mnt->mnt_parent; |
| while (parent->mnt.mnt_flags & MNT_UMOUNT) { |
| mp = parent->mnt_mp; |
| parent = parent->mnt_parent; |
| } |
| if (parent != mnt->mnt_parent) |
| mnt_change_mountpoint(parent, mp, mnt); |
| } |
| } |
| |
| /* |
| * 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_HEAD(to_restore); |
| LIST_HEAD(to_umount); |
| |
| list_for_each_entry(mnt, list, mnt_list) { |
| struct mount *parent = mnt->mnt_parent; |
| struct mount *m; |
| |
| for (m = propagation_next(parent, parent); m; |
| m = propagation_next(m, parent)) { |
| struct mount *child = __lookup_mnt(&m->mnt, |
| mnt->mnt_mountpoint); |
| if (!child) |
| continue; |
| |
| /* Check the child and parents while progress is made */ |
| while (__propagate_umount(child, |
| &to_umount, &to_restore)) { |
| /* Is the parent a umount candidate? */ |
| child = child->mnt_parent; |
| if (list_empty(&child->mnt_umounting)) |
| break; |
| } |
| } |
| } |
| |
| umount_list(&to_umount, &to_restore); |
| restore_mounts(&to_restore); |
| list_splice_tail(&to_umount, list); |
| |
| return 0; |
| } |