diff options
Diffstat (limited to 'fs/pnode.c')
| -rw-r--r-- | fs/pnode.c | 355 |
1 files changed, 355 insertions, 0 deletions
diff --git a/fs/pnode.c b/fs/pnode.c new file mode 100644 index 00000000..ab5fa9e1 --- /dev/null +++ b/fs/pnode.c @@ -0,0 +1,355 @@ +/* + * 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_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 (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; + } +} + +/* + * 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)); + /* 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 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)) + 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_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; +} |