1 files changed, 305 insertions, 0 deletions

diff --git a/fs/pnode.c b/fs/pnode.c
new file mode 100644
index 000000000000..aeeec8ba8dd2
--- /dev/null
+++ b/fs/pnode.c
@@ -0,0 +1,305 @@
+/*
+ *  linux/fs/pnode.c
+ *
+ * (C) Copyright IBM Corporation 2005.
+ *      Released under GPL v2.
+ *      Author : Ram Pai (linuxram@us.ibm.com)
+ *
+ */
+#include <linux/namespace.h>
+#include <linux/mount.h>
+#include <linux/fs.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);
+}
+
+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 than
+         * 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;
+        }
+        list_del_init(&mnt->mnt_share);
+
+        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_del(&mnt->mnt_slave);
+                list_add(&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_entry(p->next,
+                                        struct vfsmount, mnt_slave);
+                        list_del_init(&slave_mnt->mnt_slave);
+                        slave_mnt->mnt_master = NULL;
+                }
+        }
+        mnt->mnt_master = master;
+        CLEAR_MNT_SHARED(mnt);
+        INIT_LIST_HEAD(&mnt->mnt_slave_list);
+        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;
+        }
+}
+
+/*
+ * get the next mount in the propagation tree.
+ * @m: the mount seen last
+ * @origin: the original mount from where the tree walk initiated
+ */
+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;
+        *type = CL_PROPAGATION;;
+
+        if (IS_MNT_SHARED(dest))
+                *type |= CL_MAKE_SHARED;
+
+        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));
+        }
+
+        if (dest != p_last_dest) {
+                *type |= CL_SLAVE;
+                return last_src;
+        } else
+                return p_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_entry(tmp_list.next, struct vfsmount, mnt_hash);
+                list_del_init(&child->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);
+        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_del(&child->mnt_hash);
+                        list_add_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;
+}