summaryrefslogtreecommitdiffstats
path: root/fs/pnode.c
diff options
context:
space:
mode:
Diffstat (limited to 'fs/pnode.c')
-rw-r--r--fs/pnode.c305
1 files changed, 305 insertions, 0 deletions
diff --git a/fs/pnode.c b/fs/pnode.c
new file mode 100644
index 00000000000..aeeec8ba8dd
--- /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;
+}