X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=fs%2Fpnode.c;h=5cc564a83149a5fc311b57d87793febbdcfd4f27;hb=16106822b67e0a5eb228aebf47e33d6cad1e91b6;hp=2d572b88e6f6e87cc4fa579bfed573a798bfd8aa;hpb=b90fa9ae8f51f098ee480bbaabd6867992e9fc58;p=safe%2Fjmp%2Flinux-2.6

diff --git a/fs/pnode.c b/fs/pnode.c
index 2d572b8..5cc564a 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -6,9 +6,10 @@
  *	Author : Ram Pai (linuxram@us.ibm.com)
  *
  */
-#include <linux/namespace.h>
+#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 */
@@ -17,13 +18,128 @@ 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);
+}
+
+/*
+ * Return true if path is reachable from root
+ *
+ * namespace_sem is held, and mnt is attached
+ */
+static bool is_path_reachable(struct vfsmount *mnt, struct dentry *dentry,
+			 const struct path *root)
+{
+	while (mnt != root->mnt && mnt->mnt_parent != mnt) {
+		dentry = mnt->mnt_mountpoint;
+		mnt = mnt->mnt_parent;
+	}
+	return mnt == root->mnt && is_subdir(dentry, root->dentry);
+}
+
+static struct vfsmount *get_peer_under_root(struct vfsmount *mnt,
+					    struct mnt_namespace *ns,
+					    const struct path *root)
+{
+	struct vfsmount *m = mnt;
+
+	do {
+		/* Check the namespace first for optimization */
+		if (m->mnt_ns == ns && is_path_reachable(m, m->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 vfsmount *mnt, const struct path *root)
+{
+	struct vfsmount *m;
+
+	for (m = mnt->mnt_master; m != NULL; m = m->mnt_master) {
+		struct vfsmount *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 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 then
+	 * 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;
+	}
+	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 vfsmount, mnt_slave);
+			list_del_init(&slave_mnt->mnt_slave);
+			slave_mnt->mnt_master = NULL;
+		}
+	}
+	mnt->mnt_master = master;
+	CLEAR_MNT_SHARED(mnt);
+	return 0;
+}
+
 void change_mnt_propagation(struct vfsmount *mnt, int type)
 {
 	if (type == MS_SHARED) {
 		set_mnt_shared(mnt);
-	} else {
-		list_del_init(&mnt->mnt_share);
-		mnt->mnt_flags &= ~MNT_PNODE_MASK;
+		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;
+		else
+			mnt->mnt_flags &= ~MNT_UNBINDABLE;
 	}
 }
 
@@ -31,14 +147,74 @@ void change_mnt_propagation(struct vfsmount *mnt, int type)
  * 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 vfsmount *propagation_next(struct vfsmount *m,
 					 struct vfsmount *origin)
 {
-	m = next_peer(m);
-	if (m == origin)
-		return NULL;
-	return m;
+	/* 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;
+
+	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;
 }
 
 /*
@@ -66,16 +242,15 @@ int propagate_mnt(struct vfsmount *dest_mnt, struct dentry *dest_dentry,
 
 	for (m = propagation_next(dest_mnt, dest_mnt); m;
 			m = propagation_next(m, dest_mnt)) {
-		int type = CL_PROPAGATION;
+		int type;
+		struct vfsmount *source;
 
 		if (IS_MNT_NEW(m))
 			continue;
 
-		if (IS_MNT_SHARED(m))
-			type |= CL_MAKE_SHARED;
+		source =  get_source(m, prev_dest_mnt, prev_src_mnt, &type);
 
-		if (!(child = copy_tree(source_mnt, source_mnt->mnt_root,
-						type))) {
+		if (!(child = copy_tree(source, source->mnt_root, type))) {
 			ret = -ENOMEM;
 			list_splice(tree_list, tmp_list.prev);
 			goto out;
@@ -97,11 +272,93 @@ int propagate_mnt(struct vfsmount *dest_mnt, struct dentry *dest_dentry,
 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, &umount_list);
+		child = list_first_entry(&tmp_list, struct vfsmount, 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) - 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.
+ */
+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_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.
+ */
+int propagate_umount(struct list_head *list)
+{
+	struct vfsmount *mnt;
+
+	list_for_each_entry(mnt, list, mnt_hash)
+		__propagate_umount(mnt);
+	return 0;
+}