umount_tree() locking change

@@ -394,32 +394,45 @@ int may_umount(struct vfsmount *mnt)
 
 EXPORT_SYMBOL(may_umount);
 
-static void umount_tree(struct vfsmount *mnt)
+static void release_mounts(struct list_head *head)
+{
+	struct vfsmount *mnt;
+	while(!list_empty(head)) {
+		mnt = list_entry(head->next, struct vfsmount, mnt_hash);
+		list_del_init(&mnt->mnt_hash);
+		if (mnt->mnt_parent != mnt) {
+			struct dentry *dentry;
+			struct vfsmount *m;
+			spin_lock(&vfsmount_lock);
+			dentry = mnt->mnt_mountpoint;
+			m = mnt->mnt_parent;
+			mnt->mnt_mountpoint = mnt->mnt_root;
+			mnt->mnt_parent = mnt;
+			spin_unlock(&vfsmount_lock);
+			dput(dentry);
+			mntput(m);
+		}
+		mntput(mnt);
+	}
+}
+
+static void umount_tree(struct vfsmount *mnt, struct list_head *kill)
 {
 	struct vfsmount *p;
-	LIST_HEAD(kill);
 
 	for (p = mnt; p; p = next_mnt(p, mnt)) {
-		list_del(&p->mnt_list);
-		list_add(&p->mnt_list, &kill);
-		__touch_namespace(p->mnt_namespace);
-		p->mnt_namespace = NULL;
+		list_del(&p->mnt_hash);
+		list_add(&p->mnt_hash, kill);
 	}
 
-	while (!list_empty(&kill)) {
-		mnt = list_entry(kill.next, struct vfsmount, mnt_list);
-		list_del_init(&mnt->mnt_list);
-		list_del_init(&mnt->mnt_expire);
-		if (mnt->mnt_parent == mnt) {
-			spin_unlock(&vfsmount_lock);
-		} else {
-			struct nameidata old_nd;
-			detach_mnt(mnt, &old_nd);
-			spin_unlock(&vfsmount_lock);
-			path_release(&old_nd);
-		}
-		mntput(mnt);
-		spin_lock(&vfsmount_lock);
+	list_for_each_entry(p, kill, mnt_hash) {
+		list_del_init(&p->mnt_expire);
+		list_del_init(&p->mnt_list);
+		__touch_namespace(p->mnt_namespace);
+		p->mnt_namespace = NULL;
+		list_del_init(&p->mnt_child);
+		if (p->mnt_parent != p)
+			mnt->mnt_mountpoint->d_mounted--;
 	}
 }
 

@@ -427,6 +440,7 @@ static int do_umount(struct vfsmount *mn
 {
 	struct super_block *sb = mnt->mnt_sb;
 	int retval;
+	LIST_HEAD(umount_list);
 
 	retval = security_sb_umount(mnt, flags);
 	if (retval)

@@ -497,13 +511,14 @@ static int do_umount(struct vfsmount *mn
 	retval = -EBUSY;
 	if (atomic_read(&mnt->mnt_count) == 2 || flags & MNT_DETACH) {
 		if (!list_empty(&mnt->mnt_list))
-			umount_tree(mnt);
+			umount_tree(mnt, &umount_list);
 		retval = 0;
 	}
 	spin_unlock(&vfsmount_lock);
 	if (retval)
 		security_sb_umount_busy(mnt);
 	up_write(&current->namespace->sem);
+	release_mounts(&umount_list);
 	return retval;
 }
 

@@ -616,9 +631,11 @@ static struct vfsmount *copy_tree(struct
 	return res;
 Enomem:
 	if (res) {
+		LIST_HEAD(umount_list);
 		spin_lock(&vfsmount_lock);
-		umount_tree(res);
+		umount_tree(res, &umount_list);
 		spin_unlock(&vfsmount_lock);
+		release_mounts(&umount_list);
 	}
 	return NULL;
 }

@@ -698,9 +715,11 @@ static int do_loopback(struct nameidata 
 
 	err = graft_tree(mnt, nd);
 	if (err) {
+		LIST_HEAD(umount_list);
 		spin_lock(&vfsmount_lock);
-		umount_tree(mnt);
+		umount_tree(mnt, &umount_list);
 		spin_unlock(&vfsmount_lock);
+		release_mounts(&umount_list);
 	}
 
 out:

@@ -875,7 +894,8 @@ unlock:
 
 EXPORT_SYMBOL_GPL(do_add_mount);
 
-static void expire_mount(struct vfsmount *mnt, struct list_head *mounts)
+static void expire_mount(struct vfsmount *mnt, struct list_head *mounts,
+				struct list_head *umounts)
 {
 	spin_lock(&vfsmount_lock);
 

@@ -893,16 +913,12 @@ static void expire_mount(struct vfsmount
 	 * contributed by the vfsmount parent and the mntget above
 	 */
 	if (atomic_read(&mnt->mnt_count) == 2) {
-		struct nameidata old_nd;
-
 		/* delete from the namespace */
 		touch_namespace(mnt->mnt_namespace);
 		list_del_init(&mnt->mnt_list);
 		mnt->mnt_namespace = NULL;
-		detach_mnt(mnt, &old_nd);
+		umount_tree(mnt, umounts);
 		spin_unlock(&vfsmount_lock);
-		path_release(&old_nd);
-		mntput(mnt);
 	} else {
 		/*
 		 * Someone brought it back to life whilst we didn't have any

@@ -951,6 +967,7 @@ void mark_mounts_for_expiry(struct list_
 	 * - dispose of the corpse
 	 */
 	while (!list_empty(&graveyard)) {
+		LIST_HEAD(umounts);
 		mnt = list_entry(graveyard.next, struct vfsmount, mnt_expire);
 		list_del_init(&mnt->mnt_expire);
 

@@ -963,12 +980,11 @@ void mark_mounts_for_expiry(struct list_
 
 		spin_unlock(&vfsmount_lock);
 		down_write(&namespace->sem);
-		expire_mount(mnt, mounts);
+		expire_mount(mnt, mounts, &umounts);
 		up_write(&namespace->sem);
-
+		release_mounts(&umounts);
 		mntput(mnt);
 		put_namespace(namespace);
-
 		spin_lock(&vfsmount_lock);
 	}
 

@@ -1508,12 +1524,14 @@ void __init mnt_init(unsigned long mempa
 void __put_namespace(struct namespace *namespace)
 {
 	struct vfsmount *root = namespace->root;
+	LIST_HEAD(umount_list);
 	namespace->root = NULL;
 	spin_unlock(&vfsmount_lock);
 	down_write(&namespace->sem);
 	spin_lock(&vfsmount_lock);
-	umount_tree(root);
+	umount_tree(root, &umount_list);
 	spin_unlock(&vfsmount_lock);
 	up_write(&namespace->sem);
+	release_mounts(&umount_list);
 	kfree(namespace);
 }