Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6:
  [PATCH] mnt_expire is protected by namespace_sem, no need for vfsmount_lock
  [PATCH] do shrink_submounts() for all fs types
  [PATCH] sanitize locking in mark_mounts_for_expiry() and shrink_submounts()
  [PATCH] count ghost references to vfsmounts
  [PATCH] reduce stack footprint in namespace.c

1 files changed, 69 insertions, 131 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index 7953c96a2071..94f026ec990a 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -155,15 +155,15 @@ static void __touch_mnt_namespace(struct mnt_namespace *ns)
 	}
 }
 
-static void detach_mnt(struct vfsmount *mnt, struct nameidata *old_nd)
+static void detach_mnt(struct vfsmount *mnt, struct path *old_path)
 {
-	old_nd->path.dentry = mnt->mnt_mountpoint;
-	old_nd->path.mnt = mnt->mnt_parent;
+	old_path->dentry = mnt->mnt_mountpoint;
+	old_path->mnt = mnt->mnt_parent;
 	mnt->mnt_parent = mnt;
 	mnt->mnt_mountpoint = mnt->mnt_root;
 	list_del_init(&mnt->mnt_child);
 	list_del_init(&mnt->mnt_hash);
-	old_nd->path.dentry->d_mounted--;
+	old_path->dentry->d_mounted--;
 }
 
 void mnt_set_mountpoint(struct vfsmount *mnt, struct dentry *dentry,
@@ -174,12 +174,12 @@ void mnt_set_mountpoint(struct vfsmount *mnt, struct dentry *dentry,
 	dentry->d_mounted++;
 }
 
-static void attach_mnt(struct vfsmount *mnt, struct nameidata *nd)
+static void attach_mnt(struct vfsmount *mnt, struct path *path)
 {
-	mnt_set_mountpoint(nd->path.mnt, nd->path.dentry, mnt);
+	mnt_set_mountpoint(path->mnt, path->dentry, mnt);
 	list_add_tail(&mnt->mnt_hash, mount_hashtable +
-			hash(nd->path.mnt, nd->path.dentry));
-	list_add_tail(&mnt->mnt_child, &nd->path.mnt->mnt_mounts);
+			hash(path->mnt, path->dentry));
+	list_add_tail(&mnt->mnt_child, &path->mnt->mnt_mounts);
 }
 
 /*
@@ -262,10 +262,8 @@ static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root,
 		/* stick the duplicate mount on the same expiry list
 		 * as the original if that was on one */
 		if (flag & CL_EXPIRE) {
-			spin_lock(&vfsmount_lock);
 			if (!list_empty(&old->mnt_expire))
 				list_add(&mnt->mnt_expire, &old->mnt_expire);
-			spin_unlock(&vfsmount_lock);
 		}
 	}
 	return mnt;
@@ -548,6 +546,7 @@ void release_mounts(struct list_head *head)
 			m = mnt->mnt_parent;
 			mnt->mnt_mountpoint = mnt->mnt_root;
 			mnt->mnt_parent = mnt;
+			m->mnt_ghosts--;
 			spin_unlock(&vfsmount_lock);
 			dput(dentry);
 			mntput(m);
@@ -572,12 +571,16 @@ void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill)
 		__touch_mnt_namespace(p->mnt_ns);
 		p->mnt_ns = NULL;
 		list_del_init(&p->mnt_child);
-		if (p->mnt_parent != p)
+		if (p->mnt_parent != p) {
+			p->mnt_parent->mnt_ghosts++;
 			p->mnt_mountpoint->d_mounted--;
+		}
 		change_mnt_propagation(p, MS_PRIVATE);
 	}
 }
 
+static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts);
+
 static int do_umount(struct vfsmount *mnt, int flags)
 {
 	struct super_block *sb = mnt->mnt_sb;
@@ -650,6 +653,9 @@ static int do_umount(struct vfsmount *mnt, int flags)
 	spin_lock(&vfsmount_lock);
 	event++;
 
+	if (!(flags & MNT_DETACH))
+		shrink_submounts(mnt, &umount_list);
+
 	retval = -EBUSY;
 	if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) {
 		if (!list_empty(&mnt->mnt_list))
@@ -744,7 +750,7 @@ struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry,
 					int flag)
 {
 	struct vfsmount *res, *p, *q, *r, *s;
-	struct nameidata nd;
+	struct path path;
 
 	if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt))
 		return NULL;
@@ -769,14 +775,14 @@ struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry,
 				q = q->mnt_parent;
 			}
 			p = s;
-			nd.path.mnt = q;
-			nd.path.dentry = p->mnt_mountpoint;
+			path.mnt = q;
+			path.dentry = p->mnt_mountpoint;
 			q = clone_mnt(p, p->mnt_root, flag);
 			if (!q)
 				goto Enomem;
 			spin_lock(&vfsmount_lock);
 			list_add_tail(&q->mnt_list, &res->mnt_list);
-			attach_mnt(q, &nd);
+			attach_mnt(q, &path);
 			spin_unlock(&vfsmount_lock);
 		}
 	}
@@ -876,11 +882,11 @@ void drop_collected_mounts(struct vfsmount *mnt)
  * in allocations.
  */
 static int attach_recursive_mnt(struct vfsmount *source_mnt,
-			struct nameidata *nd, struct nameidata *parent_nd)
+			struct path *path, struct path *parent_path)
 {
 	LIST_HEAD(tree_list);
-	struct vfsmount *dest_mnt = nd->path.mnt;
-	struct dentry *dest_dentry = nd->path.dentry;
+	struct vfsmount *dest_mnt = path->mnt;
+	struct dentry *dest_dentry = path->dentry;
 	struct vfsmount *child, *p;
 
 	if (propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list))
@@ -892,9 +898,9 @@ static int attach_recursive_mnt(struct vfsmount *source_mnt,
 	}
 
 	spin_lock(&vfsmount_lock);
-	if (parent_nd) {
-		detach_mnt(source_mnt, parent_nd);
-		attach_mnt(source_mnt, nd);
+	if (parent_path) {
+		detach_mnt(source_mnt, parent_path);
+		attach_mnt(source_mnt, path);
 		touch_mnt_namespace(current->nsproxy->mnt_ns);
 	} else {
 		mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt);
@@ -930,7 +936,7 @@ static int graft_tree(struct vfsmount *mnt, struct nameidata *nd)
 
 	err = -ENOENT;
 	if (IS_ROOT(nd->path.dentry) || !d_unhashed(nd->path.dentry))
-		err = attach_recursive_mnt(mnt, nd, NULL);
+		err = attach_recursive_mnt(mnt, &nd->path, NULL);
 out_unlock:
 	mutex_unlock(&nd->path.dentry->d_inode->i_mutex);
 	if (!err)
@@ -1059,7 +1065,8 @@ static inline int tree_contains_unbindable(struct vfsmount *mnt)
  */
 static noinline int do_move_mount(struct nameidata *nd, char *old_name)
 {
-	struct nameidata old_nd, parent_nd;
+	struct nameidata old_nd;
+	struct path parent_path;
 	struct vfsmount *p;
 	int err = 0;
 	if (!capable(CAP_SYS_ADMIN))
@@ -1114,21 +1121,19 @@ static noinline int do_move_mount(struct nameidata *nd, char *old_name)
 		if (p == old_nd.path.mnt)
 			goto out1;
 
-	err = attach_recursive_mnt(old_nd.path.mnt, nd, &parent_nd);
+	err = attach_recursive_mnt(old_nd.path.mnt, &nd->path, &parent_path);
 	if (err)
 		goto out1;
 
-	spin_lock(&vfsmount_lock);
 	/* if the mount is moved, it should no longer be expire
 	 * automatically */
 	list_del_init(&old_nd.path.mnt->mnt_expire);
-	spin_unlock(&vfsmount_lock);
 out1:
 	mutex_unlock(&nd->path.dentry->d_inode->i_mutex);
 out:
 	up_write(&namespace_sem);
 	if (!err)
-		path_put(&parent_nd.path);
+		path_put(&parent_path);
 	path_put(&old_nd.path);
 	return err;
 }
@@ -1189,12 +1194,9 @@ int do_add_mount(struct vfsmount *newmnt, struct nameidata *nd,
 	if ((err = graft_tree(newmnt, nd)))
 		goto unlock;
 
-	if (fslist) {
-		/* add to the specified expiration list */
-		spin_lock(&vfsmount_lock);
+	if (fslist) /* add to the specified expiration list */
 		list_add_tail(&newmnt->mnt_expire, fslist);
-		spin_unlock(&vfsmount_lock);
-	}
+
 	up_write(&namespace_sem);
 	return 0;
 
@@ -1206,75 +1208,6 @@ unlock:
 
 EXPORT_SYMBOL_GPL(do_add_mount);
 
-static void expire_mount(struct vfsmount *mnt, struct list_head *mounts,
-				struct list_head *umounts)
-{
-	spin_lock(&vfsmount_lock);
-
-	/*
-	 * Check if mount is still attached, if not, let whoever holds it deal
-	 * with the sucker
-	 */
-	if (mnt->mnt_parent == mnt) {
-		spin_unlock(&vfsmount_lock);
-		return;
-	}
-
-	/*
-	 * Check that it is still dead: the count should now be 2 - as
-	 * contributed by the vfsmount parent and the mntget above
-	 */
-	if (!propagate_mount_busy(mnt, 2)) {
-		/* delete from the namespace */
-		touch_mnt_namespace(mnt->mnt_ns);
-		list_del_init(&mnt->mnt_list);
-		mnt->mnt_ns = NULL;
-		umount_tree(mnt, 1, umounts);
-		spin_unlock(&vfsmount_lock);
-	} else {
-		/*
-		 * Someone brought it back to life whilst we didn't have any
-		 * locks held so return it to the expiration list
-		 */
-		list_add_tail(&mnt->mnt_expire, mounts);
-		spin_unlock(&vfsmount_lock);
-	}
-}
-
-/*
- * go through the vfsmounts we've just consigned to the graveyard to
- * - check that they're still dead
- * - delete the vfsmount from the appropriate namespace under lock
- * - dispose of the corpse
- */
-static void expire_mount_list(struct list_head *graveyard, struct list_head *mounts)
-{
-	struct mnt_namespace *ns;
-	struct vfsmount *mnt;
-
-	while (!list_empty(graveyard)) {
-		LIST_HEAD(umounts);
-		mnt = list_first_entry(graveyard, struct vfsmount, mnt_expire);
-		list_del_init(&mnt->mnt_expire);
-
-		/* don't do anything if the namespace is dead - all the
-		 * vfsmounts from it are going away anyway */
-		ns = mnt->mnt_ns;
-		if (!ns || !ns->root)
-			continue;
-		get_mnt_ns(ns);
-
-		spin_unlock(&vfsmount_lock);
-		down_write(&namespace_sem);
-		expire_mount(mnt, mounts, &umounts);
-		up_write(&namespace_sem);
-		release_mounts(&umounts);
-		mntput(mnt);
-		put_mnt_ns(ns);
-		spin_lock(&vfsmount_lock);
-	}
-}
-
 /*
  * process a list of expirable mountpoints with the intent of discarding any
  * mountpoints that aren't in use and haven't been touched since last we came
@@ -1284,10 +1217,12 @@ void mark_mounts_for_expiry(struct list_head *mounts)
 {
 	struct vfsmount *mnt, *next;
 	LIST_HEAD(graveyard);
+	LIST_HEAD(umounts);
 
 	if (list_empty(mounts))
 		return;
 
+	down_write(&namespace_sem);
 	spin_lock(&vfsmount_lock);
 
 	/* extract from the expiration list every vfsmount that matches the
@@ -1298,16 +1233,19 @@ void mark_mounts_for_expiry(struct list_head *mounts)
 	 */
 	list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
 		if (!xchg(&mnt->mnt_expiry_mark, 1) ||
-		    atomic_read(&mnt->mnt_count) != 1)
+			propagate_mount_busy(mnt, 1))
 			continue;
-
-		mntget(mnt);
 		list_move(&mnt->mnt_expire, &graveyard);
 	}
-
-	expire_mount_list(&graveyard, mounts);
-
+	while (!list_empty(&graveyard)) {
+		mnt = list_first_entry(&graveyard, struct vfsmount, mnt_expire);
+		touch_mnt_namespace(mnt->mnt_ns);
+		umount_tree(mnt, 1, &umounts);
+	}
 	spin_unlock(&vfsmount_lock);
+	up_write(&namespace_sem);
+
+	release_mounts(&umounts);
 }
 
 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
@@ -1343,7 +1281,6 @@ resume:
 		}
 
 		if (!propagate_mount_busy(mnt, 1)) {
-			mntget(mnt);
 			list_move_tail(&mnt->mnt_expire, graveyard);
 			found++;
 		}
@@ -1363,22 +1300,22 @@ resume:
  * process a list of expirable mountpoints with the intent of discarding any
  * submounts of a specific parent mountpoint
  */
-void shrink_submounts(struct vfsmount *mountpoint, struct list_head *mounts)
+static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts)
 {
 	LIST_HEAD(graveyard);
-	int found;
-
-	spin_lock(&vfsmount_lock);
+	struct vfsmount *m;
 
 	/* extract submounts of 'mountpoint' from the expiration list */
-	while ((found = select_submounts(mountpoint, &graveyard)) != 0)
-		expire_mount_list(&graveyard, mounts);
-
-	spin_unlock(&vfsmount_lock);
+	while (select_submounts(mnt, &graveyard)) {
+		while (!list_empty(&graveyard)) {
+			m = list_first_entry(&graveyard, struct vfsmount,
+						mnt_expire);
+			touch_mnt_namespace(mnt->mnt_ns);
+			umount_tree(mnt, 1, umounts);
+		}
+	}
 }
 
-EXPORT_SYMBOL_GPL(shrink_submounts);
-
 /*
  * Some copy_from_user() implementations do not return the exact number of
  * bytes remaining to copy on a fault.  But copy_mount_options() requires that.
@@ -1683,7 +1620,7 @@ void set_fs_pwd(struct fs_struct *fs, struct path *path)
 		path_put(&old_pwd);
 }
 
-static void chroot_fs_refs(struct nameidata *old_nd, struct nameidata *new_nd)
+static void chroot_fs_refs(struct path *old_root, struct path *new_root)
 {
 	struct task_struct *g, *p;
 	struct fs_struct *fs;
@@ -1695,12 +1632,12 @@ static void chroot_fs_refs(struct nameidata *old_nd, struct nameidata *new_nd)
 		if (fs) {
 			atomic_inc(&fs->count);
 			task_unlock(p);
-			if (fs->root.dentry == old_nd->path.dentry
-			    && fs->root.mnt == old_nd->path.mnt)
-				set_fs_root(fs, &new_nd->path);
-			if (fs->pwd.dentry == old_nd->path.dentry
-			    && fs->pwd.mnt == old_nd->path.mnt)
-				set_fs_pwd(fs, &new_nd->path);
+			if (fs->root.dentry == old_root->dentry
+			    && fs->root.mnt == old_root->mnt)
+				set_fs_root(fs, new_root);
+			if (fs->pwd.dentry == old_root->dentry
+			    && fs->pwd.mnt == old_root->mnt)
+				set_fs_pwd(fs, new_root);
 			put_fs_struct(fs);
 		} else
 			task_unlock(p);
@@ -1737,7 +1674,8 @@ asmlinkage long sys_pivot_root(const char __user * new_root,
 			       const char __user * put_old)
 {
 	struct vfsmount *tmp;
-	struct nameidata new_nd, old_nd, parent_nd, root_parent, user_nd;
+	struct nameidata new_nd, old_nd, user_nd;
+	struct path parent_path, root_parent;
 	int error;
 
 	if (!capable(CAP_SYS_ADMIN))
@@ -1811,19 +1749,19 @@ asmlinkage long sys_pivot_root(const char __user * new_root,
 			goto out3;
 	} else if (!is_subdir(old_nd.path.dentry, new_nd.path.dentry))
 		goto out3;
-	detach_mnt(new_nd.path.mnt, &parent_nd);
+	detach_mnt(new_nd.path.mnt, &parent_path);
 	detach_mnt(user_nd.path.mnt, &root_parent);
 	/* mount old root on put_old */
-	attach_mnt(user_nd.path.mnt, &old_nd);
+	attach_mnt(user_nd.path.mnt, &old_nd.path);
 	/* mount new_root on / */
 	attach_mnt(new_nd.path.mnt, &root_parent);
 	touch_mnt_namespace(current->nsproxy->mnt_ns);
 	spin_unlock(&vfsmount_lock);
-	chroot_fs_refs(&user_nd, &new_nd);
+	chroot_fs_refs(&user_nd.path, &new_nd.path);
 	security_sb_post_pivotroot(&user_nd, &new_nd);
 	error = 0;
-	path_put(&root_parent.path);
-	path_put(&parent_nd.path);
+	path_put(&root_parent);
+	path_put(&parent_path);
 out2:
 	mutex_unlock(&old_nd.path.dentry->d_inode->i_mutex);
 	up_write(&namespace_sem);