1 files changed, 45 insertions, 25 deletions

diff --git a/fs/super.c b/fs/super.c
index afd0f1a..de41e1e 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -136,12 +136,13 @@ static struct super_block *alloc_super(struct file_system_type *type)
 		INIT_LIST_HEAD(&s->s_files);
 #endif
 		s->s_bdi = &default_backing_dev_info;
-		INIT_LIST_HEAD(&s->s_instances);
+		INIT_HLIST_NODE(&s->s_instances);
 		INIT_HLIST_BL_HEAD(&s->s_anon);
 		INIT_LIST_HEAD(&s->s_inodes);
 		INIT_LIST_HEAD(&s->s_dentry_lru);
 		INIT_LIST_HEAD(&s->s_inode_lru);
 		spin_lock_init(&s->s_inode_lru_lock);
+		INIT_LIST_HEAD(&s->s_mounts);
 		init_rwsem(&s->s_umount);
 		mutex_init(&s->s_lock);
 		lockdep_set_class(&s->s_umount, &type->s_umount_key);
@@ -200,6 +201,7 @@ static inline void destroy_super(struct super_block *s)
 	free_percpu(s->s_files);
 #endif
 	security_sb_free(s);
+	WARN_ON(!list_empty(&s->s_mounts));
 	kfree(s->s_subtype);
 	kfree(s->s_options);
 	kfree(s);
@@ -210,7 +212,7 @@ static inline void destroy_super(struct super_block *s)
 /*
  * Drop a superblock's refcount.  The caller must hold sb_lock.
  */
-void __put_super(struct super_block *sb)
+static void __put_super(struct super_block *sb)
 {
 	if (!--sb->s_count) {
 		list_del_init(&sb->s_list);
@@ -225,7 +227,7 @@ void __put_super(struct super_block *sb)
  *	Drops a temporary reference, frees superblock if there's no
  *	references left.
  */
-void put_super(struct super_block *sb)
+static void put_super(struct super_block *sb)
 {
 	spin_lock(&sb_lock);
 	__put_super(sb);
@@ -328,7 +330,7 @@ static int grab_super(struct super_block *s) __releases(sb_lock)
 bool grab_super_passive(struct super_block *sb)
 {
 	spin_lock(&sb_lock);
-	if (list_empty(&sb->s_instances)) {
+	if (hlist_unhashed(&sb->s_instances)) {
 		spin_unlock(&sb_lock);
 		return false;
 	}
@@ -337,7 +339,7 @@ bool grab_super_passive(struct super_block *sb)
 	spin_unlock(&sb_lock);
 
 	if (down_read_trylock(&sb->s_umount)) {
-		if (sb->s_root)
+		if (sb->s_root && (sb->s_flags & MS_BORN))
 			return true;
 		up_read(&sb->s_umount);
 	}
@@ -400,7 +402,7 @@ void generic_shutdown_super(struct super_block *sb)
 	}
 	spin_lock(&sb_lock);
 	/* should be initialized for __put_super_and_need_restart() */
-	list_del_init(&sb->s_instances);
+	hlist_del_init(&sb->s_instances);
 	spin_unlock(&sb_lock);
 	up_write(&sb->s_umount);
 }
@@ -420,13 +422,14 @@ struct super_block *sget(struct file_system_type *type,
 			void *data)
 {
 	struct super_block *s = NULL;
+	struct hlist_node *node;
 	struct super_block *old;
 	int err;
 
 retry:
 	spin_lock(&sb_lock);
 	if (test) {
-		list_for_each_entry(old, &type->fs_supers, s_instances) {
+		hlist_for_each_entry(old, node, &type->fs_supers, s_instances) {
 			if (!test(old, data))
 				continue;
 			if (!grab_super(old))
@@ -462,7 +465,7 @@ retry:
 	s->s_type = type;
 	strlcpy(s->s_id, type->name, sizeof(s->s_id));
 	list_add_tail(&s->s_list, &super_blocks);
-	list_add(&s->s_instances, &type->fs_supers);
+	hlist_add_head(&s->s_instances, &type->fs_supers);
 	spin_unlock(&sb_lock);
 	get_filesystem(type);
 	register_shrinker(&s->s_shrink);
@@ -497,14 +500,14 @@ void sync_supers(void)
 
 	spin_lock(&sb_lock);
 	list_for_each_entry(sb, &super_blocks, s_list) {
-		if (list_empty(&sb->s_instances))
+		if (hlist_unhashed(&sb->s_instances))
 			continue;
 		if (sb->s_op->write_super && sb->s_dirt) {
 			sb->s_count++;
 			spin_unlock(&sb_lock);
 
 			down_read(&sb->s_umount);
-			if (sb->s_root && sb->s_dirt)
+			if (sb->s_root && sb->s_dirt && (sb->s_flags & MS_BORN))
 				sb->s_op->write_super(sb);
 			up_read(&sb->s_umount);
 
@@ -533,13 +536,13 @@ void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
 
 	spin_lock(&sb_lock);
 	list_for_each_entry(sb, &super_blocks, s_list) {
-		if (list_empty(&sb->s_instances))
+		if (hlist_unhashed(&sb->s_instances))
 			continue;
 		sb->s_count++;
 		spin_unlock(&sb_lock);
 
 		down_read(&sb->s_umount);
-		if (sb->s_root)
+		if (sb->s_root && (sb->s_flags & MS_BORN))
 			f(sb, arg);
 		up_read(&sb->s_umount);
 
@@ -566,14 +569,15 @@ void iterate_supers_type(struct file_system_type *type,
 	void (*f)(struct super_block *, void *), void *arg)
 {
 	struct super_block *sb, *p = NULL;
+	struct hlist_node *node;
 
 	spin_lock(&sb_lock);
-	list_for_each_entry(sb, &type->fs_supers, s_instances) {
+	hlist_for_each_entry(sb, node, &type->fs_supers, s_instances) {
 		sb->s_count++;
 		spin_unlock(&sb_lock);
 
 		down_read(&sb->s_umount);
-		if (sb->s_root)
+		if (sb->s_root && (sb->s_flags & MS_BORN))
 			f(sb, arg);
 		up_read(&sb->s_umount);
 
@@ -607,14 +611,14 @@ struct super_block *get_super(struct block_device *bdev)
 	spin_lock(&sb_lock);
 rescan:
 	list_for_each_entry(sb, &super_blocks, s_list) {
-		if (list_empty(&sb->s_instances))
+		if (hlist_unhashed(&sb->s_instances))
 			continue;
 		if (sb->s_bdev == bdev) {
 			sb->s_count++;
 			spin_unlock(&sb_lock);
 			down_read(&sb->s_umount);
 			/* still alive? */
-			if (sb->s_root)
+			if (sb->s_root && (sb->s_flags & MS_BORN))
 				return sb;
 			up_read(&sb->s_umount);
 			/* nope, got unmounted */
@@ -647,7 +651,7 @@ struct super_block *get_active_super(struct block_device *bdev)
 restart:
 	spin_lock(&sb_lock);
 	list_for_each_entry(sb, &super_blocks, s_list) {
-		if (list_empty(&sb->s_instances))
+		if (hlist_unhashed(&sb->s_instances))
 			continue;
 		if (sb->s_bdev == bdev) {
 			if (grab_super(sb)) /* drops sb_lock */
@@ -667,14 +671,14 @@ struct super_block *user_get_super(dev_t dev)
 	spin_lock(&sb_lock);
 rescan:
 	list_for_each_entry(sb, &super_blocks, s_list) {
-		if (list_empty(&sb->s_instances))
+		if (hlist_unhashed(&sb->s_instances))
 			continue;
 		if (sb->s_dev ==  dev) {
 			sb->s_count++;
 			spin_unlock(&sb_lock);
 			down_read(&sb->s_umount);
 			/* still alive? */
-			if (sb->s_root)
+			if (sb->s_root && (sb->s_flags & MS_BORN))
 				return sb;
 			up_read(&sb->s_umount);
 			/* nope, got unmounted */
@@ -719,23 +723,29 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 	/* If we are remounting RDONLY and current sb is read/write,
 	   make sure there are no rw files opened */
 	if (remount_ro) {
-		if (force)
+		if (force) {
 			mark_files_ro(sb);
-		else if (!fs_may_remount_ro(sb))
-			return -EBUSY;
+		} else {
+			retval = sb_prepare_remount_readonly(sb);
+			if (retval)
+				return retval;
+		}
 	}
 
 	if (sb->s_op->remount_fs) {
 		retval = sb->s_op->remount_fs(sb, &flags, data);
 		if (retval) {
 			if (!force)
-				return retval;
+				goto cancel_readonly;
 			/* If forced remount, go ahead despite any errors */
 			WARN(1, "forced remount of a %s fs returned %i\n",
 			     sb->s_type->name, retval);
 		}
 	}
 	sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
+	/* Needs to be ordered wrt mnt_is_readonly() */
+	smp_wmb();
+	sb->s_readonly_remount = 0;
 
 	/*
 	 * Some filesystems modify their metadata via some other path than the
@@ -748,6 +758,10 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 	if (remount_ro && sb->s_bdev)
 		invalidate_bdev(sb->s_bdev);
 	return 0;
+
+cancel_readonly:
+	sb->s_readonly_remount = 0;
+	return retval;
 }
 
 static void do_emergency_remount(struct work_struct *work)
@@ -756,12 +770,13 @@ static void do_emergency_remount(struct work_struct *work)
 
 	spin_lock(&sb_lock);
 	list_for_each_entry(sb, &super_blocks, s_list) {
-		if (list_empty(&sb->s_instances))
+		if (hlist_unhashed(&sb->s_instances))
 			continue;
 		sb->s_count++;
 		spin_unlock(&sb_lock);
 		down_write(&sb->s_umount);
-		if (sb->s_root && sb->s_bdev && !(sb->s_flags & MS_RDONLY)) {
+		if (sb->s_root && sb->s_bdev && (sb->s_flags & MS_BORN) &&
+		    !(sb->s_flags & MS_RDONLY)) {
 			/*
 			 * What lock protects sb->s_flags??
 			 */
@@ -1144,6 +1159,11 @@ int freeze_super(struct super_block *sb)
 		return -EBUSY;
 	}
 
+	if (!(sb->s_flags & MS_BORN)) {
+		up_write(&sb->s_umount);
+		return 0;	/* sic - it's "nothing to do" */
+	}
+
 	if (sb->s_flags & MS_RDONLY) {
 		sb->s_frozen = SB_FREEZE_TRANS;
 		smp_wmb();