[PATCH] (1/4) ->kill_sb() switchover

New method - ->kill_sb().  It will eventually replace current
fs/super.c::shutdown_super() - i.e. it's called when fs driver
must shut the superblock down, remove it from all lists, etc.

fs/super.c

@@ -459,7 +459,10 @@ void kill_super(struct super_block *sb)
 		return;
 
 	down_write(&sb->s_umount);
-	shutdown_super(sb);
+	if (fs->kill_sb)
+		fs->kill_sb(sb);
+	else
+		shutdown_super(sb);
 	put_filesystem(fs);
 }
 
@@ -682,6 +685,22 @@ struct super_block *get_anon_super(struct file_system_type *type,
 	insert_super(s, type);
 	return s;
 }
+ 
+void kill_anon_super(struct super_block *sb)
+{
+	int slot = minor(sb->s_dev);
+	generic_shutdown_super(sb);
+	spin_lock(&unnamed_dev_lock);
+	clear_bit(slot, unnamed_dev_in_use);
+	spin_unlock(&unnamed_dev_lock);
+}
+
+void kill_litter_super(struct super_block *sb)
+{
+	if (sb->s_root)
+		d_genocide(sb->s_root);
+	kill_anon_super(sb);
+}
 
 struct super_block *get_sb_bdev(struct file_system_type *fs_type,
 	int flags, char *dev_name, void * data,
@@ -783,6 +802,14 @@ struct super_block *get_sb_bdev(struct file_system_type *fs_type,
 	return ERR_PTR(error);
 }
 
+void kill_block_super(struct super_block *sb)
+{
+	struct block_device *bdev = sb->s_bdev;
+	generic_shutdown_super(sb);
+	bd_release(bdev);
+	blkdev_put(bdev, BDEV_FS);
+}
+
 struct super_block *get_sb_nodev(struct file_system_type *fs_type,
 	int flags, void *data,
 	int (*fill_super)(struct super_block *, void *, int))

include/linux/fs.h

@@ -944,6 +944,7 @@ struct file_system_type {
 	const char *name;
 	int fs_flags;
 	struct super_block *(*get_sb) (struct file_system_type *, int, char *, void *);
+	void (*kill_sb) (struct super_block *);
 	struct module *owner;
 	struct file_system_type * next;
 	struct list_head fs_supers;
@@ -958,6 +959,9 @@ struct super_block *get_sb_single(struct file_system_type *fs_type,
 struct super_block *get_sb_nodev(struct file_system_type *fs_type,
 	int flags, void *data,
 	int (*fill_super)(struct super_block *, void *, int));
+void kill_block_super(struct super_block *sb);
+void kill_anon_super(struct super_block *sb);
+void kill_litter_super(struct super_block *sb);
 
 /* Alas, no aliases. Too much hassle with bringing module.h everywhere */
 #define fops_get(fops) \

kernel/ksyms.c

@@ -286,8 +286,11 @@ EXPORT_SYMBOL(dcache_readdir);
 EXPORT_SYMBOL(fd_install);
 EXPORT_SYMBOL(put_unused_fd);
 EXPORT_SYMBOL(get_sb_bdev);
+EXPORT_SYMBOL(kill_block_super);
 EXPORT_SYMBOL(get_sb_nodev);
 EXPORT_SYMBOL(get_sb_single);
+EXPORT_SYMBOL(kill_anon_super);
+EXPORT_SYMBOL(kill_litter_super);
 
 /* for stackable file systems (lofs, wrapfs, cryptfs, etc.) */
 EXPORT_SYMBOL(default_llseek);