aufs4.13 loopback patch

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 10707c3..af32e47 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -547,7 +547,7 @@ static int do_req_filebacked(struct loop_device *lo, struct request *rq)
 }
 
 struct switch_request {
-	struct file *file;
+	struct file *file, *virt_file;
 	struct completion wait;
 };
 
@@ -573,6 +573,7 @@ static void do_loop_switch(struct loop_device *lo, struct switch_request *p)
 	mapping = file->f_mapping;
 	mapping_set_gfp_mask(old_file->f_mapping, lo->old_gfp_mask);
 	lo->lo_backing_file = file;
+	lo->lo_backing_virt_file = p->virt_file;
 	lo->lo_blocksize = S_ISBLK(mapping->host->i_mode) ?
 		mapping->host->i_bdev->bd_block_size : PAGE_SIZE;
 	lo->old_gfp_mask = mapping_gfp_mask(mapping);
@@ -585,11 +586,13 @@ static void do_loop_switch(struct loop_device *lo, struct switch_request *p)
  * First it needs to flush existing IO, it does this by sending a magic
  * BIO down the pipe. The completion of this BIO does the actual switch.
  */
-static int loop_switch(struct loop_device *lo, struct file *file)
+static int loop_switch(struct loop_device *lo, struct file *file,
+		       struct file *virt_file)
 {
 	struct switch_request w;
 
 	w.file = file;
+	w.virt_file = virt_file;
 
 	/* freeze queue and wait for completion of scheduled requests */
 	blk_mq_freeze_queue(lo->lo_queue);
@@ -611,7 +614,16 @@ static int loop_flush(struct loop_device *lo)
 	/* loop not yet configured, no running thread, nothing to flush */
 	if (lo->lo_state != Lo_bound)
 		return 0;
-	return loop_switch(lo, NULL);
+	return loop_switch(lo, NULL, NULL);
+}
+
+static struct file *loop_real_file(struct file *file)
+{
+	struct file *f = NULL;
+
+	if (file->f_path.dentry->d_sb->s_op->real_loop)
+		f = file->f_path.dentry->d_sb->s_op->real_loop(file);
+	return f;
 }
 
 static void loop_reread_partitions(struct loop_device *lo,
@@ -648,6 +660,7 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
 			  unsigned int arg)
 {
 	struct file	*file, *old_file;
+	struct file	*f, *virt_file = NULL, *old_virt_file;
 	struct inode	*inode;
 	int		error;
 
@@ -664,9 +677,16 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
 	file = fget(arg);
 	if (!file)
 		goto out;
+	f = loop_real_file(file);
+	if (f) {
+		virt_file = file;
+		file = f;
+		get_file(file);
+	}
 
 	inode = file->f_mapping->host;
 	old_file = lo->lo_backing_file;
+	old_virt_file = lo->lo_backing_virt_file;
 
 	error = -EINVAL;
 
@@ -678,17 +698,21 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
 		goto out_putf;
 
 	/* and ... switch */
-	error = loop_switch(lo, file);
+	error = loop_switch(lo, file, virt_file);
 	if (error)
 		goto out_putf;
 
 	fput(old_file);
+	if (old_virt_file)
+		fput(old_virt_file);
 	if (lo->lo_flags & LO_FLAGS_PARTSCAN)
 		loop_reread_partitions(lo, bdev);
 	return 0;
 
  out_putf:
 	fput(file);
+	if (virt_file)
+		fput(virt_file);
  out:
 	return error;
 }
@@ -882,7 +906,7 @@ static int loop_prepare_queue(struct loop_device *lo)
 static int loop_set_fd(struct loop_device *lo, fmode_t mode,
 		       struct block_device *bdev, unsigned int arg)
 {
-	struct file	*file, *f;
+	struct file	*file, *f, *virt_file = NULL;
 	struct inode	*inode;
 	struct address_space *mapping;
 	unsigned lo_blocksize;
@@ -897,6 +921,12 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
 	file = fget(arg);
 	if (!file)
 		goto out;
+	f = loop_real_file(file);
+	if (f) {
+		virt_file = file;
+		file = f;
+		get_file(file);
+	}
 
 	error = -EBUSY;
 	if (lo->lo_state != Lo_unbound)
@@ -949,6 +979,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
 	lo->lo_device = bdev;
 	lo->lo_flags = lo_flags;
 	lo->lo_backing_file = file;
+	lo->lo_backing_virt_file = virt_file;
 	lo->transfer = NULL;
 	lo->ioctl = NULL;
 	lo->lo_sizelimit = 0;
@@ -981,6 +1012,8 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
 
  out_putf:
 	fput(file);
+	if (virt_file)
+		fput(virt_file);
  out:
 	/* This is safe: open() is still holding a reference. */
 	module_put(THIS_MODULE);
@@ -1027,6 +1060,7 @@ loop_init_xfer(struct loop_device *lo, struct loop_func_table *xfer,
 static int loop_clr_fd(struct loop_device *lo)
 {
 	struct file *filp = lo->lo_backing_file;
+	struct file *virt_filp = lo->lo_backing_virt_file;
 	gfp_t gfp = lo->old_gfp_mask;
 	struct block_device *bdev = lo->lo_device;
 
@@ -1058,6 +1092,7 @@ static int loop_clr_fd(struct loop_device *lo)
 	spin_lock_irq(&lo->lo_lock);
 	lo->lo_state = Lo_rundown;
 	lo->lo_backing_file = NULL;
+	lo->lo_backing_virt_file = NULL;
 	spin_unlock_irq(&lo->lo_lock);
 
 	loop_release_xfer(lo);
@@ -1102,6 +1137,8 @@ static int loop_clr_fd(struct loop_device *lo)
 	 * bd_mutex which is usually taken before lo_ctl_mutex.
 	 */
 	fput(filp);
+	if (virt_filp)
+		fput(virt_filp);
 	return 0;
 }
 
diff --git a/drivers/block/loop.h b/drivers/block/loop.h
index fecd3f9..6b3a7c9 100644
--- a/drivers/block/loop.h
+++ b/drivers/block/loop.h
@@ -46,7 +46,7 @@ struct loop_device {
 	int		(*ioctl)(struct loop_device *, int cmd, 
 				 unsigned long arg); 
 
-	struct file *	lo_backing_file;
+	struct file *	lo_backing_file, *lo_backing_virt_file;
 	struct block_device *lo_device;
 	unsigned	lo_blocksize;
 	void		*key_data; 
diff --git a/fs/aufs/f_op.c b/fs/aufs/f_op.c
index 8aff060..e853272 100644
--- a/fs/aufs/f_op.c
+++ b/fs/aufs/f_op.c
@@ -357,7 +357,7 @@ static ssize_t aufs_read_iter(struct kiocb *kio, struct iov_iter *iov_iter)
 	if (IS_ERR(h_file))
 		goto out;
 
-	if (au_test_loopback_kthread()) {
+	if (0 && au_test_loopback_kthread()) {
 		au_warn_loopback(h_file->f_path.dentry->d_sb);
 		if (file->f_mapping != h_file->f_mapping) {
 			file->f_mapping = h_file->f_mapping;
diff --git a/fs/aufs/loop.c b/fs/aufs/loop.c
index e35f015..b37f1ae 100644
--- a/fs/aufs/loop.c
+++ b/fs/aufs/loop.c
@@ -132,3 +132,19 @@ void au_loopback_fin(void)
 		symbol_put(loop_backing_file);
 	kfree(au_warn_loopback_array);
 }
+
+/* ---------------------------------------------------------------------- */
+
+/* support the loopback block device insude aufs */
+
+struct file *aufs_real_loop(struct file *file)
+{
+	struct file *f;
+
+	BUG_ON(!au_test_aufs(file->f_path.dentry->d_sb));
+	fi_read_lock(file);
+	f = au_hf_top(file);
+	fi_read_unlock(file);
+	AuDebugOn(!f);
+	return f;
+}
diff --git a/fs/aufs/loop.h b/fs/aufs/loop.h
index e2df495..36e5052 100644
--- a/fs/aufs/loop.h
+++ b/fs/aufs/loop.h
@@ -25,7 +25,11 @@ void au_warn_loopback(struct super_block *h_sb);
 
 int au_loopback_init(void);
 void au_loopback_fin(void);
+
+struct file *aufs_real_loop(struct file *file);
 #else
+AuStub(struct file *, loop_backing_file, return NULL)
+
 AuStubInt0(au_test_loopback_overlap, struct super_block *sb,
 	   struct dentry *h_adding)
 AuStubInt0(au_test_loopback_kthread, void)
@@ -33,6 +37,8 @@ AuStubVoid(au_warn_loopback, struct super_block *h_sb)
 
 AuStubInt0(au_loopback_init, void)
 AuStubVoid(au_loopback_fin, void)
+
+AuStub(struct file *, aufs_real_loop, return NULL, struct file *file)
 #endif /* BLK_DEV_LOOP */
 
 #endif /* __KERNEL__ */
diff --git a/fs/aufs/super.c b/fs/aufs/super.c
index 3c300125..128d790 100644
--- a/fs/aufs/super.c
+++ b/fs/aufs/super.c
@@ -838,7 +838,10 @@ static const struct super_operations aufs_sop = {
 	.statfs		= aufs_statfs,
 	.put_super	= aufs_put_super,
 	.sync_fs	= aufs_sync_fs,
-	.remount_fs	= aufs_remount_fs
+	.remount_fs	= aufs_remount_fs,
+#ifdef CONFIG_AUFS_BDEV_LOOP
+	.real_loop	= aufs_real_loop
+#endif
 };
 
 /* ---------------------------------------------------------------------- */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 9b21bb5..f7124fa 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1814,6 +1814,10 @@ struct super_operations {
 				  struct shrink_control *);
 	long (*free_cached_objects)(struct super_block *,
 				    struct shrink_control *);
+#if defined(CONFIG_BLK_DEV_LOOP) ||  defined(CONFIG_BLK_DEV_LOOP_MODULE)
+	/* and aufs */
+	struct file *(*real_loop)(struct file *);
+#endif
 };
 
 /*