SPDX-License-Identifier: GPL-2.0
aufs4.15 loopback patch

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index c292afa..a93038c 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -600,6 +600,15 @@ static inline void loop_update_dio(struct loop_device *lo)
 			lo->use_dio);
 }
 
+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,
 				   struct block_device *bdev)
 {
@@ -634,6 +643,7 @@ 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;
 
@@ -650,9 +660,16 @@ 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;
 
@@ -667,6 +684,7 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
 	blk_mq_freeze_queue(lo->lo_queue);
 	mapping_set_gfp_mask(old_file->f_mapping, lo->old_gfp_mask);
 	lo->lo_backing_file = file;
+	lo->lo_backing_virt_file = virt_file;
 	lo->old_gfp_mask = mapping_gfp_mask(file->f_mapping);
 	mapping_set_gfp_mask(file->f_mapping,
 			     lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
@@ -674,12 +692,16 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
 	blk_mq_unfreeze_queue(lo->lo_queue);
 
 	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;
 }
@@ -873,7 +895,7 @@ 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;
 	int		lo_flags = 0;
@@ -887,6 +909,12 @@ 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)
@@ -935,6 +963,7 @@ 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;
@@ -968,6 +997,8 @@ 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);
@@ -1014,6 +1045,7 @@ 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;
 
@@ -1045,6 +1077,7 @@ 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);
@@ -1092,6 +1125,8 @@ 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 0f45416..101f193 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;
 	void		*key_data; 
 
diff --git a/fs/aufs/f_op.c b/fs/aufs/f_op.c
index 0d4ea929..af293c2 100644
--- a/fs/aufs/f_op.c
+++ b/fs/aufs/f_op.c
@@ -358,7 +358,7 @@ 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 3b217c2..0f5ab22 100644
--- a/fs/aufs/loop.c
+++ b/fs/aufs/loop.c
@@ -133,3 +133,19 @@ 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 7d7bf34..ba7c188 100644
--- a/fs/aufs/loop.h
+++ b/fs/aufs/loop.h
@@ -26,7 +26,11 @@ 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)
@@ -34,6 +38,8 @@ 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 357bf04..c6614df 100644
--- a/fs/aufs/super.c
+++ b/fs/aufs/super.c
@@ -839,7 +839,10 @@ 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 96e05b3..ba5e627 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1840,6 +1840,10 @@ 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
 };
 
 /*