SPDX-License-Identifier: GPL-2.0
aufs5.x-rcN loopback patch

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 39d539df0349d..4109efe2f6a3a 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -646,6 +646,15 @@ 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)
 {
@@ -701,6 +710,7 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
 			  unsigned int arg)
 {
 	struct file	*file = NULL, *old_file;
+	struct file	*f, *virt_file = NULL, *old_virt_file;
 	int		error;
 	bool		partscan;
 
@@ -720,12 +730,19 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
 	file = fget(arg);
 	if (!file)
 		goto out_err;
+	f = loop_real_file(file);
+	if (f) {
+		virt_file = file;
+		file = f;
+		get_file(file);
+	}
 
 	error = loop_validate_file(file, bdev);
 	if (error)
 		goto out_err;
 
 	old_file = lo->lo_backing_file;
+	old_virt_file = lo->lo_backing_virt_file;
 
 	error = -EINVAL;
 
@@ -737,6 +754,7 @@ 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));
@@ -750,6 +768,8 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
 	 * dependency.
 	 */
 	fput(old_file);
+	if (old_virt_file)
+		fput(old_virt_file);
 	if (partscan)
 		loop_reread_partitions(lo, bdev);
 	return 0;
@@ -758,6 +778,8 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
 	mutex_unlock(&loop_ctl_mutex);
 	if (file)
 		fput(file);
+	if (virt_file)
+		fput(virt_file);
 	return error;
 }
 
@@ -1084,7 +1106,7 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
 			  struct block_device *bdev,
 			  const struct loop_config *config)
 {
-	struct file	*file;
+	struct file	*file, *f, *virt_file = NULL;
 	struct inode	*inode;
 	struct address_space *mapping;
 	int		error;
@@ -1099,6 +1121,12 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
 	file = fget(config->fd);
 	if (!file)
 		goto out;
+	f = loop_real_file(file);
+	if (f) {
+		virt_file = file;
+		file = f;
+		get_file(file);
+	}
 
 	/*
 	 * If we don't hold exclusive handle for the device, upgrade to it
@@ -1153,6 +1181,7 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
 	lo->use_dio = lo->lo_flags & LO_FLAGS_DIRECT_IO;
 	lo->lo_device = bdev;
 	lo->lo_backing_file = file;
+	lo->lo_backing_virt_file = virt_file;
 	lo->old_gfp_mask = mapping_gfp_mask(mapping);
 	mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
 
@@ -1203,6 +1232,8 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
 		bd_abort_claiming(bdev, loop_configure);
 out_putf:
 	fput(file);
+	if (virt_file)
+		fput(virt_file);
 out:
 	/* This is safe: open() is still holding a reference. */
 	module_put(THIS_MODULE);
@@ -1212,6 +1243,7 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
 static int __loop_clr_fd(struct loop_device *lo, bool release)
 {
 	struct file *filp = NULL;
+	struct file *virt_filp = lo->lo_backing_virt_file;
 	gfp_t gfp = lo->old_gfp_mask;
 	struct block_device *bdev = lo->lo_device;
 	int err = 0;
@@ -1235,6 +1267,7 @@ static int __loop_clr_fd(struct loop_device *lo, bool release)
 
 	spin_lock_irq(&lo->lo_lock);
 	lo->lo_backing_file = NULL;
+	lo->lo_backing_virt_file = NULL;
 	spin_unlock_irq(&lo->lo_lock);
 
 	loop_release_xfer(lo);
@@ -1317,6 +1350,8 @@ static int __loop_clr_fd(struct loop_device *lo, bool release)
 	 */
 	if (filp)
 		fput(filp);
+	if (virt_filp)
+		fput(virt_filp);
 	return err;
 }
 
diff --git a/drivers/block/loop.h b/drivers/block/loop.h
index af75a5ee40944..1d847cb194ff6 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 5ef279a59bb14..6447c37f98756 100644
--- a/fs/aufs/f_op.c
+++ b/fs/aufs/f_op.c
@@ -304,7 +304,7 @@ 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 a8b63acc62045..9d97c3af5686a 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);
 	au_kfree_try_rcu(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 94f4f80ae33bf..ca1194354aff4 100644
--- a/fs/aufs/loop.h
+++ b/fs/aufs/loop.h
@@ -26,6 +26,8 @@ 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, struct super_block *sb)
 
@@ -36,6 +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 589dd01220201..801e0a7faec59 100644
--- a/fs/aufs/super.c
+++ b/fs/aufs/super.c
@@ -844,7 +844,10 @@ 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 91f3fbe5b57ff..ad1b2e44d538b 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1965,6 +1965,10 @@ struct super_operations {
 				  struct shrink_control *);
 	long (*free_cached_objects)(struct super_block *,
 				    struct shrink_control *);
+#if IS_ENABLED(CONFIG_BLK_DEV_LOOP) || IS_ENABLED(CONFIG_BLK_DEV_LOOP_MODULE)
+	/* and aufs */
+	struct file *(*real_loop)(struct file *);
+#endif
 };
 
 /*