I want to convert my existing full-disk btrfs (unpartitioned) filesystems to bcache.
To do so, I need to move data around and reformat the drives.
I have enough hdd space to do it in a couple steps (that will probably take several days, going to reformat 36TB raw total).

Since I'm using btrfs, I thought btrfs send and btrfs receive would make this easy.

I have created a readonly snapshot of the fs I want to convert first and started sending it into a subvolume in another fs.

What I'm unclear about is how I would go about restoring that duplicated subvolume to the original disk once my superblock conversions have taken place.

The btrfs receive manpage indicates that it can only create new subvolumes and it also makes them readonly once the process is complete.

So how do I replace a fresh writable root subvolume from a received snapshot?

I want to convert my existing full-disk btrfs (unpartitioned) filesystems to bcache.
To do so, I need to move data around and reformat the drives.
I have enough hdd space to do it in a couple steps.

Since I'm using btrfs, I thought btrfs send and btrfs receive would make this easy.

I have created a readonly snapshot of the fs I want to convert first and started sending it into a subvolume in another fs.

What I'm unclear about is how I would go about restoring that duplicated subvolume to the original disk once my superblock conversions have taken place.

The btrfs receive manpage indicates that it can only create new subvolumes and it also makes them readonly once the process is complete.

So how do I replace a fresh writable root subvolume from a received snapshot?