[dm-devel] [PATCH 3/4] btrfs: zoned: fail mount if the device does not support zone append

[hch at infradead.org]

On Mon, Apr 19, 2021 at 09:35:37AM +0000, Damien Le Moal wrote:
> This is only to avoid someone from running zoned-btrfs on top of dm-crypt.
> Without this patch, mount will be OK and file data writes will also actually be
> OK. But all reads will miserably fail... I would rather have this patch in than
> deal with the "bug reports" about btrfs failing to read files. No ?
> 
> Note that like you, I dislike having to add such code. But it was my oversight
> when I worked on getting dm-crypt to work on zoned drives. Zone append was
> overlooked at that time... My bad, really.

dm-crypt needs to stop pretending it supports zoned devices if it
doesn't.  Note that dm-crypt could fairly trivially support zone append
by doing the same kind of emulation that the sd driver does.