Re: [PATCH 0/3] btrfs-progs: rescue: Add create-control-device subcommand

[David Sterba <dsterba@suse.cz>]

On Thu, Oct 29, 2020 at 04:17:35PM -0700, Daniel Xu wrote:
> This patchset adds a new `btrfs rescue create-control-device` subcommand
> that acts as a convenient way to invoke:
> 
> 	# mknod --mode=600 c 10 234 /dev/btrfs-control
> 
> on systems that don't have `mknod` installed or when you're lazy.

Well, I don't think the part 'lazy' applies.

The whole thing with the control device is simpler that I originally
thought. On a system without loaded btrfs module there's no
/dev/btrfs-control. This is correct because the device node is created
at load time or when btrfs_interface_init is called.

Creating just the device node makes no sense because there's nothing
handling it. Once module is loaded it appears and works as expected.

The only case where the rescue command makes sense is when the module is
loaded, device node creatd and then manually deleted. This is possible
but highly unlikely. For that reason the rescue command still has some
sense but the reasoning needs to reflect how it's related to the module
status.

As this is docs update only, I'll fix that myself, no need to resend.