Re: [PATCH 0/2] btrfs-progs: add check and repair ability for super num devices mismatch

[David Sterba <dsterba@suse.cz>]

On Mon, Feb 28, 2022 at 08:50:06AM +0800, Qu Wenruo wrote:
> The patchset can be fetched from github:
> https://github.com/adam900710/btrfs-progs/tree/super_num_devs
> 
> The 2nd patch contains a compressed raw image, thus it may be a little
> too large for the mail list.
> 
> This patchset will allow btrfs check to detect and repair super num devices
> mismatch.
> 
> The detect part is to iterate through chunk tree to grab the correct
> number of devices.
> This is more reliable than counting devices in fs_devices, since seed
> device is in another fs_devices.
> 
> The repair is more straightforward, just reset the value in superblock
> and commit a transaction.

As repair it should work and be safe, also it should be reasonably safe
to be part of --repair. In addition to that we may also want the rescue
subcommand as it's meant to be for such one-time fixes for specific
errors.