[PATCH btrfs-progs] btrfs-progs: do not fail when offset of a ROOT_ITEM is not -1

[David Sterba]

On Tue, Feb 09, 2021 at 06:34:06PM +0100, Marek Behún wrote:
> When the btrfs_read_fs_root() function is searching a ROOT_ITEM with
> location key offset other than -1, it currently fails via BUG_ON.
> 
> The offset can have other value than -1, though. This can happen for
> example if a subvolume is renamed:
> 
>   $ btrfs subvolume create X && sync
>   Create subvolume './X'
>   $ btrfs inspect-internal dump-tree /dev/root | grep -B 2 'name: X$
>         location key (270 ROOT_ITEM 18446744073709551615) type DIR
>         transid 283 data_len 0 name_len 1
>         name: X
>   $ mv X Y && sync
>   $ btrfs inspect-internal dump-tree /dev/root | grep -B 2 'name: Y$
>         location key (270 ROOT_ITEM 0) type DIR
>         transid 285 data_len 0 name_len 1
>         name: Y
> 
> As can be seen the offset changed from -1ULL to 0.
> 
> Do not fail in this case.
> 
> Signed-off-by: Marek Behún <marek.behun at nic.cz>
> Cc: David Sterba <dsterba at suse.com>
> Cc: Qu Wenruo <wqu at suse.com>
> Cc: Tom Rini <trini at konsulko.com>

Added to devel, thanks.