Re: [PATCH 4/6] btrfs-progs: Add freespace tree as compat_ro supported feature

[Omar Sandoval <osandov@osandov.com>]

On Fri, Jun 15, 2018 at 02:06:00PM +0300, Nikolay Borisov wrote:
> The RO_FREE_SPACE_TREE(_VALID) flags are required in order to be able
> to open an FST filesystem in repair mode. Add them to
> BTRFS_FEATURE_COMPAT_RO_SUPP.
> 
> Signed-off-by: Nikolay Borisov <nborisov@suse.com>
> ---
>  ctree.h | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/ctree.h b/ctree.h
> index ade883fecbd6..ef05e8122982 100644
> --- a/ctree.h
> +++ b/ctree.h
> @@ -497,7 +497,9 @@ struct btrfs_super_block {
>   * added here until read-write support for the free space tree is implemented in
>   * btrfs-progs.
>   */
> -#define BTRFS_FEATURE_COMPAT_RO_SUPP		0ULL
> +#define BTRFS_FEATURE_COMPAT_RO_SUPP			\
> +	(BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE |	\
> +	 BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE_VALID)


Have you tested whether btrfs-progs commands that modify the filesystem
(e.g., btrfstune or btrfs fi label) work with this series? Because that
is a requirement for claiming that we support this bit (at which point
we can delete the comment above). Also, this needs to happen _after_ we
hook up the free space tree with the extent tree.

See here for some historical context:
https://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg57738.html