[CRIU] [PATCH 4/7] btrfs: Introduce BTRFS engine

[Pavel Emelyanov]

On 12/04/2013 05:23 PM, Cyrill Gorcunov wrote:
> 
> It is been found that BTRFS uses per subvolume device
> numbering scheme  which causes some of our tests to fail
> if they are laying on this filesystem.
> 
> Here we introduce minimal engine which parses subvolumes
> present on mount point.
> 
> The interface is two functions
> 
>  - btrfs_lazy_parse_subvol: this one parses subvolume
>    and chaches the results
> 
>  - is_btrfs_subvol: test if device id is laying on subvolume
> 
> Note is_btrfs_subvol return false if previously the subvolume
> we're inspecting here was not parsed with btrfs_lazy_parse_subvol
> call.
> 
> In the code we assume that cpu we're running on
> is little endian, thus if one day we run on big
> ending machine the code must be updated accordingly.
> 
> Signed-off-by: Cyrill Gorcunov <gorcunov at openvz.org>
> ---
>  Makefile.crtools      |   1 +
>  include/mount-btrfs.h |  79 ++++++++
>  mount-btrfs.c         | 506 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 586 insertions(+)
>  create mode 100644 include/mount-btrfs.h
>  create mode 100644 mount-btrfs.c
> 


> +	BUG_ON(m->private);
> +	m->private = (void *)result;
> +	btrfs_show_subvolumes(r);

That's the only place where mi->private is used. IOW -- it's now write-only field.