[Libguestfs] [PATCH v2 15/23] daemon: Reimplement ‘btrfs_subvolume_list’ and ‘btrfs_subvolume_get_default’ in OCaml.

[Pino Toscano]

On Friday, 21 July 2017 22:36:19 CEST Richard W.M. Jones wrote:
> +let rec with_mounted mountable f =
> +  match mountable.m_type with
> +  | MountablePath ->
> +     (* This corner-case happens for Mountable_or_Path parameters, where
> +      * a path was supplied by the caller.  The path (the m_device
> +      * field) is relative to the sysroot.
> +      *)
> +     f (Sysroot.sysroot_path mountable.m_device)
> +
> +  | MountableDevice ->
> +     let cmd tmpdir =
> +       ignore (command "mount" [mountable.m_device; tmpdir]) in
> +     _with_mounted cmd f
> +
> +  | MountableBtrfsVol subvol ->
> +     let cmd tmpdir =
> +       ignore (command "mount" ["-o"; "subvol=" ^ subvol (* XXX quoting? *);
> +                                mountable.m_device; tmpdir]) in
> +     _with_mounted cmd f
> +
> +and _with_mounted mount_cmd f =
> +  let tmpdir = Mkdtemp.temp_dir "btrfs" in
> +
> +  (* This is the cleanup function which is called to unmount and
> +   * remove the temporary directory.  This is called on error and
> +   * ordinary exit paths.
> +   *)
> +  let finally () =
> +    ignore (Sys.command (sprintf "umount %s" (quote tmpdir)));
> +    rmdir tmpdir
> +  in
> +
> +  protect ~finally ~f:(fun () -> mount_cmd tmpdir; f tmpdir)

As minor note: this subhelper (_with_mounted) could be moved inside
with_mounted, so there is no risk to use it "accidentally" elsewhere
in btrfs.ml.  (Yes, I know the parameters are different, so a '_' typo
would give a build error, but you can get what I mean here.)

Thanks,
-- 
Pino Toscano
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