[Libguestfs] [PATCH] fuse: In mount-local-run, test if root filesystem has been mounted (RHBZ#1057504).

[Pino Toscano]

On Friday 24 January 2014 10:22:58 Richard W.M. Jones wrote:
> It is never normally valid to use the mount-local* APIs when you
> haven't mounted some filesystems in the libguestfs namespace.
> 
> If you try it, it results in some odd errors.  The mount-local-run
> call is successful, but subsequent operations fail:
> 
> $ mkdir -p /tmp/mnt
> $ guestfish -x -N fs mount-local /tmp/mnt : mount-local-run
> libguestfs: error: lstat: lstat_stub: you must call 'mount' first to
> mount the root filesystem libguestfs: error: lstat: lstat_stub: you
> must call 'mount' first to mount the root filesystem
> 
> With this commit, the mount-local-run call gives an error.
> 
> The error is implemented by calling guestfs_exists (g, "/") which has
> the side effect of running the NEED_ROOT macro in the daemon.  (There
> is no simple equivalent of NEED_ROOT on the library side.)
> ---
>  src/fuse.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/src/fuse.c b/src/fuse.c
> index dd4f139..c22cbba 100644
> --- a/src/fuse.c
> +++ b/src/fuse.c
> @@ -1028,6 +1028,12 @@ guestfs__mount_local_run (guestfs_h *g)
>      return -1;
>    }
> 
> +  /* Test if root is mounted.  We do this by using a side-effect of
> +   * guestfs_exists (which is that it calls NEED_ROOT).
> +   */
> +  if (guestfs_exists (g, "/") == -1)
> +    return -1;
> +
>    debug (g, "%s: entering fuse_loop", __func__);
> 
>    /* Enter the main loop. */

Sounds good (you are fast :) )
The only drawback is that the guestfish command above will leave the 
local FUSE mountpoint still mounted after the guestfish run.
Not sure whether it is worth doing anything automatic about that though, 
maybe just adding a
  error (g, _("remember to umount the mountpoint by invoking
               `guestumount` or using unmount-local"));
before the «return -1» in the patch above could help.

-- 
Pino Toscano