[Libguestfs] [PATCH] daemon/RHEL: Choose correct udev settle script.

[Jim Meyering]

Richard W.M. Jones wrote:
> Subject: [PATCH] daemon/RHEL: Choose correct udev settle script.
>
> On RHEL/CentOS 5.4, udevadm settle command does not work.  This didn't
> affect us before, but now that we're using parted for partitioning, we
> *do* need to wait for udev to settle (because parted isn't waiting for
> this, unlike sfdisk).
>
> This commit chooses the correct program to run.
> ---
>  daemon/guestfsd.c |   22 +++++++++++++++++++++-
>  1 files changed, 21 insertions(+), 1 deletions(-)
>
> diff --git a/daemon/guestfsd.c b/daemon/guestfsd.c
> index db0bff9..9375ede 100644
> --- a/daemon/guestfsd.c
> +++ b/daemon/guestfsd.c
> @@ -976,5 +976,25 @@ device_name_translation (char *device, const char *func)
>  void
>  udev_settle (void)
>  {
> -  command (NULL, NULL, "/sbin/udevadm", "settle", NULL);
> +  static int which_prog = 0;
> +
> +  if (which_prog == 0) {
> +    if (access ("/sbin/udevsettle", X_OK) == 0)
> +      which_prog = 2;
> +    else if (access ("/sbin/udevadm", X_OK) == 0)
> +      which_prog = 1;
> +    else
> +      which_prog = 3;
> +  }
> +  switch (which_prog) {
> +  case 1:
> +    command (NULL, NULL, "/sbin/udevadm", "settle", NULL);
> +    break;
> +  case 2:
> +    command (NULL, NULL, "/sbin/udevsettle", NULL);
> +    break;
> +  default:
> +    ;
> +  }

Looks fine.
Only thought was "why bother with the static var and separate switch"
just to save a call or two to access.  If you're about to invoke
one of those programs, the expense of a syscall is nil.