[Libguestfs] [PATCH libguestfs] daemon: Make vg_scan and lvm_scan no-ops if no LVM feature

[Laszlo Ersek]

On 09/27/22 14:10, Richard W.M. Jones wrote:
> If the LVM ("lvm2") feature is not available, these calls would fail.
> Really they ought to be part of the "lvm2" optgroup which would cause
> the generator to call reply_with_unavailable_feature and generate the
> correct ENOTSUP error.  When vgscan was originally added in 2010 it
> was not added to the optgroup, and when lvm_scan was later added in
> 2018 and deprecating vgscan, the same mistake was copied.
> 
> Before this commit they will try to run the lvm pvscan command which
> will fail returning some other error (instead of ENOTSUP).
> 
> Fix this by turning the calls into no-ops if the LVM feature is not
> available, since scanning for LVM objects when there is no LVM can be
> safely turned into a no-op.
> 
> See also
> https://listman.redhat.com/archives/libguestfs/2022-September/thread.html#29908
> 
> Reported-by: Laszlo Ersek
> Fixes: 55dfcb2211 ("New API: lvm_scan, deprecate vgscan")
> Fixes: 9752039e52 ("New API: vgscan")
> ---
>  daemon/lvm.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/daemon/lvm.c b/daemon/lvm.c
> index 72c59c3a1b..c273946d34 100644
> --- a/daemon/lvm.c
> +++ b/daemon/lvm.c
> @@ -651,6 +651,13 @@ do_lvm_scan (int activate)
>    const char *argv[MAX_ARGS];
>    size_t i = 0;
>  
> +  /* Historically this call was never added to the "lvm2" optgroup.
> +   * Rather than changing that and have the small risk of breaking
> +   * callers, just make it into a no-op if LVM is not available.
> +   */
> +  if (optgroup_lvm2_available () == 0)
> +    return 0;
> +
>    ADD_ARG (argv, i, "lvm");
>    ADD_ARG (argv, i, "pvscan");
>    ADD_ARG (argv, i, "--cache");
> 

Acked-by: Laszlo Ersek <lersek at redhat.com>

Thanks!
Laszlo