[Libguestfs] [PATCH v3 8/8] lib/canonical-name.c: Hide EINVAL error from underlying API call.

[Martin Kletzander]

On Fri, Oct 09, 2020 at 02:21:09PM +0100, Richard W.M. Jones wrote:
>On Fri, Oct 09, 2020 at 11:37:41AM +0100, Richard W.M. Jones wrote:
>> On Fri, Oct 09, 2020 at 11:33:43AM +0100, Richard W.M. Jones wrote:
>> >
>> > This is the patch I tested which works (on top of the
>> > patch posted):
>> >
>> > diff --git a/lib/canonical-name.c b/lib/canonical-name.c
>> > index e0c7918b4..ae4def692 100644
>> > --- a/lib/canonical-name.c
>> > +++ b/lib/canonical-name.c
>> > @@ -53,8 +53,16 @@ guestfs_impl_canonical_device_name (guestfs_h *g, const char *device)
>> >       * BitLocker-encrypted volume, so simply return the original
>> >       * name in that case.
>> >       */
>> > -    if (ret == NULL && guestfs_last_errno (g) == EINVAL)
>> > -      ret = safe_strdup (g, device);
>> > +    if (ret == NULL) {
>> > +      if (guestfs_last_errno (g) == EINVAL)
>> > +        ret = safe_strdup (g, device);
>> > +      else
>> > +        /* Make sure the original error gets pushed through the
>> > +         * error handlers.
>> > +         */
>> > +        guestfs_int_error_errno (g, guestfs_last_errno (g),
>> > +                                 "%s", guestfs_last_error (g));
>> > +    }
>> >    }
>> >    else
>> >      ret = safe_strdup (g, device);
>> >
>> > ---
>> >
>> > Current upstream:
>> >
>> > $ guestfish scratch 1M : run : canonical-device-name "/dev/dm-999"
>> > libguestfs: error: lvm_canonical_lv_name: stat: /dev/dm-999: No such file or directory
>> > /dev/dm-999           <-----
>> >
>> > Patch posted without the above patch added:
>> >
>> > $ ./run guestfish scratch 1M : run : canonical-device-name "/dev/dm-999"
>> >
>> > (no output, but the command fails with exit code 1)
>> >
>> > Patch posted + above patch:
>> >
>> > $ ./run guestfish scratch 1M : run : canonical-device-name "/dev/dm-999"
>> > libguestfs: error: lvm_canonical_lv_name: stat: /dev/dm-999: No such file or directory
>>
>> Actually I didn't notice this, but it improves on the current upstream
>> behaviour.
>>
>> Current upstream calls the error handlers and returns a non-error
>> original string (see <----- line above) and exit code 0.  With the
>> patch we return an error.
>
>This breaks virt-inspector, at least when we run the test suite which
>has a phony Ubuntu guest with a non-existent /dev/mapper/* in its
>/etc/fstab.
>
>The manpage for guestfs_canonical_device_name[1] is sort of ambiguous
>here.  It says that "/dev/mapper/*" is
>
>  Converted to /dev/VG/LV form using guestfs_lvm_canonical_lv_name.
>
>and guestfs_lvm_canonical_lv_name will certainly return an error for a
>non-existent name.
>
>However it does also say:
>
>  Other strings are returned unmodified.
>
>You can sort of read it both ways.  Because it breaks a long-standing
>user of this API I'm going to change this so it behaves more like the
>current upstream code (original error goes to debug, return original
>device string).
>

OK, that makes sense.

>Rich.
>
>[1] https://libguestfs.org/guestfs.3.html#guestfs_canonical_device_name
>
>-- 
>Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
>Read my programming and virtualization blog: http://rwmj.wordpress.com
>virt-builder quickly builds VMs from scratch
>http://libguestfs.org/virt-builder.1.html
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