[Libguestfs] [PATCH v3] New API: guestfs_device_name returning the drive name

[Richard W.M. Jones]

On Mon, May 02, 2022 at 09:20:16AM +0200, Laszlo Ersek wrote:
> On 04/29/22 13:04, Richard W.M. Jones wrote:
> > For each drive added, return the name.  For example calling this with
> > index 0 will return the string "/dev/sda".  I called it
> > guestfs_device_name (not drive_name) for consistency with the existing
> > guestfs_device_index function.
> > 
> > You don't really need to call this function.  You can follow the
> > advice here:
> > https://libguestfs.org/guestfs.3.html#block-device-naming
> > and assume that drives are added with predictable names like
> > "/dev/sda", "/dev/sdb", etc.
> > 
> > However it's useful to expose the internal guestfs_int_drive_name
> > function since especially handling names beyond index 26 is tricky
> > (https://rwmj.wordpress.com/2011/01/09/how-are-linux-drives-named-beyond-drive-26-devsdz/)
> > 
> > Fixes: https://github.com/libguestfs/libguestfs/issues/80
> > ---
> >  generator/actions_core.ml | 24 +++++++++++++++++++++++-
> >  lib/drives.c              | 15 +++++++++++++++
> >  2 files changed, 38 insertions(+), 1 deletion(-)
> > 
> > diff --git a/generator/actions_core.ml b/generator/actions_core.ml
> > index ce9ee39cca..dc12fdc33e 100644
> > --- a/generator/actions_core.ml
> > +++ b/generator/actions_core.ml
> > @@ -737,7 +737,29 @@ returns the index of the device in the list of devices.
> >  Index numbers start from 0.  The named device must exist,
> >  for example as a string returned from C<guestfs_list_devices>.
> >  
> > -See also C<guestfs_list_devices>, C<guestfs_part_to_dev>." };
> > +See also C<guestfs_list_devices>, C<guestfs_part_to_dev>,
> > +C<guestfs_device_name>." };
> > +
> > +  { defaults with
> > +    name = "device_name"; added = (1, 49, 1);
> > +    style = RString (RPlainString, "name"), [Int "index"], [];
> > +    tests = [
> > +      InitEmpty, Always, TestResult (
> > +        [["device_name"; "0"]], "STREQ (ret, \"/dev/sda\")"), [];
> > +      InitEmpty, Always, TestResult (
> > +        [["device_name"; "1"]], "STREQ (ret, \"/dev/sdb\")"), [];
> > +      InitEmpty, Always, TestLastFail (
> > +        [["device_name"; "99"]]), []
> > +    ];
> > +    shortdesc = "convert device index to name";
> > +    longdesc = "\
> > +This function takes a device index and returns the device
> > +name.  For example index C<0> will return the string C</dev/sda>.
> > +
> > +The drive index must have been added to the handle.
> > +
> > +See also C<guestfs_list_devices>, C<guestfs_part_to_dev>,
> > +C<guestfs_device_index>." };
> >  
> >    { defaults with
> >      name = "shutdown"; added = (1, 19, 16);
> > diff --git a/lib/drives.c b/lib/drives.c
> > index fd95308d2d..a6179fc367 100644
> > --- a/lib/drives.c
> > +++ b/lib/drives.c
> > @@ -31,6 +31,7 @@
> >  #include <netdb.h>
> >  #include <arpa/inet.h>
> >  #include <assert.h>
> > +#include <errno.h>
> >  #include <libintl.h>
> >  
> >  #include "c-ctype.h"
> > @@ -1084,3 +1085,17 @@ guestfs_impl_device_index (guestfs_h *g, const char *device)
> >      error (g, _("%s: device not found"), device);
> >    return r;
> >  }
> > +
> > +char *
> > +guestfs_impl_device_name (guestfs_h *g, int index)
> > +{
> > +  char drive_name[64];
> > +
> > +  if (index < 0 || index >= g->nr_drives) {
> > +    guestfs_int_error_errno (g, EINVAL, _("drive index out of range"));
> > +    return NULL;
> > +  }
> > +
> > +  guestfs_int_drive_name (index, drive_name);
> > +  return safe_asprintf (g, "/dev/sd%s", drive_name);
> > +}
> > 
> 
> Reviewed-by: Laszlo Ersek <lersek at redhat.com>

Thanks, pushed as commit ac00e603f8.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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