Re: CEPH_RBD_API: options on image create

[Mykola Golub <mgolub@mirantis.com>]

On Thu, Oct 15, 2015 at 08:05:07AM -0400, Jason Dillaman wrote:
> > > I am concerned about passing a void* + length to specify the option
> > > value since you really can't protect against the user providing data
> > > in the incorrect format.  For example, if the backend treated
> > > RBD_OPTION_STRIPE_UNIT as a 4byte int, what happens if someone
> > > passes a 2- or 8-byte int or a 4-byte char* string?
> > 
> > Then rbd_image_options_set() will fail with EINVAL, because the option
> > type (size) is a part of interface.
> > 
> > I do this by analogy to setsockopt(2):
> > 
> > http://pubs.opengroup.org/onlinepubs/009695399/functions/setsockopt.html
> > 
> > Note option type documented for every option there, and it works
> > fairly well.
> > 
> > Following a common practice is an additional argument to this
> > approach to me.
> 
> Except for the following cases:
> 
> sizeof(char*) == sizeof(uint32_t) (32bit)
> sizeof(char*) == sizeof(uint64_t) (64bit)

But we don't need them to match between different platforms, no? Is
linking 64bit code with 32bit possible (supported)?

Also, for this particular (char*) case, length would actually be the
length of the string, not the pointer length. From my example:

const char* journal_object_pool = "journal";
r = rbd_image_options_set(opts, RBD_OPTION_JOURNAL_OBJECT_POOL,
                          journal_object_pool, strlen(journal_object_pool) + 1);

-- 
Mykola Golub