Re: [xfsprogs] Do we need so many data types for user input?

Luis R. Rodriguez
2017-04-06T12:40:12Z

On Wed, Apr 05, 2017 at 04:24:18PM +0200, Jan Tulak wrote:
> On Wed, Apr 5, 2017 at 4:08 PM, Eric Sandeen <sandeen@sandeen.net> wrote:
> >
> > On 4/5/17 3:26 AM, Jan Tulak wrote:
> >> On Tue, Apr 4, 2017 at 10:17 PM, Eric Sandeen <sandeen@sandeen.net> wrote:
> >>> On 4/4/17 2:48 PM, Luis R. Rodriguez wrote:
> >>>>
> >>>> And then agsize is capped artificially later via validate_ag_geometry():
> >>>>
> >>>> if (agsize < XFS_AG_MIN_BLOCKS(blocklog)) {
> >>>> ...
> >>>> if (agsize > XFS_AG_MAX_BLOCKS(blocklog)) {
> >>>> ...
> >>>> if (agsize > dblocks) {
> >>>> ...
> >>>> if (agsize > XFS_AG_MAX_BLOCKS(blocklog)) {
> >>>> ...
> >>>>
> >>>> Its not clear if this is capped at UINT_MAX or if we need ULLONG_MAX here.
> >>>
> >>> .maxval = XFS_AG_MAX_BYTES,
> >>>
> >>> #define XFS_AG_MAX_BYTES ((XFS_AG_BYTES(31))) /* 1 TB */
> >>> #define XFS_AG_BYTES(bblog) ((long long)BBSIZE << (bblog))
> >>>
> >>> so the maximum is (long long)(512) << 31
> >>>
> >>> so, no - agsize won't fit in a 32 bit var, if that's the question...
> >>>
> >>
> >> Yeah. I think that we can make it uint64 everywhere unless it is
> >> causing an issue in a specific case with a bit shift or something, and
> >> just limit the input value where appropriate explicitly.
> >>
> >>
> >> And...
> >>> And at the end of the day, we are converting all numbers into unsigned
> >>
> >> I take back this part, we are going through long long, not unsigned long long.
> >> Everything else is still valid.
> >
> > Ok, for those who aren't immersed 24/7 in mkfs ;) can you help us understand
> > where you're going with this? What's the change you're proposing, and how
> > does it help?
> >
>
> If you ask only about the last sentence - I was just taking back my
> claim that we already convert all numbers into unsigned in getnum. We
> convert them to long long right now.

Yes but this is just general best practice -- typically strtoll() is used
and then folks cast as needed, this is done to avoid loosing information.
The casting is also where a lot of potential bugs can lurk.

getnum() returns long long, we currently cast this mostly to int.

> (It was too late evening for me,
> apparently. :-) )
>
> If you ask more about summarising what I want to do, then:
>
> I'm already moving these standalone variables into an options table,
> that holds all the information in one place. As I'm already touching
> them, I can as well clean the differences and changes accumulated over
> the years and change a lot of mkfs's internal variables from a mix of
> signed and unsigned, 32bit and 64bit, to a single type, unsigned
> 64bits long.
>
> That would simplify the code in some places and make it clear what
> type numerical values are - less things like foo((long long) bar);

Yes please ! Modulo -- as I noted I think in practice this may be:

a) self contained work -- if the changes from say int to another unsigned
type on xfs_mkfs.c only affect this file.

b) a lot changes: if the type changes require much more changes to API calls
outside of this xfs_mkfs.c file, say when the file calls to helpers.

I think a) seems reasonable to do now. b) I think this should be welcomed but
it means much more patches to your series, so if it turns out to be a lot
perhaps best left as a secondary effort for later. I don't think it clear
where this falls yet.

Luis