Re: [PATCH 01/13] seqnum_ops: Introduce Sequence Number Ops

[Shuah Khan]

On 11/11/20 12:23 PM, Shuah Khan wrote:
> On 11/10/20 5:18 PM, Kees Cook wrote:
> > On Tue, Nov 10, 2020 at 09:43:02PM +0100, Greg KH wrote:
> > > On Tue, Nov 10, 2020 at 09:41:40PM +0100, Greg KH wrote:
> > > > On Tue, Nov 10, 2020 at 12:53:27PM -0700, Shuah Khan wrote:
> > > > > +Decrement interface
> > > > > +-------------------
> > > > > +
> > > > > +Decrements sequence number and doesn't return the new value. ::
> > > > > +
> > > > > +        seqnum32_dec() --> atomic_dec()
> > > > > +        seqnum64_dec() --> atomic64_dec()
> > > >
> > > > Why would you need to decrement a sequence number?  Shouldn't they just
> > > > always go up?
> > > >
> > > > I see you use them in your patch 12/13, but I don't think that 
> > > > really is
> > > > a sequence number there, but rather just some other odd value :)
> >
> > To that end, they should likely be internally cast to u32 and u64 (and
> > why is seqnum64 ifdef on CONFIG_64BIT?).

atomic64_t depends on CONFIG_64BIT

include/linux/types.h

#ifdef CONFIG_64BIT
typedef struct {
        s64 counter;
} atomic64_t;
#endif

thanks,
-- Shuah