Re: [RFC PATCH 1/2] block: change rq_integrity_vec to respect the iterator

[Mikulas Patocka <mpatocka@redhat.com>]

On Wed, 15 May 2024, Jens Axboe wrote:

> On 5/15/24 7:28 AM, Mikulas Patocka wrote:
> > @@ -177,9 +177,9 @@ static inline int blk_integrity_rq(struc
> >  	return 0;
> >  }
> >  
> > -static inline struct bio_vec *rq_integrity_vec(struct request *rq)
> > +static inline struct bio_vec rq_integrity_vec(struct request *rq)
> >  {
> > -	return NULL;
> > +	BUG();
> >  }
> >  #endif /* CONFIG_BLK_DEV_INTEGRITY */
> >  #endif /* _LINUX_BLK_INTEGRITY_H */
> 
> Let's please not do that. If it's not used outside of
> CONFIG_BLK_DEV_INTEGRITY, it should just go away.
> 
> -- 
> Jens Axboe

It can't go away - it is guarded with blk_integrity_rq (which always 
returns 0 if compiled without CONFIG_BLK_DEV_INTEGRITY), so the compiler 
will optimize-out the calls to rq_integrity_vec. But we can't delete 
rq_integrity_vec, because the source code references it.

Should rq_integrity_vec return empty 'struct bio_vec' instead? Or should 
we add more CONFIG_BLK_DEV_INTEGRITY tests to disable the call locations?

Mikulas