Re: [PATCH 2/5] bio: fix improper use of smp_mb__before_atomic()

Peter Zijlstra
2019-04-30T08:22:04Z

On Mon, Apr 29, 2019 at 10:14:58PM +0200, Andrea Parri wrote:
> This barrier only applies to the read-modify-write operations; in
> particular, it does not apply to the atomic_set() primitive.
>
> Replace the barrier with an smp_mb().

> @@ -224,7 +224,7 @@ static inline void bio_cnt_set(struct bio *bio, unsigned int count)
> {
> if (count != 1) {
> bio->bi_flags |= (1 << BIO_REFFED);
> - smp_mb__before_atomic();

Maybe also add:

/*
* XXX the comment that explain this barrier goes here
*/
> + smp_mb();
> }
> atomic_set(&bio->__bi_cnt, count);
> }