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().

Fixes: dac56212e8127 ("bio: skip atomic inc/dec of ->bi_cnt for most use cases") Cc: stable@vger.kernel.org Reported-by: "Paul E. McKenney" paulmck@linux.ibm.com Reported-by: Peter Zijlstra peterz@infradead.org Signed-off-by: Andrea Parri andrea.parri@amarulasolutions.com Cc: Jens Axboe axboe@kernel.dk Cc: linux-block@vger.kernel.org

---

include/linux/bio.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/bio.h b/include/linux/bio.h index e584673c18814..5becbafb84e8a 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -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();
  

• smp_mb();
  

  } atomic_set(&bio->__bi_cnt, count);

}

2.7.4

Looks fine,

Reviewed-by: Ming Lei ming.lei@redhat.com

Thanks, Ming