[5.1,006/405] bio: fix improper use of smp_mb__before_atomic()

Commit Message

Greg Kroah-Hartman May 30, 2019, 3 a.m. UTC

From: Andrea Parri <[e-mail]>

commit f381c6a4bd0ae0fde2d6340f1b9bb0f58d915de6 upstream.

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: [e-mail]
Reported-by: "Paul E. McKenney" <[e-mail]>
Reported-by: Peter Zijlstra <[e-mail]>
Signed-off-by: Andrea Parri <[e-mail]>
Reviewed-by: Ming Lei <[e-mail]>
Cc: Jens Axboe <[e-mail]>
Cc: Ming Lei <[e-mail]>
Cc: [e-mail]
Cc: "Paul E. McKenney" <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Signed-off-by: Jens Axboe <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

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

Patch

--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -224,7 +224,7 @@  static inline void bio_cnt_set(struct bi
 {
 	if (count != 1) {
 		bio->bi_flags |= (1 << BIO_REFFED);
-		smp_mb__before_atomic();
+		smp_mb();
 	}
 	atomic_set(&bio->__bi_cnt, count);
 }