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[4.9,003/128] bio: fix improper use of smp_mb__before_atomic()

Message ID 20190530030433.605961301@linuxfoundation.org (mailing list archive)
State New, archived
Headers show
Series None | expand

Commit Message

Greg KH May 30, 2019, 3:05 a.m. UTC
From: Andrea Parri <andrea.parri@amarulasolutions.com>

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: 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>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: linux-block@vger.kernel.org
Cc: "Paul E. McKenney" <paulmck@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

 include/linux/bio.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -237,7 +237,7 @@  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);