[PATCH] Only the first two bits in bio->bi_rw and rq->flags match

Not three, as assumed. This causes the barrier bit to be needlessly set
for some IO.

Signed-off-by: Jens Axboe <axboe@suse.de>

diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index ab17c72..61d6b3c 100644 (file)
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -3491,8 +3491,8 @@ EXPORT_SYMBOL(end_request);
 
 void blk_rq_bio_prep(request_queue_t *q, struct request *rq, struct bio *bio)
 {
-       /* first three bits are identical in rq->flags and bio->bi_rw */
-       rq->flags |= (bio->bi_rw & 7);
+       /* first two bits are identical in rq->flags and bio->bi_rw */
+       rq->flags |= (bio->bi_rw & 3);
 
        rq->nr_phys_segments = bio_phys_segments(q, bio);
        rq->nr_hw_segments = bio_hw_segments(q, bio);

diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h
index 2346a1d..7520cc1 100644 (file)
--- a/include/linux/blktrace_api.h
+++ b/include/linux/blktrace_api.h
@@ -148,7 +148,7 @@ static inline void blk_add_trace_rq(struct request_queue *q, struct request *rq,
                                    u32 what)
 {
        struct blk_trace *bt = q->blk_trace;
-       int rw = rq->flags & 0x07;
+       int rw = rq->flags & 0x03;
 
        if (likely(!bt))
                return;