bcache: use op_is_write instead of checking for REQ_WRITE

We currently set REQ_WRITE/WRITE for all non READ IOs
like discard, flush, writesame, etc. In the next patches where we
no longer set up the op as a bitmap, we will not be able to
detect a operation direction like writesame by testing if REQ_WRITE is
set.

This has bcache use the op_is_write helper which will do the right
thing.
Signed-off-by: Mike Christie <mchristi@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/md/bcache/io.c

@@ -111,7 +111,7 @@ void bch_bbio_count_io_errors(struct cache_set *c, struct bio *bio,
 	struct bbio *b = container_of(bio, struct bbio, bio);
 	struct cache *ca = PTR_CACHE(c, &b->key, 0);
 
-	unsigned threshold = bio->bi_rw & REQ_WRITE
+	unsigned threshold = op_is_write(bio_op(bio))
 		? c->congested_write_threshold_us
 		: c->congested_read_threshold_us;
 

drivers/md/bcache/request.c

@@ -383,7 +383,7 @@ static bool check_should_bypass(struct cached_dev *dc, struct bio *bio)
 
 	if (mode == CACHE_MODE_NONE ||
 	    (mode == CACHE_MODE_WRITEAROUND &&
-	     (bio->bi_rw & REQ_WRITE)))
+	     op_is_write(bio_op(bio))))
 		goto skip;
 
 	if (bio->bi_iter.bi_sector & (c->sb.block_size - 1) ||
@@ -404,7 +404,7 @@ static bool check_should_bypass(struct cached_dev *dc, struct bio *bio)
 
 	if (!congested &&
 	    mode == CACHE_MODE_WRITEBACK &&
-	    (bio->bi_rw & REQ_WRITE) &&
+	    op_is_write(bio_op(bio)) &&
 	    (bio->bi_rw & REQ_SYNC))
 		goto rescale;
 
@@ -657,7 +657,7 @@ static inline struct search *search_alloc(struct bio *bio,
 	s->cache_miss		= NULL;
 	s->d			= d;
 	s->recoverable		= 1;
-	s->write		= (bio->bi_rw & REQ_WRITE) != 0;
+	s->write		= op_is_write(bio_op(bio));
 	s->read_dirty_data	= 0;
 	s->start_time		= jiffies;