Fix up comments about matching flags between bio and rq
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/blk-core.c b/block/blk-core.c
index b5776c1..a496727 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -624,10 +624,6 @@
blk_rq_init(q, rq);
- /*
- * first three bits are identical in rq->cmd_flags and bio->bi_rw,
- * see bio.h and blkdev.h
- */
rq->cmd_flags = rw | REQ_ALLOCED;
if (priv) {
@@ -2012,7 +2008,8 @@
void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
struct bio *bio)
{
- /* first two bits are identical in rq->cmd_flags and bio->bi_rw */
+ /* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw, and
+ we want BIO_RW_AHEAD (bit 1) to imply REQ_FAILFAST (bit 1). */
rq->cmd_flags |= (bio->bi_rw & 3);
rq->nr_phys_segments = bio_phys_segments(q, bio);
diff --git a/include/linux/bio.h b/include/linux/bio.h
index dbeb66f..17f1fbd 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -150,8 +150,8 @@
* bit 3 -- fail fast, don't want low level driver retries
* bit 4 -- synchronous I/O hint: the block layer will unplug immediately
*/
-#define BIO_RW 0
-#define BIO_RW_AHEAD 1
+#define BIO_RW 0 /* Must match RW in req flags (blkdev.h) */
+#define BIO_RW_AHEAD 1 /* Must match FAILFAST in req flags */
#define BIO_RW_BARRIER 2
#define BIO_RW_FAILFAST 3
#define BIO_RW_SYNC 4
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 53ea933..e0ba018 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -84,7 +84,7 @@
};
/*
- * request type modified bits. first three bits match BIO_RW* bits, important
+ * request type modified bits. first two bits match BIO_RW* bits, important
*/
enum rq_flag_bits {
__REQ_RW, /* not set, read. set, write */