Signed-off-by: David Woodhouse <David.Woodhouse@xxxxxxxxx>
---
block/blk-core.c | 7 ++-----
include/linux/bio.h | 4 ++--
include/linux/blkdev.h | 6 +++---
3 files changed, 7 insertions(+), 10 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 0cb993a..0754a6f 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -622,10 +622,6 @@ blk_alloc_request(struct request_queue *q, int rw, int priv, gfp_t gfp_mask)
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) {
@@ -2027,7 +2023,8 @@ EXPORT_SYMBOL_GPL(blk_end_request_callback);
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 67cb2ee..83f8260 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -152,8 +152,8 @@ struct bio {
* bit 5 --
* bit 6 -- discard sectors (trim)
*/
-#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 9e3adc4..3f077a5 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -85,11 +85,11 @@ enum {
};
/*
- * 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 */
- __REQ_FAILFAST, /* no low level driver retries */
+ __REQ_RW, /* not set, read. set, write. SEE ABOVE */
+ __REQ_FAILFAST, /* no low level driver retries. SEE ABOVE */
__REQ_DISCARD, /* request to discard sectors */
__REQ_SORTED, /* elevator knows about this request */
__REQ_SOFTBARRIER, /* may not be passed by ioscheduler */
--
1.5.5.1
--
David Woodhouse Open Source Technology Centre
David.Woodhouse@xxxxxxxxx Intel Corporation
--
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