block: use the same failfast bits for bio and request

bio and request use the same set of failfast bits.  This patch makes
the following changes to simplify things.

* enumify BIO_RW* bits and reorder bits such that BIOS_RW_FAILFAST_*
  bits coincide with __REQ_FAILFAST_* bits.

* The above pushes BIO_RW_AHEAD out of sync with __REQ_FAILFAST_DEV
  but the matching is useless anyway.  init_request_from_bio() is
  responsible for setting FAILFAST bits on FS requests and non-FS
  requests never use BIO_RW_AHEAD.  Drop the code and comment from
  blk_rq_bio_prep().

* Define REQ_FAILFAST_MASK which is OR of all FAILFAST bits and
  simplify FAILFAST flags handling in init_request_from_bio().

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 7 insertions, 12 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index e3299a77a0d8..4daae1ee2b23 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1111,17 +1111,13 @@ void init_request_from_bio(struct request *req, struct bio *bio)
         req->cmd_type = REQ_TYPE_FS;
 
         /*
-         * inherit FAILFAST from bio (for read-ahead, and explicit FAILFAST)
+         * Inherit FAILFAST from bio (for read-ahead, and explicit
+         * FAILFAST).  FAILFAST flags are identical for req and bio.
          */
         if (bio_rw_ahead(bio))
-                req->cmd_flags |= (REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
-                                   REQ_FAILFAST_DRIVER);
-        if (bio_failfast_dev(bio))
-                req->cmd_flags |= REQ_FAILFAST_DEV;
-        if (bio_failfast_transport(bio))
-                req->cmd_flags |= REQ_FAILFAST_TRANSPORT;
-        if (bio_failfast_driver(bio))
-                req->cmd_flags |= REQ_FAILFAST_DRIVER;
+                req->cmd_flags |= REQ_FAILFAST_MASK;
+        else
+                req->cmd_flags |= bio->bi_rw & REQ_FAILFAST_MASK;
 
         if (unlikely(bio_discard(bio))) {
                 req->cmd_flags |= REQ_DISCARD;
@@ -2239,9 +2235,8 @@ EXPORT_SYMBOL(__blk_end_request_cur);
 void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
                      struct bio *bio)
 {
-        /* 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);
+        /* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw */
+        rq->cmd_flags |= bio->bi_rw & REQ_RW;
 
         if (bio_has_data(bio)) {
                 rq->nr_phys_segments = bio_phys_segments(q, bio);