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, 4 insertions, 0 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 69103e053c92..c3015736d814 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -93,6 +93,7 @@ enum rq_flag_bits {
         __REQ_FAILFAST_DEV,     /* no driver retries of device errors */
         __REQ_FAILFAST_TRANSPORT, /* no driver retries of transport errors */
         __REQ_FAILFAST_DRIVER,  /* no driver retries of driver errors */
+        /* above flags must match BIO_RW_* */
         __REQ_DISCARD,          /* request to discard sectors */
         __REQ_SORTED,           /* elevator knows about this request */
         __REQ_SOFTBARRIER,      /* may not be passed by ioscheduler */
@@ -143,6 +144,9 @@ enum rq_flag_bits {
 #define REQ_NOIDLE      (1 << __REQ_NOIDLE)
 #define REQ_IO_STAT     (1 << __REQ_IO_STAT)
 
+#define REQ_FAILFAST_MASK       (REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT | \
+                                 REQ_FAILFAST_DRIVER)
+
 #define BLK_MAX_CDB     16
 
 /*