[SCSI] block: separate failfast into multiple bits.

Multipath is best at handling transport errors. If it gets a device
error then there is not much the multipath layer can do. It will just
access the same device but from a different path.

This patch breaks up failfast into device, transport and driver errors.
The multipath layers (md and dm mutlipath) only ask the lower levels to
fast fail transport errors. The user of failfast, read ahead, will ask
to fast fail on all errors.

Note that blk_noretry_request will return true if any failfast bit
is set. This allows drivers that do not support the multipath failfast
bits to continue to fail on any failfast error like before. Drivers
like scsi that are able to fail fast specific errors can check
for the specific fail fast type. In the next patch I will convert
scsi.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

1 files changed, 12 insertions, 3 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index a92d9e4ea96e..f3491d225268 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -87,7 +87,9 @@ enum {
  */
 enum rq_flag_bits {
         __REQ_RW,               /* not set, read. set, write */
-        __REQ_FAILFAST,         /* no low level driver retries */
+        __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 */
         __REQ_DISCARD,          /* request to discard sectors */
         __REQ_SORTED,           /* elevator knows about this request */
         __REQ_SOFTBARRIER,      /* may not be passed by ioscheduler */
@@ -111,8 +113,10 @@ enum rq_flag_bits {
 };
 
 #define REQ_RW          (1 << __REQ_RW)
+#define REQ_FAILFAST_DEV        (1 << __REQ_FAILFAST_DEV)
+#define REQ_FAILFAST_TRANSPORT  (1 << __REQ_FAILFAST_TRANSPORT)
+#define REQ_FAILFAST_DRIVER     (1 << __REQ_FAILFAST_DRIVER)
 #define REQ_DISCARD     (1 << __REQ_DISCARD)
-#define REQ_FAILFAST    (1 << __REQ_FAILFAST)
 #define REQ_SORTED      (1 << __REQ_SORTED)
 #define REQ_SOFTBARRIER (1 << __REQ_SOFTBARRIER)
 #define REQ_HARDBARRIER (1 << __REQ_HARDBARRIER)
@@ -560,7 +564,12 @@ enum {
 #define blk_special_request(rq) ((rq)->cmd_type == REQ_TYPE_SPECIAL)
 #define blk_sense_request(rq)   ((rq)->cmd_type == REQ_TYPE_SENSE)
 
-#define blk_noretry_request(rq) ((rq)->cmd_flags & REQ_FAILFAST)
+#define blk_failfast_dev(rq)    ((rq)->cmd_flags & REQ_FAILFAST_DEV)
+#define blk_failfast_transport(rq) ((rq)->cmd_flags & REQ_FAILFAST_TRANSPORT)
+#define blk_failfast_driver(rq) ((rq)->cmd_flags & REQ_FAILFAST_DRIVER)
+#define blk_noretry_request(rq) (blk_failfast_dev(rq) ||        \
+                                 blk_failfast_transport(rq) ||  \
+                                 blk_failfast_driver(rq))
 #define blk_rq_started(rq)      ((rq)->cmd_flags & REQ_STARTED)
 
 #define blk_account_rq(rq)      (blk_rq_started(rq) && (blk_fs_request(rq) || blk_discard_rq(rq)))