block: make every barrier action optional

In all barrier sequences, the barrier write itself was always assumed
to be issued and thus didn't have corresponding control flag.  This
patch adds QUEUE_ORDERED_DO_BAR and unify action mask handling in
start_ordered() such that any barrier action can be skipped.

This patch doesn't introduce any visible behavior changes.

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

1 files changed, 5 insertions, 2 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 5c92b4432399..b044267009ed 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -526,12 +526,14 @@ enum {
         QUEUE_ORDERED_BY_DRAIN          = 0x01,
         QUEUE_ORDERED_BY_TAG            = 0x02,
         QUEUE_ORDERED_DO_PREFLUSH       = 0x10,
+        QUEUE_ORDERED_DO_BAR            = 0x20,
         QUEUE_ORDERED_DO_POSTFLUSH      = 0x40,
         QUEUE_ORDERED_DO_FUA            = 0x80,
 
         QUEUE_ORDERED_NONE              = 0x00,
 
-        QUEUE_ORDERED_DRAIN             = QUEUE_ORDERED_BY_DRAIN,
+        QUEUE_ORDERED_DRAIN             = QUEUE_ORDERED_BY_DRAIN |
+                                          QUEUE_ORDERED_DO_BAR,
         QUEUE_ORDERED_DRAIN_FLUSH       = QUEUE_ORDERED_DRAIN |
                                           QUEUE_ORDERED_DO_PREFLUSH |
                                           QUEUE_ORDERED_DO_POSTFLUSH,
@@ -539,7 +541,8 @@ enum {
                                           QUEUE_ORDERED_DO_PREFLUSH |
                                           QUEUE_ORDERED_DO_FUA,
 
-        QUEUE_ORDERED_TAG               = QUEUE_ORDERED_BY_TAG,
+        QUEUE_ORDERED_TAG               = QUEUE_ORDERED_BY_TAG |
+                                          QUEUE_ORDERED_DO_BAR,
         QUEUE_ORDERED_TAG_FLUSH         = QUEUE_ORDERED_TAG |
                                           QUEUE_ORDERED_DO_PREFLUSH |
                                           QUEUE_ORDERED_DO_POSTFLUSH,