block: add REQ_FLUSH_SEQ

rq == &q->flush_rq was used to determine whether a rq is part of a
flush sequence, which worked because all requests in a flush sequence
were sequenced using the single dedicated request.  This is about to
change, so introduce REQ_FLUSH_SEQ flag to distinguish flush sequence
requests.

This patch doesn't cause any behavior change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 46ad5197537..dddedfc0af8 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -148,6 +148,7 @@ enum rq_flag_bits {
         __REQ_ALLOCED,          /* request came from our alloc pool */
         __REQ_COPY_USER,        /* contains copies of user pages */
         __REQ_FLUSH,            /* request for cache flush */
+        __REQ_FLUSH_SEQ,        /* request for flush sequence */
         __REQ_IO_STAT,          /* account I/O stat */
         __REQ_MIXED_MERGE,      /* merge of different types, fail separately */
         __REQ_SECURE,           /* secure discard (used with __REQ_DISCARD) */
@@ -188,6 +189,7 @@ enum rq_flag_bits {
 #define REQ_ALLOCED             (1 << __REQ_ALLOCED)
 #define REQ_COPY_USER           (1 << __REQ_COPY_USER)
 #define REQ_FLUSH               (1 << __REQ_FLUSH)
+#define REQ_FLUSH_SEQ           (1 << __REQ_FLUSH_SEQ)
 #define REQ_IO_STAT             (1 << __REQ_IO_STAT)
 #define REQ_MIXED_MERGE         (1 << __REQ_MIXED_MERGE)
 #define REQ_SECURE              (1 << __REQ_SECURE)