[RFC]block: disable discard request merge temporarily

[Shaohua Li]

The SCSI discard request merge never worked, and looks no solution for in
future, let's disable it temporarily.

Signed-off-by: Shaohua Li <shli@xxxxxxxxxxxx>

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 4e72a9d..0e6efb1 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -601,7 +601,7 @@ static inline void blk_clear_rl_full(struct request_list *rl, bool sync)
  * it already be started by driver.
  */
 #define RQ_NOMERGE_FLAGS	\
-	(REQ_NOMERGE | REQ_STARTED | REQ_SOFTBARRIER | REQ_FLUSH | REQ_FUA)
+	(REQ_NOMERGE | REQ_STARTED | REQ_SOFTBARRIER | REQ_FLUSH | REQ_FUA | REQ_DISCARD)
 #define rq_mergeable(rq)	\
 	(!((rq)->cmd_flags & RQ_NOMERGE_FLAGS) && \
 	 (((rq)->cmd_flags & REQ_DISCARD) || \
--
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