block: Add flag for telling the IO schedulers NOT to anticipate more IO

By default, CFQ will anticipate more IO from a given io context if the
previously completed IO was sync. This used to be fine, since the only
sync IO was reads and O_DIRECT writes. But with more "normal" sync writes
being used now, we don't want to anticipate for those.

Add a bio/request flag that informs the IO scheduler that this is a sync
request that we should not idle for. Introduce WRITE_ODIRECT specifically
for O_DIRECT writes, and make sure that the other sync writes set this
flag.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 67dae3bd881c..e03660964e02 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -118,6 +118,7 @@ enum rq_flag_bits {
         __REQ_COPY_USER,        /* contains copies of user pages */
         __REQ_INTEGRITY,        /* integrity metadata has been remapped */
         __REQ_UNPLUG,           /* unplug queue on submission */
+        __REQ_NOIDLE,           /* Don't anticipate more IO after this one */
         __REQ_NR_BITS,          /* stops here */
 };
 
@@ -145,6 +146,7 @@ enum rq_flag_bits {
 #define REQ_COPY_USER   (1 << __REQ_COPY_USER)
 #define REQ_INTEGRITY   (1 << __REQ_INTEGRITY)
 #define REQ_UNPLUG      (1 << __REQ_UNPLUG)
+#define REQ_NOIDLE      (1 << __REQ_NOIDLE)
 
 #define BLK_MAX_CDB     16
 
@@ -633,6 +635,7 @@ static inline bool rq_is_sync(struct request *rq)
 }
 
 #define rq_is_meta(rq)          ((rq)->cmd_flags & REQ_RW_META)
+#define rq_noidle(rq)           ((rq)->cmd_flags & REQ_NOIDLE)
 
 static inline int blk_queue_full(struct request_queue *q, int sync)
 {