block: add queue flag for SSD/non-rotational devices

We don't want to idle in AS/CFQ if the device doesn't have a seek
penalty. So add a QUEUE_FLAG_NONROT to indicate a non-rotational
device, low level drivers should set this flag upon discovery of
an SSD or similar device type.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

3 files changed, 14 insertions, 0 deletions

diff --git a/block/as-iosched.c b/block/as-iosched.c
index 80af9257e64a..4c6fafbba933 100644
--- a/block/as-iosched.c
+++ b/block/as-iosched.c
@@ -745,6 +745,12 @@ static int as_can_break_anticipation(struct as_data *ad, struct request *rq)
  */
 static int as_can_anticipate(struct as_data *ad, struct request *rq)
 {
+        /*
+         * SSD device without seek penalty, disable idling
+         */
+        if (blk_queue_nonrot(ad->q))
+                return 0;
+
         if (!ad->io_context)
                 /*
                  * Last request submitted was a write
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 494b6fdcb183..03a5953bb5df 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -878,6 +878,12 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
         struct cfq_io_context *cic;
         unsigned long sl;
 
+        /*
+         * SSD device without seek penalty, disable idling
+         */
+        if (blk_queue_nonrot(cfqd->queue))
+                return;
+
         WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
         WARN_ON(cfq_cfqq_slice_new(cfqq));
 
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 86f77ef127f4..0cf3e619fb21 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -442,6 +442,7 @@ struct request_queue
 #define QUEUE_FLAG_SAME_COMP   11       /* force complete on same CPU */
 #define QUEUE_FLAG_FAIL_IO     12       /* fake timeout */
 #define QUEUE_FLAG_STACKABLE   13       /* supports request stacking */
+#define QUEUE_FLAG_NONROT      14       /* non-rotational device (SSD) */
 
 static inline int queue_is_locked(struct request_queue *q)
 {
@@ -547,6 +548,7 @@ enum {
 #define blk_queue_tagged(q)     test_bit(QUEUE_FLAG_QUEUED, &(q)->queue_flags)
 #define blk_queue_stopped(q)    test_bit(QUEUE_FLAG_STOPPED, &(q)->queue_flags)
 #define blk_queue_nomerges(q)   test_bit(QUEUE_FLAG_NOMERGES, &(q)->queue_flags)
+#define blk_queue_nonrot(q)     test_bit(QUEUE_FLAG_NONROT, &(q)->queue_flags)
 #define blk_queue_flushing(q)   ((q)->ordseq)
 #define blk_queue_stackable(q)  \
         test_bit(QUEUE_FLAG_STACKABLE, &(q)->queue_flags)