[PATCH BUGFIX IMPROVEMENT 09/14] block, bfq: fix sequential rq detection in rate estimation

[Paolo Valente]

In bfq_update_peak_rate, to check whether an I/O request rq is
sequential, only the seek distance of rq w.r.t. the last request
dispatched is controlled. This is not sufficient for non-rotational
storage, where the size of rq is at least as relevant. This commit
adds the missing control.

Signed-off-by: Paolo Valente <paolo.vale...@linaro.org>
---
 block/bfq-iosched.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index c1bb5e5fcdc4..12228af16198 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -235,6 +235,11 @@ static struct kmem_cache *bfq_pool;
 
 #define BFQQ_SEEK_THR          (sector_t)(8 * 100)
 #define BFQQ_SECT_THR_NONROT   (sector_t)(2 * 32)
+#define BFQ_RQ_SEEKY(bfqd, last_pos, rq) \
+       (get_sdist(last_pos, rq) >                      \
+        BFQQ_SEEK_THR &&                               \
+        (!blk_queue_nonrot(bfqd->queue) ||             \
+         blk_rq_sectors(rq) < BFQQ_SECT_THR_NONROT))
 #define BFQQ_CLOSE_THR         (sector_t)(8 * 1024)
 #define BFQQ_SEEKY(bfqq)       (hweight32(bfqq->seek_history) > 19)
 
@@ -2754,7 +2759,7 @@ static void bfq_update_peak_rate(struct bfq_data *bfqd, 
struct request *rq)
 
        if ((bfqd->rq_in_driver > 0 ||
                now_ns - bfqd->last_completion < BFQ_MIN_TT)
-            && get_sdist(bfqd->last_position, rq) < BFQQ_SEEK_THR)
+           && !BFQ_RQ_SEEKY(bfqd, bfqd->last_position, rq))
                bfqd->sequential_samples++;
 
        bfqd->tot_sectors_dispatched += blk_rq_sectors(rq);
@@ -4511,10 +4516,7 @@ bfq_update_io_seektime(struct bfq_data *bfqd, struct 
bfq_queue *bfqq,
                       struct request *rq)
 {
        bfqq->seek_history <<= 1;
-       bfqq->seek_history |=
-               get_sdist(bfqq->last_request_pos, rq) > BFQQ_SEEK_THR &&
-               (!blk_queue_nonrot(bfqd->queue) ||
-                blk_rq_sectors(rq) < BFQQ_SECT_THR_NONROT);
+       bfqq->seek_history |= BFQ_RQ_SEEKY(bfqd, bfqq->last_request_pos, rq);
 }
 
 static void bfq_update_has_short_ttime(struct bfq_data *bfqd,
-- 
2.20.1