block, bfq: add missing rq_pos_tree update on rq removal

If two processes do I/O close to each other, then BFQ merges the
bfq_queues associated with these processes, to get a more sequential
I/O, and thus a higher throughput.  In this respect, to detect whether
two processes are doing I/O close to each other, BFQ keeps a list of
the head-of-line I/O requests of all active bfq_queues.  The list is
ordered by initial sectors, and implemented through a red-black tree
(rq_pos_tree).

Unfortunately, the update of the rq_pos_tree was incomplete, because
the tree was not updated on the removal of the head-of-line I/O
request of a bfq_queue, in case the queue did not remain empty. This
commit adds the missing update.

Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Angelo Ruocco <angeloruocco90@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 0f48583b93806ba07cef4829ba397f32c55ad1b9..fa395a260a2356ebade2dc974cd7dd6369d1dac2 100644 (file)
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -1627,6 +1627,8 @@ static void bfq_remove_request(struct request_queue *q,
                        rb_erase(&bfqq->pos_node, bfqq->pos_root);
                        bfqq->pos_root = NULL;
                }
+       } else {
+               bfq_pos_tree_add_move(bfqd, bfqq);
        }
 
        if (rq->cmd_flags & REQ_META)