diff options
Diffstat (limited to 'block/blk.h')
| -rw-r--r-- | block/blk.h | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/block/blk.h b/block/blk.h index c9df8fc3c999..83e4bff36201 100644 --- a/block/blk.h +++ b/block/blk.h @@ -62,7 +62,26 @@ static inline struct request *__elv_next_request(struct request_queue *q) rq = list_entry_rq(q->queue_head.next); return rq; } - + /* + * Flush request is running and flush request isn't queueable + * in the drive, we can hold the queue till flush request is + * finished. Even we don't do this, driver can't dispatch next + * requests and will requeue them. And this can improve + * throughput too. For example, we have request flush1, write1, + * flush 2. flush1 is dispatched, then queue is hold, write1 + * isn't inserted to queue. After flush1 is finished, flush2 + * will be dispatched. Since disk cache is already clean, + * flush2 will be finished very soon, so looks like flush2 is + * folded to flush1. + * Since the queue is hold, a flag is set to indicate the queue + * should be restarted later. Please see flush_end_io() for + * details. + */ + if (q->flush_pending_idx != q->flush_running_idx && + !queue_flush_queueable(q)) { + q->flush_queue_delayed = 1; + return NULL; + } if (!q->elevator->ops->elevator_dispatch_fn(q, 0)) return NULL; } |