diff options
| -rw-r--r-- | block/blk-flush.c | 16 | ||||
| -rw-r--r-- | block/blk.h | 21 | ||||
| -rw-r--r-- | include/linux/blkdev.h | 1 |
3 files changed, 32 insertions, 6 deletions
diff --git a/block/blk-flush.c b/block/blk-flush.c index 6c9b5e189e62..bb21e4c36f70 100644 --- a/block/blk-flush.c +++ b/block/blk-flush.c @@ -212,13 +212,19 @@ static void flush_end_io(struct request *flush_rq, int error) } /* - * Moving a request silently to empty queue_head may stall the - * queue. Kick the queue in those cases. This function is called - * from request completion path and calling directly into - * request_fn may confuse the driver. Always use kblockd. + * Kick the queue to avoid stall for two cases: + * 1. Moving a request silently to empty queue_head may stall the + * queue. + * 2. When flush request is running in non-queueable queue, the + * queue is hold. Restart the queue after flush request is finished + * to avoid stall. + * This function is called from request completion path and calling + * directly into request_fn may confuse the driver. Always use + * kblockd. */ - if (queued) + if (queued || q->flush_queue_delayed) blk_run_queue_async(q); + q->flush_queue_delayed = 0; } /** 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; } diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 8bd2a271b2d8..9f921bf4bf8c 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -365,6 +365,7 @@ struct request_queue */ unsigned int flush_flags; unsigned int flush_not_queueable:1; + unsigned int flush_queue_delayed:1; unsigned int flush_pending_idx:1; unsigned int flush_running_idx:1; unsigned long flush_pending_since; |