diff options
Diffstat (limited to 'block')
| -rw-r--r-- | block/blk-core.c | 28 | ||||
| -rw-r--r-- | block/blk-settings.c | 6 |
2 files changed, 34 insertions, 0 deletions
diff --git a/block/blk-core.c b/block/blk-core.c index c66333d8e48..b2d0ac8b760 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -2100,6 +2100,34 @@ void blk_rq_bio_prep(struct request_queue *q, struct request *rq, rq->rq_disk = bio->bi_bdev->bd_disk; } +/** + * blk_lld_busy - Check if underlying low-level drivers of a device are busy + * @q : the queue of the device being checked + * + * Description: + * Check if underlying low-level drivers of a device are busy. + * If the drivers want to export their busy state, they must set own + * exporting function using blk_queue_lld_busy() first. + * + * Basically, this function is used only by request stacking drivers + * to stop dispatching requests to underlying devices when underlying + * devices are busy. This behavior helps more I/O merging on the queue + * of the request stacking driver and prevents I/O throughput regression + * on burst I/O load. + * + * Return: + * 0 - Not busy (The request stacking driver should dispatch request) + * 1 - Busy (The request stacking driver should stop dispatching request) + */ +int blk_lld_busy(struct request_queue *q) +{ + if (q->lld_busy_fn) + return q->lld_busy_fn(q); + + return 0; +} +EXPORT_SYMBOL_GPL(blk_lld_busy); + int kblockd_schedule_work(struct request_queue *q, struct work_struct *work) { return queue_work(kblockd_workqueue, work); diff --git a/block/blk-settings.c b/block/blk-settings.c index 1d0330d0b40..b21dcdb6415 100644 --- a/block/blk-settings.c +++ b/block/blk-settings.c @@ -89,6 +89,12 @@ void blk_queue_rq_timed_out(struct request_queue *q, rq_timed_out_fn *fn) } EXPORT_SYMBOL_GPL(blk_queue_rq_timed_out); +void blk_queue_lld_busy(struct request_queue *q, lld_busy_fn *fn) +{ + q->lld_busy_fn = fn; +} +EXPORT_SYMBOL_GPL(blk_queue_lld_busy); + /** * blk_queue_make_request - define an alternate make_request function for a device * @q: the request queue for the device to be affected |