On 04/17/2015 03:42 PM, James Bottomley wrote:
@@ -662,32 +662,14 @@ void scsi_finish_command(struct scsi_cmnd *cmd) */ int scsi_change_queue_depth(struct scsi_device *sdev, int depth) { - unsigned long flags; - - if (depth <= 0) - goto out; - - spin_lock_irqsave(sdev->request_queue->queue_lock, flags); + if (depth > 0) { + unsigned long flags; - /* - * Check to see if the queue is managed by the block layer. - * If it is, and we fail to adjust the depth, exit. - * - * Do not resize the tag map if it is a host wide share bqt, - * because the size should be the hosts's can_queue. If there - * is more IO than the LLD's can_queue (so there are not enuogh - * tags) request_fn's host queue ready check will handle it. - */ - if (!shost_use_blk_mq(sdev->host) && !sdev->host->bqt) { - if (blk_queue_tagged(sdev->request_queue) && - blk_queue_resize_tags(sdev->request_queue, depth) != 0) - goto out_unlock; + spin_lock_irqsave(sdev->request_queue->queue_lock, flags); + sdev->queue_depth = depth; + spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags);This lock/unlock is a nasty global sync point which can be eliminated: we can rely on the architectural atomicity of 32 bit writes (might need to make sdev->queue_depth a u32 because I seem to remember 16 bit writes had to be done as two byte stores on some architectures).
It's not in a hot path (by any stretch), so doesn't really matter... -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
