diff --git a/block/blk-mq.c b/block/blk-mq.c index 5c9adcaa27ac..eecb46020bfb 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1436,7 +1436,13 @@ static void __blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async, if (unlikely(blk_mq_hctx_stopped(hctx))) return; - if (!async && !(hctx->flags & BLK_MQ_F_BLOCKING)) { + /* + * Some single-queue devices may need to dispatch IO in order + * which was guaranteed for the legacy queue via the big queue + * lock. Now we reply on single hctx->run_work for that. + */ + if (!async && !(hctx->flags & (BLK_MQ_F_BLOCKING | + BLK_MQ_F_STRICT_DISPATCH_ORDER))) { int cpu = get_cpu(); if (cpumask_test_cpu(cpu, hctx->cpumask)) { __blk_mq_run_hw_queue(hctx); @@ -3042,6 +3048,10 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set) if (!set->ops->get_budget ^ !set->ops->put_budget) return -EINVAL; + if (set->queue_depth > 1 && (set->flags & + BLK_MQ_F_STRICT_DISPATCH_ORDER)) + return -EINVAL; + if (set->queue_depth > BLK_MQ_MAX_DEPTH) { pr_info("blk-mq: reduced tag depth to %u\n", BLK_MQ_MAX_DEPTH); diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index d3d237a09a78..563188844143 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -1939,6 +1939,9 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost) shost->tag_set.flags = BLK_MQ_F_SHOULD_MERGE; shost->tag_set.flags |= BLK_ALLOC_POLICY_TO_MQ_FLAG(shost->hostt->tag_alloc_policy); + if (shost->hostt->strict_dispatch_order) + shost->tag_set.flags |= BLK_MQ_F_STRICT_DISPATCH_ORDER; + shost->tag_set.driver_data = shost; return blk_mq_alloc_tag_set(&shost->tag_set); diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c index 6737fab94959..77795edad8e8 100644 --- a/drivers/usb/storage/scsiglue.c +++ b/drivers/usb/storage/scsiglue.c @@ -661,6 +661,18 @@ static const struct scsi_host_template usb_stor_host_template = { /* we do our own delay after a device or bus reset */ .skip_settle_delay = 1, + + /* + * Some USB storage, such as Kingston Technology DataTraveler 100 + * G3/G4/SE9 G2(ID 0951:1666), requires IO dispatched in the + * sequential order, otherwise IO performance may drop drastically. + * + * can_queue is always 1, so we set .strict_dispatch_order for + * USB mass storage HBA. Another reason is that there can be such + * kind of devices too. + */ + .strict_dispatch_order = 1, + /* sysfs device attributes */ .sdev_attrs = sysfs_device_attr_list, diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index dc03e059fdff..844539690a27 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -388,6 +388,7 @@ struct blk_mq_ops { enum { BLK_MQ_F_SHOULD_MERGE = 1 << 0, BLK_MQ_F_TAG_SHARED = 1 << 1, + BLK_MQ_F_STRICT_DISPATCH_ORDER = 1 << 2, BLK_MQ_F_BLOCKING = 1 << 5, BLK_MQ_F_NO_SCHED = 1 << 6, BLK_MQ_F_ALLOC_POLICY_START_BIT = 8, diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h index d4452d0ea3c7..f932d6fa1a4c 100644 --- a/include/scsi/scsi_host.h +++ b/include/scsi/scsi_host.h @@ -442,6 +442,13 @@ struct scsi_host_template { /* True if the low-level driver supports blk-mq only */ unsigned force_blk_mq:1; + /* + * True if the low-level driver needs IO to be dispatched in + * the order provided by legacy IO path. The flag is only + * valid for single queue device. + */ + unsigned strict_dispatch_order:1; + /* * Countdown for host blocking with no commands outstanding. */