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authorMing Lei <ming.lei@redhat.com>2018-01-31 06:04:57 +0300
committerJens Axboe <axboe@kernel.dk>2018-01-31 06:18:28 +0300
commit86ff7c2a80cd357f6156a53b354f6a0b357dc0c9 (patch)
tree0c37adc6d0616685a3d9ce29bcf9f5d507c4b5c5 /drivers/nvme
parent0a4b6e2f80aad46fb55a5cf7b1664c0aef030ee0 (diff)
downloadlinux-86ff7c2a80cd357f6156a53b354f6a0b357dc0c9.tar.xz
blk-mq: introduce BLK_STS_DEV_RESOURCE
This status is returned from driver to block layer if device related resource is unavailable, but driver can guarantee that IO dispatch will be triggered in future when the resource is available. Convert some drivers to return BLK_STS_DEV_RESOURCE. Also, if driver returns BLK_STS_RESOURCE and SCHED_RESTART is set, rerun queue after a delay (BLK_MQ_DELAY_QUEUE) to avoid IO stalls. BLK_MQ_DELAY_QUEUE is 3 ms because both scsi-mq and nvmefc are using that magic value. If a driver can make sure there is in-flight IO, it is safe to return BLK_STS_DEV_RESOURCE because: 1) If all in-flight IOs complete before examining SCHED_RESTART in blk_mq_dispatch_rq_list(), SCHED_RESTART must be cleared, so queue is run immediately in this case by blk_mq_dispatch_rq_list(); 2) if there is any in-flight IO after/when examining SCHED_RESTART in blk_mq_dispatch_rq_list(): - if SCHED_RESTART isn't set, queue is run immediately as handled in 1) - otherwise, this request will be dispatched after any in-flight IO is completed via blk_mq_sched_restart() 3) if SCHED_RESTART is set concurently in context because of BLK_STS_RESOURCE, blk_mq_delay_run_hw_queue() will cover the above two cases and make sure IO hang can be avoided. One invariant is that queue will be rerun if SCHED_RESTART is set. Suggested-by: Jens Axboe <axboe@kernel.dk> Tested-by: Laurence Oberman <loberman@redhat.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'drivers/nvme')
-rw-r--r--drivers/nvme/host/fc.c12
1 files changed, 2 insertions, 10 deletions
diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
index 99bf51c7e513..b856d7c919d2 100644
--- a/drivers/nvme/host/fc.c
+++ b/drivers/nvme/host/fc.c
@@ -35,8 +35,6 @@ enum nvme_fc_queue_flags {
NVME_FC_Q_LIVE,
};
-#define NVMEFC_QUEUE_DELAY 3 /* ms units */
-
#define NVME_FC_DEFAULT_DEV_LOSS_TMO 60 /* seconds */
struct nvme_fc_queue {
@@ -2231,7 +2229,7 @@ nvme_fc_start_fcp_op(struct nvme_fc_ctrl *ctrl, struct nvme_fc_queue *queue,
* the target device is present
*/
if (ctrl->rport->remoteport.port_state != FC_OBJSTATE_ONLINE)
- goto busy;
+ return BLK_STS_RESOURCE;
if (!nvme_fc_ctrl_get(ctrl))
return BLK_STS_IOERR;
@@ -2311,16 +2309,10 @@ nvme_fc_start_fcp_op(struct nvme_fc_ctrl *ctrl, struct nvme_fc_queue *queue,
ret != -EBUSY)
return BLK_STS_IOERR;
- goto busy;
+ return BLK_STS_RESOURCE;
}
return BLK_STS_OK;
-
-busy:
- if (!(op->flags & FCOP_FLAGS_AEN) && queue->hctx)
- blk_mq_delay_run_hw_queue(queue->hctx, NVMEFC_QUEUE_DELAY);
-
- return BLK_STS_RESOURCE;
}
static inline blk_status_t nvme_fc_is_ready(struct nvme_fc_queue *queue,