diff options
| author | Ming Lei <ming.lei@redhat.com> | 2017-11-04 09:55:34 +0800 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2017-11-04 08:19:25 -0600 |
| commit | 826a70a08b1210bbfdbda812ab43eb986e25b5c2 (patch) | |
| tree | 34ffcdb1ac15fef880c93219cc4f5df4fe1785c8 | |
| parent | e4f36b249b4d4e7599f1cf0c8fb50f196e52677e (diff) | |
SCSI: don't get target/host busy_count in scsi_mq_get_budget()
It is very expensive to atomic_inc/atomic_dec the host wide counter of
host->busy_count, and it should have been avoided via blk-mq's mechanism
of getting driver tag, which uses the more efficient way of sbitmap queue.
Also we don't check atomic_read(&sdev->device_busy) in scsi_mq_get_budget()
and don't run queue if the counter becomes zero, so IO hang may be caused
if all requests are completed just before the current SCSI device
is added to shost->starved_list.
Fixes: 0df21c86bdbf(scsi: implement .get_budget and .put_budget for blk-mq)
Reported-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | drivers/scsi/scsi_lib.c | 29 |
1 files changed, 13 insertions, 16 deletions
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 6f10afaca25b..22a7e4c47207 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -1950,11 +1950,7 @@ static void scsi_mq_put_budget(struct blk_mq_hw_ctx *hctx) { struct request_queue *q = hctx->queue; struct scsi_device *sdev = q->queuedata; - struct Scsi_Host *shost = sdev->host; - atomic_dec(&shost->host_busy); - if (scsi_target(sdev)->can_queue > 0) - atomic_dec(&scsi_target(sdev)->target_busy); atomic_dec(&sdev->device_busy); put_device(&sdev->sdev_gendev); } @@ -1963,7 +1959,6 @@ static blk_status_t scsi_mq_get_budget(struct blk_mq_hw_ctx *hctx) { struct request_queue *q = hctx->queue; struct scsi_device *sdev = q->queuedata; - struct Scsi_Host *shost = sdev->host; blk_status_t ret; ret = prep_to_mq(scsi_prep_state_check(sdev, NULL)); @@ -1974,18 +1969,9 @@ static blk_status_t scsi_mq_get_budget(struct blk_mq_hw_ctx *hctx) goto out; if (!scsi_dev_queue_ready(q, sdev)) goto out_put_device; - if (!scsi_target_queue_ready(shost, sdev)) - goto out_dec_device_busy; - if (!scsi_host_queue_ready(q, shost, sdev)) - goto out_dec_target_busy; return BLK_STS_OK; -out_dec_target_busy: - if (scsi_target(sdev)->can_queue > 0) - atomic_dec(&scsi_target(sdev)->target_busy); -out_dec_device_busy: - atomic_dec(&sdev->device_busy); out_put_device: put_device(&sdev->sdev_gendev); out: @@ -1998,6 +1984,7 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req = bd->rq; struct request_queue *q = req->q; struct scsi_device *sdev = q->queuedata; + struct Scsi_Host *shost = sdev->host; struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req); blk_status_t ret; int reason; @@ -2007,10 +1994,15 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx, goto out_put_budget; ret = BLK_STS_RESOURCE; + if (!scsi_target_queue_ready(shost, sdev)) + goto out_put_budget; + if (!scsi_host_queue_ready(q, shost, sdev)) + goto out_dec_target_busy; + if (!(req->rq_flags & RQF_DONTPREP)) { ret = prep_to_mq(scsi_mq_prep_fn(req)); if (ret != BLK_STS_OK) - goto out_put_budget; + goto out_dec_host_busy; req->rq_flags |= RQF_DONTPREP; } else { blk_mq_start_request(req); @@ -2028,11 +2020,16 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx, if (reason) { scsi_set_blocked(cmd, reason); ret = BLK_STS_RESOURCE; - goto out_put_budget; + goto out_dec_host_busy; } return BLK_STS_OK; +out_dec_host_busy: + atomic_dec(&shost->host_busy); +out_dec_target_busy: + if (scsi_target(sdev)->can_queue > 0) + atomic_dec(&scsi_target(sdev)->target_busy); out_put_budget: scsi_mq_put_budget(hctx); switch (ret) { |