scsi_device's refcount is always grabbed in IO path.
Turns out it isn't necessary, because blk_queue_cleanup() will
drain any in-flight IOs, then cancel timeout/requeue work, and
SCSI's requeue_work is canceled too in __scsi_remove_device().
Also scsi_device won't go away until blk_cleanup_queue() is done.
So don't hold the refcount in IO path, especially the refcount isn't
required in IO path since blk_queue_enter() / blk_queue_exit()
is introduced in the legacy block layer.
Cc: Dongli Zhang <dongli.zhang@xxxxxxxxxx>
Cc: James Smart <james.smart@xxxxxxxxxxxx>
Cc: Bart Van Assche <bart.vanassche@xxxxxxx>
Cc: linux-scsi@xxxxxxxxxxxxxxx,
Cc: Martin K . Petersen <martin.petersen@xxxxxxxxxx>,
Cc: Christoph Hellwig <hch@xxxxxx>,
Cc: James E . J . Bottomley <jejb@xxxxxxxxxxxxxxxxxx>,
Cc: jianchao wang <jianchao.w.wang@xxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
drivers/scsi/scsi_lib.c | 30 ++++++------------------------
1 file changed, 6 insertions(+), 24 deletions(-)
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 601b9f1de267..6772d2ae1357 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -141,8 +141,6 @@ scsi_set_blocked(struct scsi_cmnd *cmd, int reason)
static void scsi_mq_requeue_cmd(struct scsi_cmnd *cmd)
{
- struct scsi_device *sdev = cmd->device;
-
if (cmd->request->rq_flags & RQF_DONTPREP) {
cmd->request->rq_flags &= ~RQF_DONTPREP;
scsi_mq_uninit_cmd(cmd);
@@ -150,7 +148,6 @@ static void scsi_mq_requeue_cmd(struct scsi_cmnd *cmd)
WARN_ON_ONCE(true);
}
blk_mq_requeue_request(cmd->request, true);
- put_device(&sdev->sdev_gendev);
}
/**
@@ -190,18 +187,12 @@ static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, bool unbusy)
cmd->result = 0;
/*
- * Before a SCSI command is dispatched,
- * get_device(&sdev->sdev_gendev) is called and the host,
- * target and device busy counters are increased. Since
- * requeuing a request causes these actions to be repeated and
- * since scsi_device_unbusy() has already been called,
- * put_device(&device->sdev_gendev) must still be called. Call
- * put_device() after blk_mq_requeue_request() to avoid that
- * removal of the SCSI device can start before requeueing has
- * happened.
+ * Before a SCSI command is dispatched, the host, target and
+ * device busy counters are increased. Since requeuing a request
+ * causes these actions to be repeated and since scsi_device_unbusy()
+ * has already been called.
*/
blk_mq_requeue_request(cmd->request, true);
- put_device(&device->sdev_gendev);
}
/*
@@ -619,7 +610,6 @@ static bool scsi_end_request(struct request *req, blk_status_t error,
blk_mq_run_hw_queues(q, true);
percpu_ref_put(&q->q_usage_counter);
- put_device(&sdev->sdev_gendev);
return false;
}
@@ -1613,7 +1603,6 @@ static void scsi_mq_put_budget(struct blk_mq_hw_ctx *hctx)
struct scsi_device *sdev = q->queuedata;
atomic_dec(&sdev->device_busy);
- put_device(&sdev->sdev_gendev);
}
static bool scsi_mq_get_budget(struct blk_mq_hw_ctx *hctx)
@@ -1621,16 +1610,9 @@ static bool scsi_mq_get_budget(struct blk_mq_hw_ctx *hctx)
struct request_queue *q = hctx->queue;
struct scsi_device *sdev = q->queuedata;
- if (!get_device(&sdev->sdev_gendev))
- goto out;
- if (!scsi_dev_queue_ready(q, sdev))
- goto out_put_device;
-
- return true;
+ if (scsi_dev_queue_ready(q, sdev))
+ return true;
-out_put_device:
- put_device(&sdev->sdev_gendev);
-out:
if (atomic_read(&sdev->device_busy) == 0 && !scsi_device_blocked(sdev))
blk_mq_delay_run_hw_queue(hctx, SCSI_QUEUE_DELAY);
return false;
--
2.9.5
