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scsi: core: don't hold device refcount in IO path

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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@oracle.com>
Cc: James Smart <james.smart@broadcom.com>
Cc: Bart Van Assche <bart.vanassche@wdc.com>
Cc: linux-scsi@vger.kernel.org,
Cc: Martin K . Petersen <martin.petersen@oracle.com>,
Cc: Christoph Hellwig <hch@lst.de>,
Cc: James E . J . Bottomley <jejb@linux.vnet.ibm.com>,
Cc: jianchao wang <jianchao.w.wang@oracle.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Ming Lei
2019-04-12 11:30:32 +08:00
committed by Martin K. Petersen
parent 1710ac1754
commit 18c4f0a42b
1 changed files with 2 additions and 26 deletions
Download Patch File Download Diff File Expand all files Collapse all files

28
drivers/scsi/scsi_lib.c
View File

@@ -141,8 +141,6 @@ scsi_set_blocked(struct scsi_cmnd *cmd, int reason)
static void scsi_mq_requeue_cmd(struct scsi_cmnd *cmd) static void scsi_mq_requeue_cmd(struct scsi_cmnd *cmd)
{ {
struct scsi_device *sdev = cmd->device;
if (cmd->request->rq_flags & RQF_DONTPREP) { if (cmd->request->rq_flags & RQF_DONTPREP) {
cmd->request->rq_flags &= ~RQF_DONTPREP; cmd->request->rq_flags &= ~RQF_DONTPREP;
scsi_mq_uninit_cmd(cmd); scsi_mq_uninit_cmd(cmd);
@@ -150,7 +148,6 @@ static void scsi_mq_requeue_cmd(struct scsi_cmnd *cmd)
WARN_ON_ONCE(true); WARN_ON_ONCE(true);
} }
blk_mq_requeue_request(cmd->request, true); blk_mq_requeue_request(cmd->request, true);
put_device(&sdev->sdev_gendev);
} }
/** /**
@@ -189,19 +186,7 @@ static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, bool unbusy)
*/ */
cmd->result = 0; 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.
*/
blk_mq_requeue_request(cmd->request, true); blk_mq_requeue_request(cmd->request, true);
put_device(&device->sdev_gendev);
} }
/* /*
@@ -619,7 +604,6 @@ static bool scsi_end_request(struct request *req, blk_status_t error,
blk_mq_run_hw_queues(q, true); blk_mq_run_hw_queues(q, true);
percpu_ref_put(&q->q_usage_counter); percpu_ref_put(&q->q_usage_counter);
put_device(&sdev->sdev_gendev);
return false; return false;
} }
@@ -1613,7 +1597,6 @@ static void scsi_mq_put_budget(struct blk_mq_hw_ctx *hctx)
struct scsi_device *sdev = q->queuedata; struct scsi_device *sdev = q->queuedata;
atomic_dec(&sdev->device_busy); atomic_dec(&sdev->device_busy);
put_device(&sdev->sdev_gendev);
} }
static bool scsi_mq_get_budget(struct blk_mq_hw_ctx *hctx) static bool scsi_mq_get_budget(struct blk_mq_hw_ctx *hctx)
@@ -1621,16 +1604,9 @@ static bool scsi_mq_get_budget(struct blk_mq_hw_ctx *hctx)
struct request_queue *q = hctx->queue; struct request_queue *q = hctx->queue;
struct scsi_device *sdev = q->queuedata; struct scsi_device *sdev = q->queuedata;
if (!get_device(&sdev->sdev_gendev)) if (scsi_dev_queue_ready(q, sdev))
goto out; return true;
if (!scsi_dev_queue_ready(q, sdev))
goto out_put_device;
return true;
out_put_device:
put_device(&sdev->sdev_gendev);
out:
if (atomic_read(&sdev->device_busy) == 0 && !scsi_device_blocked(sdev)) if (atomic_read(&sdev->device_busy) == 0 && !scsi_device_blocked(sdev))
blk_mq_delay_run_hw_queue(hctx, SCSI_QUEUE_DELAY); blk_mq_delay_run_hw_queue(hctx, SCSI_QUEUE_DELAY);
return false; return false;