[PATCH 1/6] scsi: mpt3sas: don't use .device_busy in device reset routine

[Ming Lei <ming.lei@redhat.com>]

scsih_dev_reset() uses scsi_device->device_busy to check if there is
inflight commands aimed to this LUN.

Uses block layer's helper of blk_mq_tagset_busy_iter() to do that, so
we can prepare for bypassing .device_busy for SSD since it is quite
expensive to inc/dec the global atomic counter in IO path.

With this change, no driver uses scsi_device->device_busy any more.

Cc: Sathya Prakash <sathya.prakash@broadcom.com>
Cc: Chaitra P B <chaitra.basappa@broadcom.com>
Cc: Suganath Prabu Subramani <suganath-prabu.subramani@broadcom.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumit Saxena <sumit.saxena@broadcom.com>
Cc: Shivasharan S <shivasharan.srikanteshwara@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/scsi/mpt3sas/mpt3sas_scsih.c | 32 +++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/mpt3sas/mpt3sas_scsih.c b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
index c597d544eb39..91766c172d8f 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_scsih.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
@@ -2994,6 +2994,36 @@ scsih_abort(struct scsi_cmnd *scmd)
 	return r;
 }
 
+struct device_busy {
+	struct scsi_device *dev;
+	unsigned int cnt;
+};
+
+static bool scsi_device_check_in_flight(struct request *rq, void *data,
+				      bool reserved)
+{
+	struct device_busy *busy = data;
+	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
+
+	if (test_bit(SCMD_STATE_INFLIGHT, &cmd->state) && cmd->device ==
+			busy->dev)
+		(busy->cnt)++;
+
+	return true;
+}
+
+static bool scsih_dev_busy(struct scsi_device *device)
+{
+	struct device_busy data = {
+		.dev =	device,
+		.cnt = 0,
+	};
+
+	blk_mq_tagset_busy_iter(&device->host->tag_set,
+				scsi_device_check_in_flight, &data);
+	return data.cnt > 0;
+}
+
 /**
  * scsih_dev_reset - eh threads main device reset routine
  * @scmd: pointer to scsi command object
@@ -3060,7 +3090,7 @@ scsih_dev_reset(struct scsi_cmnd *scmd)
 		MPI2_SCSITASKMGMT_TASKTYPE_LOGICAL_UNIT_RESET, 0, 0,
 		tr_timeout, tr_method);
 	/* Check for busy commands after reset */
-	if (r == SUCCESS && atomic_read(&scmd->device->device_busy))
+	if (r == SUCCESS && scsih_dev_busy(scmd->device))
 		r = FAILED;
  out:
 	sdev_printk(KERN_INFO, scmd->device, "device reset: %s scmd(0x%p)\n",
-- 
2.20.1