[PATCH 19/21] ufs: Request sense data asynchronously

[Bart Van Assche <bvanassche@acm.org>]

Clearing a unit attention synchronously from inside the UFS error handler
may trigger the following deadlock:
- ufshcd_err_handler() calls ufshcd_err_handling_unprepare() and the latter
  function calls ufshcd_clear_ua_wluns().
- ufshcd_clear_ua_wluns() submits a REQUEST SENSE command and that command
  activates the SCSI error handler.
- The SCSI error handler calls ufshcd_host_reset_and_restore().
- ufshcd_host_reset_and_restore() executes the following code:
  ufshcd_schedule_eh_work(hba);
  flush_work(&hba->eh_work);

This sequence results in a deadlock (circular wait). Fix this by requesting
sense data asynchronously.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Stanley Chu <stanley.chu@mediatek.com>
Cc: Can Guo <cang@codeaurora.org>
Cc: Asutosh Das <asutoshd@codeaurora.org>
Cc: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/ufs/ufshcd.c | 64 ++++++++++++++++++++-------------------
 1 file changed, 33 insertions(+), 31 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 250d46ab3584..a74862813140 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -7815,8 +7815,39 @@ static int ufshcd_add_lus(struct ufs_hba *hba)
 	return ret;
 }
 
+static void ufshcd_request_sense_done(struct request *rq, blk_status_t error)
+{
+	if (error != BLK_STS_OK)
+		pr_err("%s: REQUEST SENSE failed (%d)", __func__, error);
+	blk_put_request(rq);
+}
+
 static int
-ufshcd_send_request_sense(struct ufs_hba *hba, struct scsi_device *sdp);
+ufshcd_request_sense_async(struct ufs_hba *hba, struct scsi_device *sdev)
+{
+	/*
+	 * From SPC-6: the REQUEST SENSE command with any allocation length
+	 * clears the sense data.
+	 */
+	static const u8 cmd[6] = {REQUEST_SENSE, 0, 0, 0, 0, 0};
+	struct scsi_request *rq;
+	struct request *req;
+
+	req = blk_get_request(sdev->request_queue, REQ_OP_SCSI_IN, /*flags=*/0);
+	if (IS_ERR(req))
+		return PTR_ERR(req);
+
+	rq = scsi_req(req);
+	rq->cmd_len = ARRAY_SIZE(cmd);
+	memcpy(rq->cmd, cmd, rq->cmd_len);
+	rq->retries = 3;
+	req->timeout = 1 * HZ;
+	req->rq_flags |= RQF_PM | RQF_QUIET;
+
+	blk_execute_rq_nowait(/*bd_disk=*/NULL, req, /*at_head=*/true,
+			      ufshcd_request_sense_done);
+	return 0;
+}
 
 static int ufshcd_clear_ua_wlun(struct ufs_hba *hba, u8 wlun)
 {
@@ -7844,7 +7875,7 @@ static int ufshcd_clear_ua_wlun(struct ufs_hba *hba, u8 wlun)
 	if (ret)
 		goto out_err;
 
-	ret = ufshcd_send_request_sense(hba, sdp);
+	ret = ufshcd_request_sense_async(hba, sdp);
 	scsi_device_put(sdp);
 out_err:
 	if (ret)
@@ -8439,35 +8470,6 @@ static void ufshcd_hba_exit(struct ufs_hba *hba)
 	}
 }
 
-static int
-ufshcd_send_request_sense(struct ufs_hba *hba, struct scsi_device *sdp)
-{
-	unsigned char cmd[6] = {REQUEST_SENSE,
-				0,
-				0,
-				0,
-				UFS_SENSE_SIZE,
-				0};
-	char *buffer;
-	int ret;
-
-	buffer = kzalloc(UFS_SENSE_SIZE, GFP_KERNEL);
-	if (!buffer) {
-		ret = -ENOMEM;
-		goto out;
-	}
-
-	ret = scsi_execute(sdp, cmd, DMA_FROM_DEVICE, buffer,
-			UFS_SENSE_SIZE, NULL, NULL,
-			msecs_to_jiffies(1000), 3, 0, RQF_PM, NULL);
-	if (ret)
-		pr_err("%s: failed with err %d\n", __func__, ret);
-
-	kfree(buffer);
-out:
-	return ret;
-}
-
 /**
  * ufshcd_set_dev_pwr_mode - sends START STOP UNIT command to set device
  *			     power mode