ufs: fix reference counting of W-LUs

UFS driver adds three well known LUs in the initialization, but those
reference counts are not decremented, so it makes ufshcd module
impossible to unload.

This fixes it by putting scsi_device_put() in the initalization, and in
order to protect concurrent access to hba->sdev_ufs_device (UFS Device
W-LU) from manual delete, increment the reference count while requesting
device power mode setting.

The rest of W-LUs (hba->sdev_boot and hba->sdev_rpmb) are not directly
used from driver, so these references in struct ufs_hba are removed.

Signed-off-by: Akinobu Mita <mita@fixstars.com>
Reviewed-by: Maya Erez <merez@codeaurora.org>
Reviewed-by: Dolev Raviv <draviv@codeaurora.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/scsi/ufs/ufshcd.c

@@ -2844,8 +2844,13 @@ static void ufshcd_slave_destroy(struct scsi_device *sdev)
 	hba = shost_priv(sdev->host);
 	scsi_deactivate_tcq(sdev, hba->nutrs);
 	/* Drop the reference as it won't be needed anymore */
-	if (ufshcd_scsi_to_upiu_lun(sdev->lun) == UFS_UPIU_UFS_DEVICE_WLUN)
+	if (ufshcd_scsi_to_upiu_lun(sdev->lun) == UFS_UPIU_UFS_DEVICE_WLUN) {
+		unsigned long flags;
+
+		spin_lock_irqsave(hba->host->host_lock, flags);
 		hba->sdev_ufs_device = NULL;
+		spin_unlock_irqrestore(hba->host->host_lock, flags);
+	}
 }
 
 /**
@@ -4062,6 +4067,8 @@ static void ufshcd_init_icc_levels(struct ufs_hba *hba)
 static int ufshcd_scsi_add_wlus(struct ufs_hba *hba)
 {
 	int ret = 0;
+	struct scsi_device *sdev_rpmb;
+	struct scsi_device *sdev_boot;
 
 	hba->sdev_ufs_device = __scsi_add_device(hba->host, 0, 0,
 		ufshcd_upiu_wlun_to_scsi_wlun(UFS_UPIU_UFS_DEVICE_WLUN), NULL);
@@ -4070,56 +4077,33 @@ static int ufshcd_scsi_add_wlus(struct ufs_hba *hba)
 		hba->sdev_ufs_device = NULL;
 		goto out;
 	}
+	scsi_device_put(hba->sdev_ufs_device);
 
-	hba->sdev_boot = __scsi_add_device(hba->host, 0, 0,
+	sdev_boot = __scsi_add_device(hba->host, 0, 0,
 		ufshcd_upiu_wlun_to_scsi_wlun(UFS_UPIU_BOOT_WLUN), NULL);
-	if (IS_ERR(hba->sdev_boot)) {
-		ret = PTR_ERR(hba->sdev_boot);
-		hba->sdev_boot = NULL;
+	if (IS_ERR(sdev_boot)) {
+		ret = PTR_ERR(sdev_boot);
 		goto remove_sdev_ufs_device;
 	}
+	scsi_device_put(sdev_boot);
 
-	hba->sdev_rpmb = __scsi_add_device(hba->host, 0, 0,
+	sdev_rpmb = __scsi_add_device(hba->host, 0, 0,
 		ufshcd_upiu_wlun_to_scsi_wlun(UFS_UPIU_RPMB_WLUN), NULL);
-	if (IS_ERR(hba->sdev_rpmb)) {
-		ret = PTR_ERR(hba->sdev_rpmb);
-		hba->sdev_rpmb = NULL;
+	if (IS_ERR(sdev_rpmb)) {
+		ret = PTR_ERR(sdev_rpmb);
 		goto remove_sdev_boot;
 	}
+	scsi_device_put(sdev_rpmb);
 	goto out;
 
 remove_sdev_boot:
-	scsi_remove_device(hba->sdev_boot);
+	scsi_remove_device(sdev_boot);
 remove_sdev_ufs_device:
 	scsi_remove_device(hba->sdev_ufs_device);
 out:
 	return ret;
 }
 
-/**
- * ufshcd_scsi_remove_wlus - Removes the W-LUs which were added by
- *			     ufshcd_scsi_add_wlus()
- * @hba: per-adapter instance
- *
- */
-static void ufshcd_scsi_remove_wlus(struct ufs_hba *hba)
-{
-	if (hba->sdev_ufs_device) {
-		scsi_remove_device(hba->sdev_ufs_device);
-		hba->sdev_ufs_device = NULL;
-	}
-
-	if (hba->sdev_boot) {
-		scsi_remove_device(hba->sdev_boot);
-		hba->sdev_boot = NULL;
-	}
-
-	if (hba->sdev_rpmb) {
-		scsi_remove_device(hba->sdev_rpmb);
-		hba->sdev_rpmb = NULL;
-	}
-}
-
 /**
  * ufshcd_probe_hba - probe hba to detect device and initialize
  * @hba: per-adapter instance
@@ -4675,11 +4659,25 @@ static int ufshcd_set_dev_pwr_mode(struct ufs_hba *hba,
 {
 	unsigned char cmd[6] = { START_STOP };
 	struct scsi_sense_hdr sshdr;
-	struct scsi_device *sdp = hba->sdev_ufs_device;
+	struct scsi_device *sdp;
+	unsigned long flags;
 	int ret;
 
-	if (!sdp || !scsi_device_online(sdp))
-		return -ENODEV;
+	spin_lock_irqsave(hba->host->host_lock, flags);
+	sdp = hba->sdev_ufs_device;
+	if (sdp) {
+		ret = scsi_device_get(sdp);
+		if (!ret && !scsi_device_online(sdp)) {
+			ret = -ENODEV;
+			scsi_device_put(sdp);
+		}
+	} else {
+		ret = -ENODEV;
+	}
+	spin_unlock_irqrestore(hba->host->host_lock, flags);
+
+	if (ret)
+		return ret;
 
 	/*
 	 * If scsi commands fail, the scsi mid-layer schedules scsi error-
@@ -4718,6 +4716,7 @@ static int ufshcd_set_dev_pwr_mode(struct ufs_hba *hba,
 	if (!ret)
 		hba->curr_dev_pwr_mode = pwr_mode;
 out:
+	scsi_device_put(sdp);
 	hba->host->eh_noresume = 0;
 	return ret;
 }
@@ -5231,7 +5230,6 @@ EXPORT_SYMBOL(ufshcd_shutdown);
 void ufshcd_remove(struct ufs_hba *hba)
 {
 	scsi_remove_host(hba->host);
-	ufshcd_scsi_remove_wlus(hba);
 	/* disable interrupts */
 	ufshcd_disable_intr(hba, hba->intr_mask);
 	ufshcd_hba_stop(hba);

drivers/scsi/ufs/ufshcd.h

@@ -392,8 +392,6 @@ struct ufs_hba {
 	 * "UFS device" W-LU.
 	 */
 	struct scsi_device *sdev_ufs_device;
-	struct scsi_device *sdev_rpmb;
-	struct scsi_device *sdev_boot;
 
 	enum ufs_dev_pwr_mode curr_dev_pwr_mode;
 	enum uic_link_state uic_link_state;