scsi: sd: Fix TCG OPAL unlock on system resume

Commit 3cc2ffe5c16d ("scsi: sd: Differentiate system and runtime start/stop
management") introduced the manage_system_start_stop scsi_device flag to
allow libata to indicate to the SCSI disk driver that nothing should be
done when resuming a disk on system resume. This change turned the
execution of sd_resume() into a no-op for ATA devices on system
resume. While this solved deadlock issues during device resume, this change
also wrongly removed the execution of opal_unlock_from_suspend(). As a
result, devices with TCG OPAL locking enabled remain locked and
inaccessible after a system resume from sleep.

To fix this issue, introduce the SCSI driver resume method and implement it
with the sd_resume() function calling opal_unlock_from_suspend(). The
former sd_resume() function is renamed to sd_resume_common() and modified
to call the new sd_resume() function. For non-ATA devices, this result in
no functional changes.

In order for libata to explicitly execute sd_resume() when a device is
resumed during system restart, the function scsi_resume_device() is
introduced. libata calls this function from the revalidation work executed
on devie resume, a state that is indicated with the new device flag
ATA_DFLAG_RESUMING. Doing so, locked TCG OPAL enabled devices are unlocked
on resume, allowing normal operation.

Fixes: 3cc2ffe5c16d ("scsi: sd: Differentiate system and runtime start/stop management")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=218538
Cc: [e-mail]
Signed-off-by: Damien Le Moal <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/ata/libata-eh.c

···
 				ehc->saved_ncq_enabled |= 1 << devno;
 
 			/* If we are resuming, wake up the device */
-			if (ap->pflags & ATA_PFLAG_RESUMING)
+			if (ap->pflags & ATA_PFLAG_RESUMING) {
+				dev->flags |= ATA_DFLAG_RESUMING;
 				ehc->i.dev_action[devno] |= ATA_EH_SET_ACTIVE;
+			}
 		}
 	}
 
···
 	return 0;
 
  err:
+	dev->flags &= ~ATA_DFLAG_RESUMING;
 	*r_failed_dev = dev;
 	return rc;
 }

drivers/ata/libata-scsi.c

···
 	struct ata_link *link;
 	struct ata_device *dev;
 	unsigned long flags;
+	bool do_resume;
 	int ret = 0;
 
 	mutex_lock(&ap->scsi_scan_mutex);
···
 			if (scsi_device_get(sdev))
 				continue;
 
+			do_resume = dev->flags & ATA_DFLAG_RESUMING;
+
 			spin_unlock_irqrestore(ap->lock, flags);
+			if (do_resume) {
+				ret = scsi_resume_device(sdev);
+				if (ret == -EWOULDBLOCK)
+					goto unlock;
+				dev->flags &= ~ATA_DFLAG_RESUMING;
+			}
 			ret = scsi_rescan_device(sdev);
 			scsi_device_put(sdev);
 			spin_lock_irqsave(ap->lock, flags);

drivers/scsi/scsi_scan.c

···
 }
 EXPORT_SYMBOL(scsi_add_device);
 
+int scsi_resume_device(struct scsi_device *sdev)
+{
+	struct device *dev = &sdev->sdev_gendev;
+	int ret = 0;
+
+	device_lock(dev);
+
+	/*
+	 * Bail out if the device or its queue are not running. Otherwise,
+	 * the rescan may block waiting for commands to be executed, with us
+	 * holding the device lock. This can result in a potential deadlock
+	 * in the power management core code when system resume is on-going.
+	 */
+	if (sdev->sdev_state != SDEV_RUNNING ||
+	    blk_queue_pm_only(sdev->request_queue)) {
+		ret = -EWOULDBLOCK;
+		goto unlock;
+	}
+
+	if (dev->driver && try_module_get(dev->driver->owner)) {
+		struct scsi_driver *drv = to_scsi_driver(dev->driver);
+
+		if (drv->resume)
+			ret = drv->resume(dev);
+		module_put(dev->driver->owner);
+	}
+
+unlock:
+	device_unlock(dev);
+
+	return ret;
+}
+EXPORT_SYMBOL(scsi_resume_device);
+
 int scsi_rescan_device(struct scsi_device *sdev)
 {
 	struct device *dev = &sdev->sdev_gendev;

drivers/scsi/sd.c

···
 	return sd_suspend_common(dev, true);
 }
 
-static int sd_resume(struct device *dev, bool runtime)
+static int sd_resume(struct device *dev)
+{
+	struct scsi_disk *sdkp = dev_get_drvdata(dev);
+
+	sd_printk(KERN_NOTICE, sdkp, "Starting disk\n");
+
+	if (opal_unlock_from_suspend(sdkp->opal_dev)) {
+		sd_printk(KERN_NOTICE, sdkp, "OPAL unlock failed\n");
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int sd_resume_common(struct device *dev, bool runtime)
 {
 	struct scsi_disk *sdkp = dev_get_drvdata(dev);
 	int ret;
···
 	sd_printk(KERN_NOTICE, sdkp, "Starting disk\n");
 	ret = sd_start_stop_device(sdkp, 1);
 	if (!ret) {
-		opal_unlock_from_suspend(sdkp->opal_dev);
+		sd_resume(dev);
 		sdkp->suspended = false;
 	}
 
···
 		return 0;
 	}
 
-	return sd_resume(dev, false);
+	return sd_resume_common(dev, false);
 }
 
 static int sd_resume_runtime(struct device *dev)
···
 				  "Failed to clear sense data\n");
 	}
 
-	return sd_resume(dev, true);
+	return sd_resume_common(dev, true);
 }
 
 static const struct dev_pm_ops sd_pm_ops = {
···
 		.pm		= &sd_pm_ops,
 	},
 	.rescan			= sd_rescan,
+	.resume			= sd_resume,
 	.init_command		= sd_init_command,
 	.uninit_command		= sd_uninit_command,
 	.done			= sd_done,

include/linux/libata.h

···
 
 	ATA_DFLAG_NCQ_PRIO_ENABLED = (1 << 20), /* Priority cmds sent to dev */
 	ATA_DFLAG_CDL_ENABLED	= (1 << 21), /* cmd duration limits is enabled */
+	ATA_DFLAG_RESUMING	= (1 << 22),  /* Device is resuming */
 	ATA_DFLAG_DETACH	= (1 << 24),
 	ATA_DFLAG_DETACHED	= (1 << 25),
 	ATA_DFLAG_DA		= (1 << 26), /* device supports Device Attention */

include/scsi/scsi_driver.h

···
 struct scsi_driver {
 	struct device_driver	gendrv;
 
+	int (*resume)(struct device *);
 	void (*rescan)(struct device *);
 	blk_status_t (*init_command)(struct scsi_cmnd *);
 	void (*uninit_command)(struct scsi_cmnd *);

include/scsi/scsi_host.h

···
 #define scsi_template_proc_dir(sht) NULL
 #endif
 extern void scsi_scan_host(struct Scsi_Host *);
+extern int scsi_resume_device(struct scsi_device *sdev);
 extern int scsi_rescan_device(struct scsi_device *sdev);
 extern void scsi_remove_host(struct Scsi_Host *);
 extern struct Scsi_Host *scsi_host_get(struct Scsi_Host *);