[S390] dasd: do path verification for paths added at runtime

When a new path is added at runtime, the CIO layer will call the drivers
path_event callback. The DASD device driver uses this callback to trigger
a path verification for the new path. The driver will use only those
paths for I/O, which have been successfully verified.

Signed-off-by: Stefan Weinhuber <wein@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

9 files changed, 418 insertions, 100 deletions

diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c
index 605f96f..8f2067b 100644
--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -913,6 +913,11 @@ int dasd_start_IO(struct dasd_ccw_req *cqr)
 	cqr->startclk = get_clock();
 	cqr->starttime = jiffies;
 	cqr->retries--;
+	if (!test_bit(DASD_CQR_VERIFY_PATH, &cqr->flags)) {
+		cqr->lpm &= device->path_data.opm;
+		if (!cqr->lpm)
+			cqr->lpm = device->path_data.opm;
+	}
 	if (cqr->cpmode == 1) {
 		rc = ccw_device_tm_start(device->cdev, cqr->cpaddr,
 					 (long) cqr, cqr->lpm);
@@ -925,35 +930,53 @@ int dasd_start_IO(struct dasd_ccw_req *cqr)
 		cqr->status = DASD_CQR_IN_IO;
 		break;
 	case -EBUSY:
-		DBF_DEV_EVENT(DBF_DEBUG, device, "%s",
+		DBF_DEV_EVENT(DBF_WARNING, device, "%s",
 			      "start_IO: device busy, retry later");
 		break;
 	case -ETIMEDOUT:
-		DBF_DEV_EVENT(DBF_DEBUG, device, "%s",
+		DBF_DEV_EVENT(DBF_WARNING, device, "%s",
 			      "start_IO: request timeout, retry later");
 		break;
 	case -EACCES:
-		/* -EACCES indicates that the request used only a
-		 * subset of the available pathes and all these
-		 * pathes are gone.
-		 * Do a retry with all available pathes.
+		/* -EACCES indicates that the request used only a subset of the
+		 * available paths and all these paths are gone. If the lpm of
+		 * this request was only a subset of the opm (e.g. the ppm) then
+		 * we just do a retry with all available paths.
+		 * If we already use the full opm, something is amiss, and we
+		 * need a full path verification.
 		 */
-		cqr->lpm = LPM_ANYPATH;
-		DBF_DEV_EVENT(DBF_DEBUG, device, "%s",
-			      "start_IO: selected pathes gone,"
-			      " retry on all pathes");
+		if (test_bit(DASD_CQR_VERIFY_PATH, &cqr->flags)) {
+			DBF_DEV_EVENT(DBF_WARNING, device,
+				      "start_IO: selected paths gone (%x)",
+				      cqr->lpm);
+		} else if (cqr->lpm != device->path_data.opm) {
+			cqr->lpm = device->path_data.opm;
+			DBF_DEV_EVENT(DBF_DEBUG, device, "%s",
+				      "start_IO: selected paths gone,"
+				      " retry on all paths");
+		} else {
+			DBF_DEV_EVENT(DBF_WARNING, device, "%s",
+				      "start_IO: all paths in opm gone,"
+				      " do path verification");
+			dasd_generic_last_path_gone(device);
+			device->path_data.opm = 0;
+			device->path_data.ppm = 0;
+			device->path_data.npm = 0;
+			device->path_data.tbvpm =
+				ccw_device_get_path_mask(device->cdev);
+		}
 		break;
 	case -ENODEV:
-		DBF_DEV_EVENT(DBF_DEBUG, device, "%s",
+		DBF_DEV_EVENT(DBF_WARNING, device, "%s",
 			      "start_IO: -ENODEV device gone, retry");
 		break;
 	case -EIO:
-		DBF_DEV_EVENT(DBF_DEBUG, device, "%s",
+		DBF_DEV_EVENT(DBF_WARNING, device, "%s",
 			      "start_IO: -EIO device gone, retry");
 		break;
 	case -EINVAL:
 		/* most likely caused in power management context */
-		DBF_DEV_EVENT(DBF_DEBUG, device, "%s",
+		DBF_DEV_EVENT(DBF_WARNING, device, "%s",
 			      "start_IO: -EINVAL device currently "
 			      "not accessible");
 		break;
@@ -1175,12 +1198,13 @@ void dasd_int_handler(struct ccw_device *cdev, unsigned long intparm,
 		 */
 		if (!test_bit(DASD_CQR_FLAGS_USE_ERP, &cqr->flags) &&
 		    cqr->retries > 0) {
-			if (cqr->lpm == LPM_ANYPATH)
+			if (cqr->lpm == device->path_data.opm)
 				DBF_DEV_EVENT(DBF_DEBUG, device,
 					      "default ERP in fastpath "
 					      "(%i retries left)",
 					      cqr->retries);
-			cqr->lpm    = LPM_ANYPATH;
+			if (!test_bit(DASD_CQR_VERIFY_PATH, &cqr->flags))
+				cqr->lpm = device->path_data.opm;
 			cqr->status = DASD_CQR_QUEUED;
 			next = cqr;
 		} else
@@ -1364,8 +1388,14 @@ static void __dasd_device_start_head(struct dasd_device *device)
 	cqr = list_entry(device->ccw_queue.next, struct dasd_ccw_req, devlist);
 	if (cqr->status != DASD_CQR_QUEUED)
 		return;
-	/* when device is stopped, return request to previous layer */
-	if (device->stopped) {
+	/* when device is stopped, return request to previous layer
+	 * exception: only the disconnect or unresumed bits are set and the
+	 * cqr is a path verification request
+	 */
+	if (device->stopped &&
+	    !(!(device->stopped & ~(DASD_STOPPED_DC_WAIT | DASD_UNRESUMED_PM))
+	      && test_bit(DASD_CQR_VERIFY_PATH, &cqr->flags))) {
+		cqr->intrc = -EAGAIN;
 		cqr->status = DASD_CQR_CLEARED;
 		dasd_schedule_device_bh(device);
 		return;
@@ -1381,6 +1411,23 @@ static void __dasd_device_start_head(struct dasd_device *device)
 		dasd_device_set_timer(device, 50);
 }
 
+static void __dasd_device_check_path_events(struct dasd_device *device)
+{
+	int rc;
+
+	if (device->path_data.tbvpm) {
+		if (device->stopped & ~(DASD_STOPPED_DC_WAIT |
+					DASD_UNRESUMED_PM))
+			return;
+		rc = device->discipline->verify_path(
+			device, device->path_data.tbvpm);
+		if (rc)
+			dasd_device_set_timer(device, 50);
+		else
+			device->path_data.tbvpm = 0;
+	}
+};
+
 /*
  * Go through all request on the dasd_device request queue,
  * terminate them on the cdev if necessary, and return them to the
@@ -1455,6 +1502,7 @@ static void dasd_device_tasklet(struct dasd_device *device)
 	__dasd_device_check_expire(device);
 	/* find final requests on ccw queue */
 	__dasd_device_process_ccw_queue(device, &final_queue);
+	__dasd_device_check_path_events(device);
 	spin_unlock_irq(get_ccwdev_lock(device->cdev));
 	/* Now call the callback function of requests with final status */
 	__dasd_device_process_final_queue(device, &final_queue);
@@ -2586,10 +2634,53 @@ int dasd_generic_set_offline(struct ccw_device *cdev)
 	return 0;
 }
 
+int dasd_generic_last_path_gone(struct dasd_device *device)
+{
+	struct dasd_ccw_req *cqr;
+
+	dev_warn(&device->cdev->dev, "No operational channel path is left "
+		 "for the device\n");
+	DBF_DEV_EVENT(DBF_WARNING, device, "%s", "last path gone");
+	/* First of all call extended error reporting. */
+	dasd_eer_write(device, NULL, DASD_EER_NOPATH);
+
+	if (device->state < DASD_STATE_BASIC)
+		return 0;
+	/* Device is active. We want to keep it. */
+	list_for_each_entry(cqr, &device->ccw_queue, devlist)
+		if ((cqr->status == DASD_CQR_IN_IO) ||
+		    (cqr->status == DASD_CQR_CLEAR_PENDING)) {
+			cqr->status = DASD_CQR_QUEUED;
+			cqr->retries++;
+		}
+	dasd_device_set_stop_bits(device, DASD_STOPPED_DC_WAIT);
+	dasd_device_clear_timer(device);
+	dasd_schedule_device_bh(device);
+	return 1;
+}
+EXPORT_SYMBOL_GPL(dasd_generic_last_path_gone);
+
+int dasd_generic_path_operational(struct dasd_device *device)
+{
+	dev_info(&device->cdev->dev, "A channel path to the device has become "
+		 "operational\n");
+	DBF_DEV_EVENT(DBF_WARNING, device, "%s", "path operational");
+	dasd_device_remove_stop_bits(device, DASD_STOPPED_DC_WAIT);
+	if (device->stopped & DASD_UNRESUMED_PM) {
+		dasd_device_remove_stop_bits(device, DASD_UNRESUMED_PM);
+		dasd_restore_device(device);
+		return 1;
+	}
+	dasd_schedule_device_bh(device);
+	if (device->block)
+		dasd_schedule_block_bh(device->block);
+	return 1;
+}
+EXPORT_SYMBOL_GPL(dasd_generic_path_operational);
+
 int dasd_generic_notify(struct ccw_device *cdev, int event)
 {
 	struct dasd_device *device;
-	struct dasd_ccw_req *cqr;
 	int ret;
 
 	device = dasd_device_from_cdev_locked(cdev);
@@ -2600,41 +2691,64 @@ int dasd_generic_notify(struct ccw_device *cdev, int event)
 	case CIO_GONE:
 	case CIO_BOXED:
 	case CIO_NO_PATH:
-		/* First of all call extended error reporting. */
-		dasd_eer_write(device, NULL, DASD_EER_NOPATH);
-
-		if (device->state < DASD_STATE_BASIC)
-			break;
-		/* Device is active. We want to keep it. */
-		list_for_each_entry(cqr, &device->ccw_queue, devlist)
-			if (cqr->status == DASD_CQR_IN_IO) {
-				cqr->status = DASD_CQR_QUEUED;
-				cqr->retries++;
-			}
-		dasd_device_set_stop_bits(device, DASD_STOPPED_DC_WAIT);
-		dasd_device_clear_timer(device);
-		dasd_schedule_device_bh(device);
-		ret = 1;
+		device->path_data.opm = 0;
+		device->path_data.ppm = 0;
+		device->path_data.npm = 0;
+		ret = dasd_generic_last_path_gone(device);
 		break;
 	case CIO_OPER:
-		/* FIXME: add a sanity check. */
-		dasd_device_remove_stop_bits(device, DASD_STOPPED_DC_WAIT);
-		if (device->stopped & DASD_UNRESUMED_PM) {
-			dasd_device_remove_stop_bits(device, DASD_UNRESUMED_PM);
-			dasd_restore_device(device);
-			ret = 1;
-			break;
-		}
-		dasd_schedule_device_bh(device);
-		if (device->block)
-			dasd_schedule_block_bh(device->block);
 		ret = 1;
+		if (device->path_data.opm)
+			ret = dasd_generic_path_operational(device);
 		break;
 	}
 	dasd_put_device(device);
 	return ret;
 }
 
+void dasd_generic_path_event(struct ccw_device *cdev, int *path_event)
+{
+	int chp;
+	__u8 oldopm, eventlpm;
+	struct dasd_device *device;
+
+	device = dasd_device_from_cdev_locked(cdev);
+	if (IS_ERR(device))
+		return;
+	for (chp = 0; chp < 8; chp++) {
+		eventlpm = 0x80 >> chp;
+		if (path_event[chp] & PE_PATH_GONE) {
+			oldopm = device->path_data.opm;
+			device->path_data.opm &= ~eventlpm;
+			device->path_data.ppm &= ~eventlpm;
+			device->path_data.npm &= ~eventlpm;
+			if (oldopm && !device->path_data.opm)
+				dasd_generic_last_path_gone(device);
+		}
+		if (path_event[chp] & PE_PATH_AVAILABLE) {
+			device->path_data.opm &= ~eventlpm;
+			device->path_data.ppm &= ~eventlpm;
+			device->path_data.npm &= ~eventlpm;
+			device->path_data.tbvpm |= eventlpm;
+			dasd_schedule_device_bh(device);
+		}
+	}
+	dasd_put_device(device);
+}
+EXPORT_SYMBOL_GPL(dasd_generic_path_event);
+
+int dasd_generic_verify_path(struct dasd_device *device, __u8 lpm)
+{
+	if (!device->path_data.opm && lpm) {
+		device->path_data.opm = lpm;
+		dasd_generic_path_operational(device);
+	} else
+		device->path_data.opm |= lpm;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(dasd_generic_verify_path);
+
+
 int dasd_generic_pm_freeze(struct ccw_device *cdev)
 {
 	struct dasd_ccw_req *cqr, *n;
diff --git a/drivers/s390/block/dasd_3990_erp.c b/drivers/s390/block/dasd_3990_erp.c
index 968c76c..1654a24 100644
--- a/drivers/s390/block/dasd_3990_erp.c
+++ b/drivers/s390/block/dasd_3990_erp.c
@@ -152,9 +152,9 @@ dasd_3990_erp_alternate_path(struct dasd_ccw_req * erp)
 	spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
 	opm = ccw_device_get_path_mask(device->cdev);
 	spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
-	//FIXME: start with get_opm ?
 	if (erp->lpm == 0)
-		erp->lpm = LPM_ANYPATH & ~(erp->irb.esw.esw0.sublog.lpum);
+		erp->lpm = device->path_data.opm &
+			~(erp->irb.esw.esw0.sublog.lpum);
 	else
 		erp->lpm &= ~(erp->irb.esw.esw0.sublog.lpum);
 
@@ -270,10 +270,11 @@ static struct dasd_ccw_req *dasd_3990_erp_action_1(struct dasd_ccw_req *erp)
 {
 	erp->function = dasd_3990_erp_action_1;
 	dasd_3990_erp_alternate_path(erp);
-	if (erp->status == DASD_CQR_FAILED) {
+	if (erp->status == DASD_CQR_FAILED &&
+	    !test_bit(DASD_CQR_VERIFY_PATH, &erp->flags)) {
 		erp->status = DASD_CQR_FILLED;
 		erp->retries = 10;
-		erp->lpm = LPM_ANYPATH;
+		erp->lpm = erp->startdev->path_data.opm;
 		erp->function = dasd_3990_erp_action_1_sec;
 	}
 	return erp;
@@ -1907,15 +1908,14 @@ dasd_3990_erp_compound_retry(struct dasd_ccw_req * erp, char *sense)
 static void
 dasd_3990_erp_compound_path(struct dasd_ccw_req * erp, char *sense)
 {
-
 	if (sense[25] & DASD_SENSE_BIT_3) {
 		dasd_3990_erp_alternate_path(erp);
 
-		if (erp->status == DASD_CQR_FAILED) {
+		if (erp->status == DASD_CQR_FAILED &&
+		    !test_bit(DASD_CQR_VERIFY_PATH, &erp->flags)) {
 			/* reset the lpm and the status to be able to
 			 * try further actions. */
-
-			erp->lpm = 0;
+			erp->lpm = erp->startdev->path_data.opm;
 			erp->status = DASD_CQR_NEED_ERP;
 		}
 	}
diff --git a/drivers/s390/block/dasd_devmap.c b/drivers/s390/block/dasd_devmap.c
index 8d41f3e..0001df8 100644
--- a/drivers/s390/block/dasd_devmap.c
+++ b/drivers/s390/block/dasd_devmap.c
@@ -639,6 +639,7 @@ dasd_put_device_wake(struct dasd_device *device)
 {
 	wake_up(&dasd_delete_wq);
 }
+EXPORT_SYMBOL_GPL(dasd_put_device_wake);
 
 /*
  * Return dasd_device structure associated with cdev.
diff --git a/drivers/s390/block/dasd_diag.c b/drivers/s390/block/dasd_diag.c
index a3a5db5..29143ed 100644
--- a/drivers/s390/block/dasd_diag.c
+++ b/drivers/s390/block/dasd_diag.c
@@ -619,6 +619,7 @@ static struct dasd_discipline dasd_diag_discipline = {
 	.ebcname = "DIAG",
 	.max_blocks = DIAG_MAX_BLOCKS,
 	.check_device = dasd_diag_check_device,
+	.verify_path = dasd_generic_verify_path,
 	.fill_geometry = dasd_diag_fill_geometry,
 	.start_IO = dasd_start_diag,
 	.term_IO = dasd_diag_term_IO,
diff --git a/drivers/s390/block/dasd_eckd.c b/drivers/s390/block/dasd_eckd.c
index 549443a..a1ebf57 100644
--- a/drivers/s390/block/dasd_eckd.c
+++ b/drivers/s390/block/dasd_eckd.c
@@ -90,6 +90,18 @@ static struct {
 } *dasd_reserve_req;
 static DEFINE_MUTEX(dasd_reserve_mutex);
 
+/* definitions for the path verification worker */
+struct path_verification_work_data {
+	struct work_struct worker;
+	struct dasd_device *device;
+	struct dasd_ccw_req cqr;
+	struct ccw1 ccw;
+	__u8 rcd_buffer[DASD_ECKD_RCD_DATA_SIZE];
+	int isglobal;
+	__u8 tbvpm;
+};
+static struct path_verification_work_data *path_verification_worker;
+static DEFINE_MUTEX(dasd_path_verification_mutex);
 
 /* initial attempt at a probe function. this can be simplified once
  * the other detection code is gone */
@@ -755,26 +767,27 @@ static int dasd_eckd_get_uid(struct dasd_device *device, struct dasd_uid *uid)
 	return -EINVAL;
 }
 
-static struct dasd_ccw_req *dasd_eckd_build_rcd_lpm(struct dasd_device *device,
-						    void *rcd_buffer,
-						    struct ciw *ciw, __u8 lpm)
+static void dasd_eckd_fill_rcd_cqr(struct dasd_device *device,
+				   struct dasd_ccw_req *cqr,
+				   __u8 *rcd_buffer,
+				   __u8 lpm)
 {
-	struct dasd_ccw_req *cqr;
 	struct ccw1 *ccw;
-
-	cqr = dasd_smalloc_request(DASD_ECKD_MAGIC, 1 /* RCD */, ciw->count,
-				   device);
-
-	if (IS_ERR(cqr)) {
-		DBF_DEV_EVENT(DBF_WARNING, device, "%s",
-			      "Could not allocate RCD request");
-		return cqr;
-	}
+	/*
+	 * buffer has to start with EBCDIC "V1.0" to show
+	 * support for virtual device SNEQ
+	 */
+	rcd_buffer[0] = 0xE5;
+	rcd_buffer[1] = 0xF1;
+	rcd_buffer[2] = 0x4B;
+	rcd_buffer[3] = 0xF0;
 
 	ccw = cqr->cpaddr;
-	ccw->cmd_code = ciw->cmd;
+	ccw->cmd_code = DASD_ECKD_CCW_RCD;
+	ccw->flags = 0;
 	ccw->cda = (__u32)(addr_t)rcd_buffer;
-	ccw->count = ciw->count;
+	ccw->count = DASD_ECKD_RCD_DATA_SIZE;
+	cqr->magic = DASD_ECKD_MAGIC;
 
 	cqr->startdev = device;
 	cqr->memdev = device;
@@ -784,7 +797,29 @@ static struct dasd_ccw_req *dasd_eckd_build_rcd_lpm(struct dasd_device *device,
 	cqr->retries = 256;
 	cqr->buildclk = get_clock();
 	cqr->status = DASD_CQR_FILLED;
-	return cqr;
+	set_bit(DASD_CQR_VERIFY_PATH, &cqr->flags);
+}
+
+static int dasd_eckd_read_conf_immediately(struct dasd_device *device,
+					   struct dasd_ccw_req *cqr,
+					   __u8 *rcd_buffer,
+					   __u8 lpm)
+{
+	struct ciw *ciw;
+	int rc;
+	/*
+	 * sanity check: scan for RCD command in extended SenseID data
+	 * some devices do not support RCD
+	 */
+	ciw = ccw_device_get_ciw(device->cdev, CIW_TYPE_RCD);
+	if (!ciw || ciw->cmd != DASD_ECKD_CCW_RCD)
+		return -EOPNOTSUPP;
+
+	dasd_eckd_fill_rcd_cqr(device, cqr, rcd_buffer, lpm);
+	clear_bit(DASD_CQR_FLAGS_USE_ERP, &cqr->flags);
+	cqr->retries = 5;
+	rc = dasd_sleep_on_immediatly(cqr);
+	return rc;
 }
 
 static int dasd_eckd_read_conf_lpm(struct dasd_device *device,
@@ -797,32 +832,29 @@ static int dasd_eckd_read_conf_lpm(struct dasd_device *device,
 	struct dasd_ccw_req *cqr;
 
 	/*
-	 * scan for RCD command in extended SenseID data
+	 * sanity check: scan for RCD command in extended SenseID data
+	 * some devices do not support RCD
 	 */
 	ciw = ccw_device_get_ciw(device->cdev, CIW_TYPE_RCD);
-	if (!ciw || ciw->cmd == 0) {
+	if (!ciw || ciw->cmd != DASD_ECKD_CCW_RCD) {
 		ret = -EOPNOTSUPP;
 		goto out_error;
 	}
-	rcd_buf = kzalloc(ciw->count, GFP_KERNEL | GFP_DMA);
+	rcd_buf = kzalloc(DASD_ECKD_RCD_DATA_SIZE, GFP_KERNEL | GFP_DMA);
 	if (!rcd_buf) {
 		ret = -ENOMEM;
 		goto out_error;
 	}
-
-	/*
-	 * buffer has to start with EBCDIC "V1.0" to show
-	 * support for virtual device SNEQ
-	 */
-	rcd_buf[0] = 0xE5;
-	rcd_buf[1] = 0xF1;
-	rcd_buf[2] = 0x4B;
-	rcd_buf[3] = 0xF0;
-	cqr = dasd_eckd_build_rcd_lpm(device, rcd_buf, ciw, lpm);
+	cqr = dasd_smalloc_request(DASD_ECKD_MAGIC, 1 /* RCD */,
+				   0, /* use rcd_buf as data ara */
+				   device);
 	if (IS_ERR(cqr)) {
-		ret =  PTR_ERR(cqr);
+		DBF_DEV_EVENT(DBF_WARNING, device, "%s",
+			      "Could not allocate RCD request");
+		ret = -ENOMEM;
 		goto out_error;
 	}
+	dasd_eckd_fill_rcd_cqr(device, cqr, rcd_buf, lpm);
 	ret = dasd_sleep_on(cqr);
 	/*
 	 * on success we update the user input parms
@@ -831,7 +863,7 @@ static int dasd_eckd_read_conf_lpm(struct dasd_device *device,
 	if (ret)
 		goto out_error;
 
-	*rcd_buffer_size = ciw->count;
+	*rcd_buffer_size = DASD_ECKD_RCD_DATA_SIZE;
 	*rcd_buffer = rcd_buf;
 	return 0;
 out_error:
@@ -901,18 +933,18 @@ static int dasd_eckd_read_conf(struct dasd_device *device)
 	void *conf_data;
 	int conf_len, conf_data_saved;
 	int rc;
-	__u8 lpm;
+	__u8 lpm, opm;
 	struct dasd_eckd_private *private;
-	struct dasd_eckd_path *path_data;
+	struct dasd_path *path_data;
 
 	private = (struct dasd_eckd_private *) device->private;
-	path_data = (struct dasd_eckd_path *) &private->path_data;
-	path_data->opm = ccw_device_get_path_mask(device->cdev);
+	path_data = &device->path_data;
+	opm = ccw_device_get_path_mask(device->cdev);
 	lpm = 0x80;
 	conf_data_saved = 0;
 	/* get configuration data per operational path */
 	for (lpm = 0x80; lpm; lpm>>= 1) {
-		if (lpm & path_data->opm){
+		if (lpm & opm) {
 			rc = dasd_eckd_read_conf_lpm(device, &conf_data,
 						     &conf_len, lpm);
 			if (rc && rc != -EOPNOTSUPP) {	/* -EOPNOTSUPP is ok */
@@ -925,6 +957,8 @@ static int dasd_eckd_read_conf(struct dasd_device *device)
 				DBF_EVENT_DEVID(DBF_WARNING, device->cdev, "%s",
 						"No configuration data "
 						"retrieved");
+				/* no further analysis possible */
+				path_data->opm |= lpm;
 				continue;	/* no error */
 			}
 			/* save first valid configuration data */
@@ -948,6 +982,7 @@ static int dasd_eckd_read_conf(struct dasd_device *device)
 				path_data->ppm |= lpm;
 				break;
 			}
+			path_data->opm |= lpm;
 			if (conf_data != private->conf_data)
 				kfree(conf_data);
 		}
@@ -955,6 +990,140 @@ static int dasd_eckd_read_conf(struct dasd_device *device)
 	return 0;
 }
 
+static int verify_fcx_max_data(struct dasd_device *device, __u8 lpm)
+{
+	struct dasd_eckd_private *private;
+	int mdc;
+	u32 fcx_max_data;
+
+	private = (struct dasd_eckd_private *) device->private;
+	if (private->fcx_max_data) {
+		mdc = ccw_device_get_mdc(device->cdev, lpm);
+		if ((mdc < 0)) {
+			dev_warn(&device->cdev->dev,
+				 "Detecting the maximum data size for zHPF "
+				 "requests failed (rc=%d) for a new path %x\n",
+				 mdc, lpm);
+			return mdc;
+		}
+		fcx_max_data = mdc * FCX_MAX_DATA_FACTOR;
+		if (fcx_max_data < private->fcx_max_data) {
+			dev_warn(&device->cdev->dev,
+				 "The maximum data size for zHPF requests %u "
+				 "on a new path %x is below the active maximum "
+				 "%u\n", fcx_max_data, lpm,
+				 private->fcx_max_data);
+			return -EACCES;
+		}
+	}
+	return 0;
+}
+
+static void do_path_verification_work(struct work_struct *work)
+{
+	struct path_verification_work_data *data;
+	struct dasd_device *device;
+	__u8 lpm, opm, npm, ppm, epm;
+	unsigned long flags;
+	int rc;
+
+	data = container_of(work, struct path_verification_work_data, worker);
+	device = data->device;
+
+	opm = 0;
+	npm = 0;
+	ppm = 0;
+	epm = 0;
+	for (lpm = 0x80; lpm; lpm >>= 1) {
+		if (lpm & data->tbvpm) {
+			memset(data->rcd_buffer, 0, sizeof(data->rcd_buffer));
+			memset(&data->cqr, 0, sizeof(data->cqr));
+			data->cqr.cpaddr = &data->ccw;
+			rc = dasd_eckd_read_conf_immediately(device, &data->cqr,
+							     data->rcd_buffer,
+							     lpm);
+			if (!rc) {
+				switch (dasd_eckd_path_access(data->rcd_buffer,
+						     DASD_ECKD_RCD_DATA_SIZE)) {
+				case 0x02:
+					npm |= lpm;
+					break;
+				case 0x03:
+					ppm |= lpm;
+					break;
+				}
+				opm |= lpm;
+			} else if (rc == -EOPNOTSUPP) {
+				DBF_EVENT_DEVID(DBF_WARNING, device->cdev, "%s",
+				       "path verification: No configuration "
+				       "data retrieved");
+				opm |= lpm;
+			} else if (rc == -EAGAIN) {
+				DBF_EVENT_DEVID(DBF_WARNING, device->cdev, "%s",
+					"path verification: device is stopped,"
+					" try again later");
+				epm |= lpm;
+			} else {
+				dev_warn(&device->cdev->dev,
+					 "Reading device feature codes failed "
+					 "(rc=%d) for new path %x\n", rc, lpm);
+				continue;
+			}
+			if (verify_fcx_max_data(device, lpm)) {
+				opm &= ~lpm;
+				npm &= ~lpm;
+				ppm &= ~lpm;
+			}
+		}
+	}
+	/*
+	 * There is a small chance that a path is lost again between
+	 * above path verification and the following modification of
+	 * the device opm mask. We could avoid that race here by using
+	 * yet another path mask, but we rather deal with this unlikely
+	 * situation in dasd_start_IO.
+	 */
+	spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
+	if (!device->path_data.opm && opm) {
+		device->path_data.opm = opm;
+		dasd_generic_path_operational(device);
+	} else
+		device->path_data.opm |= opm;
+	device->path_data.npm |= npm;
+	device->path_data.ppm |= ppm;
+	device->path_data.tbvpm |= epm;
+	spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
+
+	dasd_put_device(device);
+	if (data->isglobal)
+		mutex_unlock(&dasd_path_verification_mutex);
+	else
+		kfree(data);
+}
+
+static int dasd_eckd_verify_path(struct dasd_device *device, __u8 lpm)
+{
+	struct path_verification_work_data *data;
+
+	data = kmalloc(sizeof(*data), GFP_ATOMIC | GFP_DMA);
+	if (!data) {
+		if (mutex_trylock(&dasd_path_verification_mutex)) {
+			data = path_verification_worker;
+			data->isglobal = 1;
+		} else
+			return -ENOMEM;
+	} else {
+		memset(data, 0, sizeof(*data));
+		data->isglobal = 0;
+	}
+	INIT_WORK(&data->worker, do_path_verification_work);
+	dasd_get_device(device);
+	data->device = device;
+	data->tbvpm = lpm;
+	schedule_work(&data->worker);
+	return 0;
+}
+
 static int dasd_eckd_read_features(struct dasd_device *device)
 {
 	struct dasd_psf_prssd_data *prssdp;
@@ -1749,6 +1918,7 @@ static void dasd_eckd_handle_terminated_request(struct dasd_ccw_req *cqr)
 	if (cqr->block && (cqr->startdev != cqr->block->base)) {
 		dasd_eckd_reset_ccw_to_base_io(cqr);
 		cqr->startdev = cqr->block->base;
+		cqr->lpm = cqr->block->base->path_data.opm;
 	}
 };
 
@@ -2017,7 +2187,7 @@ static struct dasd_ccw_req *dasd_eckd_build_cp_cmd_single(
 	cqr->memdev = startdev;
 	cqr->block = block;
 	cqr->expires = startdev->default_expires * HZ;	/* default 5 minutes */
-	cqr->lpm = private->path_data.ppm;
+	cqr->lpm = startdev->path_data.ppm;
 	cqr->retries = 256;
 	cqr->buildclk = get_clock();
 	cqr->status = DASD_CQR_FILLED;
@@ -2194,7 +2364,7 @@ static struct dasd_ccw_req *dasd_eckd_build_cp_cmd_track(
 	cqr->memdev = startdev;
 	cqr->block = block;
 	cqr->expires = startdev->default_expires * HZ;	/* default 5 minutes */
-	cqr->lpm = private->path_data.ppm;
+	cqr->lpm = startdev->path_data.ppm;
 	cqr->retries = 256;
 	cqr->buildclk = get_clock();
 	cqr->status = DASD_CQR_FILLED;
@@ -2484,7 +2654,7 @@ static struct dasd_ccw_req *dasd_eckd_build_cp_tpm_track(
 	cqr->memdev = startdev;
 	cqr->block = block;
 	cqr->expires = startdev->default_expires * HZ;	/* default 5 minutes */
-	cqr->lpm = private->path_data.ppm;
+	cqr->lpm = startdev->path_data.ppm;
 	cqr->retries = 256;
 	cqr->buildclk = get_clock();
 	cqr->status = DASD_CQR_FILLED;
@@ -3624,6 +3794,7 @@ static struct ccw_driver dasd_eckd_driver = {
 	.set_offline = dasd_generic_set_offline,
 	.set_online  = dasd_eckd_set_online,
 	.notify      = dasd_generic_notify,
+	.path_event  = dasd_generic_path_event,
 	.freeze      = dasd_generic_pm_freeze,
 	.thaw	     = dasd_generic_restore_device,
 	.restore     = dasd_generic_restore_device,
@@ -3651,6 +3822,7 @@ static struct dasd_discipline dasd_eckd_discipline = {
 	.check_device = dasd_eckd_check_characteristics,
 	.uncheck_device = dasd_eckd_uncheck_device,
 	.do_analysis = dasd_eckd_do_analysis,
+	.verify_path = dasd_eckd_verify_path,
 	.ready_to_online = dasd_eckd_ready_to_online,
 	.online_to_ready = dasd_eckd_online_to_ready,
 	.fill_geometry = dasd_eckd_fill_geometry,
@@ -3683,11 +3855,19 @@ dasd_eckd_init(void)
 				   GFP_KERNEL | GFP_DMA);
 	if (!dasd_reserve_req)
 		return -ENOMEM;
+	path_verification_worker = kmalloc(sizeof(*path_verification_worker),
+				   GFP_KERNEL | GFP_DMA);
+	if (!path_verification_worker) {
+		kfree(dasd_reserve_req);
+		return -ENOMEM;
+	}
 	ret = ccw_driver_register(&dasd_eckd_driver);
 	if (!ret)
 		wait_for_device_probe();
-	else
+	else {
+		kfree(path_verification_worker);
 		kfree(dasd_reserve_req);
+	}
 	return ret;
 }
 
@@ -3695,6 +3875,7 @@ static void __exit
 dasd_eckd_cleanup(void)
 {
 	ccw_driver_unregister(&dasd_eckd_driver);
+	kfree(path_verification_worker);
 	kfree(dasd_reserve_req);
 }
 
diff --git a/drivers/s390/block/dasd_eckd.h b/drivers/s390/block/dasd_eckd.h
index 2150aed..5051f37 100644
--- a/drivers/s390/block/dasd_eckd.h
+++ b/drivers/s390/block/dasd_eckd.h
@@ -45,6 +45,7 @@
 #define DASD_ECKD_CCW_PFX		 0xE7
 #define DASD_ECKD_CCW_PFX_READ		 0xEA
 #define DASD_ECKD_CCW_RSCK		 0xF9
+#define DASD_ECKD_CCW_RCD		 0xFA
 
 /*
  * Perform Subsystem Function / Sub-Orders
@@ -59,6 +60,7 @@
 
 
 #define FCX_MAX_DATA_FACTOR 65536
+#define DASD_ECKD_RCD_DATA_SIZE 256
 
 
 /*****************************************************************************
@@ -335,12 +337,6 @@ struct dasd_gneq {
 	__u8 reserved2[22];
 } __attribute__ ((packed));
 
-struct dasd_eckd_path {
-	__u8 opm;
-	__u8 ppm;
-	__u8 npm;
-};
-
 struct dasd_rssd_features {
 	char feature[256];
 } __attribute__((packed));
@@ -446,7 +442,6 @@ struct dasd_eckd_private {
 	struct vd_sneq *vdsneq;
 	struct dasd_gneq *gneq;
 
-	struct dasd_eckd_path path_data;
 	struct eckd_count count_area[5];
 	int init_cqr_status;
 	int uses_cdl;
diff --git a/drivers/s390/block/dasd_erp.c b/drivers/s390/block/dasd_erp.c
index 7656384..0eafe2e 100644
--- a/drivers/s390/block/dasd_erp.c
+++ b/drivers/s390/block/dasd_erp.c
@@ -96,7 +96,8 @@ dasd_default_erp_action(struct dasd_ccw_req *cqr)
 		DBF_DEV_EVENT(DBF_DEBUG, device,
                              "default ERP called (%i retries left)",
                              cqr->retries);
-		cqr->lpm    = LPM_ANYPATH;
+		if (!test_bit(DASD_CQR_VERIFY_PATH, &cqr->flags))
+			cqr->lpm = device->path_data.opm;
 		cqr->status = DASD_CQR_FILLED;
         } else {
 		pr_err("%s: default ERP has run out of retries and failed\n",
diff --git a/drivers/s390/block/dasd_fba.c b/drivers/s390/block/dasd_fba.c
index bec5486e..86bacda 100644
--- a/drivers/s390/block/dasd_fba.c
+++ b/drivers/s390/block/dasd_fba.c
@@ -73,6 +73,7 @@ static struct ccw_driver dasd_fba_driver = {
 	.set_offline = dasd_generic_set_offline,
 	.set_online  = dasd_fba_set_online,
 	.notify      = dasd_generic_notify,
+	.path_event  = dasd_generic_path_event,
 	.freeze      = dasd_generic_pm_freeze,
 	.thaw	     = dasd_generic_restore_device,
 	.restore     = dasd_generic_restore_device,
@@ -164,6 +165,7 @@ dasd_fba_check_characteristics(struct dasd_device *device)
 	}
 
 	device->default_expires = DASD_EXPIRES;
+	device->path_data.opm = LPM_ANYPATH;
 
 	readonly = dasd_device_is_ro(device);
 	if (readonly)
@@ -596,6 +598,7 @@ static struct dasd_discipline dasd_fba_discipline = {
 	.max_blocks = 96,
 	.check_device = dasd_fba_check_characteristics,
 	.do_analysis = dasd_fba_do_analysis,
+	.verify_path = dasd_generic_verify_path,
 	.fill_geometry = dasd_fba_fill_geometry,
 	.start_IO = dasd_start_IO,
 	.term_IO = dasd_term_IO,
diff --git a/drivers/s390/block/dasd_int.h b/drivers/s390/block/dasd_int.h
index 500678d..ba038ef 100644
--- a/drivers/s390/block/dasd_int.h
+++ b/drivers/s390/block/dasd_int.h
@@ -231,6 +231,7 @@ struct dasd_ccw_req {
 /* per dasd_ccw_req flags */
 #define DASD_CQR_FLAGS_USE_ERP   0	/* use ERP for this request */
 #define DASD_CQR_FLAGS_FAILFAST  1	/* FAILFAST */
+#define DASD_CQR_VERIFY_PATH	 2	/* path verification request */
 
 /* Signature for error recovery functions. */
 typedef struct dasd_ccw_req *(*dasd_erp_fn_t) (struct dasd_ccw_req *);
@@ -287,6 +288,14 @@ struct dasd_discipline {
 	int (*do_analysis) (struct dasd_block *);
 
 	/*
+	 * This function is called, when new paths become available.
+	 * Disciplins may use this callback to do necessary setup work,
+	 * e.g. verify that new path is compatible with the current
+	 * configuration.
+	 */
+	int (*verify_path)(struct dasd_device *, __u8);
+
+	/*
 	 * Last things to do when a device is set online, and first things
 	 * when it is set offline.
 	 */
@@ -362,6 +371,13 @@ extern struct dasd_discipline *dasd_diag_discipline_pointer;
 #define DASD_EER_STATECHANGE 3
 #define DASD_EER_PPRCSUSPEND 4
 
+struct dasd_path {
+	__u8 opm;
+	__u8 tbvpm;
+	__u8 ppm;
+	__u8 npm;
+};
+
 struct dasd_device {
 	/* Block device stuff. */
 	struct dasd_block *block;
@@ -377,6 +393,7 @@ struct dasd_device {
 	struct dasd_discipline *discipline;
 	struct dasd_discipline *base_discipline;
 	char *private;
+	struct dasd_path path_data;
 
 	/* Device state and target state. */
 	int state, target;
@@ -620,10 +637,15 @@ void dasd_generic_remove (struct ccw_device *cdev);
 int dasd_generic_set_online(struct ccw_device *, struct dasd_discipline *);
 int dasd_generic_set_offline (struct ccw_device *cdev);
 int dasd_generic_notify(struct ccw_device *, int);
+int dasd_generic_last_path_gone(struct dasd_device *);
+int dasd_generic_path_operational(struct dasd_device *);
+
 void dasd_generic_handle_state_change(struct dasd_device *);
 int dasd_generic_pm_freeze(struct ccw_device *);
 int dasd_generic_restore_device(struct ccw_device *);
 enum uc_todo dasd_generic_uc_handler(struct ccw_device *, struct irb *);
+void dasd_generic_path_event(struct ccw_device *, int *);
+int dasd_generic_verify_path(struct dasd_device *, __u8);
 
 int dasd_generic_read_dev_chars(struct dasd_device *, int, void *, int);
 char *dasd_get_sense(struct irb *);