[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 605f96f154a5..8f2067bc88c0 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 968c76cf7127..1654a24817be 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 8d41f3ed38d7..0001df8ad3e6 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 a3a5db58df18..29143eda9dd9 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 549443af121c..a1ebf5722ae5 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 2150aed541be..5051f374cbcb 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 7656384a811d..0eafe2e421e7 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 bec5486e0e6d..86bacda2c5f6 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 500678d7116c..ba038ef57606 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 *);