aboutsummaryrefslogblamecommitdiffstats
path: root/drivers/s390/block/dasd_alias.c
blob: 20676cdef4a519802b1d1a605d637f21ae64319b (plain) (tree)
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749




























































































                                                                               

                                                                             















































































































































































































































                                                                               
                                                                         




























































































































































































































































































































































































































                                                                                












                                                             









                                                                



                                                                    
                                                               



                                                                          




















































































































                                                                                
/*
 * PAV alias management for the DASD ECKD discipline
 *
 * Copyright IBM Corporation, 2007
 * Author(s): Stefan Weinhuber <wein@de.ibm.com>
 */

#include <linux/list.h>
#include <asm/ebcdic.h>
#include "dasd_int.h"
#include "dasd_eckd.h"

#ifdef PRINTK_HEADER
#undef PRINTK_HEADER
#endif				/* PRINTK_HEADER */
#define PRINTK_HEADER "dasd(eckd):"


/*
 * General concept of alias management:
 * - PAV and DASD alias management is specific to the eckd discipline.
 * - A device is connected to an lcu as long as the device exists.
 *   dasd_alias_make_device_known_to_lcu will be called wenn the
 *   device is checked by the eckd discipline and
 *   dasd_alias_disconnect_device_from_lcu will be called
 *   before the device is deleted.
 * - The dasd_alias_add_device / dasd_alias_remove_device
 *   functions mark the point when a device is 'ready for service'.
 * - A summary unit check is a rare occasion, but it is mandatory to
 *   support it. It requires some complex recovery actions before the
 *   devices can be used again (see dasd_alias_handle_summary_unit_check).
 * - dasd_alias_get_start_dev will find an alias device that can be used
 *   instead of the base device and does some (very simple) load balancing.
 *   This is the function that gets called for each I/O, so when improving
 *   something, this function should get faster or better, the rest has just
 *   to be correct.
 */


static void summary_unit_check_handling_work(struct work_struct *);
static void lcu_update_work(struct work_struct *);
static int _schedule_lcu_update(struct alias_lcu *, struct dasd_device *);

static struct alias_root aliastree = {
	.serverlist = LIST_HEAD_INIT(aliastree.serverlist),
	.lock = __SPIN_LOCK_UNLOCKED(aliastree.lock),
};

static struct alias_server *_find_server(struct dasd_uid *uid)
{
	struct alias_server *pos;
	list_for_each_entry(pos, &aliastree.serverlist, server) {
		if (!strncmp(pos->uid.vendor, uid->vendor,
			     sizeof(uid->vendor))
		    && !strncmp(pos->uid.serial, uid->serial,
				sizeof(uid->serial)))
			return pos;
	};
	return NULL;
}

static struct alias_lcu *_find_lcu(struct alias_server *server,
				   struct dasd_uid *uid)
{
	struct alias_lcu *pos;
	list_for_each_entry(pos, &server->lculist, lcu) {
		if (pos->uid.ssid == uid->ssid)
			return pos;
	};
	return NULL;
}

static struct alias_pav_group *_find_group(struct alias_lcu *lcu,
					   struct dasd_uid *uid)
{
	struct alias_pav_group *pos;
	__u8 search_unit_addr;

	/* for hyper pav there is only one group */
	if (lcu->pav == HYPER_PAV) {
		if (list_empty(&lcu->grouplist))
			return NULL;
		else
			return list_first_entry(&lcu->grouplist,
						struct alias_pav_group, group);
	}

	/* for base pav we have to find the group that matches the base */
	if (uid->type == UA_BASE_DEVICE)
		search_unit_addr = uid->real_unit_addr;
	else
		search_unit_addr = uid->base_unit_addr;
	list_for_each_entry(pos, &lcu->grouplist, group) {
		if (pos->uid.base_unit_addr == search_unit_addr &&
		    !strncmp(pos->uid.vduit, uid->vduit, sizeof(uid->vduit)))
			return pos;
	};
	return NULL;
}

static struct alias_server *_allocate_server(struct dasd_uid *uid)
{
	struct alias_server *server;

	server = kzalloc(sizeof(*server), GFP_KERNEL);
	if (!server)
		return ERR_PTR(-ENOMEM);
	memcpy(server->uid.vendor, uid->vendor, sizeof(uid->vendor));
	memcpy(server->uid.serial, uid->serial, sizeof(uid->serial));
	INIT_LIST_HEAD(&server->server);
	INIT_LIST_HEAD(&server->lculist);
	return server;
}

static void _free_server(struct alias_server *server)
{
	kfree(server);
}

static struct alias_lcu *_allocate_lcu(struct dasd_uid *uid)
{
	struct alias_lcu *lcu;

	lcu = kzalloc(sizeof(*lcu), GFP_KERNEL);
	if (!lcu)
		return ERR_PTR(-ENOMEM);
	lcu->uac = kzalloc(sizeof(*(lcu->uac)), GFP_KERNEL | GFP_DMA);
	if (!lcu->uac)
		goto out_err1;
	lcu->rsu_cqr = kzalloc(sizeof(*lcu->rsu_cqr), GFP_KERNEL | GFP_DMA);
	if (!lcu->rsu_cqr)
		goto out_err2;
	lcu->rsu_cqr->cpaddr = kzalloc(sizeof(struct ccw1),
				       GFP_KERNEL | GFP_DMA);
	if (!lcu->rsu_cqr->cpaddr)
		goto out_err3;
	lcu->rsu_cqr->data = kzalloc(16, GFP_KERNEL | GFP_DMA);
	if (!lcu->rsu_cqr->data)
		goto out_err4;

	memcpy(lcu->uid.vendor, uid->vendor, sizeof(uid->vendor));
	memcpy(lcu->uid.serial, uid->serial, sizeof(uid->serial));
	lcu->uid.ssid = uid->ssid;
	lcu->pav = NO_PAV;
	lcu->flags = NEED_UAC_UPDATE | UPDATE_PENDING;
	INIT_LIST_HEAD(&lcu->lcu);
	INIT_LIST_HEAD(&lcu->inactive_devices);
	INIT_LIST_HEAD(&lcu->active_devices);
	INIT_LIST_HEAD(&lcu->grouplist);
	INIT_WORK(&lcu->suc_data.worker, summary_unit_check_handling_work);
	INIT_DELAYED_WORK(&lcu->ruac_data.dwork, lcu_update_work);
	spin_lock_init(&lcu->lock);
	return lcu;

out_err4:
	kfree(lcu->rsu_cqr->cpaddr);
out_err3:
	kfree(lcu->rsu_cqr);
out_err2:
	kfree(lcu->uac);
out_err1:
	kfree(lcu);
	return ERR_PTR(-ENOMEM);
}

static void _free_lcu(struct alias_lcu *lcu)
{
	kfree(lcu->rsu_cqr->data);
	kfree(lcu->rsu_cqr->cpaddr);
	kfree(lcu->rsu_cqr);
	kfree(lcu->uac);
	kfree(lcu);
}

/*
 * This is the function that will allocate all the server and lcu data,
 * so this function must be called first for a new device.
 * If the return value is 1, the lcu was already known before, if it
 * is 0, this is a new lcu.
 * Negative return code indicates that something went wrong (e.g. -ENOMEM)
 */
int dasd_alias_make_device_known_to_lcu(struct dasd_device *device)
{
	struct dasd_eckd_private *private;
	unsigned long flags;
	struct alias_server *server, *newserver;
	struct alias_lcu *lcu, *newlcu;
	int is_lcu_known;
	struct dasd_uid *uid;

	private = (struct dasd_eckd_private *) device->private;
	uid = &private->uid;
	spin_lock_irqsave(&aliastree.lock, flags);
	is_lcu_known = 1;
	server = _find_server(uid);
	if (!server) {
		spin_unlock_irqrestore(&aliastree.lock, flags);
		newserver = _allocate_server(uid);
		if (IS_ERR(newserver))
			return PTR_ERR(newserver);
		spin_lock_irqsave(&aliastree.lock, flags);
		server = _find_server(uid);
		if (!server) {
			list_add(&newserver->server, &aliastree.serverlist);
			server = newserver;
			is_lcu_known = 0;
		} else {
			/* someone was faster */
			_free_server(newserver);
		}
	}

	lcu = _find_lcu(server, uid);
	if (!lcu) {
		spin_unlock_irqrestore(&aliastree.lock, flags);
		newlcu = _allocate_lcu(uid);
		if (IS_ERR(newlcu))
			return PTR_ERR(lcu);
		spin_lock_irqsave(&aliastree.lock, flags);
		lcu = _find_lcu(server, uid);
		if (!lcu) {
			list_add(&newlcu->lcu, &server->lculist);
			lcu = newlcu;
			is_lcu_known = 0;
		} else {
			/* someone was faster */
			_free_lcu(newlcu);
		}
		is_lcu_known = 0;
	}
	spin_lock(&lcu->lock);
	list_add(&device->alias_list, &lcu->inactive_devices);
	private->lcu = lcu;
	spin_unlock(&lcu->lock);
	spin_unlock_irqrestore(&aliastree.lock, flags);

	return is_lcu_known;
}

/*
 * This function removes a device from the scope of alias management.
 * The complicated part is to make sure that it is not in use by
 * any of the workers. If necessary cancel the work.
 */
void dasd_alias_disconnect_device_from_lcu(struct dasd_device *device)
{
	struct dasd_eckd_private *private;
	unsigned long flags;
	struct alias_lcu *lcu;
	struct alias_server *server;
	int was_pending;

	private = (struct dasd_eckd_private *) device->private;
	lcu = private->lcu;
	spin_lock_irqsave(&lcu->lock, flags);
	list_del_init(&device->alias_list);
	/* make sure that the workers don't use this device */
	if (device == lcu->suc_data.device) {
		spin_unlock_irqrestore(&lcu->lock, flags);
		cancel_work_sync(&lcu->suc_data.worker);
		spin_lock_irqsave(&lcu->lock, flags);
		if (device == lcu->suc_data.device)
			lcu->suc_data.device = NULL;
	}
	was_pending = 0;
	if (device == lcu->ruac_data.device) {
		spin_unlock_irqrestore(&lcu->lock, flags);
		was_pending = 1;
		cancel_delayed_work_sync(&lcu->ruac_data.dwork);
		spin_lock_irqsave(&lcu->lock, flags);
		if (device == lcu->ruac_data.device)
			lcu->ruac_data.device = NULL;
	}
	private->lcu = NULL;
	spin_unlock_irqrestore(&lcu->lock, flags);

	spin_lock_irqsave(&aliastree.lock, flags);
	spin_lock(&lcu->lock);
	if (list_empty(&lcu->grouplist) &&
	    list_empty(&lcu->active_devices) &&
	    list_empty(&lcu->inactive_devices)) {
		list_del(&lcu->lcu);
		spin_unlock(&lcu->lock);
		_free_lcu(lcu);
		lcu = NULL;
	} else {
		if (was_pending)
			_schedule_lcu_update(lcu, NULL);
		spin_unlock(&lcu->lock);
	}
	server = _find_server(&private->uid);
	if (server && list_empty(&server->lculist)) {
		list_del(&server->server);
		_free_server(server);
	}
	spin_unlock_irqrestore(&aliastree.lock, flags);
}

/*
 * This function assumes that the unit address configuration stored
 * in the lcu is up to date and will update the device uid before
 * adding it to a pav group.
 */
static int _add_device_to_lcu(struct alias_lcu *lcu,
			      struct dasd_device *device)
{

	struct dasd_eckd_private *private;
	struct alias_pav_group *group;
	struct dasd_uid *uid;

	private = (struct dasd_eckd_private *) device->private;
	uid = &private->uid;
	uid->type = lcu->uac->unit[uid->real_unit_addr].ua_type;
	uid->base_unit_addr = lcu->uac->unit[uid->real_unit_addr].base_ua;
	dasd_set_uid(device->cdev, &private->uid);

	/* if we have no PAV anyway, we don't need to bother with PAV groups */
	if (lcu->pav == NO_PAV) {
		list_move(&device->alias_list, &lcu->active_devices);
		return 0;
	}

	group = _find_group(lcu, uid);
	if (!group) {
		group = kzalloc(sizeof(*group), GFP_ATOMIC);
		if (!group)
			return -ENOMEM;
		memcpy(group->uid.vendor, uid->vendor, sizeof(uid->vendor));
		memcpy(group->uid.serial, uid->serial, sizeof(uid->serial));
		group->uid.ssid = uid->ssid;
		if (uid->type == UA_BASE_DEVICE)
			group->uid.base_unit_addr = uid->real_unit_addr;
		else
			group->uid.base_unit_addr = uid->base_unit_addr;
		memcpy(group->uid.vduit, uid->vduit, sizeof(uid->vduit));
		INIT_LIST_HEAD(&group->group);
		INIT_LIST_HEAD(&group->baselist);
		INIT_LIST_HEAD(&group->aliaslist);
		list_add(&group->group, &lcu->grouplist);
	}
	if (uid->type == UA_BASE_DEVICE)
		list_move(&device->alias_list, &group->baselist);
	else
		list_move(&device->alias_list, &group->aliaslist);
	private->pavgroup = group;
	return 0;
};

static void _remove_device_from_lcu(struct alias_lcu *lcu,
				    struct dasd_device *device)
{
	struct dasd_eckd_private *private;
	struct alias_pav_group *group;

	private = (struct dasd_eckd_private *) device->private;
	list_move(&device->alias_list, &lcu->inactive_devices);
	group = private->pavgroup;
	if (!group)
		return;
	private->pavgroup = NULL;
	if (list_empty(&group->baselist) && list_empty(&group->aliaslist)) {
		list_del(&group->group);
		kfree(group);
		return;
	}
	if (group->next == device)
		group->next = NULL;
};

static int read_unit_address_configuration(struct dasd_device *device,
					   struct alias_lcu *lcu)
{
	struct dasd_psf_prssd_data *prssdp;
	struct dasd_ccw_req *cqr;
	struct ccw1 *ccw;
	int rc;
	unsigned long flags;

	cqr = dasd_kmalloc_request("ECKD",
				   1 /* PSF */	+ 1 /* RSSD */ ,
				   (sizeof(struct dasd_psf_prssd_data)),
				   device);
	if (IS_ERR(cqr))
		return PTR_ERR(cqr);
	cqr->startdev = device;
	cqr->memdev = device;
	clear_bit(DASD_CQR_FLAGS_USE_ERP, &cqr->flags);
	cqr->retries = 10;
	cqr->expires = 20 * HZ;

	/* Prepare for Read Subsystem Data */
	prssdp = (struct dasd_psf_prssd_data *) cqr->data;
	memset(prssdp, 0, sizeof(struct dasd_psf_prssd_data));
	prssdp->order = PSF_ORDER_PRSSD;
	prssdp->suborder = 0x0e;	/* Read unit address configuration */
	/* all other bytes of prssdp must be zero */

	ccw = cqr->cpaddr;
	ccw->cmd_code = DASD_ECKD_CCW_PSF;
	ccw->count = sizeof(struct dasd_psf_prssd_data);
	ccw->flags |= CCW_FLAG_CC;
	ccw->cda = (__u32)(addr_t) prssdp;

	/* Read Subsystem Data - feature codes */
	memset(lcu->uac, 0, sizeof(*(lcu->uac)));

	ccw++;
	ccw->cmd_code = DASD_ECKD_CCW_RSSD;
	ccw->count = sizeof(*(lcu->uac));
	ccw->cda = (__u32)(addr_t) lcu->uac;

	cqr->buildclk = get_clock();
	cqr->status = DASD_CQR_FILLED;

	/* need to unset flag here to detect race with summary unit check */
	spin_lock_irqsave(&lcu->lock, flags);
	lcu->flags &= ~NEED_UAC_UPDATE;
	spin_unlock_irqrestore(&lcu->lock, flags);

	do {
		rc = dasd_sleep_on(cqr);
	} while (rc && (cqr->retries > 0));
	if (rc) {
		spin_lock_irqsave(&lcu->lock, flags);
		lcu->flags |= NEED_UAC_UPDATE;
		spin_unlock_irqrestore(&lcu->lock, flags);
	}
	dasd_kfree_request(cqr, cqr->memdev);
	return rc;
}

static int _lcu_update(struct dasd_device *refdev, struct alias_lcu *lcu)
{
	unsigned long flags;
	struct alias_pav_group *pavgroup, *tempgroup;
	struct dasd_device *device, *tempdev;
	int i, rc;
	struct dasd_eckd_private *private;

	spin_lock_irqsave(&lcu->lock, flags);
	list_for_each_entry_safe(pavgroup, tempgroup, &lcu->grouplist, group) {
		list_for_each_entry_safe(device, tempdev, &pavgroup->baselist,
					 alias_list) {
			list_move(&device->alias_list, &lcu->active_devices);
			private = (struct dasd_eckd_private *) device->private;
			private->pavgroup = NULL;
		}
		list_for_each_entry_safe(device, tempdev, &pavgroup->aliaslist,
					 alias_list) {
			list_move(&device->alias_list, &lcu->active_devices);
			private = (struct dasd_eckd_private *) device->private;
			private->pavgroup = NULL;
		}
		list_del(&pavgroup->group);
		kfree(pavgroup);
	}
	spin_unlock_irqrestore(&lcu->lock, flags);

	rc = read_unit_address_configuration(refdev, lcu);
	if (rc)
		return rc;

	spin_lock_irqsave(&lcu->lock, flags);
	lcu->pav = NO_PAV;
	for (i = 0; i < MAX_DEVICES_PER_LCU; ++i) {
		switch (lcu->uac->unit[i].ua_type) {
		case UA_BASE_PAV_ALIAS:
			lcu->pav = BASE_PAV;
			break;
		case UA_HYPER_PAV_ALIAS:
			lcu->pav = HYPER_PAV;
			break;
		}
		if (lcu->pav != NO_PAV)
			break;
	}

	list_for_each_entry_safe(device, tempdev, &lcu->active_devices,
				 alias_list) {
		_add_device_to_lcu(lcu, device);
	}
	spin_unlock_irqrestore(&lcu->lock, flags);
	return 0;
}

static void lcu_update_work(struct work_struct *work)
{
	struct alias_lcu *lcu;
	struct read_uac_work_data *ruac_data;
	struct dasd_device *device;
	unsigned long flags;
	int rc;

	ruac_data = container_of(work, struct read_uac_work_data, dwork.work);
	lcu = container_of(ruac_data, struct alias_lcu, ruac_data);
	device = ruac_data->device;
	rc = _lcu_update(device, lcu);
	/*
	 * Need to check flags again, as there could have been another
	 * prepare_update or a new device a new device while we were still
	 * processing the data
	 */
	spin_lock_irqsave(&lcu->lock, flags);
	if (rc || (lcu->flags & NEED_UAC_UPDATE)) {
		DEV_MESSAGE(KERN_WARNING, device, "could not update"
			    " alias data in lcu (rc = %d), retry later", rc);
		schedule_delayed_work(&lcu->ruac_data.dwork, 30*HZ);
	} else {
		lcu->ruac_data.device = NULL;
		lcu->flags &= ~UPDATE_PENDING;
	}
	spin_unlock_irqrestore(&lcu->lock, flags);
}

static int _schedule_lcu_update(struct alias_lcu *lcu,
				struct dasd_device *device)
{
	struct dasd_device *usedev = NULL;
	struct alias_pav_group *group;

	lcu->flags |= NEED_UAC_UPDATE;
	if (lcu->ruac_data.device) {
		/* already scheduled or running */
		return 0;
	}
	if (device && !list_empty(&device->alias_list))
		usedev = device;

	if (!usedev && !list_empty(&lcu->grouplist)) {
		group = list_first_entry(&lcu->grouplist,
					 struct alias_pav_group, group);
		if (!list_empty(&group->baselist))
			usedev = list_first_entry(&group->baselist,
						  struct dasd_device,
						  alias_list);
		else if (!list_empty(&group->aliaslist))
			usedev = list_first_entry(&group->aliaslist,
						  struct dasd_device,
						  alias_list);
	}
	if (!usedev && !list_empty(&lcu->active_devices)) {
		usedev = list_first_entry(&lcu->active_devices,
					  struct dasd_device, alias_list);
	}
	/*
	 * if we haven't found a proper device yet, give up for now, the next
	 * device that will be set active will trigger an lcu update
	 */
	if (!usedev)
		return -EINVAL;
	lcu->ruac_data.device = usedev;
	schedule_delayed_work(&lcu->ruac_data.dwork, 0);
	return 0;
}

int dasd_alias_add_device(struct dasd_device *device)
{
	struct dasd_eckd_private *private;
	struct alias_lcu *lcu;
	unsigned long flags;
	int rc;

	private = (struct dasd_eckd_private *) device->private;
	lcu = private->lcu;
	rc = 0;
	spin_lock_irqsave(&lcu->lock, flags);
	if (!(lcu->flags & UPDATE_PENDING)) {
		rc = _add_device_to_lcu(lcu, device);
		if (rc)
			lcu->flags |= UPDATE_PENDING;
	}
	if (lcu->flags & UPDATE_PENDING) {
		list_move(&device->alias_list, &lcu->active_devices);
		_schedule_lcu_update(lcu, device);
	}
	spin_unlock_irqrestore(&lcu->lock, flags);
	return rc;
}

int dasd_alias_remove_device(struct dasd_device *device)
{
	struct dasd_eckd_private *private;
	struct alias_lcu *lcu;
	unsigned long flags;

	private = (struct dasd_eckd_private *) device->private;
	lcu = private->lcu;
	spin_lock_irqsave(&lcu->lock, flags);
	_remove_device_from_lcu(lcu, device);
	spin_unlock_irqrestore(&lcu->lock, flags);
	return 0;
}

struct dasd_device *dasd_alias_get_start_dev(struct dasd_device *base_device)
{

	struct dasd_device *alias_device;
	struct alias_pav_group *group;
	struct alias_lcu *lcu;
	struct dasd_eckd_private *private, *alias_priv;
	unsigned long flags;

	private = (struct dasd_eckd_private *) base_device->private;
	group = private->pavgroup;
	lcu = private->lcu;
	if (!group || !lcu)
		return NULL;
	if (lcu->pav == NO_PAV ||
	    lcu->flags & (NEED_UAC_UPDATE | UPDATE_PENDING))
		return NULL;

	spin_lock_irqsave(&lcu->lock, flags);
	alias_device = group->next;
	if (!alias_device) {
		if (list_empty(&group->aliaslist)) {
			spin_unlock_irqrestore(&lcu->lock, flags);
			return NULL;
		} else {
			alias_device = list_first_entry(&group->aliaslist,
							struct dasd_device,
							alias_list);
		}
	}
	if (list_is_last(&alias_device->alias_list, &group->aliaslist))
		group->next = list_first_entry(&group->aliaslist,
					       struct dasd_device, alias_list);
	else
		group->next = list_first_entry(&alias_device->alias_list,
					       struct dasd_device, alias_list);
	spin_unlock_irqrestore(&lcu->lock, flags);
	alias_priv = (struct dasd_eckd_private *) alias_device->private;
	if ((alias_priv->count < private->count) && !alias_device->stopped)
		return alias_device;
	else
		return NULL;
}

/*
 * Summary unit check handling depends on the way alias devices
 * are handled so it is done here rather then in dasd_eckd.c
 */
static int reset_summary_unit_check(struct alias_lcu *lcu,
				    struct dasd_device *device,
				    char reason)
{
	struct dasd_ccw_req *cqr;
	int rc = 0;

	cqr = lcu->rsu_cqr;
	strncpy((char *) &cqr->magic, "ECKD", 4);
	ASCEBC((char *) &cqr->magic, 4);
	cqr->cpaddr->cmd_code = DASD_ECKD_CCW_RSCK;
	cqr->cpaddr->flags = 0 ;
	cqr->cpaddr->count = 16;
	cqr->cpaddr->cda = (__u32)(addr_t) cqr->data;
	((char *)cqr->data)[0] = reason;

	clear_bit(DASD_CQR_FLAGS_USE_ERP, &cqr->flags);
	cqr->retries = 255;	/* set retry counter to enable basic ERP */
	cqr->startdev = device;
	cqr->memdev = device;
	cqr->block = NULL;
	cqr->expires = 5 * HZ;
	cqr->buildclk = get_clock();
	cqr->status = DASD_CQR_FILLED;

	rc = dasd_sleep_on_immediatly(cqr);
	return rc;
}

static void _restart_all_base_devices_on_lcu(struct alias_lcu *lcu)
{
	struct alias_pav_group *pavgroup;
	struct dasd_device *device;
	struct dasd_eckd_private *private;

	/* active and inactive list can contain alias as well as base devices */
	list_for_each_entry(device, &lcu->active_devices, alias_list) {
		private = (struct dasd_eckd_private *) device->private;
		if (private->uid.type != UA_BASE_DEVICE)
			continue;
		dasd_schedule_block_bh(device->block);
		dasd_schedule_device_bh(device);
	}
	list_for_each_entry(device, &lcu->inactive_devices, alias_list) {
		private = (struct dasd_eckd_private *) device->private;
		if (private->uid.type != UA_BASE_DEVICE)
			continue;
		dasd_schedule_block_bh(device->block);
		dasd_schedule_device_bh(device);
	}
	list_for_each_entry(pavgroup, &lcu->grouplist, group) {
		list_for_each_entry(device, &pavgroup->baselist, alias_list) {
			dasd_schedule_block_bh(device->block);
			dasd_schedule_device_bh(device);
		}
	}
}

static void flush_all_alias_devices_on_lcu(struct alias_lcu *lcu)
{
	struct alias_pav_group *pavgroup;
	struct dasd_device *device, *temp;
	struct dasd_eckd_private *private;
	int rc;
	unsigned long flags;
	LIST_HEAD(active);

	/*
	 * Problem here ist that dasd_flush_device_queue may wait
	 * for termination of a request to complete. We can't keep
	 * the lcu lock during that time, so we must assume that
	 * the lists may have changed.
	 * Idea: first gather all active alias devices in a separate list,
	 * then flush the first element of this list unlocked, and afterwards
	 * check if it is still on the list before moving it to the
	 * active_devices list.
	 */

	spin_lock_irqsave(&lcu->lock, flags);
	list_for_each_entry_safe(device, temp, &lcu->active_devices,
				 alias_list) {
		private = (struct dasd_eckd_private *) device->private;
		if (private->uid.type == UA_BASE_DEVICE)
			continue;
		list_move(&device->alias_list, &active);
	}

	list_for_each_entry(pavgroup, &lcu->grouplist, group) {
		list_splice_init(&pavgroup->aliaslist, &active);
	}
	while (!list_empty(&active)) {
		device = list_first_entry(&active, struct dasd_device,
					  alias_list);
		spin_unlock_irqrestore(&lcu->lock, flags);
		rc = dasd_flush_device_queue(device);
		spin_lock_irqsave(&lcu->lock, flags);
		/*
		 * only move device around if it wasn't moved away while we
		 * were waiting for the flush
		 */
		if (device == list_first_entry(&active,
					       struct dasd_device, alias_list))
			list_move(&device->alias_list, &lcu->active_devices);
	}
	spin_unlock_irqrestore(&lcu->lock, flags);
}

static void __stop_device_on_lcu(struct dasd_device *device,
				 struct dasd_device *pos)
{
	/* If pos == device then device is already locked! */
	if (pos == device) {
		pos->stopped |= DASD_STOPPED_SU;
		return;
	}
	spin_lock(get_ccwdev_lock(pos->cdev));
	pos->stopped |= DASD_STOPPED_SU;
	spin_unlock(get_ccwdev_lock(pos->cdev));
}

/*
 * This function is called in interrupt context, so the
 * cdev lock for device is already locked!
 */
static void _stop_all_devices_on_lcu(struct alias_lcu *lcu,
				     struct dasd_device *device)
{
	struct alias_pav_group *pavgroup;
	struct dasd_device *pos;

	list_for_each_entry(pos, &lcu->active_devices, alias_list)
		__stop_device_on_lcu(device, pos);
	list_for_each_entry(pos, &lcu->inactive_devices, alias_list)
		__stop_device_on_lcu(device, pos);
	list_for_each_entry(pavgroup, &lcu->grouplist, group) {
		list_for_each_entry(pos, &pavgroup->baselist, alias_list)
			__stop_device_on_lcu(device, pos);
		list_for_each_entry(pos, &pavgroup->aliaslist, alias_list)
			__stop_device_on_lcu(device, pos);
	}
}

static void _unstop_all_devices_on_lcu(struct alias_lcu *lcu)
{
	struct alias_pav_group *pavgroup;
	struct dasd_device *device;
	unsigned long flags;

	list_for_each_entry(device, &lcu->active_devices, alias_list) {
		spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
		device->stopped &= ~DASD_STOPPED_SU;
		spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
	}

	list_for_each_entry(device, &lcu->inactive_devices, alias_list) {
		spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
		device->stopped &= ~DASD_STOPPED_SU;
		spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
	}

	list_for_each_entry(pavgroup, &lcu->grouplist, group) {
		list_for_each_entry(device, &pavgroup->baselist, alias_list) {
			spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
			device->stopped &= ~DASD_STOPPED_SU;
			spin_unlock_irqrestore(get_ccwdev_lock(device->cdev),
					       flags);
		}
		list_for_each_entry(device, &pavgroup->aliaslist, alias_list) {
			spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
			device->stopped &= ~DASD_STOPPED_SU;
			spin_unlock_irqrestore(get_ccwdev_lock(device->cdev),
					       flags);
		}
	}
}

static void summary_unit_check_handling_work(struct work_struct *work)
{
	struct alias_lcu *lcu;
	struct summary_unit_check_work_data *suc_data;
	unsigned long flags;
	struct dasd_device *device;

	suc_data = container_of(work, struct summary_unit_check_work_data,
				worker);
	lcu = container_of(suc_data, struct alias_lcu, suc_data);
	device = suc_data->device;

	/* 1. flush alias devices */
	flush_all_alias_devices_on_lcu(lcu);

	/* 2. reset summary unit check */
	spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
	device->stopped &= ~(DASD_STOPPED_SU | DASD_STOPPED_PENDING);
	spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
	reset_summary_unit_check(lcu, device, suc_data->reason);

	spin_lock_irqsave(&lcu->lock, flags);
	_unstop_all_devices_on_lcu(lcu);
	_restart_all_base_devices_on_lcu(lcu);
	/* 3. read new alias configuration */
	_schedule_lcu_update(lcu, device);
	lcu->suc_data.device = NULL;
	spin_unlock_irqrestore(&lcu->lock, flags);
}

/*
 * note: this will be called from int handler context (cdev locked)
 */
void dasd_alias_handle_summary_unit_check(struct dasd_device *device,
					  struct irb *irb)
{
	struct alias_lcu *lcu;
	char reason;
	struct dasd_eckd_private *private;

	private = (struct dasd_eckd_private *) device->private;

	reason = irb->ecw[8];
	DEV_MESSAGE(KERN_WARNING, device, "%s %x",
		    "eckd handle summary unit check: reason", reason);

	lcu = private->lcu;
	if (!lcu) {
		DEV_MESSAGE(KERN_WARNING, device, "%s",
			    "device not ready to handle summary"
			    " unit check (no lcu structure)");
		return;
	}
	spin_lock(&lcu->lock);
	_stop_all_devices_on_lcu(lcu, device);
	/* prepare for lcu_update */
	private->lcu->flags |= NEED_UAC_UPDATE | UPDATE_PENDING;
	/* If this device is about to be removed just return and wait for
	 * the next interrupt on a different device
	 */
	if (list_empty(&device->alias_list)) {
		DEV_MESSAGE(KERN_WARNING, device, "%s",
			    "device is in offline processing,"
			    " don't do summary unit check handling");
		spin_unlock(&lcu->lock);
		return;
	}
	if (lcu->suc_data.device) {
		/* already scheduled or running */
		DEV_MESSAGE(KERN_WARNING, device, "%s",
			    "previous instance of summary unit check worker"
			    " still pending");
		spin_unlock(&lcu->lock);
		return ;
	}
	lcu->suc_data.reason = reason;
	lcu->suc_data.device = device;
	spin_unlock(&lcu->lock);
	schedule_work(&lcu->suc_data.worker);
};