drivers/s390/block/scm_blk.c - kernel/msm-5.4 - Gitiles

 /*
  * Block driver for s390 storage class memory.
  *
  * Copyright IBM Corp. 2012
  * Author(s): Sebastian Ott <sebott@linux.vnet.ibm.com>
  */

 #define KMSG_COMPONENT "scm_block"
 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt

 #include <linux/interrupt.h>
 #include <linux/spinlock.h>
 #include <linux/module.h>
 #include <linux/blkdev.h>
 #include <linux/genhd.h>
 #include <linux/slab.h>
 #include <linux/list.h>
 #include <asm/eadm.h>
 #include "scm_blk.h"

 debug_info_t *scm_debug;
 static int scm_major;
 static DEFINE_SPINLOCK(list_lock);
 static LIST_HEAD(inactive_requests);
 static unsigned int nr_requests = 64;
 static atomic_t nr_devices = ATOMIC_INIT(0);
 module_param(nr_requests, uint, S_IRUGO);
 MODULE_PARM_DESC(nr_requests, "Number of parallel requests.");

 MODULE_DESCRIPTION("Block driver for s390 storage class memory.");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS("scm:scmdev*");

 static void __scm_free_rq(struct scm_request *scmrq)
 {
 	struct aob_rq_header *aobrq = to_aobrq(scmrq);

 	free_page((unsigned long) scmrq->aob);
 	free_page((unsigned long) scmrq->aidaw);
 	__scm_free_rq_cluster(scmrq);
 	kfree(aobrq);
 }

 static void scm_free_rqs(void)
 {
 	struct list_head *iter, *safe;
 	struct scm_request *scmrq;

 	spin_lock_irq(&list_lock);
 	list_for_each_safe(iter, safe, &inactive_requests) {
 		scmrq = list_entry(iter, struct scm_request, list);
 		list_del(&scmrq->list);
 		__scm_free_rq(scmrq);
 	}
 	spin_unlock_irq(&list_lock);
 }

 static int __scm_alloc_rq(void)
 {
 	struct aob_rq_header *aobrq;
 	struct scm_request *scmrq;

 	aobrq = kzalloc(sizeof(*aobrq) + sizeof(*scmrq), GFP_KERNEL);
 	if (!aobrq)
 		return -ENOMEM;

 	scmrq = (void *) aobrq->data;
 	scmrq->aidaw = (void *) get_zeroed_page(GFP_DMA);
 	scmrq->aob = (void *) get_zeroed_page(GFP_DMA);
 	if (!scmrq->aob || !scmrq->aidaw) {
 		__scm_free_rq(scmrq);
 		return -ENOMEM;
 	}

 	if (__scm_alloc_rq_cluster(scmrq)) {
 		__scm_free_rq(scmrq);
 		return -ENOMEM;
 	}

 	INIT_LIST_HEAD(&scmrq->list);
 	spin_lock_irq(&list_lock);
 	list_add(&scmrq->list, &inactive_requests);
 	spin_unlock_irq(&list_lock);

 	return 0;
 }

 static int scm_alloc_rqs(unsigned int nrqs)
 {
 	int ret = 0;

 	while (nrqs-- && !ret)
 		ret = __scm_alloc_rq();

 	return ret;
 }

 static struct scm_request *scm_request_fetch(void)
 {
 	struct scm_request *scmrq = NULL;

 	spin_lock(&list_lock);
 	if (list_empty(&inactive_requests))
 		goto out;
 	scmrq = list_first_entry(&inactive_requests, struct scm_request, list);
 	list_del(&scmrq->list);
 out:
 	spin_unlock(&list_lock);
 	return scmrq;
 }

 static void scm_request_done(struct scm_request *scmrq)
 {
 	unsigned long flags;

 	spin_lock_irqsave(&list_lock, flags);
 	list_add(&scmrq->list, &inactive_requests);
 	spin_unlock_irqrestore(&list_lock, flags);
 }

 static int scm_open(struct block_device *blkdev, fmode_t mode)
 {
 	return scm_get_ref();
 }

 static int scm_release(struct gendisk *gendisk, fmode_t mode)
 {
 	scm_put_ref();
 	return 0;
 }

 static const struct block_device_operations scm_blk_devops = {
 	.owner = THIS_MODULE,
 	.open = scm_open,
 	.release = scm_release,
 };

 static bool scm_permit_request(struct scm_blk_dev *bdev, struct request *req)
 {
 	return rq_data_dir(req) != WRITE || bdev->state != SCM_WR_PROHIBIT;
 }

 static void scm_request_prepare(struct scm_request *scmrq)
 {
 	struct scm_blk_dev *bdev = scmrq->bdev;
 	struct scm_device *scmdev = bdev->gendisk->private_data;
 	struct aidaw *aidaw = scmrq->aidaw;
 	struct msb *msb = &scmrq->aob->msb[0];
 	struct req_iterator iter;
 	struct bio_vec *bv;

 	msb->bs = MSB_BS_4K;
 	scmrq->aob->request.msb_count = 1;
 	msb->scm_addr = scmdev->address +
 		((u64) blk_rq_pos(scmrq->request) << 9);
 	msb->oc = (rq_data_dir(scmrq->request) == READ) ?
 		MSB_OC_READ : MSB_OC_WRITE;
 	msb->flags |= MSB_FLAG_IDA;
 	msb->data_addr = (u64) aidaw;

 	rq_for_each_segment(bv, scmrq->request, iter) {
 		WARN_ON(bv->bv_offset);
 		msb->blk_count += bv->bv_len >> 12;
 		aidaw->data_addr = (u64) page_address(bv->bv_page);
 		aidaw++;
 	}
 }

 static inline void scm_request_init(struct scm_blk_dev *bdev,
 				    struct scm_request *scmrq,
 				    struct request *req)
 {
 	struct aob_rq_header *aobrq = to_aobrq(scmrq);
 	struct aob *aob = scmrq->aob;

 	memset(aob, 0, sizeof(*aob));
 	memset(scmrq->aidaw, 0, PAGE_SIZE);
 	aobrq->scmdev = bdev->scmdev;
 	aob->request.cmd_code = ARQB_CMD_MOVE;
 	aob->request.data = (u64) aobrq;
 	scmrq->request = req;
 	scmrq->bdev = bdev;
 	scmrq->retries = 4;
 	scmrq->error = 0;
 	scm_request_cluster_init(scmrq);
 }

 static void scm_ensure_queue_restart(struct scm_blk_dev *bdev)
 {
 	if (atomic_read(&bdev->queued_reqs)) {
 		/* Queue restart is triggered by the next interrupt. */
 		return;
 	}
 	blk_delay_queue(bdev->rq, SCM_QUEUE_DELAY);
 }

 void scm_request_requeue(struct scm_request *scmrq)
 {
 	struct scm_blk_dev *bdev = scmrq->bdev;

 	scm_release_cluster(scmrq);
 	blk_requeue_request(bdev->rq, scmrq->request);
 	atomic_dec(&bdev->queued_reqs);
 	scm_request_done(scmrq);
 	scm_ensure_queue_restart(bdev);
 }

 void scm_request_finish(struct scm_request *scmrq)
 {
 	struct scm_blk_dev *bdev = scmrq->bdev;

 	scm_release_cluster(scmrq);
 	blk_end_request_all(scmrq->request, scmrq->error);
 	atomic_dec(&bdev->queued_reqs);
 	scm_request_done(scmrq);
 }

 static void scm_blk_request(struct request_queue *rq)
 {
 	struct scm_device *scmdev = rq->queuedata;
 	struct scm_blk_dev *bdev = dev_get_drvdata(&scmdev->dev);
 	struct scm_request *scmrq;
 	struct request *req;
 	int ret;

 	while ((req = blk_peek_request(rq))) {
 		if (req->cmd_type != REQ_TYPE_FS)
 			continue;

 		if (!scm_permit_request(bdev, req)) {
 			scm_ensure_queue_restart(bdev);
 			return;
 		}
 		scmrq = scm_request_fetch();
 		if (!scmrq) {
 			SCM_LOG(5, "no request");
 			scm_ensure_queue_restart(bdev);
 			return;
 		}
 		scm_request_init(bdev, scmrq, req);
 		if (!scm_reserve_cluster(scmrq)) {
 			SCM_LOG(5, "cluster busy");
 			scm_request_done(scmrq);
 			return;
 		}
 		if (scm_need_cluster_request(scmrq)) {
 			atomic_inc(&bdev->queued_reqs);
 			blk_start_request(req);
 			scm_initiate_cluster_request(scmrq);
 			return;
 		}
 		scm_request_prepare(scmrq);
 		atomic_inc(&bdev->queued_reqs);
 		blk_start_request(req);

 		ret = scm_start_aob(scmrq->aob);
 		if (ret) {
 			SCM_LOG(5, "no subchannel");
 			scm_request_requeue(scmrq);
 			return;
 		}
 	}
 }

 static void __scmrq_log_error(struct scm_request *scmrq)
 {
 	struct aob *aob = scmrq->aob;

 	if (scmrq->error == -ETIMEDOUT)
 		SCM_LOG(1, "Request timeout");
 	else {
 		SCM_LOG(1, "Request error");
 		SCM_LOG_HEX(1, &aob->response, sizeof(aob->response));
 	}
 	if (scmrq->retries)
 		SCM_LOG(1, "Retry request");
 	else
 		pr_err("An I/O operation to SCM failed with rc=%d\n",
 		       scmrq->error);
 }

 void scm_blk_irq(struct scm_device *scmdev, void *data, int error)
 {
 	struct scm_request *scmrq = data;
 	struct scm_blk_dev *bdev = scmrq->bdev;

 	scmrq->error = error;
 	if (error)
 		__scmrq_log_error(scmrq);

 	spin_lock(&bdev->lock);
 	list_add_tail(&scmrq->list, &bdev->finished_requests);
 	spin_unlock(&bdev->lock);
 	tasklet_hi_schedule(&bdev->tasklet);
 }

 static void scm_blk_handle_error(struct scm_request *scmrq)
 {
 	struct scm_blk_dev *bdev = scmrq->bdev;
 	unsigned long flags;

 	if (scmrq->error != -EIO)
 		goto restart;

 	/* For -EIO the response block is valid. */
 	switch (scmrq->aob->response.eqc) {
 	case EQC_WR_PROHIBIT:
 		spin_lock_irqsave(&bdev->lock, flags);
 		if (bdev->state != SCM_WR_PROHIBIT)
 			pr_info("%lu: Write access to the SCM increment is suspended\n",
 				(unsigned long) bdev->scmdev->address);
 		bdev->state = SCM_WR_PROHIBIT;
 		spin_unlock_irqrestore(&bdev->lock, flags);
 		goto requeue;
 	default:
 		break;
 	}

 restart:
 	if (!scm_start_aob(scmrq->aob))
 		return;

 requeue:
 	spin_lock_irqsave(&bdev->rq_lock, flags);
 	scm_request_requeue(scmrq);
 	spin_unlock_irqrestore(&bdev->rq_lock, flags);
 }

 static void scm_blk_tasklet(struct scm_blk_dev *bdev)
 {
 	struct scm_request *scmrq;
 	unsigned long flags;

 	spin_lock_irqsave(&bdev->lock, flags);
 	while (!list_empty(&bdev->finished_requests)) {
 		scmrq = list_first_entry(&bdev->finished_requests,
 					 struct scm_request, list);
 		list_del(&scmrq->list);
 		spin_unlock_irqrestore(&bdev->lock, flags);

 		if (scmrq->error && scmrq->retries-- > 0) {
 			scm_blk_handle_error(scmrq);

 			/* Request restarted or requeued, handle next. */
 			spin_lock_irqsave(&bdev->lock, flags);
 			continue;
 		}

 		if (scm_test_cluster_request(scmrq)) {
 			scm_cluster_request_irq(scmrq);
 			spin_lock_irqsave(&bdev->lock, flags);
 			continue;
 		}

 		scm_request_finish(scmrq);
 		spin_lock_irqsave(&bdev->lock, flags);
 	}
 	spin_unlock_irqrestore(&bdev->lock, flags);
 	/* Look out for more requests. */
 	blk_run_queue(bdev->rq);
 }

 int scm_blk_dev_setup(struct scm_blk_dev *bdev, struct scm_device *scmdev)
 {
 	struct request_queue *rq;
 	int len, ret = -ENOMEM;
 	unsigned int devindex, nr_max_blk;

 	devindex = atomic_inc_return(&nr_devices) - 1;
 	/* scma..scmz + scmaa..scmzz */
 	if (devindex > 701) {
 		ret = -ENODEV;
 		goto out;
 	}

 	bdev->scmdev = scmdev;
 	bdev->state = SCM_OPER;
 	spin_lock_init(&bdev->rq_lock);
 	spin_lock_init(&bdev->lock);
 	INIT_LIST_HEAD(&bdev->finished_requests);
 	atomic_set(&bdev->queued_reqs, 0);
 	tasklet_init(&bdev->tasklet,
 		     (void (*)(unsigned long)) scm_blk_tasklet,
 		     (unsigned long) bdev);

 	rq = blk_init_queue(scm_blk_request, &bdev->rq_lock);
 	if (!rq)
 		goto out;

 	bdev->rq = rq;
 	nr_max_blk = min(scmdev->nr_max_block,
 			 (unsigned int) (PAGE_SIZE / sizeof(struct aidaw)));

 	blk_queue_logical_block_size(rq, 1 << 12);
 	blk_queue_max_hw_sectors(rq, nr_max_blk << 3); /* 8 * 512 = blk_size */
 	blk_queue_max_segments(rq, nr_max_blk);
 	queue_flag_set_unlocked(QUEUE_FLAG_NONROT, rq);
 	scm_blk_dev_cluster_setup(bdev);

 	bdev->gendisk = alloc_disk(SCM_NR_PARTS);
 	if (!bdev->gendisk)
 		goto out_queue;

 	rq->queuedata = scmdev;
 	bdev->gendisk->driverfs_dev = &scmdev->dev;
 	bdev->gendisk->private_data = scmdev;
 	bdev->gendisk->fops = &scm_blk_devops;
 	bdev->gendisk->queue = rq;
 	bdev->gendisk->major = scm_major;
 	bdev->gendisk->first_minor = devindex * SCM_NR_PARTS;

 	len = snprintf(bdev->gendisk->disk_name, DISK_NAME_LEN, "scm");
 	if (devindex > 25) {
 		len += snprintf(bdev->gendisk->disk_name + len,
 				DISK_NAME_LEN - len, "%c",
 				'a' + (devindex / 26) - 1);
 		devindex = devindex % 26;
 	}
 	snprintf(bdev->gendisk->disk_name + len, DISK_NAME_LEN - len, "%c",
 		 'a' + devindex);

 	/* 512 byte sectors */
 	set_capacity(bdev->gendisk, scmdev->size >> 9);
 	add_disk(bdev->gendisk);
 	return 0;

 out_queue:
 	blk_cleanup_queue(rq);
 out:
 	atomic_dec(&nr_devices);
 	return ret;
 }

 void scm_blk_dev_cleanup(struct scm_blk_dev *bdev)
 {
 	tasklet_kill(&bdev->tasklet);
 	del_gendisk(bdev->gendisk);
 	blk_cleanup_queue(bdev->gendisk->queue);
 	put_disk(bdev->gendisk);
 }

 void scm_blk_set_available(struct scm_blk_dev *bdev)
 {
 	unsigned long flags;

 	spin_lock_irqsave(&bdev->lock, flags);
 	if (bdev->state == SCM_WR_PROHIBIT)
 		pr_info("%lu: Write access to the SCM increment is restored\n",
 			(unsigned long) bdev->scmdev->address);
 	bdev->state = SCM_OPER;
 	spin_unlock_irqrestore(&bdev->lock, flags);
 }

 static int __init scm_blk_init(void)
 {
 	int ret = -EINVAL;

 	if (!scm_cluster_size_valid())
 		goto out;

 	ret = register_blkdev(0, "scm");
 	if (ret < 0)
 		goto out;

 	scm_major = ret;
 	if (scm_alloc_rqs(nr_requests))
 		goto out_unreg;

 	scm_debug = debug_register("scm_log", 16, 1, 16);
 	if (!scm_debug)
 		goto out_free;

 	debug_register_view(scm_debug, &debug_hex_ascii_view);
 	debug_set_level(scm_debug, 2);

 	ret = scm_drv_init();
 	if (ret)
 		goto out_dbf;

 	return ret;

 out_dbf:
 	debug_unregister(scm_debug);
 out_free:
 	scm_free_rqs();
 out_unreg:
 	unregister_blkdev(scm_major, "scm");
 out:
 	return ret;
 }
 module_init(scm_blk_init);

 static void __exit scm_blk_cleanup(void)
 {
 	scm_drv_cleanup();
 	debug_unregister(scm_debug);
 	scm_free_rqs();
 	unregister_blkdev(scm_major, "scm");
 }
 module_exit(scm_blk_cleanup);
	/*
	* Block driver for s390 storage class memory.
	*
	* Copyright IBM Corp. 2012
	* Author(s): Sebastian Ott <sebott@linux.vnet.ibm.com>
	*/

	#define KMSG_COMPONENT "scm_block"
	#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt

	#include <linux/interrupt.h>
	#include <linux/spinlock.h>
	#include <linux/module.h>
	#include <linux/blkdev.h>
	#include <linux/genhd.h>
	#include <linux/slab.h>
	#include <linux/list.h>
	#include <asm/eadm.h>
	#include "scm_blk.h"

	debug_info_t *scm_debug;
	static int scm_major;
	static DEFINE_SPINLOCK(list_lock);
	static LIST_HEAD(inactive_requests);
	static unsigned int nr_requests = 64;
	static atomic_t nr_devices = ATOMIC_INIT(0);
	module_param(nr_requests, uint, S_IRUGO);
	MODULE_PARM_DESC(nr_requests, "Number of parallel requests.");

	MODULE_DESCRIPTION("Block driver for s390 storage class memory.");
	MODULE_LICENSE("GPL");
	MODULE_ALIAS("scm:scmdev*");

	static void __scm_free_rq(struct scm_request *scmrq)
	{
	struct aob_rq_header *aobrq = to_aobrq(scmrq);

	free_page((unsigned long) scmrq->aob);
	free_page((unsigned long) scmrq->aidaw);
	__scm_free_rq_cluster(scmrq);
	kfree(aobrq);
	}

	static void scm_free_rqs(void)
	{
	struct list_head iter, safe;
	struct scm_request *scmrq;

	spin_lock_irq(&list_lock);
	list_for_each_safe(iter, safe, &inactive_requests) {
	scmrq = list_entry(iter, struct scm_request, list);
	list_del(&scmrq->list);
	__scm_free_rq(scmrq);
	}
	spin_unlock_irq(&list_lock);
	}

	static int __scm_alloc_rq(void)
	{
	struct aob_rq_header *aobrq;
	struct scm_request *scmrq;

	aobrq = kzalloc(sizeof(aobrq) + sizeof(scmrq), GFP_KERNEL);
	if (!aobrq)
	return -ENOMEM;

	scmrq = (void *) aobrq->data;
	scmrq->aidaw = (void *) get_zeroed_page(GFP_DMA);
	scmrq->aob = (void *) get_zeroed_page(GFP_DMA);
	if (!scmrq->aob \|\| !scmrq->aidaw) {
	__scm_free_rq(scmrq);
	return -ENOMEM;
	}

	if (__scm_alloc_rq_cluster(scmrq)) {
	__scm_free_rq(scmrq);
	return -ENOMEM;
	}

	INIT_LIST_HEAD(&scmrq->list);
	spin_lock_irq(&list_lock);
	list_add(&scmrq->list, &inactive_requests);
	spin_unlock_irq(&list_lock);

	return 0;
	}

	static int scm_alloc_rqs(unsigned int nrqs)
	{
	int ret = 0;

	while (nrqs-- && !ret)
	ret = __scm_alloc_rq();

	return ret;
	}

	static struct scm_request *scm_request_fetch(void)
	{
	struct scm_request *scmrq = NULL;

	spin_lock(&list_lock);
	if (list_empty(&inactive_requests))
	goto out;
	scmrq = list_first_entry(&inactive_requests, struct scm_request, list);
	list_del(&scmrq->list);
	out:
	spin_unlock(&list_lock);
	return scmrq;
	}

	static void scm_request_done(struct scm_request *scmrq)
	{
	unsigned long flags;

	spin_lock_irqsave(&list_lock, flags);
	list_add(&scmrq->list, &inactive_requests);
	spin_unlock_irqrestore(&list_lock, flags);
	}

	static int scm_open(struct block_device *blkdev, fmode_t mode)
	{
	return scm_get_ref();
	}

	static int scm_release(struct gendisk *gendisk, fmode_t mode)
	{
	scm_put_ref();
	return 0;
	}

	static const struct block_device_operations scm_blk_devops = {
	.owner = THIS_MODULE,
	.open = scm_open,
	.release = scm_release,
	};

	static bool scm_permit_request(struct scm_blk_dev bdev, struct request req)
	{
	return rq_data_dir(req) != WRITE \|\| bdev->state != SCM_WR_PROHIBIT;
	}

	static void scm_request_prepare(struct scm_request *scmrq)
	{
	struct scm_blk_dev *bdev = scmrq->bdev;
	struct scm_device *scmdev = bdev->gendisk->private_data;
	struct aidaw *aidaw = scmrq->aidaw;
	struct msb *msb = &scmrq->aob->msb[0];
	struct req_iterator iter;
	struct bio_vec *bv;

	msb->bs = MSB_BS_4K;
	scmrq->aob->request.msb_count = 1;
	msb->scm_addr = scmdev->address +
	((u64) blk_rq_pos(scmrq->request) << 9);
	msb->oc = (rq_data_dir(scmrq->request) == READ) ?
	MSB_OC_READ : MSB_OC_WRITE;
	msb->flags \|= MSB_FLAG_IDA;
	msb->data_addr = (u64) aidaw;

	rq_for_each_segment(bv, scmrq->request, iter) {
	WARN_ON(bv->bv_offset);
	msb->blk_count += bv->bv_len >> 12;
	aidaw->data_addr = (u64) page_address(bv->bv_page);
	aidaw++;
	}
	}

	static inline void scm_request_init(struct scm_blk_dev *bdev,
	struct scm_request *scmrq,
	struct request *req)
	{
	struct aob_rq_header *aobrq = to_aobrq(scmrq);
	struct aob *aob = scmrq->aob;

	memset(aob, 0, sizeof(*aob));
	memset(scmrq->aidaw, 0, PAGE_SIZE);
	aobrq->scmdev = bdev->scmdev;
	aob->request.cmd_code = ARQB_CMD_MOVE;
	aob->request.data = (u64) aobrq;
	scmrq->request = req;
	scmrq->bdev = bdev;
	scmrq->retries = 4;
	scmrq->error = 0;
	scm_request_cluster_init(scmrq);
	}

	static void scm_ensure_queue_restart(struct scm_blk_dev *bdev)
	{
	if (atomic_read(&bdev->queued_reqs)) {
	/* Queue restart is triggered by the next interrupt. */
	return;
	}
	blk_delay_queue(bdev->rq, SCM_QUEUE_DELAY);
	}

	void scm_request_requeue(struct scm_request *scmrq)
	{
	struct scm_blk_dev *bdev = scmrq->bdev;

	scm_release_cluster(scmrq);
	blk_requeue_request(bdev->rq, scmrq->request);
	atomic_dec(&bdev->queued_reqs);
	scm_request_done(scmrq);
	scm_ensure_queue_restart(bdev);
	}

	void scm_request_finish(struct scm_request *scmrq)
	{
	struct scm_blk_dev *bdev = scmrq->bdev;

	scm_release_cluster(scmrq);
	blk_end_request_all(scmrq->request, scmrq->error);
	atomic_dec(&bdev->queued_reqs);
	scm_request_done(scmrq);
	}

	static void scm_blk_request(struct request_queue *rq)
	{
	struct scm_device *scmdev = rq->queuedata;
	struct scm_blk_dev *bdev = dev_get_drvdata(&scmdev->dev);
	struct scm_request *scmrq;
	struct request *req;
	int ret;

	while ((req = blk_peek_request(rq))) {
	if (req->cmd_type != REQ_TYPE_FS)
	continue;

	if (!scm_permit_request(bdev, req)) {
	scm_ensure_queue_restart(bdev);
	return;
	}
	scmrq = scm_request_fetch();
	if (!scmrq) {
	SCM_LOG(5, "no request");
	scm_ensure_queue_restart(bdev);
	return;
	}
	scm_request_init(bdev, scmrq, req);
	if (!scm_reserve_cluster(scmrq)) {
	SCM_LOG(5, "cluster busy");
	scm_request_done(scmrq);
	return;
	}
	if (scm_need_cluster_request(scmrq)) {
	atomic_inc(&bdev->queued_reqs);
	blk_start_request(req);
	scm_initiate_cluster_request(scmrq);
	return;
	}
	scm_request_prepare(scmrq);
	atomic_inc(&bdev->queued_reqs);
	blk_start_request(req);

	ret = scm_start_aob(scmrq->aob);
	if (ret) {
	SCM_LOG(5, "no subchannel");
	scm_request_requeue(scmrq);
	return;
	}
	}
	}

	static void __scmrq_log_error(struct scm_request *scmrq)
	{
	struct aob *aob = scmrq->aob;

	if (scmrq->error == -ETIMEDOUT)
	SCM_LOG(1, "Request timeout");
	else {
	SCM_LOG(1, "Request error");
	SCM_LOG_HEX(1, &aob->response, sizeof(aob->response));
	}
	if (scmrq->retries)
	SCM_LOG(1, "Retry request");
	else
	pr_err("An I/O operation to SCM failed with rc=%d\n",
	scmrq->error);
	}

	void scm_blk_irq(struct scm_device scmdev, void data, int error)
	{
	struct scm_request *scmrq = data;
	struct scm_blk_dev *bdev = scmrq->bdev;

	scmrq->error = error;
	if (error)
	__scmrq_log_error(scmrq);

	spin_lock(&bdev->lock);
	list_add_tail(&scmrq->list, &bdev->finished_requests);
	spin_unlock(&bdev->lock);
	tasklet_hi_schedule(&bdev->tasklet);
	}

	static void scm_blk_handle_error(struct scm_request *scmrq)
	{
	struct scm_blk_dev *bdev = scmrq->bdev;
	unsigned long flags;

	if (scmrq->error != -EIO)
	goto restart;

	/* For -EIO the response block is valid. */
	switch (scmrq->aob->response.eqc) {
	case EQC_WR_PROHIBIT:
	spin_lock_irqsave(&bdev->lock, flags);
	if (bdev->state != SCM_WR_PROHIBIT)
	pr_info("%lu: Write access to the SCM increment is suspended\n",
	(unsigned long) bdev->scmdev->address);
	bdev->state = SCM_WR_PROHIBIT;
	spin_unlock_irqrestore(&bdev->lock, flags);
	goto requeue;
	default:
	break;
	}

	restart:
	if (!scm_start_aob(scmrq->aob))
	return;

	requeue:
	spin_lock_irqsave(&bdev->rq_lock, flags);
	scm_request_requeue(scmrq);
	spin_unlock_irqrestore(&bdev->rq_lock, flags);
	}

	static void scm_blk_tasklet(struct scm_blk_dev *bdev)
	{
	struct scm_request *scmrq;
	unsigned long flags;

	spin_lock_irqsave(&bdev->lock, flags);
	while (!list_empty(&bdev->finished_requests)) {
	scmrq = list_first_entry(&bdev->finished_requests,
	struct scm_request, list);
	list_del(&scmrq->list);
	spin_unlock_irqrestore(&bdev->lock, flags);

	if (scmrq->error && scmrq->retries-- > 0) {
	scm_blk_handle_error(scmrq);

	/* Request restarted or requeued, handle next. */
	spin_lock_irqsave(&bdev->lock, flags);
	continue;
	}

	if (scm_test_cluster_request(scmrq)) {
	scm_cluster_request_irq(scmrq);
	spin_lock_irqsave(&bdev->lock, flags);
	continue;
	}

	scm_request_finish(scmrq);
	spin_lock_irqsave(&bdev->lock, flags);
	}
	spin_unlock_irqrestore(&bdev->lock, flags);
	/* Look out for more requests. */
	blk_run_queue(bdev->rq);
	}

	int scm_blk_dev_setup(struct scm_blk_dev bdev, struct scm_device scmdev)
	{
	struct request_queue *rq;
	int len, ret = -ENOMEM;
	unsigned int devindex, nr_max_blk;

	devindex = atomic_inc_return(&nr_devices) - 1;
	/* scma..scmz + scmaa..scmzz */
	if (devindex > 701) {
	ret = -ENODEV;
	goto out;
	}

	bdev->scmdev = scmdev;
	bdev->state = SCM_OPER;
	spin_lock_init(&bdev->rq_lock);
	spin_lock_init(&bdev->lock);
	INIT_LIST_HEAD(&bdev->finished_requests);
	atomic_set(&bdev->queued_reqs, 0);
	tasklet_init(&bdev->tasklet,
	(void (*)(unsigned long)) scm_blk_tasklet,
	(unsigned long) bdev);

	rq = blk_init_queue(scm_blk_request, &bdev->rq_lock);
	if (!rq)
	goto out;

	bdev->rq = rq;
	nr_max_blk = min(scmdev->nr_max_block,
	(unsigned int) (PAGE_SIZE / sizeof(struct aidaw)));

	blk_queue_logical_block_size(rq, 1 << 12);
	blk_queue_max_hw_sectors(rq, nr_max_blk << 3); /* 8 * 512 = blk_size */
	blk_queue_max_segments(rq, nr_max_blk);
	queue_flag_set_unlocked(QUEUE_FLAG_NONROT, rq);
	scm_blk_dev_cluster_setup(bdev);

	bdev->gendisk = alloc_disk(SCM_NR_PARTS);
	if (!bdev->gendisk)
	goto out_queue;

	rq->queuedata = scmdev;
	bdev->gendisk->driverfs_dev = &scmdev->dev;
	bdev->gendisk->private_data = scmdev;
	bdev->gendisk->fops = &scm_blk_devops;
	bdev->gendisk->queue = rq;
	bdev->gendisk->major = scm_major;
	bdev->gendisk->first_minor = devindex * SCM_NR_PARTS;

	len = snprintf(bdev->gendisk->disk_name, DISK_NAME_LEN, "scm");
	if (devindex > 25) {
	len += snprintf(bdev->gendisk->disk_name + len,
	DISK_NAME_LEN - len, "%c",
	'a' + (devindex / 26) - 1);
	devindex = devindex % 26;
	}
	snprintf(bdev->gendisk->disk_name + len, DISK_NAME_LEN - len, "%c",
	'a' + devindex);

	/* 512 byte sectors */
	set_capacity(bdev->gendisk, scmdev->size >> 9);
	add_disk(bdev->gendisk);
	return 0;

	out_queue:
	blk_cleanup_queue(rq);
	out:
	atomic_dec(&nr_devices);
	return ret;
	}

	void scm_blk_dev_cleanup(struct scm_blk_dev *bdev)
	{
	tasklet_kill(&bdev->tasklet);
	del_gendisk(bdev->gendisk);
	blk_cleanup_queue(bdev->gendisk->queue);
	put_disk(bdev->gendisk);
	}

	void scm_blk_set_available(struct scm_blk_dev *bdev)
	{
	unsigned long flags;

	spin_lock_irqsave(&bdev->lock, flags);
	if (bdev->state == SCM_WR_PROHIBIT)
	pr_info("%lu: Write access to the SCM increment is restored\n",
	(unsigned long) bdev->scmdev->address);
	bdev->state = SCM_OPER;
	spin_unlock_irqrestore(&bdev->lock, flags);
	}

	static int __init scm_blk_init(void)
	{
	int ret = -EINVAL;

	if (!scm_cluster_size_valid())
	goto out;

	ret = register_blkdev(0, "scm");
	if (ret < 0)
	goto out;

	scm_major = ret;
	if (scm_alloc_rqs(nr_requests))
	goto out_unreg;

	scm_debug = debug_register("scm_log", 16, 1, 16);
	if (!scm_debug)
	goto out_free;

	debug_register_view(scm_debug, &debug_hex_ascii_view);
	debug_set_level(scm_debug, 2);

	ret = scm_drv_init();
	if (ret)
	goto out_dbf;

	return ret;

	out_dbf:
	debug_unregister(scm_debug);
	out_free:
	scm_free_rqs();
	out_unreg:
	unregister_blkdev(scm_major, "scm");
	out:
	return ret;
	}
	module_init(scm_blk_init);

	static void __exit scm_blk_cleanup(void)
	{
	scm_drv_cleanup();
	debug_unregister(scm_debug);
	scm_free_rqs();
	unregister_blkdev(scm_major, "scm");
	}
	module_exit(scm_blk_cleanup);