scm_blk.c

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/*
 * Block driver for s390 storage class memory.
 *
 * Copyright IBM Corp. 2012
 * Author(s): Sebastian Ott <[email protected]>
 */

#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 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);
    scm_request_done(scmrq);
    scm_ensure_queue_restart(bdev);
}

void scm_request_finish(struct scm_request *scmrq)
{
    scm_release_cluster(scmrq);
    blk_end_request_all(scmrq->request, scmrq->error);
    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;

        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)) {
            blk_start_request(req);
            scm_initiate_cluster_request(scmrq);
            return;
        }
        scm_request_prepare(scmrq);
        blk_start_request(req);

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

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_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) {
            if (scm_start_aob(scmrq->aob)) {
                spin_lock_irqsave(&bdev->rq_lock, flags);
                scm_request_requeue(scmrq);
                spin_unlock_irqrestore(&bdev->rq_lock, flags);
            }
            /* 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);
        atomic_dec(&bdev->queued_reqs);
        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;
    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);
}

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);