scm_blk_cluster.c

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

#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"

static unsigned int write_cluster_size = 64;
module_param(write_cluster_size, uint, S_IRUGO);
MODULE_PARM_DESC(write_cluster_size,
         "Number of pages used for contiguous writes.");

#define CLUSTER_SIZE (write_cluster_size * PAGE_SIZE)

void __scm_free_rq_cluster(struct scm_request *scmrq)
{
    int i;

    if (!scmrq->cluster.buf)
        return;

    for (i = 0; i < 2 * write_cluster_size; i++)
        free_page((unsigned long) scmrq->cluster.buf[i]);

    kfree(scmrq->cluster.buf);
}

int __scm_alloc_rq_cluster(struct scm_request *scmrq)
{
    int i;

    scmrq->cluster.buf = kzalloc(sizeof(void *) * 2 * write_cluster_size,
                 GFP_KERNEL);
    if (!scmrq->cluster.buf)
        return -ENOMEM;

    for (i = 0; i < 2 * write_cluster_size; i++) {
        scmrq->cluster.buf[i] = (void *) get_zeroed_page(GFP_DMA);
        if (!scmrq->cluster.buf[i])
            return -ENOMEM;
    }
    INIT_LIST_HEAD(&scmrq->cluster.list);
    return 0;
}

void scm_request_cluster_init(struct scm_request *scmrq)
{
    scmrq->cluster.state = CLUSTER_NONE;
}

static bool clusters_intersect(struct scm_request *A, struct scm_request *B)
{
    unsigned long firstA, lastA, firstB, lastB;

    firstA = ((u64) blk_rq_pos(A->request) << 9) / CLUSTER_SIZE;
    lastA = (((u64) blk_rq_pos(A->request) << 9) +
            blk_rq_bytes(A->request) - 1) / CLUSTER_SIZE;

    firstB = ((u64) blk_rq_pos(B->request) << 9) / CLUSTER_SIZE;
    lastB = (((u64) blk_rq_pos(B->request) << 9) +
            blk_rq_bytes(B->request) - 1) / CLUSTER_SIZE;

    return (firstB <= lastA && firstA <= lastB);
}

bool scm_reserve_cluster(struct scm_request *scmrq)
{
    struct scm_blk_dev *bdev = scmrq->bdev;
    struct scm_request *iter;

    if (write_cluster_size == 0)
        return true;

    spin_lock(&bdev->lock);
    list_for_each_entry(iter, &bdev->cluster_list, cluster.list) {
        if (clusters_intersect(scmrq, iter) &&
            (rq_data_dir(scmrq->request) == WRITE ||
             rq_data_dir(iter->request) == WRITE)) {
            spin_unlock(&bdev->lock);
            return false;
        }
    }
    list_add(&scmrq->cluster.list, &bdev->cluster_list);
    spin_unlock(&bdev->lock);

    return true;
}

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

    if (write_cluster_size == 0)
        return;

    spin_lock_irqsave(&bdev->lock, flags);
    list_del(&scmrq->cluster.list);
    spin_unlock_irqrestore(&bdev->lock, flags);
}

void scm_blk_dev_cluster_setup(struct scm_blk_dev *bdev)
{
    INIT_LIST_HEAD(&bdev->cluster_list);
    blk_queue_io_opt(bdev->rq, CLUSTER_SIZE);
}

static void scm_prepare_cluster_request(struct scm_request *scmrq)
{
    struct scm_blk_dev *bdev = scmrq->bdev;
    struct scm_device *scmdev = bdev->gendisk->private_data;
    struct request *req = scmrq->request;
    struct aidaw *aidaw = scmrq->aidaw;
    struct msb *msb = &scmrq->aob->msb[0];
    struct req_iterator iter;
    struct bio_vec *bv;
    int i = 0;
    u64 addr;

    switch (scmrq->cluster.state) {
    case CLUSTER_NONE:
        scmrq->cluster.state = CLUSTER_READ;
        /* fall through */
    case CLUSTER_READ:
        scmrq->aob->request.msb_count = 1;
        msb->bs = MSB_BS_4K;
        msb->oc = MSB_OC_READ;
        msb->flags = MSB_FLAG_IDA;
        msb->data_addr = (u64) aidaw;
        msb->blk_count = write_cluster_size;

        addr = scmdev->address + ((u64) blk_rq_pos(req) << 9);
        msb->scm_addr = round_down(addr, CLUSTER_SIZE);

        if (msb->scm_addr !=
            round_down(addr + (u64) blk_rq_bytes(req) - 1,
                   CLUSTER_SIZE))
            msb->blk_count = 2 * write_cluster_size;

        for (i = 0; i < msb->blk_count; i++) {
            aidaw->data_addr = (u64) scmrq->cluster.buf[i];
            aidaw++;
        }

        break;
    case CLUSTER_WRITE:
        msb->oc = MSB_OC_WRITE;

        for (addr = msb->scm_addr;
             addr < scmdev->address + ((u64) blk_rq_pos(req) << 9);
             addr += PAGE_SIZE) {
            aidaw->data_addr = (u64) scmrq->cluster.buf[i];
            aidaw++;
            i++;
        }
        rq_for_each_segment(bv, req, iter) {
            aidaw->data_addr = (u64) page_address(bv->bv_page);
            aidaw++;
            i++;
        }
        for (; i < msb->blk_count; i++) {
            aidaw->data_addr = (u64) scmrq->cluster.buf[i];
            aidaw++;
        }
        break;
    }
}

bool scm_need_cluster_request(struct scm_request *scmrq)
{
    if (rq_data_dir(scmrq->request) == READ)
        return false;

    return blk_rq_bytes(scmrq->request) < CLUSTER_SIZE;
}

/* Called with queue lock held. */
void scm_initiate_cluster_request(struct scm_request *scmrq)
{
    scm_prepare_cluster_request(scmrq);
    if (scm_start_aob(scmrq->aob))
        scm_request_requeue(scmrq);
}

bool scm_test_cluster_request(struct scm_request *scmrq)
{
    return scmrq->cluster.state != CLUSTER_NONE;
}

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

    switch (scmrq->cluster.state) {
    case CLUSTER_NONE:
        BUG();
        break;
    case CLUSTER_READ:
        if (scmrq->error) {
            scm_request_finish(scmrq);
            break;
        }
        scmrq->cluster.state = CLUSTER_WRITE;
        spin_lock_irqsave(&bdev->rq_lock, flags);
        scm_initiate_cluster_request(scmrq);
        spin_unlock_irqrestore(&bdev->rq_lock, flags);
        break;
    case CLUSTER_WRITE:
        scm_request_finish(scmrq);
        break;
    }
}

bool scm_cluster_size_valid(void)
{
    return write_cluster_size == 0 || write_cluster_size == 32 ||
        write_cluster_size == 64 || write_cluster_size == 128;
}