algos.c

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/* -*- linux-c -*- ------------------------------------------------------- *
 *
 *   Copyright 2002 H. Peter Anvin - All Rights Reserved
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
 *   Boston MA 02111-1307, USA; either version 2 of the License, or
 *   (at your option) any later version; incorporated herein by reference.
 *
 * ----------------------------------------------------------------------- */

/*
 * raid6/algos.c
 *
 * Algorithm list and algorithm selection for RAID-6
 */

#include <linux/raid/pq.h>
#ifndef __KERNEL__
#include <sys/mman.h>
#include <stdio.h>
#else
#include <linux/module.h>
#include <linux/gfp.h>
#if !RAID6_USE_EMPTY_ZERO_PAGE
/* In .bss so it's zeroed */
const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
EXPORT_SYMBOL(raid6_empty_zero_page);
#endif
#endif

struct raid6_calls raid6_call;
EXPORT_SYMBOL_GPL(raid6_call);

const struct raid6_calls * const raid6_algos[] = {
#if defined(__ia64__)
    &raid6_intx16,
    &raid6_intx32,
#endif
#if defined(__i386__) && !defined(__arch_um__)
    &raid6_mmxx1,
    &raid6_mmxx2,
    &raid6_sse1x1,
    &raid6_sse1x2,
    &raid6_sse2x1,
    &raid6_sse2x2,
#endif
#if defined(__x86_64__) && !defined(__arch_um__)
    &raid6_sse2x1,
    &raid6_sse2x2,
    &raid6_sse2x4,
#endif
#ifdef CONFIG_ALTIVEC
    &raid6_altivec1,
    &raid6_altivec2,
    &raid6_altivec4,
    &raid6_altivec8,
#endif
    &raid6_intx1,
    &raid6_intx2,
    &raid6_intx4,
    &raid6_intx8,
    NULL
};

void (*raid6_2data_recov)(int, size_t, int, int, void **);
EXPORT_SYMBOL_GPL(raid6_2data_recov);

void (*raid6_datap_recov)(int, size_t, int, void **);
EXPORT_SYMBOL_GPL(raid6_datap_recov);

const struct raid6_recov_calls *const raid6_recov_algos[] = {
#if (defined(__i386__) || defined(__x86_64__)) && !defined(__arch_um__)
    &raid6_recov_ssse3,
#endif
    &raid6_recov_intx1,
    NULL
};

#ifdef __KERNEL__
#define RAID6_TIME_JIFFIES_LG2  4
#else
/* Need more time to be stable in userspace */
#define RAID6_TIME_JIFFIES_LG2  9
#define time_before(x, y) ((x) < (y))
#endif

static inline const struct raid6_recov_calls *raid6_choose_recov(void)
{
    const struct raid6_recov_calls *const *algo;
    const struct raid6_recov_calls *best;

    for (best = NULL, algo = raid6_recov_algos; *algo; algo++)
        if (!best || (*algo)->priority > best->priority)
            if (!(*algo)->valid || (*algo)->valid())
                best = *algo;

    if (best) {
        raid6_2data_recov = best->data2;
        raid6_datap_recov = best->datap;

        printk("raid6: using %s recovery algorithm\n", best->name);
    } else
        printk("raid6: Yikes! No recovery algorithm found!\n");

    return best;
}

static inline const struct raid6_calls *raid6_choose_gen(
    void *(*const dptrs)[(65536/PAGE_SIZE)+2], const int disks)
{
    unsigned long perf, bestperf, j0, j1;
    const struct raid6_calls *const *algo;
    const struct raid6_calls *best;

    for (bestperf = 0, best = NULL, algo = raid6_algos; *algo; algo++) {
        if (!best || (*algo)->prefer >= best->prefer) {
            if ((*algo)->valid && !(*algo)->valid())
                continue;

            perf = 0;

            preempt_disable();
            j0 = jiffies;
            while ((j1 = jiffies) == j0)
                cpu_relax();
            while (time_before(jiffies,
                        j1 + (1<<RAID6_TIME_JIFFIES_LG2))) {
                (*algo)->gen_syndrome(disks, PAGE_SIZE, *dptrs);
                perf++;
            }
            preempt_enable();

            if (perf > bestperf) {
                bestperf = perf;
                best = *algo;
            }
            printk("raid6: %-8s %5ld MB/s\n", (*algo)->name,
                   (perf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
        }
    }

    if (best) {
        printk("raid6: using algorithm %s (%ld MB/s)\n",
               best->name,
               (bestperf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
        raid6_call = *best;
    } else
        printk("raid6: Yikes!  No algorithm found!\n");

    return best;
}


/* Try to pick the best algorithm */
/* This code uses the gfmul table as convenient data set to abuse */

int __init raid6_select_algo(void)
{
    const int disks = (65536/PAGE_SIZE)+2;

    const struct raid6_calls *gen_best;
    const struct raid6_recov_calls *rec_best;
    char *syndromes;
    void *dptrs[(65536/PAGE_SIZE)+2];
    int i;

    for (i = 0; i < disks-2; i++)
        dptrs[i] = ((char *)raid6_gfmul) + PAGE_SIZE*i;

    /* Normal code - use a 2-page allocation to avoid D$ conflict */
    syndromes = (void *) __get_free_pages(GFP_KERNEL, 1);

    if (!syndromes) {
        printk("raid6: Yikes!  No memory available.\n");
        return -ENOMEM;
    }

    dptrs[disks-2] = syndromes;
    dptrs[disks-1] = syndromes + PAGE_SIZE;

    /* select raid gen_syndrome function */
    gen_best = raid6_choose_gen(&dptrs, disks);

    /* select raid recover functions */
    rec_best = raid6_choose_recov();

    free_pages((unsigned long)syndromes, 1);

    return gen_best && rec_best ? 0 : -EINVAL;
}

static void raid6_exit(void)
{
    do { } while (0);
}

subsys_initcall(raid6_select_algo);
module_exit(raid6_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("RAID6 Q-syndrome calculations");