root/lib/raid6/algos.c
// SPDX-License-Identifier: GPL-2.0-or-later
/* -*- linux-c -*- ------------------------------------------------------- *
 *
 *   Copyright 2002 H. Peter Anvin - All Rights Reserved
 *
 * ----------------------------------------------------------------------- */

/*
 * 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>
#endif

struct raid6_calls raid6_call;
EXPORT_SYMBOL_GPL(raid6_call);

const struct raid6_calls * const raid6_algos[] = {
#if defined(__i386__) && !defined(__arch_um__)
        &raid6_avx512x2,
        &raid6_avx512x1,
        &raid6_avx2x2,
        &raid6_avx2x1,
        &raid6_sse2x2,
        &raid6_sse2x1,
        &raid6_sse1x2,
        &raid6_sse1x1,
        &raid6_mmxx2,
        &raid6_mmxx1,
#endif
#if defined(__x86_64__) && !defined(__arch_um__)
        &raid6_avx512x4,
        &raid6_avx512x2,
        &raid6_avx512x1,
        &raid6_avx2x4,
        &raid6_avx2x2,
        &raid6_avx2x1,
        &raid6_sse2x4,
        &raid6_sse2x2,
        &raid6_sse2x1,
#endif
#ifdef CONFIG_ALTIVEC
        &raid6_vpermxor8,
        &raid6_vpermxor4,
        &raid6_vpermxor2,
        &raid6_vpermxor1,
        &raid6_altivec8,
        &raid6_altivec4,
        &raid6_altivec2,
        &raid6_altivec1,
#endif
#if defined(CONFIG_S390)
        &raid6_s390vx8,
#endif
#ifdef CONFIG_KERNEL_MODE_NEON
        &raid6_neonx8,
        &raid6_neonx4,
        &raid6_neonx2,
        &raid6_neonx1,
#endif
#ifdef CONFIG_LOONGARCH
#ifdef CONFIG_CPU_HAS_LASX
        &raid6_lasx,
#endif
#ifdef CONFIG_CPU_HAS_LSX
        &raid6_lsx,
#endif
#endif
#ifdef CONFIG_RISCV_ISA_V
        &raid6_rvvx1,
        &raid6_rvvx2,
        &raid6_rvvx4,
        &raid6_rvvx8,
#endif
        &raid6_intx8,
        &raid6_intx4,
        &raid6_intx2,
        &raid6_intx1,
        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[] = {
#ifdef CONFIG_X86
        &raid6_recov_avx512,
        &raid6_recov_avx2,
        &raid6_recov_ssse3,
#endif
#ifdef CONFIG_S390
        &raid6_recov_s390xc,
#endif
#if defined(CONFIG_KERNEL_MODE_NEON)
        &raid6_recov_neon,
#endif
#ifdef CONFIG_LOONGARCH
#ifdef CONFIG_CPU_HAS_LASX
        &raid6_recov_lasx,
#endif
#ifdef CONFIG_CPU_HAS_LSX
        &raid6_recov_lsx,
#endif
#endif
#ifdef CONFIG_RISCV_ISA_V
        &raid6_recov_rvv,
#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

#define RAID6_TEST_DISKS        8
#define RAID6_TEST_DISKS_ORDER  3

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;

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

        return best;
}

static inline const struct raid6_calls *raid6_choose_gen(
        void *(*const dptrs)[RAID6_TEST_DISKS], const int disks)
{
        unsigned long perf, bestgenperf, j0, j1;
        int start = (disks>>1)-1, stop = disks-3;       /* work on the second half of the disks */
        const struct raid6_calls *const *algo;
        const struct raid6_calls *best;

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

                        if (!IS_ENABLED(CONFIG_RAID6_PQ_BENCHMARK)) {
                                best = *algo;
                                break;
                        }

                        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 > bestgenperf) {
                                bestgenperf = perf;
                                best = *algo;
                        }
                        pr_info("raid6: %-8s gen() %5ld MB/s\n", (*algo)->name,
                                (perf * HZ * (disks-2)) >>
                                (20 - PAGE_SHIFT + RAID6_TIME_JIFFIES_LG2));
                }
        }

        if (!best) {
                pr_err("raid6: Yikes! No algorithm found!\n");
                goto out;
        }

        raid6_call = *best;

        if (!IS_ENABLED(CONFIG_RAID6_PQ_BENCHMARK)) {
                pr_info("raid6: skipped pq benchmark and selected %s\n",
                        best->name);
                goto out;
        }

        pr_info("raid6: using algorithm %s gen() %ld MB/s\n",
                best->name,
                (bestgenperf * HZ * (disks - 2)) >>
                (20 - PAGE_SHIFT + RAID6_TIME_JIFFIES_LG2));

        if (best->xor_syndrome) {
                perf = 0;

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

                pr_info("raid6: .... xor() %ld MB/s, rmw enabled\n",
                        (perf * HZ * (disks - 2)) >>
                        (20 - PAGE_SHIFT + RAID6_TIME_JIFFIES_LG2 + 1));
        }

out:
        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 = RAID6_TEST_DISKS;

        const struct raid6_calls *gen_best;
        const struct raid6_recov_calls *rec_best;
        char *disk_ptr, *p;
        void *dptrs[RAID6_TEST_DISKS];
        int i, cycle;

        /* prepare the buffer and fill it circularly with gfmul table */
        disk_ptr = (char *)__get_free_pages(GFP_KERNEL, RAID6_TEST_DISKS_ORDER);
        if (!disk_ptr) {
                pr_err("raid6: Yikes!  No memory available.\n");
                return -ENOMEM;
        }

        p = disk_ptr;
        for (i = 0; i < disks; i++)
                dptrs[i] = p + PAGE_SIZE * i;

        cycle = ((disks - 2) * PAGE_SIZE) / 65536;
        for (i = 0; i < cycle; i++) {
                memcpy(p, raid6_gfmul, 65536);
                p += 65536;
        }

        if ((disks - 2) * PAGE_SIZE % 65536)
                memcpy(p, raid6_gfmul, (disks - 2) * PAGE_SIZE % 65536);

        /* 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)disk_ptr, RAID6_TEST_DISKS_ORDER);

        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");