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Diffstat (limited to 'lib/raid/raid6/algos.c')
| -rw-r--r-- | lib/raid/raid6/algos.c | 377 |
1 files changed, 377 insertions, 0 deletions
diff --git a/lib/raid/raid6/algos.c b/lib/raid/raid6/algos.c new file mode 100644 index 000000000..6f5c89ab2 --- /dev/null +++ b/lib/raid/raid6/algos.c @@ -0,0 +1,377 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright 2002 H. Peter Anvin - All Rights Reserved + * + * Algorithm list and algorithm selection for RAID-6 + */ + +#include <linux/module.h> +#include <linux/gfp.h> +#include <linux/raid/pq.h> +#include <linux/slab.h> +#include <linux/static_call.h> +#include <kunit/visibility.h> +#include "algos.h" + +#define RAID6_MAX_ALGOS 16 +static const struct raid6_calls *raid6_algos[RAID6_MAX_ALGOS]; +static unsigned int raid6_nr_algos; +static const struct raid6_recov_calls *raid6_recov_algo; + +/* Selected algorithm */ +DEFINE_STATIC_CALL_NULL(raid6_gen_syndrome_impl, *raid6_intx1.gen_syndrome); +DEFINE_STATIC_CALL_NULL(raid6_xor_syndrome_impl, *raid6_intx1.xor_syndrome); +DEFINE_STATIC_CALL_NULL(raid6_recov_2data_impl, *raid6_recov_intx1.data2); +DEFINE_STATIC_CALL_NULL(raid6_recov_datap_impl, *raid6_recov_intx1.datap); + +/** + * raid6_gen_syndrome - generate RAID6 P/Q parity + * @disks: number of "disks" to operate on including parity + * @bytes: length in bytes of each vector + * @ptrs: @disks size array of memory pointers + * + * Generate @bytes worth of RAID6 P and Q parity in @ptrs[@disks - 2] and + * @ptrs[@disks - 1] respectively from the memory pointed to by @ptrs[0] to + * @ptrs[@disks - 3]. + * + * @disks must be at least 4, and the memory pointed to by each member of @ptrs + * must be at least 64-byte aligned. @bytes must be non-zero and a multiple of + * 512. + * + * See https://kernel.org/pub/linux/kernel/people/hpa/raid6.pdf for underlying + * algorithm. + */ +void raid6_gen_syndrome(int disks, size_t bytes, void **ptrs) +{ + WARN_ON_ONCE(!in_task() || irqs_disabled() || softirq_count()); + WARN_ON_ONCE(bytes & 511); + WARN_ON_ONCE(disks < RAID6_MIN_DISKS); + + static_call(raid6_gen_syndrome_impl)(disks, bytes, ptrs); +} +EXPORT_SYMBOL_GPL(raid6_gen_syndrome); + +/** + * raid6_xor_syndrome - update RAID6 P/Q parity + * @disks: number of "disks" to operate on including parity + * @start: first index into @disk to update + * @stop: last index into @disk to update + * @bytes: length in bytes of each vector + * @ptrs: @disks size array of memory pointers + * + * Update @bytes worth of RAID6 P and Q parity in @ptrs[@disks - 2] and + * @ptrs[@disks - 1] respectively for the memory pointed to by + * @ptrs[@start..@stop]. + * + * This is used to update parity in place using the following sequence: + * + * 1) call raid6_xor_syndrome(disk, start, stop, ...) for the existing data. + * 2) update the the data in @ptrs[@start..@stop]. + * 3) call raid6_xor_syndrome(disk, start, stop, ...) for the new data. + * + * Data between @start and @stop that is not changed should be filled + * with a pointer to the kernel zero page. + * + * @disks must be at least 4, and the memory pointed to by each member of @ptrs + * must be at least 64-byte aligned. @bytes must be non-zero and a multiple of + * 512. @stop must be larger or equal to @start. + */ +void raid6_xor_syndrome(int disks, int start, int stop, size_t bytes, + void **ptrs) +{ + WARN_ON_ONCE(!in_task() || irqs_disabled() || softirq_count()); + WARN_ON_ONCE(bytes & 511); + WARN_ON_ONCE(disks < RAID6_MIN_DISKS); + WARN_ON_ONCE(stop < start); + + static_call(raid6_xor_syndrome_impl)(disks, start, stop, bytes, ptrs); +} +EXPORT_SYMBOL_GPL(raid6_xor_syndrome); + +/* + * raid6_can_xor_syndrome - check if raid6_xor_syndrome() can be used + * + * Returns %true if raid6_can_xor_syndrome() can be used, else %false. + */ +bool raid6_can_xor_syndrome(void) +{ + return !!static_call_query(raid6_xor_syndrome_impl); +} +EXPORT_SYMBOL_GPL(raid6_can_xor_syndrome); + +/** + * raid6_recov_2data - recover two missing data disks + * @disks: number of "disks" to operate on including parity + * @bytes: length in bytes of each vector + * @faila: first failed data disk index + * @failb: second failed data disk index + * @ptrs: @disks size array of memory pointers + * + * Rebuild @bytes of missing data in @ptrs[@faila] and @ptrs[@failb] from the + * data in the remaining disks and the two parities pointed to by the other + * indices between 0 and @disks - 1 in @ptrs. @disks includes the data disks + * and the two parities. @faila must be smaller than @failb. + * + * Memory pointed to by each pointer in @ptrs must be page aligned and is + * limited to %PAGE_SIZE. + */ +void raid6_recov_2data(int disks, size_t bytes, int faila, int failb, + void **ptrs) +{ + WARN_ON_ONCE(!in_task() || irqs_disabled() || softirq_count()); + WARN_ON_ONCE(bytes & 511); + WARN_ON_ONCE(bytes > PAGE_SIZE); + WARN_ON_ONCE(failb <= faila); + + static_call(raid6_recov_2data_impl)(disks, bytes, faila, failb, ptrs); +} +EXPORT_SYMBOL_GPL(raid6_recov_2data); + +/** + * raid6_recov_datap - recover a missing data disk and missing P-parity + * @disks: number of "disks" to operate on including parity + * @bytes: length in bytes of each vector + * @faila: failed data disk index + * @ptrs: @disks size array of memory pointers + * + * Rebuild @bytes of missing data in @ptrs[@faila] and the missing P-parity in + * @ptrs[@disks - 2] from the data in the remaining disks and the Q-parity + * pointed to by the other indices between 0 and @disks - 1 in @ptrs. @disks + * includes the data disks and the two parities. + * + * Memory pointed to by each pointer in @ptrs must be page aligned and is + * limited to %PAGE_SIZE. + */ +void raid6_recov_datap(int disks, size_t bytes, int faila, void **ptrs) +{ + WARN_ON_ONCE(!in_task() || irqs_disabled() || softirq_count()); + WARN_ON_ONCE(bytes & 511); + WARN_ON_ONCE(bytes > PAGE_SIZE); + + static_call(raid6_recov_datap_impl)(disks, bytes, faila, ptrs); +} +EXPORT_SYMBOL_GPL(raid6_recov_datap); + +#define RAID6_TIME_JIFFIES_LG2 4 +#define RAID6_TEST_DISKS 8 + +static int raid6_choose_gen(void *(*const dptrs)[RAID6_TEST_DISKS], + const int disks) +{ + /* work on the second half of the disks */ + int start = (disks >> 1) - 1, stop = disks - 3; + const struct raid6_calls *best = NULL; + unsigned long bestgenperf = 0; + unsigned int i; + + for (i = 0; i < raid6_nr_algos; i++) { + const struct raid6_calls *algo = raid6_algos[i]; + unsigned long perf = 0, j0, j1; + + 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"); + return -EINVAL; + } + + static_call_update(raid6_gen_syndrome_impl, best->gen_syndrome); + static_call_update(raid6_xor_syndrome_impl, best->xor_syndrome); + + 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) { + unsigned long perf = 0, j0, j1; + + 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)); + } + + return 0; +} + + +/* Try to pick the best algorithm */ +/* This code uses the gfmul table as convenient data set to abuse */ + +static int __init raid6_select_algo(void) +{ + const int disks = RAID6_TEST_DISKS; + char *disk_ptr, *p; + void *dptrs[RAID6_TEST_DISKS]; + int i, cycle; + int error; + + if (!IS_ENABLED(CONFIG_RAID6_PQ_BENCHMARK) || raid6_nr_algos == 1) { + pr_info("raid6: skipped pq benchmark and selected %s\n", + raid6_algos[raid6_nr_algos - 1]->name); + static_call_update(raid6_gen_syndrome_impl, + raid6_algos[raid6_nr_algos - 1]->gen_syndrome); + static_call_update(raid6_xor_syndrome_impl, + raid6_algos[raid6_nr_algos - 1]->xor_syndrome); + return 0; + } + + /* prepare the buffer and fill it circularly with gfmul table */ + disk_ptr = kmalloc(PAGE_SIZE * RAID6_TEST_DISKS, GFP_KERNEL); + 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 */ + error = raid6_choose_gen(&dptrs, disks); + + kfree(disk_ptr); + + return error; +} + +/* + * Register a RAID6 P/Q generation algorithm. The most optimized/unrolled + * implementation should be registered last so it will be selected when the + * boot-time benchmark is disabled. + */ +void __init raid6_algo_add(const struct raid6_calls *algo) +{ + if (WARN_ON_ONCE(raid6_nr_algos == RAID6_MAX_ALGOS)) + return; + raid6_algos[raid6_nr_algos++] = algo; +} + +void __init raid6_algo_add_default(void) +{ + raid6_algo_add(&raid6_intx1); + raid6_algo_add(&raid6_intx2); + raid6_algo_add(&raid6_intx4); + raid6_algo_add(&raid6_intx8); +} + +void __init raid6_recov_algo_add(const struct raid6_recov_calls *algo) +{ + if (WARN_ON_ONCE(raid6_recov_algo)) + return; + raid6_recov_algo = algo; +} + +#ifdef CONFIG_RAID6_PQ_ARCH +#include "pq_arch.h" +#else +static inline void arch_raid6_init(void) +{ + raid6_algo_add_default(); +} +#endif /* CONFIG_RAID6_PQ_ARCH */ + +static int __init raid6_init(void) +{ + /* + * Architectures providing arch_raid6_init must add all PQ generation + * algorithms they want to consider in arch_raid6_init(), including + * the generic ones using raid6_algo_add_default() if wanted. + */ + arch_raid6_init(); + + /* + * Architectures don't have to set a recovery algorithm, we'll just pick + * the generic integer one if none was set. + */ + if (!raid6_recov_algo) + raid6_recov_algo = &raid6_recov_intx1; + static_call_update(raid6_recov_2data_impl, raid6_recov_algo->data2); + static_call_update(raid6_recov_datap_impl, raid6_recov_algo->datap); + pr_info("raid6: using %s recovery algorithm\n", raid6_recov_algo->name); + + return raid6_select_algo(); +} + +static void __exit raid6_exit(void) +{ +} + +subsys_initcall(raid6_init); +module_exit(raid6_exit); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("RAID6 Q-syndrome calculations"); + +#if IS_ENABLED(CONFIG_RAID6_PQ_KUNIT_TEST) +const struct raid6_calls *raid6_algo_find(unsigned int idx) +{ + if (idx >= raid6_nr_algos) { + /* + * Always include the simplest generic integer implementation in + * the unit tests as a baseline. + */ + if (idx == raid6_nr_algos && + raid6_algos[0] != &raid6_intx1) + return &raid6_intx1; + return NULL; + } + return raid6_algos[idx]; +} +EXPORT_SYMBOL_IF_KUNIT(raid6_algo_find); + +const struct raid6_recov_calls *raid6_recov_algo_find(unsigned int idx) +{ + switch (idx) { + case 0: + /* always test the generic integer implementation */ + return &raid6_recov_intx1; + case 1: + /* test the optimized implementation if there is one */ + if (raid6_recov_algo != &raid6_recov_intx1) + return raid6_recov_algo; + return NULL; + default: + return NULL; + } +} +EXPORT_SYMBOL_IF_KUNIT(raid6_recov_algo_find); +#endif /* CONFIG_RAID6_PQ_KUNIT_TEST */ |