1 /* -*- linux-c -*- ------------------------------------------------------- *
3 * Copyright 2002 H. Peter Anvin - All Rights Reserved
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation, Inc., 53 Temple Place Ste 330,
8 * Boston MA 02111-1307, USA; either version 2 of the License, or
9 * (at your option) any later version; incorporated herein by reference.
11 * ----------------------------------------------------------------------- */
16 * Algorithm list and algorithm selection for RAID-6
19 #include <linux/raid/pq.h>
24 #include <linux/module.h>
25 #include <linux/gfp.h>
26 #if !RAID6_USE_EMPTY_ZERO_PAGE
27 /* In .bss so it's zeroed */
28 const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
29 EXPORT_SYMBOL(raid6_empty_zero_page);
33 struct raid6_calls raid6_call;
34 EXPORT_SYMBOL_GPL(raid6_call);
36 const struct raid6_calls * const raid6_algos[] = {
41 #if defined(__i386__) && !defined(__arch_um__)
49 #if defined(__x86_64__) && !defined(__arch_um__)
67 void (*raid6_2data_recov)(int, size_t, int, int, void **);
68 EXPORT_SYMBOL_GPL(raid6_2data_recov);
70 void (*raid6_datap_recov)(int, size_t, int, void **);
71 EXPORT_SYMBOL_GPL(raid6_datap_recov);
73 const struct raid6_recov_calls *const raid6_recov_algos[] = {
74 #if (defined(__i386__) || defined(__x86_64__)) && !defined(__arch_um__)
82 #define RAID6_TIME_JIFFIES_LG2 4
84 /* Need more time to be stable in userspace */
85 #define RAID6_TIME_JIFFIES_LG2 9
86 #define time_before(x, y) ((x) < (y))
89 static inline const struct raid6_recov_calls *raid6_choose_recov(void)
91 const struct raid6_recov_calls *const *algo;
92 const struct raid6_recov_calls *best;
94 for (best = NULL, algo = raid6_recov_algos; *algo; algo++)
95 if (!best || (*algo)->priority > best->priority)
96 if (!(*algo)->valid || (*algo)->valid())
100 raid6_2data_recov = best->data2;
101 raid6_datap_recov = best->datap;
103 printk("raid6: using %s recovery algorithm\n", best->name);
105 printk("raid6: Yikes! No recovery algorithm found!\n");
110 static inline const struct raid6_calls *raid6_choose_gen(
111 void *(*const dptrs)[(65536/PAGE_SIZE)+2], const int disks)
113 unsigned long perf, bestperf, j0, j1;
114 const struct raid6_calls *const *algo;
115 const struct raid6_calls *best;
117 for (bestperf = 0, best = NULL, algo = raid6_algos; *algo; algo++) {
118 if (!best || (*algo)->prefer >= best->prefer) {
119 if ((*algo)->valid && !(*algo)->valid())
126 while ((j1 = jiffies) == j0)
128 while (time_before(jiffies,
129 j1 + (1<<RAID6_TIME_JIFFIES_LG2))) {
130 (*algo)->gen_syndrome(disks, PAGE_SIZE, *dptrs);
135 if (perf > bestperf) {
139 printk("raid6: %-8s %5ld MB/s\n", (*algo)->name,
140 (perf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
145 printk("raid6: using algorithm %s (%ld MB/s)\n",
147 (bestperf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
150 printk("raid6: Yikes! No algorithm found!\n");
156 /* Try to pick the best algorithm */
157 /* This code uses the gfmul table as convenient data set to abuse */
159 int __init raid6_select_algo(void)
161 const int disks = (65536/PAGE_SIZE)+2;
163 const struct raid6_calls *gen_best;
164 const struct raid6_recov_calls *rec_best;
166 void *dptrs[(65536/PAGE_SIZE)+2];
169 for (i = 0; i < disks-2; i++)
170 dptrs[i] = ((char *)raid6_gfmul) + PAGE_SIZE*i;
172 /* Normal code - use a 2-page allocation to avoid D$ conflict */
173 syndromes = (void *) __get_free_pages(GFP_KERNEL, 1);
176 printk("raid6: Yikes! No memory available.\n");
180 dptrs[disks-2] = syndromes;
181 dptrs[disks-1] = syndromes + PAGE_SIZE;
183 /* select raid gen_syndrome function */
184 gen_best = raid6_choose_gen(&dptrs, disks);
186 /* select raid recover functions */
187 rec_best = raid6_choose_recov();
189 free_pages((unsigned long)syndromes, 1);
191 return gen_best && rec_best ? 0 : -EINVAL;
194 static void raid6_exit(void)
199 subsys_initcall(raid6_select_algo);
200 module_exit(raid6_exit);
201 MODULE_LICENSE("GPL");
202 MODULE_DESCRIPTION("RAID6 Q-syndrome calculations");