xref: /freebsd/sys/contrib/openzfs/module/zfs/vdev_raidz_math.c (revision 657729a89dd578d8cfc70d6616f5c65a48a8b33a)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or https://opensource.org/licenses/CDDL-1.0.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 /*
22  * Copyright (C) 2016 Gvozden Nešković. All rights reserved.
23  */
24 
25 #include <sys/zfs_context.h>
26 #include <sys/types.h>
27 #include <sys/zio.h>
28 #include <sys/debug.h>
29 #include <sys/zfs_debug.h>
30 #include <sys/vdev_raidz.h>
31 #include <sys/vdev_raidz_impl.h>
32 #include <sys/simd.h>
33 
34 /* Opaque implementation with NULL methods to represent original methods */
35 static const raidz_impl_ops_t vdev_raidz_original_impl = {
36 	.name = "original",
37 	.is_supported = raidz_will_scalar_work,
38 };
39 
40 /* RAIDZ parity op that contain the fastest methods */
41 static raidz_impl_ops_t vdev_raidz_fastest_impl = {
42 	.name = "fastest"
43 };
44 
45 /* All compiled in implementations */
46 static const raidz_impl_ops_t *const raidz_all_maths[] = {
47 	&vdev_raidz_original_impl,
48 	&vdev_raidz_scalar_impl,
49 #if defined(__x86_64) && defined(HAVE_SSE2)	/* only x86_64 for now */
50 	&vdev_raidz_sse2_impl,
51 #endif
52 #if defined(__x86_64) && defined(HAVE_SSSE3)	/* only x86_64 for now */
53 	&vdev_raidz_ssse3_impl,
54 #endif
55 #if defined(__x86_64) && defined(HAVE_AVX2)	/* only x86_64 for now */
56 	&vdev_raidz_avx2_impl,
57 #endif
58 #if defined(__x86_64) && defined(HAVE_AVX512F)	/* only x86_64 for now */
59 	&vdev_raidz_avx512f_impl,
60 #endif
61 #if defined(__x86_64) && defined(HAVE_AVX512BW)	/* only x86_64 for now */
62 	&vdev_raidz_avx512bw_impl,
63 #endif
64 #if defined(__aarch64__) && !defined(__FreeBSD__)
65 	&vdev_raidz_aarch64_neon_impl,
66 	&vdev_raidz_aarch64_neonx2_impl,
67 #endif
68 #if defined(__powerpc__) && defined(__altivec__)
69 	&vdev_raidz_powerpc_altivec_impl,
70 #endif
71 };
72 
73 /* Indicate that benchmark has been completed */
74 static boolean_t raidz_math_initialized = B_FALSE;
75 
76 /* Select raidz implementation */
77 #define	IMPL_FASTEST	(UINT32_MAX)
78 #define	IMPL_CYCLE	(UINT32_MAX - 1)
79 #define	IMPL_ORIGINAL	(0)
80 #define	IMPL_SCALAR	(1)
81 
82 #define	RAIDZ_IMPL_READ(i)	(*(volatile uint32_t *) &(i))
83 
84 static uint32_t zfs_vdev_raidz_impl = IMPL_SCALAR;
85 static uint32_t user_sel_impl = IMPL_FASTEST;
86 
87 /* Hold all supported implementations */
88 static size_t raidz_supp_impl_cnt = 0;
89 static raidz_impl_ops_t *raidz_supp_impl[ARRAY_SIZE(raidz_all_maths)];
90 
91 #if defined(_KERNEL)
92 /*
93  * kstats values for supported implementations
94  * Values represent per disk throughput of 8 disk+parity raidz vdev [B/s]
95  */
96 static raidz_impl_kstat_t raidz_impl_kstats[ARRAY_SIZE(raidz_all_maths) + 1];
97 
98 /* kstat for benchmarked implementations */
99 static kstat_t *raidz_math_kstat = NULL;
100 #endif
101 
102 /*
103  * Returns the RAIDZ operations for raidz_map() parity calculations.   When
104  * a SIMD implementation is not allowed in the current context, then fallback
105  * to the fastest generic implementation.
106  */
107 const raidz_impl_ops_t *
108 vdev_raidz_math_get_ops(void)
109 {
110 	if (!kfpu_allowed())
111 		return (&vdev_raidz_scalar_impl);
112 
113 	raidz_impl_ops_t *ops = NULL;
114 	const uint32_t impl = RAIDZ_IMPL_READ(zfs_vdev_raidz_impl);
115 
116 	switch (impl) {
117 	case IMPL_FASTEST:
118 		ASSERT(raidz_math_initialized);
119 		ops = &vdev_raidz_fastest_impl;
120 		break;
121 	case IMPL_CYCLE:
122 		/* Cycle through all supported implementations */
123 		ASSERT(raidz_math_initialized);
124 		ASSERT3U(raidz_supp_impl_cnt, >, 0);
125 		static size_t cycle_impl_idx = 0;
126 		size_t idx = (++cycle_impl_idx) % raidz_supp_impl_cnt;
127 		ops = raidz_supp_impl[idx];
128 		break;
129 	case IMPL_ORIGINAL:
130 		ops = (raidz_impl_ops_t *)&vdev_raidz_original_impl;
131 		break;
132 	case IMPL_SCALAR:
133 		ops = (raidz_impl_ops_t *)&vdev_raidz_scalar_impl;
134 		break;
135 	default:
136 		ASSERT3U(impl, <, raidz_supp_impl_cnt);
137 		ASSERT3U(raidz_supp_impl_cnt, >, 0);
138 		if (impl < ARRAY_SIZE(raidz_all_maths))
139 			ops = raidz_supp_impl[impl];
140 		break;
141 	}
142 
143 	ASSERT3P(ops, !=, NULL);
144 
145 	return (ops);
146 }
147 
148 /*
149  * Select parity generation method for raidz_map
150  */
151 int
152 vdev_raidz_math_generate(raidz_map_t *rm, raidz_row_t *rr)
153 {
154 	raidz_gen_f gen_parity = NULL;
155 
156 	switch (raidz_parity(rm)) {
157 		case 1:
158 			gen_parity = rm->rm_ops->gen[RAIDZ_GEN_P];
159 			break;
160 		case 2:
161 			gen_parity = rm->rm_ops->gen[RAIDZ_GEN_PQ];
162 			break;
163 		case 3:
164 			gen_parity = rm->rm_ops->gen[RAIDZ_GEN_PQR];
165 			break;
166 		default:
167 			gen_parity = NULL;
168 			cmn_err(CE_PANIC, "invalid RAID-Z configuration %llu",
169 			    (u_longlong_t)raidz_parity(rm));
170 			break;
171 	}
172 
173 	/* if method is NULL execute the original implementation */
174 	if (gen_parity == NULL)
175 		return (RAIDZ_ORIGINAL_IMPL);
176 
177 	gen_parity(rr);
178 
179 	return (0);
180 }
181 
182 static raidz_rec_f
183 reconstruct_fun_p_sel(raidz_map_t *rm, const int *parity_valid,
184     const int nbaddata)
185 {
186 	if (nbaddata == 1 && parity_valid[CODE_P]) {
187 		return (rm->rm_ops->rec[RAIDZ_REC_P]);
188 	}
189 	return ((raidz_rec_f) NULL);
190 }
191 
192 static raidz_rec_f
193 reconstruct_fun_pq_sel(raidz_map_t *rm, const int *parity_valid,
194     const int nbaddata)
195 {
196 	if (nbaddata == 1) {
197 		if (parity_valid[CODE_P]) {
198 			return (rm->rm_ops->rec[RAIDZ_REC_P]);
199 		} else if (parity_valid[CODE_Q]) {
200 			return (rm->rm_ops->rec[RAIDZ_REC_Q]);
201 		}
202 	} else if (nbaddata == 2 &&
203 	    parity_valid[CODE_P] && parity_valid[CODE_Q]) {
204 		return (rm->rm_ops->rec[RAIDZ_REC_PQ]);
205 	}
206 	return ((raidz_rec_f) NULL);
207 }
208 
209 static raidz_rec_f
210 reconstruct_fun_pqr_sel(raidz_map_t *rm, const int *parity_valid,
211     const int nbaddata)
212 {
213 	if (nbaddata == 1) {
214 		if (parity_valid[CODE_P]) {
215 			return (rm->rm_ops->rec[RAIDZ_REC_P]);
216 		} else if (parity_valid[CODE_Q]) {
217 			return (rm->rm_ops->rec[RAIDZ_REC_Q]);
218 		} else if (parity_valid[CODE_R]) {
219 			return (rm->rm_ops->rec[RAIDZ_REC_R]);
220 		}
221 	} else if (nbaddata == 2) {
222 		if (parity_valid[CODE_P] && parity_valid[CODE_Q]) {
223 			return (rm->rm_ops->rec[RAIDZ_REC_PQ]);
224 		} else if (parity_valid[CODE_P] && parity_valid[CODE_R]) {
225 			return (rm->rm_ops->rec[RAIDZ_REC_PR]);
226 		} else if (parity_valid[CODE_Q] && parity_valid[CODE_R]) {
227 			return (rm->rm_ops->rec[RAIDZ_REC_QR]);
228 		}
229 	} else if (nbaddata == 3 &&
230 	    parity_valid[CODE_P] && parity_valid[CODE_Q] &&
231 	    parity_valid[CODE_R]) {
232 		return (rm->rm_ops->rec[RAIDZ_REC_PQR]);
233 	}
234 	return ((raidz_rec_f) NULL);
235 }
236 
237 /*
238  * Select data reconstruction method for raidz_map
239  * @parity_valid - Parity validity flag
240  * @dt           - Failed data index array
241  * @nbaddata     - Number of failed data columns
242  */
243 int
244 vdev_raidz_math_reconstruct(raidz_map_t *rm, raidz_row_t *rr,
245     const int *parity_valid, const int *dt, const int nbaddata)
246 {
247 	raidz_rec_f rec_fn = NULL;
248 
249 	switch (raidz_parity(rm)) {
250 	case PARITY_P:
251 		rec_fn = reconstruct_fun_p_sel(rm, parity_valid, nbaddata);
252 		break;
253 	case PARITY_PQ:
254 		rec_fn = reconstruct_fun_pq_sel(rm, parity_valid, nbaddata);
255 		break;
256 	case PARITY_PQR:
257 		rec_fn = reconstruct_fun_pqr_sel(rm, parity_valid, nbaddata);
258 		break;
259 	default:
260 		cmn_err(CE_PANIC, "invalid RAID-Z configuration %llu",
261 		    (u_longlong_t)raidz_parity(rm));
262 		break;
263 	}
264 
265 	if (rec_fn == NULL)
266 		return (RAIDZ_ORIGINAL_IMPL);
267 	else
268 		return (rec_fn(rr, dt));
269 }
270 
271 const char *const raidz_gen_name[] = {
272 	"gen_p", "gen_pq", "gen_pqr"
273 };
274 const char *const raidz_rec_name[] = {
275 	"rec_p", "rec_q", "rec_r",
276 	"rec_pq", "rec_pr", "rec_qr", "rec_pqr"
277 };
278 
279 #if defined(_KERNEL)
280 
281 #define	RAIDZ_KSTAT_LINE_LEN	(17 + 10*12 + 1)
282 
283 static int
284 raidz_math_kstat_headers(char *buf, size_t size)
285 {
286 	ASSERT3U(size, >=, RAIDZ_KSTAT_LINE_LEN);
287 
288 	ssize_t off = kmem_scnprintf(buf, size, "%-17s", "implementation");
289 
290 	for (int i = 0; i < ARRAY_SIZE(raidz_gen_name); i++)
291 		off += kmem_scnprintf(buf + off, size - off, "%-16s",
292 		    raidz_gen_name[i]);
293 
294 	for (int i = 0; i < ARRAY_SIZE(raidz_rec_name); i++)
295 		off += kmem_scnprintf(buf + off, size - off, "%-16s",
296 		    raidz_rec_name[i]);
297 
298 	(void) kmem_scnprintf(buf + off, size - off, "\n");
299 
300 	return (0);
301 }
302 
303 static int
304 raidz_math_kstat_data(char *buf, size_t size, void *data)
305 {
306 	raidz_impl_kstat_t *fstat = &raidz_impl_kstats[raidz_supp_impl_cnt];
307 	raidz_impl_kstat_t *cstat = (raidz_impl_kstat_t *)data;
308 	ssize_t off = 0;
309 	int i;
310 
311 	ASSERT3U(size, >=, RAIDZ_KSTAT_LINE_LEN);
312 
313 	if (cstat == fstat) {
314 		off += kmem_scnprintf(buf + off, size - off, "%-17s",
315 		    "fastest");
316 
317 		for (i = 0; i < ARRAY_SIZE(raidz_gen_name); i++) {
318 			int id = fstat->gen[i];
319 			off += kmem_scnprintf(buf + off, size - off, "%-16s",
320 			    raidz_supp_impl[id]->name);
321 		}
322 		for (i = 0; i < ARRAY_SIZE(raidz_rec_name); i++) {
323 			int id = fstat->rec[i];
324 			off += kmem_scnprintf(buf + off, size - off, "%-16s",
325 			    raidz_supp_impl[id]->name);
326 		}
327 	} else {
328 		ptrdiff_t id = cstat - raidz_impl_kstats;
329 
330 		off += kmem_scnprintf(buf + off, size - off, "%-17s",
331 		    raidz_supp_impl[id]->name);
332 
333 		for (i = 0; i < ARRAY_SIZE(raidz_gen_name); i++)
334 			off += kmem_scnprintf(buf + off, size - off, "%-16llu",
335 			    (u_longlong_t)cstat->gen[i]);
336 
337 		for (i = 0; i < ARRAY_SIZE(raidz_rec_name); i++)
338 			off += kmem_scnprintf(buf + off, size - off, "%-16llu",
339 			    (u_longlong_t)cstat->rec[i]);
340 	}
341 
342 	(void) kmem_scnprintf(buf + off, size - off, "\n");
343 
344 	return (0);
345 }
346 
347 static void *
348 raidz_math_kstat_addr(kstat_t *ksp, loff_t n)
349 {
350 	if (n <= raidz_supp_impl_cnt)
351 		ksp->ks_private = (void *) (raidz_impl_kstats + n);
352 	else
353 		ksp->ks_private = NULL;
354 
355 	return (ksp->ks_private);
356 }
357 
358 #define	BENCH_D_COLS	(8ULL)
359 #define	BENCH_COLS	(BENCH_D_COLS + PARITY_PQR)
360 #define	BENCH_ZIO_SIZE	(1ULL << SPA_OLD_MAXBLOCKSHIFT)	/* 128 kiB */
361 #define	BENCH_NS	MSEC2NSEC(1)			/* 1ms */
362 
363 typedef void (*benchmark_fn)(raidz_map_t *rm, const int fn);
364 
365 static void
366 benchmark_gen_impl(raidz_map_t *rm, const int fn)
367 {
368 	(void) fn;
369 	vdev_raidz_generate_parity(rm);
370 }
371 
372 static void
373 benchmark_rec_impl(raidz_map_t *rm, const int fn)
374 {
375 	static const int rec_tgt[7][3] = {
376 		{1, 2, 3},	/* rec_p:   bad QR & D[0]	*/
377 		{0, 2, 3},	/* rec_q:   bad PR & D[0]	*/
378 		{0, 1, 3},	/* rec_r:   bad PQ & D[0]	*/
379 		{2, 3, 4},	/* rec_pq:  bad R  & D[0][1]	*/
380 		{1, 3, 4},	/* rec_pr:  bad Q  & D[0][1]	*/
381 		{0, 3, 4},	/* rec_qr:  bad P  & D[0][1]	*/
382 		{3, 4, 5}	/* rec_pqr: bad    & D[0][1][2] */
383 	};
384 
385 	vdev_raidz_reconstruct(rm, rec_tgt[fn], 3);
386 }
387 
388 /*
389  * Benchmarking of all supported implementations (raidz_supp_impl_cnt)
390  * is performed by setting the rm_ops pointer and calling the top level
391  * generate/reconstruct methods of bench_rm.
392  */
393 static void
394 benchmark_raidz_impl(raidz_map_t *bench_rm, const int fn, benchmark_fn bench_fn)
395 {
396 	uint64_t run_cnt, speed, best_speed = 0;
397 	hrtime_t t_start, t_diff;
398 	raidz_impl_ops_t *curr_impl;
399 	raidz_impl_kstat_t *fstat = &raidz_impl_kstats[raidz_supp_impl_cnt];
400 	int impl, i;
401 
402 	for (impl = 0; impl < raidz_supp_impl_cnt; impl++) {
403 		/* set an implementation to benchmark */
404 		curr_impl = raidz_supp_impl[impl];
405 		bench_rm->rm_ops = curr_impl;
406 
407 		run_cnt = 0;
408 		t_start = gethrtime();
409 
410 		do {
411 			for (i = 0; i < 5; i++, run_cnt++)
412 				bench_fn(bench_rm, fn);
413 
414 			t_diff = gethrtime() - t_start;
415 		} while (t_diff < BENCH_NS);
416 
417 		speed = run_cnt * BENCH_ZIO_SIZE * NANOSEC;
418 		speed /= (t_diff * BENCH_COLS);
419 
420 		if (bench_fn == benchmark_gen_impl)
421 			raidz_impl_kstats[impl].gen[fn] = speed;
422 		else
423 			raidz_impl_kstats[impl].rec[fn] = speed;
424 
425 		/* Update fastest implementation method */
426 		if (speed > best_speed) {
427 			best_speed = speed;
428 
429 			if (bench_fn == benchmark_gen_impl) {
430 				fstat->gen[fn] = impl;
431 				vdev_raidz_fastest_impl.gen[fn] =
432 				    curr_impl->gen[fn];
433 			} else {
434 				fstat->rec[fn] = impl;
435 				vdev_raidz_fastest_impl.rec[fn] =
436 				    curr_impl->rec[fn];
437 			}
438 		}
439 	}
440 }
441 #endif
442 
443 /*
444  * Initialize and benchmark all supported implementations.
445  */
446 static void
447 benchmark_raidz(void)
448 {
449 	raidz_impl_ops_t *curr_impl;
450 	int i, c;
451 
452 	/* Move supported impl into raidz_supp_impl */
453 	for (i = 0, c = 0; i < ARRAY_SIZE(raidz_all_maths); i++) {
454 		curr_impl = (raidz_impl_ops_t *)raidz_all_maths[i];
455 
456 		if (curr_impl->init)
457 			curr_impl->init();
458 
459 		if (curr_impl->is_supported())
460 			raidz_supp_impl[c++] = (raidz_impl_ops_t *)curr_impl;
461 	}
462 	membar_producer();		/* complete raidz_supp_impl[] init */
463 	raidz_supp_impl_cnt = c;	/* number of supported impl */
464 
465 #if defined(_KERNEL)
466 	abd_t *pabd;
467 	zio_t *bench_zio = NULL;
468 	raidz_map_t *bench_rm = NULL;
469 	uint64_t bench_parity;
470 
471 	/* Fake a zio and run the benchmark on a warmed up buffer */
472 	bench_zio = kmem_zalloc(sizeof (zio_t), KM_SLEEP);
473 	bench_zio->io_offset = 0;
474 	bench_zio->io_size = BENCH_ZIO_SIZE; /* only data columns */
475 	bench_zio->io_abd = abd_alloc_linear(BENCH_ZIO_SIZE, B_TRUE);
476 	memset(abd_to_buf(bench_zio->io_abd), 0xAA, BENCH_ZIO_SIZE);
477 
478 	/* Benchmark parity generation methods */
479 	for (int fn = 0; fn < RAIDZ_GEN_NUM; fn++) {
480 		bench_parity = fn + 1;
481 		/* New raidz_map is needed for each generate_p/q/r */
482 		bench_rm = vdev_raidz_map_alloc(bench_zio, SPA_MINBLOCKSHIFT,
483 		    BENCH_D_COLS + bench_parity, bench_parity);
484 
485 		benchmark_raidz_impl(bench_rm, fn, benchmark_gen_impl);
486 
487 		vdev_raidz_map_free(bench_rm);
488 	}
489 
490 	/* Benchmark data reconstruction methods */
491 	bench_rm = vdev_raidz_map_alloc(bench_zio, SPA_MINBLOCKSHIFT,
492 	    BENCH_COLS, PARITY_PQR);
493 
494 	/* Ensure that fake parity blocks are initialized */
495 	for (c = 0; c < bench_rm->rm_row[0]->rr_firstdatacol; c++) {
496 		pabd = bench_rm->rm_row[0]->rr_col[c].rc_abd;
497 		memset(abd_to_buf(pabd), 0xAA, abd_get_size(pabd));
498 	}
499 
500 	for (int fn = 0; fn < RAIDZ_REC_NUM; fn++)
501 		benchmark_raidz_impl(bench_rm, fn, benchmark_rec_impl);
502 
503 	vdev_raidz_map_free(bench_rm);
504 
505 	/* cleanup the bench zio */
506 	abd_free(bench_zio->io_abd);
507 	kmem_free(bench_zio, sizeof (zio_t));
508 #else
509 	/*
510 	 * Skip the benchmark in user space to avoid impacting libzpool
511 	 * consumers (zdb, zhack, zinject, ztest).  The last implementation
512 	 * is assumed to be the fastest and used by default.
513 	 */
514 	memcpy(&vdev_raidz_fastest_impl,
515 	    raidz_supp_impl[raidz_supp_impl_cnt - 1],
516 	    sizeof (vdev_raidz_fastest_impl));
517 	strcpy(vdev_raidz_fastest_impl.name, "fastest");
518 #endif /* _KERNEL */
519 }
520 
521 void
522 vdev_raidz_math_init(void)
523 {
524 	/* Determine the fastest available implementation. */
525 	benchmark_raidz();
526 
527 #if defined(_KERNEL)
528 	/* Install kstats for all implementations */
529 	raidz_math_kstat = kstat_create("zfs", 0, "vdev_raidz_bench", "misc",
530 	    KSTAT_TYPE_RAW, 0, KSTAT_FLAG_VIRTUAL);
531 	if (raidz_math_kstat != NULL) {
532 		raidz_math_kstat->ks_data = NULL;
533 		raidz_math_kstat->ks_ndata = UINT32_MAX;
534 		kstat_set_raw_ops(raidz_math_kstat,
535 		    raidz_math_kstat_headers,
536 		    raidz_math_kstat_data,
537 		    raidz_math_kstat_addr);
538 		kstat_install(raidz_math_kstat);
539 	}
540 #endif
541 
542 	/* Finish initialization */
543 	atomic_swap_32(&zfs_vdev_raidz_impl, user_sel_impl);
544 	raidz_math_initialized = B_TRUE;
545 }
546 
547 void
548 vdev_raidz_math_fini(void)
549 {
550 	raidz_impl_ops_t const *curr_impl;
551 
552 #if defined(_KERNEL)
553 	if (raidz_math_kstat != NULL) {
554 		kstat_delete(raidz_math_kstat);
555 		raidz_math_kstat = NULL;
556 	}
557 #endif
558 
559 	for (int i = 0; i < ARRAY_SIZE(raidz_all_maths); i++) {
560 		curr_impl = raidz_all_maths[i];
561 		if (curr_impl->fini)
562 			curr_impl->fini();
563 	}
564 }
565 
566 static const struct {
567 	const char *name;
568 	uint32_t sel;
569 } math_impl_opts[] = {
570 		{ "cycle",	IMPL_CYCLE },
571 		{ "fastest",	IMPL_FASTEST },
572 		{ "original",	IMPL_ORIGINAL },
573 		{ "scalar",	IMPL_SCALAR }
574 };
575 
576 /*
577  * Function sets desired raidz implementation.
578  *
579  * If we are called before init(), user preference will be saved in
580  * user_sel_impl, and applied in later init() call. This occurs when module
581  * parameter is specified on module load. Otherwise, directly update
582  * zfs_vdev_raidz_impl.
583  *
584  * @val		Name of raidz implementation to use
585  * @param	Unused.
586  */
587 int
588 vdev_raidz_impl_set(const char *val)
589 {
590 	int err = -EINVAL;
591 	char req_name[RAIDZ_IMPL_NAME_MAX];
592 	uint32_t impl = RAIDZ_IMPL_READ(user_sel_impl);
593 	size_t i;
594 
595 	/* sanitize input */
596 	i = strnlen(val, RAIDZ_IMPL_NAME_MAX);
597 	if (i == 0 || i == RAIDZ_IMPL_NAME_MAX)
598 		return (err);
599 
600 	strlcpy(req_name, val, RAIDZ_IMPL_NAME_MAX);
601 	while (i > 0 && !!isspace(req_name[i-1]))
602 		i--;
603 	req_name[i] = '\0';
604 
605 	/* Check mandatory options */
606 	for (i = 0; i < ARRAY_SIZE(math_impl_opts); i++) {
607 		if (strcmp(req_name, math_impl_opts[i].name) == 0) {
608 			impl = math_impl_opts[i].sel;
609 			err = 0;
610 			break;
611 		}
612 	}
613 
614 	/* check all supported impl if init() was already called */
615 	if (err != 0 && raidz_math_initialized) {
616 		/* check all supported implementations */
617 		for (i = 0; i < raidz_supp_impl_cnt; i++) {
618 			if (strcmp(req_name, raidz_supp_impl[i]->name) == 0) {
619 				impl = i;
620 				err = 0;
621 				break;
622 			}
623 		}
624 	}
625 
626 	if (err == 0) {
627 		if (raidz_math_initialized)
628 			atomic_swap_32(&zfs_vdev_raidz_impl, impl);
629 		else
630 			atomic_swap_32(&user_sel_impl, impl);
631 	}
632 
633 	return (err);
634 }
635 
636 #if defined(_KERNEL) && defined(__linux__)
637 
638 static int
639 zfs_vdev_raidz_impl_set(const char *val, zfs_kernel_param_t *kp)
640 {
641 	return (vdev_raidz_impl_set(val));
642 }
643 
644 static int
645 zfs_vdev_raidz_impl_get(char *buffer, zfs_kernel_param_t *kp)
646 {
647 	int i, cnt = 0;
648 	char *fmt;
649 	const uint32_t impl = RAIDZ_IMPL_READ(zfs_vdev_raidz_impl);
650 
651 	ASSERT(raidz_math_initialized);
652 
653 	/* list mandatory options */
654 	for (i = 0; i < ARRAY_SIZE(math_impl_opts) - 2; i++) {
655 		fmt = (impl == math_impl_opts[i].sel) ? "[%s] " : "%s ";
656 		cnt += sprintf(buffer + cnt, fmt, math_impl_opts[i].name);
657 	}
658 
659 	/* list all supported implementations */
660 	for (i = 0; i < raidz_supp_impl_cnt; i++) {
661 		fmt = (i == impl) ? "[%s] " : "%s ";
662 		cnt += sprintf(buffer + cnt, fmt, raidz_supp_impl[i]->name);
663 	}
664 
665 	return (cnt);
666 }
667 
668 module_param_call(zfs_vdev_raidz_impl, zfs_vdev_raidz_impl_set,
669     zfs_vdev_raidz_impl_get, NULL, 0644);
670 MODULE_PARM_DESC(zfs_vdev_raidz_impl, "Select raidz implementation.");
671 #endif
672