xref: /illumos-gate/usr/src/uts/common/fs/zfs/vdev_mirror.c (revision cd11837edb943ce20ca539d505e60b469f89bf20)
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 http://www.opensolaris.org/os/licensing.
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 2008 Sun Microsystems, Inc.  All rights reserved.
23  * Use is subject to license terms.
24  */
25 
26 #include <sys/zfs_context.h>
27 #include <sys/spa.h>
28 #include <sys/vdev_impl.h>
29 #include <sys/zio.h>
30 #include <sys/fs/zfs.h>
31 
32 /*
33  * Virtual device vector for mirroring.
34  */
35 
36 typedef struct mirror_child {
37 	vdev_t		*mc_vd;
38 	uint64_t	mc_offset;
39 	int		mc_error;
40 	uint8_t		mc_tried;
41 	uint8_t		mc_skipped;
42 	uint8_t		mc_speculative;
43 } mirror_child_t;
44 
45 typedef struct mirror_map {
46 	int		mm_children;
47 	int		mm_replacing;
48 	int		mm_preferred;
49 	int		mm_root;
50 	mirror_child_t	mm_child[1];
51 } mirror_map_t;
52 
53 int vdev_mirror_shift = 21;
54 
55 static void
56 vdev_mirror_map_free(zio_t *zio)
57 {
58 	mirror_map_t *mm = zio->io_vsd;
59 
60 	kmem_free(mm, offsetof(mirror_map_t, mm_child[mm->mm_children]));
61 }
62 
63 static mirror_map_t *
64 vdev_mirror_map_alloc(zio_t *zio)
65 {
66 	mirror_map_t *mm = NULL;
67 	mirror_child_t *mc;
68 	vdev_t *vd = zio->io_vd;
69 	int c, d;
70 
71 	if (vd == NULL) {
72 		dva_t *dva = zio->io_bp->blk_dva;
73 		spa_t *spa = zio->io_spa;
74 
75 		c = BP_GET_NDVAS(zio->io_bp);
76 
77 		mm = kmem_zalloc(offsetof(mirror_map_t, mm_child[c]), KM_SLEEP);
78 		mm->mm_children = c;
79 		mm->mm_replacing = B_FALSE;
80 		mm->mm_preferred = spa_get_random(c);
81 		mm->mm_root = B_TRUE;
82 
83 		/*
84 		 * Check the other, lower-index DVAs to see if they're on
85 		 * the same vdev as the child we picked.  If they are, use
86 		 * them since they are likely to have been allocated from
87 		 * the primary metaslab in use at the time, and hence are
88 		 * more likely to have locality with single-copy data.
89 		 */
90 		for (c = mm->mm_preferred, d = c - 1; d >= 0; d--) {
91 			if (DVA_GET_VDEV(&dva[d]) == DVA_GET_VDEV(&dva[c]))
92 				mm->mm_preferred = d;
93 		}
94 
95 		for (c = 0; c < mm->mm_children; c++) {
96 			mc = &mm->mm_child[c];
97 
98 			mc->mc_vd = vdev_lookup_top(spa, DVA_GET_VDEV(&dva[c]));
99 			mc->mc_offset = DVA_GET_OFFSET(&dva[c]);
100 		}
101 	} else {
102 		c = vd->vdev_children;
103 
104 		mm = kmem_zalloc(offsetof(mirror_map_t, mm_child[c]), KM_SLEEP);
105 		mm->mm_children = c;
106 		mm->mm_replacing = (vd->vdev_ops == &vdev_replacing_ops ||
107 		    vd->vdev_ops == &vdev_spare_ops);
108 		mm->mm_preferred = mm->mm_replacing ? 0 :
109 		    (zio->io_offset >> vdev_mirror_shift) % c;
110 		mm->mm_root = B_FALSE;
111 
112 		for (c = 0; c < mm->mm_children; c++) {
113 			mc = &mm->mm_child[c];
114 			mc->mc_vd = vd->vdev_child[c];
115 			mc->mc_offset = zio->io_offset;
116 		}
117 	}
118 
119 	zio->io_vsd = mm;
120 	zio->io_vsd_free = vdev_mirror_map_free;
121 	return (mm);
122 }
123 
124 static int
125 vdev_mirror_open(vdev_t *vd, uint64_t *asize, uint64_t *ashift)
126 {
127 	vdev_t *cvd;
128 	uint64_t c;
129 	int numerrors = 0;
130 	int ret, lasterror = 0;
131 
132 	if (vd->vdev_children == 0) {
133 		vd->vdev_stat.vs_aux = VDEV_AUX_BAD_LABEL;
134 		return (EINVAL);
135 	}
136 
137 	for (c = 0; c < vd->vdev_children; c++) {
138 		cvd = vd->vdev_child[c];
139 
140 		if ((ret = vdev_open(cvd)) != 0) {
141 			lasterror = ret;
142 			numerrors++;
143 			continue;
144 		}
145 
146 		*asize = MIN(*asize - 1, cvd->vdev_asize - 1) + 1;
147 		*ashift = MAX(*ashift, cvd->vdev_ashift);
148 	}
149 
150 	if (numerrors == vd->vdev_children) {
151 		vd->vdev_stat.vs_aux = VDEV_AUX_NO_REPLICAS;
152 		return (lasterror);
153 	}
154 
155 	return (0);
156 }
157 
158 static void
159 vdev_mirror_close(vdev_t *vd)
160 {
161 	uint64_t c;
162 
163 	for (c = 0; c < vd->vdev_children; c++)
164 		vdev_close(vd->vdev_child[c]);
165 }
166 
167 static void
168 vdev_mirror_child_done(zio_t *zio)
169 {
170 	mirror_child_t *mc = zio->io_private;
171 
172 	mc->mc_error = zio->io_error;
173 	mc->mc_tried = 1;
174 	mc->mc_skipped = 0;
175 }
176 
177 static void
178 vdev_mirror_scrub_done(zio_t *zio)
179 {
180 	mirror_child_t *mc = zio->io_private;
181 
182 	if (zio->io_error == 0) {
183 		zio_t *pio = zio->io_parent;
184 		mutex_enter(&pio->io_lock);
185 		ASSERT3U(zio->io_size, >=, pio->io_size);
186 		bcopy(zio->io_data, pio->io_data, pio->io_size);
187 		mutex_exit(&pio->io_lock);
188 	}
189 
190 	zio_buf_free(zio->io_data, zio->io_size);
191 
192 	mc->mc_error = zio->io_error;
193 	mc->mc_tried = 1;
194 	mc->mc_skipped = 0;
195 }
196 
197 /*
198  * Try to find a child whose DTL doesn't contain the block we want to read.
199  * If we can't, try the read on any vdev we haven't already tried.
200  */
201 static int
202 vdev_mirror_child_select(zio_t *zio)
203 {
204 	mirror_map_t *mm = zio->io_vsd;
205 	mirror_child_t *mc;
206 	uint64_t txg = zio->io_txg;
207 	int i, c;
208 
209 	ASSERT(zio->io_bp == NULL || zio->io_bp->blk_birth == txg);
210 
211 	/*
212 	 * Try to find a child whose DTL doesn't contain the block to read.
213 	 * If a child is known to be completely inaccessible (indicated by
214 	 * vdev_readable() returning B_FALSE), don't even try.
215 	 */
216 	for (i = 0, c = mm->mm_preferred; i < mm->mm_children; i++, c++) {
217 		if (c >= mm->mm_children)
218 			c = 0;
219 		mc = &mm->mm_child[c];
220 		if (mc->mc_tried || mc->mc_skipped)
221 			continue;
222 		if (!vdev_readable(mc->mc_vd)) {
223 			mc->mc_error = ENXIO;
224 			mc->mc_tried = 1;	/* don't even try */
225 			mc->mc_skipped = 1;
226 			continue;
227 		}
228 		if (!vdev_dtl_contains(&mc->mc_vd->vdev_dtl_map, txg, 1))
229 			return (c);
230 		mc->mc_error = ESTALE;
231 		mc->mc_skipped = 1;
232 		mc->mc_speculative = 1;
233 	}
234 
235 	/*
236 	 * Every device is either missing or has this txg in its DTL.
237 	 * Look for any child we haven't already tried before giving up.
238 	 */
239 	for (c = 0; c < mm->mm_children; c++)
240 		if (!mm->mm_child[c].mc_tried)
241 			return (c);
242 
243 	/*
244 	 * Every child failed.  There's no place left to look.
245 	 */
246 	return (-1);
247 }
248 
249 static int
250 vdev_mirror_io_start(zio_t *zio)
251 {
252 	mirror_map_t *mm;
253 	mirror_child_t *mc;
254 	int c, children;
255 
256 	mm = vdev_mirror_map_alloc(zio);
257 
258 	if (zio->io_type == ZIO_TYPE_READ) {
259 		if ((zio->io_flags & ZIO_FLAG_SCRUB) && !mm->mm_replacing) {
260 			/*
261 			 * For scrubbing reads we need to allocate a read
262 			 * buffer for each child and issue reads to all
263 			 * children.  If any child succeeds, it will copy its
264 			 * data into zio->io_data in vdev_mirror_scrub_done.
265 			 */
266 			for (c = 0; c < mm->mm_children; c++) {
267 				mc = &mm->mm_child[c];
268 				zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
269 				    mc->mc_vd, mc->mc_offset,
270 				    zio_buf_alloc(zio->io_size), zio->io_size,
271 				    zio->io_type, zio->io_priority, 0,
272 				    vdev_mirror_scrub_done, mc));
273 			}
274 			return (ZIO_PIPELINE_CONTINUE);
275 		}
276 		/*
277 		 * For normal reads just pick one child.
278 		 */
279 		c = vdev_mirror_child_select(zio);
280 		children = (c >= 0);
281 	} else {
282 		ASSERT(zio->io_type == ZIO_TYPE_WRITE);
283 
284 		/*
285 		 * If this is a resilvering I/O to a replacing vdev,
286 		 * only the last child should be written -- unless the
287 		 * first child happens to have a DTL entry here as well.
288 		 * All other writes go to all children.
289 		 */
290 		if ((zio->io_flags & ZIO_FLAG_RESILVER) && mm->mm_replacing &&
291 		    !vdev_dtl_contains(&mm->mm_child[0].mc_vd->vdev_dtl_map,
292 		    zio->io_txg, 1)) {
293 			c = mm->mm_children - 1;
294 			children = 1;
295 		} else {
296 			c = 0;
297 			children = mm->mm_children;
298 		}
299 	}
300 
301 	while (children--) {
302 		mc = &mm->mm_child[c];
303 		zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
304 		    mc->mc_vd, mc->mc_offset, zio->io_data, zio->io_size,
305 		    zio->io_type, zio->io_priority, 0,
306 		    vdev_mirror_child_done, mc));
307 		c++;
308 	}
309 
310 	return (ZIO_PIPELINE_CONTINUE);
311 }
312 
313 static int
314 vdev_mirror_worst_error(mirror_map_t *mm)
315 {
316 	int error[2] = { 0, 0 };
317 
318 	for (int c = 0; c < mm->mm_children; c++) {
319 		mirror_child_t *mc = &mm->mm_child[c];
320 		int s = mc->mc_speculative;
321 		error[s] = zio_worst_error(error[s], mc->mc_error);
322 	}
323 
324 	return (error[0] ? error[0] : error[1]);
325 }
326 
327 static void
328 vdev_mirror_io_done(zio_t *zio)
329 {
330 	mirror_map_t *mm = zio->io_vsd;
331 	mirror_child_t *mc;
332 	int c;
333 	int good_copies = 0;
334 	int unexpected_errors = 0;
335 
336 	for (c = 0; c < mm->mm_children; c++) {
337 		mc = &mm->mm_child[c];
338 
339 		if (mc->mc_error) {
340 			if (!mc->mc_skipped)
341 				unexpected_errors++;
342 		} else if (mc->mc_tried) {
343 			good_copies++;
344 		}
345 	}
346 
347 	if (zio->io_type == ZIO_TYPE_WRITE) {
348 		/*
349 		 * XXX -- for now, treat partial writes as success.
350 		 *
351 		 * Now that we support write reallocation, it would be better
352 		 * to treat partial failure as real failure unless there are
353 		 * no non-degraded top-level vdevs left, and not update DTLs
354 		 * if we intend to reallocate.
355 		 */
356 		/* XXPOLICY */
357 		if (good_copies != mm->mm_children) {
358 			/*
359 			 * Always require at least one good copy.
360 			 *
361 			 * For ditto blocks (io_vd == NULL), require
362 			 * all copies to be good.
363 			 *
364 			 * XXX -- for replacing vdevs, there's no great answer.
365 			 * If the old device is really dead, we may not even
366 			 * be able to access it -- so we only want to
367 			 * require good writes to the new device.  But if
368 			 * the new device turns out to be flaky, we want
369 			 * to be able to detach it -- which requires all
370 			 * writes to the old device to have succeeded.
371 			 */
372 			if (good_copies == 0 || zio->io_vd == NULL)
373 				zio->io_error = vdev_mirror_worst_error(mm);
374 		}
375 		return;
376 	}
377 
378 	ASSERT(zio->io_type == ZIO_TYPE_READ);
379 
380 	/*
381 	 * If we don't have a good copy yet, keep trying other children.
382 	 */
383 	/* XXPOLICY */
384 	if (good_copies == 0 && (c = vdev_mirror_child_select(zio)) != -1) {
385 		ASSERT(c >= 0 && c < mm->mm_children);
386 		mc = &mm->mm_child[c];
387 		zio_vdev_io_redone(zio);
388 		zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
389 		    mc->mc_vd, mc->mc_offset, zio->io_data, zio->io_size,
390 		    ZIO_TYPE_READ, zio->io_priority, 0,
391 		    vdev_mirror_child_done, mc));
392 		return;
393 	}
394 
395 	/* XXPOLICY */
396 	if (good_copies == 0) {
397 		zio->io_error = vdev_mirror_worst_error(mm);
398 		ASSERT(zio->io_error != 0);
399 	}
400 
401 	if (good_copies && (spa_mode & FWRITE) &&
402 	    (unexpected_errors ||
403 	    (zio->io_flags & ZIO_FLAG_RESILVER) ||
404 	    ((zio->io_flags & ZIO_FLAG_SCRUB) && mm->mm_replacing))) {
405 		/*
406 		 * Use the good data we have in hand to repair damaged children.
407 		 */
408 		for (c = 0; c < mm->mm_children; c++) {
409 			/*
410 			 * Don't rewrite known good children.
411 			 * Not only is it unnecessary, it could
412 			 * actually be harmful: if the system lost
413 			 * power while rewriting the only good copy,
414 			 * there would be no good copies left!
415 			 */
416 			mc = &mm->mm_child[c];
417 
418 			if (mc->mc_error == 0) {
419 				if (mc->mc_tried)
420 					continue;
421 				if (!(zio->io_flags & ZIO_FLAG_SCRUB) &&
422 				    !vdev_dtl_contains(&mc->mc_vd->vdev_dtl_map,
423 				    zio->io_txg, 1))
424 					continue;
425 				mc->mc_error = ESTALE;
426 			}
427 
428 			zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
429 			    mc->mc_vd, mc->mc_offset,
430 			    zio->io_data, zio->io_size,
431 			    ZIO_TYPE_WRITE, zio->io_priority,
432 			    ZIO_FLAG_IO_REPAIR, NULL, NULL));
433 		}
434 	}
435 }
436 
437 static void
438 vdev_mirror_state_change(vdev_t *vd, int faulted, int degraded)
439 {
440 	if (faulted == vd->vdev_children)
441 		vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
442 		    VDEV_AUX_NO_REPLICAS);
443 	else if (degraded + faulted != 0)
444 		vdev_set_state(vd, B_FALSE, VDEV_STATE_DEGRADED, VDEV_AUX_NONE);
445 	else
446 		vdev_set_state(vd, B_FALSE, VDEV_STATE_HEALTHY, VDEV_AUX_NONE);
447 }
448 
449 vdev_ops_t vdev_mirror_ops = {
450 	vdev_mirror_open,
451 	vdev_mirror_close,
452 	vdev_default_asize,
453 	vdev_mirror_io_start,
454 	vdev_mirror_io_done,
455 	vdev_mirror_state_change,
456 	VDEV_TYPE_MIRROR,	/* name of this vdev type */
457 	B_FALSE			/* not a leaf vdev */
458 };
459 
460 vdev_ops_t vdev_replacing_ops = {
461 	vdev_mirror_open,
462 	vdev_mirror_close,
463 	vdev_default_asize,
464 	vdev_mirror_io_start,
465 	vdev_mirror_io_done,
466 	vdev_mirror_state_change,
467 	VDEV_TYPE_REPLACING,	/* name of this vdev type */
468 	B_FALSE			/* not a leaf vdev */
469 };
470 
471 vdev_ops_t vdev_spare_ops = {
472 	vdev_mirror_open,
473 	vdev_mirror_close,
474 	vdev_default_asize,
475 	vdev_mirror_io_start,
476 	vdev_mirror_io_done,
477 	vdev_mirror_state_change,
478 	VDEV_TYPE_SPARE,	/* name of this vdev type */
479 	B_FALSE			/* not a leaf vdev */
480 };
481