xref: /illumos-gate/usr/src/uts/common/fs/zfs/metaslab.c (revision 9eb57f7f3fbb970d4b9b89dcd5ecf543fe2414d5)
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 (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
23  * Copyright (c) 2012 by Delphix. All rights reserved.
24  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
25  */
26 
27 #include <sys/zfs_context.h>
28 #include <sys/dmu.h>
29 #include <sys/dmu_tx.h>
30 #include <sys/space_map.h>
31 #include <sys/metaslab_impl.h>
32 #include <sys/vdev_impl.h>
33 #include <sys/zio.h>
34 
35 /*
36  * Allow allocations to switch to gang blocks quickly. We do this to
37  * avoid having to load lots of space_maps in a given txg. There are,
38  * however, some cases where we want to avoid "fast" ganging and instead
39  * we want to do an exhaustive search of all metaslabs on this device.
40  * Currently we don't allow any gang, zil, or dump device related allocations
41  * to "fast" gang.
42  */
43 #define	CAN_FASTGANG(flags) \
44 	(!((flags) & (METASLAB_GANG_CHILD | METASLAB_GANG_HEADER | \
45 	METASLAB_GANG_AVOID)))
46 
47 uint64_t metaslab_aliquot = 512ULL << 10;
48 uint64_t metaslab_gang_bang = SPA_MAXBLOCKSIZE + 1;	/* force gang blocks */
49 
50 /*
51  * The in-core space map representation is more compact than its on-disk form.
52  * The zfs_condense_pct determines how much more compact the in-core
53  * space_map representation must be before we compact it on-disk.
54  * Values should be greater than or equal to 100.
55  */
56 int zfs_condense_pct = 200;
57 
58 /*
59  * This value defines the number of allowed allocation failures per vdev.
60  * If a device reaches this threshold in a given txg then we consider skipping
61  * allocations on that device.
62  */
63 int zfs_mg_alloc_failures;
64 
65 /*
66  * Metaslab debugging: when set, keeps all space maps in core to verify frees.
67  */
68 static int metaslab_debug = 0;
69 
70 /*
71  * Minimum size which forces the dynamic allocator to change
72  * it's allocation strategy.  Once the space map cannot satisfy
73  * an allocation of this size then it switches to using more
74  * aggressive strategy (i.e search by size rather than offset).
75  */
76 uint64_t metaslab_df_alloc_threshold = SPA_MAXBLOCKSIZE;
77 
78 /*
79  * The minimum free space, in percent, which must be available
80  * in a space map to continue allocations in a first-fit fashion.
81  * Once the space_map's free space drops below this level we dynamically
82  * switch to using best-fit allocations.
83  */
84 int metaslab_df_free_pct = 4;
85 
86 /*
87  * A metaslab is considered "free" if it contains a contiguous
88  * segment which is greater than metaslab_min_alloc_size.
89  */
90 uint64_t metaslab_min_alloc_size = DMU_MAX_ACCESS;
91 
92 /*
93  * Max number of space_maps to prefetch.
94  */
95 int metaslab_prefetch_limit = SPA_DVAS_PER_BP;
96 
97 /*
98  * Percentage bonus multiplier for metaslabs that are in the bonus area.
99  */
100 int metaslab_smo_bonus_pct = 150;
101 
102 /*
103  * Should we be willing to write data to degraded vdevs?
104  */
105 boolean_t zfs_write_to_degraded = B_FALSE;
106 
107 /*
108  * ==========================================================================
109  * Metaslab classes
110  * ==========================================================================
111  */
112 metaslab_class_t *
113 metaslab_class_create(spa_t *spa, space_map_ops_t *ops)
114 {
115 	metaslab_class_t *mc;
116 
117 	mc = kmem_zalloc(sizeof (metaslab_class_t), KM_SLEEP);
118 
119 	mc->mc_spa = spa;
120 	mc->mc_rotor = NULL;
121 	mc->mc_ops = ops;
122 
123 	return (mc);
124 }
125 
126 void
127 metaslab_class_destroy(metaslab_class_t *mc)
128 {
129 	ASSERT(mc->mc_rotor == NULL);
130 	ASSERT(mc->mc_alloc == 0);
131 	ASSERT(mc->mc_deferred == 0);
132 	ASSERT(mc->mc_space == 0);
133 	ASSERT(mc->mc_dspace == 0);
134 
135 	kmem_free(mc, sizeof (metaslab_class_t));
136 }
137 
138 int
139 metaslab_class_validate(metaslab_class_t *mc)
140 {
141 	metaslab_group_t *mg;
142 	vdev_t *vd;
143 
144 	/*
145 	 * Must hold one of the spa_config locks.
146 	 */
147 	ASSERT(spa_config_held(mc->mc_spa, SCL_ALL, RW_READER) ||
148 	    spa_config_held(mc->mc_spa, SCL_ALL, RW_WRITER));
149 
150 	if ((mg = mc->mc_rotor) == NULL)
151 		return (0);
152 
153 	do {
154 		vd = mg->mg_vd;
155 		ASSERT(vd->vdev_mg != NULL);
156 		ASSERT3P(vd->vdev_top, ==, vd);
157 		ASSERT3P(mg->mg_class, ==, mc);
158 		ASSERT3P(vd->vdev_ops, !=, &vdev_hole_ops);
159 	} while ((mg = mg->mg_next) != mc->mc_rotor);
160 
161 	return (0);
162 }
163 
164 void
165 metaslab_class_space_update(metaslab_class_t *mc, int64_t alloc_delta,
166     int64_t defer_delta, int64_t space_delta, int64_t dspace_delta)
167 {
168 	atomic_add_64(&mc->mc_alloc, alloc_delta);
169 	atomic_add_64(&mc->mc_deferred, defer_delta);
170 	atomic_add_64(&mc->mc_space, space_delta);
171 	atomic_add_64(&mc->mc_dspace, dspace_delta);
172 }
173 
174 uint64_t
175 metaslab_class_get_alloc(metaslab_class_t *mc)
176 {
177 	return (mc->mc_alloc);
178 }
179 
180 uint64_t
181 metaslab_class_get_deferred(metaslab_class_t *mc)
182 {
183 	return (mc->mc_deferred);
184 }
185 
186 uint64_t
187 metaslab_class_get_space(metaslab_class_t *mc)
188 {
189 	return (mc->mc_space);
190 }
191 
192 uint64_t
193 metaslab_class_get_dspace(metaslab_class_t *mc)
194 {
195 	return (spa_deflate(mc->mc_spa) ? mc->mc_dspace : mc->mc_space);
196 }
197 
198 /*
199  * ==========================================================================
200  * Metaslab groups
201  * ==========================================================================
202  */
203 static int
204 metaslab_compare(const void *x1, const void *x2)
205 {
206 	const metaslab_t *m1 = x1;
207 	const metaslab_t *m2 = x2;
208 
209 	if (m1->ms_weight < m2->ms_weight)
210 		return (1);
211 	if (m1->ms_weight > m2->ms_weight)
212 		return (-1);
213 
214 	/*
215 	 * If the weights are identical, use the offset to force uniqueness.
216 	 */
217 	if (m1->ms_map->sm_start < m2->ms_map->sm_start)
218 		return (-1);
219 	if (m1->ms_map->sm_start > m2->ms_map->sm_start)
220 		return (1);
221 
222 	ASSERT3P(m1, ==, m2);
223 
224 	return (0);
225 }
226 
227 metaslab_group_t *
228 metaslab_group_create(metaslab_class_t *mc, vdev_t *vd)
229 {
230 	metaslab_group_t *mg;
231 
232 	mg = kmem_zalloc(sizeof (metaslab_group_t), KM_SLEEP);
233 	mutex_init(&mg->mg_lock, NULL, MUTEX_DEFAULT, NULL);
234 	avl_create(&mg->mg_metaslab_tree, metaslab_compare,
235 	    sizeof (metaslab_t), offsetof(struct metaslab, ms_group_node));
236 	mg->mg_vd = vd;
237 	mg->mg_class = mc;
238 	mg->mg_activation_count = 0;
239 
240 	return (mg);
241 }
242 
243 void
244 metaslab_group_destroy(metaslab_group_t *mg)
245 {
246 	ASSERT(mg->mg_prev == NULL);
247 	ASSERT(mg->mg_next == NULL);
248 	/*
249 	 * We may have gone below zero with the activation count
250 	 * either because we never activated in the first place or
251 	 * because we're done, and possibly removing the vdev.
252 	 */
253 	ASSERT(mg->mg_activation_count <= 0);
254 
255 	avl_destroy(&mg->mg_metaslab_tree);
256 	mutex_destroy(&mg->mg_lock);
257 	kmem_free(mg, sizeof (metaslab_group_t));
258 }
259 
260 void
261 metaslab_group_activate(metaslab_group_t *mg)
262 {
263 	metaslab_class_t *mc = mg->mg_class;
264 	metaslab_group_t *mgprev, *mgnext;
265 
266 	ASSERT(spa_config_held(mc->mc_spa, SCL_ALLOC, RW_WRITER));
267 
268 	ASSERT(mc->mc_rotor != mg);
269 	ASSERT(mg->mg_prev == NULL);
270 	ASSERT(mg->mg_next == NULL);
271 	ASSERT(mg->mg_activation_count <= 0);
272 
273 	if (++mg->mg_activation_count <= 0)
274 		return;
275 
276 	mg->mg_aliquot = metaslab_aliquot * MAX(1, mg->mg_vd->vdev_children);
277 
278 	if ((mgprev = mc->mc_rotor) == NULL) {
279 		mg->mg_prev = mg;
280 		mg->mg_next = mg;
281 	} else {
282 		mgnext = mgprev->mg_next;
283 		mg->mg_prev = mgprev;
284 		mg->mg_next = mgnext;
285 		mgprev->mg_next = mg;
286 		mgnext->mg_prev = mg;
287 	}
288 	mc->mc_rotor = mg;
289 }
290 
291 void
292 metaslab_group_passivate(metaslab_group_t *mg)
293 {
294 	metaslab_class_t *mc = mg->mg_class;
295 	metaslab_group_t *mgprev, *mgnext;
296 
297 	ASSERT(spa_config_held(mc->mc_spa, SCL_ALLOC, RW_WRITER));
298 
299 	if (--mg->mg_activation_count != 0) {
300 		ASSERT(mc->mc_rotor != mg);
301 		ASSERT(mg->mg_prev == NULL);
302 		ASSERT(mg->mg_next == NULL);
303 		ASSERT(mg->mg_activation_count < 0);
304 		return;
305 	}
306 
307 	mgprev = mg->mg_prev;
308 	mgnext = mg->mg_next;
309 
310 	if (mg == mgnext) {
311 		mc->mc_rotor = NULL;
312 	} else {
313 		mc->mc_rotor = mgnext;
314 		mgprev->mg_next = mgnext;
315 		mgnext->mg_prev = mgprev;
316 	}
317 
318 	mg->mg_prev = NULL;
319 	mg->mg_next = NULL;
320 }
321 
322 static void
323 metaslab_group_add(metaslab_group_t *mg, metaslab_t *msp)
324 {
325 	mutex_enter(&mg->mg_lock);
326 	ASSERT(msp->ms_group == NULL);
327 	msp->ms_group = mg;
328 	msp->ms_weight = 0;
329 	avl_add(&mg->mg_metaslab_tree, msp);
330 	mutex_exit(&mg->mg_lock);
331 }
332 
333 static void
334 metaslab_group_remove(metaslab_group_t *mg, metaslab_t *msp)
335 {
336 	mutex_enter(&mg->mg_lock);
337 	ASSERT(msp->ms_group == mg);
338 	avl_remove(&mg->mg_metaslab_tree, msp);
339 	msp->ms_group = NULL;
340 	mutex_exit(&mg->mg_lock);
341 }
342 
343 static void
344 metaslab_group_sort(metaslab_group_t *mg, metaslab_t *msp, uint64_t weight)
345 {
346 	/*
347 	 * Although in principle the weight can be any value, in
348 	 * practice we do not use values in the range [1, 510].
349 	 */
350 	ASSERT(weight >= SPA_MINBLOCKSIZE-1 || weight == 0);
351 	ASSERT(MUTEX_HELD(&msp->ms_lock));
352 
353 	mutex_enter(&mg->mg_lock);
354 	ASSERT(msp->ms_group == mg);
355 	avl_remove(&mg->mg_metaslab_tree, msp);
356 	msp->ms_weight = weight;
357 	avl_add(&mg->mg_metaslab_tree, msp);
358 	mutex_exit(&mg->mg_lock);
359 }
360 
361 /*
362  * ==========================================================================
363  * Common allocator routines
364  * ==========================================================================
365  */
366 static int
367 metaslab_segsize_compare(const void *x1, const void *x2)
368 {
369 	const space_seg_t *s1 = x1;
370 	const space_seg_t *s2 = x2;
371 	uint64_t ss_size1 = s1->ss_end - s1->ss_start;
372 	uint64_t ss_size2 = s2->ss_end - s2->ss_start;
373 
374 	if (ss_size1 < ss_size2)
375 		return (-1);
376 	if (ss_size1 > ss_size2)
377 		return (1);
378 
379 	if (s1->ss_start < s2->ss_start)
380 		return (-1);
381 	if (s1->ss_start > s2->ss_start)
382 		return (1);
383 
384 	return (0);
385 }
386 
387 /*
388  * This is a helper function that can be used by the allocator to find
389  * a suitable block to allocate. This will search the specified AVL
390  * tree looking for a block that matches the specified criteria.
391  */
392 static uint64_t
393 metaslab_block_picker(avl_tree_t *t, uint64_t *cursor, uint64_t size,
394     uint64_t align)
395 {
396 	space_seg_t *ss, ssearch;
397 	avl_index_t where;
398 
399 	ssearch.ss_start = *cursor;
400 	ssearch.ss_end = *cursor + size;
401 
402 	ss = avl_find(t, &ssearch, &where);
403 	if (ss == NULL)
404 		ss = avl_nearest(t, where, AVL_AFTER);
405 
406 	while (ss != NULL) {
407 		uint64_t offset = P2ROUNDUP(ss->ss_start, align);
408 
409 		if (offset + size <= ss->ss_end) {
410 			*cursor = offset + size;
411 			return (offset);
412 		}
413 		ss = AVL_NEXT(t, ss);
414 	}
415 
416 	/*
417 	 * If we know we've searched the whole map (*cursor == 0), give up.
418 	 * Otherwise, reset the cursor to the beginning and try again.
419 	 */
420 	if (*cursor == 0)
421 		return (-1ULL);
422 
423 	*cursor = 0;
424 	return (metaslab_block_picker(t, cursor, size, align));
425 }
426 
427 static void
428 metaslab_pp_load(space_map_t *sm)
429 {
430 	space_seg_t *ss;
431 
432 	ASSERT(sm->sm_ppd == NULL);
433 	sm->sm_ppd = kmem_zalloc(64 * sizeof (uint64_t), KM_SLEEP);
434 
435 	sm->sm_pp_root = kmem_alloc(sizeof (avl_tree_t), KM_SLEEP);
436 	avl_create(sm->sm_pp_root, metaslab_segsize_compare,
437 	    sizeof (space_seg_t), offsetof(struct space_seg, ss_pp_node));
438 
439 	for (ss = avl_first(&sm->sm_root); ss; ss = AVL_NEXT(&sm->sm_root, ss))
440 		avl_add(sm->sm_pp_root, ss);
441 }
442 
443 static void
444 metaslab_pp_unload(space_map_t *sm)
445 {
446 	void *cookie = NULL;
447 
448 	kmem_free(sm->sm_ppd, 64 * sizeof (uint64_t));
449 	sm->sm_ppd = NULL;
450 
451 	while (avl_destroy_nodes(sm->sm_pp_root, &cookie) != NULL) {
452 		/* tear down the tree */
453 	}
454 
455 	avl_destroy(sm->sm_pp_root);
456 	kmem_free(sm->sm_pp_root, sizeof (avl_tree_t));
457 	sm->sm_pp_root = NULL;
458 }
459 
460 /* ARGSUSED */
461 static void
462 metaslab_pp_claim(space_map_t *sm, uint64_t start, uint64_t size)
463 {
464 	/* No need to update cursor */
465 }
466 
467 /* ARGSUSED */
468 static void
469 metaslab_pp_free(space_map_t *sm, uint64_t start, uint64_t size)
470 {
471 	/* No need to update cursor */
472 }
473 
474 /*
475  * Return the maximum contiguous segment within the metaslab.
476  */
477 uint64_t
478 metaslab_pp_maxsize(space_map_t *sm)
479 {
480 	avl_tree_t *t = sm->sm_pp_root;
481 	space_seg_t *ss;
482 
483 	if (t == NULL || (ss = avl_last(t)) == NULL)
484 		return (0ULL);
485 
486 	return (ss->ss_end - ss->ss_start);
487 }
488 
489 /*
490  * ==========================================================================
491  * The first-fit block allocator
492  * ==========================================================================
493  */
494 static uint64_t
495 metaslab_ff_alloc(space_map_t *sm, uint64_t size)
496 {
497 	avl_tree_t *t = &sm->sm_root;
498 	uint64_t align = size & -size;
499 	uint64_t *cursor = (uint64_t *)sm->sm_ppd + highbit(align) - 1;
500 
501 	return (metaslab_block_picker(t, cursor, size, align));
502 }
503 
504 /* ARGSUSED */
505 boolean_t
506 metaslab_ff_fragmented(space_map_t *sm)
507 {
508 	return (B_TRUE);
509 }
510 
511 static space_map_ops_t metaslab_ff_ops = {
512 	metaslab_pp_load,
513 	metaslab_pp_unload,
514 	metaslab_ff_alloc,
515 	metaslab_pp_claim,
516 	metaslab_pp_free,
517 	metaslab_pp_maxsize,
518 	metaslab_ff_fragmented
519 };
520 
521 /*
522  * ==========================================================================
523  * Dynamic block allocator -
524  * Uses the first fit allocation scheme until space get low and then
525  * adjusts to a best fit allocation method. Uses metaslab_df_alloc_threshold
526  * and metaslab_df_free_pct to determine when to switch the allocation scheme.
527  * ==========================================================================
528  */
529 static uint64_t
530 metaslab_df_alloc(space_map_t *sm, uint64_t size)
531 {
532 	avl_tree_t *t = &sm->sm_root;
533 	uint64_t align = size & -size;
534 	uint64_t *cursor = (uint64_t *)sm->sm_ppd + highbit(align) - 1;
535 	uint64_t max_size = metaslab_pp_maxsize(sm);
536 	int free_pct = sm->sm_space * 100 / sm->sm_size;
537 
538 	ASSERT(MUTEX_HELD(sm->sm_lock));
539 	ASSERT3U(avl_numnodes(&sm->sm_root), ==, avl_numnodes(sm->sm_pp_root));
540 
541 	if (max_size < size)
542 		return (-1ULL);
543 
544 	/*
545 	 * If we're running low on space switch to using the size
546 	 * sorted AVL tree (best-fit).
547 	 */
548 	if (max_size < metaslab_df_alloc_threshold ||
549 	    free_pct < metaslab_df_free_pct) {
550 		t = sm->sm_pp_root;
551 		*cursor = 0;
552 	}
553 
554 	return (metaslab_block_picker(t, cursor, size, 1ULL));
555 }
556 
557 static boolean_t
558 metaslab_df_fragmented(space_map_t *sm)
559 {
560 	uint64_t max_size = metaslab_pp_maxsize(sm);
561 	int free_pct = sm->sm_space * 100 / sm->sm_size;
562 
563 	if (max_size >= metaslab_df_alloc_threshold &&
564 	    free_pct >= metaslab_df_free_pct)
565 		return (B_FALSE);
566 
567 	return (B_TRUE);
568 }
569 
570 static space_map_ops_t metaslab_df_ops = {
571 	metaslab_pp_load,
572 	metaslab_pp_unload,
573 	metaslab_df_alloc,
574 	metaslab_pp_claim,
575 	metaslab_pp_free,
576 	metaslab_pp_maxsize,
577 	metaslab_df_fragmented
578 };
579 
580 /*
581  * ==========================================================================
582  * Other experimental allocators
583  * ==========================================================================
584  */
585 static uint64_t
586 metaslab_cdf_alloc(space_map_t *sm, uint64_t size)
587 {
588 	avl_tree_t *t = &sm->sm_root;
589 	uint64_t *cursor = (uint64_t *)sm->sm_ppd;
590 	uint64_t *extent_end = (uint64_t *)sm->sm_ppd + 1;
591 	uint64_t max_size = metaslab_pp_maxsize(sm);
592 	uint64_t rsize = size;
593 	uint64_t offset = 0;
594 
595 	ASSERT(MUTEX_HELD(sm->sm_lock));
596 	ASSERT3U(avl_numnodes(&sm->sm_root), ==, avl_numnodes(sm->sm_pp_root));
597 
598 	if (max_size < size)
599 		return (-1ULL);
600 
601 	ASSERT3U(*extent_end, >=, *cursor);
602 
603 	/*
604 	 * If we're running low on space switch to using the size
605 	 * sorted AVL tree (best-fit).
606 	 */
607 	if ((*cursor + size) > *extent_end) {
608 
609 		t = sm->sm_pp_root;
610 		*cursor = *extent_end = 0;
611 
612 		if (max_size > 2 * SPA_MAXBLOCKSIZE)
613 			rsize = MIN(metaslab_min_alloc_size, max_size);
614 		offset = metaslab_block_picker(t, extent_end, rsize, 1ULL);
615 		if (offset != -1)
616 			*cursor = offset + size;
617 	} else {
618 		offset = metaslab_block_picker(t, cursor, rsize, 1ULL);
619 	}
620 	ASSERT3U(*cursor, <=, *extent_end);
621 	return (offset);
622 }
623 
624 static boolean_t
625 metaslab_cdf_fragmented(space_map_t *sm)
626 {
627 	uint64_t max_size = metaslab_pp_maxsize(sm);
628 
629 	if (max_size > (metaslab_min_alloc_size * 10))
630 		return (B_FALSE);
631 	return (B_TRUE);
632 }
633 
634 static space_map_ops_t metaslab_cdf_ops = {
635 	metaslab_pp_load,
636 	metaslab_pp_unload,
637 	metaslab_cdf_alloc,
638 	metaslab_pp_claim,
639 	metaslab_pp_free,
640 	metaslab_pp_maxsize,
641 	metaslab_cdf_fragmented
642 };
643 
644 uint64_t metaslab_ndf_clump_shift = 4;
645 
646 static uint64_t
647 metaslab_ndf_alloc(space_map_t *sm, uint64_t size)
648 {
649 	avl_tree_t *t = &sm->sm_root;
650 	avl_index_t where;
651 	space_seg_t *ss, ssearch;
652 	uint64_t hbit = highbit(size);
653 	uint64_t *cursor = (uint64_t *)sm->sm_ppd + hbit - 1;
654 	uint64_t max_size = metaslab_pp_maxsize(sm);
655 
656 	ASSERT(MUTEX_HELD(sm->sm_lock));
657 	ASSERT3U(avl_numnodes(&sm->sm_root), ==, avl_numnodes(sm->sm_pp_root));
658 
659 	if (max_size < size)
660 		return (-1ULL);
661 
662 	ssearch.ss_start = *cursor;
663 	ssearch.ss_end = *cursor + size;
664 
665 	ss = avl_find(t, &ssearch, &where);
666 	if (ss == NULL || (ss->ss_start + size > ss->ss_end)) {
667 		t = sm->sm_pp_root;
668 
669 		ssearch.ss_start = 0;
670 		ssearch.ss_end = MIN(max_size,
671 		    1ULL << (hbit + metaslab_ndf_clump_shift));
672 		ss = avl_find(t, &ssearch, &where);
673 		if (ss == NULL)
674 			ss = avl_nearest(t, where, AVL_AFTER);
675 		ASSERT(ss != NULL);
676 	}
677 
678 	if (ss != NULL) {
679 		if (ss->ss_start + size <= ss->ss_end) {
680 			*cursor = ss->ss_start + size;
681 			return (ss->ss_start);
682 		}
683 	}
684 	return (-1ULL);
685 }
686 
687 static boolean_t
688 metaslab_ndf_fragmented(space_map_t *sm)
689 {
690 	uint64_t max_size = metaslab_pp_maxsize(sm);
691 
692 	if (max_size > (metaslab_min_alloc_size << metaslab_ndf_clump_shift))
693 		return (B_FALSE);
694 	return (B_TRUE);
695 }
696 
697 
698 static space_map_ops_t metaslab_ndf_ops = {
699 	metaslab_pp_load,
700 	metaslab_pp_unload,
701 	metaslab_ndf_alloc,
702 	metaslab_pp_claim,
703 	metaslab_pp_free,
704 	metaslab_pp_maxsize,
705 	metaslab_ndf_fragmented
706 };
707 
708 space_map_ops_t *zfs_metaslab_ops = &metaslab_df_ops;
709 
710 /*
711  * ==========================================================================
712  * Metaslabs
713  * ==========================================================================
714  */
715 metaslab_t *
716 metaslab_init(metaslab_group_t *mg, space_map_obj_t *smo,
717 	uint64_t start, uint64_t size, uint64_t txg)
718 {
719 	vdev_t *vd = mg->mg_vd;
720 	metaslab_t *msp;
721 
722 	msp = kmem_zalloc(sizeof (metaslab_t), KM_SLEEP);
723 	mutex_init(&msp->ms_lock, NULL, MUTEX_DEFAULT, NULL);
724 
725 	msp->ms_smo_syncing = *smo;
726 
727 	/*
728 	 * We create the main space map here, but we don't create the
729 	 * allocmaps and freemaps until metaslab_sync_done().  This serves
730 	 * two purposes: it allows metaslab_sync_done() to detect the
731 	 * addition of new space; and for debugging, it ensures that we'd
732 	 * data fault on any attempt to use this metaslab before it's ready.
733 	 */
734 	msp->ms_map = kmem_zalloc(sizeof (space_map_t), KM_SLEEP);
735 	space_map_create(msp->ms_map, start, size,
736 	    vd->vdev_ashift, &msp->ms_lock);
737 
738 	metaslab_group_add(mg, msp);
739 
740 	if (metaslab_debug && smo->smo_object != 0) {
741 		mutex_enter(&msp->ms_lock);
742 		VERIFY(space_map_load(msp->ms_map, mg->mg_class->mc_ops,
743 		    SM_FREE, smo, spa_meta_objset(vd->vdev_spa)) == 0);
744 		mutex_exit(&msp->ms_lock);
745 	}
746 
747 	/*
748 	 * If we're opening an existing pool (txg == 0) or creating
749 	 * a new one (txg == TXG_INITIAL), all space is available now.
750 	 * If we're adding space to an existing pool, the new space
751 	 * does not become available until after this txg has synced.
752 	 */
753 	if (txg <= TXG_INITIAL)
754 		metaslab_sync_done(msp, 0);
755 
756 	if (txg != 0) {
757 		vdev_dirty(vd, 0, NULL, txg);
758 		vdev_dirty(vd, VDD_METASLAB, msp, txg);
759 	}
760 
761 	return (msp);
762 }
763 
764 void
765 metaslab_fini(metaslab_t *msp)
766 {
767 	metaslab_group_t *mg = msp->ms_group;
768 
769 	vdev_space_update(mg->mg_vd,
770 	    -msp->ms_smo.smo_alloc, 0, -msp->ms_map->sm_size);
771 
772 	metaslab_group_remove(mg, msp);
773 
774 	mutex_enter(&msp->ms_lock);
775 
776 	space_map_unload(msp->ms_map);
777 	space_map_destroy(msp->ms_map);
778 	kmem_free(msp->ms_map, sizeof (*msp->ms_map));
779 
780 	for (int t = 0; t < TXG_SIZE; t++) {
781 		space_map_destroy(msp->ms_allocmap[t]);
782 		space_map_destroy(msp->ms_freemap[t]);
783 		kmem_free(msp->ms_allocmap[t], sizeof (*msp->ms_allocmap[t]));
784 		kmem_free(msp->ms_freemap[t], sizeof (*msp->ms_freemap[t]));
785 	}
786 
787 	for (int t = 0; t < TXG_DEFER_SIZE; t++) {
788 		space_map_destroy(msp->ms_defermap[t]);
789 		kmem_free(msp->ms_defermap[t], sizeof (*msp->ms_defermap[t]));
790 	}
791 
792 	ASSERT0(msp->ms_deferspace);
793 
794 	mutex_exit(&msp->ms_lock);
795 	mutex_destroy(&msp->ms_lock);
796 
797 	kmem_free(msp, sizeof (metaslab_t));
798 }
799 
800 #define	METASLAB_WEIGHT_PRIMARY		(1ULL << 63)
801 #define	METASLAB_WEIGHT_SECONDARY	(1ULL << 62)
802 #define	METASLAB_ACTIVE_MASK		\
803 	(METASLAB_WEIGHT_PRIMARY | METASLAB_WEIGHT_SECONDARY)
804 
805 static uint64_t
806 metaslab_weight(metaslab_t *msp)
807 {
808 	metaslab_group_t *mg = msp->ms_group;
809 	space_map_t *sm = msp->ms_map;
810 	space_map_obj_t *smo = &msp->ms_smo;
811 	vdev_t *vd = mg->mg_vd;
812 	uint64_t weight, space;
813 
814 	ASSERT(MUTEX_HELD(&msp->ms_lock));
815 
816 	/*
817 	 * This vdev is in the process of being removed so there is nothing
818 	 * for us to do here.
819 	 */
820 	if (vd->vdev_removing) {
821 		ASSERT0(smo->smo_alloc);
822 		ASSERT0(vd->vdev_ms_shift);
823 		return (0);
824 	}
825 
826 	/*
827 	 * The baseline weight is the metaslab's free space.
828 	 */
829 	space = sm->sm_size - smo->smo_alloc;
830 	weight = space;
831 
832 	/*
833 	 * Modern disks have uniform bit density and constant angular velocity.
834 	 * Therefore, the outer recording zones are faster (higher bandwidth)
835 	 * than the inner zones by the ratio of outer to inner track diameter,
836 	 * which is typically around 2:1.  We account for this by assigning
837 	 * higher weight to lower metaslabs (multiplier ranging from 2x to 1x).
838 	 * In effect, this means that we'll select the metaslab with the most
839 	 * free bandwidth rather than simply the one with the most free space.
840 	 */
841 	weight = 2 * weight -
842 	    ((sm->sm_start >> vd->vdev_ms_shift) * weight) / vd->vdev_ms_count;
843 	ASSERT(weight >= space && weight <= 2 * space);
844 
845 	/*
846 	 * For locality, assign higher weight to metaslabs which have
847 	 * a lower offset than what we've already activated.
848 	 */
849 	if (sm->sm_start <= mg->mg_bonus_area)
850 		weight *= (metaslab_smo_bonus_pct / 100);
851 	ASSERT(weight >= space &&
852 	    weight <= 2 * (metaslab_smo_bonus_pct / 100) * space);
853 
854 	if (sm->sm_loaded && !sm->sm_ops->smop_fragmented(sm)) {
855 		/*
856 		 * If this metaslab is one we're actively using, adjust its
857 		 * weight to make it preferable to any inactive metaslab so
858 		 * we'll polish it off.
859 		 */
860 		weight |= (msp->ms_weight & METASLAB_ACTIVE_MASK);
861 	}
862 	return (weight);
863 }
864 
865 static void
866 metaslab_prefetch(metaslab_group_t *mg)
867 {
868 	spa_t *spa = mg->mg_vd->vdev_spa;
869 	metaslab_t *msp;
870 	avl_tree_t *t = &mg->mg_metaslab_tree;
871 	int m;
872 
873 	mutex_enter(&mg->mg_lock);
874 
875 	/*
876 	 * Prefetch the next potential metaslabs
877 	 */
878 	for (msp = avl_first(t), m = 0; msp; msp = AVL_NEXT(t, msp), m++) {
879 		space_map_t *sm = msp->ms_map;
880 		space_map_obj_t *smo = &msp->ms_smo;
881 
882 		/* If we have reached our prefetch limit then we're done */
883 		if (m >= metaslab_prefetch_limit)
884 			break;
885 
886 		if (!sm->sm_loaded && smo->smo_object != 0) {
887 			mutex_exit(&mg->mg_lock);
888 			dmu_prefetch(spa_meta_objset(spa), smo->smo_object,
889 			    0ULL, smo->smo_objsize);
890 			mutex_enter(&mg->mg_lock);
891 		}
892 	}
893 	mutex_exit(&mg->mg_lock);
894 }
895 
896 static int
897 metaslab_activate(metaslab_t *msp, uint64_t activation_weight)
898 {
899 	metaslab_group_t *mg = msp->ms_group;
900 	space_map_t *sm = msp->ms_map;
901 	space_map_ops_t *sm_ops = msp->ms_group->mg_class->mc_ops;
902 
903 	ASSERT(MUTEX_HELD(&msp->ms_lock));
904 
905 	if ((msp->ms_weight & METASLAB_ACTIVE_MASK) == 0) {
906 		space_map_load_wait(sm);
907 		if (!sm->sm_loaded) {
908 			space_map_obj_t *smo = &msp->ms_smo;
909 
910 			int error = space_map_load(sm, sm_ops, SM_FREE, smo,
911 			    spa_meta_objset(msp->ms_group->mg_vd->vdev_spa));
912 			if (error)  {
913 				metaslab_group_sort(msp->ms_group, msp, 0);
914 				return (error);
915 			}
916 			for (int t = 0; t < TXG_DEFER_SIZE; t++)
917 				space_map_walk(msp->ms_defermap[t],
918 				    space_map_claim, sm);
919 
920 		}
921 
922 		/*
923 		 * Track the bonus area as we activate new metaslabs.
924 		 */
925 		if (sm->sm_start > mg->mg_bonus_area) {
926 			mutex_enter(&mg->mg_lock);
927 			mg->mg_bonus_area = sm->sm_start;
928 			mutex_exit(&mg->mg_lock);
929 		}
930 
931 		metaslab_group_sort(msp->ms_group, msp,
932 		    msp->ms_weight | activation_weight);
933 	}
934 	ASSERT(sm->sm_loaded);
935 	ASSERT(msp->ms_weight & METASLAB_ACTIVE_MASK);
936 
937 	return (0);
938 }
939 
940 static void
941 metaslab_passivate(metaslab_t *msp, uint64_t size)
942 {
943 	/*
944 	 * If size < SPA_MINBLOCKSIZE, then we will not allocate from
945 	 * this metaslab again.  In that case, it had better be empty,
946 	 * or we would be leaving space on the table.
947 	 */
948 	ASSERT(size >= SPA_MINBLOCKSIZE || msp->ms_map->sm_space == 0);
949 	metaslab_group_sort(msp->ms_group, msp, MIN(msp->ms_weight, size));
950 	ASSERT((msp->ms_weight & METASLAB_ACTIVE_MASK) == 0);
951 }
952 
953 /*
954  * Determine if the in-core space map representation can be condensed on-disk.
955  * We would like to use the following criteria to make our decision:
956  *
957  * 1. The size of the space map object should not dramatically increase as a
958  * result of writing out our in-core free map.
959  *
960  * 2. The minimal on-disk space map representation is zfs_condense_pct/100
961  * times the size than the in-core representation (i.e. zfs_condense_pct = 110
962  * and in-core = 1MB, minimal = 1.1.MB).
963  *
964  * Checking the first condition is tricky since we don't want to walk
965  * the entire AVL tree calculating the estimated on-disk size. Instead we
966  * use the size-ordered AVL tree in the space map and calculate the
967  * size required for the largest segment in our in-core free map. If the
968  * size required to represent that segment on disk is larger than the space
969  * map object then we avoid condensing this map.
970  *
971  * To determine the second criterion we use a best-case estimate and assume
972  * each segment can be represented on-disk as a single 64-bit entry. We refer
973  * to this best-case estimate as the space map's minimal form.
974  */
975 static boolean_t
976 metaslab_should_condense(metaslab_t *msp)
977 {
978 	space_map_t *sm = msp->ms_map;
979 	space_map_obj_t *smo = &msp->ms_smo_syncing;
980 	space_seg_t *ss;
981 	uint64_t size, entries, segsz;
982 
983 	ASSERT(MUTEX_HELD(&msp->ms_lock));
984 	ASSERT(sm->sm_loaded);
985 
986 	/*
987 	 * Use the sm_pp_root AVL tree, which is ordered by size, to obtain
988 	 * the largest segment in the in-core free map. If the tree is
989 	 * empty then we should condense the map.
990 	 */
991 	ss = avl_last(sm->sm_pp_root);
992 	if (ss == NULL)
993 		return (B_TRUE);
994 
995 	/*
996 	 * Calculate the number of 64-bit entries this segment would
997 	 * require when written to disk. If this single segment would be
998 	 * larger on-disk than the entire current on-disk structure, then
999 	 * clearly condensing will increase the on-disk structure size.
1000 	 */
1001 	size = (ss->ss_end - ss->ss_start) >> sm->sm_shift;
1002 	entries = size / (MIN(size, SM_RUN_MAX));
1003 	segsz = entries * sizeof (uint64_t);
1004 
1005 	return (segsz <= smo->smo_objsize &&
1006 	    smo->smo_objsize >= (zfs_condense_pct *
1007 	    sizeof (uint64_t) * avl_numnodes(&sm->sm_root)) / 100);
1008 }
1009 
1010 /*
1011  * Condense the on-disk space map representation to its minimized form.
1012  * The minimized form consists of a small number of allocations followed by
1013  * the in-core free map.
1014  */
1015 static void
1016 metaslab_condense(metaslab_t *msp, uint64_t txg, dmu_tx_t *tx)
1017 {
1018 	spa_t *spa = msp->ms_group->mg_vd->vdev_spa;
1019 	space_map_t *freemap = msp->ms_freemap[txg & TXG_MASK];
1020 	space_map_t condense_map;
1021 	space_map_t *sm = msp->ms_map;
1022 	objset_t *mos = spa_meta_objset(spa);
1023 	space_map_obj_t *smo = &msp->ms_smo_syncing;
1024 
1025 	ASSERT(MUTEX_HELD(&msp->ms_lock));
1026 	ASSERT3U(spa_sync_pass(spa), ==, 1);
1027 	ASSERT(sm->sm_loaded);
1028 
1029 	spa_dbgmsg(spa, "condensing: txg %llu, msp[%llu] %p, "
1030 	    "smo size %llu, segments %lu", txg,
1031 	    (msp->ms_map->sm_start / msp->ms_map->sm_size), msp,
1032 	    smo->smo_objsize, avl_numnodes(&sm->sm_root));
1033 
1034 	/*
1035 	 * Create an map that is a 100% allocated map. We remove segments
1036 	 * that have been freed in this txg, any deferred frees that exist,
1037 	 * and any allocation in the future. Removing segments should be
1038 	 * a relatively inexpensive operation since we expect these maps to
1039 	 * a small number of nodes.
1040 	 */
1041 	space_map_create(&condense_map, sm->sm_start, sm->sm_size,
1042 	    sm->sm_shift, sm->sm_lock);
1043 	space_map_add(&condense_map, condense_map.sm_start,
1044 	    condense_map.sm_size);
1045 
1046 	/*
1047 	 * Remove what's been freed in this txg from the condense_map.
1048 	 * Since we're in sync_pass 1, we know that all the frees from
1049 	 * this txg are in the freemap.
1050 	 */
1051 	space_map_walk(freemap, space_map_remove, &condense_map);
1052 
1053 	for (int t = 0; t < TXG_DEFER_SIZE; t++)
1054 		space_map_walk(msp->ms_defermap[t],
1055 		    space_map_remove, &condense_map);
1056 
1057 	for (int t = 1; t < TXG_CONCURRENT_STATES; t++)
1058 		space_map_walk(msp->ms_allocmap[(txg + t) & TXG_MASK],
1059 		    space_map_remove, &condense_map);
1060 
1061 	/*
1062 	 * We're about to drop the metaslab's lock thus allowing
1063 	 * other consumers to change it's content. Set the
1064 	 * space_map's sm_condensing flag to ensure that
1065 	 * allocations on this metaslab do not occur while we're
1066 	 * in the middle of committing it to disk. This is only critical
1067 	 * for the ms_map as all other space_maps use per txg
1068 	 * views of their content.
1069 	 */
1070 	sm->sm_condensing = B_TRUE;
1071 
1072 	mutex_exit(&msp->ms_lock);
1073 	space_map_truncate(smo, mos, tx);
1074 	mutex_enter(&msp->ms_lock);
1075 
1076 	/*
1077 	 * While we would ideally like to create a space_map representation
1078 	 * that consists only of allocation records, doing so can be
1079 	 * prohibitively expensive because the in-core free map can be
1080 	 * large, and therefore computationally expensive to subtract
1081 	 * from the condense_map. Instead we sync out two maps, a cheap
1082 	 * allocation only map followed by the in-core free map. While not
1083 	 * optimal, this is typically close to optimal, and much cheaper to
1084 	 * compute.
1085 	 */
1086 	space_map_sync(&condense_map, SM_ALLOC, smo, mos, tx);
1087 	space_map_vacate(&condense_map, NULL, NULL);
1088 	space_map_destroy(&condense_map);
1089 
1090 	space_map_sync(sm, SM_FREE, smo, mos, tx);
1091 	sm->sm_condensing = B_FALSE;
1092 
1093 	spa_dbgmsg(spa, "condensed: txg %llu, msp[%llu] %p, "
1094 	    "smo size %llu", txg,
1095 	    (msp->ms_map->sm_start / msp->ms_map->sm_size), msp,
1096 	    smo->smo_objsize);
1097 }
1098 
1099 /*
1100  * Write a metaslab to disk in the context of the specified transaction group.
1101  */
1102 void
1103 metaslab_sync(metaslab_t *msp, uint64_t txg)
1104 {
1105 	vdev_t *vd = msp->ms_group->mg_vd;
1106 	spa_t *spa = vd->vdev_spa;
1107 	objset_t *mos = spa_meta_objset(spa);
1108 	space_map_t *allocmap = msp->ms_allocmap[txg & TXG_MASK];
1109 	space_map_t **freemap = &msp->ms_freemap[txg & TXG_MASK];
1110 	space_map_t **freed_map = &msp->ms_freemap[TXG_CLEAN(txg) & TXG_MASK];
1111 	space_map_t *sm = msp->ms_map;
1112 	space_map_obj_t *smo = &msp->ms_smo_syncing;
1113 	dmu_buf_t *db;
1114 	dmu_tx_t *tx;
1115 
1116 	ASSERT(!vd->vdev_ishole);
1117 
1118 	/*
1119 	 * This metaslab has just been added so there's no work to do now.
1120 	 */
1121 	if (*freemap == NULL) {
1122 		ASSERT3P(allocmap, ==, NULL);
1123 		return;
1124 	}
1125 
1126 	ASSERT3P(allocmap, !=, NULL);
1127 	ASSERT3P(*freemap, !=, NULL);
1128 	ASSERT3P(*freed_map, !=, NULL);
1129 
1130 	if (allocmap->sm_space == 0 && (*freemap)->sm_space == 0)
1131 		return;
1132 
1133 	/*
1134 	 * The only state that can actually be changing concurrently with
1135 	 * metaslab_sync() is the metaslab's ms_map.  No other thread can
1136 	 * be modifying this txg's allocmap, freemap, freed_map, or smo.
1137 	 * Therefore, we only hold ms_lock to satify space_map ASSERTs.
1138 	 * We drop it whenever we call into the DMU, because the DMU
1139 	 * can call down to us (e.g. via zio_free()) at any time.
1140 	 */
1141 
1142 	tx = dmu_tx_create_assigned(spa_get_dsl(spa), txg);
1143 
1144 	if (smo->smo_object == 0) {
1145 		ASSERT(smo->smo_objsize == 0);
1146 		ASSERT(smo->smo_alloc == 0);
1147 		smo->smo_object = dmu_object_alloc(mos,
1148 		    DMU_OT_SPACE_MAP, 1 << SPACE_MAP_BLOCKSHIFT,
1149 		    DMU_OT_SPACE_MAP_HEADER, sizeof (*smo), tx);
1150 		ASSERT(smo->smo_object != 0);
1151 		dmu_write(mos, vd->vdev_ms_array, sizeof (uint64_t) *
1152 		    (sm->sm_start >> vd->vdev_ms_shift),
1153 		    sizeof (uint64_t), &smo->smo_object, tx);
1154 	}
1155 
1156 	mutex_enter(&msp->ms_lock);
1157 
1158 	if (sm->sm_loaded && spa_sync_pass(spa) == 1 &&
1159 	    metaslab_should_condense(msp)) {
1160 		metaslab_condense(msp, txg, tx);
1161 	} else {
1162 		space_map_sync(allocmap, SM_ALLOC, smo, mos, tx);
1163 		space_map_sync(*freemap, SM_FREE, smo, mos, tx);
1164 	}
1165 
1166 	space_map_vacate(allocmap, NULL, NULL);
1167 
1168 	/*
1169 	 * For sync pass 1, we avoid walking the entire space map and
1170 	 * instead will just swap the pointers for freemap and
1171 	 * freed_map. We can safely do this since the freed_map is
1172 	 * guaranteed to be empty on the initial pass.
1173 	 */
1174 	if (spa_sync_pass(spa) == 1) {
1175 		ASSERT0((*freed_map)->sm_space);
1176 		ASSERT0(avl_numnodes(&(*freed_map)->sm_root));
1177 		space_map_swap(freemap, freed_map);
1178 	} else {
1179 		space_map_vacate(*freemap, space_map_add, *freed_map);
1180 	}
1181 
1182 	ASSERT0(msp->ms_allocmap[txg & TXG_MASK]->sm_space);
1183 	ASSERT0(msp->ms_freemap[txg & TXG_MASK]->sm_space);
1184 
1185 	mutex_exit(&msp->ms_lock);
1186 
1187 	VERIFY0(dmu_bonus_hold(mos, smo->smo_object, FTAG, &db));
1188 	dmu_buf_will_dirty(db, tx);
1189 	ASSERT3U(db->db_size, >=, sizeof (*smo));
1190 	bcopy(smo, db->db_data, sizeof (*smo));
1191 	dmu_buf_rele(db, FTAG);
1192 
1193 	dmu_tx_commit(tx);
1194 }
1195 
1196 /*
1197  * Called after a transaction group has completely synced to mark
1198  * all of the metaslab's free space as usable.
1199  */
1200 void
1201 metaslab_sync_done(metaslab_t *msp, uint64_t txg)
1202 {
1203 	space_map_obj_t *smo = &msp->ms_smo;
1204 	space_map_obj_t *smosync = &msp->ms_smo_syncing;
1205 	space_map_t *sm = msp->ms_map;
1206 	space_map_t **freed_map = &msp->ms_freemap[TXG_CLEAN(txg) & TXG_MASK];
1207 	space_map_t **defer_map = &msp->ms_defermap[txg % TXG_DEFER_SIZE];
1208 	metaslab_group_t *mg = msp->ms_group;
1209 	vdev_t *vd = mg->mg_vd;
1210 	int64_t alloc_delta, defer_delta;
1211 
1212 	ASSERT(!vd->vdev_ishole);
1213 
1214 	mutex_enter(&msp->ms_lock);
1215 
1216 	/*
1217 	 * If this metaslab is just becoming available, initialize its
1218 	 * allocmaps, freemaps, and defermap and add its capacity to the vdev.
1219 	 */
1220 	if (*freed_map == NULL) {
1221 		ASSERT(*defer_map == NULL);
1222 		for (int t = 0; t < TXG_SIZE; t++) {
1223 			msp->ms_allocmap[t] = kmem_zalloc(sizeof (space_map_t),
1224 			    KM_SLEEP);
1225 			space_map_create(msp->ms_allocmap[t], sm->sm_start,
1226 			    sm->sm_size, sm->sm_shift, sm->sm_lock);
1227 			msp->ms_freemap[t] = kmem_zalloc(sizeof (space_map_t),
1228 			    KM_SLEEP);
1229 			space_map_create(msp->ms_freemap[t], sm->sm_start,
1230 			    sm->sm_size, sm->sm_shift, sm->sm_lock);
1231 		}
1232 
1233 		for (int t = 0; t < TXG_DEFER_SIZE; t++) {
1234 			msp->ms_defermap[t] = kmem_zalloc(sizeof (space_map_t),
1235 			    KM_SLEEP);
1236 			space_map_create(msp->ms_defermap[t], sm->sm_start,
1237 			    sm->sm_size, sm->sm_shift, sm->sm_lock);
1238 		}
1239 
1240 		freed_map = &msp->ms_freemap[TXG_CLEAN(txg) & TXG_MASK];
1241 		defer_map = &msp->ms_defermap[txg % TXG_DEFER_SIZE];
1242 
1243 		vdev_space_update(vd, 0, 0, sm->sm_size);
1244 	}
1245 
1246 	alloc_delta = smosync->smo_alloc - smo->smo_alloc;
1247 	defer_delta = (*freed_map)->sm_space - (*defer_map)->sm_space;
1248 
1249 	vdev_space_update(vd, alloc_delta + defer_delta, defer_delta, 0);
1250 
1251 	ASSERT(msp->ms_allocmap[txg & TXG_MASK]->sm_space == 0);
1252 	ASSERT(msp->ms_freemap[txg & TXG_MASK]->sm_space == 0);
1253 
1254 	/*
1255 	 * If there's a space_map_load() in progress, wait for it to complete
1256 	 * so that we have a consistent view of the in-core space map.
1257 	 */
1258 	space_map_load_wait(sm);
1259 
1260 	/*
1261 	 * Move the frees from the defer_map to this map (if it's loaded).
1262 	 * Swap the freed_map and the defer_map -- this is safe to do
1263 	 * because we've just emptied out the defer_map.
1264 	 */
1265 	space_map_vacate(*defer_map, sm->sm_loaded ? space_map_free : NULL, sm);
1266 	ASSERT0((*defer_map)->sm_space);
1267 	ASSERT0(avl_numnodes(&(*defer_map)->sm_root));
1268 	space_map_swap(freed_map, defer_map);
1269 
1270 	*smo = *smosync;
1271 
1272 	msp->ms_deferspace += defer_delta;
1273 	ASSERT3S(msp->ms_deferspace, >=, 0);
1274 	ASSERT3S(msp->ms_deferspace, <=, sm->sm_size);
1275 	if (msp->ms_deferspace != 0) {
1276 		/*
1277 		 * Keep syncing this metaslab until all deferred frees
1278 		 * are back in circulation.
1279 		 */
1280 		vdev_dirty(vd, VDD_METASLAB, msp, txg + 1);
1281 	}
1282 
1283 	/*
1284 	 * If the map is loaded but no longer active, evict it as soon as all
1285 	 * future allocations have synced.  (If we unloaded it now and then
1286 	 * loaded a moment later, the map wouldn't reflect those allocations.)
1287 	 */
1288 	if (sm->sm_loaded && (msp->ms_weight & METASLAB_ACTIVE_MASK) == 0) {
1289 		int evictable = 1;
1290 
1291 		for (int t = 1; t < TXG_CONCURRENT_STATES; t++)
1292 			if (msp->ms_allocmap[(txg + t) & TXG_MASK]->sm_space)
1293 				evictable = 0;
1294 
1295 		if (evictable && !metaslab_debug)
1296 			space_map_unload(sm);
1297 	}
1298 
1299 	metaslab_group_sort(mg, msp, metaslab_weight(msp));
1300 
1301 	mutex_exit(&msp->ms_lock);
1302 }
1303 
1304 void
1305 metaslab_sync_reassess(metaslab_group_t *mg)
1306 {
1307 	vdev_t *vd = mg->mg_vd;
1308 	int64_t failures = mg->mg_alloc_failures;
1309 
1310 	/*
1311 	 * Re-evaluate all metaslabs which have lower offsets than the
1312 	 * bonus area.
1313 	 */
1314 	for (int m = 0; m < vd->vdev_ms_count; m++) {
1315 		metaslab_t *msp = vd->vdev_ms[m];
1316 
1317 		if (msp->ms_map->sm_start > mg->mg_bonus_area)
1318 			break;
1319 
1320 		mutex_enter(&msp->ms_lock);
1321 		metaslab_group_sort(mg, msp, metaslab_weight(msp));
1322 		mutex_exit(&msp->ms_lock);
1323 	}
1324 
1325 	atomic_add_64(&mg->mg_alloc_failures, -failures);
1326 
1327 	/*
1328 	 * Prefetch the next potential metaslabs
1329 	 */
1330 	metaslab_prefetch(mg);
1331 }
1332 
1333 static uint64_t
1334 metaslab_distance(metaslab_t *msp, dva_t *dva)
1335 {
1336 	uint64_t ms_shift = msp->ms_group->mg_vd->vdev_ms_shift;
1337 	uint64_t offset = DVA_GET_OFFSET(dva) >> ms_shift;
1338 	uint64_t start = msp->ms_map->sm_start >> ms_shift;
1339 
1340 	if (msp->ms_group->mg_vd->vdev_id != DVA_GET_VDEV(dva))
1341 		return (1ULL << 63);
1342 
1343 	if (offset < start)
1344 		return ((start - offset) << ms_shift);
1345 	if (offset > start)
1346 		return ((offset - start) << ms_shift);
1347 	return (0);
1348 }
1349 
1350 static uint64_t
1351 metaslab_group_alloc(metaslab_group_t *mg, uint64_t psize, uint64_t asize,
1352     uint64_t txg, uint64_t min_distance, dva_t *dva, int d, int flags)
1353 {
1354 	spa_t *spa = mg->mg_vd->vdev_spa;
1355 	metaslab_t *msp = NULL;
1356 	uint64_t offset = -1ULL;
1357 	avl_tree_t *t = &mg->mg_metaslab_tree;
1358 	uint64_t activation_weight;
1359 	uint64_t target_distance;
1360 	int i;
1361 
1362 	activation_weight = METASLAB_WEIGHT_PRIMARY;
1363 	for (i = 0; i < d; i++) {
1364 		if (DVA_GET_VDEV(&dva[i]) == mg->mg_vd->vdev_id) {
1365 			activation_weight = METASLAB_WEIGHT_SECONDARY;
1366 			break;
1367 		}
1368 	}
1369 
1370 	for (;;) {
1371 		boolean_t was_active;
1372 
1373 		mutex_enter(&mg->mg_lock);
1374 		for (msp = avl_first(t); msp; msp = AVL_NEXT(t, msp)) {
1375 			if (msp->ms_weight < asize) {
1376 				spa_dbgmsg(spa, "%s: failed to meet weight "
1377 				    "requirement: vdev %llu, txg %llu, mg %p, "
1378 				    "msp %p, psize %llu, asize %llu, "
1379 				    "failures %llu, weight %llu",
1380 				    spa_name(spa), mg->mg_vd->vdev_id, txg,
1381 				    mg, msp, psize, asize,
1382 				    mg->mg_alloc_failures, msp->ms_weight);
1383 				mutex_exit(&mg->mg_lock);
1384 				return (-1ULL);
1385 			}
1386 			was_active = msp->ms_weight & METASLAB_ACTIVE_MASK;
1387 			if (activation_weight == METASLAB_WEIGHT_PRIMARY)
1388 				break;
1389 
1390 			target_distance = min_distance +
1391 			    (msp->ms_smo.smo_alloc ? 0 : min_distance >> 1);
1392 
1393 			for (i = 0; i < d; i++)
1394 				if (metaslab_distance(msp, &dva[i]) <
1395 				    target_distance)
1396 					break;
1397 			if (i == d)
1398 				break;
1399 		}
1400 		mutex_exit(&mg->mg_lock);
1401 		if (msp == NULL)
1402 			return (-1ULL);
1403 
1404 		/*
1405 		 * If we've already reached the allowable number of failed
1406 		 * allocation attempts on this metaslab group then we
1407 		 * consider skipping it. We skip it only if we're allowed
1408 		 * to "fast" gang, the physical size is larger than
1409 		 * a gang block, and we're attempting to allocate from
1410 		 * the primary metaslab.
1411 		 */
1412 		if (mg->mg_alloc_failures > zfs_mg_alloc_failures &&
1413 		    CAN_FASTGANG(flags) && psize > SPA_GANGBLOCKSIZE &&
1414 		    activation_weight == METASLAB_WEIGHT_PRIMARY) {
1415 			spa_dbgmsg(spa, "%s: skipping metaslab group: "
1416 			    "vdev %llu, txg %llu, mg %p, psize %llu, "
1417 			    "asize %llu, failures %llu", spa_name(spa),
1418 			    mg->mg_vd->vdev_id, txg, mg, psize, asize,
1419 			    mg->mg_alloc_failures);
1420 			return (-1ULL);
1421 		}
1422 
1423 		mutex_enter(&msp->ms_lock);
1424 
1425 		/*
1426 		 * If this metaslab is currently condensing then pick again as
1427 		 * we can't manipulate this metaslab until it's committed
1428 		 * to disk.
1429 		 */
1430 		if (msp->ms_map->sm_condensing) {
1431 			mutex_exit(&msp->ms_lock);
1432 			continue;
1433 		}
1434 
1435 		/*
1436 		 * Ensure that the metaslab we have selected is still
1437 		 * capable of handling our request. It's possible that
1438 		 * another thread may have changed the weight while we
1439 		 * were blocked on the metaslab lock.
1440 		 */
1441 		if (msp->ms_weight < asize || (was_active &&
1442 		    !(msp->ms_weight & METASLAB_ACTIVE_MASK) &&
1443 		    activation_weight == METASLAB_WEIGHT_PRIMARY)) {
1444 			mutex_exit(&msp->ms_lock);
1445 			continue;
1446 		}
1447 
1448 		if ((msp->ms_weight & METASLAB_WEIGHT_SECONDARY) &&
1449 		    activation_weight == METASLAB_WEIGHT_PRIMARY) {
1450 			metaslab_passivate(msp,
1451 			    msp->ms_weight & ~METASLAB_ACTIVE_MASK);
1452 			mutex_exit(&msp->ms_lock);
1453 			continue;
1454 		}
1455 
1456 		if (metaslab_activate(msp, activation_weight) != 0) {
1457 			mutex_exit(&msp->ms_lock);
1458 			continue;
1459 		}
1460 
1461 		if ((offset = space_map_alloc(msp->ms_map, asize)) != -1ULL)
1462 			break;
1463 
1464 		atomic_inc_64(&mg->mg_alloc_failures);
1465 
1466 		metaslab_passivate(msp, space_map_maxsize(msp->ms_map));
1467 
1468 		mutex_exit(&msp->ms_lock);
1469 	}
1470 
1471 	if (msp->ms_allocmap[txg & TXG_MASK]->sm_space == 0)
1472 		vdev_dirty(mg->mg_vd, VDD_METASLAB, msp, txg);
1473 
1474 	space_map_add(msp->ms_allocmap[txg & TXG_MASK], offset, asize);
1475 
1476 	mutex_exit(&msp->ms_lock);
1477 
1478 	return (offset);
1479 }
1480 
1481 /*
1482  * Allocate a block for the specified i/o.
1483  */
1484 static int
1485 metaslab_alloc_dva(spa_t *spa, metaslab_class_t *mc, uint64_t psize,
1486     dva_t *dva, int d, dva_t *hintdva, uint64_t txg, int flags)
1487 {
1488 	metaslab_group_t *mg, *rotor;
1489 	vdev_t *vd;
1490 	int dshift = 3;
1491 	int all_zero;
1492 	int zio_lock = B_FALSE;
1493 	boolean_t allocatable;
1494 	uint64_t offset = -1ULL;
1495 	uint64_t asize;
1496 	uint64_t distance;
1497 
1498 	ASSERT(!DVA_IS_VALID(&dva[d]));
1499 
1500 	/*
1501 	 * For testing, make some blocks above a certain size be gang blocks.
1502 	 */
1503 	if (psize >= metaslab_gang_bang && (ddi_get_lbolt() & 3) == 0)
1504 		return (ENOSPC);
1505 
1506 	/*
1507 	 * Start at the rotor and loop through all mgs until we find something.
1508 	 * Note that there's no locking on mc_rotor or mc_aliquot because
1509 	 * nothing actually breaks if we miss a few updates -- we just won't
1510 	 * allocate quite as evenly.  It all balances out over time.
1511 	 *
1512 	 * If we are doing ditto or log blocks, try to spread them across
1513 	 * consecutive vdevs.  If we're forced to reuse a vdev before we've
1514 	 * allocated all of our ditto blocks, then try and spread them out on
1515 	 * that vdev as much as possible.  If it turns out to not be possible,
1516 	 * gradually lower our standards until anything becomes acceptable.
1517 	 * Also, allocating on consecutive vdevs (as opposed to random vdevs)
1518 	 * gives us hope of containing our fault domains to something we're
1519 	 * able to reason about.  Otherwise, any two top-level vdev failures
1520 	 * will guarantee the loss of data.  With consecutive allocation,
1521 	 * only two adjacent top-level vdev failures will result in data loss.
1522 	 *
1523 	 * If we are doing gang blocks (hintdva is non-NULL), try to keep
1524 	 * ourselves on the same vdev as our gang block header.  That
1525 	 * way, we can hope for locality in vdev_cache, plus it makes our
1526 	 * fault domains something tractable.
1527 	 */
1528 	if (hintdva) {
1529 		vd = vdev_lookup_top(spa, DVA_GET_VDEV(&hintdva[d]));
1530 
1531 		/*
1532 		 * It's possible the vdev we're using as the hint no
1533 		 * longer exists (i.e. removed). Consult the rotor when
1534 		 * all else fails.
1535 		 */
1536 		if (vd != NULL) {
1537 			mg = vd->vdev_mg;
1538 
1539 			if (flags & METASLAB_HINTBP_AVOID &&
1540 			    mg->mg_next != NULL)
1541 				mg = mg->mg_next;
1542 		} else {
1543 			mg = mc->mc_rotor;
1544 		}
1545 	} else if (d != 0) {
1546 		vd = vdev_lookup_top(spa, DVA_GET_VDEV(&dva[d - 1]));
1547 		mg = vd->vdev_mg->mg_next;
1548 	} else {
1549 		mg = mc->mc_rotor;
1550 	}
1551 
1552 	/*
1553 	 * If the hint put us into the wrong metaslab class, or into a
1554 	 * metaslab group that has been passivated, just follow the rotor.
1555 	 */
1556 	if (mg->mg_class != mc || mg->mg_activation_count <= 0)
1557 		mg = mc->mc_rotor;
1558 
1559 	rotor = mg;
1560 top:
1561 	all_zero = B_TRUE;
1562 	do {
1563 		ASSERT(mg->mg_activation_count == 1);
1564 
1565 		vd = mg->mg_vd;
1566 
1567 		/*
1568 		 * Don't allocate from faulted devices.
1569 		 */
1570 		if (zio_lock) {
1571 			spa_config_enter(spa, SCL_ZIO, FTAG, RW_READER);
1572 			allocatable = vdev_allocatable(vd);
1573 			spa_config_exit(spa, SCL_ZIO, FTAG);
1574 		} else {
1575 			allocatable = vdev_allocatable(vd);
1576 		}
1577 		if (!allocatable)
1578 			goto next;
1579 
1580 		/*
1581 		 * Avoid writing single-copy data to a failing vdev
1582 		 * unless the user instructs us that it is okay.
1583 		 */
1584 		if ((vd->vdev_stat.vs_write_errors > 0 ||
1585 		    vd->vdev_state < VDEV_STATE_HEALTHY) &&
1586 		    d == 0 && dshift == 3 &&
1587 		    !(zfs_write_to_degraded && vd->vdev_state ==
1588 		    VDEV_STATE_DEGRADED)) {
1589 			all_zero = B_FALSE;
1590 			goto next;
1591 		}
1592 
1593 		ASSERT(mg->mg_class == mc);
1594 
1595 		distance = vd->vdev_asize >> dshift;
1596 		if (distance <= (1ULL << vd->vdev_ms_shift))
1597 			distance = 0;
1598 		else
1599 			all_zero = B_FALSE;
1600 
1601 		asize = vdev_psize_to_asize(vd, psize);
1602 		ASSERT(P2PHASE(asize, 1ULL << vd->vdev_ashift) == 0);
1603 
1604 		offset = metaslab_group_alloc(mg, psize, asize, txg, distance,
1605 		    dva, d, flags);
1606 		if (offset != -1ULL) {
1607 			/*
1608 			 * If we've just selected this metaslab group,
1609 			 * figure out whether the corresponding vdev is
1610 			 * over- or under-used relative to the pool,
1611 			 * and set an allocation bias to even it out.
1612 			 */
1613 			if (mc->mc_aliquot == 0) {
1614 				vdev_stat_t *vs = &vd->vdev_stat;
1615 				int64_t vu, cu;
1616 
1617 				vu = (vs->vs_alloc * 100) / (vs->vs_space + 1);
1618 				cu = (mc->mc_alloc * 100) / (mc->mc_space + 1);
1619 
1620 				/*
1621 				 * Calculate how much more or less we should
1622 				 * try to allocate from this device during
1623 				 * this iteration around the rotor.
1624 				 * For example, if a device is 80% full
1625 				 * and the pool is 20% full then we should
1626 				 * reduce allocations by 60% on this device.
1627 				 *
1628 				 * mg_bias = (20 - 80) * 512K / 100 = -307K
1629 				 *
1630 				 * This reduces allocations by 307K for this
1631 				 * iteration.
1632 				 */
1633 				mg->mg_bias = ((cu - vu) *
1634 				    (int64_t)mg->mg_aliquot) / 100;
1635 			}
1636 
1637 			if (atomic_add_64_nv(&mc->mc_aliquot, asize) >=
1638 			    mg->mg_aliquot + mg->mg_bias) {
1639 				mc->mc_rotor = mg->mg_next;
1640 				mc->mc_aliquot = 0;
1641 			}
1642 
1643 			DVA_SET_VDEV(&dva[d], vd->vdev_id);
1644 			DVA_SET_OFFSET(&dva[d], offset);
1645 			DVA_SET_GANG(&dva[d], !!(flags & METASLAB_GANG_HEADER));
1646 			DVA_SET_ASIZE(&dva[d], asize);
1647 
1648 			return (0);
1649 		}
1650 next:
1651 		mc->mc_rotor = mg->mg_next;
1652 		mc->mc_aliquot = 0;
1653 	} while ((mg = mg->mg_next) != rotor);
1654 
1655 	if (!all_zero) {
1656 		dshift++;
1657 		ASSERT(dshift < 64);
1658 		goto top;
1659 	}
1660 
1661 	if (!allocatable && !zio_lock) {
1662 		dshift = 3;
1663 		zio_lock = B_TRUE;
1664 		goto top;
1665 	}
1666 
1667 	bzero(&dva[d], sizeof (dva_t));
1668 
1669 	return (ENOSPC);
1670 }
1671 
1672 /*
1673  * Free the block represented by DVA in the context of the specified
1674  * transaction group.
1675  */
1676 static void
1677 metaslab_free_dva(spa_t *spa, const dva_t *dva, uint64_t txg, boolean_t now)
1678 {
1679 	uint64_t vdev = DVA_GET_VDEV(dva);
1680 	uint64_t offset = DVA_GET_OFFSET(dva);
1681 	uint64_t size = DVA_GET_ASIZE(dva);
1682 	vdev_t *vd;
1683 	metaslab_t *msp;
1684 
1685 	ASSERT(DVA_IS_VALID(dva));
1686 
1687 	if (txg > spa_freeze_txg(spa))
1688 		return;
1689 
1690 	if ((vd = vdev_lookup_top(spa, vdev)) == NULL ||
1691 	    (offset >> vd->vdev_ms_shift) >= vd->vdev_ms_count) {
1692 		cmn_err(CE_WARN, "metaslab_free_dva(): bad DVA %llu:%llu",
1693 		    (u_longlong_t)vdev, (u_longlong_t)offset);
1694 		ASSERT(0);
1695 		return;
1696 	}
1697 
1698 	msp = vd->vdev_ms[offset >> vd->vdev_ms_shift];
1699 
1700 	if (DVA_GET_GANG(dva))
1701 		size = vdev_psize_to_asize(vd, SPA_GANGBLOCKSIZE);
1702 
1703 	mutex_enter(&msp->ms_lock);
1704 
1705 	if (now) {
1706 		space_map_remove(msp->ms_allocmap[txg & TXG_MASK],
1707 		    offset, size);
1708 		space_map_free(msp->ms_map, offset, size);
1709 	} else {
1710 		if (msp->ms_freemap[txg & TXG_MASK]->sm_space == 0)
1711 			vdev_dirty(vd, VDD_METASLAB, msp, txg);
1712 		space_map_add(msp->ms_freemap[txg & TXG_MASK], offset, size);
1713 	}
1714 
1715 	mutex_exit(&msp->ms_lock);
1716 }
1717 
1718 /*
1719  * Intent log support: upon opening the pool after a crash, notify the SPA
1720  * of blocks that the intent log has allocated for immediate write, but
1721  * which are still considered free by the SPA because the last transaction
1722  * group didn't commit yet.
1723  */
1724 static int
1725 metaslab_claim_dva(spa_t *spa, const dva_t *dva, uint64_t txg)
1726 {
1727 	uint64_t vdev = DVA_GET_VDEV(dva);
1728 	uint64_t offset = DVA_GET_OFFSET(dva);
1729 	uint64_t size = DVA_GET_ASIZE(dva);
1730 	vdev_t *vd;
1731 	metaslab_t *msp;
1732 	int error = 0;
1733 
1734 	ASSERT(DVA_IS_VALID(dva));
1735 
1736 	if ((vd = vdev_lookup_top(spa, vdev)) == NULL ||
1737 	    (offset >> vd->vdev_ms_shift) >= vd->vdev_ms_count)
1738 		return (ENXIO);
1739 
1740 	msp = vd->vdev_ms[offset >> vd->vdev_ms_shift];
1741 
1742 	if (DVA_GET_GANG(dva))
1743 		size = vdev_psize_to_asize(vd, SPA_GANGBLOCKSIZE);
1744 
1745 	mutex_enter(&msp->ms_lock);
1746 
1747 	if ((txg != 0 && spa_writeable(spa)) || !msp->ms_map->sm_loaded)
1748 		error = metaslab_activate(msp, METASLAB_WEIGHT_SECONDARY);
1749 
1750 	if (error == 0 && !space_map_contains(msp->ms_map, offset, size))
1751 		error = ENOENT;
1752 
1753 	if (error || txg == 0) {	/* txg == 0 indicates dry run */
1754 		mutex_exit(&msp->ms_lock);
1755 		return (error);
1756 	}
1757 
1758 	space_map_claim(msp->ms_map, offset, size);
1759 
1760 	if (spa_writeable(spa)) {	/* don't dirty if we're zdb(1M) */
1761 		if (msp->ms_allocmap[txg & TXG_MASK]->sm_space == 0)
1762 			vdev_dirty(vd, VDD_METASLAB, msp, txg);
1763 		space_map_add(msp->ms_allocmap[txg & TXG_MASK], offset, size);
1764 	}
1765 
1766 	mutex_exit(&msp->ms_lock);
1767 
1768 	return (0);
1769 }
1770 
1771 int
1772 metaslab_alloc(spa_t *spa, metaslab_class_t *mc, uint64_t psize, blkptr_t *bp,
1773     int ndvas, uint64_t txg, blkptr_t *hintbp, int flags)
1774 {
1775 	dva_t *dva = bp->blk_dva;
1776 	dva_t *hintdva = hintbp->blk_dva;
1777 	int error = 0;
1778 
1779 	ASSERT(bp->blk_birth == 0);
1780 	ASSERT(BP_PHYSICAL_BIRTH(bp) == 0);
1781 
1782 	spa_config_enter(spa, SCL_ALLOC, FTAG, RW_READER);
1783 
1784 	if (mc->mc_rotor == NULL) {	/* no vdevs in this class */
1785 		spa_config_exit(spa, SCL_ALLOC, FTAG);
1786 		return (ENOSPC);
1787 	}
1788 
1789 	ASSERT(ndvas > 0 && ndvas <= spa_max_replication(spa));
1790 	ASSERT(BP_GET_NDVAS(bp) == 0);
1791 	ASSERT(hintbp == NULL || ndvas <= BP_GET_NDVAS(hintbp));
1792 
1793 	for (int d = 0; d < ndvas; d++) {
1794 		error = metaslab_alloc_dva(spa, mc, psize, dva, d, hintdva,
1795 		    txg, flags);
1796 		if (error) {
1797 			for (d--; d >= 0; d--) {
1798 				metaslab_free_dva(spa, &dva[d], txg, B_TRUE);
1799 				bzero(&dva[d], sizeof (dva_t));
1800 			}
1801 			spa_config_exit(spa, SCL_ALLOC, FTAG);
1802 			return (error);
1803 		}
1804 	}
1805 	ASSERT(error == 0);
1806 	ASSERT(BP_GET_NDVAS(bp) == ndvas);
1807 
1808 	spa_config_exit(spa, SCL_ALLOC, FTAG);
1809 
1810 	BP_SET_BIRTH(bp, txg, txg);
1811 
1812 	return (0);
1813 }
1814 
1815 void
1816 metaslab_free(spa_t *spa, const blkptr_t *bp, uint64_t txg, boolean_t now)
1817 {
1818 	const dva_t *dva = bp->blk_dva;
1819 	int ndvas = BP_GET_NDVAS(bp);
1820 
1821 	ASSERT(!BP_IS_HOLE(bp));
1822 	ASSERT(!now || bp->blk_birth >= spa_syncing_txg(spa));
1823 
1824 	spa_config_enter(spa, SCL_FREE, FTAG, RW_READER);
1825 
1826 	for (int d = 0; d < ndvas; d++)
1827 		metaslab_free_dva(spa, &dva[d], txg, now);
1828 
1829 	spa_config_exit(spa, SCL_FREE, FTAG);
1830 }
1831 
1832 int
1833 metaslab_claim(spa_t *spa, const blkptr_t *bp, uint64_t txg)
1834 {
1835 	const dva_t *dva = bp->blk_dva;
1836 	int ndvas = BP_GET_NDVAS(bp);
1837 	int error = 0;
1838 
1839 	ASSERT(!BP_IS_HOLE(bp));
1840 
1841 	if (txg != 0) {
1842 		/*
1843 		 * First do a dry run to make sure all DVAs are claimable,
1844 		 * so we don't have to unwind from partial failures below.
1845 		 */
1846 		if ((error = metaslab_claim(spa, bp, 0)) != 0)
1847 			return (error);
1848 	}
1849 
1850 	spa_config_enter(spa, SCL_ALLOC, FTAG, RW_READER);
1851 
1852 	for (int d = 0; d < ndvas; d++)
1853 		if ((error = metaslab_claim_dva(spa, &dva[d], txg)) != 0)
1854 			break;
1855 
1856 	spa_config_exit(spa, SCL_ALLOC, FTAG);
1857 
1858 	ASSERT(error == 0 || txg == 0);
1859 
1860 	return (error);
1861 }
1862