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 2009 Sun Microsystems, Inc. All rights reserved.
23 * Use is subject to license terms.
24 */
25 /*
26 * Copyright (c) 2012, 2019 by Delphix. All rights reserved.
27 */
28
29 #include <sys/zfs_context.h>
30 #include <sys/spa.h>
31 #include <sys/dmu.h>
32 #include <sys/dmu_tx.h>
33 #include <sys/dnode.h>
34 #include <sys/dsl_pool.h>
35 #include <sys/zio.h>
36 #include <sys/space_map.h>
37 #include <sys/zfeature.h>
38
39 /*
40 * Note on space map block size:
41 *
42 * The data for a given space map can be kept on blocks of any size.
43 * Larger blocks entail fewer I/O operations, but they also cause the
44 * DMU to keep more data in-core, and also to waste more I/O bandwidth
45 * when only a few blocks have changed since the last transaction group.
46 */
47
48 /*
49 * Enabled whenever we want to stress test the use of double-word
50 * space map entries.
51 */
52 boolean_t zfs_force_some_double_word_sm_entries = B_FALSE;
53
54 /*
55 * Override the default indirect block size of 128K, instead use 16K for
56 * spacemaps (2^14 bytes). This dramatically reduces write inflation since
57 * appending to a spacemap typically has to write one data block (4KB) and one
58 * or two indirect blocks (16K-32K, rather than 128K).
59 */
60 int space_map_ibs = 14;
61
62 boolean_t
sm_entry_is_debug(uint64_t e)63 sm_entry_is_debug(uint64_t e)
64 {
65 return (SM_PREFIX_DECODE(e) == SM_DEBUG_PREFIX);
66 }
67
68 boolean_t
sm_entry_is_single_word(uint64_t e)69 sm_entry_is_single_word(uint64_t e)
70 {
71 uint8_t prefix = SM_PREFIX_DECODE(e);
72 return (prefix != SM_DEBUG_PREFIX && prefix != SM2_PREFIX);
73 }
74
75 boolean_t
sm_entry_is_double_word(uint64_t e)76 sm_entry_is_double_word(uint64_t e)
77 {
78 return (SM_PREFIX_DECODE(e) == SM2_PREFIX);
79 }
80
81 /*
82 * Iterate through the space map, invoking the callback on each (non-debug)
83 * space map entry. Stop after reading 'end' bytes of the space map.
84 */
85 int
space_map_iterate(space_map_t * sm,uint64_t end,sm_cb_t callback,void * arg)86 space_map_iterate(space_map_t *sm, uint64_t end, sm_cb_t callback, void *arg)
87 {
88 uint64_t blksz = sm->sm_blksz;
89
90 ASSERT3U(blksz, !=, 0);
91 ASSERT3U(end, <=, space_map_length(sm));
92 ASSERT0(P2PHASE(end, sizeof (uint64_t)));
93
94 dmu_prefetch(sm->sm_os, space_map_object(sm), 0, 0, end,
95 ZIO_PRIORITY_SYNC_READ);
96
97 int error = 0;
98 uint64_t txg = 0, sync_pass = 0;
99 for (uint64_t block_base = 0; block_base < end && error == 0;
100 block_base += blksz) {
101 dmu_buf_t *db;
102 error = dmu_buf_hold(sm->sm_os, space_map_object(sm),
103 block_base, FTAG, &db, DMU_READ_PREFETCH);
104 if (error != 0)
105 return (error);
106
107 uint64_t *block_start = db->db_data;
108 uint64_t block_length = MIN(end - block_base, blksz);
109 uint64_t *block_end = block_start +
110 (block_length / sizeof (uint64_t));
111
112 VERIFY0(P2PHASE(block_length, sizeof (uint64_t)));
113 VERIFY3U(block_length, !=, 0);
114 ASSERT3U(blksz, ==, db->db_size);
115
116 for (uint64_t *block_cursor = block_start;
117 block_cursor < block_end && error == 0; block_cursor++) {
118 uint64_t e = *block_cursor;
119
120 if (sm_entry_is_debug(e)) {
121 /*
122 * Debug entries are only needed to record the
123 * current TXG and sync pass if available.
124 *
125 * Note though that sometimes there can be
126 * debug entries that are used as padding
127 * at the end of space map blocks in-order
128 * to not split a double-word entry in the
129 * middle between two blocks. These entries
130 * have their TXG field set to 0 and we
131 * skip them without recording the TXG.
132 * [see comment in space_map_write_seg()]
133 */
134 uint64_t e_txg = SM_DEBUG_TXG_DECODE(e);
135 if (e_txg != 0) {
136 txg = e_txg;
137 sync_pass = SM_DEBUG_SYNCPASS_DECODE(e);
138 } else {
139 ASSERT0(SM_DEBUG_SYNCPASS_DECODE(e));
140 }
141 continue;
142 }
143
144 uint64_t raw_offset, raw_run, vdev_id;
145 maptype_t type;
146 if (sm_entry_is_single_word(e)) {
147 type = SM_TYPE_DECODE(e);
148 vdev_id = SM_NO_VDEVID;
149 raw_offset = SM_OFFSET_DECODE(e);
150 raw_run = SM_RUN_DECODE(e);
151 } else {
152 /* it is a two-word entry */
153 ASSERT(sm_entry_is_double_word(e));
154 raw_run = SM2_RUN_DECODE(e);
155 vdev_id = SM2_VDEV_DECODE(e);
156
157 /* move on to the second word */
158 block_cursor++;
159 e = *block_cursor;
160 VERIFY3P(block_cursor, <=, block_end);
161
162 type = SM2_TYPE_DECODE(e);
163 raw_offset = SM2_OFFSET_DECODE(e);
164 }
165
166 uint64_t entry_offset = (raw_offset << sm->sm_shift) +
167 sm->sm_start;
168 uint64_t entry_run = raw_run << sm->sm_shift;
169
170 VERIFY0(P2PHASE(entry_offset, 1ULL << sm->sm_shift));
171 VERIFY0(P2PHASE(entry_run, 1ULL << sm->sm_shift));
172 ASSERT3U(entry_offset, >=, sm->sm_start);
173 ASSERT3U(entry_offset, <, sm->sm_start + sm->sm_size);
174 ASSERT3U(entry_run, <=, sm->sm_size);
175 ASSERT3U(entry_offset + entry_run, <=,
176 sm->sm_start + sm->sm_size);
177
178 space_map_entry_t sme = {
179 .sme_type = type,
180 .sme_vdev = vdev_id,
181 .sme_offset = entry_offset,
182 .sme_run = entry_run,
183 .sme_txg = txg,
184 .sme_sync_pass = sync_pass
185 };
186 error = callback(&sme, arg);
187 }
188 dmu_buf_rele(db, FTAG);
189 }
190 return (error);
191 }
192
193 /*
194 * Reads the entries from the last block of the space map into
195 * buf in reverse order. Populates nwords with number of words
196 * in the last block.
197 *
198 * Refer to block comment within space_map_incremental_destroy()
199 * to understand why this function is needed.
200 */
201 static int
space_map_reversed_last_block_entries(space_map_t * sm,uint64_t * buf,uint64_t bufsz,uint64_t * nwords)202 space_map_reversed_last_block_entries(space_map_t *sm, uint64_t *buf,
203 uint64_t bufsz, uint64_t *nwords)
204 {
205 int error = 0;
206 dmu_buf_t *db;
207
208 /*
209 * Find the offset of the last word in the space map and use
210 * that to read the last block of the space map with
211 * dmu_buf_hold().
212 */
213 uint64_t last_word_offset =
214 sm->sm_phys->smp_length - sizeof (uint64_t);
215 error = dmu_buf_hold(sm->sm_os, space_map_object(sm), last_word_offset,
216 FTAG, &db, DMU_READ_NO_PREFETCH);
217 if (error != 0)
218 return (error);
219
220 ASSERT3U(sm->sm_object, ==, db->db_object);
221 ASSERT3U(sm->sm_blksz, ==, db->db_size);
222 ASSERT3U(bufsz, >=, db->db_size);
223 ASSERT(nwords != NULL);
224
225 uint64_t *words = db->db_data;
226 *nwords =
227 (sm->sm_phys->smp_length - db->db_offset) / sizeof (uint64_t);
228
229 ASSERT3U(*nwords, <=, bufsz / sizeof (uint64_t));
230
231 uint64_t n = *nwords;
232 uint64_t j = n - 1;
233 for (uint64_t i = 0; i < n; i++) {
234 uint64_t entry = words[i];
235 if (sm_entry_is_double_word(entry)) {
236 /*
237 * Since we are populating the buffer backwards
238 * we have to be extra careful and add the two
239 * words of the double-word entry in the right
240 * order.
241 */
242 ASSERT3U(j, >, 0);
243 buf[j - 1] = entry;
244
245 i++;
246 ASSERT3U(i, <, n);
247 entry = words[i];
248 buf[j] = entry;
249 j -= 2;
250 } else {
251 ASSERT(sm_entry_is_debug(entry) ||
252 sm_entry_is_single_word(entry));
253 buf[j] = entry;
254 j--;
255 }
256 }
257
258 /*
259 * Assert that we wrote backwards all the
260 * way to the beginning of the buffer.
261 */
262 ASSERT3S(j, ==, -1);
263
264 dmu_buf_rele(db, FTAG);
265 return (error);
266 }
267
268 /*
269 * Note: This function performs destructive actions - specifically
270 * it deletes entries from the end of the space map. Thus, callers
271 * should ensure that they are holding the appropriate locks for
272 * the space map that they provide.
273 */
274 int
space_map_incremental_destroy(space_map_t * sm,sm_cb_t callback,void * arg,dmu_tx_t * tx)275 space_map_incremental_destroy(space_map_t *sm, sm_cb_t callback, void *arg,
276 dmu_tx_t *tx)
277 {
278 uint64_t bufsz = MAX(sm->sm_blksz, SPA_MINBLOCKSIZE);
279 uint64_t *buf = zio_buf_alloc(bufsz);
280
281 dmu_buf_will_dirty(sm->sm_dbuf, tx);
282
283 /*
284 * Ideally we would want to iterate from the beginning of the
285 * space map to the end in incremental steps. The issue with this
286 * approach is that we don't have any field on-disk that points
287 * us where to start between each step. We could try zeroing out
288 * entries that we've destroyed, but this doesn't work either as
289 * an entry that is 0 is a valid one (ALLOC for range [0x0:0x200]).
290 *
291 * As a result, we destroy its entries incrementally starting from
292 * the end after applying the callback to each of them.
293 *
294 * The problem with this approach is that we cannot literally
295 * iterate through the words in the space map backwards as we
296 * can't distinguish two-word space map entries from their second
297 * word. Thus we do the following:
298 *
299 * 1] We get all the entries from the last block of the space map
300 * and put them into a buffer in reverse order. This way the
301 * last entry comes first in the buffer, the second to last is
302 * second, etc.
303 * 2] We iterate through the entries in the buffer and we apply
304 * the callback to each one. As we move from entry to entry we
305 * we decrease the size of the space map, deleting effectively
306 * each entry.
307 * 3] If there are no more entries in the space map or the callback
308 * returns a value other than 0, we stop iterating over the
309 * space map. If there are entries remaining and the callback
310 * returned 0, we go back to step [1].
311 */
312 int error = 0;
313 while (space_map_length(sm) > 0 && error == 0) {
314 uint64_t nwords = 0;
315 error = space_map_reversed_last_block_entries(sm, buf, bufsz,
316 &nwords);
317 if (error != 0)
318 break;
319
320 ASSERT3U(nwords, <=, bufsz / sizeof (uint64_t));
321
322 for (uint64_t i = 0; i < nwords; i++) {
323 uint64_t e = buf[i];
324
325 if (sm_entry_is_debug(e)) {
326 sm->sm_phys->smp_length -= sizeof (uint64_t);
327 continue;
328 }
329
330 int words = 1;
331 uint64_t raw_offset, raw_run, vdev_id;
332 maptype_t type;
333 if (sm_entry_is_single_word(e)) {
334 type = SM_TYPE_DECODE(e);
335 vdev_id = SM_NO_VDEVID;
336 raw_offset = SM_OFFSET_DECODE(e);
337 raw_run = SM_RUN_DECODE(e);
338 } else {
339 ASSERT(sm_entry_is_double_word(e));
340 words = 2;
341
342 raw_run = SM2_RUN_DECODE(e);
343 vdev_id = SM2_VDEV_DECODE(e);
344
345 /* move to the second word */
346 i++;
347 e = buf[i];
348
349 ASSERT3P(i, <=, nwords);
350
351 type = SM2_TYPE_DECODE(e);
352 raw_offset = SM2_OFFSET_DECODE(e);
353 }
354
355 uint64_t entry_offset =
356 (raw_offset << sm->sm_shift) + sm->sm_start;
357 uint64_t entry_run = raw_run << sm->sm_shift;
358
359 VERIFY0(P2PHASE(entry_offset, 1ULL << sm->sm_shift));
360 VERIFY0(P2PHASE(entry_run, 1ULL << sm->sm_shift));
361 VERIFY3U(entry_offset, >=, sm->sm_start);
362 VERIFY3U(entry_offset, <, sm->sm_start + sm->sm_size);
363 VERIFY3U(entry_run, <=, sm->sm_size);
364 VERIFY3U(entry_offset + entry_run, <=,
365 sm->sm_start + sm->sm_size);
366
367 space_map_entry_t sme = {
368 .sme_type = type,
369 .sme_vdev = vdev_id,
370 .sme_offset = entry_offset,
371 .sme_run = entry_run
372 };
373 error = callback(&sme, arg);
374 if (error != 0)
375 break;
376
377 if (type == SM_ALLOC)
378 sm->sm_phys->smp_alloc -= entry_run;
379 else
380 sm->sm_phys->smp_alloc += entry_run;
381 sm->sm_phys->smp_length -= words * sizeof (uint64_t);
382 }
383 }
384
385 if (space_map_length(sm) == 0) {
386 ASSERT0(error);
387 ASSERT0(space_map_allocated(sm));
388 }
389
390 zio_buf_free(buf, bufsz);
391 return (error);
392 }
393
394 typedef struct space_map_load_arg {
395 space_map_t *smla_sm;
396 range_tree_t *smla_rt;
397 maptype_t smla_type;
398 } space_map_load_arg_t;
399
400 static int
space_map_load_callback(space_map_entry_t * sme,void * arg)401 space_map_load_callback(space_map_entry_t *sme, void *arg)
402 {
403 space_map_load_arg_t *smla = arg;
404 if (sme->sme_type == smla->smla_type) {
405 VERIFY3U(range_tree_space(smla->smla_rt) + sme->sme_run, <=,
406 smla->smla_sm->sm_size);
407 range_tree_add(smla->smla_rt, sme->sme_offset, sme->sme_run);
408 } else {
409 range_tree_remove(smla->smla_rt, sme->sme_offset, sme->sme_run);
410 }
411
412 return (0);
413 }
414
415 /*
416 * Load the spacemap into the rangetree, like space_map_load. But only
417 * read the first 'length' bytes of the spacemap.
418 */
419 int
space_map_load_length(space_map_t * sm,range_tree_t * rt,maptype_t maptype,uint64_t length)420 space_map_load_length(space_map_t *sm, range_tree_t *rt, maptype_t maptype,
421 uint64_t length)
422 {
423 space_map_load_arg_t smla;
424
425 VERIFY0(range_tree_space(rt));
426
427 if (maptype == SM_FREE)
428 range_tree_add(rt, sm->sm_start, sm->sm_size);
429
430 smla.smla_rt = rt;
431 smla.smla_sm = sm;
432 smla.smla_type = maptype;
433 int err = space_map_iterate(sm, length,
434 space_map_load_callback, &smla);
435
436 if (err != 0)
437 range_tree_vacate(rt, NULL, NULL);
438
439 return (err);
440 }
441
442 /*
443 * Load the space map disk into the specified range tree. Segments of maptype
444 * are added to the range tree, other segment types are removed.
445 */
446 int
space_map_load(space_map_t * sm,range_tree_t * rt,maptype_t maptype)447 space_map_load(space_map_t *sm, range_tree_t *rt, maptype_t maptype)
448 {
449 return (space_map_load_length(sm, rt, maptype, space_map_length(sm)));
450 }
451
452 void
space_map_histogram_clear(space_map_t * sm)453 space_map_histogram_clear(space_map_t *sm)
454 {
455 if (sm->sm_dbuf->db_size != sizeof (space_map_phys_t))
456 return;
457
458 memset(sm->sm_phys->smp_histogram, 0,
459 sizeof (sm->sm_phys->smp_histogram));
460 }
461
462 boolean_t
space_map_histogram_verify(space_map_t * sm,range_tree_t * rt)463 space_map_histogram_verify(space_map_t *sm, range_tree_t *rt)
464 {
465 /*
466 * Verify that the in-core range tree does not have any
467 * ranges smaller than our sm_shift size.
468 */
469 for (int i = 0; i < sm->sm_shift; i++) {
470 if (rt->rt_histogram[i] != 0)
471 return (B_FALSE);
472 }
473 return (B_TRUE);
474 }
475
476 void
space_map_histogram_add(space_map_t * sm,range_tree_t * rt,dmu_tx_t * tx)477 space_map_histogram_add(space_map_t *sm, range_tree_t *rt, dmu_tx_t *tx)
478 {
479 int idx = 0;
480
481 ASSERT(dmu_tx_is_syncing(tx));
482 VERIFY3U(space_map_object(sm), !=, 0);
483
484 if (sm->sm_dbuf->db_size != sizeof (space_map_phys_t))
485 return;
486
487 dmu_buf_will_dirty(sm->sm_dbuf, tx);
488
489 ASSERT(space_map_histogram_verify(sm, rt));
490 /*
491 * Transfer the content of the range tree histogram to the space
492 * map histogram. The space map histogram contains 32 buckets ranging
493 * between 2^sm_shift to 2^(32+sm_shift-1). The range tree,
494 * however, can represent ranges from 2^0 to 2^63. Since the space
495 * map only cares about allocatable blocks (minimum of sm_shift) we
496 * can safely ignore all ranges in the range tree smaller than sm_shift.
497 */
498 for (int i = sm->sm_shift; i < RANGE_TREE_HISTOGRAM_SIZE; i++) {
499
500 /*
501 * Since the largest histogram bucket in the space map is
502 * 2^(32+sm_shift-1), we need to normalize the values in
503 * the range tree for any bucket larger than that size. For
504 * example given an sm_shift of 9, ranges larger than 2^40
505 * would get normalized as if they were 1TB ranges. Assume
506 * the range tree had a count of 5 in the 2^44 (16TB) bucket,
507 * the calculation below would normalize this to 5 * 2^4 (16).
508 */
509 ASSERT3U(i, >=, idx + sm->sm_shift);
510 sm->sm_phys->smp_histogram[idx] +=
511 rt->rt_histogram[i] << (i - idx - sm->sm_shift);
512
513 /*
514 * Increment the space map's index as long as we haven't
515 * reached the maximum bucket size. Accumulate all ranges
516 * larger than the max bucket size into the last bucket.
517 */
518 if (idx < SPACE_MAP_HISTOGRAM_SIZE - 1) {
519 ASSERT3U(idx + sm->sm_shift, ==, i);
520 idx++;
521 ASSERT3U(idx, <, SPACE_MAP_HISTOGRAM_SIZE);
522 }
523 }
524 }
525
526 static void
space_map_write_intro_debug(space_map_t * sm,maptype_t maptype,dmu_tx_t * tx)527 space_map_write_intro_debug(space_map_t *sm, maptype_t maptype, dmu_tx_t *tx)
528 {
529 dmu_buf_will_dirty(sm->sm_dbuf, tx);
530
531 uint64_t dentry = SM_PREFIX_ENCODE(SM_DEBUG_PREFIX) |
532 SM_DEBUG_ACTION_ENCODE(maptype) |
533 SM_DEBUG_SYNCPASS_ENCODE(spa_sync_pass(tx->tx_pool->dp_spa)) |
534 SM_DEBUG_TXG_ENCODE(dmu_tx_get_txg(tx));
535
536 dmu_write(sm->sm_os, space_map_object(sm), sm->sm_phys->smp_length,
537 sizeof (dentry), &dentry, tx);
538
539 sm->sm_phys->smp_length += sizeof (dentry);
540 }
541
542 /*
543 * Writes one or more entries given a segment.
544 *
545 * Note: The function may release the dbuf from the pointer initially
546 * passed to it, and return a different dbuf. Also, the space map's
547 * dbuf must be dirty for the changes in sm_phys to take effect.
548 */
549 static void
space_map_write_seg(space_map_t * sm,uint64_t rstart,uint64_t rend,maptype_t maptype,uint64_t vdev_id,uint8_t words,dmu_buf_t ** dbp,const void * tag,dmu_tx_t * tx)550 space_map_write_seg(space_map_t *sm, uint64_t rstart, uint64_t rend,
551 maptype_t maptype, uint64_t vdev_id, uint8_t words, dmu_buf_t **dbp,
552 const void *tag, dmu_tx_t *tx)
553 {
554 ASSERT3U(words, !=, 0);
555 ASSERT3U(words, <=, 2);
556
557 /* ensure the vdev_id can be represented by the space map */
558 ASSERT3U(vdev_id, <=, SM_NO_VDEVID);
559
560 /*
561 * if this is a single word entry, ensure that no vdev was
562 * specified.
563 */
564 IMPLY(words == 1, vdev_id == SM_NO_VDEVID);
565
566 dmu_buf_t *db = *dbp;
567 ASSERT3U(db->db_size, ==, sm->sm_blksz);
568
569 uint64_t *block_base = db->db_data;
570 uint64_t *block_end = block_base + (sm->sm_blksz / sizeof (uint64_t));
571 uint64_t *block_cursor = block_base +
572 (sm->sm_phys->smp_length - db->db_offset) / sizeof (uint64_t);
573
574 ASSERT3P(block_cursor, <=, block_end);
575
576 uint64_t size = (rend - rstart) >> sm->sm_shift;
577 uint64_t start = (rstart - sm->sm_start) >> sm->sm_shift;
578 uint64_t run_max = (words == 2) ? SM2_RUN_MAX : SM_RUN_MAX;
579
580 ASSERT3U(rstart, >=, sm->sm_start);
581 ASSERT3U(rstart, <, sm->sm_start + sm->sm_size);
582 ASSERT3U(rend - rstart, <=, sm->sm_size);
583 ASSERT3U(rend, <=, sm->sm_start + sm->sm_size);
584
585 while (size != 0) {
586 ASSERT3P(block_cursor, <=, block_end);
587
588 /*
589 * If we are at the end of this block, flush it and start
590 * writing again from the beginning.
591 */
592 if (block_cursor == block_end) {
593 dmu_buf_rele(db, tag);
594
595 uint64_t next_word_offset = sm->sm_phys->smp_length;
596 VERIFY0(dmu_buf_hold(sm->sm_os,
597 space_map_object(sm), next_word_offset,
598 tag, &db, DMU_READ_PREFETCH));
599 dmu_buf_will_dirty(db, tx);
600
601 /* update caller's dbuf */
602 *dbp = db;
603
604 ASSERT3U(db->db_size, ==, sm->sm_blksz);
605
606 block_base = db->db_data;
607 block_cursor = block_base;
608 block_end = block_base +
609 (db->db_size / sizeof (uint64_t));
610 }
611
612 /*
613 * If we are writing a two-word entry and we only have one
614 * word left on this block, just pad it with an empty debug
615 * entry and write the two-word entry in the next block.
616 */
617 uint64_t *next_entry = block_cursor + 1;
618 if (next_entry == block_end && words > 1) {
619 ASSERT3U(words, ==, 2);
620 *block_cursor = SM_PREFIX_ENCODE(SM_DEBUG_PREFIX) |
621 SM_DEBUG_ACTION_ENCODE(0) |
622 SM_DEBUG_SYNCPASS_ENCODE(0) |
623 SM_DEBUG_TXG_ENCODE(0);
624 block_cursor++;
625 sm->sm_phys->smp_length += sizeof (uint64_t);
626 ASSERT3P(block_cursor, ==, block_end);
627 continue;
628 }
629
630 uint64_t run_len = MIN(size, run_max);
631 switch (words) {
632 case 1:
633 *block_cursor = SM_OFFSET_ENCODE(start) |
634 SM_TYPE_ENCODE(maptype) |
635 SM_RUN_ENCODE(run_len);
636 block_cursor++;
637 break;
638 case 2:
639 /* write the first word of the entry */
640 *block_cursor = SM_PREFIX_ENCODE(SM2_PREFIX) |
641 SM2_RUN_ENCODE(run_len) |
642 SM2_VDEV_ENCODE(vdev_id);
643 block_cursor++;
644
645 /* move on to the second word of the entry */
646 ASSERT3P(block_cursor, <, block_end);
647 *block_cursor = SM2_TYPE_ENCODE(maptype) |
648 SM2_OFFSET_ENCODE(start);
649 block_cursor++;
650 break;
651 default:
652 panic("%d-word space map entries are not supported",
653 words);
654 break;
655 }
656 sm->sm_phys->smp_length += words * sizeof (uint64_t);
657
658 start += run_len;
659 size -= run_len;
660 }
661 ASSERT0(size);
662
663 }
664
665 /*
666 * Note: The space map's dbuf must be dirty for the changes in sm_phys to
667 * take effect.
668 */
669 static void
space_map_write_impl(space_map_t * sm,range_tree_t * rt,maptype_t maptype,uint64_t vdev_id,dmu_tx_t * tx)670 space_map_write_impl(space_map_t *sm, range_tree_t *rt, maptype_t maptype,
671 uint64_t vdev_id, dmu_tx_t *tx)
672 {
673 spa_t *spa = tx->tx_pool->dp_spa;
674 dmu_buf_t *db;
675
676 space_map_write_intro_debug(sm, maptype, tx);
677
678 #ifdef ZFS_DEBUG
679 /*
680 * We do this right after we write the intro debug entry
681 * because the estimate does not take it into account.
682 */
683 uint64_t initial_objsize = sm->sm_phys->smp_length;
684 uint64_t estimated_growth =
685 space_map_estimate_optimal_size(sm, rt, SM_NO_VDEVID);
686 uint64_t estimated_final_objsize = initial_objsize + estimated_growth;
687 #endif
688
689 /*
690 * Find the offset right after the last word in the space map
691 * and use that to get a hold of the last block, so we can
692 * start appending to it.
693 */
694 uint64_t next_word_offset = sm->sm_phys->smp_length;
695 VERIFY0(dmu_buf_hold(sm->sm_os, space_map_object(sm),
696 next_word_offset, FTAG, &db, DMU_READ_PREFETCH));
697 ASSERT3U(db->db_size, ==, sm->sm_blksz);
698
699 dmu_buf_will_dirty(db, tx);
700
701 zfs_btree_t *t = &rt->rt_root;
702 zfs_btree_index_t where;
703 for (range_seg_t *rs = zfs_btree_first(t, &where); rs != NULL;
704 rs = zfs_btree_next(t, &where, &where)) {
705 uint64_t offset = (rs_get_start(rs, rt) - sm->sm_start) >>
706 sm->sm_shift;
707 uint64_t length = (rs_get_end(rs, rt) - rs_get_start(rs, rt)) >>
708 sm->sm_shift;
709 uint8_t words = 1;
710
711 /*
712 * We only write two-word entries when both of the following
713 * are true:
714 *
715 * [1] The feature is enabled.
716 * [2] The offset or run is too big for a single-word entry,
717 * or the vdev_id is set (meaning not equal to
718 * SM_NO_VDEVID).
719 *
720 * Note that for purposes of testing we've added the case that
721 * we write two-word entries occasionally when the feature is
722 * enabled and zfs_force_some_double_word_sm_entries has been
723 * set.
724 */
725 if (spa_feature_is_active(spa, SPA_FEATURE_SPACEMAP_V2) &&
726 (offset >= (1ULL << SM_OFFSET_BITS) ||
727 length > SM_RUN_MAX ||
728 vdev_id != SM_NO_VDEVID ||
729 (zfs_force_some_double_word_sm_entries &&
730 random_in_range(100) == 0)))
731 words = 2;
732
733 space_map_write_seg(sm, rs_get_start(rs, rt), rs_get_end(rs,
734 rt), maptype, vdev_id, words, &db, FTAG, tx);
735 }
736
737 dmu_buf_rele(db, FTAG);
738
739 #ifdef ZFS_DEBUG
740 /*
741 * We expect our estimation to be based on the worst case
742 * scenario [see comment in space_map_estimate_optimal_size()].
743 * Therefore we expect the actual objsize to be equal or less
744 * than whatever we estimated it to be.
745 */
746 ASSERT3U(estimated_final_objsize, >=, sm->sm_phys->smp_length);
747 #endif
748 }
749
750 /*
751 * Note: This function manipulates the state of the given space map but
752 * does not hold any locks implicitly. Thus the caller is responsible
753 * for synchronizing writes to the space map.
754 */
755 void
space_map_write(space_map_t * sm,range_tree_t * rt,maptype_t maptype,uint64_t vdev_id,dmu_tx_t * tx)756 space_map_write(space_map_t *sm, range_tree_t *rt, maptype_t maptype,
757 uint64_t vdev_id, dmu_tx_t *tx)
758 {
759 ASSERT(dsl_pool_sync_context(dmu_objset_pool(sm->sm_os)));
760 VERIFY3U(space_map_object(sm), !=, 0);
761
762 dmu_buf_will_dirty(sm->sm_dbuf, tx);
763
764 /*
765 * This field is no longer necessary since the in-core space map
766 * now contains the object number but is maintained for backwards
767 * compatibility.
768 */
769 sm->sm_phys->smp_object = sm->sm_object;
770
771 if (range_tree_is_empty(rt)) {
772 VERIFY3U(sm->sm_object, ==, sm->sm_phys->smp_object);
773 return;
774 }
775
776 if (maptype == SM_ALLOC)
777 sm->sm_phys->smp_alloc += range_tree_space(rt);
778 else
779 sm->sm_phys->smp_alloc -= range_tree_space(rt);
780
781 uint64_t nodes = zfs_btree_numnodes(&rt->rt_root);
782 uint64_t rt_space = range_tree_space(rt);
783
784 space_map_write_impl(sm, rt, maptype, vdev_id, tx);
785
786 /*
787 * Ensure that the space_map's accounting wasn't changed
788 * while we were in the middle of writing it out.
789 */
790 VERIFY3U(nodes, ==, zfs_btree_numnodes(&rt->rt_root));
791 VERIFY3U(range_tree_space(rt), ==, rt_space);
792 }
793
794 static int
space_map_open_impl(space_map_t * sm)795 space_map_open_impl(space_map_t *sm)
796 {
797 int error;
798 u_longlong_t blocks;
799
800 error = dmu_bonus_hold(sm->sm_os, sm->sm_object, sm, &sm->sm_dbuf);
801 if (error)
802 return (error);
803
804 dmu_object_size_from_db(sm->sm_dbuf, &sm->sm_blksz, &blocks);
805 sm->sm_phys = sm->sm_dbuf->db_data;
806 return (0);
807 }
808
809 int
space_map_open(space_map_t ** smp,objset_t * os,uint64_t object,uint64_t start,uint64_t size,uint8_t shift)810 space_map_open(space_map_t **smp, objset_t *os, uint64_t object,
811 uint64_t start, uint64_t size, uint8_t shift)
812 {
813 space_map_t *sm;
814 int error;
815
816 ASSERT(*smp == NULL);
817 ASSERT(os != NULL);
818 ASSERT(object != 0);
819
820 sm = kmem_alloc(sizeof (space_map_t), KM_SLEEP);
821
822 sm->sm_start = start;
823 sm->sm_size = size;
824 sm->sm_shift = shift;
825 sm->sm_os = os;
826 sm->sm_object = object;
827 sm->sm_blksz = 0;
828 sm->sm_dbuf = NULL;
829 sm->sm_phys = NULL;
830
831 error = space_map_open_impl(sm);
832 if (error != 0) {
833 space_map_close(sm);
834 return (error);
835 }
836 *smp = sm;
837
838 return (0);
839 }
840
841 void
space_map_close(space_map_t * sm)842 space_map_close(space_map_t *sm)
843 {
844 if (sm == NULL)
845 return;
846
847 if (sm->sm_dbuf != NULL)
848 dmu_buf_rele(sm->sm_dbuf, sm);
849 sm->sm_dbuf = NULL;
850 sm->sm_phys = NULL;
851
852 kmem_free(sm, sizeof (*sm));
853 }
854
855 void
space_map_truncate(space_map_t * sm,int blocksize,dmu_tx_t * tx)856 space_map_truncate(space_map_t *sm, int blocksize, dmu_tx_t *tx)
857 {
858 objset_t *os = sm->sm_os;
859 spa_t *spa = dmu_objset_spa(os);
860 dmu_object_info_t doi;
861
862 ASSERT(dsl_pool_sync_context(dmu_objset_pool(os)));
863 ASSERT(dmu_tx_is_syncing(tx));
864 VERIFY3U(dmu_tx_get_txg(tx), <=, spa_final_dirty_txg(spa));
865
866 dmu_object_info_from_db(sm->sm_dbuf, &doi);
867
868 /*
869 * If the space map has the wrong bonus size (because
870 * SPA_FEATURE_SPACEMAP_HISTOGRAM has recently been enabled), or
871 * the wrong block size (because space_map_blksz has changed),
872 * free and re-allocate its object with the updated sizes.
873 *
874 * Otherwise, just truncate the current object.
875 */
876 if ((spa_feature_is_enabled(spa, SPA_FEATURE_SPACEMAP_HISTOGRAM) &&
877 doi.doi_bonus_size != sizeof (space_map_phys_t)) ||
878 doi.doi_data_block_size != blocksize ||
879 doi.doi_metadata_block_size != 1 << space_map_ibs) {
880 zfs_dbgmsg("txg %llu, spa %s, sm %px, reallocating "
881 "object[%llu]: old bonus %llu, old blocksz %u",
882 (u_longlong_t)dmu_tx_get_txg(tx), spa_name(spa), sm,
883 (u_longlong_t)sm->sm_object,
884 (u_longlong_t)doi.doi_bonus_size,
885 doi.doi_data_block_size);
886
887 space_map_free(sm, tx);
888 dmu_buf_rele(sm->sm_dbuf, sm);
889
890 sm->sm_object = space_map_alloc(sm->sm_os, blocksize, tx);
891 VERIFY0(space_map_open_impl(sm));
892 } else {
893 VERIFY0(dmu_free_range(os, space_map_object(sm), 0, -1ULL, tx));
894
895 /*
896 * If the spacemap is reallocated, its histogram
897 * will be reset. Do the same in the common case so that
898 * bugs related to the uncommon case do not go unnoticed.
899 */
900 memset(sm->sm_phys->smp_histogram, 0,
901 sizeof (sm->sm_phys->smp_histogram));
902 }
903
904 dmu_buf_will_dirty(sm->sm_dbuf, tx);
905 sm->sm_phys->smp_length = 0;
906 sm->sm_phys->smp_alloc = 0;
907 }
908
909 uint64_t
space_map_alloc(objset_t * os,int blocksize,dmu_tx_t * tx)910 space_map_alloc(objset_t *os, int blocksize, dmu_tx_t *tx)
911 {
912 spa_t *spa = dmu_objset_spa(os);
913 uint64_t object;
914 int bonuslen;
915
916 if (spa_feature_is_enabled(spa, SPA_FEATURE_SPACEMAP_HISTOGRAM)) {
917 spa_feature_incr(spa, SPA_FEATURE_SPACEMAP_HISTOGRAM, tx);
918 bonuslen = sizeof (space_map_phys_t);
919 ASSERT3U(bonuslen, <=, dmu_bonus_max());
920 } else {
921 bonuslen = SPACE_MAP_SIZE_V0;
922 }
923
924 object = dmu_object_alloc_ibs(os, DMU_OT_SPACE_MAP, blocksize,
925 space_map_ibs, DMU_OT_SPACE_MAP_HEADER, bonuslen, tx);
926
927 return (object);
928 }
929
930 void
space_map_free_obj(objset_t * os,uint64_t smobj,dmu_tx_t * tx)931 space_map_free_obj(objset_t *os, uint64_t smobj, dmu_tx_t *tx)
932 {
933 spa_t *spa = dmu_objset_spa(os);
934 if (spa_feature_is_enabled(spa, SPA_FEATURE_SPACEMAP_HISTOGRAM)) {
935 dmu_object_info_t doi;
936
937 VERIFY0(dmu_object_info(os, smobj, &doi));
938 if (doi.doi_bonus_size != SPACE_MAP_SIZE_V0) {
939 spa_feature_decr(spa,
940 SPA_FEATURE_SPACEMAP_HISTOGRAM, tx);
941 }
942 }
943
944 VERIFY0(dmu_object_free(os, smobj, tx));
945 }
946
947 void
space_map_free(space_map_t * sm,dmu_tx_t * tx)948 space_map_free(space_map_t *sm, dmu_tx_t *tx)
949 {
950 if (sm == NULL)
951 return;
952
953 space_map_free_obj(sm->sm_os, space_map_object(sm), tx);
954 sm->sm_object = 0;
955 }
956
957 /*
958 * Given a range tree, it makes a worst-case estimate of how much
959 * space would the tree's segments take if they were written to
960 * the given space map.
961 */
962 uint64_t
space_map_estimate_optimal_size(space_map_t * sm,range_tree_t * rt,uint64_t vdev_id)963 space_map_estimate_optimal_size(space_map_t *sm, range_tree_t *rt,
964 uint64_t vdev_id)
965 {
966 spa_t *spa = dmu_objset_spa(sm->sm_os);
967 uint64_t shift = sm->sm_shift;
968 uint64_t *histogram = rt->rt_histogram;
969 uint64_t entries_for_seg = 0;
970
971 /*
972 * In order to get a quick estimate of the optimal size that this
973 * range tree would have on-disk as a space map, we iterate through
974 * its histogram buckets instead of iterating through its nodes.
975 *
976 * Note that this is a highest-bound/worst-case estimate for the
977 * following reasons:
978 *
979 * 1] We assume that we always add a debug padding for each block
980 * we write and we also assume that we start at the last word
981 * of a block attempting to write a two-word entry.
982 * 2] Rounding up errors due to the way segments are distributed
983 * in the buckets of the range tree's histogram.
984 * 3] The activation of zfs_force_some_double_word_sm_entries
985 * (tunable) when testing.
986 *
987 * = Math and Rounding Errors =
988 *
989 * rt_histogram[i] bucket of a range tree represents the number
990 * of entries in [2^i, (2^(i+1))-1] of that range_tree. Given
991 * that, we want to divide the buckets into groups: Buckets that
992 * can be represented using a single-word entry, ones that can
993 * be represented with a double-word entry, and ones that can
994 * only be represented with multiple two-word entries.
995 *
996 * [Note that if the new encoding feature is not enabled there
997 * are only two groups: single-word entry buckets and multiple
998 * single-word entry buckets. The information below assumes
999 * two-word entries enabled, but it can easily applied when
1000 * the feature is not enabled]
1001 *
1002 * To find the highest bucket that can be represented with a
1003 * single-word entry we look at the maximum run that such entry
1004 * can have, which is 2^(SM_RUN_BITS + sm_shift) [remember that
1005 * the run of a space map entry is shifted by sm_shift, thus we
1006 * add it to the exponent]. This way, excluding the value of the
1007 * maximum run that can be represented by a single-word entry,
1008 * all runs that are smaller exist in buckets 0 to
1009 * SM_RUN_BITS + shift - 1.
1010 *
1011 * To find the highest bucket that can be represented with a
1012 * double-word entry, we follow the same approach. Finally, any
1013 * bucket higher than that are represented with multiple two-word
1014 * entries. To be more specific, if the highest bucket whose
1015 * segments can be represented with a single two-word entry is X,
1016 * then bucket X+1 will need 2 two-word entries for each of its
1017 * segments, X+2 will need 4, X+3 will need 8, ...etc.
1018 *
1019 * With all of the above we make our estimation based on bucket
1020 * groups. There is a rounding error though. As we mentioned in
1021 * the example with the one-word entry, the maximum run that can
1022 * be represented in a one-word entry 2^(SM_RUN_BITS + shift) is
1023 * not part of bucket SM_RUN_BITS + shift - 1. Thus, segments of
1024 * that length fall into the next bucket (and bucket group) where
1025 * we start counting two-word entries and this is one more reason
1026 * why the estimated size may end up being bigger than the actual
1027 * size written.
1028 */
1029 uint64_t size = 0;
1030 uint64_t idx = 0;
1031
1032 if (!spa_feature_is_enabled(spa, SPA_FEATURE_SPACEMAP_V2) ||
1033 (vdev_id == SM_NO_VDEVID && sm->sm_size < SM_OFFSET_MAX)) {
1034
1035 /*
1036 * If we are trying to force some double word entries just
1037 * assume the worst-case of every single word entry being
1038 * written as a double word entry.
1039 */
1040 uint64_t entry_size =
1041 (spa_feature_is_enabled(spa, SPA_FEATURE_SPACEMAP_V2) &&
1042 zfs_force_some_double_word_sm_entries) ?
1043 (2 * sizeof (uint64_t)) : sizeof (uint64_t);
1044
1045 uint64_t single_entry_max_bucket = SM_RUN_BITS + shift - 1;
1046 for (; idx <= single_entry_max_bucket; idx++)
1047 size += histogram[idx] * entry_size;
1048
1049 if (!spa_feature_is_enabled(spa, SPA_FEATURE_SPACEMAP_V2)) {
1050 for (; idx < RANGE_TREE_HISTOGRAM_SIZE; idx++) {
1051 ASSERT3U(idx, >=, single_entry_max_bucket);
1052 entries_for_seg =
1053 1ULL << (idx - single_entry_max_bucket);
1054 size += histogram[idx] *
1055 entries_for_seg * entry_size;
1056 }
1057 return (size);
1058 }
1059 }
1060
1061 ASSERT(spa_feature_is_enabled(spa, SPA_FEATURE_SPACEMAP_V2));
1062
1063 uint64_t double_entry_max_bucket = SM2_RUN_BITS + shift - 1;
1064 for (; idx <= double_entry_max_bucket; idx++)
1065 size += histogram[idx] * 2 * sizeof (uint64_t);
1066
1067 for (; idx < RANGE_TREE_HISTOGRAM_SIZE; idx++) {
1068 ASSERT3U(idx, >=, double_entry_max_bucket);
1069 entries_for_seg = 1ULL << (idx - double_entry_max_bucket);
1070 size += histogram[idx] *
1071 entries_for_seg * 2 * sizeof (uint64_t);
1072 }
1073
1074 /*
1075 * Assume the worst case where we start with the padding at the end
1076 * of the current block and we add an extra padding entry at the end
1077 * of all subsequent blocks.
1078 */
1079 size += ((size / sm->sm_blksz) + 1) * sizeof (uint64_t);
1080
1081 return (size);
1082 }
1083
1084 uint64_t
space_map_object(space_map_t * sm)1085 space_map_object(space_map_t *sm)
1086 {
1087 return (sm != NULL ? sm->sm_object : 0);
1088 }
1089
1090 int64_t
space_map_allocated(space_map_t * sm)1091 space_map_allocated(space_map_t *sm)
1092 {
1093 return (sm != NULL ? sm->sm_phys->smp_alloc : 0);
1094 }
1095
1096 uint64_t
space_map_length(space_map_t * sm)1097 space_map_length(space_map_t *sm)
1098 {
1099 return (sm != NULL ? sm->sm_phys->smp_length : 0);
1100 }
1101
1102 uint64_t
space_map_nblocks(space_map_t * sm)1103 space_map_nblocks(space_map_t *sm)
1104 {
1105 if (sm == NULL)
1106 return (0);
1107 return (DIV_ROUND_UP(space_map_length(sm), sm->sm_blksz));
1108 }
1109