xref: /linux/fs/bcachefs/sb-members.c (revision 42b16d3ac371a2fac9b6f08fd75f23f34ba3955a)
1 // SPDX-License-Identifier: GPL-2.0
2 
3 #include "bcachefs.h"
4 #include "btree_cache.h"
5 #include "disk_groups.h"
6 #include "error.h"
7 #include "opts.h"
8 #include "replicas.h"
9 #include "sb-members.h"
10 #include "super-io.h"
11 
bch2_dev_missing(struct bch_fs * c,unsigned dev)12 void bch2_dev_missing(struct bch_fs *c, unsigned dev)
13 {
14 	if (dev != BCH_SB_MEMBER_INVALID)
15 		bch2_fs_inconsistent(c, "pointer to nonexistent device %u", dev);
16 }
17 
bch2_dev_bucket_missing(struct bch_fs * c,struct bpos bucket)18 void bch2_dev_bucket_missing(struct bch_fs *c, struct bpos bucket)
19 {
20 	bch2_fs_inconsistent(c, "pointer to nonexistent bucket %llu:%llu", bucket.inode, bucket.offset);
21 }
22 
23 #define x(t, n, ...) [n] = #t,
24 static const char * const bch2_iops_measurements[] = {
25 	BCH_IOPS_MEASUREMENTS()
26 	NULL
27 };
28 
29 char * const bch2_member_error_strs[] = {
30 	BCH_MEMBER_ERROR_TYPES()
31 	NULL
32 };
33 #undef x
34 
35 /* Code for bch_sb_field_members_v1: */
36 
bch2_members_v2_get_mut(struct bch_sb * sb,int i)37 struct bch_member *bch2_members_v2_get_mut(struct bch_sb *sb, int i)
38 {
39 	return __bch2_members_v2_get_mut(bch2_sb_field_get(sb, members_v2), i);
40 }
41 
members_v2_get(struct bch_sb_field_members_v2 * mi,int i)42 static struct bch_member members_v2_get(struct bch_sb_field_members_v2 *mi, int i)
43 {
44 	struct bch_member ret, *p = __bch2_members_v2_get_mut(mi, i);
45 	memset(&ret, 0, sizeof(ret));
46 	memcpy(&ret, p, min_t(size_t, le16_to_cpu(mi->member_bytes), sizeof(ret)));
47 	return ret;
48 }
49 
members_v1_get_mut(struct bch_sb_field_members_v1 * mi,int i)50 static struct bch_member *members_v1_get_mut(struct bch_sb_field_members_v1 *mi, int i)
51 {
52 	return (void *) mi->_members + (i * BCH_MEMBER_V1_BYTES);
53 }
54 
members_v1_get(struct bch_sb_field_members_v1 * mi,int i)55 static struct bch_member members_v1_get(struct bch_sb_field_members_v1 *mi, int i)
56 {
57 	struct bch_member ret, *p = members_v1_get_mut(mi, i);
58 	memset(&ret, 0, sizeof(ret));
59 	memcpy(&ret, p, min_t(size_t, BCH_MEMBER_V1_BYTES, sizeof(ret)));
60 	return ret;
61 }
62 
bch2_sb_member_get(struct bch_sb * sb,int i)63 struct bch_member bch2_sb_member_get(struct bch_sb *sb, int i)
64 {
65 	struct bch_sb_field_members_v2 *mi2 = bch2_sb_field_get(sb, members_v2);
66 	if (mi2)
67 		return members_v2_get(mi2, i);
68 	struct bch_sb_field_members_v1 *mi1 = bch2_sb_field_get(sb, members_v1);
69 	return members_v1_get(mi1, i);
70 }
71 
sb_members_v2_resize_entries(struct bch_fs * c)72 static int sb_members_v2_resize_entries(struct bch_fs *c)
73 {
74 	struct bch_sb_field_members_v2 *mi = bch2_sb_field_get(c->disk_sb.sb, members_v2);
75 
76 	if (le16_to_cpu(mi->member_bytes) < sizeof(struct bch_member)) {
77 		unsigned u64s = DIV_ROUND_UP((sizeof(*mi) + sizeof(mi->_members[0]) *
78 					      c->disk_sb.sb->nr_devices), 8);
79 
80 		mi = bch2_sb_field_resize(&c->disk_sb, members_v2, u64s);
81 		if (!mi)
82 			return -BCH_ERR_ENOSPC_sb_members_v2;
83 
84 		for (int i = c->disk_sb.sb->nr_devices - 1; i >= 0; --i) {
85 			void *dst = (void *) mi->_members + (i * sizeof(struct bch_member));
86 			memmove(dst, __bch2_members_v2_get_mut(mi, i), le16_to_cpu(mi->member_bytes));
87 			memset(dst + le16_to_cpu(mi->member_bytes),
88 			       0, (sizeof(struct bch_member) - le16_to_cpu(mi->member_bytes)));
89 		}
90 		mi->member_bytes = cpu_to_le16(sizeof(struct bch_member));
91 	}
92 	return 0;
93 }
94 
bch2_sb_members_v2_init(struct bch_fs * c)95 int bch2_sb_members_v2_init(struct bch_fs *c)
96 {
97 	struct bch_sb_field_members_v1 *mi1;
98 	struct bch_sb_field_members_v2 *mi2;
99 
100 	if (!bch2_sb_field_get(c->disk_sb.sb, members_v2)) {
101 		mi2 = bch2_sb_field_resize(&c->disk_sb, members_v2,
102 				DIV_ROUND_UP(sizeof(*mi2) +
103 					     sizeof(struct bch_member) * c->sb.nr_devices,
104 					     sizeof(u64)));
105 		mi1 = bch2_sb_field_get(c->disk_sb.sb, members_v1);
106 		memcpy(&mi2->_members[0], &mi1->_members[0],
107 		       BCH_MEMBER_V1_BYTES * c->sb.nr_devices);
108 		memset(&mi2->pad[0], 0, sizeof(mi2->pad));
109 		mi2->member_bytes = cpu_to_le16(BCH_MEMBER_V1_BYTES);
110 	}
111 
112 	return sb_members_v2_resize_entries(c);
113 }
114 
bch2_sb_members_cpy_v2_v1(struct bch_sb_handle * disk_sb)115 int bch2_sb_members_cpy_v2_v1(struct bch_sb_handle *disk_sb)
116 {
117 	struct bch_sb_field_members_v1 *mi1;
118 	struct bch_sb_field_members_v2 *mi2;
119 
120 	mi1 = bch2_sb_field_resize(disk_sb, members_v1,
121 			DIV_ROUND_UP(sizeof(*mi1) + BCH_MEMBER_V1_BYTES *
122 				     disk_sb->sb->nr_devices, sizeof(u64)));
123 	if (!mi1)
124 		return -BCH_ERR_ENOSPC_sb_members;
125 
126 	mi2 = bch2_sb_field_get(disk_sb->sb, members_v2);
127 
128 	for (unsigned i = 0; i < disk_sb->sb->nr_devices; i++)
129 		memcpy(members_v1_get_mut(mi1, i), __bch2_members_v2_get_mut(mi2, i), BCH_MEMBER_V1_BYTES);
130 
131 	return 0;
132 }
133 
validate_member(struct printbuf * err,struct bch_member m,struct bch_sb * sb,int i)134 static int validate_member(struct printbuf *err,
135 			   struct bch_member m,
136 			   struct bch_sb *sb,
137 			   int i)
138 {
139 	if (le64_to_cpu(m.nbuckets) > BCH_MEMBER_NBUCKETS_MAX) {
140 		prt_printf(err, "device %u: too many buckets (got %llu, max %u)",
141 			   i, le64_to_cpu(m.nbuckets), BCH_MEMBER_NBUCKETS_MAX);
142 		return -BCH_ERR_invalid_sb_members;
143 	}
144 
145 	if (le64_to_cpu(m.nbuckets) -
146 	    le16_to_cpu(m.first_bucket) < BCH_MIN_NR_NBUCKETS) {
147 		prt_printf(err, "device %u: not enough buckets (got %llu, max %u)",
148 			   i, le64_to_cpu(m.nbuckets), BCH_MIN_NR_NBUCKETS);
149 		return -BCH_ERR_invalid_sb_members;
150 	}
151 
152 	if (le16_to_cpu(m.bucket_size) <
153 	    le16_to_cpu(sb->block_size)) {
154 		prt_printf(err, "device %u: bucket size %u smaller than block size %u",
155 			   i, le16_to_cpu(m.bucket_size), le16_to_cpu(sb->block_size));
156 		return -BCH_ERR_invalid_sb_members;
157 	}
158 
159 	if (le16_to_cpu(m.bucket_size) <
160 	    BCH_SB_BTREE_NODE_SIZE(sb)) {
161 		prt_printf(err, "device %u: bucket size %u smaller than btree node size %llu",
162 			   i, le16_to_cpu(m.bucket_size), BCH_SB_BTREE_NODE_SIZE(sb));
163 		return -BCH_ERR_invalid_sb_members;
164 	}
165 
166 	return 0;
167 }
168 
member_to_text(struct printbuf * out,struct bch_member m,struct bch_sb_field_disk_groups * gi,struct bch_sb * sb,int i)169 static void member_to_text(struct printbuf *out,
170 			   struct bch_member m,
171 			   struct bch_sb_field_disk_groups *gi,
172 			   struct bch_sb *sb,
173 			   int i)
174 {
175 	unsigned data_have = bch2_sb_dev_has_data(sb, i);
176 	u64 bucket_size = le16_to_cpu(m.bucket_size);
177 	u64 device_size = le64_to_cpu(m.nbuckets) * bucket_size;
178 
179 	if (!bch2_member_alive(&m))
180 		return;
181 
182 	prt_printf(out, "Device:\t%u\n", i);
183 
184 	printbuf_indent_add(out, 2);
185 
186 	prt_printf(out, "Label:\t");
187 	if (BCH_MEMBER_GROUP(&m)) {
188 		unsigned idx = BCH_MEMBER_GROUP(&m) - 1;
189 
190 		if (idx < disk_groups_nr(gi))
191 			prt_printf(out, "%s (%u)",
192 				   gi->entries[idx].label, idx);
193 		else
194 			prt_printf(out, "(bad disk labels section)");
195 	} else {
196 		prt_printf(out, "(none)");
197 	}
198 	prt_newline(out);
199 
200 	prt_printf(out, "UUID:\t");
201 	pr_uuid(out, m.uuid.b);
202 	prt_newline(out);
203 
204 	prt_printf(out, "Size:\t");
205 	prt_units_u64(out, device_size << 9);
206 	prt_newline(out);
207 
208 	for (unsigned i = 0; i < BCH_MEMBER_ERROR_NR; i++)
209 		prt_printf(out, "%s errors:\t%llu\n", bch2_member_error_strs[i], le64_to_cpu(m.errors[i]));
210 
211 	for (unsigned i = 0; i < BCH_IOPS_NR; i++)
212 		prt_printf(out, "%s iops:\t%u\n", bch2_iops_measurements[i], le32_to_cpu(m.iops[i]));
213 
214 	prt_printf(out, "Bucket size:\t");
215 	prt_units_u64(out, bucket_size << 9);
216 	prt_newline(out);
217 
218 	prt_printf(out, "First bucket:\t%u\n", le16_to_cpu(m.first_bucket));
219 	prt_printf(out, "Buckets:\t%llu\n", le64_to_cpu(m.nbuckets));
220 
221 	prt_printf(out, "Last mount:\t");
222 	if (m.last_mount)
223 		bch2_prt_datetime(out, le64_to_cpu(m.last_mount));
224 	else
225 		prt_printf(out, "(never)");
226 	prt_newline(out);
227 
228 	prt_printf(out, "Last superblock write:\t%llu\n", le64_to_cpu(m.seq));
229 
230 	prt_printf(out, "State:\t%s\n",
231 		   BCH_MEMBER_STATE(&m) < BCH_MEMBER_STATE_NR
232 		   ? bch2_member_states[BCH_MEMBER_STATE(&m)]
233 		   : "unknown");
234 
235 	prt_printf(out, "Data allowed:\t");
236 	if (BCH_MEMBER_DATA_ALLOWED(&m))
237 		prt_bitflags(out, __bch2_data_types, BCH_MEMBER_DATA_ALLOWED(&m));
238 	else
239 		prt_printf(out, "(none)");
240 	prt_newline(out);
241 
242 	prt_printf(out, "Has data:\t");
243 	if (data_have)
244 		prt_bitflags(out, __bch2_data_types, data_have);
245 	else
246 		prt_printf(out, "(none)");
247 	prt_newline(out);
248 
249 	prt_printf(out, "Btree allocated bitmap blocksize:\t");
250 	prt_units_u64(out, 1ULL << m.btree_bitmap_shift);
251 	prt_newline(out);
252 
253 	prt_printf(out, "Btree allocated bitmap:\t");
254 	bch2_prt_u64_base2_nbits(out, le64_to_cpu(m.btree_allocated_bitmap), 64);
255 	prt_newline(out);
256 
257 	prt_printf(out, "Durability:\t%llu\n", BCH_MEMBER_DURABILITY(&m) ? BCH_MEMBER_DURABILITY(&m) - 1 : 1);
258 
259 	prt_printf(out, "Discard:\t%llu\n", BCH_MEMBER_DISCARD(&m));
260 	prt_printf(out, "Freespace initialized:\t%llu\n", BCH_MEMBER_FREESPACE_INITIALIZED(&m));
261 
262 	printbuf_indent_sub(out, 2);
263 }
264 
bch2_sb_members_v1_validate(struct bch_sb * sb,struct bch_sb_field * f,enum bch_validate_flags flags,struct printbuf * err)265 static int bch2_sb_members_v1_validate(struct bch_sb *sb, struct bch_sb_field *f,
266 				enum bch_validate_flags flags, struct printbuf *err)
267 {
268 	struct bch_sb_field_members_v1 *mi = field_to_type(f, members_v1);
269 	unsigned i;
270 
271 	if ((void *) members_v1_get_mut(mi, sb->nr_devices) > vstruct_end(&mi->field)) {
272 		prt_printf(err, "too many devices for section size");
273 		return -BCH_ERR_invalid_sb_members;
274 	}
275 
276 	for (i = 0; i < sb->nr_devices; i++) {
277 		struct bch_member m = members_v1_get(mi, i);
278 
279 		int ret = validate_member(err, m, sb, i);
280 		if (ret)
281 			return ret;
282 	}
283 
284 	return 0;
285 }
286 
bch2_sb_members_v1_to_text(struct printbuf * out,struct bch_sb * sb,struct bch_sb_field * f)287 static void bch2_sb_members_v1_to_text(struct printbuf *out, struct bch_sb *sb,
288 				       struct bch_sb_field *f)
289 {
290 	struct bch_sb_field_members_v1 *mi = field_to_type(f, members_v1);
291 	struct bch_sb_field_disk_groups *gi = bch2_sb_field_get(sb, disk_groups);
292 	unsigned i;
293 
294 	for (i = 0; i < sb->nr_devices; i++)
295 		member_to_text(out, members_v1_get(mi, i), gi, sb, i);
296 }
297 
298 const struct bch_sb_field_ops bch_sb_field_ops_members_v1 = {
299 	.validate	= bch2_sb_members_v1_validate,
300 	.to_text	= bch2_sb_members_v1_to_text,
301 };
302 
bch2_sb_members_v2_to_text(struct printbuf * out,struct bch_sb * sb,struct bch_sb_field * f)303 static void bch2_sb_members_v2_to_text(struct printbuf *out, struct bch_sb *sb,
304 				       struct bch_sb_field *f)
305 {
306 	struct bch_sb_field_members_v2 *mi = field_to_type(f, members_v2);
307 	struct bch_sb_field_disk_groups *gi = bch2_sb_field_get(sb, disk_groups);
308 	unsigned i;
309 
310 	for (i = 0; i < sb->nr_devices; i++)
311 		member_to_text(out, members_v2_get(mi, i), gi, sb, i);
312 }
313 
bch2_sb_members_v2_validate(struct bch_sb * sb,struct bch_sb_field * f,enum bch_validate_flags flags,struct printbuf * err)314 static int bch2_sb_members_v2_validate(struct bch_sb *sb, struct bch_sb_field *f,
315 				enum bch_validate_flags flags, struct printbuf *err)
316 {
317 	struct bch_sb_field_members_v2 *mi = field_to_type(f, members_v2);
318 	size_t mi_bytes = (void *) __bch2_members_v2_get_mut(mi, sb->nr_devices) -
319 		(void *) mi;
320 
321 	if (mi_bytes > vstruct_bytes(&mi->field)) {
322 		prt_printf(err, "section too small (%zu > %zu)",
323 			   mi_bytes, vstruct_bytes(&mi->field));
324 		return -BCH_ERR_invalid_sb_members;
325 	}
326 
327 	for (unsigned i = 0; i < sb->nr_devices; i++) {
328 		int ret = validate_member(err, members_v2_get(mi, i), sb, i);
329 		if (ret)
330 			return ret;
331 	}
332 
333 	return 0;
334 }
335 
336 const struct bch_sb_field_ops bch_sb_field_ops_members_v2 = {
337 	.validate	= bch2_sb_members_v2_validate,
338 	.to_text	= bch2_sb_members_v2_to_text,
339 };
340 
bch2_sb_members_from_cpu(struct bch_fs * c)341 void bch2_sb_members_from_cpu(struct bch_fs *c)
342 {
343 	struct bch_sb_field_members_v2 *mi = bch2_sb_field_get(c->disk_sb.sb, members_v2);
344 
345 	rcu_read_lock();
346 	for_each_member_device_rcu(c, ca, NULL) {
347 		struct bch_member *m = __bch2_members_v2_get_mut(mi, ca->dev_idx);
348 
349 		for (unsigned e = 0; e < BCH_MEMBER_ERROR_NR; e++)
350 			m->errors[e] = cpu_to_le64(atomic64_read(&ca->errors[e]));
351 	}
352 	rcu_read_unlock();
353 }
354 
bch2_dev_io_errors_to_text(struct printbuf * out,struct bch_dev * ca)355 void bch2_dev_io_errors_to_text(struct printbuf *out, struct bch_dev *ca)
356 {
357 	struct bch_fs *c = ca->fs;
358 	struct bch_member m;
359 
360 	mutex_lock(&ca->fs->sb_lock);
361 	m = bch2_sb_member_get(c->disk_sb.sb, ca->dev_idx);
362 	mutex_unlock(&ca->fs->sb_lock);
363 
364 	printbuf_tabstop_push(out, 12);
365 
366 	prt_str(out, "IO errors since filesystem creation");
367 	prt_newline(out);
368 
369 	printbuf_indent_add(out, 2);
370 	for (unsigned i = 0; i < BCH_MEMBER_ERROR_NR; i++)
371 		prt_printf(out, "%s:\t%llu\n", bch2_member_error_strs[i], atomic64_read(&ca->errors[i]));
372 	printbuf_indent_sub(out, 2);
373 
374 	prt_str(out, "IO errors since ");
375 	bch2_pr_time_units(out, (ktime_get_real_seconds() - le64_to_cpu(m.errors_reset_time)) * NSEC_PER_SEC);
376 	prt_str(out, " ago");
377 	prt_newline(out);
378 
379 	printbuf_indent_add(out, 2);
380 	for (unsigned i = 0; i < BCH_MEMBER_ERROR_NR; i++)
381 		prt_printf(out, "%s:\t%llu\n", bch2_member_error_strs[i],
382 			   atomic64_read(&ca->errors[i]) - le64_to_cpu(m.errors_at_reset[i]));
383 	printbuf_indent_sub(out, 2);
384 }
385 
bch2_dev_errors_reset(struct bch_dev * ca)386 void bch2_dev_errors_reset(struct bch_dev *ca)
387 {
388 	struct bch_fs *c = ca->fs;
389 	struct bch_member *m;
390 
391 	mutex_lock(&c->sb_lock);
392 	m = bch2_members_v2_get_mut(c->disk_sb.sb, ca->dev_idx);
393 	for (unsigned i = 0; i < ARRAY_SIZE(m->errors_at_reset); i++)
394 		m->errors_at_reset[i] = cpu_to_le64(atomic64_read(&ca->errors[i]));
395 	m->errors_reset_time = cpu_to_le64(ktime_get_real_seconds());
396 
397 	bch2_write_super(c);
398 	mutex_unlock(&c->sb_lock);
399 }
400 
401 /*
402  * Per member "range has btree nodes" bitmap:
403  *
404  * This is so that if we ever have to run the btree node scan to repair we don't
405  * have to scan full devices:
406  */
407 
bch2_dev_btree_bitmap_marked(struct bch_fs * c,struct bkey_s_c k)408 bool bch2_dev_btree_bitmap_marked(struct bch_fs *c, struct bkey_s_c k)
409 {
410 	bool ret = true;
411 	rcu_read_lock();
412 	bkey_for_each_ptr(bch2_bkey_ptrs_c(k), ptr) {
413 		struct bch_dev *ca = bch2_dev_rcu(c, ptr->dev);
414 		if (!ca)
415 			continue;
416 
417 		if (!bch2_dev_btree_bitmap_marked_sectors(ca, ptr->offset, btree_sectors(c))) {
418 			ret = false;
419 			break;
420 		}
421 	}
422 	rcu_read_unlock();
423 	return ret;
424 }
425 
__bch2_dev_btree_bitmap_mark(struct bch_sb_field_members_v2 * mi,unsigned dev,u64 start,unsigned sectors)426 static void __bch2_dev_btree_bitmap_mark(struct bch_sb_field_members_v2 *mi, unsigned dev,
427 				u64 start, unsigned sectors)
428 {
429 	struct bch_member *m = __bch2_members_v2_get_mut(mi, dev);
430 	u64 bitmap = le64_to_cpu(m->btree_allocated_bitmap);
431 
432 	u64 end = start + sectors;
433 
434 	int resize = ilog2(roundup_pow_of_two(end)) - (m->btree_bitmap_shift + 6);
435 	if (resize > 0) {
436 		u64 new_bitmap = 0;
437 
438 		for (unsigned i = 0; i < 64; i++)
439 			if (bitmap & BIT_ULL(i))
440 				new_bitmap |= BIT_ULL(i >> resize);
441 		bitmap = new_bitmap;
442 		m->btree_bitmap_shift += resize;
443 	}
444 
445 	BUG_ON(m->btree_bitmap_shift > 57);
446 	BUG_ON(end > 64ULL << m->btree_bitmap_shift);
447 
448 	for (unsigned bit = start >> m->btree_bitmap_shift;
449 	     (u64) bit << m->btree_bitmap_shift < end;
450 	     bit++)
451 		bitmap |= BIT_ULL(bit);
452 
453 	m->btree_allocated_bitmap = cpu_to_le64(bitmap);
454 }
455 
bch2_dev_btree_bitmap_mark(struct bch_fs * c,struct bkey_s_c k)456 void bch2_dev_btree_bitmap_mark(struct bch_fs *c, struct bkey_s_c k)
457 {
458 	lockdep_assert_held(&c->sb_lock);
459 
460 	struct bch_sb_field_members_v2 *mi = bch2_sb_field_get(c->disk_sb.sb, members_v2);
461 	bkey_for_each_ptr(bch2_bkey_ptrs_c(k), ptr) {
462 		if (!bch2_member_exists(c->disk_sb.sb, ptr->dev))
463 			continue;
464 
465 		__bch2_dev_btree_bitmap_mark(mi, ptr->dev, ptr->offset, btree_sectors(c));
466 	}
467 }
468 
bch2_sb_nr_devices(const struct bch_sb * sb)469 unsigned bch2_sb_nr_devices(const struct bch_sb *sb)
470 {
471 	unsigned nr = 0;
472 
473 	for (unsigned i = 0; i < sb->nr_devices; i++)
474 		nr += bch2_member_exists((struct bch_sb *) sb, i);
475 	return nr;
476 }
477 
bch2_sb_member_alloc(struct bch_fs * c)478 int bch2_sb_member_alloc(struct bch_fs *c)
479 {
480 	unsigned dev_idx = c->sb.nr_devices;
481 	struct bch_sb_field_members_v2 *mi;
482 	unsigned nr_devices;
483 	unsigned u64s;
484 	int best = -1;
485 	u64 best_last_mount = 0;
486 
487 	if (dev_idx < BCH_SB_MEMBERS_MAX)
488 		goto have_slot;
489 
490 	for (dev_idx = 0; dev_idx < BCH_SB_MEMBERS_MAX; dev_idx++) {
491 		/* eventually BCH_SB_MEMBERS_MAX will be raised */
492 		if (dev_idx == BCH_SB_MEMBER_INVALID)
493 			continue;
494 
495 		struct bch_member m = bch2_sb_member_get(c->disk_sb.sb, dev_idx);
496 		if (bch2_member_alive(&m))
497 			continue;
498 
499 		u64 last_mount = le64_to_cpu(m.last_mount);
500 		if (best < 0 || last_mount < best_last_mount) {
501 			best = dev_idx;
502 			best_last_mount = last_mount;
503 		}
504 	}
505 	if (best >= 0) {
506 		dev_idx = best;
507 		goto have_slot;
508 	}
509 
510 	return -BCH_ERR_ENOSPC_sb_members;
511 have_slot:
512 	nr_devices = max_t(unsigned, dev_idx + 1, c->sb.nr_devices);
513 
514 	mi = bch2_sb_field_get(c->disk_sb.sb, members_v2);
515 	u64s = DIV_ROUND_UP(sizeof(struct bch_sb_field_members_v2) +
516 			    le16_to_cpu(mi->member_bytes) * nr_devices, sizeof(u64));
517 
518 	mi = bch2_sb_field_resize(&c->disk_sb, members_v2, u64s);
519 	if (!mi)
520 		return -BCH_ERR_ENOSPC_sb_members;
521 
522 	c->disk_sb.sb->nr_devices = nr_devices;
523 	return dev_idx;
524 }
525