1 // SPDX-License-Identifier: GPL-2.0
4 #include "alloc_background.h"
5 #include "backpointers.h"
6 #include "btree_cache.h"
7 #include "btree_update.h"
8 #include "btree_write_buffer.h"
13 static bool extent_matches_bp(struct bch_fs *c,
14 enum btree_id btree_id, unsigned level,
17 struct bch_backpointer bp)
19 struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(k);
20 const union bch_extent_entry *entry;
21 struct extent_ptr_decoded p;
23 bkey_for_each_ptr_decode(k.k, ptrs, p, entry) {
25 struct bch_backpointer bp2;
30 bch2_extent_ptr_to_bp(c, btree_id, level, k, p,
32 if (bpos_eq(bucket, bucket2) &&
33 !memcmp(&bp, &bp2, sizeof(bp)))
40 int bch2_backpointer_invalid(const struct bch_fs *c, struct bkey_s_c k,
41 unsigned flags, struct printbuf *err)
43 struct bkey_s_c_backpointer bp = bkey_s_c_to_backpointer(k);
44 struct bpos bucket = bp_pos_to_bucket(c, bp.k->p);
46 if (!bpos_eq(bp.k->p, bucket_pos_to_bp(c, bucket, bp.v->bucket_offset))) {
47 prt_str(err, "backpointer at wrong pos");
48 return -BCH_ERR_invalid_bkey;
54 void bch2_backpointer_to_text(struct printbuf *out, const struct bch_backpointer *bp)
56 prt_printf(out, "btree=%s l=%u offset=%llu:%u len=%u pos=",
57 bch2_btree_ids[bp->btree_id],
59 (u64) (bp->bucket_offset >> MAX_EXTENT_COMPRESS_RATIO_SHIFT),
60 (u32) bp->bucket_offset & ~(~0U << MAX_EXTENT_COMPRESS_RATIO_SHIFT),
62 bch2_bpos_to_text(out, bp->pos);
65 void bch2_backpointer_k_to_text(struct printbuf *out, struct bch_fs *c, struct bkey_s_c k)
67 prt_str(out, "bucket=");
68 bch2_bpos_to_text(out, bp_pos_to_bucket(c, k.k->p));
71 bch2_backpointer_to_text(out, bkey_s_c_to_backpointer(k).v);
74 void bch2_backpointer_swab(struct bkey_s k)
76 struct bkey_s_backpointer bp = bkey_s_to_backpointer(k);
78 bp.v->bucket_offset = swab32(bp.v->bucket_offset);
79 bp.v->bucket_len = swab32(bp.v->bucket_len);
80 bch2_bpos_swab(&bp.v->pos);
83 static noinline int backpointer_mod_err(struct btree_trans *trans,
84 struct bch_backpointer bp,
86 struct bkey_s_c orig_k,
89 struct bch_fs *c = trans->c;
90 struct printbuf buf = PRINTBUF;
93 prt_printf(&buf, "existing backpointer found when inserting ");
94 bch2_backpointer_to_text(&buf, &bp);
96 printbuf_indent_add(&buf, 2);
98 prt_printf(&buf, "found ");
99 bch2_bkey_val_to_text(&buf, c, bp_k);
102 prt_printf(&buf, "for ");
103 bch2_bkey_val_to_text(&buf, c, orig_k);
105 bch_err(c, "%s", buf.buf);
106 } else if (test_bit(BCH_FS_CHECK_BACKPOINTERS_DONE, &c->flags)) {
107 prt_printf(&buf, "backpointer not found when deleting");
109 printbuf_indent_add(&buf, 2);
111 prt_printf(&buf, "searching for ");
112 bch2_backpointer_to_text(&buf, &bp);
115 prt_printf(&buf, "got ");
116 bch2_bkey_val_to_text(&buf, c, bp_k);
119 prt_printf(&buf, "for ");
120 bch2_bkey_val_to_text(&buf, c, orig_k);
122 bch_err(c, "%s", buf.buf);
127 if (test_bit(BCH_FS_CHECK_BACKPOINTERS_DONE, &c->flags)) {
128 bch2_inconsistent_error(c);
135 int bch2_bucket_backpointer_mod_nowritebuffer(struct btree_trans *trans,
137 struct bch_backpointer bp,
138 struct bkey_s_c orig_k,
141 struct bch_fs *c = trans->c;
142 struct bkey_i_backpointer *bp_k;
143 struct btree_iter bp_iter;
147 bp_k = bch2_trans_kmalloc_nomemzero(trans, sizeof(struct bkey_i_backpointer));
148 ret = PTR_ERR_OR_ZERO(bp_k);
152 bkey_backpointer_init(&bp_k->k_i);
153 bp_k->k.p = bucket_pos_to_bp(c, bucket, bp.bucket_offset);
157 bp_k->k.type = KEY_TYPE_deleted;
158 set_bkey_val_u64s(&bp_k->k, 0);
161 k = bch2_bkey_get_iter(trans, &bp_iter, BTREE_ID_backpointers,
165 BTREE_ITER_WITH_UPDATES);
172 : (k.k->type != KEY_TYPE_backpointer ||
173 memcmp(bkey_s_c_to_backpointer(k).v, &bp, sizeof(bp)))) {
174 ret = backpointer_mod_err(trans, bp, k, orig_k, insert);
179 ret = bch2_trans_update(trans, &bp_iter, &bp_k->k_i, 0);
181 bch2_trans_iter_exit(trans, &bp_iter);
186 * Find the next backpointer >= *bp_offset:
188 int bch2_get_next_backpointer(struct btree_trans *trans,
189 struct bpos bucket, int gen,
191 struct bch_backpointer *bp,
194 struct bch_fs *c = trans->c;
195 struct bpos bp_end_pos = bucket_pos_to_bp(c, bpos_nosnap_successor(bucket), 0);
196 struct btree_iter alloc_iter = { NULL }, bp_iter = { NULL };
200 if (bpos_ge(*bp_pos, bp_end_pos))
204 k = bch2_bkey_get_iter(trans, &alloc_iter, BTREE_ID_alloc,
205 bucket, BTREE_ITER_CACHED|iter_flags);
210 if (k.k->type != KEY_TYPE_alloc_v4 ||
211 bkey_s_c_to_alloc_v4(k).v->gen != gen)
215 *bp_pos = bpos_max(*bp_pos, bucket_pos_to_bp(c, bucket, 0));
217 for_each_btree_key_norestart(trans, bp_iter, BTREE_ID_backpointers,
218 *bp_pos, iter_flags, k, ret) {
219 if (bpos_ge(k.k->p, bp_end_pos))
223 *bp = *bkey_s_c_to_backpointer(k).v;
229 bch2_trans_iter_exit(trans, &bp_iter);
230 bch2_trans_iter_exit(trans, &alloc_iter);
234 static void backpointer_not_found(struct btree_trans *trans,
236 struct bch_backpointer bp,
238 const char *thing_it_points_to)
240 struct bch_fs *c = trans->c;
241 struct printbuf buf = PRINTBUF;
242 struct bpos bucket = bp_pos_to_bucket(c, bp_pos);
244 if (likely(!bch2_backpointers_no_use_write_buffer))
247 prt_printf(&buf, "backpointer doesn't match %s it points to:\n ",
249 prt_printf(&buf, "bucket: ");
250 bch2_bpos_to_text(&buf, bucket);
251 prt_printf(&buf, "\n ");
253 prt_printf(&buf, "backpointer pos: ");
254 bch2_bpos_to_text(&buf, bp_pos);
255 prt_printf(&buf, "\n ");
257 bch2_backpointer_to_text(&buf, &bp);
258 prt_printf(&buf, "\n ");
259 bch2_bkey_val_to_text(&buf, c, k);
260 if (!test_bit(BCH_FS_CHECK_BACKPOINTERS_DONE, &c->flags))
261 bch_err_ratelimited(c, "%s", buf.buf);
263 bch2_trans_inconsistent(trans, "%s", buf.buf);
268 struct bkey_s_c bch2_backpointer_get_key(struct btree_trans *trans,
269 struct btree_iter *iter,
271 struct bch_backpointer bp,
274 struct bch_fs *c = trans->c;
275 struct bpos bucket = bp_pos_to_bucket(c, bp_pos);
278 bch2_trans_node_iter_init(trans, iter,
282 min(bp.level, c->btree_roots[bp.btree_id].level),
284 k = bch2_btree_iter_peek_slot(iter);
286 bch2_trans_iter_exit(trans, iter);
290 if (bp.level == c->btree_roots[bp.btree_id].level + 1)
291 k = bkey_i_to_s_c(&c->btree_roots[bp.btree_id].key);
293 if (k.k && extent_matches_bp(c, bp.btree_id, bp.level, k, bucket, bp))
296 bch2_trans_iter_exit(trans, iter);
298 if (unlikely(bch2_backpointers_no_use_write_buffer)) {
303 * If a backpointer for a btree node wasn't found, it may be
304 * because it was overwritten by a new btree node that hasn't
305 * been written out yet - backpointer_get_node() checks for
308 b = bch2_backpointer_get_node(trans, iter, bp_pos, bp);
309 if (!IS_ERR_OR_NULL(b))
310 return bkey_i_to_s_c(&b->key);
312 bch2_trans_iter_exit(trans, iter);
315 return bkey_s_c_err(PTR_ERR(b));
316 return bkey_s_c_null;
319 backpointer_not_found(trans, bp_pos, bp, k, "extent");
322 return bkey_s_c_null;
325 struct btree *bch2_backpointer_get_node(struct btree_trans *trans,
326 struct btree_iter *iter,
328 struct bch_backpointer bp)
330 struct bch_fs *c = trans->c;
331 struct bpos bucket = bp_pos_to_bucket(c, bp_pos);
336 bch2_trans_node_iter_init(trans, iter,
342 b = bch2_btree_iter_peek_node(iter);
346 if (b && extent_matches_bp(c, bp.btree_id, bp.level,
347 bkey_i_to_s_c(&b->key),
351 if (b && btree_node_will_make_reachable(b)) {
352 b = ERR_PTR(-BCH_ERR_backpointer_to_overwritten_btree_node);
354 backpointer_not_found(trans, bp_pos, bp,
355 bkey_i_to_s_c(&b->key), "btree node");
359 bch2_trans_iter_exit(trans, iter);
363 static int bch2_check_btree_backpointer(struct btree_trans *trans, struct btree_iter *bp_iter,
366 struct bch_fs *c = trans->c;
367 struct btree_iter alloc_iter = { NULL };
369 struct bkey_s_c alloc_k;
370 struct printbuf buf = PRINTBUF;
373 if (fsck_err_on(!bch2_dev_exists2(c, k.k->p.inode), c,
374 "backpointer for mising device:\n%s",
375 (bch2_bkey_val_to_text(&buf, c, k), buf.buf))) {
376 ret = bch2_btree_delete_at(trans, bp_iter, 0);
380 ca = bch_dev_bkey_exists(c, k.k->p.inode);
382 alloc_k = bch2_bkey_get_iter(trans, &alloc_iter, BTREE_ID_alloc,
383 bp_pos_to_bucket(c, k.k->p), 0);
384 ret = bkey_err(alloc_k);
388 if (fsck_err_on(alloc_k.k->type != KEY_TYPE_alloc_v4, c,
389 "backpointer for nonexistent alloc key: %llu:%llu:0\n%s",
390 alloc_iter.pos.inode, alloc_iter.pos.offset,
391 (bch2_bkey_val_to_text(&buf, c, alloc_k), buf.buf))) {
392 ret = bch2_btree_delete_at(trans, bp_iter, 0);
397 bch2_trans_iter_exit(trans, &alloc_iter);
402 /* verify that every backpointer has a corresponding alloc key */
403 int bch2_check_btree_backpointers(struct bch_fs *c)
405 struct btree_iter iter;
408 return bch2_trans_run(c,
409 for_each_btree_key_commit(&trans, iter,
410 BTREE_ID_backpointers, POS_MIN, 0, k,
411 NULL, NULL, BTREE_INSERT_LAZY_RW|BTREE_INSERT_NOFAIL,
412 bch2_check_btree_backpointer(&trans, &iter, k)));
420 static int check_bp_exists(struct btree_trans *trans,
422 struct bch_backpointer bp,
423 struct bkey_s_c orig_k,
424 struct bpos bucket_start,
425 struct bpos bucket_end,
426 struct bpos_level *last_flushed)
428 struct bch_fs *c = trans->c;
429 struct btree_iter bp_iter = { NULL };
430 struct printbuf buf = PRINTBUF;
431 struct bkey_s_c bp_k;
434 if (bpos_lt(bucket, bucket_start) ||
435 bpos_gt(bucket, bucket_end))
438 if (!bch2_dev_bucket_exists(c, bucket))
441 bp_k = bch2_bkey_get_iter(trans, &bp_iter, BTREE_ID_backpointers,
442 bucket_pos_to_bp(c, bucket, bp.bucket_offset),
444 ret = bkey_err(bp_k);
448 if (bp_k.k->type != KEY_TYPE_backpointer ||
449 memcmp(bkey_s_c_to_backpointer(bp_k).v, &bp, sizeof(bp))) {
450 if (last_flushed->level != bp.level ||
451 !bpos_eq(last_flushed->pos, orig_k.k->p)) {
452 last_flushed->level = bp.level;
453 last_flushed->pos = orig_k.k->p;
455 ret = bch2_btree_write_buffer_flush_sync(trans) ?:
456 -BCH_ERR_transaction_restart_write_buffer_flush;
464 bch2_trans_iter_exit(trans, &bp_iter);
468 prt_printf(&buf, "missing backpointer for btree=%s l=%u ",
469 bch2_btree_ids[bp.btree_id], bp.level);
470 bch2_bkey_val_to_text(&buf, c, orig_k);
471 prt_printf(&buf, "\nbp pos ");
472 bch2_bpos_to_text(&buf, bp_iter.pos);
474 if (c->sb.version < bcachefs_metadata_version_backpointers ||
475 c->opts.reconstruct_alloc ||
476 fsck_err(c, "%s", buf.buf))
477 ret = bch2_bucket_backpointer_mod(trans, bucket, bp, orig_k, true);
482 static int check_extent_to_backpointers(struct btree_trans *trans,
483 struct btree_iter *iter,
484 struct bpos bucket_start,
485 struct bpos bucket_end,
486 struct bpos_level *last_flushed)
488 struct bch_fs *c = trans->c;
489 struct bkey_ptrs_c ptrs;
490 const union bch_extent_entry *entry;
491 struct extent_ptr_decoded p;
495 k = bch2_btree_iter_peek_all_levels(iter);
502 ptrs = bch2_bkey_ptrs_c(k);
503 bkey_for_each_ptr_decode(k.k, ptrs, p, entry) {
504 struct bpos bucket_pos;
505 struct bch_backpointer bp;
510 bch2_extent_ptr_to_bp(c, iter->btree_id, iter->path->level,
511 k, p, &bucket_pos, &bp);
513 ret = check_bp_exists(trans, bucket_pos, bp, k,
514 bucket_start, bucket_end,
523 static int check_btree_root_to_backpointers(struct btree_trans *trans,
524 enum btree_id btree_id,
525 struct bpos bucket_start,
526 struct bpos bucket_end,
527 struct bpos_level *last_flushed)
529 struct bch_fs *c = trans->c;
530 struct btree_iter iter;
533 struct bkey_ptrs_c ptrs;
534 struct extent_ptr_decoded p;
535 const union bch_extent_entry *entry;
538 bch2_trans_node_iter_init(trans, &iter, btree_id, POS_MIN, 0,
539 c->btree_roots[btree_id].level, 0);
540 b = bch2_btree_iter_peek_node(&iter);
541 ret = PTR_ERR_OR_ZERO(b);
545 BUG_ON(b != btree_node_root(c, b));
547 k = bkey_i_to_s_c(&b->key);
548 ptrs = bch2_bkey_ptrs_c(k);
549 bkey_for_each_ptr_decode(k.k, ptrs, p, entry) {
550 struct bpos bucket_pos;
551 struct bch_backpointer bp;
556 bch2_extent_ptr_to_bp(c, iter.btree_id, b->c.level + 1,
557 k, p, &bucket_pos, &bp);
559 ret = check_bp_exists(trans, bucket_pos, bp, k,
560 bucket_start, bucket_end,
566 bch2_trans_iter_exit(trans, &iter);
570 static inline struct bbpos bp_to_bbpos(struct bch_backpointer bp)
572 return (struct bbpos) {
573 .btree = bp.btree_id,
578 static size_t btree_nodes_fit_in_ram(struct bch_fs *c)
584 mem_bytes = i.totalram * i.mem_unit;
585 return div_u64(mem_bytes >> 1, btree_bytes(c));
588 int bch2_get_btree_in_memory_pos(struct btree_trans *trans,
589 unsigned btree_leaf_mask,
590 unsigned btree_interior_mask,
591 struct bbpos start, struct bbpos *end)
593 struct btree_iter iter;
595 size_t btree_nodes = btree_nodes_fit_in_ram(trans->c);
599 for (btree = start.btree; btree < BTREE_ID_NR && !ret; btree++) {
600 unsigned depth = ((1U << btree) & btree_leaf_mask) ? 1 : 2;
602 if (!((1U << btree) & btree_leaf_mask) &&
603 !((1U << btree) & btree_interior_mask))
606 bch2_trans_node_iter_init(trans, &iter, btree,
607 btree == start.btree ? start.pos : POS_MIN,
610 * for_each_btree_key_contineu() doesn't check the return value
611 * from bch2_btree_iter_advance(), which is needed when
612 * iterating over interior nodes where we'll see keys at
616 k = __bch2_btree_iter_peek_and_restart(trans, &iter, 0);
623 *end = BBPOS(btree, k.k->p);
624 bch2_trans_iter_exit(trans, &iter);
627 } while (bch2_btree_iter_advance(&iter));
628 bch2_trans_iter_exit(trans, &iter);
635 static int bch2_check_extents_to_backpointers_pass(struct btree_trans *trans,
636 struct bpos bucket_start,
637 struct bpos bucket_end)
639 struct btree_iter iter;
640 enum btree_id btree_id;
641 struct bpos_level last_flushed = { UINT_MAX };
644 for (btree_id = 0; btree_id < BTREE_ID_NR; btree_id++) {
645 unsigned depth = btree_type_has_ptrs(btree_id) ? 0 : 1;
647 bch2_trans_node_iter_init(trans, &iter, btree_id, POS_MIN, 0,
649 BTREE_ITER_ALL_LEVELS|
650 BTREE_ITER_PREFETCH);
653 ret = commit_do(trans, NULL, NULL,
654 BTREE_INSERT_LAZY_RW|
656 check_extent_to_backpointers(trans, &iter,
657 bucket_start, bucket_end,
661 } while (!bch2_btree_iter_advance(&iter));
663 bch2_trans_iter_exit(trans, &iter);
668 ret = commit_do(trans, NULL, NULL,
669 BTREE_INSERT_LAZY_RW|
671 check_btree_root_to_backpointers(trans, btree_id,
672 bucket_start, bucket_end,
680 static struct bpos bucket_pos_to_bp_safe(const struct bch_fs *c,
683 return bch2_dev_exists2(c, bucket.inode)
684 ? bucket_pos_to_bp(c, bucket, 0)
688 int bch2_get_alloc_in_memory_pos(struct btree_trans *trans,
689 struct bpos start, struct bpos *end)
691 struct btree_iter alloc_iter;
692 struct btree_iter bp_iter;
693 struct bkey_s_c alloc_k, bp_k;
694 size_t btree_nodes = btree_nodes_fit_in_ram(trans->c);
695 bool alloc_end = false, bp_end = false;
698 bch2_trans_node_iter_init(trans, &alloc_iter, BTREE_ID_alloc,
700 bch2_trans_node_iter_init(trans, &bp_iter, BTREE_ID_backpointers,
701 bucket_pos_to_bp_safe(trans->c, start), 0, 1, 0);
704 ? __bch2_btree_iter_peek_and_restart(trans, &alloc_iter, 0)
707 ? __bch2_btree_iter_peek_and_restart(trans, &bp_iter, 0)
710 ret = bkey_err(alloc_k) ?: bkey_err(bp_k);
711 if ((!alloc_k.k && !bp_k.k) || ret) {
722 if (bpos_lt(alloc_iter.pos, SPOS_MAX) &&
723 bpos_lt(bucket_pos_to_bp_safe(trans->c, alloc_iter.pos), bp_iter.pos)) {
724 if (!bch2_btree_iter_advance(&alloc_iter))
727 if (!bch2_btree_iter_advance(&bp_iter))
731 bch2_trans_iter_exit(trans, &bp_iter);
732 bch2_trans_iter_exit(trans, &alloc_iter);
736 int bch2_check_extents_to_backpointers(struct bch_fs *c)
738 struct btree_trans trans;
739 struct bpos start = POS_MIN, end;
742 bch2_trans_init(&trans, c, 0, 0);
744 ret = bch2_get_alloc_in_memory_pos(&trans, start, &end);
748 if (bpos_eq(start, POS_MIN) && !bpos_eq(end, SPOS_MAX))
749 bch_verbose(c, "%s(): alloc info does not fit in ram, running in multiple passes with %zu nodes per pass",
750 __func__, btree_nodes_fit_in_ram(c));
752 if (!bpos_eq(start, POS_MIN) || !bpos_eq(end, SPOS_MAX)) {
753 struct printbuf buf = PRINTBUF;
755 prt_str(&buf, "check_extents_to_backpointers(): ");
756 bch2_bpos_to_text(&buf, start);
758 bch2_bpos_to_text(&buf, end);
760 bch_verbose(c, "%s", buf.buf);
764 ret = bch2_check_extents_to_backpointers_pass(&trans, start, end);
765 if (ret || bpos_eq(end, SPOS_MAX))
768 start = bpos_successor(end);
770 bch2_trans_exit(&trans);
775 static int check_one_backpointer(struct btree_trans *trans,
778 struct bkey_s_c_backpointer bp,
779 struct bpos *last_flushed_pos)
781 struct bch_fs *c = trans->c;
782 struct btree_iter iter;
783 struct bbpos pos = bp_to_bbpos(*bp.v);
785 struct printbuf buf = PRINTBUF;
788 if (bbpos_cmp(pos, start) < 0 ||
789 bbpos_cmp(pos, end) > 0)
792 k = bch2_backpointer_get_key(trans, &iter, bp.k->p, *bp.v, 0);
794 if (ret == -BCH_ERR_backpointer_to_overwritten_btree_node)
799 if (!k.k && !bpos_eq(*last_flushed_pos, bp.k->p)) {
800 *last_flushed_pos = bp.k->p;
801 ret = bch2_btree_write_buffer_flush_sync(trans) ?:
802 -BCH_ERR_transaction_restart_write_buffer_flush;
806 if (fsck_err_on(!k.k, c,
807 "backpointer for missing extent\n %s",
808 (bch2_backpointer_k_to_text(&buf, c, bp.s_c), buf.buf)))
809 return bch2_btree_delete_at_buffered(trans, BTREE_ID_backpointers, bp.k->p);
812 bch2_trans_iter_exit(trans, &iter);
817 static int bch2_check_backpointers_to_extents_pass(struct btree_trans *trans,
821 struct btree_iter iter;
823 struct bpos last_flushed_pos = SPOS_MAX;
825 return for_each_btree_key_commit(trans, iter, BTREE_ID_backpointers,
826 POS_MIN, BTREE_ITER_PREFETCH, k,
827 NULL, NULL, BTREE_INSERT_LAZY_RW|BTREE_INSERT_NOFAIL,
828 check_one_backpointer(trans, start, end,
829 bkey_s_c_to_backpointer(k),
833 int bch2_check_backpointers_to_extents(struct bch_fs *c)
835 struct btree_trans trans;
836 struct bbpos start = (struct bbpos) { .btree = 0, .pos = POS_MIN, }, end;
839 bch2_trans_init(&trans, c, 0, 0);
841 ret = bch2_get_btree_in_memory_pos(&trans,
842 (1U << BTREE_ID_extents)|
843 (1U << BTREE_ID_reflink),
849 if (!bbpos_cmp(start, BBPOS_MIN) &&
850 bbpos_cmp(end, BBPOS_MAX))
851 bch_verbose(c, "%s(): extents do not fit in ram, running in multiple passes with %zu nodes per pass",
852 __func__, btree_nodes_fit_in_ram(c));
854 if (bbpos_cmp(start, BBPOS_MIN) ||
855 bbpos_cmp(end, BBPOS_MAX)) {
856 struct printbuf buf = PRINTBUF;
858 prt_str(&buf, "check_backpointers_to_extents(): ");
859 bch2_bbpos_to_text(&buf, start);
861 bch2_bbpos_to_text(&buf, end);
863 bch_verbose(c, "%s", buf.buf);
867 ret = bch2_check_backpointers_to_extents_pass(&trans, start, end);
868 if (ret || !bbpos_cmp(end, BBPOS_MAX))
871 start = bbpos_successor(end);
873 bch2_trans_exit(&trans);