!memcmp(l.v, r.v, bkey_val_bytes(l.k));
 }
 
+struct extents_to_bp_state {
+       struct bpos     bucket_start;
+       struct bpos     bucket_end;
+       struct bkey_buf last_flushed;
+};
+
 static int check_bp_exists(struct btree_trans *trans,
+                          struct extents_to_bp_state *s,
                           struct bpos bucket,
                           struct bch_backpointer bp,
-                          struct bkey_s_c orig_k,
-                          struct bpos bucket_start,
-                          struct bpos bucket_end,
-                          struct bkey_buf *last_flushed)
+                          struct bkey_s_c orig_k)
 {
        struct bch_fs *c = trans->c;
        struct btree_iter bp_iter = { NULL };
 
        bch2_bkey_buf_init(&tmp);
 
-       if (bpos_lt(bucket, bucket_start) ||
-           bpos_gt(bucket, bucket_end))
+       if (bpos_lt(bucket, s->bucket_start) ||
+           bpos_gt(bucket, s->bucket_end))
                return 0;
 
        if (!bch2_dev_bucket_exists(c, bucket))
 
        if (bp_k.k->type != KEY_TYPE_backpointer ||
            memcmp(bkey_s_c_to_backpointer(bp_k).v, &bp, sizeof(bp))) {
-               if (!bkey_and_val_eq(orig_k, bkey_i_to_s_c(last_flushed->k))) {
-                       bch2_bkey_buf_reassemble(&tmp, c, orig_k);
+               bch2_bkey_buf_reassemble(&tmp, c, orig_k);
 
+               if (!bkey_and_val_eq(orig_k, bkey_i_to_s_c(s->last_flushed.k))) {
                        if (bp.level) {
                                bch2_trans_unlock(trans);
                                bch2_btree_interior_updates_flush(c);
                        if (ret)
                                goto err;
 
-                       bch2_bkey_buf_copy(last_flushed, c, tmp.k);
+                       bch2_bkey_buf_copy(&s->last_flushed, c, tmp.k);
                        ret = -BCH_ERR_transaction_restart_write_buffer_flush;
                        goto out;
                }
 }
 
 static int check_extent_to_backpointers(struct btree_trans *trans,
+                                       struct extents_to_bp_state *s,
                                        enum btree_id btree, unsigned level,
-                                       struct bpos bucket_start,
-                                       struct bpos bucket_end,
-                                       struct bkey_buf *last_flushed,
                                        struct bkey_s_c k)
 {
        struct bch_fs *c = trans->c;
                bch2_extent_ptr_to_bp(c, btree, level,
                                      k, p, &bucket_pos, &bp);
 
-               ret = check_bp_exists(trans, bucket_pos, bp, k,
-                                     bucket_start, bucket_end,
-                                     last_flushed);
+               ret = check_bp_exists(trans, s, bucket_pos, bp, k);
                if (ret)
                        return ret;
        }
 }
 
 static int check_btree_root_to_backpointers(struct btree_trans *trans,
+                                           struct extents_to_bp_state *s,
                                            enum btree_id btree_id,
-                                           struct bpos bucket_start,
-                                           struct bpos bucket_end,
-                                           struct bkey_buf *last_flushed,
                                            int *level)
 {
        struct bch_fs *c = trans->c;
        *level = b->c.level;
 
        k = bkey_i_to_s_c(&b->key);
-       ret = check_extent_to_backpointers(trans, btree_id, b->c.level + 1,
-                                     bucket_start, bucket_end,
-                                     last_flushed, k);
+       ret = check_extent_to_backpointers(trans, s, btree_id, b->c.level + 1, k);
 err:
        bch2_trans_iter_exit(trans, &iter);
        return ret;
 }
 
 static int bch2_check_extents_to_backpointers_pass(struct btree_trans *trans,
-                                                  struct bpos bucket_start,
-                                                  struct bpos bucket_end)
+                                                  struct extents_to_bp_state *s)
 {
        struct bch_fs *c = trans->c;
-       struct btree_iter iter;
-       enum btree_id btree_id;
-       struct bkey_s_c k;
-       struct bkey_buf last_flushed;
        int ret = 0;
 
-       bch2_bkey_buf_init(&last_flushed);
-       bkey_init(&last_flushed.k->k);
-
-       for (btree_id = 0; btree_id < btree_id_nr_alive(c); btree_id++) {
+       for (enum btree_id btree_id = 0;
+            btree_id < btree_id_nr_alive(c);
+            btree_id++) {
                int level, depth = btree_type_has_ptrs(btree_id) ? 0 : 1;
 
                ret = commit_do(trans, NULL, NULL,
                                BCH_TRANS_COMMIT_no_enospc,
-                               check_btree_root_to_backpointers(trans, btree_id,
-                                                       bucket_start, bucket_end,
-                                                       &last_flushed, &level));
+                               check_btree_root_to_backpointers(trans, s, btree_id, &level));
                if (ret)
                        return ret;
 
                while (level >= depth) {
+                       struct btree_iter iter;
                        bch2_trans_node_iter_init(trans, &iter, btree_id, POS_MIN, 0,
                                                  level,
                                                  BTREE_ITER_PREFETCH);
                        while (1) {
                                bch2_trans_begin(trans);
-                               k = bch2_btree_iter_peek(&iter);
+
+                               struct bkey_s_c k = bch2_btree_iter_peek(&iter);
                                if (!k.k)
                                        break;
                                ret = bkey_err(k) ?:
-                                       check_extent_to_backpointers(trans, btree_id, level,
-                                                                    bucket_start, bucket_end,
-                                                                    &last_flushed, k) ?:
+                                       check_extent_to_backpointers(trans, s, btree_id, level, k) ?:
                                        bch2_trans_commit(trans, NULL, NULL,
                                                          BCH_TRANS_COMMIT_no_enospc);
                                if (bch2_err_matches(ret, BCH_ERR_transaction_restart)) {
                }
        }
 
-       bch2_bkey_buf_exit(&last_flushed, c);
        return 0;
 }
 
 int bch2_check_extents_to_backpointers(struct bch_fs *c)
 {
        struct btree_trans *trans = bch2_trans_get(c);
-       struct bpos start = POS_MIN, end;
+       struct extents_to_bp_state s = { .bucket_start = POS_MIN };
        int ret;
 
+       bch2_bkey_buf_init(&s.last_flushed);
+       bkey_init(&s.last_flushed.k->k);
+
        while (1) {
-               ret = bch2_get_alloc_in_memory_pos(trans, start, &end);
+               ret = bch2_get_alloc_in_memory_pos(trans, s.bucket_start, &s.bucket_end);
                if (ret)
                        break;
 
-               if (bpos_eq(start, POS_MIN) && !bpos_eq(end, SPOS_MAX))
+               if ( bpos_eq(s.bucket_start, POS_MIN) &&
+                   !bpos_eq(s.bucket_end, SPOS_MAX))
                        bch_verbose(c, "%s(): alloc info does not fit in ram, running in multiple passes with %zu nodes per pass",
                                    __func__, btree_nodes_fit_in_ram(c));
 
-               if (!bpos_eq(start, POS_MIN) || !bpos_eq(end, SPOS_MAX)) {
+               if (!bpos_eq(s.bucket_start, POS_MIN) ||
+                   !bpos_eq(s.bucket_end, SPOS_MAX)) {
                        struct printbuf buf = PRINTBUF;
 
                        prt_str(&buf, "check_extents_to_backpointers(): ");
-                       bch2_bpos_to_text(&buf, start);
+                       bch2_bpos_to_text(&buf, s.bucket_start);
                        prt_str(&buf, "-");
-                       bch2_bpos_to_text(&buf, end);
+                       bch2_bpos_to_text(&buf, s.bucket_end);
 
                        bch_verbose(c, "%s", buf.buf);
                        printbuf_exit(&buf);
                }
 
-               ret = bch2_check_extents_to_backpointers_pass(trans, start, end);
-               if (ret || bpos_eq(end, SPOS_MAX))
+               ret = bch2_check_extents_to_backpointers_pass(trans, &s);
+               if (ret || bpos_eq(s.bucket_end, SPOS_MAX))
                        break;
 
-               start = bpos_successor(end);
+               s.bucket_start = bpos_successor(s.bucket_end);
        }
        bch2_trans_put(trans);
+       bch2_bkey_buf_exit(&s.last_flushed, c);
 
        bch_err_fn(c, ret);
        return ret;