struct btree_key_cache  btree_key_cache;
 
        struct workqueue_struct *btree_update_wq;
-       struct workqueue_struct *btree_error_wq;
+       struct workqueue_struct *btree_io_complete_wq;
        /* copygc needs its own workqueue for index updates.. */
        struct workqueue_struct *copygc_wq;
 
 
        atomic64_t              btree_writes_nr;
        atomic64_t              btree_writes_sectors;
-       struct bio_list         btree_write_error_list;
-       struct work_struct      btree_write_error_work;
        spinlock_t              btree_write_error_lock;
 
        /* ERRORS */
 
        bcachefs_metadata_version_inode_btree_change    = 11,
        bcachefs_metadata_version_snapshot              = 12,
        bcachefs_metadata_version_inode_backpointers    = 13,
-       bcachefs_metadata_version_max                   = 14,
+       bcachefs_metadata_version_btree_ptr_sectors_written = 14,
+       bcachefs_metadata_version_max                   = 15,
 };
 
 #define bcachefs_metadata_version_current      (bcachefs_metadata_version_max - 1)
 
 {
        EBUG_ON(!btree_node_write_in_flight(b));
 
+       clear_btree_node_write_in_flight_inner(b);
        clear_btree_node_write_in_flight(b);
        wake_up_bit(&b->flags, BTREE_NODE_write_in_flight);
 }
        bool updated_range = b->key.k.type == KEY_TYPE_btree_ptr_v2 &&
                BTREE_PTR_RANGE_UPDATED(&bkey_i_to_btree_ptr_v2(&b->key)->v);
        unsigned u64s;
-       unsigned nonblacklisted_written = 0;
+       unsigned blacklisted_written, nonblacklisted_written = 0;
+       unsigned ptr_written = btree_ptr_sectors_written(&b->key);
        int ret, retry_read = 0, write = READ;
 
        b->version_ondisk = U16_MAX;
                             b->data->keys.seq, bp->seq);
        }
 
-       while (b->written < c->opts.btree_node_size) {
+       while (b->written < (ptr_written ?: c->opts.btree_node_size)) {
                unsigned sectors, whiteout_u64s = 0;
                struct nonce nonce;
                struct bch_csum csum;
                btree_err_on(blacklisted && first,
                             BTREE_ERR_FIXABLE, c, ca, b, i,
                             "first btree node bset has blacklisted journal seq");
+
+               btree_err_on(blacklisted && ptr_written,
+                            BTREE_ERR_FIXABLE, c, ca, b, i,
+                            "found blacklisted bset in btree node with sectors_written");
                if (blacklisted && !first)
                        continue;
 
                nonblacklisted_written = b->written;
        }
 
-       for (bne = write_block(b);
-            bset_byte_offset(b, bne) < btree_bytes(c);
-            bne = (void *) bne + block_bytes(c))
-               btree_err_on(bne->keys.seq == b->data->keys.seq &&
-                            !bch2_journal_seq_is_blacklisted(c,
-                                       le64_to_cpu(bne->keys.journal_seq),
-                                       true),
+       if (ptr_written) {
+               btree_err_on(b->written < ptr_written,
                             BTREE_ERR_WANT_RETRY, c, ca, b, NULL,
-                            "found bset signature after last bset");
+                            "btree node data missing: expected %u sectors, found %u",
+                            ptr_written, b->written);
+       } else {
+               for (bne = write_block(b);
+                    bset_byte_offset(b, bne) < btree_bytes(c);
+                    bne = (void *) bne + block_bytes(c))
+                       btree_err_on(bne->keys.seq == b->data->keys.seq &&
+                                    !bch2_journal_seq_is_blacklisted(c,
+                                                                     le64_to_cpu(bne->keys.journal_seq),
+                                                                     true),
+                                    BTREE_ERR_WANT_RETRY, c, ca, b, NULL,
+                                    "found bset signature after last bset");
 
-       /*
-        * Blacklisted bsets are those that were written after the most recent
-        * (flush) journal write. Since there wasn't a flush, they may not have
-        * made it to all devices - which means we shouldn't write new bsets
-        * after them, as that could leave a gap and then reads from that device
-        * wouldn't find all the bsets in that btree node - which means it's
-        * important that we start writing new bsets after the most recent _non_
-        * blacklisted bset:
-        */
-       b->written = nonblacklisted_written;
+               /*
+                * Blacklisted bsets are those that were written after the most recent
+                * (flush) journal write. Since there wasn't a flush, they may not have
+                * made it to all devices - which means we shouldn't write new bsets
+                * after them, as that could leave a gap and then reads from that device
+                * wouldn't find all the bsets in that btree node - which means it's
+                * important that we start writing new bsets after the most recent _non_
+                * blacklisted bset:
+                */
+               blacklisted_written = b->written;
+               b->written = nonblacklisted_written;
+       }
 
        sorted = btree_bounce_alloc(c, btree_bytes(c), &used_mempool);
        sorted->keys.u64s = 0;
                if (ca->mi.state != BCH_MEMBER_STATE_rw)
                        set_btree_node_need_rewrite(b);
        }
+
+       if (!ptr_written)
+               set_btree_node_need_rewrite(b);
 out:
        mempool_free(iter, &c->fill_iter);
        return retry_read;
                        goto do_write;
 
                new &= ~(1U << BTREE_NODE_write_in_flight);
+               new &= ~(1U << BTREE_NODE_write_in_flight_inner);
        } while ((v = cmpxchg(&b->flags, old, new)) != old);
 
        wake_up_bit(&b->flags, BTREE_NODE_write_in_flight);
                        new &= ~(1U << BTREE_NODE_dirty);
                        new &= ~(1U << BTREE_NODE_need_write);
                        new |=  (1U << BTREE_NODE_write_in_flight);
+                       new |=  (1U << BTREE_NODE_write_in_flight_inner);
                        new |=  (1U << BTREE_NODE_just_written);
                        new ^=  (1U << BTREE_NODE_write_idx);
                } else {
                        new &= ~(1U << BTREE_NODE_write_in_flight);
+                       new &= ~(1U << BTREE_NODE_write_in_flight_inner);
                }
        } while ((v = cmpxchg(&b->flags, old, new)) != old);
 
        six_unlock_read(&b->c.lock);
 }
 
-static void bch2_btree_node_write_error(struct bch_fs *c,
-                                       struct btree_write_bio *wbio)
+static void btree_node_write_work(struct work_struct *work)
 {
+       struct btree_write_bio *wbio =
+               container_of(work, struct btree_write_bio, work);
+       struct bch_fs *c        = wbio->wbio.c;
        struct btree *b         = wbio->wbio.bio.bi_private;
-       struct bkey_buf k;
        struct bch_extent_ptr *ptr;
-       struct btree_trans trans;
-       struct btree_iter *iter;
        int ret;
 
-       bch2_bkey_buf_init(&k);
-       bch2_trans_init(&trans, c, 0, 0);
-
-       iter = bch2_trans_get_node_iter(&trans, b->c.btree_id, b->key.k.p,
-                                       BTREE_MAX_DEPTH, b->c.level, 0);
-retry:
-       ret = bch2_btree_iter_traverse(iter);
-       if (ret)
-               goto err;
-
-       /* has node been freed? */
-       if (iter->l[b->c.level].b != b) {
-               /* node has been freed: */
-               BUG_ON(!btree_node_dying(b));
-               goto out;
-       }
-
-       BUG_ON(!btree_node_hashed(b));
-
-       bch2_bkey_buf_copy(&k, c, &b->key);
+       btree_bounce_free(c,
+               wbio->data_bytes,
+               wbio->wbio.used_mempool,
+               wbio->data);
 
-       bch2_bkey_drop_ptrs(bkey_i_to_s(k.k), ptr,
+       bch2_bkey_drop_ptrs(bkey_i_to_s(&wbio->key), ptr,
                bch2_dev_list_has_dev(wbio->wbio.failed, ptr->dev));
 
-       if (!bch2_bkey_nr_ptrs(bkey_i_to_s_c(k.k)))
+       if (!bch2_bkey_nr_ptrs(bkey_i_to_s_c(&wbio->key)))
                goto err;
 
-       ret = bch2_btree_node_update_key(&trans, iter, b, k.k);
-       if (ret == -EINTR)
-               goto retry;
-       if (ret)
-               goto err;
+       if (wbio->wbio.first_btree_write) {
+               if (wbio->wbio.failed.nr) {
+
+               }
+       } else {
+               ret = bch2_trans_do(c, NULL, NULL, 0,
+                       bch2_btree_node_update_key_get_iter(&trans, b, &wbio->key,
+                                                           !wbio->wbio.failed.nr));
+               if (ret)
+                       goto err;
+       }
 out:
-       bch2_trans_iter_put(&trans, iter);
-       bch2_trans_exit(&trans);
-       bch2_bkey_buf_exit(&k, c);
        bio_put(&wbio->wbio.bio);
        btree_node_write_done(c, b);
        return;
        goto out;
 }
 
-void bch2_btree_write_error_work(struct work_struct *work)
-{
-       struct bch_fs *c = container_of(work, struct bch_fs,
-                                       btree_write_error_work);
-       struct bio *bio;
-
-       while (1) {
-               spin_lock_irq(&c->btree_write_error_lock);
-               bio = bio_list_pop(&c->btree_write_error_list);
-               spin_unlock_irq(&c->btree_write_error_lock);
-
-               if (!bio)
-                       break;
-
-               bch2_btree_node_write_error(c,
-                       container_of(bio, struct btree_write_bio, wbio.bio));
-       }
-}
-
-static void btree_node_write_work(struct work_struct *work)
-{
-       struct btree_write_bio *wbio =
-               container_of(work, struct btree_write_bio, work);
-       struct bch_fs *c        = wbio->wbio.c;
-       struct btree *b         = wbio->wbio.bio.bi_private;
-
-       btree_bounce_free(c,
-               wbio->bytes,
-               wbio->wbio.used_mempool,
-               wbio->data);
-
-       if (wbio->wbio.failed.nr) {
-               unsigned long flags;
-
-               spin_lock_irqsave(&c->btree_write_error_lock, flags);
-               bio_list_add(&c->btree_write_error_list, &wbio->wbio.bio);
-               spin_unlock_irqrestore(&c->btree_write_error_lock, flags);
-
-               queue_work(c->btree_error_wq, &c->btree_write_error_work);
-               return;
-       }
-
-       bio_put(&wbio->wbio.bio);
-       btree_node_write_done(c, b);
-}
-
 static void btree_node_write_endio(struct bio *bio)
 {
        struct bch_write_bio *wbio      = to_wbio(bio);
        struct bch_write_bio *parent    = wbio->split ? wbio->parent : NULL;
        struct bch_write_bio *orig      = parent ?: wbio;
+       struct btree_write_bio *wb      = container_of(orig, struct btree_write_bio, wbio);
        struct bch_fs *c                = wbio->c;
+       struct btree *b                 = wbio->bio.bi_private;
        struct bch_dev *ca              = bch_dev_bkey_exists(c, wbio->dev);
        unsigned long flags;
 
        if (parent) {
                bio_put(bio);
                bio_endio(&parent->bio);
-       } else {
-               struct btree_write_bio *wb =
-                       container_of(orig, struct btree_write_bio, wbio);
-
-               INIT_WORK(&wb->work, btree_node_write_work);
-               queue_work(c->io_complete_wq, &wb->work);
+               return;
        }
+
+       clear_btree_node_write_in_flight_inner(b);
+       wake_up_bit(&b->flags, BTREE_NODE_write_in_flight_inner);
+       INIT_WORK(&wb->work, btree_node_write_work);
+       queue_work(c->btree_io_complete_wq, &wb->work);
 }
 
 static int validate_bset_for_write(struct bch_fs *c, struct btree *b,
 static void btree_write_submit(struct work_struct *work)
 {
        struct btree_write_bio *wbio = container_of(work, struct btree_write_bio, work);
+       struct bch_extent_ptr *ptr;
+       __BKEY_PADDED(k, BKEY_BTREE_PTR_VAL_U64s_MAX) tmp;
+
+       bkey_copy(&tmp.k, &wbio->key);
+
+       bkey_for_each_ptr(bch2_bkey_ptrs(bkey_i_to_s(&tmp.k)), ptr)
+               ptr->offset += wbio->sector_offset;
 
-       bch2_submit_wbio_replicas(&wbio->wbio, wbio->wbio.c, BCH_DATA_btree, &wbio->key);
+       bch2_submit_wbio_replicas(&wbio->wbio, wbio->wbio.c, BCH_DATA_btree, &tmp.k);
 }
 
 void __bch2_btree_node_write(struct bch_fs *c, struct btree *b, bool already_started)
        struct bset *i;
        struct btree_node *bn = NULL;
        struct btree_node_entry *bne = NULL;
-       struct bch_extent_ptr *ptr;
        struct sort_iter sort_iter;
        struct nonce nonce;
        unsigned bytes_to_write, sectors_to_write, bytes, u64s;
                new &= ~(1 << BTREE_NODE_dirty);
                new &= ~(1 << BTREE_NODE_need_write);
                new |=  (1 << BTREE_NODE_write_in_flight);
+               new |=  (1 << BTREE_NODE_write_in_flight_inner);
                new |=  (1 << BTREE_NODE_just_written);
                new ^=  (1 << BTREE_NODE_write_idx);
        } while (cmpxchg_acquire(&b->flags, old, new) != old);
                            struct btree_write_bio, wbio.bio);
        wbio_init(&wbio->wbio.bio);
        wbio->data                      = data;
-       wbio->bytes                     = bytes;
+       wbio->data_bytes                = bytes;
+       wbio->sector_offset             = b->written;
        wbio->wbio.c                    = c;
        wbio->wbio.used_mempool         = used_mempool;
+       wbio->wbio.first_btree_write    = !b->written;
        wbio->wbio.bio.bi_end_io        = btree_node_write_endio;
        wbio->wbio.bio.bi_private       = b;
 
        bch2_bio_map(&wbio->wbio.bio, data, sectors_to_write << 9);
 
-       /*
-        * If we're appending to a leaf node, we don't technically need FUA -
-        * this write just needs to be persisted before the next journal write,
-        * which will be marked FLUSH|FUA.
-        *
-        * Similarly if we're writing a new btree root - the pointer is going to
-        * be in the next journal entry.
-        *
-        * But if we're writing a new btree node (that isn't a root) or
-        * appending to a non leaf btree node, we need either FUA or a flush
-        * when we write the parent with the new pointer. FUA is cheaper than a
-        * flush, and writes appending to leaf nodes aren't blocking anything so
-        * just make all btree node writes FUA to keep things sane.
-        */
-
        bkey_copy(&wbio->key, &b->key);
 
-       bkey_for_each_ptr(bch2_bkey_ptrs(bkey_i_to_s(&wbio->key)), ptr)
-               ptr->offset += b->written;
-
        b->written += sectors_to_write;
 
+       if (wbio->wbio.first_btree_write &&
+           b->key.k.type == KEY_TYPE_btree_ptr_v2)
+               bkey_i_to_btree_ptr_v2(&b->key)->v.sectors_written =
+                       cpu_to_le16(b->written);
+
+       if (wbio->key.k.type == KEY_TYPE_btree_ptr_v2)
+               bkey_i_to_btree_ptr_v2(&wbio->key)->v.sectors_written =
+                       cpu_to_le16(b->written);
+
        atomic64_inc(&c->btree_writes_nr);
        atomic64_add(sectors_to_write, &c->btree_writes_sectors);
 
        return;
 err:
        set_btree_node_noevict(b);
+       if (!b->written &&
+           b->key.k.type == KEY_TYPE_btree_ptr_v2)
+               bkey_i_to_btree_ptr_v2(&b->key)->v.sectors_written =
+                       cpu_to_le16(sectors_to_write);
        b->written += sectors_to_write;
 nowrite:
        btree_bounce_free(c, bytes, used_mempool, data);
 
                atomic_dec(&c->btree_cache.dirty);
 }
 
+static inline unsigned btree_ptr_sectors_written(struct bkey_i *k)
+{
+       return k->k.type == KEY_TYPE_btree_ptr_v2
+               ? le16_to_cpu(bkey_i_to_btree_ptr_v2(k)->v.sectors_written)
+               : 0;
+}
+
 struct btree_read_bio {
        struct bch_fs           *c;
        struct btree            *b;
        struct work_struct      work;
        __BKEY_PADDED(key, BKEY_BTREE_PTR_VAL_U64s_MAX);
        void                    *data;
-       unsigned                bytes;
+       unsigned                data_bytes;
+       unsigned                sector_offset;
        struct bch_write_bio    wbio;
 };
 
 
 void bch2_btree_complete_write(struct bch_fs *, struct btree *,
                              struct btree_write *);
-void bch2_btree_write_error_work(struct work_struct *);
 
 void __bch2_btree_node_write(struct bch_fs *, struct btree *, bool);
 bool bch2_btree_post_write_cleanup(struct bch_fs *, struct btree *);
 
 
 static inline void bch2_btree_iter_downgrade(struct btree_iter *iter)
 {
-       unsigned new_locks_want = (iter->flags & BTREE_ITER_INTENT ? 1 : 0);
+       unsigned new_locks_want = iter->level + !!(iter->flags & BTREE_ITER_INTENT);
 
        if (iter->locks_want > new_locks_want)
                __bch2_btree_iter_downgrade(iter, new_locks_want);
 
        BTREE_NODE_write_idx,
        BTREE_NODE_accessed,
        BTREE_NODE_write_in_flight,
+       BTREE_NODE_write_in_flight_inner,
        BTREE_NODE_just_written,
        BTREE_NODE_dying,
        BTREE_NODE_fake,
 BTREE_FLAG(write_idx);
 BTREE_FLAG(accessed);
 BTREE_FLAG(write_in_flight);
+BTREE_FLAG(write_in_flight_inner);
 BTREE_FLAG(just_written);
 BTREE_FLAG(dying);
 BTREE_FLAG(fake);
 
                            __le64, unsigned);
 void bch2_btree_node_rewrite_async(struct bch_fs *, struct btree *);
 int bch2_btree_node_update_key(struct btree_trans *, struct btree_iter *,
-                              struct btree *, struct bkey_i *);
+                              struct btree *, struct bkey_i *, bool);
+int bch2_btree_node_update_key_get_iter(struct btree_trans *,
+                               struct btree *, struct bkey_i *, bool);
 
 int bch2_trans_update(struct btree_trans *, struct btree_iter *,
                      struct bkey_i *, enum btree_update_flags);
 
                goto retry;
        }
 
-       if (c->sb.features & (1ULL << BCH_FEATURE_btree_ptr_v2))
-               bkey_btree_ptr_v2_init(&tmp.k);
-       else
-               bkey_btree_ptr_init(&tmp.k);
-
+       bkey_btree_ptr_v2_init(&tmp.k);
        bch2_alloc_sectors_append_ptrs(c, wp, &tmp.k, c->opts.btree_node_size);
 
        bch2_open_bucket_get(c, wp, &ob);
                six_unlock_read(&old->c.lock);
 
                if (seq == as->old_nodes_seq[i])
-                       bch2_btree_node_wait_on_write(old);
+                       wait_on_bit_io(&old->flags, BTREE_NODE_write_in_flight_inner,
+                                      TASK_UNINTERRUPTIBLE);
        }
 
        /*
        struct bkey_packed *k;
        const char *invalid;
 
+       BUG_ON(insert->k.type == KEY_TYPE_btree_ptr_v2 &&
+              !btree_ptr_sectors_written(insert));
+
        invalid = bch2_bkey_invalid(c, bkey_i_to_s_c(insert), btree_node_type(b)) ?:
                bch2_bkey_in_btree_node(b, bkey_i_to_s_c(insert));
        if (invalid) {
                six_unlock_write(&n2->c.lock);
                six_unlock_write(&n1->c.lock);
 
+               bch2_btree_node_write(c, n1, SIX_LOCK_intent);
                bch2_btree_node_write(c, n2, SIX_LOCK_intent);
 
                /*
                bch2_btree_build_aux_trees(n1);
                six_unlock_write(&n1->c.lock);
 
+               bch2_btree_node_write(c, n1, SIX_LOCK_intent);
+
                if (parent)
                        bch2_keylist_add(&as->parent_keys, &n1->key);
        }
 
-       bch2_btree_node_write(c, n1, SIX_LOCK_intent);
-
        /* New nodes all written, now make them visible: */
 
        if (parent) {
        bch2_btree_build_aux_trees(n);
        six_unlock_write(&n->c.lock);
 
+       bch2_btree_node_write(c, n, SIX_LOCK_intent);
+
        bkey_init(&delete.k);
        delete.k.p = prev->key.k.p;
        bch2_keylist_add(&as->parent_keys, &delete);
        bch2_keylist_add(&as->parent_keys, &n->key);
 
-       bch2_btree_node_write(c, n, SIX_LOCK_intent);
-
        bch2_btree_insert_node(as, trans, iter, parent, &as->parent_keys, flags);
 
        bch2_btree_update_get_open_buckets(as, n);
        queue_work(c->btree_interior_update_worker, &a->work);
 }
 
-static void __bch2_btree_node_update_key(struct btree_update *as,
-                                        struct btree_trans *trans,
-                                        struct btree_iter *iter,
-                                        struct btree *b, struct btree *new_hash,
-                                        struct bkey_i *new_key)
+static int __bch2_btree_node_update_key(struct btree_trans *trans,
+                                       struct btree_iter *iter,
+                                       struct btree *b, struct btree *new_hash,
+                                       struct bkey_i *new_key,
+                                       bool skip_triggers)
 {
-       struct bch_fs *c = as->c;
+       struct bch_fs *c = trans->c;
+       struct btree_iter *iter2 = NULL;
        struct btree *parent;
+       u64 journal_entries[BKEY_BTREE_PTR_U64s_MAX];
        int ret;
 
-       btree_update_will_delete_key(as, &b->key);
-       btree_update_will_add_key(as, new_key);
+       if (!skip_triggers) {
+               ret = bch2_trans_mark_key(trans,
+                                         bkey_s_c_null,
+                                         bkey_i_to_s_c(new_key),
+                                         BTREE_TRIGGER_INSERT);
+               if (ret)
+                       return ret;
+
+               ret = bch2_trans_mark_key(trans,
+                                         bkey_i_to_s_c(&b->key),
+                                         bkey_s_c_null,
+                                         BTREE_TRIGGER_OVERWRITE);
+               if (ret)
+                       return ret;
+       }
+
+       if (new_hash) {
+               bkey_copy(&new_hash->key, new_key);
+               ret = bch2_btree_node_hash_insert(&c->btree_cache,
+                               new_hash, b->c.level, b->c.btree_id);
+               BUG_ON(ret);
+       }
 
        parent = btree_node_parent(iter, b);
        if (parent) {
-               if (new_hash) {
-                       bkey_copy(&new_hash->key, new_key);
-                       ret = bch2_btree_node_hash_insert(&c->btree_cache,
-                                       new_hash, b->c.level, b->c.btree_id);
-                       BUG_ON(ret);
-               }
+               iter2 = bch2_trans_copy_iter(trans, iter);
 
-               bch2_keylist_add(&as->parent_keys, new_key);
-               bch2_btree_insert_node(as, trans, iter, parent, &as->parent_keys, 0);
+               BUG_ON(iter2->level != b->c.level);
+               BUG_ON(bpos_cmp(iter2->pos, new_key->k.p));
 
-               if (new_hash) {
-                       mutex_lock(&c->btree_cache.lock);
-                       bch2_btree_node_hash_remove(&c->btree_cache, new_hash);
+               btree_node_unlock(iter2, iter2->level);
+               iter2->l[iter2->level].b = BTREE_ITER_NO_NODE_UP;
+               iter2->level++;
 
-                       bch2_btree_node_hash_remove(&c->btree_cache, b);
-
-                       bkey_copy(&b->key, new_key);
-                       ret = __bch2_btree_node_hash_insert(&c->btree_cache, b);
-                       BUG_ON(ret);
-                       mutex_unlock(&c->btree_cache.lock);
-               } else {
-                       bkey_copy(&b->key, new_key);
-               }
+               ret   = bch2_btree_iter_traverse(iter2) ?:
+                       bch2_trans_update(trans, iter2, new_key, BTREE_TRIGGER_NORUN);
+               if (ret)
+                       goto err;
        } else {
                BUG_ON(btree_node_root(c, b) != b);
 
-               bch2_btree_node_lock_write(b, iter);
-               bkey_copy(&b->key, new_key);
+               trans->extra_journal_entries = (void *) &journal_entries[0];
+               trans->extra_journal_entry_u64s =
+                       journal_entry_set((void *) &journal_entries[0],
+                                         BCH_JSET_ENTRY_btree_root,
+                                         b->c.btree_id, b->c.level,
+                                         new_key, new_key->k.u64s);
+       }
 
-               if (btree_ptr_hash_val(&b->key) != b->hash_val) {
-                       mutex_lock(&c->btree_cache.lock);
-                       bch2_btree_node_hash_remove(&c->btree_cache, b);
+       ret = bch2_trans_commit(trans, NULL, NULL,
+                               BTREE_INSERT_NOFAIL|
+                               BTREE_INSERT_NOCHECK_RW|
+                               BTREE_INSERT_JOURNAL_RECLAIM|
+                               BTREE_INSERT_JOURNAL_RESERVED|
+                               BTREE_INSERT_NOUNLOCK);
+       if (ret)
+               goto err;
 
-                       ret = __bch2_btree_node_hash_insert(&c->btree_cache, b);
-                       BUG_ON(ret);
-                       mutex_unlock(&c->btree_cache.lock);
-               }
+       bch2_btree_node_lock_write(b, iter);
 
-               btree_update_updated_root(as, b);
-               bch2_btree_node_unlock_write(b, iter);
+       if (new_hash) {
+               mutex_lock(&c->btree_cache.lock);
+               bch2_btree_node_hash_remove(&c->btree_cache, new_hash);
+               bch2_btree_node_hash_remove(&c->btree_cache, b);
+
+               bkey_copy(&b->key, new_key);
+               ret = __bch2_btree_node_hash_insert(&c->btree_cache, b);
+               BUG_ON(ret);
+               mutex_unlock(&c->btree_cache.lock);
+       } else {
+               bkey_copy(&b->key, new_key);
        }
 
-       bch2_btree_update_done(as);
+       bch2_btree_node_unlock_write(b, iter);
+out:
+       bch2_trans_iter_put(trans, iter2);
+       return ret;
+err:
+       if (new_hash) {
+               mutex_lock(&c->btree_cache.lock);
+               bch2_btree_node_hash_remove(&c->btree_cache, b);
+               mutex_unlock(&c->btree_cache.lock);
+       }
+       goto out;
 }
 
-int bch2_btree_node_update_key(struct btree_trans *trans,
-                              struct btree_iter *iter,
-                              struct btree *b,
-                              struct bkey_i *new_key)
+int bch2_btree_node_update_key(struct btree_trans *trans, struct btree_iter *iter,
+                              struct btree *b, struct bkey_i *new_key,
+                              bool skip_triggers)
 {
        struct bch_fs *c = trans->c;
-       struct btree *parent = btree_node_parent(iter, b);
-       struct btree_update *as = NULL;
        struct btree *new_hash = NULL;
        struct closure cl;
        int ret = 0;
        if (btree_ptr_hash_val(new_key) != b->hash_val) {
                ret = bch2_btree_cache_cannibalize_lock(c, &cl);
                if (ret) {
-                       bch2_trans_unlock(iter->trans);
+                       bch2_trans_unlock(trans);
                        closure_sync(&cl);
-                       if (!bch2_trans_relock(iter->trans))
+                       if (!bch2_trans_relock(trans))
                                return -EINTR;
                }
 
                new_hash = bch2_btree_node_mem_alloc(c);
        }
 
-       as = bch2_btree_update_start(iter, b->c.level,
-               parent ? btree_update_reserve_required(c, parent) : 0,
-               BTREE_INSERT_NOFAIL);
-       if (IS_ERR(as)) {
-               ret = PTR_ERR(as);
-               goto err;
-       }
-
-       __bch2_btree_node_update_key(as, trans, iter, b, new_hash, new_key);
+       ret = __bch2_btree_node_update_key(trans, iter, b, new_hash,
+                                          new_key, skip_triggers);
 
-       bch2_btree_iter_downgrade(iter);
-err:
        if (new_hash) {
                mutex_lock(&c->btree_cache.lock);
                list_move(&new_hash->list, &c->btree_cache.freeable);
        return ret;
 }
 
+int bch2_btree_node_update_key_get_iter(struct btree_trans *trans,
+                                       struct btree *b, struct bkey_i *new_key,
+                                       bool skip_triggers)
+{
+       struct btree_iter *iter;
+       int ret;
+
+       iter = bch2_trans_get_node_iter(trans, b->c.btree_id, b->key.k.p,
+                                       BTREE_MAX_DEPTH, b->c.level,
+                                       BTREE_ITER_INTENT);
+       ret = bch2_btree_iter_traverse(iter);
+       if (ret)
+               goto out;
+
+       /* has node been freed? */
+       if (iter->l[b->c.level].b != b) {
+               /* node has been freed: */
+               BUG_ON(!btree_node_dying(b));
+               goto out;
+       }
+
+       BUG_ON(!btree_node_hashed(b));
+
+       ret = bch2_btree_node_update_key(trans, iter, b, new_key, skip_triggers);
+out:
+       bch2_trans_iter_put(trans, iter);
+       return ret;
+}
+
 /* Init code: */
 
 /*
 
        unsigned u64s, reset_flags = 0;
        int ret = 0;
 
-       if (!trans->nr_updates)
+       if (!trans->nr_updates &&
+           !trans->extra_journal_entry_u64s)
                goto out_reset;
 
        if (trans->flags & BTREE_INSERT_GC_LOCK_HELD)
 
                                bounce:1,
                                put_bio:1,
                                have_ioref:1,
-                               used_mempool:1;
+                               used_mempool:1,
+                               first_btree_write:1;
        );
 
        struct bio              bio;
 
                                break;
                        }
 
-                       ret = bch2_btree_node_update_key(&trans, iter, b, k.k);
+                       ret = bch2_btree_node_update_key(&trans, iter, b, k.k, false);
                        if (ret == -EINTR) {
                                b = bch2_btree_iter_peek_node(iter);
                                ret = 0;
 
                c->opts.fix_errors      = FSCK_OPT_YES;
        }
 
+       if (c->sb.version < bcachefs_metadata_version_btree_ptr_sectors_written) {
+               bch_info(c, "version prior to btree_ptr_sectors_written, upgrade required");
+               c->opts.version_upgrade = true;
+       }
+
        ret = bch2_blacklist_table_initialize(c);
        if (ret) {
                bch_err(c, "error initializing blacklist table");
 
                destroy_workqueue(c->io_complete_wq );
        if (c->copygc_wq)
                destroy_workqueue(c->copygc_wq);
-       if (c->btree_error_wq)
-               destroy_workqueue(c->btree_error_wq);
+       if (c->btree_io_complete_wq)
+               destroy_workqueue(c->btree_io_complete_wq);
        if (c->btree_update_wq)
                destroy_workqueue(c->btree_update_wq);
 
        for_each_member_device(ca, c, i)
                cancel_work_sync(&ca->io_error_work);
 
-       cancel_work_sync(&c->btree_write_error_work);
        cancel_work_sync(&c->read_only_work);
 }
 
 
        mutex_init(&c->bio_bounce_pages_lock);
 
-       bio_list_init(&c->btree_write_error_list);
        spin_lock_init(&c->btree_write_error_lock);
-       INIT_WORK(&c->btree_write_error_work, bch2_btree_write_error_work);
 
        INIT_WORK(&c->journal_seq_blacklist_gc_work,
                  bch2_blacklist_entries_gc);
 
        if (!(c->btree_update_wq = alloc_workqueue("bcachefs",
                                WQ_FREEZABLE|WQ_MEM_RECLAIM, 1)) ||
-           !(c->btree_error_wq = alloc_workqueue("bcachefs_error",
+           !(c->btree_io_complete_wq = alloc_workqueue("bcachefs_btree_io",
                                WQ_FREEZABLE|WQ_MEM_RECLAIM, 1)) ||
            !(c->copygc_wq = alloc_workqueue("bcachefs_copygc",
                                WQ_FREEZABLE|WQ_MEM_RECLAIM|WQ_CPU_INTENSIVE, 1)) ||