[bcachefs-tools-debian] / libbcachefs / btree_update_interior.c

// SPDX-License-Identifier: GPL-2.0

#include "bcachefs.h"
#include "alloc_foreground.h"
#include "bkey_methods.h"
#include "btree_cache.h"
#include "btree_gc.h"
#include "btree_journal_iter.h"
#include "btree_update.h"
#include "btree_update_interior.h"
#include "btree_io.h"
#include "btree_iter.h"
#include "btree_locking.h"
#include "buckets.h"
#include "clock.h"
#include "error.h"
#include "extents.h"
#include "journal.h"
#include "journal_reclaim.h"
#include "keylist.h"
#include "replicas.h"
#include "super-io.h"
#include "trace.h"

#include <linux/random.h>

static int bch2_btree_insert_node(struct btree_update *, struct btree_trans *,
                                  btree_path_idx_t, struct btree *,
                                  struct keylist *, unsigned);
static void bch2_btree_update_add_new_node(struct btree_update *, struct btree *);

static btree_path_idx_t get_unlocked_mut_path(struct btree_trans *trans,
                                              enum btree_id btree_id,
                                              unsigned level,
                                              struct bpos pos)
{
        btree_path_idx_t path_idx = bch2_path_get(trans, btree_id, pos, level + 1, level,
                             BTREE_ITER_NOPRESERVE|
                             BTREE_ITER_INTENT, _RET_IP_);
        path_idx = bch2_btree_path_make_mut(trans, path_idx, true, _RET_IP_);

        struct btree_path *path = trans->paths + path_idx;
        bch2_btree_path_downgrade(trans, path);
        __bch2_btree_path_unlock(trans, path);
        return path_idx;
}

/* Debug code: */

/*
 * Verify that child nodes correctly span parent node's range:
 */
static void btree_node_interior_verify(struct bch_fs *c, struct btree *b)
{
#ifdef CONFIG_BCACHEFS_DEBUG
        struct bpos next_node = b->data->min_key;
        struct btree_node_iter iter;
        struct bkey_s_c k;
        struct bkey_s_c_btree_ptr_v2 bp;
        struct bkey unpacked;
        struct printbuf buf1 = PRINTBUF, buf2 = PRINTBUF;

        BUG_ON(!b->c.level);

        if (!test_bit(JOURNAL_REPLAY_DONE, &c->journal.flags))
                return;

        bch2_btree_node_iter_init_from_start(&iter, b);

        while (1) {
                k = bch2_btree_node_iter_peek_unpack(&iter, b, &unpacked);
                if (k.k->type != KEY_TYPE_btree_ptr_v2)
                        break;
                bp = bkey_s_c_to_btree_ptr_v2(k);

                if (!bpos_eq(next_node, bp.v->min_key)) {
                        bch2_dump_btree_node(c, b);
                        bch2_bpos_to_text(&buf1, next_node);
                        bch2_bpos_to_text(&buf2, bp.v->min_key);
                        panic("expected next min_key %s got %s\n", buf1.buf, buf2.buf);
                }

                bch2_btree_node_iter_advance(&iter, b);

                if (bch2_btree_node_iter_end(&iter)) {
                        if (!bpos_eq(k.k->p, b->key.k.p)) {
                                bch2_dump_btree_node(c, b);
                                bch2_bpos_to_text(&buf1, b->key.k.p);
                                bch2_bpos_to_text(&buf2, k.k->p);
                                panic("expected end %s got %s\n", buf1.buf, buf2.buf);
                        }
                        break;
                }

                next_node = bpos_successor(k.k->p);
        }
#endif
}

/* Calculate ideal packed bkey format for new btree nodes: */

static void __bch2_btree_calc_format(struct bkey_format_state *s, struct btree *b)
{
        struct bkey_packed *k;
        struct bset_tree *t;
        struct bkey uk;

        for_each_bset(b, t)
                bset_tree_for_each_key(b, t, k)
                        if (!bkey_deleted(k)) {
                                uk = bkey_unpack_key(b, k);
                                bch2_bkey_format_add_key(s, &uk);
                        }
}

static struct bkey_format bch2_btree_calc_format(struct btree *b)
{
        struct bkey_format_state s;

        bch2_bkey_format_init(&s);
        bch2_bkey_format_add_pos(&s, b->data->min_key);
        bch2_bkey_format_add_pos(&s, b->data->max_key);
        __bch2_btree_calc_format(&s, b);

        return bch2_bkey_format_done(&s);
}

static size_t btree_node_u64s_with_format(struct btree_nr_keys nr,
                                          struct bkey_format *old_f,
                                          struct bkey_format *new_f)
{
        /* stupid integer promotion rules */
        ssize_t delta =
            (((int) new_f->key_u64s - old_f->key_u64s) *
             (int) nr.packed_keys) +
            (((int) new_f->key_u64s - BKEY_U64s) *
             (int) nr.unpacked_keys);

        BUG_ON(delta + nr.live_u64s < 0);

        return nr.live_u64s + delta;
}

/**
 * bch2_btree_node_format_fits - check if we could rewrite node with a new format
 *
 * @c:          filesystem handle
 * @b:          btree node to rewrite
 * @nr:         number of keys for new node (i.e. b->nr)
 * @new_f:      bkey format to translate keys to
 *
 * Returns: true if all re-packed keys will be able to fit in a new node.
 *
 * Assumes all keys will successfully pack with the new format.
 */
static bool bch2_btree_node_format_fits(struct bch_fs *c, struct btree *b,
                                 struct btree_nr_keys nr,
                                 struct bkey_format *new_f)
{
        size_t u64s = btree_node_u64s_with_format(nr, &b->format, new_f);

        return __vstruct_bytes(struct btree_node, u64s) < btree_buf_bytes(b);
}

/* Btree node freeing/allocation: */

static void __btree_node_free(struct btree_trans *trans, struct btree *b)
{
        struct bch_fs *c = trans->c;

        trace_and_count(c, btree_node_free, trans, b);

        BUG_ON(btree_node_write_blocked(b));
        BUG_ON(btree_node_dirty(b));
        BUG_ON(btree_node_need_write(b));
        BUG_ON(b == btree_node_root(c, b));
        BUG_ON(b->ob.nr);
        BUG_ON(!list_empty(&b->write_blocked));
        BUG_ON(b->will_make_reachable);

        clear_btree_node_noevict(b);

        mutex_lock(&c->btree_cache.lock);
        list_move(&b->list, &c->btree_cache.freeable);
        mutex_unlock(&c->btree_cache.lock);
}

static void bch2_btree_node_free_inmem(struct btree_trans *trans,
                                       struct btree_path *path,
                                       struct btree *b)
{
        struct bch_fs *c = trans->c;
        unsigned i, level = b->c.level;

        bch2_btree_node_lock_write_nofail(trans, path, &b->c);
        bch2_btree_node_hash_remove(&c->btree_cache, b);
        __btree_node_free(trans, b);
        six_unlock_write(&b->c.lock);
        mark_btree_node_locked_noreset(path, level, BTREE_NODE_INTENT_LOCKED);

        trans_for_each_path(trans, path, i)
                if (path->l[level].b == b) {
                        btree_node_unlock(trans, path, level);
                        path->l[level].b = ERR_PTR(-BCH_ERR_no_btree_node_init);
                }
}

static void bch2_btree_node_free_never_used(struct btree_update *as,
                                            struct btree_trans *trans,
                                            struct btree *b)
{
        struct bch_fs *c = as->c;
        struct prealloc_nodes *p = &as->prealloc_nodes[b->c.lock.readers != NULL];
        struct btree_path *path;
        unsigned i, level = b->c.level;

        BUG_ON(!list_empty(&b->write_blocked));
        BUG_ON(b->will_make_reachable != (1UL|(unsigned long) as));

        b->will_make_reachable = 0;
        closure_put(&as->cl);

        clear_btree_node_will_make_reachable(b);
        clear_btree_node_accessed(b);
        clear_btree_node_dirty_acct(c, b);
        clear_btree_node_need_write(b);

        mutex_lock(&c->btree_cache.lock);
        list_del_init(&b->list);
        bch2_btree_node_hash_remove(&c->btree_cache, b);
        mutex_unlock(&c->btree_cache.lock);

        BUG_ON(p->nr >= ARRAY_SIZE(p->b));
        p->b[p->nr++] = b;

        six_unlock_intent(&b->c.lock);

        trans_for_each_path(trans, path, i)
                if (path->l[level].b == b) {
                        btree_node_unlock(trans, path, level);
                        path->l[level].b = ERR_PTR(-BCH_ERR_no_btree_node_init);
                }
}

static struct btree *__bch2_btree_node_alloc(struct btree_trans *trans,
                                             struct disk_reservation *res,
                                             struct closure *cl,
                                             bool interior_node,
                                             unsigned flags)
{
        struct bch_fs *c = trans->c;
        struct write_point *wp;
        struct btree *b;
        BKEY_PADDED_ONSTACK(k, BKEY_BTREE_PTR_VAL_U64s_MAX) tmp;
        struct open_buckets obs = { .nr = 0 };
        struct bch_devs_list devs_have = (struct bch_devs_list) { 0 };
        enum bch_watermark watermark = flags & BCH_WATERMARK_MASK;
        unsigned nr_reserve = watermark > BCH_WATERMARK_reclaim
                ? BTREE_NODE_RESERVE
                : 0;
        int ret;

        mutex_lock(&c->btree_reserve_cache_lock);
        if (c->btree_reserve_cache_nr > nr_reserve) {
                struct btree_alloc *a =
                        &c->btree_reserve_cache[--c->btree_reserve_cache_nr];

                obs = a->ob;
                bkey_copy(&tmp.k, &a->k);
                mutex_unlock(&c->btree_reserve_cache_lock);
                goto mem_alloc;
        }
        mutex_unlock(&c->btree_reserve_cache_lock);

retry:
        ret = bch2_alloc_sectors_start_trans(trans,
                                      c->opts.metadata_target ?:
                                      c->opts.foreground_target,
                                      0,
                                      writepoint_ptr(&c->btree_write_point),
                                      &devs_have,
                                      res->nr_replicas,
                                      min(res->nr_replicas,
                                          c->opts.metadata_replicas_required),
                                      watermark, 0, cl, &wp);
        if (unlikely(ret))
                return ERR_PTR(ret);

        if (wp->sectors_free < btree_sectors(c)) {
                struct open_bucket *ob;
                unsigned i;

                open_bucket_for_each(c, &wp->ptrs, ob, i)
                        if (ob->sectors_free < btree_sectors(c))
                                ob->sectors_free = 0;

                bch2_alloc_sectors_done(c, wp);
                goto retry;
        }

        bkey_btree_ptr_v2_init(&tmp.k);
        bch2_alloc_sectors_append_ptrs(c, wp, &tmp.k, btree_sectors(c), false);

        bch2_open_bucket_get(c, wp, &obs);
        bch2_alloc_sectors_done(c, wp);
mem_alloc:
        b = bch2_btree_node_mem_alloc(trans, interior_node);
        six_unlock_write(&b->c.lock);
        six_unlock_intent(&b->c.lock);

        /* we hold cannibalize_lock: */
        BUG_ON(IS_ERR(b));
        BUG_ON(b->ob.nr);

        bkey_copy(&b->key, &tmp.k);
        b->ob = obs;

        return b;
}

static struct btree *bch2_btree_node_alloc(struct btree_update *as,
                                           struct btree_trans *trans,
                                           unsigned level)
{
        struct bch_fs *c = as->c;
        struct btree *b;
        struct prealloc_nodes *p = &as->prealloc_nodes[!!level];
        int ret;

        BUG_ON(level >= BTREE_MAX_DEPTH);
        BUG_ON(!p->nr);

        b = p->b[--p->nr];

        btree_node_lock_nopath_nofail(trans, &b->c, SIX_LOCK_intent);
        btree_node_lock_nopath_nofail(trans, &b->c, SIX_LOCK_write);

        set_btree_node_accessed(b);
        set_btree_node_dirty_acct(c, b);
        set_btree_node_need_write(b);

        bch2_bset_init_first(b, &b->data->keys);
        b->c.level      = level;
        b->c.btree_id   = as->btree_id;
        b->version_ondisk = c->sb.version;

        memset(&b->nr, 0, sizeof(b->nr));
        b->data->magic = cpu_to_le64(bset_magic(c));
        memset(&b->data->_ptr, 0, sizeof(b->data->_ptr));
        b->data->flags = 0;
        SET_BTREE_NODE_ID(b->data, as->btree_id);
        SET_BTREE_NODE_LEVEL(b->data, level);

        if (b->key.k.type == KEY_TYPE_btree_ptr_v2) {
                struct bkey_i_btree_ptr_v2 *bp = bkey_i_to_btree_ptr_v2(&b->key);

                bp->v.mem_ptr           = 0;
                bp->v.seq               = b->data->keys.seq;
                bp->v.sectors_written   = 0;
        }

        SET_BTREE_NODE_NEW_EXTENT_OVERWRITE(b->data, true);

        bch2_btree_build_aux_trees(b);

        ret = bch2_btree_node_hash_insert(&c->btree_cache, b, level, as->btree_id);
        BUG_ON(ret);

        trace_and_count(c, btree_node_alloc, trans, b);
        bch2_increment_clock(c, btree_sectors(c), WRITE);
        return b;
}

static void btree_set_min(struct btree *b, struct bpos pos)
{
        if (b->key.k.type == KEY_TYPE_btree_ptr_v2)
                bkey_i_to_btree_ptr_v2(&b->key)->v.min_key = pos;
        b->data->min_key = pos;
}

static void btree_set_max(struct btree *b, struct bpos pos)
{
        b->key.k.p = pos;
        b->data->max_key = pos;
}

static struct btree *bch2_btree_node_alloc_replacement(struct btree_update *as,
                                                       struct btree_trans *trans,
                                                       struct btree *b)
{
        struct btree *n = bch2_btree_node_alloc(as, trans, b->c.level);
        struct bkey_format format = bch2_btree_calc_format(b);

        /*
         * The keys might expand with the new format - if they wouldn't fit in
         * the btree node anymore, use the old format for now:
         */
        if (!bch2_btree_node_format_fits(as->c, b, b->nr, &format))
                format = b->format;

        SET_BTREE_NODE_SEQ(n->data, BTREE_NODE_SEQ(b->data) + 1);

        btree_set_min(n, b->data->min_key);
        btree_set_max(n, b->data->max_key);

        n->data->format         = format;
        btree_node_set_format(n, format);

        bch2_btree_sort_into(as->c, n, b);

        btree_node_reset_sib_u64s(n);
        return n;
}

static struct btree *__btree_root_alloc(struct btree_update *as,
                                struct btree_trans *trans, unsigned level)
{
        struct btree *b = bch2_btree_node_alloc(as, trans, level);

        btree_set_min(b, POS_MIN);
        btree_set_max(b, SPOS_MAX);
        b->data->format = bch2_btree_calc_format(b);

        btree_node_set_format(b, b->data->format);
        bch2_btree_build_aux_trees(b);

        return b;
}

static void bch2_btree_reserve_put(struct btree_update *as, struct btree_trans *trans)
{
        struct bch_fs *c = as->c;
        struct prealloc_nodes *p;

        for (p = as->prealloc_nodes;
             p < as->prealloc_nodes + ARRAY_SIZE(as->prealloc_nodes);
             p++) {
                while (p->nr) {
                        struct btree *b = p->b[--p->nr];

                        mutex_lock(&c->btree_reserve_cache_lock);

                        if (c->btree_reserve_cache_nr <
                            ARRAY_SIZE(c->btree_reserve_cache)) {
                                struct btree_alloc *a =
                                        &c->btree_reserve_cache[c->btree_reserve_cache_nr++];

                                a->ob = b->ob;
                                b->ob.nr = 0;
                                bkey_copy(&a->k, &b->key);
                        } else {
                                bch2_open_buckets_put(c, &b->ob);
                        }

                        mutex_unlock(&c->btree_reserve_cache_lock);

                        btree_node_lock_nopath_nofail(trans, &b->c, SIX_LOCK_intent);
                        btree_node_lock_nopath_nofail(trans, &b->c, SIX_LOCK_write);
                        __btree_node_free(trans, b);
                        six_unlock_write(&b->c.lock);
                        six_unlock_intent(&b->c.lock);
                }
        }
}

static int bch2_btree_reserve_get(struct btree_trans *trans,
                                  struct btree_update *as,
                                  unsigned nr_nodes[2],
                                  unsigned flags,
                                  struct closure *cl)
{
        struct btree *b;
        unsigned interior;
        int ret = 0;

        BUG_ON(nr_nodes[0] + nr_nodes[1] > BTREE_RESERVE_MAX);

        /*
         * Protects reaping from the btree node cache and using the btree node
         * open bucket reserve:
         */
        ret = bch2_btree_cache_cannibalize_lock(trans, cl);
        if (ret)
                return ret;

        for (interior = 0; interior < 2; interior++) {
                struct prealloc_nodes *p = as->prealloc_nodes + interior;

                while (p->nr < nr_nodes[interior]) {
                        b = __bch2_btree_node_alloc(trans, &as->disk_res, cl,
                                                    interior, flags);
                        if (IS_ERR(b)) {
                                ret = PTR_ERR(b);
                                goto err;
                        }

                        p->b[p->nr++] = b;
                }
        }
err:
        bch2_btree_cache_cannibalize_unlock(trans);
        return ret;
}

/* Asynchronous interior node update machinery */

static void bch2_btree_update_free(struct btree_update *as, struct btree_trans *trans)
{
        struct bch_fs *c = as->c;

        if (as->took_gc_lock)
                up_read(&c->gc_lock);
        as->took_gc_lock = false;

        bch2_journal_pin_drop(&c->journal, &as->journal);
        bch2_journal_pin_flush(&c->journal, &as->journal);
        bch2_disk_reservation_put(c, &as->disk_res);
        bch2_btree_reserve_put(as, trans);

        time_stats_update(&c->times[BCH_TIME_btree_interior_update_total],
                               as->start_time);

        mutex_lock(&c->btree_interior_update_lock);
        list_del(&as->unwritten_list);
        list_del(&as->list);

        closure_debug_destroy(&as->cl);
        mempool_free(as, &c->btree_interior_update_pool);

        /*
         * Have to do the wakeup with btree_interior_update_lock still held,
         * since being on btree_interior_update_list is our ref on @c:
         */
        closure_wake_up(&c->btree_interior_update_wait);

        mutex_unlock(&c->btree_interior_update_lock);
}

static void btree_update_add_key(struct btree_update *as,
                                 struct keylist *keys, struct btree *b)
{
        struct bkey_i *k = &b->key;

        BUG_ON(bch2_keylist_u64s(keys) + k->k.u64s >
               ARRAY_SIZE(as->_old_keys));

        bkey_copy(keys->top, k);
        bkey_i_to_btree_ptr_v2(keys->top)->v.mem_ptr = b->c.level + 1;

        bch2_keylist_push(keys);
}

/*
 * The transactional part of an interior btree node update, where we journal the
 * update we did to the interior node and update alloc info:
 */
static int btree_update_nodes_written_trans(struct btree_trans *trans,
                                            struct btree_update *as)
{
        struct jset_entry *e = bch2_trans_jset_entry_alloc(trans, as->journal_u64s);
        int ret = PTR_ERR_OR_ZERO(e);
        if (ret)
                return ret;

        memcpy(e, as->journal_entries, as->journal_u64s * sizeof(u64));

        trans->journal_pin = &as->journal;

        for_each_keylist_key(&as->old_keys, k) {
                unsigned level = bkey_i_to_btree_ptr_v2(k)->v.mem_ptr;

                ret = bch2_key_trigger_old(trans, as->btree_id, level, bkey_i_to_s_c(k),
                                           BTREE_TRIGGER_TRANSACTIONAL);
                if (ret)
                        return ret;
        }

        for_each_keylist_key(&as->new_keys, k) {
                unsigned level = bkey_i_to_btree_ptr_v2(k)->v.mem_ptr;

                ret = bch2_key_trigger_new(trans, as->btree_id, level, bkey_i_to_s(k),
                                           BTREE_TRIGGER_TRANSACTIONAL);
                if (ret)
                        return ret;
        }

        return 0;
}

static void btree_update_nodes_written(struct btree_update *as)
{
        struct bch_fs *c = as->c;
        struct btree *b;
        struct btree_trans *trans = bch2_trans_get(c);
        u64 journal_seq = 0;
        unsigned i;
        int ret;

        /*
         * If we're already in an error state, it might be because a btree node
         * was never written, and we might be trying to free that same btree
         * node here, but it won't have been marked as allocated and we'll see
         * spurious disk usage inconsistencies in the transactional part below
         * if we don't skip it:
         */
        ret = bch2_journal_error(&c->journal);
        if (ret)
                goto err;

        /*
         * Wait for any in flight writes to finish before we free the old nodes
         * on disk:
         */
        for (i = 0; i < as->nr_old_nodes; i++) {
                __le64 seq;

                b = as->old_nodes[i];

                btree_node_lock_nopath_nofail(trans, &b->c, SIX_LOCK_read);
                seq = b->data ? b->data->keys.seq : 0;
                six_unlock_read(&b->c.lock);

                if (seq == as->old_nodes_seq[i])
                        wait_on_bit_io(&b->flags, BTREE_NODE_write_in_flight_inner,
                                       TASK_UNINTERRUPTIBLE);
        }

        /*
         * We did an update to a parent node where the pointers we added pointed
         * to child nodes that weren't written yet: now, the child nodes have
         * been written so we can write out the update to the interior node.
         */

        /*
         * We can't call into journal reclaim here: we'd block on the journal
         * reclaim lock, but we may need to release the open buckets we have
         * pinned in order for other btree updates to make forward progress, and
         * journal reclaim does btree updates when flushing bkey_cached entries,
         * which may require allocations as well.
         */
        ret = commit_do(trans, &as->disk_res, &journal_seq,
                        BCH_WATERMARK_reclaim|
                        BCH_TRANS_COMMIT_no_enospc|
                        BCH_TRANS_COMMIT_no_check_rw|
                        BCH_TRANS_COMMIT_journal_reclaim,
                        btree_update_nodes_written_trans(trans, as));
        bch2_trans_unlock(trans);

        bch2_fs_fatal_err_on(ret && !bch2_journal_error(&c->journal), c,
                             "%s(): error %s", __func__, bch2_err_str(ret));
err:
        if (as->b) {

                b = as->b;
                btree_path_idx_t path_idx = get_unlocked_mut_path(trans,
                                                as->btree_id, b->c.level, b->key.k.p);
                struct btree_path *path = trans->paths + path_idx;
                /*
                 * @b is the node we did the final insert into:
                 *
                 * On failure to get a journal reservation, we still have to
                 * unblock the write and allow most of the write path to happen
                 * so that shutdown works, but the i->journal_seq mechanism
                 * won't work to prevent the btree write from being visible (we
                 * didn't get a journal sequence number) - instead
                 * __bch2_btree_node_write() doesn't do the actual write if
                 * we're in journal error state:
                 */

                /*
                 * Ensure transaction is unlocked before using
                 * btree_node_lock_nopath() (the use of which is always suspect,
                 * we need to work on removing this in the future)
                 *
                 * It should be, but get_unlocked_mut_path() -> bch2_path_get()
                 * calls bch2_path_upgrade(), before we call path_make_mut(), so
                 * we may rarely end up with a locked path besides the one we
                 * have here:
                 */
                bch2_trans_unlock(trans);
                btree_node_lock_nopath_nofail(trans, &b->c, SIX_LOCK_intent);
                mark_btree_node_locked(trans, path, b->c.level, BTREE_NODE_INTENT_LOCKED);
                path->l[b->c.level].lock_seq = six_lock_seq(&b->c.lock);
                path->l[b->c.level].b = b;

                bch2_btree_node_lock_write_nofail(trans, path, &b->c);

                mutex_lock(&c->btree_interior_update_lock);

                list_del(&as->write_blocked_list);
                if (list_empty(&b->write_blocked))
                        clear_btree_node_write_blocked(b);

                /*
                 * Node might have been freed, recheck under
                 * btree_interior_update_lock:
                 */
                if (as->b == b) {
                        BUG_ON(!b->c.level);
                        BUG_ON(!btree_node_dirty(b));

                        if (!ret) {
                                struct bset *last = btree_bset_last(b);

                                last->journal_seq = cpu_to_le64(
                                                             max(journal_seq,
                                                                 le64_to_cpu(last->journal_seq)));

                                bch2_btree_add_journal_pin(c, b, journal_seq);
                        } else {
                                /*
                                 * If we didn't get a journal sequence number we
                                 * can't write this btree node, because recovery
                                 * won't know to ignore this write:
                                 */
                                set_btree_node_never_write(b);
                        }
                }

                mutex_unlock(&c->btree_interior_update_lock);

                mark_btree_node_locked_noreset(path, b->c.level, BTREE_NODE_INTENT_LOCKED);
                six_unlock_write(&b->c.lock);

                btree_node_write_if_need(c, b, SIX_LOCK_intent);
                btree_node_unlock(trans, path, b->c.level);
                bch2_path_put(trans, path_idx, true);
        }

        bch2_journal_pin_drop(&c->journal, &as->journal);

        mutex_lock(&c->btree_interior_update_lock);
        for (i = 0; i < as->nr_new_nodes; i++) {
                b = as->new_nodes[i];

                BUG_ON(b->will_make_reachable != (unsigned long) as);
                b->will_make_reachable = 0;
                clear_btree_node_will_make_reachable(b);
        }
        mutex_unlock(&c->btree_interior_update_lock);

        for (i = 0; i < as->nr_new_nodes; i++) {
                b = as->new_nodes[i];

                btree_node_lock_nopath_nofail(trans, &b->c, SIX_LOCK_read);
                btree_node_write_if_need(c, b, SIX_LOCK_read);
                six_unlock_read(&b->c.lock);
        }

        for (i = 0; i < as->nr_open_buckets; i++)
                bch2_open_bucket_put(c, c->open_buckets + as->open_buckets[i]);

        bch2_btree_update_free(as, trans);
        bch2_trans_put(trans);
}

static void btree_interior_update_work(struct work_struct *work)
{
        struct bch_fs *c =
                container_of(work, struct bch_fs, btree_interior_update_work);
        struct btree_update *as;

        while (1) {
                mutex_lock(&c->btree_interior_update_lock);
                as = list_first_entry_or_null(&c->btree_interior_updates_unwritten,
                                              struct btree_update, unwritten_list);
                if (as && !as->nodes_written)
                        as = NULL;
                mutex_unlock(&c->btree_interior_update_lock);

                if (!as)
                        break;

                btree_update_nodes_written(as);
        }
}

static CLOSURE_CALLBACK(btree_update_set_nodes_written)
{
        closure_type(as, struct btree_update, cl);
        struct bch_fs *c = as->c;

        mutex_lock(&c->btree_interior_update_lock);
        as->nodes_written = true;
        mutex_unlock(&c->btree_interior_update_lock);

        queue_work(c->btree_interior_update_worker, &c->btree_interior_update_work);
}

/*
 * We're updating @b with pointers to nodes that haven't finished writing yet:
 * block @b from being written until @as completes
 */
static void btree_update_updated_node(struct btree_update *as, struct btree *b)
{
        struct bch_fs *c = as->c;

        mutex_lock(&c->btree_interior_update_lock);
        list_add_tail(&as->unwritten_list, &c->btree_interior_updates_unwritten);

        BUG_ON(as->mode != BTREE_INTERIOR_NO_UPDATE);
        BUG_ON(!btree_node_dirty(b));
        BUG_ON(!b->c.level);

        as->mode        = BTREE_INTERIOR_UPDATING_NODE;
        as->b           = b;

        set_btree_node_write_blocked(b);
        list_add(&as->write_blocked_list, &b->write_blocked);

        mutex_unlock(&c->btree_interior_update_lock);
}

static int bch2_update_reparent_journal_pin_flush(struct journal *j,
                                struct journal_entry_pin *_pin, u64 seq)
{
        return 0;
}

static void btree_update_reparent(struct btree_update *as,
                                  struct btree_update *child)
{
        struct bch_fs *c = as->c;

        lockdep_assert_held(&c->btree_interior_update_lock);

        child->b = NULL;
        child->mode = BTREE_INTERIOR_UPDATING_AS;

        bch2_journal_pin_copy(&c->journal, &as->journal, &child->journal,
                              bch2_update_reparent_journal_pin_flush);
}

static void btree_update_updated_root(struct btree_update *as, struct btree *b)
{
        struct bkey_i *insert = &b->key;
        struct bch_fs *c = as->c;

        BUG_ON(as->mode != BTREE_INTERIOR_NO_UPDATE);

        BUG_ON(as->journal_u64s + jset_u64s(insert->k.u64s) >
               ARRAY_SIZE(as->journal_entries));

        as->journal_u64s +=
                journal_entry_set((void *) &as->journal_entries[as->journal_u64s],
                                  BCH_JSET_ENTRY_btree_root,
                                  b->c.btree_id, b->c.level,
                                  insert, insert->k.u64s);

        mutex_lock(&c->btree_interior_update_lock);
        list_add_tail(&as->unwritten_list, &c->btree_interior_updates_unwritten);

        as->mode        = BTREE_INTERIOR_UPDATING_ROOT;
        mutex_unlock(&c->btree_interior_update_lock);
}

/*
 * bch2_btree_update_add_new_node:
 *
 * This causes @as to wait on @b to be written, before it gets to
 * bch2_btree_update_nodes_written
 *
 * Additionally, it sets b->will_make_reachable to prevent any additional writes
 * to @b from happening besides the first until @b is reachable on disk
 *
 * And it adds @b to the list of @as's new nodes, so that we can update sector
 * counts in bch2_btree_update_nodes_written:
 */
static void bch2_btree_update_add_new_node(struct btree_update *as, struct btree *b)
{
        struct bch_fs *c = as->c;

        closure_get(&as->cl);

        mutex_lock(&c->btree_interior_update_lock);
        BUG_ON(as->nr_new_nodes >= ARRAY_SIZE(as->new_nodes));
        BUG_ON(b->will_make_reachable);

        as->new_nodes[as->nr_new_nodes++] = b;
        b->will_make_reachable = 1UL|(unsigned long) as;
        set_btree_node_will_make_reachable(b);

        mutex_unlock(&c->btree_interior_update_lock);

        btree_update_add_key(as, &as->new_keys, b);

        if (b->key.k.type == KEY_TYPE_btree_ptr_v2) {
                unsigned bytes = vstruct_end(&b->data->keys) - (void *) b->data;
                unsigned sectors = round_up(bytes, block_bytes(c)) >> 9;

                bkey_i_to_btree_ptr_v2(&b->key)->v.sectors_written =
                        cpu_to_le16(sectors);
        }
}

/*
 * returns true if @b was a new node
 */
static void btree_update_drop_new_node(struct bch_fs *c, struct btree *b)
{
        struct btree_update *as;
        unsigned long v;
        unsigned i;

        mutex_lock(&c->btree_interior_update_lock);
        /*
         * When b->will_make_reachable != 0, it owns a ref on as->cl that's
         * dropped when it gets written by bch2_btree_complete_write - the
         * xchg() is for synchronization with bch2_btree_complete_write:
         */
        v = xchg(&b->will_make_reachable, 0);
        clear_btree_node_will_make_reachable(b);
        as = (struct btree_update *) (v & ~1UL);

        if (!as) {
                mutex_unlock(&c->btree_interior_update_lock);
                return;
        }

        for (i = 0; i < as->nr_new_nodes; i++)
                if (as->new_nodes[i] == b)
                        goto found;

        BUG();
found:
        array_remove_item(as->new_nodes, as->nr_new_nodes, i);
        mutex_unlock(&c->btree_interior_update_lock);

        if (v & 1)
                closure_put(&as->cl);
}

static void bch2_btree_update_get_open_buckets(struct btree_update *as, struct btree *b)
{
        while (b->ob.nr)
                as->open_buckets[as->nr_open_buckets++] =
                        b->ob.v[--b->ob.nr];
}

static int bch2_btree_update_will_free_node_journal_pin_flush(struct journal *j,
                                struct journal_entry_pin *_pin, u64 seq)
{
        return 0;
}

/*
 * @b is being split/rewritten: it may have pointers to not-yet-written btree
 * nodes and thus outstanding btree_updates - redirect @b's
 * btree_updates to point to this btree_update:
 */
static void bch2_btree_interior_update_will_free_node(struct btree_update *as,
                                                      struct btree *b)
{
        struct bch_fs *c = as->c;
        struct btree_update *p, *n;
        struct btree_write *w;

        set_btree_node_dying(b);

        if (btree_node_fake(b))
                return;

        mutex_lock(&c->btree_interior_update_lock);

        /*
         * Does this node have any btree_update operations preventing
         * it from being written?
         *
         * If so, redirect them to point to this btree_update: we can
         * write out our new nodes, but we won't make them visible until those
         * operations complete
         */
        list_for_each_entry_safe(p, n, &b->write_blocked, write_blocked_list) {
                list_del_init(&p->write_blocked_list);
                btree_update_reparent(as, p);

                /*
                 * for flush_held_btree_writes() waiting on updates to flush or
                 * nodes to be writeable:
                 */
                closure_wake_up(&c->btree_interior_update_wait);
        }

        clear_btree_node_dirty_acct(c, b);
        clear_btree_node_need_write(b);
        clear_btree_node_write_blocked(b);

        /*
         * Does this node have unwritten data that has a pin on the journal?
         *
         * If so, transfer that pin to the btree_update operation -
         * note that if we're freeing multiple nodes, we only need to keep the
         * oldest pin of any of the nodes we're freeing. We'll release the pin
         * when the new nodes are persistent and reachable on disk:
         */
        w = btree_current_write(b);
        bch2_journal_pin_copy(&c->journal, &as->journal, &w->journal,
                              bch2_btree_update_will_free_node_journal_pin_flush);
        bch2_journal_pin_drop(&c->journal, &w->journal);

        w = btree_prev_write(b);
        bch2_journal_pin_copy(&c->journal, &as->journal, &w->journal,
                              bch2_btree_update_will_free_node_journal_pin_flush);
        bch2_journal_pin_drop(&c->journal, &w->journal);

        mutex_unlock(&c->btree_interior_update_lock);

        /*
         * Is this a node that isn't reachable on disk yet?
         *
         * Nodes that aren't reachable yet have writes blocked until they're
         * reachable - now that we've cancelled any pending writes and moved
         * things waiting on that write to wait on this update, we can drop this
         * node from the list of nodes that the other update is making
         * reachable, prior to freeing it:
         */
        btree_update_drop_new_node(c, b);

        btree_update_add_key(as, &as->old_keys, b);

        as->old_nodes[as->nr_old_nodes] = b;
        as->old_nodes_seq[as->nr_old_nodes] = b->data->keys.seq;
        as->nr_old_nodes++;
}

static void bch2_btree_update_done(struct btree_update *as, struct btree_trans *trans)
{
        struct bch_fs *c = as->c;
        u64 start_time = as->start_time;

        BUG_ON(as->mode == BTREE_INTERIOR_NO_UPDATE);

        if (as->took_gc_lock)
                up_read(&as->c->gc_lock);
        as->took_gc_lock = false;

        bch2_btree_reserve_put(as, trans);

        continue_at(&as->cl, btree_update_set_nodes_written,
                    as->c->btree_interior_update_worker);

        time_stats_update(&c->times[BCH_TIME_btree_interior_update_foreground],
                               start_time);
}

static struct btree_update *
bch2_btree_update_start(struct btree_trans *trans, struct btree_path *path,
                        unsigned level, bool split, unsigned flags)
{
        struct bch_fs *c = trans->c;
        struct btree_update *as;
        u64 start_time = local_clock();
        int disk_res_flags = (flags & BCH_TRANS_COMMIT_no_enospc)
                ? BCH_DISK_RESERVATION_NOFAIL : 0;
        unsigned nr_nodes[2] = { 0, 0 };
        unsigned update_level = level;
        enum bch_watermark watermark = flags & BCH_WATERMARK_MASK;
        int ret = 0;
        u32 restart_count = trans->restart_count;

        BUG_ON(!path->should_be_locked);

        if (watermark == BCH_WATERMARK_copygc)
                watermark = BCH_WATERMARK_btree_copygc;
        if (watermark < BCH_WATERMARK_btree)
                watermark = BCH_WATERMARK_btree;

        flags &= ~BCH_WATERMARK_MASK;
        flags |= watermark;

        if (!(flags & BCH_TRANS_COMMIT_journal_reclaim) &&
            watermark < c->journal.watermark) {
                struct journal_res res = { 0 };

                ret = drop_locks_do(trans,
                        bch2_journal_res_get(&c->journal, &res, 1,
                                             watermark|JOURNAL_RES_GET_CHECK));
                if (ret)
                        return ERR_PTR(ret);
        }

        while (1) {
                nr_nodes[!!update_level] += 1 + split;
                update_level++;

                ret = bch2_btree_path_upgrade(trans, path, update_level + 1);
                if (ret)
                        return ERR_PTR(ret);

                if (!btree_path_node(path, update_level)) {
                        /* Allocating new root? */
                        nr_nodes[1] += split;
                        update_level = BTREE_MAX_DEPTH;
                        break;
                }

                /*
                 * Always check for space for two keys, even if we won't have to
                 * split at prior level - it might have been a merge instead:
                 */
                if (bch2_btree_node_insert_fits(path->l[update_level].b,
                                                BKEY_BTREE_PTR_U64s_MAX * 2))
                        break;

                split = path->l[update_level].b->nr.live_u64s > BTREE_SPLIT_THRESHOLD(c);
        }

        if (!down_read_trylock(&c->gc_lock)) {
                ret = drop_locks_do(trans, (down_read(&c->gc_lock), 0));
                if (ret) {
                        up_read(&c->gc_lock);
                        return ERR_PTR(ret);
                }
        }

        as = mempool_alloc(&c->btree_interior_update_pool, GFP_NOFS);
        memset(as, 0, sizeof(*as));
        closure_init(&as->cl, NULL);
        as->c           = c;
        as->start_time  = start_time;
        as->mode        = BTREE_INTERIOR_NO_UPDATE;
        as->took_gc_lock = true;
        as->btree_id    = path->btree_id;
        as->update_level = update_level;
        INIT_LIST_HEAD(&as->list);
        INIT_LIST_HEAD(&as->unwritten_list);
        INIT_LIST_HEAD(&as->write_blocked_list);
        bch2_keylist_init(&as->old_keys, as->_old_keys);
        bch2_keylist_init(&as->new_keys, as->_new_keys);
        bch2_keylist_init(&as->parent_keys, as->inline_keys);

        mutex_lock(&c->btree_interior_update_lock);
        list_add_tail(&as->list, &c->btree_interior_update_list);
        mutex_unlock(&c->btree_interior_update_lock);

        /*
         * We don't want to allocate if we're in an error state, that can cause
         * deadlock on emergency shutdown due to open buckets getting stuck in
         * the btree_reserve_cache after allocator shutdown has cleared it out.
         * This check needs to come after adding us to the btree_interior_update
         * list but before calling bch2_btree_reserve_get, to synchronize with
         * __bch2_fs_read_only().
         */
        ret = bch2_journal_error(&c->journal);
        if (ret)
                goto err;

        ret = bch2_disk_reservation_get(c, &as->disk_res,
                        (nr_nodes[0] + nr_nodes[1]) * btree_sectors(c),
                        c->opts.metadata_replicas,
                        disk_res_flags);
        if (ret)
                goto err;

        ret = bch2_btree_reserve_get(trans, as, nr_nodes, flags, NULL);
        if (bch2_err_matches(ret, ENOSPC) ||
            bch2_err_matches(ret, ENOMEM)) {
                struct closure cl;

                /*
                 * XXX: this should probably be a separate BTREE_INSERT_NONBLOCK
                 * flag
                 */
                if (bch2_err_matches(ret, ENOSPC) &&
                    (flags & BCH_TRANS_COMMIT_journal_reclaim) &&
                    watermark != BCH_WATERMARK_reclaim) {
                        ret = -BCH_ERR_journal_reclaim_would_deadlock;
                        goto err;
                }

                closure_init_stack(&cl);

                do {
                        ret = bch2_btree_reserve_get(trans, as, nr_nodes, flags, &cl);

                        bch2_trans_unlock(trans);
                        closure_sync(&cl);
                } while (bch2_err_matches(ret, BCH_ERR_operation_blocked));
        }

        if (ret) {
                trace_and_count(c, btree_reserve_get_fail, trans->fn,
                                _RET_IP_, nr_nodes[0] + nr_nodes[1], ret);
                goto err;
        }

        ret = bch2_trans_relock(trans);
        if (ret)
                goto err;

        bch2_trans_verify_not_restarted(trans, restart_count);
        return as;
err:
        bch2_btree_update_free(as, trans);
        if (!bch2_err_matches(ret, ENOSPC) &&
            !bch2_err_matches(ret, EROFS))
                bch_err_fn_ratelimited(c, ret);
        return ERR_PTR(ret);
}

/* Btree root updates: */

static void bch2_btree_set_root_inmem(struct bch_fs *c, struct btree *b)
{
        /* Root nodes cannot be reaped */
        mutex_lock(&c->btree_cache.lock);
        list_del_init(&b->list);
        mutex_unlock(&c->btree_cache.lock);

        mutex_lock(&c->btree_root_lock);
        BUG_ON(btree_node_root(c, b) &&
               (b->c.level < btree_node_root(c, b)->c.level ||
                !btree_node_dying(btree_node_root(c, b))));

        bch2_btree_id_root(c, b->c.btree_id)->b = b;
        mutex_unlock(&c->btree_root_lock);

        bch2_recalc_btree_reserve(c);
}

static void bch2_btree_set_root(struct btree_update *as,
                                struct btree_trans *trans,
                                struct btree_path *path,
                                struct btree *b)
{
        struct bch_fs *c = as->c;
        struct btree *old;

        trace_and_count(c, btree_node_set_root, trans, b);

        old = btree_node_root(c, b);

        /*
         * Ensure no one is using the old root while we switch to the
         * new root:
         */
        bch2_btree_node_lock_write_nofail(trans, path, &old->c);

        bch2_btree_set_root_inmem(c, b);

        btree_update_updated_root(as, b);

        /*
         * Unlock old root after new root is visible:
         *
         * The new root isn't persistent, but that's ok: we still have
         * an intent lock on the new root, and any updates that would
         * depend on the new root would have to update the new root.
         */
        bch2_btree_node_unlock_write(trans, path, old);
}

/* Interior node updates: */

static void bch2_insert_fixup_btree_ptr(struct btree_update *as,
                                        struct btree_trans *trans,
                                        struct btree_path *path,
                                        struct btree *b,
                                        struct btree_node_iter *node_iter,
                                        struct bkey_i *insert)
{
        struct bch_fs *c = as->c;
        struct bkey_packed *k;
        struct printbuf buf = PRINTBUF;
        unsigned long old, new, v;

        BUG_ON(insert->k.type == KEY_TYPE_btree_ptr_v2 &&
               !btree_ptr_sectors_written(insert));

        if (unlikely(!test_bit(JOURNAL_REPLAY_DONE, &c->journal.flags)))
                bch2_journal_key_overwritten(c, b->c.btree_id, b->c.level, insert->k.p);

        if (bch2_bkey_invalid(c, bkey_i_to_s_c(insert),
                              btree_node_type(b), WRITE, &buf) ?:
            bch2_bkey_in_btree_node(c, b, bkey_i_to_s_c(insert), &buf)) {
                printbuf_reset(&buf);
                prt_printf(&buf, "inserting invalid bkey\n  ");
                bch2_bkey_val_to_text(&buf, c, bkey_i_to_s_c(insert));
                prt_printf(&buf, "\n  ");
                bch2_bkey_invalid(c, bkey_i_to_s_c(insert),
                                  btree_node_type(b), WRITE, &buf);
                bch2_bkey_in_btree_node(c, b, bkey_i_to_s_c(insert), &buf);

                bch2_fs_inconsistent(c, "%s", buf.buf);
                dump_stack();
        }

        BUG_ON(as->journal_u64s + jset_u64s(insert->k.u64s) >
               ARRAY_SIZE(as->journal_entries));

        as->journal_u64s +=
                journal_entry_set((void *) &as->journal_entries[as->journal_u64s],
                                  BCH_JSET_ENTRY_btree_keys,
                                  b->c.btree_id, b->c.level,
                                  insert, insert->k.u64s);

        while ((k = bch2_btree_node_iter_peek_all(node_iter, b)) &&
               bkey_iter_pos_cmp(b, k, &insert->k.p) < 0)
                bch2_btree_node_iter_advance(node_iter, b);

        bch2_btree_bset_insert_key(trans, path, b, node_iter, insert);
        set_btree_node_dirty_acct(c, b);

        v = READ_ONCE(b->flags);
        do {
                old = new = v;

                new &= ~BTREE_WRITE_TYPE_MASK;
                new |= BTREE_WRITE_interior;
                new |= 1 << BTREE_NODE_need_write;
        } while ((v = cmpxchg(&b->flags, old, new)) != old);

        printbuf_exit(&buf);
}

static void
__bch2_btree_insert_keys_interior(struct btree_update *as,
                                  struct btree_trans *trans,
                                  struct btree_path *path,
                                  struct btree *b,
                                  struct btree_node_iter node_iter,
                                  struct keylist *keys)
{
        struct bkey_i *insert = bch2_keylist_front(keys);
        struct bkey_packed *k;

        BUG_ON(btree_node_type(b) != BKEY_TYPE_btree);

        while ((k = bch2_btree_node_iter_prev_all(&node_iter, b)) &&
               (bkey_cmp_left_packed(b, k, &insert->k.p) >= 0))
                ;

        while (!bch2_keylist_empty(keys)) {
                insert = bch2_keylist_front(keys);

                if (bpos_gt(insert->k.p, b->key.k.p))
                        break;

                bch2_insert_fixup_btree_ptr(as, trans, path, b, &node_iter, insert);
                bch2_keylist_pop_front(keys);
        }
}

/*
 * Move keys from n1 (original replacement node, now lower node) to n2 (higher
 * node)
 */
static void __btree_split_node(struct btree_update *as,
                               struct btree_trans *trans,
                               struct btree *b,
                               struct btree *n[2])
{
        struct bkey_packed *k;
        struct bpos n1_pos = POS_MIN;
        struct btree_node_iter iter;
        struct bset *bsets[2];
        struct bkey_format_state format[2];
        struct bkey_packed *out[2];
        struct bkey uk;
        unsigned u64s, n1_u64s = (b->nr.live_u64s * 3) / 5;
        struct { unsigned nr_keys, val_u64s; } nr_keys[2];
        int i;

        memset(&nr_keys, 0, sizeof(nr_keys));

        for (i = 0; i < 2; i++) {
                BUG_ON(n[i]->nsets != 1);

                bsets[i] = btree_bset_first(n[i]);
                out[i] = bsets[i]->start;

                SET_BTREE_NODE_SEQ(n[i]->data, BTREE_NODE_SEQ(b->data) + 1);
                bch2_bkey_format_init(&format[i]);
        }

        u64s = 0;
        for_each_btree_node_key(b, k, &iter) {
                if (bkey_deleted(k))
                        continue;

                i = u64s >= n1_u64s;
                u64s += k->u64s;
                uk = bkey_unpack_key(b, k);
                if (!i)
                        n1_pos = uk.p;
                bch2_bkey_format_add_key(&format[i], &uk);

                nr_keys[i].nr_keys++;
                nr_keys[i].val_u64s += bkeyp_val_u64s(&b->format, k);
        }

        btree_set_min(n[0], b->data->min_key);
        btree_set_max(n[0], n1_pos);
        btree_set_min(n[1], bpos_successor(n1_pos));
        btree_set_max(n[1], b->data->max_key);

        for (i = 0; i < 2; i++) {
                bch2_bkey_format_add_pos(&format[i], n[i]->data->min_key);
                bch2_bkey_format_add_pos(&format[i], n[i]->data->max_key);

                n[i]->data->format = bch2_bkey_format_done(&format[i]);

                unsigned u64s = nr_keys[i].nr_keys * n[i]->data->format.key_u64s +
                        nr_keys[i].val_u64s;
                if (__vstruct_bytes(struct btree_node, u64s) > btree_buf_bytes(b))
                        n[i]->data->format = b->format;

                btree_node_set_format(n[i], n[i]->data->format);
        }

        u64s = 0;
        for_each_btree_node_key(b, k, &iter) {
                if (bkey_deleted(k))
                        continue;

                i = u64s >= n1_u64s;
                u64s += k->u64s;

                if (bch2_bkey_transform(&n[i]->format, out[i], bkey_packed(k)
                                        ? &b->format: &bch2_bkey_format_current, k))
                        out[i]->format = KEY_FORMAT_LOCAL_BTREE;
                else
                        bch2_bkey_unpack(b, (void *) out[i], k);

                out[i]->needs_whiteout = false;

                btree_keys_account_key_add(&n[i]->nr, 0, out[i]);
                out[i] = bkey_p_next(out[i]);
        }

        for (i = 0; i < 2; i++) {
                bsets[i]->u64s = cpu_to_le16((u64 *) out[i] - bsets[i]->_data);

                BUG_ON(!bsets[i]->u64s);

                set_btree_bset_end(n[i], n[i]->set);

                btree_node_reset_sib_u64s(n[i]);

                bch2_verify_btree_nr_keys(n[i]);

                if (b->c.level)
                        btree_node_interior_verify(as->c, n[i]);
        }
}

/*
 * For updates to interior nodes, we've got to do the insert before we split
 * because the stuff we're inserting has to be inserted atomically. Post split,
 * the keys might have to go in different nodes and the split would no longer be
 * atomic.
 *
 * Worse, if the insert is from btree node coalescing, if we do the insert after
 * we do the split (and pick the pivot) - the pivot we pick might be between
 * nodes that were coalesced, and thus in the middle of a child node post
 * coalescing:
 */
static void btree_split_insert_keys(struct btree_update *as,
                                    struct btree_trans *trans,
                                    btree_path_idx_t path_idx,
                                    struct btree *b,
                                    struct keylist *keys)
{
        struct btree_path *path = trans->paths + path_idx;

        if (!bch2_keylist_empty(keys) &&
            bpos_le(bch2_keylist_front(keys)->k.p, b->data->max_key)) {
                struct btree_node_iter node_iter;

                bch2_btree_node_iter_init(&node_iter, b, &bch2_keylist_front(keys)->k.p);

                __bch2_btree_insert_keys_interior(as, trans, path, b, node_iter, keys);

                btree_node_interior_verify(as->c, b);
        }
}

static int btree_split(struct btree_update *as, struct btree_trans *trans,
                       btree_path_idx_t path, struct btree *b,
                       struct keylist *keys, unsigned flags)
{
        struct bch_fs *c = as->c;
        struct btree *parent = btree_node_parent(trans->paths + path, b);
        struct btree *n1, *n2 = NULL, *n3 = NULL;
        btree_path_idx_t path1 = 0, path2 = 0;
        u64 start_time = local_clock();
        int ret = 0;

        BUG_ON(!parent && (b != btree_node_root(c, b)));
        BUG_ON(parent && !btree_node_intent_locked(trans->paths + path, b->c.level + 1));

        bch2_btree_interior_update_will_free_node(as, b);

        if (b->nr.live_u64s > BTREE_SPLIT_THRESHOLD(c)) {
                struct btree *n[2];

                trace_and_count(c, btree_node_split, trans, b);

                n[0] = n1 = bch2_btree_node_alloc(as, trans, b->c.level);
                n[1] = n2 = bch2_btree_node_alloc(as, trans, b->c.level);

                __btree_split_node(as, trans, b, n);

                if (keys) {
                        btree_split_insert_keys(as, trans, path, n1, keys);
                        btree_split_insert_keys(as, trans, path, n2, keys);
                        BUG_ON(!bch2_keylist_empty(keys));
                }

                bch2_btree_build_aux_trees(n2);
                bch2_btree_build_aux_trees(n1);

                bch2_btree_update_add_new_node(as, n1);
                bch2_btree_update_add_new_node(as, n2);
                six_unlock_write(&n2->c.lock);
                six_unlock_write(&n1->c.lock);

                path1 = get_unlocked_mut_path(trans, as->btree_id, n1->c.level, n1->key.k.p);
                six_lock_increment(&n1->c.lock, SIX_LOCK_intent);
                mark_btree_node_locked(trans, trans->paths + path1, n1->c.level, BTREE_NODE_INTENT_LOCKED);
                bch2_btree_path_level_init(trans, trans->paths + path1, n1);

                path2 = get_unlocked_mut_path(trans, as->btree_id, n2->c.level, n2->key.k.p);
                six_lock_increment(&n2->c.lock, SIX_LOCK_intent);
                mark_btree_node_locked(trans, trans->paths + path2, n2->c.level, BTREE_NODE_INTENT_LOCKED);
                bch2_btree_path_level_init(trans, trans->paths + path2, n2);

                /*
                 * Note that on recursive parent_keys == keys, so we
                 * can't start adding new keys to parent_keys before emptying it
                 * out (which we did with btree_split_insert_keys() above)
                 */
                bch2_keylist_add(&as->parent_keys, &n1->key);
                bch2_keylist_add(&as->parent_keys, &n2->key);

                if (!parent) {
                        /* Depth increases, make a new root */
                        n3 = __btree_root_alloc(as, trans, b->c.level + 1);

                        bch2_btree_update_add_new_node(as, n3);
                        six_unlock_write(&n3->c.lock);

                        trans->paths[path2].locks_want++;
                        BUG_ON(btree_node_locked(trans->paths + path2, n3->c.level));
                        six_lock_increment(&n3->c.lock, SIX_LOCK_intent);
                        mark_btree_node_locked(trans, trans->paths + path2, n3->c.level, BTREE_NODE_INTENT_LOCKED);
                        bch2_btree_path_level_init(trans, trans->paths + path2, n3);

                        n3->sib_u64s[0] = U16_MAX;
                        n3->sib_u64s[1] = U16_MAX;

                        btree_split_insert_keys(as, trans, path, n3, &as->parent_keys);
                }
        } else {
                trace_and_count(c, btree_node_compact, trans, b);

                n1 = bch2_btree_node_alloc_replacement(as, trans, b);

                if (keys) {
                        btree_split_insert_keys(as, trans, path, n1, keys);
                        BUG_ON(!bch2_keylist_empty(keys));
                }

                bch2_btree_build_aux_trees(n1);
                bch2_btree_update_add_new_node(as, n1);
                six_unlock_write(&n1->c.lock);

                path1 = get_unlocked_mut_path(trans, as->btree_id, n1->c.level, n1->key.k.p);
                six_lock_increment(&n1->c.lock, SIX_LOCK_intent);
                mark_btree_node_locked(trans, trans->paths + path1, n1->c.level, BTREE_NODE_INTENT_LOCKED);
                bch2_btree_path_level_init(trans, trans->paths + path1, n1);

                if (parent)
                        bch2_keylist_add(&as->parent_keys, &n1->key);
        }

        /* New nodes all written, now make them visible: */

        if (parent) {
                /* Split a non root node */
                ret = bch2_btree_insert_node(as, trans, path, parent, &as->parent_keys, flags);
                if (ret)
                        goto err;
        } else if (n3) {
                bch2_btree_set_root(as, trans, trans->paths + path, n3);
        } else {
                /* Root filled up but didn't need to be split */
                bch2_btree_set_root(as, trans, trans->paths + path, n1);
        }

        if (n3) {
                bch2_btree_update_get_open_buckets(as, n3);
                bch2_btree_node_write(c, n3, SIX_LOCK_intent, 0);
        }
        if (n2) {
                bch2_btree_update_get_open_buckets(as, n2);
                bch2_btree_node_write(c, n2, SIX_LOCK_intent, 0);
        }
        bch2_btree_update_get_open_buckets(as, n1);
        bch2_btree_node_write(c, n1, SIX_LOCK_intent, 0);

        /*
         * The old node must be freed (in memory) _before_ unlocking the new
         * nodes - else another thread could re-acquire a read lock on the old
         * node after another thread has locked and updated the new node, thus
         * seeing stale data:
         */
        bch2_btree_node_free_inmem(trans, trans->paths + path, b);

        if (n3)
                bch2_trans_node_add(trans, trans->paths + path, n3);
        if (n2)
                bch2_trans_node_add(trans, trans->paths + path2, n2);
        bch2_trans_node_add(trans, trans->paths + path1, n1);

        if (n3)
                six_unlock_intent(&n3->c.lock);
        if (n2)
                six_unlock_intent(&n2->c.lock);
        six_unlock_intent(&n1->c.lock);
out:
        if (path2) {
                __bch2_btree_path_unlock(trans, trans->paths + path2);
                bch2_path_put(trans, path2, true);
        }
        if (path1) {
                __bch2_btree_path_unlock(trans, trans->paths + path1);
                bch2_path_put(trans, path1, true);
        }

        bch2_trans_verify_locks(trans);

        time_stats_update(&c->times[n2
                               ? BCH_TIME_btree_node_split
                               : BCH_TIME_btree_node_compact],
                               start_time);
        return ret;
err:
        if (n3)
                bch2_btree_node_free_never_used(as, trans, n3);
        if (n2)
                bch2_btree_node_free_never_used(as, trans, n2);
        bch2_btree_node_free_never_used(as, trans, n1);
        goto out;
}

static void
bch2_btree_insert_keys_interior(struct btree_update *as,
                                struct btree_trans *trans,
                                struct btree_path *path,
                                struct btree *b,
                                struct keylist *keys)
{
        struct btree_path *linked;
        unsigned i;

        __bch2_btree_insert_keys_interior(as, trans, path, b,
                                          path->l[b->c.level].iter, keys);

        btree_update_updated_node(as, b);

        trans_for_each_path_with_node(trans, b, linked, i)
                bch2_btree_node_iter_peek(&linked->l[b->c.level].iter, b);

        bch2_trans_verify_paths(trans);
}

/**
 * bch2_btree_insert_node - insert bkeys into a given btree node
 *
 * @as:                 btree_update object
 * @trans:              btree_trans object
 * @path_idx:           path that points to current node
 * @b:                  node to insert keys into
 * @keys:               list of keys to insert
 * @flags:              transaction commit flags
 *
 * Returns: 0 on success, typically transaction restart error on failure
 *
 * Inserts as many keys as it can into a given btree node, splitting it if full.
 * If a split occurred, this function will return early. This can only happen
 * for leaf nodes -- inserts into interior nodes have to be atomic.
 */
static int bch2_btree_insert_node(struct btree_update *as, struct btree_trans *trans,
                                  btree_path_idx_t path_idx, struct btree *b,
                                  struct keylist *keys, unsigned flags)
{
        struct bch_fs *c = as->c;
        struct btree_path *path = trans->paths + path_idx;
        int old_u64s = le16_to_cpu(btree_bset_last(b)->u64s);
        int old_live_u64s = b->nr.live_u64s;
        int live_u64s_added, u64s_added;
        int ret;

        lockdep_assert_held(&c->gc_lock);
        BUG_ON(!btree_node_intent_locked(path, b->c.level));
        BUG_ON(!b->c.level);
        BUG_ON(!as || as->b);
        bch2_verify_keylist_sorted(keys);

        ret = bch2_btree_node_lock_write(trans, path, &b->c);
        if (ret)
                return ret;

        bch2_btree_node_prep_for_write(trans, path, b);

        if (!bch2_btree_node_insert_fits(b, bch2_keylist_u64s(keys))) {
                bch2_btree_node_unlock_write(trans, path, b);
                goto split;
        }

        btree_node_interior_verify(c, b);

        bch2_btree_insert_keys_interior(as, trans, path, b, keys);

        live_u64s_added = (int) b->nr.live_u64s - old_live_u64s;
        u64s_added = (int) le16_to_cpu(btree_bset_last(b)->u64s) - old_u64s;

        if (b->sib_u64s[0] != U16_MAX && live_u64s_added < 0)
                b->sib_u64s[0] = max(0, (int) b->sib_u64s[0] + live_u64s_added);
        if (b->sib_u64s[1] != U16_MAX && live_u64s_added < 0)
                b->sib_u64s[1] = max(0, (int) b->sib_u64s[1] + live_u64s_added);

        if (u64s_added > live_u64s_added &&
            bch2_maybe_compact_whiteouts(c, b))
                bch2_trans_node_reinit_iter(trans, b);

        bch2_btree_node_unlock_write(trans, path, b);

        btree_node_interior_verify(c, b);
        return 0;
split:
        /*
         * We could attempt to avoid the transaction restart, by calling
         * bch2_btree_path_upgrade() and allocating more nodes:
         */
        if (b->c.level >= as->update_level) {
                trace_and_count(c, trans_restart_split_race, trans, _THIS_IP_, b);
                return btree_trans_restart(trans, BCH_ERR_transaction_restart_split_race);
        }

        return btree_split(as, trans, path_idx, b, keys, flags);
}

int bch2_btree_split_leaf(struct btree_trans *trans,
                          btree_path_idx_t path,
                          unsigned flags)
{
        /* btree_split & merge may both cause paths array to be reallocated */

        struct btree *b = path_l(trans->paths + path)->b;
        struct btree_update *as;
        unsigned l;
        int ret = 0;

        as = bch2_btree_update_start(trans, trans->paths + path,
                                     trans->paths[path].level,
                                     true, flags);
        if (IS_ERR(as))
                return PTR_ERR(as);

        ret = btree_split(as, trans, path, b, NULL, flags);
        if (ret) {
                bch2_btree_update_free(as, trans);
                return ret;
        }

        bch2_btree_update_done(as, trans);

        for (l = trans->paths[path].level + 1;
             btree_node_intent_locked(&trans->paths[path], l) && !ret;
             l++)
                ret = bch2_foreground_maybe_merge(trans, path, l, flags);

        return ret;
}

int __bch2_foreground_maybe_merge(struct btree_trans *trans,
                                  btree_path_idx_t path,
                                  unsigned level,
                                  unsigned flags,
                                  enum btree_node_sibling sib)
{
        struct bch_fs *c = trans->c;
        struct btree_update *as;
        struct bkey_format_state new_s;
        struct bkey_format new_f;
        struct bkey_i delete;
        struct btree *b, *m, *n, *prev, *next, *parent;
        struct bpos sib_pos;
        size_t sib_u64s;
        enum btree_id btree = trans->paths[path].btree_id;
        btree_path_idx_t sib_path = 0, new_path = 0;
        u64 start_time = local_clock();
        int ret = 0;

        BUG_ON(!trans->paths[path].should_be_locked);
        BUG_ON(!btree_node_locked(&trans->paths[path], level));

        b = trans->paths[path].l[level].b;

        if ((sib == btree_prev_sib && bpos_eq(b->data->min_key, POS_MIN)) ||
            (sib == btree_next_sib && bpos_eq(b->data->max_key, SPOS_MAX))) {
                b->sib_u64s[sib] = U16_MAX;
                return 0;
        }

        sib_pos = sib == btree_prev_sib
                ? bpos_predecessor(b->data->min_key)
                : bpos_successor(b->data->max_key);

        sib_path = bch2_path_get(trans, btree, sib_pos,
                                 U8_MAX, level, BTREE_ITER_INTENT, _THIS_IP_);
        ret = bch2_btree_path_traverse(trans, sib_path, false);
        if (ret)
                goto err;

        btree_path_set_should_be_locked(trans->paths + sib_path);

        m = trans->paths[sib_path].l[level].b;

        if (btree_node_parent(trans->paths + path, b) !=
            btree_node_parent(trans->paths + sib_path, m)) {
                b->sib_u64s[sib] = U16_MAX;
                goto out;
        }

        if (sib == btree_prev_sib) {
                prev = m;
                next = b;
        } else {
                prev = b;
                next = m;
        }

        if (!bpos_eq(bpos_successor(prev->data->max_key), next->data->min_key)) {
                struct printbuf buf1 = PRINTBUF, buf2 = PRINTBUF;

                bch2_bpos_to_text(&buf1, prev->data->max_key);
                bch2_bpos_to_text(&buf2, next->data->min_key);
                bch_err(c,
                        "%s(): btree topology error:\n"
                        "  prev ends at   %s\n"
                        "  next starts at %s",
                        __func__, buf1.buf, buf2.buf);
                printbuf_exit(&buf1);
                printbuf_exit(&buf2);
                ret = bch2_topology_error(c);
                goto err;
        }

        bch2_bkey_format_init(&new_s);
        bch2_bkey_format_add_pos(&new_s, prev->data->min_key);
        __bch2_btree_calc_format(&new_s, prev);
        __bch2_btree_calc_format(&new_s, next);
        bch2_bkey_format_add_pos(&new_s, next->data->max_key);
        new_f = bch2_bkey_format_done(&new_s);

        sib_u64s = btree_node_u64s_with_format(b->nr, &b->format, &new_f) +
                btree_node_u64s_with_format(m->nr, &m->format, &new_f);

        if (sib_u64s > BTREE_FOREGROUND_MERGE_HYSTERESIS(c)) {
                sib_u64s -= BTREE_FOREGROUND_MERGE_HYSTERESIS(c);
                sib_u64s /= 2;
                sib_u64s += BTREE_FOREGROUND_MERGE_HYSTERESIS(c);
        }

        sib_u64s = min(sib_u64s, btree_max_u64s(c));
        sib_u64s = min(sib_u64s, (size_t) U16_MAX - 1);
        b->sib_u64s[sib] = sib_u64s;

        if (b->sib_u64s[sib] > c->btree_foreground_merge_threshold)
                goto out;

        parent = btree_node_parent(trans->paths + path, b);
        as = bch2_btree_update_start(trans, trans->paths + path, level, false,
                                     BCH_TRANS_COMMIT_no_enospc|flags);
        ret = PTR_ERR_OR_ZERO(as);
        if (ret)
                goto err;

        trace_and_count(c, btree_node_merge, trans, b);

        bch2_btree_interior_update_will_free_node(as, b);
        bch2_btree_interior_update_will_free_node(as, m);

        n = bch2_btree_node_alloc(as, trans, b->c.level);

        SET_BTREE_NODE_SEQ(n->data,
                           max(BTREE_NODE_SEQ(b->data),
                               BTREE_NODE_SEQ(m->data)) + 1);

        btree_set_min(n, prev->data->min_key);
        btree_set_max(n, next->data->max_key);

        n->data->format  = new_f;
        btree_node_set_format(n, new_f);

        bch2_btree_sort_into(c, n, prev);
        bch2_btree_sort_into(c, n, next);

        bch2_btree_build_aux_trees(n);
        bch2_btree_update_add_new_node(as, n);
        six_unlock_write(&n->c.lock);

        new_path = get_unlocked_mut_path(trans, btree, n->c.level, n->key.k.p);
        six_lock_increment(&n->c.lock, SIX_LOCK_intent);
        mark_btree_node_locked(trans, trans->paths + new_path, n->c.level, BTREE_NODE_INTENT_LOCKED);
        bch2_btree_path_level_init(trans, trans->paths + new_path, n);

        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_trans_verify_paths(trans);

        ret = bch2_btree_insert_node(as, trans, path, parent, &as->parent_keys, flags);
        if (ret)
                goto err_free_update;

        bch2_trans_verify_paths(trans);

        bch2_btree_update_get_open_buckets(as, n);
        bch2_btree_node_write(c, n, SIX_LOCK_intent, 0);

        bch2_btree_node_free_inmem(trans, trans->paths + path, b);
        bch2_btree_node_free_inmem(trans, trans->paths + sib_path, m);

        bch2_trans_node_add(trans, trans->paths + path, n);

        bch2_trans_verify_paths(trans);

        six_unlock_intent(&n->c.lock);

        bch2_btree_update_done(as, trans);

        time_stats_update(&c->times[BCH_TIME_btree_node_merge], start_time);
out:
err:
        if (new_path)
                bch2_path_put(trans, new_path, true);
        bch2_path_put(trans, sib_path, true);
        bch2_trans_verify_locks(trans);
        return ret;
err_free_update:
        bch2_btree_node_free_never_used(as, trans, n);
        bch2_btree_update_free(as, trans);
        goto out;
}

int bch2_btree_node_rewrite(struct btree_trans *trans,
                            struct btree_iter *iter,
                            struct btree *b,
                            unsigned flags)
{
        struct bch_fs *c = trans->c;
        struct btree *n, *parent;
        struct btree_update *as;
        btree_path_idx_t new_path = 0;
        int ret;

        flags |= BCH_TRANS_COMMIT_no_enospc;

        struct btree_path *path = btree_iter_path(trans, iter);
        parent = btree_node_parent(path, b);
        as = bch2_btree_update_start(trans, path, b->c.level, false, flags);
        ret = PTR_ERR_OR_ZERO(as);
        if (ret)
                goto out;

        bch2_btree_interior_update_will_free_node(as, b);

        n = bch2_btree_node_alloc_replacement(as, trans, b);

        bch2_btree_build_aux_trees(n);
        bch2_btree_update_add_new_node(as, n);
        six_unlock_write(&n->c.lock);

        new_path = get_unlocked_mut_path(trans, iter->btree_id, n->c.level, n->key.k.p);
        six_lock_increment(&n->c.lock, SIX_LOCK_intent);
        mark_btree_node_locked(trans, trans->paths + new_path, n->c.level, BTREE_NODE_INTENT_LOCKED);
        bch2_btree_path_level_init(trans, trans->paths + new_path, n);

        trace_and_count(c, btree_node_rewrite, trans, b);

        if (parent) {
                bch2_keylist_add(&as->parent_keys, &n->key);
                ret = bch2_btree_insert_node(as, trans, iter->path,
                                             parent, &as->parent_keys, flags);
                if (ret)
                        goto err;
        } else {
                bch2_btree_set_root(as, trans, btree_iter_path(trans, iter), n);
        }

        bch2_btree_update_get_open_buckets(as, n);
        bch2_btree_node_write(c, n, SIX_LOCK_intent, 0);

        bch2_btree_node_free_inmem(trans, btree_iter_path(trans, iter), b);

        bch2_trans_node_add(trans, trans->paths + iter->path, n);
        six_unlock_intent(&n->c.lock);

        bch2_btree_update_done(as, trans);
out:
        if (new_path)
                bch2_path_put(trans, new_path, true);
        bch2_trans_downgrade(trans);
        return ret;
err:
        bch2_btree_node_free_never_used(as, trans, n);
        bch2_btree_update_free(as, trans);
        goto out;
}

struct async_btree_rewrite {
        struct bch_fs           *c;
        struct work_struct      work;
        struct list_head        list;
        enum btree_id           btree_id;
        unsigned                level;
        struct bpos             pos;
        __le64                  seq;
};

static int async_btree_node_rewrite_trans(struct btree_trans *trans,
                                          struct async_btree_rewrite *a)
{
        struct bch_fs *c = trans->c;
        struct btree_iter iter;
        struct btree *b;
        int ret;

        bch2_trans_node_iter_init(trans, &iter, a->btree_id, a->pos,
                                  BTREE_MAX_DEPTH, a->level, 0);
        b = bch2_btree_iter_peek_node(&iter);
        ret = PTR_ERR_OR_ZERO(b);
        if (ret)
                goto out;

        if (!b || b->data->keys.seq != a->seq) {
                struct printbuf buf = PRINTBUF;

                if (b)
                        bch2_bkey_val_to_text(&buf, c, bkey_i_to_s_c(&b->key));
                else
                        prt_str(&buf, "(null");
                bch_info(c, "%s: node to rewrite not found:, searching for seq %llu, got\n%s",
                         __func__, a->seq, buf.buf);
                printbuf_exit(&buf);
                goto out;
        }

        ret = bch2_btree_node_rewrite(trans, &iter, b, 0);
out:
        bch2_trans_iter_exit(trans, &iter);

        return ret;
}

static void async_btree_node_rewrite_work(struct work_struct *work)
{
        struct async_btree_rewrite *a =
                container_of(work, struct async_btree_rewrite, work);
        struct bch_fs *c = a->c;
        int ret;

        ret = bch2_trans_do(c, NULL, NULL, 0,
                      async_btree_node_rewrite_trans(trans, a));
        bch_err_fn(c, ret);
        bch2_write_ref_put(c, BCH_WRITE_REF_node_rewrite);
        kfree(a);
}

void bch2_btree_node_rewrite_async(struct bch_fs *c, struct btree *b)
{
        struct async_btree_rewrite *a;
        int ret;

        a = kmalloc(sizeof(*a), GFP_NOFS);
        if (!a) {
                bch_err(c, "%s: error allocating memory", __func__);
                return;
        }

        a->c            = c;
        a->btree_id     = b->c.btree_id;
        a->level        = b->c.level;
        a->pos          = b->key.k.p;
        a->seq          = b->data->keys.seq;
        INIT_WORK(&a->work, async_btree_node_rewrite_work);

        if (unlikely(!test_bit(BCH_FS_may_go_rw, &c->flags))) {
                mutex_lock(&c->pending_node_rewrites_lock);
                list_add(&a->list, &c->pending_node_rewrites);
                mutex_unlock(&c->pending_node_rewrites_lock);
                return;
        }

        if (!bch2_write_ref_tryget(c, BCH_WRITE_REF_node_rewrite)) {
                if (test_bit(BCH_FS_started, &c->flags)) {
                        bch_err(c, "%s: error getting c->writes ref", __func__);
                        kfree(a);
                        return;
                }

                ret = bch2_fs_read_write_early(c);
                bch_err_msg(c, ret, "going read-write");
                if (ret) {
                        kfree(a);
                        return;
                }

                bch2_write_ref_get(c, BCH_WRITE_REF_node_rewrite);
        }

        queue_work(c->btree_interior_update_worker, &a->work);
}

void bch2_do_pending_node_rewrites(struct bch_fs *c)
{
        struct async_btree_rewrite *a, *n;

        mutex_lock(&c->pending_node_rewrites_lock);
        list_for_each_entry_safe(a, n, &c->pending_node_rewrites, list) {
                list_del(&a->list);

                bch2_write_ref_get(c, BCH_WRITE_REF_node_rewrite);
                queue_work(c->btree_interior_update_worker, &a->work);
        }
        mutex_unlock(&c->pending_node_rewrites_lock);
}

void bch2_free_pending_node_rewrites(struct bch_fs *c)
{
        struct async_btree_rewrite *a, *n;

        mutex_lock(&c->pending_node_rewrites_lock);
        list_for_each_entry_safe(a, n, &c->pending_node_rewrites, list) {
                list_del(&a->list);

                kfree(a);
        }
        mutex_unlock(&c->pending_node_rewrites_lock);
}

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,
                                        unsigned commit_flags,
                                        bool skip_triggers)
{
        struct bch_fs *c = trans->c;
        struct btree_iter iter2 = { NULL };
        struct btree *parent;
        int ret;

        if (!skip_triggers) {
                ret   = bch2_key_trigger_old(trans, b->c.btree_id, b->c.level + 1,
                                             bkey_i_to_s_c(&b->key),
                                             BTREE_TRIGGER_TRANSACTIONAL) ?:
                        bch2_key_trigger_new(trans, b->c.btree_id, b->c.level + 1,
                                             bkey_i_to_s(new_key),
                                             BTREE_TRIGGER_TRANSACTIONAL);
                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(btree_iter_path(trans, iter), b);
        if (parent) {
                bch2_trans_copy_iter(&iter2, iter);

                iter2.path = bch2_btree_path_make_mut(trans, iter2.path,
                                iter2.flags & BTREE_ITER_INTENT,
                                _THIS_IP_);

                struct btree_path *path2 = btree_iter_path(trans, &iter2);
                BUG_ON(path2->level != b->c.level);
                BUG_ON(!bpos_eq(path2->pos, new_key->k.p));

                btree_path_set_level_up(trans, path2);

                trans->paths_sorted = false;

                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);

                struct jset_entry *e = bch2_trans_jset_entry_alloc(trans,
                                       jset_u64s(new_key->k.u64s));
                ret = PTR_ERR_OR_ZERO(e);
                if (ret)
                        return ret;

                journal_entry_set(e,
                                  BCH_JSET_ENTRY_btree_root,
                                  b->c.btree_id, b->c.level,
                                  new_key, new_key->k.u64s);
        }

        ret = bch2_trans_commit(trans, NULL, NULL, commit_flags);
        if (ret)
                goto err;

        bch2_btree_node_lock_write_nofail(trans, btree_iter_path(trans, iter), &b->c);

        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_node_unlock_write(trans, btree_iter_path(trans, iter), b);
out:
        bch2_trans_iter_exit(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,
                               unsigned commit_flags, bool skip_triggers)
{
        struct bch_fs *c = trans->c;
        struct btree *new_hash = NULL;
        struct btree_path *path = btree_iter_path(trans, iter);
        struct closure cl;
        int ret = 0;

        ret = bch2_btree_path_upgrade(trans, path, b->c.level + 1);
        if (ret)
                return ret;

        closure_init_stack(&cl);

        /*
         * check btree_ptr_hash_val() after @b is locked by
         * btree_iter_traverse():
         */
        if (btree_ptr_hash_val(new_key) != b->hash_val) {
                ret = bch2_btree_cache_cannibalize_lock(trans, &cl);
                if (ret) {
                        ret = drop_locks_do(trans, (closure_sync(&cl), 0));
                        if (ret)
                                return ret;
                }

                new_hash = bch2_btree_node_mem_alloc(trans, false);
        }

        path->intent_ref++;
        ret = __bch2_btree_node_update_key(trans, iter, b, new_hash, new_key,
                                           commit_flags, skip_triggers);
        --path->intent_ref;

        if (new_hash) {
                mutex_lock(&c->btree_cache.lock);
                list_move(&new_hash->list, &c->btree_cache.freeable);
                mutex_unlock(&c->btree_cache.lock);

                six_unlock_write(&new_hash->c.lock);
                six_unlock_intent(&new_hash->c.lock);
        }
        closure_sync(&cl);
        bch2_btree_cache_cannibalize_unlock(trans);
        return ret;
}

int bch2_btree_node_update_key_get_iter(struct btree_trans *trans,
                                        struct btree *b, struct bkey_i *new_key,
                                        unsigned commit_flags, bool skip_triggers)
{
        struct btree_iter iter;
        int ret;

        bch2_trans_node_iter_init(trans, &iter, 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 (btree_iter_path(trans, &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));

        struct bch_extent_ptr *ptr;
        bch2_bkey_drop_ptrs(bkey_i_to_s(new_key), ptr,
                            !bch2_bkey_has_device(bkey_i_to_s(&b->key), ptr->dev));

        ret = bch2_btree_node_update_key(trans, &iter, b, new_key,
                                         commit_flags, skip_triggers);
out:
        bch2_trans_iter_exit(trans, &iter);
        return ret;
}

/* Init code: */

/*
 * Only for filesystem bringup, when first reading the btree roots or allocating
 * btree roots when initializing a new filesystem:
 */
void bch2_btree_set_root_for_read(struct bch_fs *c, struct btree *b)
{
        BUG_ON(btree_node_root(c, b));

        bch2_btree_set_root_inmem(c, b);
}

static int __bch2_btree_root_alloc(struct btree_trans *trans, enum btree_id id)
{
        struct bch_fs *c = trans->c;
        struct closure cl;
        struct btree *b;
        int ret;

        closure_init_stack(&cl);

        do {
                ret = bch2_btree_cache_cannibalize_lock(trans, &cl);
                closure_sync(&cl);
        } while (ret);

        b = bch2_btree_node_mem_alloc(trans, false);
        bch2_btree_cache_cannibalize_unlock(trans);

        set_btree_node_fake(b);
        set_btree_node_need_rewrite(b);
        b->c.level      = 0;
        b->c.btree_id   = id;

        bkey_btree_ptr_init(&b->key);
        b->key.k.p = SPOS_MAX;
        *((u64 *) bkey_i_to_btree_ptr(&b->key)->v.start) = U64_MAX - id;

        bch2_bset_init_first(b, &b->data->keys);
        bch2_btree_build_aux_trees(b);

        b->data->flags = 0;
        btree_set_min(b, POS_MIN);
        btree_set_max(b, SPOS_MAX);
        b->data->format = bch2_btree_calc_format(b);
        btree_node_set_format(b, b->data->format);

        ret = bch2_btree_node_hash_insert(&c->btree_cache, b,
                                          b->c.level, b->c.btree_id);
        BUG_ON(ret);

        bch2_btree_set_root_inmem(c, b);

        six_unlock_write(&b->c.lock);
        six_unlock_intent(&b->c.lock);
        return 0;
}

void bch2_btree_root_alloc(struct bch_fs *c, enum btree_id id)
{
        bch2_trans_run(c, __bch2_btree_root_alloc(trans, id));
}

void bch2_btree_updates_to_text(struct printbuf *out, struct bch_fs *c)
{
        struct btree_update *as;

        mutex_lock(&c->btree_interior_update_lock);
        list_for_each_entry(as, &c->btree_interior_update_list, list)
                prt_printf(out, "%p m %u w %u r %u j %llu\n",
                       as,
                       as->mode,
                       as->nodes_written,
                       closure_nr_remaining(&as->cl),
                       as->journal.seq);
        mutex_unlock(&c->btree_interior_update_lock);
}

static bool bch2_btree_interior_updates_pending(struct bch_fs *c)
{
        bool ret;

        mutex_lock(&c->btree_interior_update_lock);
        ret = !list_empty(&c->btree_interior_update_list);
        mutex_unlock(&c->btree_interior_update_lock);

        return ret;
}

bool bch2_btree_interior_updates_flush(struct bch_fs *c)
{
        bool ret = bch2_btree_interior_updates_pending(c);

        if (ret)
                closure_wait_event(&c->btree_interior_update_wait,
                                   !bch2_btree_interior_updates_pending(c));
        return ret;
}

void bch2_journal_entry_to_btree_root(struct bch_fs *c, struct jset_entry *entry)
{
        struct btree_root *r = bch2_btree_id_root(c, entry->btree_id);

        mutex_lock(&c->btree_root_lock);

        r->level = entry->level;
        r->alive = true;
        bkey_copy(&r->key, (struct bkey_i *) entry->start);

        mutex_unlock(&c->btree_root_lock);
}

struct jset_entry *
bch2_btree_roots_to_journal_entries(struct bch_fs *c,
                                    struct jset_entry *end,
                                    unsigned long skip)
{
        unsigned i;

        mutex_lock(&c->btree_root_lock);

        for (i = 0; i < btree_id_nr_alive(c); i++) {
                struct btree_root *r = bch2_btree_id_root(c, i);

                if (r->alive && !test_bit(i, &skip)) {
                        journal_entry_set(end, BCH_JSET_ENTRY_btree_root,
                                          i, r->level, &r->key, r->key.k.u64s);
                        end = vstruct_next(end);
                }
        }

        mutex_unlock(&c->btree_root_lock);

        return end;
}

void bch2_fs_btree_interior_update_exit(struct bch_fs *c)
{
        if (c->btree_interior_update_worker)
                destroy_workqueue(c->btree_interior_update_worker);
        mempool_exit(&c->btree_interior_update_pool);
}

void bch2_fs_btree_interior_update_init_early(struct bch_fs *c)
{
        mutex_init(&c->btree_reserve_cache_lock);
        INIT_LIST_HEAD(&c->btree_interior_update_list);
        INIT_LIST_HEAD(&c->btree_interior_updates_unwritten);
        mutex_init(&c->btree_interior_update_lock);
        INIT_WORK(&c->btree_interior_update_work, btree_interior_update_work);

        INIT_LIST_HEAD(&c->pending_node_rewrites);
        mutex_init(&c->pending_node_rewrites_lock);
}

int bch2_fs_btree_interior_update_init(struct bch_fs *c)
{
        c->btree_interior_update_worker =
                alloc_workqueue("btree_update", WQ_UNBOUND|WQ_MEM_RECLAIM, 8);
        if (!c->btree_interior_update_worker)
                return -BCH_ERR_ENOMEM_btree_interior_update_worker_init;

        if (mempool_init_kmalloc_pool(&c->btree_interior_update_pool, 1,
                                      sizeof(struct btree_update)))
                return -BCH_ERR_ENOMEM_btree_interior_update_pool_init;

        return 0;
}