path: root/fs/bcachefs/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_update.h"
#include "btree_update_interior.h"
#include "btree_io.h"
#include "btree_iter.h"
#include "btree_locking.h"
#include "buckets.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 void btree_node_will_make_reachable(struct btree_update *,
					   struct btree *);
static void btree_update_drop_new_node(struct bch_fs *, struct btree *);

/* Debug code: */

/*
 * Verify that child nodes correctly span parent node's range:
 */
static void btree_node_interior_verify(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;

	BUG_ON(!b->c.level);

	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);

		BUG_ON(bkey_cmp(next_node, bp.v->min_key));

		bch2_btree_node_iter_advance(&iter, b);

		if (bch2_btree_node_iter_end(&iter)) {
			BUG_ON(bkey_cmp(k.k->p, b->key.k.p));
			break;
		}

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

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

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

	bch2_bkey_format_add_pos(s, b->data->min_key);

	for_each_bset(b, t)
		bset_tree_for_each_key(b, t, k)
			if (!bkey_whiteout(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_btree_calc_format(&s, b);

	return bch2_bkey_format_done(&s);
}

static size_t btree_node_u64s_with_format(struct btree *b,
					  struct bkey_format *new_f)
{
	struct bkey_format *old_f = &b->format;

	/* stupid integer promotion rules */
	ssize_t delta =
	    (((int) new_f->key_u64s - old_f->key_u64s) *
	     (int) b->nr.packed_keys) +
	    (((int) new_f->key_u64s - BKEY_U64s) *
	     (int) b->nr.unpacked_keys);

	BUG_ON(delta + b->nr.live_u64s < 0);

	return b->nr.live_u64s + delta;
}

/**
 * btree_node_format_fits - check if we could rewrite node with a new format
 *
 * This assumes all keys can pack with the new format -- it just checks if
 * the re-packed keys would fit inside the node itself.
 */
bool bch2_btree_node_format_fits(struct bch_fs *c, struct btree *b,
				 struct bkey_format *new_f)
{
	size_t u64s = btree_node_u64s_with_format(b, new_f);

	return __vstruct_bytes(struct btree_node, u64s) < btree_bytes(c);
}

/* Btree node freeing/allocation: */

static bool btree_key_matches(struct bch_fs *c,
			      struct bkey_s_c l,
			      struct bkey_s_c r)
{
	struct bkey_ptrs_c ptrs1 = bch2_bkey_ptrs_c(l);
	struct bkey_ptrs_c ptrs2 = bch2_bkey_ptrs_c(r);
	const struct bch_extent_ptr *ptr1, *ptr2;

	bkey_for_each_ptr(ptrs1, ptr1)
		bkey_for_each_ptr(ptrs2, ptr2)
			if (ptr1->dev == ptr2->dev &&
			    ptr1->gen == ptr2->gen &&
			    ptr1->offset == ptr2->offset)
				return true;

	return false;
}

/*
 * We're doing the index update that makes @b unreachable, update stuff to
 * reflect that:
 *
 * Must be called _before_ btree_update_updated_root() or
 * btree_update_updated_node:
 */
static void bch2_btree_node_free_index(struct btree_update *as, struct btree *b,
				       struct bkey_s_c k,
				       struct bch_fs_usage *stats)
{
	struct bch_fs *c = as->c;
	struct pending_btree_node_free *d;

	for (d = as->pending; d < as->pending + as->nr_pending; d++)
		if (!bkey_cmp(k.k->p, d->key.k.p) &&
		    btree_key_matches(c, k, bkey_i_to_s_c(&d->key)))
			goto found;
	BUG();
found:
	BUG_ON(d->index_update_done);
	d->index_update_done = true;

	/*
	 * We're dropping @k from the btree, but it's still live until the
	 * index update is persistent so we need to keep a reference around for
	 * mark and sweep to find - that's primarily what the
	 * btree_node_pending_free list is for.
	 *
	 * So here (when we set index_update_done = true), we're moving an
	 * existing reference to a different part of the larger "gc keyspace" -
	 * and the new position comes after the old position, since GC marks
	 * the pending free list after it walks the btree.
	 *
	 * If we move the reference while mark and sweep is _between_ the old
	 * and the new position, mark and sweep will see the reference twice
	 * and it'll get double accounted - so check for that here and subtract
	 * to cancel out one of mark and sweep's markings if necessary:
	 */

	if (gc_pos_cmp(c->gc_pos, b
		       ? gc_pos_btree_node(b)
		       : gc_pos_btree_root(as->btree_id)) >= 0 &&
	    gc_pos_cmp(c->gc_pos, gc_phase(GC_PHASE_PENDING_DELETE)) < 0)
		bch2_mark_key_locked(c, bkey_i_to_s_c(&d->key),
			      0, 0, NULL, 0,
			      BTREE_TRIGGER_OVERWRITE|
			      BTREE_TRIGGER_GC);
}

static void __btree_node_free(struct bch_fs *c, struct btree *b)
{
	trace_btree_node_free(c, 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);

	bch2_btree_node_hash_remove(&c->btree_cache, b);

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

void bch2_btree_node_free_never_inserted(struct bch_fs *c, struct btree *b)
{
	struct open_buckets ob = b->ob;

	btree_update_drop_new_node(c, b);

	b->ob.nr = 0;

	clear_btree_node_dirty(b);

	btree_node_lock_type(c, b, SIX_LOCK_write);
	__btree_node_free(c, b);
	six_unlock_write(&b->c.lock);

	bch2_open_buckets_put(c, &ob);
}

void bch2_btree_node_free_inmem(struct bch_fs *c, struct btree *b,
				struct btree_iter *iter)
{
	struct btree_iter *linked;

	trans_for_each_iter(iter->trans, linked)
		BUG_ON(linked->l[b->c.level].b == b);

	/*
	 * 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);

	six_lock_write(&b->c.lock, NULL, NULL);
	__btree_node_free(c, b);
	six_unlock_write(&b->c.lock);
	six_unlock_intent(&b->c.lock);
}

static void bch2_btree_node_free_ondisk(struct bch_fs *c,
			struct pending_btree_node_free *pending,
			u64 journal_seq)
{
	BUG_ON(!pending->index_update_done);

	bch2_mark_key(c, bkey_i_to_s_c(&pending->key),
		      0, 0, NULL, journal_seq, BTREE_TRIGGER_OVERWRITE);

	if (gc_visited(c, gc_phase(GC_PHASE_PENDING_DELETE)))
		bch2_mark_key(c, bkey_i_to_s_c(&pending->key),
			      0, 0, NULL, journal_seq,
			      BTREE_TRIGGER_OVERWRITE|
			      BTREE_TRIGGER_GC);
}

static struct btree *__bch2_btree_node_alloc(struct bch_fs *c,
					     struct disk_reservation *res,
					     struct closure *cl,
					     unsigned flags)
{
	struct write_point *wp;
	struct btree *b;
	BKEY_PADDED(k) tmp;
	struct open_buckets ob = { .nr = 0 };
	struct bch_devs_list devs_have = (struct bch_devs_list) { 0 };
	unsigned nr_reserve;
	enum alloc_reserve alloc_reserve;

	if (flags & BTREE_INSERT_USE_ALLOC_RESERVE) {
		nr_reserve	= 0;
		alloc_reserve	= RESERVE_ALLOC;
	} else if (flags & BTREE_INSERT_USE_RESERVE) {
		nr_reserve	= BTREE_NODE_RESERVE / 2;
		alloc_reserve	= RESERVE_BTREE;
	} else {
		nr_reserve	= BTREE_NODE_RESERVE;
		alloc_reserve	= RESERVE_NONE;
	}

	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];

		ob = 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:
	wp = bch2_alloc_sectors_start(c, c->opts.foreground_target, 0,
				      writepoint_ptr(&c->btree_write_point),
				      &devs_have,
				      res->nr_replicas,
				      c->opts.metadata_replicas_required,
				      alloc_reserve, 0, cl);
	if (IS_ERR(wp))
		return ERR_CAST(wp);

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

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

		bch2_alloc_sectors_done(c, wp);
		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);

	bch2_alloc_sectors_append_ptrs(c, wp, &tmp.k, c->opts.btree_node_size);

	bch2_open_bucket_get(c, wp, &ob);
	bch2_alloc_sectors_done(c, wp);
mem_alloc:
	b = bch2_btree_node_mem_alloc(c);

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

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

	return b;
}

static struct btree *bch2_btree_node_alloc(struct btree_update *as, unsigned level)
{
	struct bch_fs *c = as->c;
	struct btree *b;
	int ret;

	BUG_ON(level >= BTREE_MAX_DEPTH);
	BUG_ON(!as->reserve->nr);

	b = as->reserve->b[--as->reserve->nr];

	set_btree_node_accessed(b);
	set_btree_node_dirty(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;

	memset(&b->nr, 0, sizeof(b->nr));
	b->data->magic = cpu_to_le64(bset_magic(c));
	b->data->flags = 0;
	SET_BTREE_NODE_ID(b->data, as->btree_id);
	SET_BTREE_NODE_LEVEL(b->data, level);
	b->data->ptr = bch2_bkey_ptrs_c(bkey_i_to_s_c(&b->key)).start->ptr;

	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;
		bp->v.sectors		= cpu_to_le16(c->opts.btree_node_size);
	}

	if (c->sb.features & (1ULL << BCH_FEATURE_new_extent_overwrite))
		SET_BTREE_NODE_NEW_EXTENT_OVERWRITE(b->data, true);

	if (btree_node_is_extents(b) &&
	    !BTREE_NODE_NEW_EXTENT_OVERWRITE(b->data))
		set_btree_node_old_extent_overwrite(b);

	bch2_btree_build_aux_trees(b);

	btree_node_will_make_reachable(as, b);

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

	trace_btree_node_alloc(c, b);
	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;
}

struct btree *__bch2_btree_node_alloc_replacement(struct btree_update *as,
						  struct btree *b,
						  struct bkey_format format)
{
	struct btree *n;

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

	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);

	n->key.k.p = b->key.k.p;
	return n;
}

static struct btree *bch2_btree_node_alloc_replacement(struct btree_update *as,
						       struct btree *b)
{
	struct bkey_format new_f = 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, &new_f))
		new_f = b->format;

	return __bch2_btree_node_alloc_replacement(as, b, new_f);
}

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

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

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

	six_unlock_write(&b->c.lock);

	return b;
}

static void bch2_btree_reserve_put(struct bch_fs *c, struct btree_reserve *reserve)
{
	bch2_disk_reservation_put(c, &reserve->disk_res);

	mutex_lock(&c->btree_reserve_cache_lock);

	while (reserve->nr) {
		struct btree *b = reserve->b[--reserve->nr];

		six_unlock_write(&b->c.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);
		}

		btree_node_lock_type(c, b, SIX_LOCK_write);
		__btree_node_free(c, b);
		six_unlock_write(&b->c.lock);

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

	mutex_unlock(&c->btree_reserve_cache_lock);

	mempool_free(reserve, &c->btree_reserve_pool);
}

static struct btree_reserve *bch2_btree_reserve_get(struct bch_fs *c,
						    unsigned nr_nodes,
						    unsigned flags,
						    struct closure *cl)
{
	struct btree_reserve *reserve;
	struct btree *b;
	struct disk_reservation disk_res = { 0, 0 };
	unsigned sectors = nr_nodes * c->opts.btree_node_size;
	int ret, disk_res_flags = 0;

	if (flags & BTREE_INSERT_NOFAIL)
		disk_res_flags |= BCH_DISK_RESERVATION_NOFAIL;

	/*
	 * This check isn't necessary for correctness - it's just to potentially
	 * prevent us from doing a lot of work that'll end up being wasted:
	 */
	ret = bch2_journal_error(&c->journal);
	if (ret)
		return ERR_PTR(ret);

	if (bch2_disk_reservation_get(c, &disk_res, sectors,
				      c->opts.metadata_replicas,
				      disk_res_flags))
		return ERR_PTR(-ENOSPC);

	BUG_ON(nr_nodes > BTREE_RESERVE_MAX);

	/*
	 * Protects reaping from the btree node cache and using the btree node
	 * open bucket reserve:
	 */
	ret = bch2_btree_cache_cannibalize_lock(c, cl);
	if (ret) {
		bch2_disk_reservation_put(c, &disk_res);
		return ERR_PTR(ret);
	}

	reserve = mempool_alloc(&c->btree_reserve_pool, GFP_NOIO);

	reserve->disk_res = disk_res;
	reserve->nr = 0;

	while (reserve->nr < nr_nodes) {
		b = __bch2_btree_node_alloc(c, &disk_res,
					    flags & BTREE_INSERT_NOWAIT
					    ? NULL : cl, flags);
		if (IS_ERR(b)) {
			ret = PTR_ERR(b);
			goto err_free;
		}

		ret = bch2_mark_bkey_replicas(c, bkey_i_to_s_c(&b->key));
		if (ret)
			goto err_free;

		reserve->b[reserve->nr++] = b;
	}

	bch2_btree_cache_cannibalize_unlock(c);
	return reserve;
err_free:
	bch2_btree_reserve_put(c, reserve);
	bch2_btree_cache_cannibalize_unlock(c);
	trace_btree_reserve_get_fail(c, nr_nodes, cl);
	return ERR_PTR(ret);
}

/* Asynchronous interior node update machinery */

static void __bch2_btree_update_free(struct btree_update *as)
{
	struct bch_fs *c = as->c;

	bch2_journal_preres_put(&c->journal, &as->journal_preres);

	bch2_journal_pin_drop(&c->journal, &as->journal);
	bch2_journal_pin_flush(&c->journal, &as->journal);

	BUG_ON(as->nr_new_nodes || as->nr_pending);

	if (as->reserve)
		bch2_btree_reserve_put(c, as->reserve);

	list_del(&as->unwritten_list);
	list_del(&as->list);

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

	closure_wake_up(&c->btree_interior_update_wait);
}

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

	mutex_lock(&c->btree_interior_update_lock);
	__bch2_btree_update_free(as);
	mutex_unlock(&c->btree_interior_update_lock);
}

static inline bool six_trylock_intentwrite(struct six_lock *lock)
{
	if (!six_trylock_intent(lock))
		return false;

	if (!six_trylock_write(lock)) {
		six_unlock_intent(lock);
		return false;
	}

	return true;
}

static void btree_update_nodes_written(struct closure *cl)
{
	struct btree_update *as = container_of(cl, struct btree_update, cl);
	struct btree *nodes_need_write[BTREE_MAX_DEPTH * 2 + GC_MERGE_NODES + 1];
	unsigned nr_nodes_need_write;
	struct journal_res res = { 0 };
	struct bch_fs *c = as->c;
	struct btree_root *r;
	struct btree *b;
	int ret;

	/*
	 * 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.
	 */
	mutex_lock(&c->btree_interior_update_lock);
	as->nodes_written = true;
again:
	nr_nodes_need_write = 0;
	as = list_first_entry_or_null(&c->btree_interior_updates_unwritten,
				      struct btree_update, unwritten_list);
	if (!as || !as->nodes_written) {
		mutex_unlock(&c->btree_interior_update_lock);
		return;
	}

	b = as->b;
	if (b && !six_trylock_intentwrite(&b->c.lock)) {
		mutex_unlock(&c->btree_interior_update_lock);

		btree_node_lock_type(c, b, SIX_LOCK_intent);
		six_lock_write(&b->c.lock, NULL, NULL);

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

		mutex_lock(&c->btree_interior_update_lock);
		goto again;
	}

	ret = bch2_journal_res_get(&c->journal, &res, as->journal_u64s,
				   JOURNAL_RES_GET_NONBLOCK|
				   JOURNAL_RES_GET_RESERVED);
	if (ret == -EAGAIN) {
		unsigned u64s = as->journal_u64s;

		if (b) {
			six_unlock_write(&b->c.lock);
			six_unlock_intent(&b->c.lock);
		}

		mutex_unlock(&c->btree_interior_update_lock);

		ret = bch2_journal_res_get(&c->journal, &res, u64s,
					   JOURNAL_RES_GET_CHECK|
					   JOURNAL_RES_GET_RESERVED);
		if (!ret) {
			mutex_lock(&c->btree_interior_update_lock);
			goto again;
		}
	}

	if (!ret) {
		struct journal_buf *buf = &c->journal.buf[res.idx];
		struct jset_entry *entry = vstruct_idx(buf->data, res.offset);

		res.offset	+= as->journal_u64s;
		res.u64s	-= as->journal_u64s;
		memcpy_u64s(entry, as->journal_entries, as->journal_u64s);
	} else {
		/*
		 * On journal error we have to run most of the normal path so
		 * that shutdown works - unblocking btree node writes in
		 * particular and writing them if needed - except for
		 * journalling the update:
		 */

		BUG_ON(!bch2_journal_error(&c->journal));
	}

	switch (as->mode) {
	case BTREE_INTERIOR_NO_UPDATE:
		BUG();
	case BTREE_INTERIOR_UPDATING_NODE:
		/* @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:
		 */

		list_del(&as->write_blocked_list);

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

			i->journal_seq = cpu_to_le64(
				max(res.seq,
				    le64_to_cpu(i->journal_seq)));

			bch2_btree_add_journal_pin(c, b, res.seq);
		}

		nodes_need_write[nr_nodes_need_write++] = b;

		six_unlock_write(&b->c.lock);
		six_unlock_intent(&b->c.lock);
		break;

	case BTREE_INTERIOR_UPDATING_AS:
		BUG_ON(b);
		break;

	case BTREE_INTERIOR_UPDATING_ROOT:
		r = &c->btree_roots[as->btree_id];

		BUG_ON(b);

		mutex_lock(&c->btree_root_lock);
		bkey_copy(&r->key, as->parent_keys.keys);
		r->level = as->level;
		r->alive = true;
		c->btree_roots_dirty = true;
		mutex_unlock(&c->btree_root_lock);
		break;
	}

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

	bch2_journal_res_put(&c->journal, &res);
	bch2_journal_preres_put(&c->journal, &as->journal_preres);

	while (as->nr_new_nodes) {
		b = as->new_nodes[--as->nr_new_nodes];

		BUG_ON(b->will_make_reachable != (unsigned long) as);
		b->will_make_reachable = 0;

		nodes_need_write[nr_nodes_need_write++] = b;
	}

	while (as->nr_pending)
		bch2_btree_node_free_ondisk(c,
			&as->pending[--as->nr_pending], res.seq);

	__bch2_btree_update_free(as);
	/*
	 * for flush_held_btree_writes() waiting on updates to flush or
	 * nodes to be writeable:
	 */
	closure_wake_up(&c->btree_interior_update_wait);

	/*
	 * Can't take btree node locks while holding btree_interior_update_lock:
	 * */
	mutex_unlock(&c->btree_interior_update_lock);

	/* Do btree writes after dropping journal res/locks: */
	while (nr_nodes_need_write) {
		b = nodes_need_write[--nr_nodes_need_write];

		btree_node_lock_type(c, b, SIX_LOCK_read);
		bch2_btree_node_write_cond(c, b, btree_node_need_write(b));
		six_unlock_read(&b->c.lock);
	}

	mutex_lock(&c->btree_interior_update_lock);
	goto again;
}

/*
 * 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));

	as->mode	= BTREE_INTERIOR_UPDATING_NODE;
	as->b		= b;
	as->level	= b->c.level;
	list_add(&as->write_blocked_list, &b->write_blocked);

	mutex_unlock(&c->btree_interior_update_lock);
}

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;

	/*
	 * When we write a new btree root, we have to drop our journal pin
	 * _before_ the new nodes are technically reachable; see
	 * btree_update_nodes_written().
	 *
	 * This goes for journal pins that are recursively blocked on us - so,
	 * just transfer the journal pin to the new interior update so
	 * btree_update_nodes_written() can drop it.
	 */
	bch2_journal_pin_copy(&c->journal, &as->journal, &child->journal, NULL);
	bch2_journal_pin_drop(&c->journal, &child->journal);
}

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

	BUG_ON(as->mode != BTREE_INTERIOR_NO_UPDATE);
	BUG_ON(!bch2_keylist_empty(&as->parent_keys));

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

	as->mode	= BTREE_INTERIOR_UPDATING_ROOT;
	as->level	= b->c.level;
	bch2_keylist_add(&as->parent_keys, &b->key);
	mutex_unlock(&c->btree_interior_update_lock);
}

static void btree_node_will_make_reachable(struct btree_update *as,
					   struct btree *b)
{
	struct bch_fs *c = as->c;

	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;

	closure_get(&as->cl);
	mutex_unlock(&c->btree_interior_update_lock);
}

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);
	v = xchg(&b->will_make_reachable, 0);
	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 btree_interior_update_add_node_reference(struct btree_update *as,
						     struct btree *b)
{
	struct bch_fs *c = as->c;
	struct pending_btree_node_free *d;

	mutex_lock(&c->btree_interior_update_lock);

	/* Add this node to the list of nodes being freed: */
	BUG_ON(as->nr_pending >= ARRAY_SIZE(as->pending));

	d = &as->pending[as->nr_pending++];
	d->index_update_done	= false;
	d->seq			= b->data->keys.seq;
	d->btree_id		= b->c.btree_id;
	d->level		= b->c.level;
	bkey_copy(&d->key, &b->key);

	mutex_unlock(&c->btree_interior_update_lock);
}

/*
 * @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:
 */
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;

	btree_interior_update_add_node_reference(as, b);

	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(&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(b);
	clear_btree_node_need_write(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, NULL);
	bch2_journal_pin_drop(&c->journal, &w->journal);

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

	mutex_unlock(&c->btree_interior_update_lock);
}

void bch2_btree_update_done(struct btree_update *as)
{
	BUG_ON(as->mode == BTREE_INTERIOR_NO_UPDATE);

	bch2_btree_reserve_put(as->c, as->reserve);
	as->reserve = NULL;

	continue_at(&as->cl, btree_update_nodes_written, system_freezable_wq);
}

struct btree_update *
bch2_btree_update_start(struct btree_trans *trans, enum btree_id id,
			unsigned nr_nodes, unsigned flags,
			struct closure *cl)
{
	struct bch_fs *c = trans->c;
	struct journal_preres journal_preres = { 0 };
	struct btree_reserve *reserve;
	struct btree_update *as;
	int ret;

	ret = bch2_journal_preres_get(&c->journal, &journal_preres,
				      BTREE_UPDATE_JOURNAL_RES,
				      JOURNAL_RES_GET_NONBLOCK);
	if (ret == -EAGAIN) {
		if (flags & BTREE_INSERT_NOUNLOCK)
			return ERR_PTR(-EINTR);

		bch2_trans_unlock(trans);

		ret = bch2_journal_preres_get(&c->journal, &journal_preres,
					      BTREE_UPDATE_JOURNAL_RES, 0);
		if (ret)
			return ERR_PTR(ret);

		if (!bch2_trans_relock(trans)) {
			bch2_journal_preres_put(&c->journal, &journal_preres);
			return ERR_PTR(-EINTR);
		}
	}

	reserve = bch2_btree_reserve_get(c, nr_nodes, flags, cl);
	if (IS_ERR(reserve)) {
		bch2_journal_preres_put(&c->journal, &journal_preres);
		return ERR_CAST(reserve);
	}

	as = mempool_alloc(&c->btree_interior_update_pool, GFP_NOIO);
	memset(as, 0, sizeof(*as));
	closure_init(&as->cl, NULL);
	as->c		= c;
	as->mode	= BTREE_INTERIOR_NO_UPDATE;
	as->btree_id	= id;
	as->reserve	= reserve;
	INIT_LIST_HEAD(&as->write_blocked_list);
	INIT_LIST_HEAD(&as->unwritten_list);
	as->journal_preres = journal_preres;

	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);

	return as;
}

/* 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))));

	btree_node_root(c, b) = b;
	mutex_unlock(&c->btree_root_lock);

	bch2_recalc_btree_reserve(c);
}

static void bch2_btree_set_root_inmem(struct btree_update *as, struct btree *b)
{
	struct bch_fs *c = as->c;
	struct btree *old = btree_node_root(c, b);
	struct bch_fs_usage_online *fs_usage;

	__bch2_btree_set_root_inmem(c, b);

	mutex_lock(&c->btree_interior_update_lock);
	percpu_down_read(&c->mark_lock);
	fs_usage = bch2_fs_usage_scratch_get(c);

	bch2_mark_key_locked(c, bkey_i_to_s_c(&b->key),
		      0, 0, &fs_usage->u, 0,
		      BTREE_TRIGGER_INSERT);
	if (gc_visited(c, gc_pos_btree_root(b->c.btree_id)))
		bch2_mark_key_locked(c, bkey_i_to_s_c(&b->key),
				     0, 0, NULL, 0,
				     BTREE_TRIGGER_INSERT|
				     BTREE_TRIGGER_GC);

	if (old && !btree_node_fake(old))
		bch2_btree_node_free_index(as, NULL,
					   bkey_i_to_s_c(&old->key),
					   &fs_usage->u);
	bch2_fs_usage_apply(c, fs_usage, &as->reserve->disk_res, 0);

	bch2_fs_usage_scratch_put(c, fs_usage);
	percpu_up_read(&c->mark_lock);
	mutex_unlock(&c->btree_interior_update_lock);
}

/**
 * bch_btree_set_root - update the root in memory and on disk
 *
 * To ensure forward progress, the current task must not be holding any
 * btree node write locks. However, you must hold an intent lock on the
 * old root.
 *
 * Note: This allocates a journal entry but doesn't add any keys to
 * it.  All the btree roots are part of every journal write, so there
 * is nothing new to be done.  This just guarantees that there is a
 * journal write.
 */
static void bch2_btree_set_root(struct btree_update *as, struct btree *b,
				struct btree_iter *iter)
{
	struct bch_fs *c = as->c;
	struct btree *old;

	trace_btree_set_root(c, b);
	BUG_ON(!b->written &&
	       !test_bit(BCH_FS_HOLD_BTREE_WRITES, &c->flags));

	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(old, iter);

	bch2_btree_set_root_inmem(as, 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(old, iter);
}

/* Interior node updates: */

static void bch2_insert_fixup_btree_ptr(struct btree_update *as, struct btree *b,
					struct btree_iter *iter,
					struct bkey_i *insert,
					struct btree_node_iter *node_iter)
{
	struct bch_fs *c = as->c;
	struct bch_fs_usage_online *fs_usage;
	struct jset_entry *entry;
	struct bkey_packed *k;
	struct bkey tmp;

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

	entry = (void *) &as->journal_entries[as->journal_u64s];
	memset(entry, 0, sizeof(*entry));
	entry->u64s	= cpu_to_le16(insert->k.u64s);
	entry->type	= BCH_JSET_ENTRY_btree_keys;
	entry->btree_id = b->c.btree_id;
	entry->level	= b->c.level;
	memcpy_u64s_small(entry->_data, insert, insert->k.u64s);
	as->journal_u64s += jset_u64s(insert->k.u64s);

	mutex_lock(&c->btree_interior_update_lock);
	percpu_down_read(&c->mark_lock);
	fs_usage = bch2_fs_usage_scratch_get(c);

	bch2_mark_key_locked(c, bkey_i_to_s_c(insert),
			     0, 0, &fs_usage->u, 0,
			     BTREE_TRIGGER_INSERT);

	if (gc_visited(c, gc_pos_btree_node(b)))
		bch2_mark_key_locked(c, bkey_i_to_s_c(insert),
				     0, 0, NULL, 0,
				     BTREE_TRIGGER_INSERT|
				     BTREE_TRIGGER_GC);

	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);

	/*
	 * If we're overwriting, look up pending delete and mark so that gc
	 * marks it on the pending delete list:
	 */
	if (k && !bkey_cmp_packed(b, k, &insert->k))
		bch2_btree_node_free_index(as, b,
					   bkey_disassemble(b, k, &tmp),
					   &fs_usage->u);

	bch2_fs_usage_apply(c, fs_usage, &as->reserve->disk_res, 0);

	bch2_fs_usage_scratch_put(c, fs_usage);
	percpu_up_read(&c->mark_lock);
	mutex_unlock(&c->btree_interior_update_lock);

	bch2_btree_bset_insert_key(iter, b, node_iter, insert);
	set_btree_node_dirty(b);
	set_btree_node_need_write(b);
}

/*
 * Move keys from n1 (original replacement node, now lower node) to n2 (higher
 * node)
 */
static struct btree *__btree_split_node(struct btree_update *as,
					struct btree *n1,
					struct btree_iter *iter)
{
	size_t nr_packed = 0, nr_unpacked = 0;
	struct btree *n2;
	struct bset *set1, *set2;
	struct bkey_packed *k, *prev = NULL;

	n2 = bch2_btree_node_alloc(as, n1->c.level);

	n2->data->max_key	= n1->data->max_key;
	n2->data->format	= n1->format;
	SET_BTREE_NODE_SEQ(n2->data, BTREE_NODE_SEQ(n1->data));
	n2->key.k.p = n1->key.k.p;

	btree_node_set_format(n2, n2->data->format);

	set1 = btree_bset_first(n1);
	set2 = btree_bset_first(n2);

	/*
	 * Has to be a linear search because we don't have an auxiliary
	 * search tree yet
	 */
	k = set1->start;
	while (1) {
		struct bkey_packed *n = bkey_next_skip_noops(k, vstruct_last(set1));

		if (n == vstruct_last(set1))
			break;
		if (k->_data - set1->_data >= (le16_to_cpu(set1->u64s) * 3) / 5)
			break;

		if (bkey_packed(k))
			nr_packed++;
		else
			nr_unpacked++;

		prev = k;
		k = n;
	}

	BUG_ON(!prev);

	btree_set_max(n1, bkey_unpack_pos(n1, prev));
	btree_set_min(n2, bkey_successor(n1->key.k.p));

	set2->u64s = cpu_to_le16((u64 *) vstruct_end(set1) - (u64 *) k);
	set1->u64s = cpu_to_le16(le16_to_cpu(set1->u64s) - le16_to_cpu(set2->u64s));

	set_btree_bset_end(n1, n1->set);
	set_btree_bset_end(n2, n2->set);

	n2->nr.live_u64s	= le16_to_cpu(set2->u64s);
	n2->nr.bset_u64s[0]	= le16_to_cpu(set2->u64s);
	n2->nr.packed_keys	= n1->nr.packed_keys - nr_packed;
	n2->nr.unpacked_keys	= n1->nr.unpacked_keys - nr_unpacked;

	n1->nr.live_u64s	= le16_to_cpu(set1->u64s);
	n1->nr.bset_u64s[0]	= le16_to_cpu(set1->u64s);
	n1->nr.packed_keys	= nr_packed;
	n1->nr.unpacked_keys	= nr_unpacked;

	BUG_ON(!set1->u64s);
	BUG_ON(!set2->u64s);

	memcpy_u64s(set2->start,
		    vstruct_end(set1),
		    le16_to_cpu(set2->u64s));

	btree_node_reset_sib_u64s(n1);
	btree_node_reset_sib_u64s(n2);

	bch2_verify_btree_nr_keys(n1);
	bch2_verify_btree_nr_keys(n2);

	if (n1->c.level) {
		btree_node_interior_verify(n1);
		btree_node_interior_verify(n2);
	}

	return n2;
}

/*
 * 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 *b,
				    struct btree_iter *iter,
				    struct keylist *keys)
{
	struct btree_node_iter node_iter;
	struct bkey_i *k = bch2_keylist_front(keys);
	struct bkey_packed *src, *dst, *n;
	struct bset *i;

	/*
	 * XXX
	 *
	 * these updates must be journalled
	 *
	 * oops
	 */

	BUG_ON(btree_node_type(b) != BKEY_TYPE_BTREE);

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

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

		bch2_insert_fixup_btree_ptr(as, b, iter, k, &node_iter);
		bch2_keylist_pop_front(keys);
	}

	/*
	 * We can't tolerate whiteouts here - with whiteouts there can be
	 * duplicate keys, and it would be rather bad if we picked a duplicate
	 * for the pivot:
	 */
	i = btree_bset_first(b);
	src = dst = i->start;
	while (src != vstruct_last(i)) {
		n = bkey_next_skip_noops(src, vstruct_last(i));
		if (!bkey_deleted(src)) {
			memmove_u64s_down(dst, src, src->u64s);
			dst = bkey_next(dst);
		}
		src = n;
	}

	i->u64s = cpu_to_le16((u64 *) dst - i->_data);
	set_btree_bset_end(b, b->set);

	BUG_ON(b->nsets != 1 ||
	       b->nr.live_u64s != le16_to_cpu(btree_bset_first(b)->u64s));

	btree_node_interior_verify(b);
}

static void btree_split(struct btree_update *as, struct btree *b,
			struct btree_iter *iter, struct keylist *keys,
			unsigned flags)
{
	struct bch_fs *c = as->c;
	struct btree *parent = btree_node_parent(iter, b);
	struct btree *n1, *n2 = NULL, *n3 = NULL;
	u64 start_time = local_clock();

	BUG_ON(!parent && (b != btree_node_root(c, b)));
	BUG_ON(!btree_node_intent_locked(iter, btree_node_root(c, b)->c.level));

	bch2_btree_interior_update_will_free_node(as, b);

	n1 = bch2_btree_node_alloc_replacement(as, b);

	if (keys)
		btree_split_insert_keys(as, n1, iter, keys);

	if (bset_u64s(&n1->set[0]) > BTREE_SPLIT_THRESHOLD(c)) {
		trace_btree_split(c, b);

		n2 = __btree_split_node(as, n1, iter);

		bch2_btree_build_aux_trees(n2);
		bch2_btree_build_aux_trees(n1);
		six_unlock_write(&n2->c.lock);
		six_unlock_write(&n1->c.lock);

		bch2_btree_node_write(c, n2, SIX_LOCK_intent);

		/*
		 * 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, b->c.level + 1);

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

			btree_split_insert_keys(as, n3, iter, &as->parent_keys);

			bch2_btree_node_write(c, n3, SIX_LOCK_intent);
		}
	} else {
		trace_btree_compact(c, b);

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

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

	bch2_open_buckets_put(c, &n1->ob);
	if (n2)
		bch2_open_buckets_put(c, &n2->ob);
	if (n3)
		bch2_open_buckets_put(c, &n3->ob);

	/* Successful split, update the iterator to point to the new nodes: */

	six_lock_increment(&b->c.lock, SIX_LOCK_intent);
	bch2_btree_iter_node_drop(iter, b);
	if (n3)
		bch2_btree_iter_node_replace(iter, n3);
	if (n2)
		bch2_btree_iter_node_replace(iter, n2);
	bch2_btree_iter_node_replace(iter, n1);

	/*
	 * 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(c, b, iter);

	if (n3)
		six_unlock_intent(&n3->c.lock);
	if (n2)
		six_unlock_intent(&n2->c.lock);
	six_unlock_intent(&n1->c.lock);

	bch2_btree_trans_verify_locks(iter->trans);

	bch2_time_stats_update(&c->times[BCH_TIME_btree_node_split],
			       start_time);
}

static void
bch2_btree_insert_keys_interior(struct btree_update *as, struct btree *b,
				struct btree_iter *iter, struct keylist *keys)
{
	struct btree_iter *linked;
	struct btree_node_iter node_iter;
	struct bkey_i *insert = bch2_keylist_front(keys);
	struct bkey_packed *k;

	/* Don't screw up @iter's position: */
	node_iter = iter->l[b->c.level].iter;

	/*
	 * btree_split(), btree_gc_coalesce() will insert keys before
	 * the iterator's current position - they know the keys go in
	 * the node the iterator points to:
	 */
	while ((k = bch2_btree_node_iter_prev_all(&node_iter, b)) &&
	       (bkey_cmp_packed(b, k, &insert->k) >= 0))
		;

	for_each_keylist_key(keys, insert)
		bch2_insert_fixup_btree_ptr(as, b, iter, insert, &node_iter);

	btree_update_updated_node(as, b);

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

	bch2_btree_trans_verify_iters(iter->trans, b);
}

/**
 * bch_btree_insert_node - insert bkeys into a given btree node
 *
 * @iter:		btree iterator
 * @keys:		list of keys to insert
 * @hook:		insert callback
 * @persistent:		if not null, @persistent will wait on journal write
 *
 * 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.
 */
void bch2_btree_insert_node(struct btree_update *as, struct btree *b,
			    struct btree_iter *iter, struct keylist *keys,
			    unsigned flags)
{
	struct bch_fs *c = as->c;
	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;

	BUG_ON(!btree_node_intent_locked(iter, btree_node_root(c, b)->c.level));
	BUG_ON(!b->c.level);
	BUG_ON(!as || as->b);
	bch2_verify_keylist_sorted(keys);

	if (as->must_rewrite)
		goto split;

	bch2_btree_node_lock_for_insert(c, b, iter);

	if (!bch2_btree_node_insert_fits(c, b, bch_keylist_u64s(keys))) {
		bch2_btree_node_unlock_write(b, iter);
		goto split;
	}

	bch2_btree_insert_keys_interior(as, b, iter, 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_btree_iter_reinit_node(iter, b);

	bch2_btree_node_unlock_write(b, iter);

	btree_node_interior_verify(b);

	/*
	 * when called from the btree_split path the new nodes aren't added to
	 * the btree iterator yet, so the merge path's unlock/wait/relock dance
	 * won't work:
	 */
	bch2_foreground_maybe_merge(c, iter, b->c.level,
				    flags|BTREE_INSERT_NOUNLOCK);
	return;
split:
	btree_split(as, b, iter, keys, flags);
}

int bch2_btree_split_leaf(struct bch_fs *c, struct btree_iter *iter,
			  unsigned flags)
{
	struct btree_trans *trans = iter->trans;
	struct btree *b = iter_l(iter)->b;
	struct btree_update *as;
	struct closure cl;
	int ret = 0;
	struct btree_iter *linked;

	/*
	 * We already have a disk reservation and open buckets pinned; this
	 * allocation must not block:
	 */
	trans_for_each_iter(trans, linked)
		if (linked->btree_id == BTREE_ID_EXTENTS)
			flags |= BTREE_INSERT_USE_RESERVE;

	closure_init_stack(&cl);

	/* Hack, because gc and splitting nodes doesn't mix yet: */
	if (!(flags & BTREE_INSERT_GC_LOCK_HELD) &&
	    !down_read_trylock(&c->gc_lock)) {
		if (flags & BTREE_INSERT_NOUNLOCK) {
			trace_transaction_restart_ip(trans->ip, _THIS_IP_);
			return -EINTR;
		}

		bch2_trans_unlock(trans);
		down_read(&c->gc_lock);

		if (!bch2_trans_relock(trans))
			ret = -EINTR;
	}

	/*
	 * XXX: figure out how far we might need to split,
	 * instead of locking/reserving all the way to the root:
	 */
	if (!bch2_btree_iter_upgrade(iter, U8_MAX)) {
		trace_trans_restart_iter_upgrade(trans->ip);
		ret = -EINTR;
		goto out;
	}

	as = bch2_btree_update_start(trans, iter->btree_id,
		btree_update_reserve_required(c, b), flags,
		!(flags & BTREE_INSERT_NOUNLOCK) ? &cl : NULL);
	if (IS_ERR(as)) {
		ret = PTR_ERR(as);
		if (ret == -EAGAIN) {
			BUG_ON(flags & BTREE_INSERT_NOUNLOCK);
			bch2_trans_unlock(trans);
			ret = -EINTR;

			trace_transaction_restart_ip(trans->ip, _THIS_IP_);
		}
		goto out;
	}

	btree_split(as, b, iter, NULL, flags);
	bch2_btree_update_done(as);

	/*
	 * We haven't successfully inserted yet, so don't downgrade all the way
	 * back to read locks;
	 */
	__bch2_btree_iter_downgrade(iter, 1);
out:
	if (!(flags & BTREE_INSERT_GC_LOCK_HELD))
		up_read(&c->gc_lock);
	closure_sync(&cl);
	return ret;
}

void __bch2_foreground_maybe_merge(struct bch_fs *c,
				   struct btree_iter *iter,
				   unsigned level,
				   unsigned flags,
				   enum btree_node_sibling sib)
{
	struct btree_trans *trans = iter->trans;
	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 closure cl;
	size_t sib_u64s;
	int ret = 0;

	BUG_ON(!btree_node_locked(iter, level));

	closure_init_stack(&cl);
retry:
	BUG_ON(!btree_node_locked(iter, level));

	b = iter->l[level].b;

	parent = btree_node_parent(iter, b);
	if (!parent)
		goto out;

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

	/* XXX: can't be holding read locks */
	m = bch2_btree_node_get_sibling(c, iter, b, sib);
	if (IS_ERR(m)) {
		ret = PTR_ERR(m);
		goto err;
	}

	/* NULL means no sibling: */
	if (!m) {
		b->sib_u64s[sib] = U16_MAX;
		goto out;
	}

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

	bch2_bkey_format_init(&new_s);
	__bch2_btree_calc_format(&new_s, b);
	__bch2_btree_calc_format(&new_s, m);
	new_f = bch2_bkey_format_done(&new_s);

	sib_u64s = btree_node_u64s_with_format(b, &new_f) +
		btree_node_u64s_with_format(m, &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));
	b->sib_u64s[sib] = sib_u64s;

	if (b->sib_u64s[sib] > BTREE_FOREGROUND_MERGE_THRESHOLD(c)) {
		six_unlock_intent(&m->c.lock);
		goto out;
	}

	/* We're changing btree topology, doesn't mix with gc: */
	if (!(flags & BTREE_INSERT_GC_LOCK_HELD) &&
	    !down_read_trylock(&c->gc_lock))
		goto err_cycle_gc_lock;

	if (!bch2_btree_iter_upgrade(iter, U8_MAX)) {
		ret = -EINTR;
		goto err_unlock;
	}

	as = bch2_btree_update_start(trans, iter->btree_id,
			 btree_update_reserve_required(c, parent) + 1,
			 flags|
			 BTREE_INSERT_NOFAIL|
			 BTREE_INSERT_USE_RESERVE,
			 !(flags & BTREE_INSERT_NOUNLOCK) ? &cl : NULL);
	if (IS_ERR(as)) {
		ret = PTR_ERR(as);
		goto err_unlock;
	}

	trace_btree_merge(c, 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, b->c.level);

	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);
	six_unlock_write(&n->c.lock);

	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, parent, iter, &as->parent_keys, flags);

	bch2_open_buckets_put(c, &n->ob);

	six_lock_increment(&b->c.lock, SIX_LOCK_intent);
	bch2_btree_iter_node_drop(iter, b);
	bch2_btree_iter_node_drop(iter, m);

	bch2_btree_iter_node_replace(iter, n);

	bch2_btree_trans_verify_iters(trans, n);

	bch2_btree_node_free_inmem(c, b, iter);
	bch2_btree_node_free_inmem(c, m, iter);

	six_unlock_intent(&n->c.lock);

	bch2_btree_update_done(as);

	if (!(flags & BTREE_INSERT_GC_LOCK_HELD))
		up_read(&c->gc_lock);
out:
	bch2_btree_trans_verify_locks(trans);

	/*
	 * Don't downgrade locks here: we're called after successful insert,
	 * and the caller will downgrade locks after a successful insert
	 * anyways (in case e.g. a split was required first)
	 *
	 * And we're also called when inserting into interior nodes in the
	 * split path, and downgrading to read locks in there is potentially
	 * confusing:
	 */
	closure_sync(&cl);
	return;

err_cycle_gc_lock:
	six_unlock_intent(&m->c.lock);

	if (flags & BTREE_INSERT_NOUNLOCK)
		goto out;

	bch2_trans_unlock(trans);

	down_read(&c->gc_lock);
	up_read(&c->gc_lock);
	ret = -EINTR;
	goto err;

err_unlock:
	six_unlock_intent(&m->c.lock);
	if (!(flags & BTREE_INSERT_GC_LOCK_HELD))
		up_read(&c->gc_lock);
err:
	BUG_ON(ret == -EAGAIN && (flags & BTREE_INSERT_NOUNLOCK));

	if ((ret == -EAGAIN || ret == -EINTR) &&
	    !(flags & BTREE_INSERT_NOUNLOCK)) {
		bch2_trans_unlock(trans);
		closure_sync(&cl);
		ret = bch2_btree_iter_traverse(iter);
		if (ret)
			goto out;

		goto retry;
	}

	goto out;
}

static int __btree_node_rewrite(struct bch_fs *c, struct btree_iter *iter,
				struct btree *b, unsigned flags,
				struct closure *cl)
{
	struct btree *n, *parent = btree_node_parent(iter, b);
	struct btree_update *as;

	as = bch2_btree_update_start(iter->trans, iter->btree_id,
		(parent
		 ? btree_update_reserve_required(c, parent)
		 : 0) + 1,
		flags, cl);
	if (IS_ERR(as)) {
		trace_btree_gc_rewrite_node_fail(c, b);
		return PTR_ERR(as);
	}

	bch2_btree_interior_update_will_free_node(as, b);

	n = bch2_btree_node_alloc_replacement(as, b);

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

	trace_btree_gc_rewrite_node(c, b);

	bch2_btree_node_write(c, n, SIX_LOCK_intent);

	if (parent) {
		bch2_keylist_add(&as->parent_keys, &n->key);
		bch2_btree_insert_node(as, parent, iter, &as->parent_keys, flags);
	} else {
		bch2_btree_set_root(as, n, iter);
	}

	bch2_open_buckets_put(c, &n->ob);

	six_lock_increment(&b->c.lock, SIX_LOCK_intent);
	bch2_btree_iter_node_drop(iter, b);
	bch2_btree_iter_node_replace(iter, n);
	bch2_btree_node_free_inmem(c, b, iter);
	six_unlock_intent(&n->c.lock);

	bch2_btree_update_done(as);
	return 0;
}

/**
 * bch_btree_node_rewrite - Rewrite/move a btree node
 *
 * Returns 0 on success, -EINTR or -EAGAIN on failure (i.e.
 * btree_check_reserve() has to wait)
 */
int bch2_btree_node_rewrite(struct bch_fs *c, struct btree_iter *iter,
			    __le64 seq, unsigned flags)
{
	struct btree_trans *trans = iter->trans;
	struct closure cl;
	struct btree *b;
	int ret;

	flags |= BTREE_INSERT_NOFAIL;

	closure_init_stack(&cl);

	bch2_btree_iter_upgrade(iter, U8_MAX);

	if (!(flags & BTREE_INSERT_GC_LOCK_HELD)) {
		if (!down_read_trylock(&c->gc_lock)) {
			bch2_trans_unlock(trans);
			down_read(&c->gc_lock);
		}
	}

	while (1) {
		ret = bch2_btree_iter_traverse(iter);
		if (ret)
			break;

		b = bch2_btree_iter_peek_node(iter);
		if (!b || b->data->keys.seq != seq)
			break;

		ret = __btree_node_rewrite(c, iter, b, flags, &cl);
		if (ret != -EAGAIN &&
		    ret != -EINTR)
			break;

		bch2_trans_unlock(trans);
		closure_sync(&cl);
	}

	bch2_btree_iter_downgrade(iter);

	if (!(flags & BTREE_INSERT_GC_LOCK_HELD))
		up_read(&c->gc_lock);

	closure_sync(&cl);
	return ret;
}

static void __bch2_btree_node_update_key(struct bch_fs *c,
					 struct btree_update *as,
					 struct btree_iter *iter,
					 struct btree *b, struct btree *new_hash,
					 struct bkey_i *new_key)
{
	struct btree *parent;
	int ret;

	/*
	 * Two corner cases that need to be thought about here:
	 *
	 * @b may not be reachable yet - there might be another interior update
	 * operation waiting on @b to be written, and we're gonna deliver the
	 * write completion to that interior update operation _before_
	 * persisting the new_key update
	 *
	 * That ends up working without us having to do anything special here:
	 * the reason is, we do kick off (and do the in memory updates) for the
	 * update for @new_key before we return, creating a new interior_update
	 * operation here.
	 *
	 * The new interior update operation here will in effect override the
	 * previous one. The previous one was going to terminate - make @b
	 * reachable - in one of two ways:
	 * - updating the btree root pointer
	 *   In that case,
	 *   no, this doesn't work. argh.
	 */

	if (b->will_make_reachable)
		as->must_rewrite = true;

	btree_interior_update_add_node_reference(as, b);

	/*
	 * XXX: the rest of the update path treats this like we're actually
	 * inserting a new node and deleting the existing node, so the
	 * reservation needs to include enough space for @b
	 *
	 * that is actually sketch as fuck though and I am surprised the code
	 * seems to work like that, definitely need to go back and rework it
	 * into something saner.
	 *
	 * (I think @b is just getting double counted until the btree update
	 * finishes and "deletes" @b on disk)
	 */
	ret = bch2_disk_reservation_add(c, &as->reserve->disk_res,
			c->opts.btree_node_size *
			bch2_bkey_nr_ptrs(bkey_i_to_s_c(new_key)),
			BCH_DISK_RESERVATION_NOFAIL);
	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);
		}

		bch2_keylist_add(&as->parent_keys, new_key);
		bch2_btree_insert_node(as, parent, iter, &as->parent_keys, 0);

		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);
		}
	} else {
		struct bch_fs_usage_online *fs_usage;

		BUG_ON(btree_node_root(c, b) != b);

		bch2_btree_node_lock_write(b, iter);

		mutex_lock(&c->btree_interior_update_lock);
		percpu_down_read(&c->mark_lock);
		fs_usage = bch2_fs_usage_scratch_get(c);

		bch2_mark_key_locked(c, bkey_i_to_s_c(new_key),
			      0, 0, &fs_usage->u, 0,
			      BTREE_TRIGGER_INSERT);
		if (gc_visited(c, gc_pos_btree_root(b->c.btree_id)))
			bch2_mark_key_locked(c, bkey_i_to_s_c(new_key),
					     0, 0, NULL, 0,
					     BTREE_TRIGGER_INSERT||
					     BTREE_TRIGGER_GC);

		bch2_btree_node_free_index(as, NULL,
					   bkey_i_to_s_c(&b->key),
					   &fs_usage->u);
		bch2_fs_usage_apply(c, fs_usage, &as->reserve->disk_res, 0);

		bch2_fs_usage_scratch_put(c, fs_usage);
		percpu_up_read(&c->mark_lock);
		mutex_unlock(&c->btree_interior_update_lock);

		if (btree_ptr_hash_val(new_key) != b->hash_val) {
			mutex_lock(&c->btree_cache.lock);
			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);
		}

		btree_update_updated_root(as, b);
		bch2_btree_node_unlock_write(b, iter);
	}

	bch2_btree_update_done(as);
}

int bch2_btree_node_update_key(struct bch_fs *c, struct btree_iter *iter,
			       struct btree *b,
			       struct bkey_i *new_key)
{
	struct btree *parent = btree_node_parent(iter, b);
	struct btree_update *as = NULL;
	struct btree *new_hash = NULL;
	struct closure cl;
	int ret;

	closure_init_stack(&cl);

	if (!bch2_btree_iter_upgrade(iter, U8_MAX))
		return -EINTR;

	if (!down_read_trylock(&c->gc_lock)) {
		bch2_trans_unlock(iter->trans);
		down_read(&c->gc_lock);

		if (!bch2_trans_relock(iter->trans)) {
			ret = -EINTR;
			goto err;
		}
	}

	/*
	 * check btree_ptr_hash_val() after @b is locked by
	 * btree_iter_traverse():
	 */
	if (btree_ptr_hash_val(new_key) != b->hash_val) {
		/* bch2_btree_reserve_get will unlock */
		ret = bch2_btree_cache_cannibalize_lock(c, &cl);
		if (ret) {
			bch2_trans_unlock(iter->trans);
			up_read(&c->gc_lock);
			closure_sync(&cl);
			down_read(&c->gc_lock);

			if (!bch2_trans_relock(iter->trans)) {
				ret = -EINTR;
				goto err;
			}
		}

		new_hash = bch2_btree_node_mem_alloc(c);
	}

	as = bch2_btree_update_start(iter->trans, iter->btree_id,
		parent ? btree_update_reserve_required(c, parent) : 0,
		BTREE_INSERT_NOFAIL|
		BTREE_INSERT_USE_RESERVE|
		BTREE_INSERT_USE_ALLOC_RESERVE,
		&cl);

	if (IS_ERR(as)) {
		ret = PTR_ERR(as);
		if (ret == -EAGAIN)
			ret = -EINTR;

		if (ret != -EINTR)
			goto err;

		bch2_trans_unlock(iter->trans);
		up_read(&c->gc_lock);
		closure_sync(&cl);
		down_read(&c->gc_lock);

		if (!bch2_trans_relock(iter->trans))
			goto err;
	}

	ret = bch2_mark_bkey_replicas(c, bkey_i_to_s_c(new_key));
	if (ret)
		goto err_free_update;

	__bch2_btree_node_update_key(c, as, iter, b, new_hash, new_key);

	bch2_btree_iter_downgrade(iter);
err:
	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);
	}
	up_read(&c->gc_lock);
	closure_sync(&cl);
	return ret;
err_free_update:
	bch2_btree_update_free(as);
	goto err;
}

/* 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);
}

void bch2_btree_root_alloc(struct bch_fs *c, enum btree_id id)
{
	struct closure cl;
	struct btree *b;
	int ret;

	closure_init_stack(&cl);

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

	b = bch2_btree_node_mem_alloc(c);
	bch2_btree_cache_cannibalize_unlock(c);

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

	bkey_btree_ptr_init(&b->key);
	b->key.k.p = POS_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, POS_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);
}

ssize_t bch2_btree_updates_print(struct bch_fs *c, char *buf)
{
	struct printbuf out = _PBUF(buf, PAGE_SIZE);
	struct btree_update *as;

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

	return out.pos - buf;
}

size_t bch2_btree_interior_updates_nr_pending(struct bch_fs *c)
{
	size_t ret = 0;
	struct list_head *i;

	mutex_lock(&c->btree_interior_update_lock);
	list_for_each(i, &c->btree_interior_update_list)
		ret++;
	mutex_unlock(&c->btree_interior_update_lock);

	return ret;
}