1 files changed, 1067 insertions, 0 deletions

diff --git a/c_src/libbcachefs/btree_key_cache.c b/c_src/libbcachefs/btree_key_cache.c
new file mode 100644
index 00000000..74e52fd2
--- /dev/null
+++ b/c_src/libbcachefs/btree_key_cache.c
@@ -0,0 +1,1067 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "bcachefs.h"
+#include "btree_cache.h"
+#include "btree_iter.h"
+#include "btree_key_cache.h"
+#include "btree_locking.h"
+#include "btree_update.h"
+#include "errcode.h"
+#include "error.h"
+#include "journal.h"
+#include "journal_reclaim.h"
+#include "trace.h"
+
+#include <linux/sched/mm.h>
+
+static inline bool btree_uses_pcpu_readers(enum btree_id id)
+{
+	return id == BTREE_ID_subvolumes;
+}
+
+static struct kmem_cache *bch2_key_cache;
+
+static int bch2_btree_key_cache_cmp_fn(struct rhashtable_compare_arg *arg,
+				       const void *obj)
+{
+	const struct bkey_cached *ck = obj;
+	const struct bkey_cached_key *key = arg->key;
+
+	return ck->key.btree_id != key->btree_id ||
+		!bpos_eq(ck->key.pos, key->pos);
+}
+
+static const struct rhashtable_params bch2_btree_key_cache_params = {
+	.head_offset	= offsetof(struct bkey_cached, hash),
+	.key_offset	= offsetof(struct bkey_cached, key),
+	.key_len	= sizeof(struct bkey_cached_key),
+	.obj_cmpfn	= bch2_btree_key_cache_cmp_fn,
+};
+
+__flatten
+inline struct bkey_cached *
+bch2_btree_key_cache_find(struct bch_fs *c, enum btree_id btree_id, struct bpos pos)
+{
+	struct bkey_cached_key key = {
+		.btree_id	= btree_id,
+		.pos		= pos,
+	};
+
+	return rhashtable_lookup_fast(&c->btree_key_cache.table, &key,
+				      bch2_btree_key_cache_params);
+}
+
+static bool bkey_cached_lock_for_evict(struct bkey_cached *ck)
+{
+	if (!six_trylock_intent(&ck->c.lock))
+		return false;
+
+	if (test_bit(BKEY_CACHED_DIRTY, &ck->flags)) {
+		six_unlock_intent(&ck->c.lock);
+		return false;
+	}
+
+	if (!six_trylock_write(&ck->c.lock)) {
+		six_unlock_intent(&ck->c.lock);
+		return false;
+	}
+
+	return true;
+}
+
+static void bkey_cached_evict(struct btree_key_cache *c,
+			      struct bkey_cached *ck)
+{
+	BUG_ON(rhashtable_remove_fast(&c->table, &ck->hash,
+				      bch2_btree_key_cache_params));
+	memset(&ck->key, ~0, sizeof(ck->key));
+
+	atomic_long_dec(&c->nr_keys);
+}
+
+static void bkey_cached_free(struct btree_key_cache *bc,
+			     struct bkey_cached *ck)
+{
+	struct bch_fs *c = container_of(bc, struct bch_fs, btree_key_cache);
+
+	BUG_ON(test_bit(BKEY_CACHED_DIRTY, &ck->flags));
+
+	ck->btree_trans_barrier_seq =
+		start_poll_synchronize_srcu(&c->btree_trans_barrier);
+
+	if (ck->c.lock.readers) {
+		list_move_tail(&ck->list, &bc->freed_pcpu);
+		bc->nr_freed_pcpu++;
+	} else {
+		list_move_tail(&ck->list, &bc->freed_nonpcpu);
+		bc->nr_freed_nonpcpu++;
+	}
+	atomic_long_inc(&bc->nr_freed);
+
+	kfree(ck->k);
+	ck->k		= NULL;
+	ck->u64s	= 0;
+
+	six_unlock_write(&ck->c.lock);
+	six_unlock_intent(&ck->c.lock);
+}
+
+#ifdef __KERNEL__
+static void __bkey_cached_move_to_freelist_ordered(struct btree_key_cache *bc,
+						   struct bkey_cached *ck)
+{
+	struct bkey_cached *pos;
+
+	bc->nr_freed_nonpcpu++;
+
+	list_for_each_entry_reverse(pos, &bc->freed_nonpcpu, list) {
+		if (ULONG_CMP_GE(ck->btree_trans_barrier_seq,
+				 pos->btree_trans_barrier_seq)) {
+			list_move(&ck->list, &pos->list);
+			return;
+		}
+	}
+
+	list_move(&ck->list, &bc->freed_nonpcpu);
+}
+#endif
+
+static void bkey_cached_move_to_freelist(struct btree_key_cache *bc,
+					 struct bkey_cached *ck)
+{
+	BUG_ON(test_bit(BKEY_CACHED_DIRTY, &ck->flags));
+
+	if (!ck->c.lock.readers) {
+#ifdef __KERNEL__
+		struct btree_key_cache_freelist *f;
+		bool freed = false;
+
+		preempt_disable();
+		f = this_cpu_ptr(bc->pcpu_freed);
+
+		if (f->nr < ARRAY_SIZE(f->objs)) {
+			f->objs[f->nr++] = ck;
+			freed = true;
+		}
+		preempt_enable();
+
+		if (!freed) {
+			mutex_lock(&bc->lock);
+			preempt_disable();
+			f = this_cpu_ptr(bc->pcpu_freed);
+
+			while (f->nr > ARRAY_SIZE(f->objs) / 2) {
+				struct bkey_cached *ck2 = f->objs[--f->nr];
+
+				__bkey_cached_move_to_freelist_ordered(bc, ck2);
+			}
+			preempt_enable();
+
+			__bkey_cached_move_to_freelist_ordered(bc, ck);
+			mutex_unlock(&bc->lock);
+		}
+#else
+		mutex_lock(&bc->lock);
+		list_move_tail(&ck->list, &bc->freed_nonpcpu);
+		bc->nr_freed_nonpcpu++;
+		mutex_unlock(&bc->lock);
+#endif
+	} else {
+		mutex_lock(&bc->lock);
+		list_move_tail(&ck->list, &bc->freed_pcpu);
+		mutex_unlock(&bc->lock);
+	}
+}
+
+static void bkey_cached_free_fast(struct btree_key_cache *bc,
+				  struct bkey_cached *ck)
+{
+	struct bch_fs *c = container_of(bc, struct bch_fs, btree_key_cache);
+
+	ck->btree_trans_barrier_seq =
+		start_poll_synchronize_srcu(&c->btree_trans_barrier);
+
+	list_del_init(&ck->list);
+	atomic_long_inc(&bc->nr_freed);
+
+	kfree(ck->k);
+	ck->k		= NULL;
+	ck->u64s	= 0;
+
+	bkey_cached_move_to_freelist(bc, ck);
+
+	six_unlock_write(&ck->c.lock);
+	six_unlock_intent(&ck->c.lock);
+}
+
+static struct bkey_cached *
+bkey_cached_alloc(struct btree_trans *trans, struct btree_path *path,
+		  bool *was_new)
+{
+	struct bch_fs *c = trans->c;
+	struct btree_key_cache *bc = &c->btree_key_cache;
+	struct bkey_cached *ck = NULL;
+	bool pcpu_readers = btree_uses_pcpu_readers(path->btree_id);
+	int ret;
+
+	if (!pcpu_readers) {
+#ifdef __KERNEL__
+		struct btree_key_cache_freelist *f;
+
+		preempt_disable();
+		f = this_cpu_ptr(bc->pcpu_freed);
+		if (f->nr)
+			ck = f->objs[--f->nr];
+		preempt_enable();
+
+		if (!ck) {
+			mutex_lock(&bc->lock);
+			preempt_disable();
+			f = this_cpu_ptr(bc->pcpu_freed);
+
+			while (!list_empty(&bc->freed_nonpcpu) &&
+			       f->nr < ARRAY_SIZE(f->objs) / 2) {
+				ck = list_last_entry(&bc->freed_nonpcpu, struct bkey_cached, list);
+				list_del_init(&ck->list);
+				bc->nr_freed_nonpcpu--;
+				f->objs[f->nr++] = ck;
+			}
+
+			ck = f->nr ? f->objs[--f->nr] : NULL;
+			preempt_enable();
+			mutex_unlock(&bc->lock);
+		}
+#else
+		mutex_lock(&bc->lock);
+		if (!list_empty(&bc->freed_nonpcpu)) {
+			ck = list_last_entry(&bc->freed_nonpcpu, struct bkey_cached, list);
+			list_del_init(&ck->list);
+			bc->nr_freed_nonpcpu--;
+		}
+		mutex_unlock(&bc->lock);
+#endif
+	} else {
+		mutex_lock(&bc->lock);
+		if (!list_empty(&bc->freed_pcpu)) {
+			ck = list_last_entry(&bc->freed_pcpu, struct bkey_cached, list);
+			list_del_init(&ck->list);
+		}
+		mutex_unlock(&bc->lock);
+	}
+
+	if (ck) {
+		ret = btree_node_lock_nopath(trans, &ck->c, SIX_LOCK_intent, _THIS_IP_);
+		if (unlikely(ret)) {
+			bkey_cached_move_to_freelist(bc, ck);
+			return ERR_PTR(ret);
+		}
+
+		path->l[0].b = (void *) ck;
+		path->l[0].lock_seq = six_lock_seq(&ck->c.lock);
+		mark_btree_node_locked(trans, path, 0, BTREE_NODE_INTENT_LOCKED);
+
+		ret = bch2_btree_node_lock_write(trans, path, &ck->c);
+		if (unlikely(ret)) {
+			btree_node_unlock(trans, path, 0);
+			bkey_cached_move_to_freelist(bc, ck);
+			return ERR_PTR(ret);
+		}
+
+		return ck;
+	}
+
+	ck = allocate_dropping_locks(trans, ret,
+			kmem_cache_zalloc(bch2_key_cache, _gfp));
+	if (ret) {
+		kmem_cache_free(bch2_key_cache, ck);
+		return ERR_PTR(ret);
+	}
+
+	if (!ck)
+		return NULL;
+
+	INIT_LIST_HEAD(&ck->list);
+	bch2_btree_lock_init(&ck->c, pcpu_readers ? SIX_LOCK_INIT_PCPU : 0);
+
+	ck->c.cached = true;
+	BUG_ON(!six_trylock_intent(&ck->c.lock));
+	BUG_ON(!six_trylock_write(&ck->c.lock));
+	*was_new = true;
+	return ck;
+}
+
+static struct bkey_cached *
+bkey_cached_reuse(struct btree_key_cache *c)
+{
+	struct bucket_table *tbl;
+	struct rhash_head *pos;
+	struct bkey_cached *ck;
+	unsigned i;
+
+	mutex_lock(&c->lock);
+	rcu_read_lock();
+	tbl = rht_dereference_rcu(c->table.tbl, &c->table);
+	for (i = 0; i < tbl->size; i++)
+		rht_for_each_entry_rcu(ck, pos, tbl, i, hash) {
+			if (!test_bit(BKEY_CACHED_DIRTY, &ck->flags) &&
+			    bkey_cached_lock_for_evict(ck)) {
+				bkey_cached_evict(c, ck);
+				goto out;
+			}
+		}
+	ck = NULL;
+out:
+	rcu_read_unlock();
+	mutex_unlock(&c->lock);
+	return ck;
+}
+
+static struct bkey_cached *
+btree_key_cache_create(struct btree_trans *trans, struct btree_path *path)
+{
+	struct bch_fs *c = trans->c;
+	struct btree_key_cache *bc = &c->btree_key_cache;
+	struct bkey_cached *ck;
+	bool was_new = false;
+
+	ck = bkey_cached_alloc(trans, path, &was_new);
+	if (IS_ERR(ck))
+		return ck;
+
+	if (unlikely(!ck)) {
+		ck = bkey_cached_reuse(bc);
+		if (unlikely(!ck)) {
+			bch_err(c, "error allocating memory for key cache item, btree %s",
+				bch2_btree_id_str(path->btree_id));
+			return ERR_PTR(-BCH_ERR_ENOMEM_btree_key_cache_create);
+		}
+
+		mark_btree_node_locked(trans, path, 0, BTREE_NODE_INTENT_LOCKED);
+	}
+
+	ck->c.level		= 0;
+	ck->c.btree_id		= path->btree_id;
+	ck->key.btree_id	= path->btree_id;
+	ck->key.pos		= path->pos;
+	ck->valid		= false;
+	ck->flags		= 1U << BKEY_CACHED_ACCESSED;
+
+	if (unlikely(rhashtable_lookup_insert_fast(&bc->table,
+					  &ck->hash,
+					  bch2_btree_key_cache_params))) {
+		/* We raced with another fill: */
+
+		if (likely(was_new)) {
+			six_unlock_write(&ck->c.lock);
+			six_unlock_intent(&ck->c.lock);
+			kfree(ck);
+		} else {
+			bkey_cached_free_fast(bc, ck);
+		}
+
+		mark_btree_node_locked(trans, path, 0, BTREE_NODE_UNLOCKED);
+		return NULL;
+	}
+
+	atomic_long_inc(&bc->nr_keys);
+
+	six_unlock_write(&ck->c.lock);
+
+	return ck;
+}
+
+static int btree_key_cache_fill(struct btree_trans *trans,
+				struct btree_path *ck_path,
+				struct bkey_cached *ck)
+{
+	struct btree_iter iter;
+	struct bkey_s_c k;
+	unsigned new_u64s = 0;
+	struct bkey_i *new_k = NULL;
+	int ret;
+
+	k = bch2_bkey_get_iter(trans, &iter, ck->key.btree_id, ck->key.pos,
+			       BTREE_ITER_KEY_CACHE_FILL|
+			       BTREE_ITER_CACHED_NOFILL);
+	ret = bkey_err(k);
+	if (ret)
+		goto err;
+
+	if (!bch2_btree_node_relock(trans, ck_path, 0)) {
+		trace_and_count(trans->c, trans_restart_relock_key_cache_fill, trans, _THIS_IP_, ck_path);
+		ret = btree_trans_restart(trans, BCH_ERR_transaction_restart_key_cache_fill);
+		goto err;
+	}
+
+	/*
+	 * bch2_varint_decode can read past the end of the buffer by at
+	 * most 7 bytes (it won't be used):
+	 */
+	new_u64s = k.k->u64s + 1;
+
+	/*
+	 * Allocate some extra space so that the transaction commit path is less
+	 * likely to have to reallocate, since that requires a transaction
+	 * restart:
+	 */
+	new_u64s = min(256U, (new_u64s * 3) / 2);
+
+	if (new_u64s > ck->u64s) {
+		new_u64s = roundup_pow_of_two(new_u64s);
+		new_k = kmalloc(new_u64s * sizeof(u64), GFP_NOWAIT|__GFP_NOWARN);
+		if (!new_k) {
+			bch2_trans_unlock(trans);
+
+			new_k = kmalloc(new_u64s * sizeof(u64), GFP_KERNEL);
+			if (!new_k) {
+				bch_err(trans->c, "error allocating memory for key cache key, btree %s u64s %u",
+					bch2_btree_id_str(ck->key.btree_id), new_u64s);
+				ret = -BCH_ERR_ENOMEM_btree_key_cache_fill;
+				goto err;
+			}
+
+			if (!bch2_btree_node_relock(trans, ck_path, 0)) {
+				kfree(new_k);
+				trace_and_count(trans->c, trans_restart_relock_key_cache_fill, trans, _THIS_IP_, ck_path);
+				ret = btree_trans_restart(trans, BCH_ERR_transaction_restart_key_cache_fill);
+				goto err;
+			}
+
+			ret = bch2_trans_relock(trans);
+			if (ret) {
+				kfree(new_k);
+				goto err;
+			}
+		}
+	}
+
+	ret = bch2_btree_node_lock_write(trans, ck_path, &ck_path->l[0].b->c);
+	if (ret) {
+		kfree(new_k);
+		goto err;
+	}
+
+	if (new_k) {
+		kfree(ck->k);
+		ck->u64s = new_u64s;
+		ck->k = new_k;
+	}
+
+	bkey_reassemble(ck->k, k);
+	ck->valid = true;
+	bch2_btree_node_unlock_write(trans, ck_path, ck_path->l[0].b);
+
+	/* We're not likely to need this iterator again: */
+	set_btree_iter_dontneed(&iter);
+err:
+	bch2_trans_iter_exit(trans, &iter);
+	return ret;
+}
+
+static noinline int
+bch2_btree_path_traverse_cached_slowpath(struct btree_trans *trans, struct btree_path *path,
+					 unsigned flags)
+{
+	struct bch_fs *c = trans->c;
+	struct bkey_cached *ck;
+	int ret = 0;
+
+	BUG_ON(path->level);
+
+	path->l[1].b = NULL;
+
+	if (bch2_btree_node_relock_notrace(trans, path, 0)) {
+		ck = (void *) path->l[0].b;
+		goto fill;
+	}
+retry:
+	ck = bch2_btree_key_cache_find(c, path->btree_id, path->pos);
+	if (!ck) {
+		ck = btree_key_cache_create(trans, path);
+		ret = PTR_ERR_OR_ZERO(ck);
+		if (ret)
+			goto err;
+		if (!ck)
+			goto retry;
+
+		mark_btree_node_locked(trans, path, 0, BTREE_NODE_INTENT_LOCKED);
+		path->locks_want = 1;
+	} else {
+		enum six_lock_type lock_want = __btree_lock_want(path, 0);
+
+		ret = btree_node_lock(trans, path, (void *) ck, 0,
+				      lock_want, _THIS_IP_);
+		if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
+			goto err;
+
+		BUG_ON(ret);
+
+		if (ck->key.btree_id != path->btree_id ||
+		    !bpos_eq(ck->key.pos, path->pos)) {
+			six_unlock_type(&ck->c.lock, lock_want);
+			goto retry;
+		}
+
+		mark_btree_node_locked(trans, path, 0,
+				       (enum btree_node_locked_type) lock_want);
+	}
+
+	path->l[0].lock_seq	= six_lock_seq(&ck->c.lock);
+	path->l[0].b		= (void *) ck;
+fill:
+	path->uptodate = BTREE_ITER_UPTODATE;
+
+	if (!ck->valid && !(flags & BTREE_ITER_CACHED_NOFILL)) {
+		/*
+		 * Using the underscore version because we haven't set
+		 * path->uptodate yet:
+		 */
+		if (!path->locks_want &&
+		    !__bch2_btree_path_upgrade(trans, path, 1, NULL)) {
+			trace_and_count(trans->c, trans_restart_key_cache_upgrade, trans, _THIS_IP_);
+			ret = btree_trans_restart(trans, BCH_ERR_transaction_restart_key_cache_upgrade);
+			goto err;
+		}
+
+		ret = btree_key_cache_fill(trans, path, ck);
+		if (ret)
+			goto err;
+
+		ret = bch2_btree_path_relock(trans, path, _THIS_IP_);
+		if (ret)
+			goto err;
+
+		path->uptodate = BTREE_ITER_UPTODATE;
+	}
+
+	if (!test_bit(BKEY_CACHED_ACCESSED, &ck->flags))
+		set_bit(BKEY_CACHED_ACCESSED, &ck->flags);
+
+	BUG_ON(btree_node_locked_type(path, 0) != btree_lock_want(path, 0));
+	BUG_ON(path->uptodate);
+
+	return ret;
+err:
+	path->uptodate = BTREE_ITER_NEED_TRAVERSE;
+	if (!bch2_err_matches(ret, BCH_ERR_transaction_restart)) {
+		btree_node_unlock(trans, path, 0);
+		path->l[0].b = ERR_PTR(ret);
+	}
+	return ret;
+}
+
+int bch2_btree_path_traverse_cached(struct btree_trans *trans, struct btree_path *path,
+				    unsigned flags)
+{
+	struct bch_fs *c = trans->c;
+	struct bkey_cached *ck;
+	int ret = 0;
+
+	EBUG_ON(path->level);
+
+	path->l[1].b = NULL;
+
+	if (bch2_btree_node_relock_notrace(trans, path, 0)) {
+		ck = (void *) path->l[0].b;
+		goto fill;
+	}
+retry:
+	ck = bch2_btree_key_cache_find(c, path->btree_id, path->pos);
+	if (!ck) {
+		return bch2_btree_path_traverse_cached_slowpath(trans, path, flags);
+	} else {
+		enum six_lock_type lock_want = __btree_lock_want(path, 0);
+
+		ret = btree_node_lock(trans, path, (void *) ck, 0,
+				      lock_want, _THIS_IP_);
+		EBUG_ON(ret && !bch2_err_matches(ret, BCH_ERR_transaction_restart));
+
+		if (ret)
+			return ret;
+
+		if (ck->key.btree_id != path->btree_id ||
+		    !bpos_eq(ck->key.pos, path->pos)) {
+			six_unlock_type(&ck->c.lock, lock_want);
+			goto retry;
+		}
+
+		mark_btree_node_locked(trans, path, 0,
+				       (enum btree_node_locked_type) lock_want);
+	}
+
+	path->l[0].lock_seq	= six_lock_seq(&ck->c.lock);
+	path->l[0].b		= (void *) ck;
+fill:
+	if (!ck->valid)
+		return bch2_btree_path_traverse_cached_slowpath(trans, path, flags);
+
+	if (!test_bit(BKEY_CACHED_ACCESSED, &ck->flags))
+		set_bit(BKEY_CACHED_ACCESSED, &ck->flags);
+
+	path->uptodate = BTREE_ITER_UPTODATE;
+	EBUG_ON(!ck->valid);
+	EBUG_ON(btree_node_locked_type(path, 0) != btree_lock_want(path, 0));
+
+	return ret;
+}
+
+static int btree_key_cache_flush_pos(struct btree_trans *trans,
+				     struct bkey_cached_key key,
+				     u64 journal_seq,
+				     unsigned commit_flags,
+				     bool evict)
+{
+	struct bch_fs *c = trans->c;
+	struct journal *j = &c->journal;
+	struct btree_iter c_iter, b_iter;
+	struct bkey_cached *ck = NULL;
+	int ret;
+
+	bch2_trans_iter_init(trans, &b_iter, key.btree_id, key.pos,
+			     BTREE_ITER_SLOTS|
+			     BTREE_ITER_INTENT|
+			     BTREE_ITER_ALL_SNAPSHOTS);
+	bch2_trans_iter_init(trans, &c_iter, key.btree_id, key.pos,
+			     BTREE_ITER_CACHED|
+			     BTREE_ITER_INTENT);
+	b_iter.flags &= ~BTREE_ITER_WITH_KEY_CACHE;
+
+	ret = bch2_btree_iter_traverse(&c_iter);
+	if (ret)
+		goto out;
+
+	ck = (void *) btree_iter_path(trans, &c_iter)->l[0].b;
+	if (!ck)
+		goto out;
+
+	if (!test_bit(BKEY_CACHED_DIRTY, &ck->flags)) {
+		if (evict)
+			goto evict;
+		goto out;
+	}
+
+	BUG_ON(!ck->valid);
+
+	if (journal_seq && ck->journal.seq != journal_seq)
+		goto out;
+
+	trans->journal_res.seq = ck->journal.seq;
+
+	/*
+	 * If we're at the end of the journal, we really want to free up space
+	 * in the journal right away - we don't want to pin that old journal
+	 * sequence number with a new btree node write, we want to re-journal
+	 * the update
+	 */
+	if (ck->journal.seq == journal_last_seq(j))
+		commit_flags |= BCH_WATERMARK_reclaim;
+
+	if (ck->journal.seq != journal_last_seq(j) ||
+	    j->watermark == BCH_WATERMARK_stripe)
+		commit_flags |= BCH_TRANS_COMMIT_no_journal_res;
+
+	ret   = bch2_btree_iter_traverse(&b_iter) ?:
+		bch2_trans_update(trans, &b_iter, ck->k,
+				  BTREE_UPDATE_KEY_CACHE_RECLAIM|
+				  BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE|
+				  BTREE_TRIGGER_NORUN) ?:
+		bch2_trans_commit(trans, NULL, NULL,
+				  BCH_TRANS_COMMIT_no_check_rw|
+				  BCH_TRANS_COMMIT_no_enospc|
+				  commit_flags);
+
+	bch2_fs_fatal_err_on(ret &&
+			     !bch2_err_matches(ret, BCH_ERR_transaction_restart) &&
+			     !bch2_err_matches(ret, BCH_ERR_journal_reclaim_would_deadlock) &&
+			     !bch2_journal_error(j), c,
+			     "error flushing key cache: %s", bch2_err_str(ret));
+	if (ret)
+		goto out;
+
+	bch2_journal_pin_drop(j, &ck->journal);
+
+	struct btree_path *path = btree_iter_path(trans, &c_iter);
+	BUG_ON(!btree_node_locked(path, 0));
+
+	if (!evict) {
+		if (test_bit(BKEY_CACHED_DIRTY, &ck->flags)) {
+			clear_bit(BKEY_CACHED_DIRTY, &ck->flags);
+			atomic_long_dec(&c->btree_key_cache.nr_dirty);
+		}
+	} else {
+		struct btree_path *path2;
+		unsigned i;
+evict:
+		trans_for_each_path(trans, path2, i)
+			if (path2 != path)
+				__bch2_btree_path_unlock(trans, path2);
+
+		bch2_btree_node_lock_write_nofail(trans, path, &ck->c);
+
+		if (test_bit(BKEY_CACHED_DIRTY, &ck->flags)) {
+			clear_bit(BKEY_CACHED_DIRTY, &ck->flags);
+			atomic_long_dec(&c->btree_key_cache.nr_dirty);
+		}
+
+		mark_btree_node_locked_noreset(path, 0, BTREE_NODE_UNLOCKED);
+		bkey_cached_evict(&c->btree_key_cache, ck);
+		bkey_cached_free_fast(&c->btree_key_cache, ck);
+	}
+out:
+	bch2_trans_iter_exit(trans, &b_iter);
+	bch2_trans_iter_exit(trans, &c_iter);
+	return ret;
+}
+
+int bch2_btree_key_cache_journal_flush(struct journal *j,
+				struct journal_entry_pin *pin, u64 seq)
+{
+	struct bch_fs *c = container_of(j, struct bch_fs, journal);
+	struct bkey_cached *ck =
+		container_of(pin, struct bkey_cached, journal);
+	struct bkey_cached_key key;
+	struct btree_trans *trans = bch2_trans_get(c);
+	int srcu_idx = srcu_read_lock(&c->btree_trans_barrier);
+	int ret = 0;
+
+	btree_node_lock_nopath_nofail(trans, &ck->c, SIX_LOCK_read);
+	key = ck->key;
+
+	if (ck->journal.seq != seq ||
+	    !test_bit(BKEY_CACHED_DIRTY, &ck->flags)) {
+		six_unlock_read(&ck->c.lock);
+		goto unlock;
+	}
+
+	if (ck->seq != seq) {
+		bch2_journal_pin_update(&c->journal, ck->seq, &ck->journal,
+					bch2_btree_key_cache_journal_flush);
+		six_unlock_read(&ck->c.lock);
+		goto unlock;
+	}
+	six_unlock_read(&ck->c.lock);
+
+	ret = lockrestart_do(trans,
+		btree_key_cache_flush_pos(trans, key, seq,
+				BCH_TRANS_COMMIT_journal_reclaim, false));
+unlock:
+	srcu_read_unlock(&c->btree_trans_barrier, srcu_idx);
+
+	bch2_trans_put(trans);
+	return ret;
+}
+
+bool bch2_btree_insert_key_cached(struct btree_trans *trans,
+				  unsigned flags,
+				  struct btree_insert_entry *insert_entry)
+{
+	struct bch_fs *c = trans->c;
+	struct bkey_cached *ck = (void *) (trans->paths + insert_entry->path)->l[0].b;
+	struct bkey_i *insert = insert_entry->k;
+	bool kick_reclaim = false;
+
+	BUG_ON(insert->k.u64s > ck->u64s);
+
+	bkey_copy(ck->k, insert);
+	ck->valid = true;
+
+	if (!test_bit(BKEY_CACHED_DIRTY, &ck->flags)) {
+		EBUG_ON(test_bit(BCH_FS_clean_shutdown, &c->flags));
+		set_bit(BKEY_CACHED_DIRTY, &ck->flags);
+		atomic_long_inc(&c->btree_key_cache.nr_dirty);
+
+		if (bch2_nr_btree_keys_need_flush(c))
+			kick_reclaim = true;
+	}
+
+	/*
+	 * To minimize lock contention, we only add the journal pin here and
+	 * defer pin updates to the flush callback via ->seq. Be careful not to
+	 * update ->seq on nojournal commits because we don't want to update the
+	 * pin to a seq that doesn't include journal updates on disk. Otherwise
+	 * we risk losing the update after a crash.
+	 *
+	 * The only exception is if the pin is not active in the first place. We
+	 * have to add the pin because journal reclaim drives key cache
+	 * flushing. The flush callback will not proceed unless ->seq matches
+	 * the latest pin, so make sure it starts with a consistent value.
+	 */
+	if (!(insert_entry->flags & BTREE_UPDATE_NOJOURNAL) ||
+	    !journal_pin_active(&ck->journal)) {
+		ck->seq = trans->journal_res.seq;
+	}
+	bch2_journal_pin_add(&c->journal, trans->journal_res.seq,
+			     &ck->journal, bch2_btree_key_cache_journal_flush);
+
+	if (kick_reclaim)
+		journal_reclaim_kick(&c->journal);
+	return true;
+}
+
+void bch2_btree_key_cache_drop(struct btree_trans *trans,
+			       struct btree_path *path)
+{
+	struct bch_fs *c = trans->c;
+	struct bkey_cached *ck = (void *) path->l[0].b;
+
+	BUG_ON(!ck->valid);
+
+	/*
+	 * We just did an update to the btree, bypassing the key cache: the key
+	 * cache key is now stale and must be dropped, even if dirty:
+	 */
+	if (test_bit(BKEY_CACHED_DIRTY, &ck->flags)) {
+		clear_bit(BKEY_CACHED_DIRTY, &ck->flags);
+		atomic_long_dec(&c->btree_key_cache.nr_dirty);
+		bch2_journal_pin_drop(&c->journal, &ck->journal);
+	}
+
+	ck->valid = false;
+}
+
+static unsigned long bch2_btree_key_cache_scan(struct shrinker *shrink,
+					   struct shrink_control *sc)
+{
+	struct bch_fs *c = shrink->private_data;
+	struct btree_key_cache *bc = &c->btree_key_cache;
+	struct bucket_table *tbl;
+	struct bkey_cached *ck, *t;
+	size_t scanned = 0, freed = 0, nr = sc->nr_to_scan;
+	unsigned start, flags;
+	int srcu_idx;
+
+	mutex_lock(&bc->lock);
+	srcu_idx = srcu_read_lock(&c->btree_trans_barrier);
+	flags = memalloc_nofs_save();
+
+	/*
+	 * Newest freed entries are at the end of the list - once we hit one
+	 * that's too new to be freed, we can bail out:
+	 */
+	scanned += bc->nr_freed_nonpcpu;
+
+	list_for_each_entry_safe(ck, t, &bc->freed_nonpcpu, list) {
+		if (!poll_state_synchronize_srcu(&c->btree_trans_barrier,
+						 ck->btree_trans_barrier_seq))
+			break;
+
+		list_del(&ck->list);
+		six_lock_exit(&ck->c.lock);
+		kmem_cache_free(bch2_key_cache, ck);
+		atomic_long_dec(&bc->nr_freed);
+		freed++;
+		bc->nr_freed_nonpcpu--;
+	}
+
+	if (scanned >= nr)
+		goto out;
+
+	scanned += bc->nr_freed_pcpu;
+
+	list_for_each_entry_safe(ck, t, &bc->freed_pcpu, list) {
+		if (!poll_state_synchronize_srcu(&c->btree_trans_barrier,
+						 ck->btree_trans_barrier_seq))
+			break;
+
+		list_del(&ck->list);
+		six_lock_exit(&ck->c.lock);
+		kmem_cache_free(bch2_key_cache, ck);
+		atomic_long_dec(&bc->nr_freed);
+		freed++;
+		bc->nr_freed_pcpu--;
+	}
+
+	if (scanned >= nr)
+		goto out;
+
+	rcu_read_lock();
+	tbl = rht_dereference_rcu(bc->table.tbl, &bc->table);
+	if (bc->shrink_iter >= tbl->size)
+		bc->shrink_iter = 0;
+	start = bc->shrink_iter;
+
+	do {
+		struct rhash_head *pos, *next;
+
+		pos = rht_ptr_rcu(rht_bucket(tbl, bc->shrink_iter));
+
+		while (!rht_is_a_nulls(pos)) {
+			next = rht_dereference_bucket_rcu(pos->next, tbl, bc->shrink_iter);
+			ck = container_of(pos, struct bkey_cached, hash);
+
+			if (test_bit(BKEY_CACHED_DIRTY, &ck->flags))
+				goto next;
+
+			if (test_bit(BKEY_CACHED_ACCESSED, &ck->flags))
+				clear_bit(BKEY_CACHED_ACCESSED, &ck->flags);
+			else if (bkey_cached_lock_for_evict(ck)) {
+				bkey_cached_evict(bc, ck);
+				bkey_cached_free(bc, ck);
+			}
+
+			scanned++;
+			if (scanned >= nr)
+				break;
+next:
+			pos = next;
+		}
+
+		bc->shrink_iter++;
+		if (bc->shrink_iter >= tbl->size)
+			bc->shrink_iter = 0;
+	} while (scanned < nr && bc->shrink_iter != start);
+
+	rcu_read_unlock();
+out:
+	memalloc_nofs_restore(flags);
+	srcu_read_unlock(&c->btree_trans_barrier, srcu_idx);
+	mutex_unlock(&bc->lock);
+
+	return freed;
+}
+
+static unsigned long bch2_btree_key_cache_count(struct shrinker *shrink,
+					    struct shrink_control *sc)
+{
+	struct bch_fs *c = shrink->private_data;
+	struct btree_key_cache *bc = &c->btree_key_cache;
+	long nr = atomic_long_read(&bc->nr_keys) -
+		atomic_long_read(&bc->nr_dirty);
+
+	return max(0L, nr);
+}
+
+void bch2_fs_btree_key_cache_exit(struct btree_key_cache *bc)
+{
+	struct bch_fs *c = container_of(bc, struct bch_fs, btree_key_cache);
+	struct bucket_table *tbl;
+	struct bkey_cached *ck, *n;
+	struct rhash_head *pos;
+	LIST_HEAD(items);
+	unsigned i;
+#ifdef __KERNEL__
+	int cpu;
+#endif
+
+	shrinker_free(bc->shrink);
+
+	mutex_lock(&bc->lock);
+
+	/*
+	 * The loop is needed to guard against racing with rehash:
+	 */
+	while (atomic_long_read(&bc->nr_keys)) {
+		rcu_read_lock();
+		tbl = rht_dereference_rcu(bc->table.tbl, &bc->table);
+		if (tbl)
+			for (i = 0; i < tbl->size; i++)
+				rht_for_each_entry_rcu(ck, pos, tbl, i, hash) {
+					bkey_cached_evict(bc, ck);
+					list_add(&ck->list, &items);
+				}
+		rcu_read_unlock();
+	}
+
+#ifdef __KERNEL__
+	for_each_possible_cpu(cpu) {
+		struct btree_key_cache_freelist *f =
+			per_cpu_ptr(bc->pcpu_freed, cpu);
+
+		for (i = 0; i < f->nr; i++) {
+			ck = f->objs[i];
+			list_add(&ck->list, &items);
+		}
+	}
+#endif
+
+	BUG_ON(list_count_nodes(&bc->freed_pcpu) != bc->nr_freed_pcpu);
+	BUG_ON(list_count_nodes(&bc->freed_nonpcpu) != bc->nr_freed_nonpcpu);
+
+	list_splice(&bc->freed_pcpu,	&items);
+	list_splice(&bc->freed_nonpcpu,	&items);
+
+	mutex_unlock(&bc->lock);
+
+	list_for_each_entry_safe(ck, n, &items, list) {
+		cond_resched();
+
+		list_del(&ck->list);
+		kfree(ck->k);
+		six_lock_exit(&ck->c.lock);
+		kmem_cache_free(bch2_key_cache, ck);
+	}
+
+	if (atomic_long_read(&bc->nr_dirty) &&
+	    !bch2_journal_error(&c->journal) &&
+	    test_bit(BCH_FS_was_rw, &c->flags))
+		panic("btree key cache shutdown error: nr_dirty nonzero (%li)\n",
+		      atomic_long_read(&bc->nr_dirty));
+
+	if (atomic_long_read(&bc->nr_keys))
+		panic("btree key cache shutdown error: nr_keys nonzero (%li)\n",
+		      atomic_long_read(&bc->nr_keys));
+
+	if (bc->table_init_done)
+		rhashtable_destroy(&bc->table);
+
+	free_percpu(bc->pcpu_freed);
+}
+
+void bch2_fs_btree_key_cache_init_early(struct btree_key_cache *c)
+{
+	mutex_init(&c->lock);
+	INIT_LIST_HEAD(&c->freed_pcpu);
+	INIT_LIST_HEAD(&c->freed_nonpcpu);
+}
+
+int bch2_fs_btree_key_cache_init(struct btree_key_cache *bc)
+{
+	struct bch_fs *c = container_of(bc, struct bch_fs, btree_key_cache);
+	struct shrinker *shrink;
+
+#ifdef __KERNEL__
+	bc->pcpu_freed = alloc_percpu(struct btree_key_cache_freelist);
+	if (!bc->pcpu_freed)
+		return -BCH_ERR_ENOMEM_fs_btree_cache_init;
+#endif
+
+	if (rhashtable_init(&bc->table, &bch2_btree_key_cache_params))
+		return -BCH_ERR_ENOMEM_fs_btree_cache_init;
+
+	bc->table_init_done = true;
+
+	shrink = shrinker_alloc(0, "%s-btree_key_cache", c->name);
+	if (!shrink)
+		return -BCH_ERR_ENOMEM_fs_btree_cache_init;
+	bc->shrink = shrink;
+	shrink->seeks		= 0;
+	shrink->count_objects	= bch2_btree_key_cache_count;
+	shrink->scan_objects	= bch2_btree_key_cache_scan;
+	shrink->private_data	= c;
+	shrinker_register(shrink);
+	return 0;
+}
+
+void bch2_btree_key_cache_to_text(struct printbuf *out, struct btree_key_cache *c)
+{
+	prt_printf(out, "nr_freed:\t%lu",	atomic_long_read(&c->nr_freed));
+	prt_newline(out);
+	prt_printf(out, "nr_keys:\t%lu",	atomic_long_read(&c->nr_keys));
+	prt_newline(out);
+	prt_printf(out, "nr_dirty:\t%lu",	atomic_long_read(&c->nr_dirty));
+	prt_newline(out);
+}
+
+void bch2_btree_key_cache_exit(void)
+{
+	kmem_cache_destroy(bch2_key_cache);
+}
+
+int __init bch2_btree_key_cache_init(void)
+{
+	bch2_key_cache = KMEM_CACHE(bkey_cached, SLAB_RECLAIM_ACCOUNT);
+	if (!bch2_key_cache)
+		return -ENOMEM;
+
+	return 0;
+}