Adding upstream version 6.7.7.upstream/6.7.7

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1215 insertions, 0 deletions

diff --git a/fs/bcachefs/btree_cache.c b/fs/bcachefs/btree_cache.c
new file mode 100644
index 0000000000..79495cd7a7
--- /dev/null
+++ b/fs/bcachefs/btree_cache.c
@@ -0,0 +1,1215 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "bcachefs.h"
+#include "bkey_buf.h"
+#include "btree_cache.h"
+#include "btree_io.h"
+#include "btree_iter.h"
+#include "btree_locking.h"
+#include "debug.h"
+#include "errcode.h"
+#include "error.h"
+#include "journal.h"
+#include "trace.h"
+
+#include <linux/prefetch.h>
+#include <linux/sched/mm.h>
+
+const char * const bch2_btree_node_flags[] = {
+#define x(f)	#f,
+	BTREE_FLAGS()
+#undef x
+	NULL
+};
+
+void bch2_recalc_btree_reserve(struct bch_fs *c)
+{
+	unsigned i, reserve = 16;
+
+	if (!c->btree_roots_known[0].b)
+		reserve += 8;
+
+	for (i = 0; i < btree_id_nr_alive(c); i++) {
+		struct btree_root *r = bch2_btree_id_root(c, i);
+
+		if (r->b)
+			reserve += min_t(unsigned, 1, r->b->c.level) * 8;
+	}
+
+	c->btree_cache.reserve = reserve;
+}
+
+static inline unsigned btree_cache_can_free(struct btree_cache *bc)
+{
+	return max_t(int, 0, bc->used - bc->reserve);
+}
+
+static void btree_node_to_freedlist(struct btree_cache *bc, struct btree *b)
+{
+	if (b->c.lock.readers)
+		list_move(&b->list, &bc->freed_pcpu);
+	else
+		list_move(&b->list, &bc->freed_nonpcpu);
+}
+
+static void btree_node_data_free(struct bch_fs *c, struct btree *b)
+{
+	struct btree_cache *bc = &c->btree_cache;
+
+	EBUG_ON(btree_node_write_in_flight(b));
+
+	clear_btree_node_just_written(b);
+
+	kvpfree(b->data, btree_bytes(c));
+	b->data = NULL;
+#ifdef __KERNEL__
+	kvfree(b->aux_data);
+#else
+	munmap(b->aux_data, btree_aux_data_bytes(b));
+#endif
+	b->aux_data = NULL;
+
+	bc->used--;
+
+	btree_node_to_freedlist(bc, b);
+}
+
+static int bch2_btree_cache_cmp_fn(struct rhashtable_compare_arg *arg,
+				   const void *obj)
+{
+	const struct btree *b = obj;
+	const u64 *v = arg->key;
+
+	return b->hash_val == *v ? 0 : 1;
+}
+
+static const struct rhashtable_params bch_btree_cache_params = {
+	.head_offset	= offsetof(struct btree, hash),
+	.key_offset	= offsetof(struct btree, hash_val),
+	.key_len	= sizeof(u64),
+	.obj_cmpfn	= bch2_btree_cache_cmp_fn,
+};
+
+static int btree_node_data_alloc(struct bch_fs *c, struct btree *b, gfp_t gfp)
+{
+	BUG_ON(b->data || b->aux_data);
+
+	b->data = kvpmalloc(btree_bytes(c), gfp);
+	if (!b->data)
+		return -BCH_ERR_ENOMEM_btree_node_mem_alloc;
+#ifdef __KERNEL__
+	b->aux_data = kvmalloc(btree_aux_data_bytes(b), gfp);
+#else
+	b->aux_data = mmap(NULL, btree_aux_data_bytes(b),
+			   PROT_READ|PROT_WRITE|PROT_EXEC,
+			   MAP_PRIVATE|MAP_ANONYMOUS, 0, 0);
+	if (b->aux_data == MAP_FAILED)
+		b->aux_data = NULL;
+#endif
+	if (!b->aux_data) {
+		kvpfree(b->data, btree_bytes(c));
+		b->data = NULL;
+		return -BCH_ERR_ENOMEM_btree_node_mem_alloc;
+	}
+
+	return 0;
+}
+
+static struct btree *__btree_node_mem_alloc(struct bch_fs *c, gfp_t gfp)
+{
+	struct btree *b;
+
+	b = kzalloc(sizeof(struct btree), gfp);
+	if (!b)
+		return NULL;
+
+	bkey_btree_ptr_init(&b->key);
+	INIT_LIST_HEAD(&b->list);
+	INIT_LIST_HEAD(&b->write_blocked);
+	b->byte_order = ilog2(btree_bytes(c));
+	return b;
+}
+
+struct btree *__bch2_btree_node_mem_alloc(struct bch_fs *c)
+{
+	struct btree_cache *bc = &c->btree_cache;
+	struct btree *b;
+
+	b = __btree_node_mem_alloc(c, GFP_KERNEL);
+	if (!b)
+		return NULL;
+
+	if (btree_node_data_alloc(c, b, GFP_KERNEL)) {
+		kfree(b);
+		return NULL;
+	}
+
+	bch2_btree_lock_init(&b->c, 0);
+
+	bc->used++;
+	list_add(&b->list, &bc->freeable);
+	return b;
+}
+
+/* Btree in memory cache - hash table */
+
+void bch2_btree_node_hash_remove(struct btree_cache *bc, struct btree *b)
+{
+	int ret = rhashtable_remove_fast(&bc->table, &b->hash, bch_btree_cache_params);
+
+	BUG_ON(ret);
+
+	/* Cause future lookups for this node to fail: */
+	b->hash_val = 0;
+}
+
+int __bch2_btree_node_hash_insert(struct btree_cache *bc, struct btree *b)
+{
+	BUG_ON(b->hash_val);
+	b->hash_val = btree_ptr_hash_val(&b->key);
+
+	return rhashtable_lookup_insert_fast(&bc->table, &b->hash,
+					     bch_btree_cache_params);
+}
+
+int bch2_btree_node_hash_insert(struct btree_cache *bc, struct btree *b,
+				unsigned level, enum btree_id id)
+{
+	int ret;
+
+	b->c.level	= level;
+	b->c.btree_id	= id;
+
+	mutex_lock(&bc->lock);
+	ret = __bch2_btree_node_hash_insert(bc, b);
+	if (!ret)
+		list_add_tail(&b->list, &bc->live);
+	mutex_unlock(&bc->lock);
+
+	return ret;
+}
+
+__flatten
+static inline struct btree *btree_cache_find(struct btree_cache *bc,
+				     const struct bkey_i *k)
+{
+	u64 v = btree_ptr_hash_val(k);
+
+	return rhashtable_lookup_fast(&bc->table, &v, bch_btree_cache_params);
+}
+
+/*
+ * this version is for btree nodes that have already been freed (we're not
+ * reaping a real btree node)
+ */
+static int __btree_node_reclaim(struct bch_fs *c, struct btree *b, bool flush)
+{
+	struct btree_cache *bc = &c->btree_cache;
+	int ret = 0;
+
+	lockdep_assert_held(&bc->lock);
+wait_on_io:
+	if (b->flags & ((1U << BTREE_NODE_dirty)|
+			(1U << BTREE_NODE_read_in_flight)|
+			(1U << BTREE_NODE_write_in_flight))) {
+		if (!flush)
+			return -BCH_ERR_ENOMEM_btree_node_reclaim;
+
+		/* XXX: waiting on IO with btree cache lock held */
+		bch2_btree_node_wait_on_read(b);
+		bch2_btree_node_wait_on_write(b);
+	}
+
+	if (!six_trylock_intent(&b->c.lock))
+		return -BCH_ERR_ENOMEM_btree_node_reclaim;
+
+	if (!six_trylock_write(&b->c.lock))
+		goto out_unlock_intent;
+
+	/* recheck under lock */
+	if (b->flags & ((1U << BTREE_NODE_read_in_flight)|
+			(1U << BTREE_NODE_write_in_flight))) {
+		if (!flush)
+			goto out_unlock;
+		six_unlock_write(&b->c.lock);
+		six_unlock_intent(&b->c.lock);
+		goto wait_on_io;
+	}
+
+	if (btree_node_noevict(b) ||
+	    btree_node_write_blocked(b) ||
+	    btree_node_will_make_reachable(b))
+		goto out_unlock;
+
+	if (btree_node_dirty(b)) {
+		if (!flush)
+			goto out_unlock;
+		/*
+		 * Using the underscore version because we don't want to compact
+		 * bsets after the write, since this node is about to be evicted
+		 * - unless btree verify mode is enabled, since it runs out of
+		 * the post write cleanup:
+		 */
+		if (bch2_verify_btree_ondisk)
+			bch2_btree_node_write(c, b, SIX_LOCK_intent,
+					      BTREE_WRITE_cache_reclaim);
+		else
+			__bch2_btree_node_write(c, b,
+						BTREE_WRITE_cache_reclaim);
+
+		six_unlock_write(&b->c.lock);
+		six_unlock_intent(&b->c.lock);
+		goto wait_on_io;
+	}
+out:
+	if (b->hash_val && !ret)
+		trace_and_count(c, btree_cache_reap, c, b);
+	return ret;
+out_unlock:
+	six_unlock_write(&b->c.lock);
+out_unlock_intent:
+	six_unlock_intent(&b->c.lock);
+	ret = -BCH_ERR_ENOMEM_btree_node_reclaim;
+	goto out;
+}
+
+static int btree_node_reclaim(struct bch_fs *c, struct btree *b)
+{
+	return __btree_node_reclaim(c, b, false);
+}
+
+static int btree_node_write_and_reclaim(struct bch_fs *c, struct btree *b)
+{
+	return __btree_node_reclaim(c, b, true);
+}
+
+static unsigned long bch2_btree_cache_scan(struct shrinker *shrink,
+					   struct shrink_control *sc)
+{
+	struct bch_fs *c = shrink->private_data;
+	struct btree_cache *bc = &c->btree_cache;
+	struct btree *b, *t;
+	unsigned long nr = sc->nr_to_scan;
+	unsigned long can_free = 0;
+	unsigned long freed = 0;
+	unsigned long touched = 0;
+	unsigned i, flags;
+	unsigned long ret = SHRINK_STOP;
+	bool trigger_writes = atomic_read(&bc->dirty) + nr >=
+		bc->used * 3 / 4;
+
+	if (bch2_btree_shrinker_disabled)
+		return SHRINK_STOP;
+
+	mutex_lock(&bc->lock);
+	flags = memalloc_nofs_save();
+
+	/*
+	 * It's _really_ critical that we don't free too many btree nodes - we
+	 * have to always leave ourselves a reserve. The reserve is how we
+	 * guarantee that allocating memory for a new btree node can always
+	 * succeed, so that inserting keys into the btree can always succeed and
+	 * IO can always make forward progress:
+	 */
+	can_free = btree_cache_can_free(bc);
+	nr = min_t(unsigned long, nr, can_free);
+
+	i = 0;
+	list_for_each_entry_safe(b, t, &bc->freeable, list) {
+		/*
+		 * Leave a few nodes on the freeable list, so that a btree split
+		 * won't have to hit the system allocator:
+		 */
+		if (++i <= 3)
+			continue;
+
+		touched++;
+
+		if (touched >= nr)
+			goto out;
+
+		if (!btree_node_reclaim(c, b)) {
+			btree_node_data_free(c, b);
+			six_unlock_write(&b->c.lock);
+			six_unlock_intent(&b->c.lock);
+			freed++;
+		}
+	}
+restart:
+	list_for_each_entry_safe(b, t, &bc->live, list) {
+		touched++;
+
+		if (btree_node_accessed(b)) {
+			clear_btree_node_accessed(b);
+		} else if (!btree_node_reclaim(c, b)) {
+			freed++;
+			btree_node_data_free(c, b);
+
+			bch2_btree_node_hash_remove(bc, b);
+			six_unlock_write(&b->c.lock);
+			six_unlock_intent(&b->c.lock);
+
+			if (freed == nr)
+				goto out_rotate;
+		} else if (trigger_writes &&
+			   btree_node_dirty(b) &&
+			   !btree_node_will_make_reachable(b) &&
+			   !btree_node_write_blocked(b) &&
+			   six_trylock_read(&b->c.lock)) {
+			list_move(&bc->live, &b->list);
+			mutex_unlock(&bc->lock);
+			__bch2_btree_node_write(c, b, BTREE_WRITE_cache_reclaim);
+			six_unlock_read(&b->c.lock);
+			if (touched >= nr)
+				goto out_nounlock;
+			mutex_lock(&bc->lock);
+			goto restart;
+		}
+
+		if (touched >= nr)
+			break;
+	}
+out_rotate:
+	if (&t->list != &bc->live)
+		list_move_tail(&bc->live, &t->list);
+out:
+	mutex_unlock(&bc->lock);
+out_nounlock:
+	ret = freed;
+	memalloc_nofs_restore(flags);
+	trace_and_count(c, btree_cache_scan, sc->nr_to_scan, can_free, ret);
+	return ret;
+}
+
+static unsigned long bch2_btree_cache_count(struct shrinker *shrink,
+					    struct shrink_control *sc)
+{
+	struct bch_fs *c = shrink->private_data;
+	struct btree_cache *bc = &c->btree_cache;
+
+	if (bch2_btree_shrinker_disabled)
+		return 0;
+
+	return btree_cache_can_free(bc);
+}
+
+void bch2_fs_btree_cache_exit(struct bch_fs *c)
+{
+	struct btree_cache *bc = &c->btree_cache;
+	struct btree *b;
+	unsigned i, flags;
+
+	shrinker_free(bc->shrink);
+
+	/* vfree() can allocate memory: */
+	flags = memalloc_nofs_save();
+	mutex_lock(&bc->lock);
+
+	if (c->verify_data)
+		list_move(&c->verify_data->list, &bc->live);
+
+	kvpfree(c->verify_ondisk, btree_bytes(c));
+
+	for (i = 0; i < btree_id_nr_alive(c); i++) {
+		struct btree_root *r = bch2_btree_id_root(c, i);
+
+		if (r->b)
+			list_add(&r->b->list, &bc->live);
+	}
+
+	list_splice(&bc->freeable, &bc->live);
+
+	while (!list_empty(&bc->live)) {
+		b = list_first_entry(&bc->live, struct btree, list);
+
+		BUG_ON(btree_node_read_in_flight(b) ||
+		       btree_node_write_in_flight(b));
+
+		btree_node_data_free(c, b);
+	}
+
+	BUG_ON(!bch2_journal_error(&c->journal) &&
+	       atomic_read(&c->btree_cache.dirty));
+
+	list_splice(&bc->freed_pcpu, &bc->freed_nonpcpu);
+
+	while (!list_empty(&bc->freed_nonpcpu)) {
+		b = list_first_entry(&bc->freed_nonpcpu, struct btree, list);
+		list_del(&b->list);
+		six_lock_exit(&b->c.lock);
+		kfree(b);
+	}
+
+	mutex_unlock(&bc->lock);
+	memalloc_nofs_restore(flags);
+
+	if (bc->table_init_done)
+		rhashtable_destroy(&bc->table);
+}
+
+int bch2_fs_btree_cache_init(struct bch_fs *c)
+{
+	struct btree_cache *bc = &c->btree_cache;
+	struct shrinker *shrink;
+	unsigned i;
+	int ret = 0;
+
+	ret = rhashtable_init(&bc->table, &bch_btree_cache_params);
+	if (ret)
+		goto err;
+
+	bc->table_init_done = true;
+
+	bch2_recalc_btree_reserve(c);
+
+	for (i = 0; i < bc->reserve; i++)
+		if (!__bch2_btree_node_mem_alloc(c))
+			goto err;
+
+	list_splice_init(&bc->live, &bc->freeable);
+
+	mutex_init(&c->verify_lock);
+
+	shrink = shrinker_alloc(0, "%s-btree_cache", c->name);
+	if (!shrink)
+		goto err;
+	bc->shrink = shrink;
+	shrink->count_objects	= bch2_btree_cache_count;
+	shrink->scan_objects	= bch2_btree_cache_scan;
+	shrink->seeks		= 4;
+	shrink->private_data	= c;
+	shrinker_register(shrink);
+
+	return 0;
+err:
+	return -BCH_ERR_ENOMEM_fs_btree_cache_init;
+}
+
+void bch2_fs_btree_cache_init_early(struct btree_cache *bc)
+{
+	mutex_init(&bc->lock);
+	INIT_LIST_HEAD(&bc->live);
+	INIT_LIST_HEAD(&bc->freeable);
+	INIT_LIST_HEAD(&bc->freed_pcpu);
+	INIT_LIST_HEAD(&bc->freed_nonpcpu);
+}
+
+/*
+ * We can only have one thread cannibalizing other cached btree nodes at a time,
+ * or we'll deadlock. We use an open coded mutex to ensure that, which a
+ * cannibalize_bucket() will take. This means every time we unlock the root of
+ * the btree, we need to release this lock if we have it held.
+ */
+void bch2_btree_cache_cannibalize_unlock(struct bch_fs *c)
+{
+	struct btree_cache *bc = &c->btree_cache;
+
+	if (bc->alloc_lock == current) {
+		trace_and_count(c, btree_cache_cannibalize_unlock, c);
+		bc->alloc_lock = NULL;
+		closure_wake_up(&bc->alloc_wait);
+	}
+}
+
+int bch2_btree_cache_cannibalize_lock(struct bch_fs *c, struct closure *cl)
+{
+	struct btree_cache *bc = &c->btree_cache;
+	struct task_struct *old;
+
+	old = cmpxchg(&bc->alloc_lock, NULL, current);
+	if (old == NULL || old == current)
+		goto success;
+
+	if (!cl) {
+		trace_and_count(c, btree_cache_cannibalize_lock_fail, c);
+		return -BCH_ERR_ENOMEM_btree_cache_cannibalize_lock;
+	}
+
+	closure_wait(&bc->alloc_wait, cl);
+
+	/* Try again, after adding ourselves to waitlist */
+	old = cmpxchg(&bc->alloc_lock, NULL, current);
+	if (old == NULL || old == current) {
+		/* We raced */
+		closure_wake_up(&bc->alloc_wait);
+		goto success;
+	}
+
+	trace_and_count(c, btree_cache_cannibalize_lock_fail, c);
+	return -BCH_ERR_btree_cache_cannibalize_lock_blocked;
+
+success:
+	trace_and_count(c, btree_cache_cannibalize_lock, c);
+	return 0;
+}
+
+static struct btree *btree_node_cannibalize(struct bch_fs *c)
+{
+	struct btree_cache *bc = &c->btree_cache;
+	struct btree *b;
+
+	list_for_each_entry_reverse(b, &bc->live, list)
+		if (!btree_node_reclaim(c, b))
+			return b;
+
+	while (1) {
+		list_for_each_entry_reverse(b, &bc->live, list)
+			if (!btree_node_write_and_reclaim(c, b))
+				return b;
+
+		/*
+		 * Rare case: all nodes were intent-locked.
+		 * Just busy-wait.
+		 */
+		WARN_ONCE(1, "btree cache cannibalize failed\n");
+		cond_resched();
+	}
+}
+
+struct btree *bch2_btree_node_mem_alloc(struct btree_trans *trans, bool pcpu_read_locks)
+{
+	struct bch_fs *c = trans->c;
+	struct btree_cache *bc = &c->btree_cache;
+	struct list_head *freed = pcpu_read_locks
+		? &bc->freed_pcpu
+		: &bc->freed_nonpcpu;
+	struct btree *b, *b2;
+	u64 start_time = local_clock();
+	unsigned flags;
+
+	flags = memalloc_nofs_save();
+	mutex_lock(&bc->lock);
+
+	/*
+	 * We never free struct btree itself, just the memory that holds the on
+	 * disk node. Check the freed list before allocating a new one:
+	 */
+	list_for_each_entry(b, freed, list)
+		if (!btree_node_reclaim(c, b)) {
+			list_del_init(&b->list);
+			goto got_node;
+		}
+
+	b = __btree_node_mem_alloc(c, GFP_NOWAIT|__GFP_NOWARN);
+	if (!b) {
+		mutex_unlock(&bc->lock);
+		bch2_trans_unlock(trans);
+		b = __btree_node_mem_alloc(c, GFP_KERNEL);
+		if (!b)
+			goto err;
+		mutex_lock(&bc->lock);
+	}
+
+	bch2_btree_lock_init(&b->c, pcpu_read_locks ? SIX_LOCK_INIT_PCPU : 0);
+
+	BUG_ON(!six_trylock_intent(&b->c.lock));
+	BUG_ON(!six_trylock_write(&b->c.lock));
+got_node:
+
+	/*
+	 * btree_free() doesn't free memory; it sticks the node on the end of
+	 * the list. Check if there's any freed nodes there:
+	 */
+	list_for_each_entry(b2, &bc->freeable, list)
+		if (!btree_node_reclaim(c, b2)) {
+			swap(b->data, b2->data);
+			swap(b->aux_data, b2->aux_data);
+			btree_node_to_freedlist(bc, b2);
+			six_unlock_write(&b2->c.lock);
+			six_unlock_intent(&b2->c.lock);
+			goto got_mem;
+		}
+
+	mutex_unlock(&bc->lock);
+
+	if (btree_node_data_alloc(c, b, GFP_NOWAIT|__GFP_NOWARN)) {
+		bch2_trans_unlock(trans);
+		if (btree_node_data_alloc(c, b, GFP_KERNEL|__GFP_NOWARN))
+			goto err;
+	}
+
+	mutex_lock(&bc->lock);
+	bc->used++;
+got_mem:
+	mutex_unlock(&bc->lock);
+
+	BUG_ON(btree_node_hashed(b));
+	BUG_ON(btree_node_dirty(b));
+	BUG_ON(btree_node_write_in_flight(b));
+out:
+	b->flags		= 0;
+	b->written		= 0;
+	b->nsets		= 0;
+	b->sib_u64s[0]		= 0;
+	b->sib_u64s[1]		= 0;
+	b->whiteout_u64s	= 0;
+	bch2_btree_keys_init(b);
+	set_btree_node_accessed(b);
+
+	bch2_time_stats_update(&c->times[BCH_TIME_btree_node_mem_alloc],
+			       start_time);
+
+	memalloc_nofs_restore(flags);
+	return b;
+err:
+	mutex_lock(&bc->lock);
+
+	/* Try to cannibalize another cached btree node: */
+	if (bc->alloc_lock == current) {
+		b2 = btree_node_cannibalize(c);
+		clear_btree_node_just_written(b2);
+		bch2_btree_node_hash_remove(bc, b2);
+
+		if (b) {
+			swap(b->data, b2->data);
+			swap(b->aux_data, b2->aux_data);
+			btree_node_to_freedlist(bc, b2);
+			six_unlock_write(&b2->c.lock);
+			six_unlock_intent(&b2->c.lock);
+		} else {
+			b = b2;
+			list_del_init(&b->list);
+		}
+
+		mutex_unlock(&bc->lock);
+
+		trace_and_count(c, btree_cache_cannibalize, c);
+		goto out;
+	}
+
+	mutex_unlock(&bc->lock);
+	memalloc_nofs_restore(flags);
+	return ERR_PTR(-BCH_ERR_ENOMEM_btree_node_mem_alloc);
+}
+
+/* Slowpath, don't want it inlined into btree_iter_traverse() */
+static noinline struct btree *bch2_btree_node_fill(struct btree_trans *trans,
+				struct btree_path *path,
+				const struct bkey_i *k,
+				enum btree_id btree_id,
+				unsigned level,
+				enum six_lock_type lock_type,
+				bool sync)
+{
+	struct bch_fs *c = trans->c;
+	struct btree_cache *bc = &c->btree_cache;
+	struct btree *b;
+	u32 seq;
+
+	BUG_ON(level + 1 >= BTREE_MAX_DEPTH);
+	/*
+	 * Parent node must be locked, else we could read in a btree node that's
+	 * been freed:
+	 */
+	if (path && !bch2_btree_node_relock(trans, path, level + 1)) {
+		trace_and_count(c, trans_restart_relock_parent_for_fill, trans, _THIS_IP_, path);
+		return ERR_PTR(btree_trans_restart(trans, BCH_ERR_transaction_restart_fill_relock));
+	}
+
+	b = bch2_btree_node_mem_alloc(trans, level != 0);
+
+	if (bch2_err_matches(PTR_ERR_OR_ZERO(b), ENOMEM)) {
+		trans->memory_allocation_failure = true;
+		trace_and_count(c, trans_restart_memory_allocation_failure, trans, _THIS_IP_, path);
+		return ERR_PTR(btree_trans_restart(trans, BCH_ERR_transaction_restart_fill_mem_alloc_fail));
+	}
+
+	if (IS_ERR(b))
+		return b;
+
+	/*
+	 * Btree nodes read in from disk should not have the accessed bit set
+	 * initially, so that linear scans don't thrash the cache:
+	 */
+	clear_btree_node_accessed(b);
+
+	bkey_copy(&b->key, k);
+	if (bch2_btree_node_hash_insert(bc, b, level, btree_id)) {
+		/* raced with another fill: */
+
+		/* mark as unhashed... */
+		b->hash_val = 0;
+
+		mutex_lock(&bc->lock);
+		list_add(&b->list, &bc->freeable);
+		mutex_unlock(&bc->lock);
+
+		six_unlock_write(&b->c.lock);
+		six_unlock_intent(&b->c.lock);
+		return NULL;
+	}
+
+	set_btree_node_read_in_flight(b);
+
+	six_unlock_write(&b->c.lock);
+	seq = six_lock_seq(&b->c.lock);
+	six_unlock_intent(&b->c.lock);
+
+	/* Unlock before doing IO: */
+	if (path && sync)
+		bch2_trans_unlock_noassert(trans);
+
+	bch2_btree_node_read(c, b, sync);
+
+	if (!sync)
+		return NULL;
+
+	if (path) {
+		int ret = bch2_trans_relock(trans) ?:
+			bch2_btree_path_relock_intent(trans, path);
+		if (ret) {
+			BUG_ON(!trans->restarted);
+			return ERR_PTR(ret);
+		}
+	}
+
+	if (!six_relock_type(&b->c.lock, lock_type, seq)) {
+		if (path)
+			trace_and_count(c, trans_restart_relock_after_fill, trans, _THIS_IP_, path);
+		return ERR_PTR(btree_trans_restart(trans, BCH_ERR_transaction_restart_relock_after_fill));
+	}
+
+	return b;
+}
+
+static noinline void btree_bad_header(struct bch_fs *c, struct btree *b)
+{
+	struct printbuf buf = PRINTBUF;
+
+	if (c->curr_recovery_pass <= BCH_RECOVERY_PASS_check_allocations)
+		return;
+
+	prt_printf(&buf,
+	       "btree node header doesn't match ptr\n"
+	       "btree %s level %u\n"
+	       "ptr: ",
+	       bch2_btree_id_str(b->c.btree_id), b->c.level);
+	bch2_bkey_val_to_text(&buf, c, bkey_i_to_s_c(&b->key));
+
+	prt_printf(&buf, "\nheader: btree %s level %llu\n"
+	       "min ",
+	       bch2_btree_id_str(BTREE_NODE_ID(b->data)),
+	       BTREE_NODE_LEVEL(b->data));
+	bch2_bpos_to_text(&buf, b->data->min_key);
+
+	prt_printf(&buf, "\nmax ");
+	bch2_bpos_to_text(&buf, b->data->max_key);
+
+	bch2_fs_inconsistent(c, "%s", buf.buf);
+	printbuf_exit(&buf);
+}
+
+static inline void btree_check_header(struct bch_fs *c, struct btree *b)
+{
+	if (b->c.btree_id != BTREE_NODE_ID(b->data) ||
+	    b->c.level != BTREE_NODE_LEVEL(b->data) ||
+	    !bpos_eq(b->data->max_key, b->key.k.p) ||
+	    (b->key.k.type == KEY_TYPE_btree_ptr_v2 &&
+	     !bpos_eq(b->data->min_key,
+		      bkey_i_to_btree_ptr_v2(&b->key)->v.min_key)))
+		btree_bad_header(c, b);
+}
+
+static struct btree *__bch2_btree_node_get(struct btree_trans *trans, struct btree_path *path,
+					   const struct bkey_i *k, unsigned level,
+					   enum six_lock_type lock_type,
+					   unsigned long trace_ip)
+{
+	struct bch_fs *c = trans->c;
+	struct btree_cache *bc = &c->btree_cache;
+	struct btree *b;
+	struct bset_tree *t;
+	bool need_relock = false;
+	int ret;
+
+	EBUG_ON(level >= BTREE_MAX_DEPTH);
+retry:
+	b = btree_cache_find(bc, k);
+	if (unlikely(!b)) {
+		/*
+		 * We must have the parent locked to call bch2_btree_node_fill(),
+		 * else we could read in a btree node from disk that's been
+		 * freed:
+		 */
+		b = bch2_btree_node_fill(trans, path, k, path->btree_id,
+					 level, lock_type, true);
+		need_relock = true;
+
+		/* We raced and found the btree node in the cache */
+		if (!b)
+			goto retry;
+
+		if (IS_ERR(b))
+			return b;
+	} else {
+		if (btree_node_read_locked(path, level + 1))
+			btree_node_unlock(trans, path, level + 1);
+
+		ret = btree_node_lock(trans, path, &b->c, level, lock_type, trace_ip);
+		if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
+			return ERR_PTR(ret);
+
+		BUG_ON(ret);
+
+		if (unlikely(b->hash_val != btree_ptr_hash_val(k) ||
+			     b->c.level != level ||
+			     race_fault())) {
+			six_unlock_type(&b->c.lock, lock_type);
+			if (bch2_btree_node_relock(trans, path, level + 1))
+				goto retry;
+
+			trace_and_count(c, trans_restart_btree_node_reused, trans, trace_ip, path);
+			return ERR_PTR(btree_trans_restart(trans, BCH_ERR_transaction_restart_lock_node_reused));
+		}
+
+		/* avoid atomic set bit if it's not needed: */
+		if (!btree_node_accessed(b))
+			set_btree_node_accessed(b);
+	}
+
+	if (unlikely(btree_node_read_in_flight(b))) {
+		u32 seq = six_lock_seq(&b->c.lock);
+
+		six_unlock_type(&b->c.lock, lock_type);
+		bch2_trans_unlock(trans);
+		need_relock = true;
+
+		bch2_btree_node_wait_on_read(b);
+
+		/*
+		 * should_be_locked is not set on this path yet, so we need to
+		 * relock it specifically:
+		 */
+		if (!six_relock_type(&b->c.lock, lock_type, seq))
+			goto retry;
+	}
+
+	if (unlikely(need_relock)) {
+		ret = bch2_trans_relock(trans) ?:
+			bch2_btree_path_relock_intent(trans, path);
+		if (ret) {
+			six_unlock_type(&b->c.lock, lock_type);
+			return ERR_PTR(ret);
+		}
+	}
+
+	prefetch(b->aux_data);
+
+	for_each_bset(b, t) {
+		void *p = (u64 *) b->aux_data + t->aux_data_offset;
+
+		prefetch(p + L1_CACHE_BYTES * 0);
+		prefetch(p + L1_CACHE_BYTES * 1);
+		prefetch(p + L1_CACHE_BYTES * 2);
+	}
+
+	if (unlikely(btree_node_read_error(b))) {
+		six_unlock_type(&b->c.lock, lock_type);
+		return ERR_PTR(-EIO);
+	}
+
+	EBUG_ON(b->c.btree_id != path->btree_id);
+	EBUG_ON(BTREE_NODE_LEVEL(b->data) != level);
+	btree_check_header(c, b);
+
+	return b;
+}
+
+/**
+ * bch2_btree_node_get - find a btree node in the cache and lock it, reading it
+ * in from disk if necessary.
+ *
+ * @trans:	btree transaction object
+ * @path:	btree_path being traversed
+ * @k:		pointer to btree node (generally KEY_TYPE_btree_ptr_v2)
+ * @level:	level of btree node being looked up (0 == leaf node)
+ * @lock_type:	SIX_LOCK_read or SIX_LOCK_intent
+ * @trace_ip:	ip of caller of btree iterator code (i.e. caller of bch2_btree_iter_peek())
+ *
+ * The btree node will have either a read or a write lock held, depending on
+ * the @write parameter.
+ *
+ * Returns: btree node or ERR_PTR()
+ */
+struct btree *bch2_btree_node_get(struct btree_trans *trans, struct btree_path *path,
+				  const struct bkey_i *k, unsigned level,
+				  enum six_lock_type lock_type,
+				  unsigned long trace_ip)
+{
+	struct bch_fs *c = trans->c;
+	struct btree *b;
+	struct bset_tree *t;
+	int ret;
+
+	EBUG_ON(level >= BTREE_MAX_DEPTH);
+
+	b = btree_node_mem_ptr(k);
+
+	/*
+	 * Check b->hash_val _before_ calling btree_node_lock() - this might not
+	 * be the node we want anymore, and trying to lock the wrong node could
+	 * cause an unneccessary transaction restart:
+	 */
+	if (unlikely(!c->opts.btree_node_mem_ptr_optimization ||
+		     !b ||
+		     b->hash_val != btree_ptr_hash_val(k)))
+		return __bch2_btree_node_get(trans, path, k, level, lock_type, trace_ip);
+
+	if (btree_node_read_locked(path, level + 1))
+		btree_node_unlock(trans, path, level + 1);
+
+	ret = btree_node_lock(trans, path, &b->c, level, lock_type, trace_ip);
+	if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
+		return ERR_PTR(ret);
+
+	BUG_ON(ret);
+
+	if (unlikely(b->hash_val != btree_ptr_hash_val(k) ||
+		     b->c.level != level ||
+		     race_fault())) {
+		six_unlock_type(&b->c.lock, lock_type);
+		if (bch2_btree_node_relock(trans, path, level + 1))
+			return __bch2_btree_node_get(trans, path, k, level, lock_type, trace_ip);
+
+		trace_and_count(c, trans_restart_btree_node_reused, trans, trace_ip, path);
+		return ERR_PTR(btree_trans_restart(trans, BCH_ERR_transaction_restart_lock_node_reused));
+	}
+
+	if (unlikely(btree_node_read_in_flight(b))) {
+		six_unlock_type(&b->c.lock, lock_type);
+		return __bch2_btree_node_get(trans, path, k, level, lock_type, trace_ip);
+	}
+
+	prefetch(b->aux_data);
+
+	for_each_bset(b, t) {
+		void *p = (u64 *) b->aux_data + t->aux_data_offset;
+
+		prefetch(p + L1_CACHE_BYTES * 0);
+		prefetch(p + L1_CACHE_BYTES * 1);
+		prefetch(p + L1_CACHE_BYTES * 2);
+	}
+
+	/* avoid atomic set bit if it's not needed: */
+	if (!btree_node_accessed(b))
+		set_btree_node_accessed(b);
+
+	if (unlikely(btree_node_read_error(b))) {
+		six_unlock_type(&b->c.lock, lock_type);
+		return ERR_PTR(-EIO);
+	}
+
+	EBUG_ON(b->c.btree_id != path->btree_id);
+	EBUG_ON(BTREE_NODE_LEVEL(b->data) != level);
+	btree_check_header(c, b);
+
+	return b;
+}
+
+struct btree *bch2_btree_node_get_noiter(struct btree_trans *trans,
+					 const struct bkey_i *k,
+					 enum btree_id btree_id,
+					 unsigned level,
+					 bool nofill)
+{
+	struct bch_fs *c = trans->c;
+	struct btree_cache *bc = &c->btree_cache;
+	struct btree *b;
+	struct bset_tree *t;
+	int ret;
+
+	EBUG_ON(level >= BTREE_MAX_DEPTH);
+
+	if (c->opts.btree_node_mem_ptr_optimization) {
+		b = btree_node_mem_ptr(k);
+		if (b)
+			goto lock_node;
+	}
+retry:
+	b = btree_cache_find(bc, k);
+	if (unlikely(!b)) {
+		if (nofill)
+			goto out;
+
+		b = bch2_btree_node_fill(trans, NULL, k, btree_id,
+					 level, SIX_LOCK_read, true);
+
+		/* We raced and found the btree node in the cache */
+		if (!b)
+			goto retry;
+
+		if (IS_ERR(b) &&
+		    !bch2_btree_cache_cannibalize_lock(c, NULL))
+			goto retry;
+
+		if (IS_ERR(b))
+			goto out;
+	} else {
+lock_node:
+		ret = btree_node_lock_nopath(trans, &b->c, SIX_LOCK_read, _THIS_IP_);
+		if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
+			return ERR_PTR(ret);
+
+		BUG_ON(ret);
+
+		if (unlikely(b->hash_val != btree_ptr_hash_val(k) ||
+			     b->c.btree_id != btree_id ||
+			     b->c.level != level)) {
+			six_unlock_read(&b->c.lock);
+			goto retry;
+		}
+	}
+
+	/* XXX: waiting on IO with btree locks held: */
+	__bch2_btree_node_wait_on_read(b);
+
+	prefetch(b->aux_data);
+
+	for_each_bset(b, t) {
+		void *p = (u64 *) b->aux_data + t->aux_data_offset;
+
+		prefetch(p + L1_CACHE_BYTES * 0);
+		prefetch(p + L1_CACHE_BYTES * 1);
+		prefetch(p + L1_CACHE_BYTES * 2);
+	}
+
+	/* avoid atomic set bit if it's not needed: */
+	if (!btree_node_accessed(b))
+		set_btree_node_accessed(b);
+
+	if (unlikely(btree_node_read_error(b))) {
+		six_unlock_read(&b->c.lock);
+		b = ERR_PTR(-EIO);
+		goto out;
+	}
+
+	EBUG_ON(b->c.btree_id != btree_id);
+	EBUG_ON(BTREE_NODE_LEVEL(b->data) != level);
+	btree_check_header(c, b);
+out:
+	bch2_btree_cache_cannibalize_unlock(c);
+	return b;
+}
+
+int bch2_btree_node_prefetch(struct btree_trans *trans,
+			     struct btree_path *path,
+			     const struct bkey_i *k,
+			     enum btree_id btree_id, unsigned level)
+{
+	struct bch_fs *c = trans->c;
+	struct btree_cache *bc = &c->btree_cache;
+	struct btree *b;
+
+	BUG_ON(trans && !btree_node_locked(path, level + 1));
+	BUG_ON(level >= BTREE_MAX_DEPTH);
+
+	b = btree_cache_find(bc, k);
+	if (b)
+		return 0;
+
+	b = bch2_btree_node_fill(trans, path, k, btree_id,
+				 level, SIX_LOCK_read, false);
+	return PTR_ERR_OR_ZERO(b);
+}
+
+void bch2_btree_node_evict(struct btree_trans *trans, const struct bkey_i *k)
+{
+	struct bch_fs *c = trans->c;
+	struct btree_cache *bc = &c->btree_cache;
+	struct btree *b;
+
+	b = btree_cache_find(bc, k);
+	if (!b)
+		return;
+wait_on_io:
+	/* not allowed to wait on io with btree locks held: */
+
+	/* XXX we're called from btree_gc which will be holding other btree
+	 * nodes locked
+	 */
+	__bch2_btree_node_wait_on_read(b);
+	__bch2_btree_node_wait_on_write(b);
+
+	btree_node_lock_nopath_nofail(trans, &b->c, SIX_LOCK_intent);
+	btree_node_lock_nopath_nofail(trans, &b->c, SIX_LOCK_write);
+
+	if (btree_node_dirty(b)) {
+		__bch2_btree_node_write(c, b, BTREE_WRITE_cache_reclaim);
+		six_unlock_write(&b->c.lock);
+		six_unlock_intent(&b->c.lock);
+		goto wait_on_io;
+	}
+
+	BUG_ON(btree_node_dirty(b));
+
+	mutex_lock(&bc->lock);
+	btree_node_data_free(c, b);
+	bch2_btree_node_hash_remove(bc, b);
+	mutex_unlock(&bc->lock);
+
+	six_unlock_write(&b->c.lock);
+	six_unlock_intent(&b->c.lock);
+}
+
+const char *bch2_btree_id_str(enum btree_id btree)
+{
+	return btree < BTREE_ID_NR ? __bch2_btree_ids[btree] : "(unknown)";
+}
+
+void bch2_btree_pos_to_text(struct printbuf *out, struct bch_fs *c, const struct btree *b)
+{
+	prt_printf(out, "%s level %u/%u\n  ",
+	       bch2_btree_id_str(b->c.btree_id),
+	       b->c.level,
+	       bch2_btree_id_root(c, b->c.btree_id)->level);
+	bch2_bkey_val_to_text(out, c, bkey_i_to_s_c(&b->key));
+}
+
+void bch2_btree_node_to_text(struct printbuf *out, struct bch_fs *c, const struct btree *b)
+{
+	struct bset_stats stats;
+
+	memset(&stats, 0, sizeof(stats));
+
+	bch2_btree_keys_stats(b, &stats);
+
+	prt_printf(out, "l %u ", b->c.level);
+	bch2_bpos_to_text(out, b->data->min_key);
+	prt_printf(out, " - ");
+	bch2_bpos_to_text(out, b->data->max_key);
+	prt_printf(out, ":\n"
+	       "    ptrs: ");
+	bch2_val_to_text(out, c, bkey_i_to_s_c(&b->key));
+	prt_newline(out);
+
+	prt_printf(out,
+	       "    format: ");
+	bch2_bkey_format_to_text(out, &b->format);
+
+	prt_printf(out,
+	       "    unpack fn len: %u\n"
+	       "    bytes used %zu/%zu (%zu%% full)\n"
+	       "    sib u64s: %u, %u (merge threshold %u)\n"
+	       "    nr packed keys %u\n"
+	       "    nr unpacked keys %u\n"
+	       "    floats %zu\n"
+	       "    failed unpacked %zu\n",
+	       b->unpack_fn_len,
+	       b->nr.live_u64s * sizeof(u64),
+	       btree_bytes(c) - sizeof(struct btree_node),
+	       b->nr.live_u64s * 100 / btree_max_u64s(c),
+	       b->sib_u64s[0],
+	       b->sib_u64s[1],
+	       c->btree_foreground_merge_threshold,
+	       b->nr.packed_keys,
+	       b->nr.unpacked_keys,
+	       stats.floats,
+	       stats.failed);
+}
+
+void bch2_btree_cache_to_text(struct printbuf *out, const struct bch_fs *c)
+{
+	prt_printf(out, "nr nodes:\t\t%u\n", c->btree_cache.used);
+	prt_printf(out, "nr dirty:\t\t%u\n", atomic_read(&c->btree_cache.dirty));
+	prt_printf(out, "cannibalize lock:\t%p\n", c->btree_cache.alloc_lock);
+}