Adding upstream version 6.7.7.upstream/6.7.7

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

1 files changed, 1592 insertions, 0 deletions

diff --git a/fs/bcachefs/bset.c b/fs/bcachefs/bset.c
new file mode 100644
index 0000000000..bb73ba9017
--- /dev/null
+++ b/fs/bcachefs/bset.c
@@ -0,0 +1,1592 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Code for working with individual keys, and sorted sets of keys with in a
+ * btree node
+ *
+ * Copyright 2012 Google, Inc.
+ */
+
+#include "bcachefs.h"
+#include "btree_cache.h"
+#include "bset.h"
+#include "eytzinger.h"
+#include "trace.h"
+#include "util.h"
+
+#include <asm/unaligned.h>
+#include <linux/console.h>
+#include <linux/random.h>
+#include <linux/prefetch.h>
+
+static inline void __bch2_btree_node_iter_advance(struct btree_node_iter *,
+						  struct btree *);
+
+static inline unsigned __btree_node_iter_used(struct btree_node_iter *iter)
+{
+	unsigned n = ARRAY_SIZE(iter->data);
+
+	while (n && __btree_node_iter_set_end(iter, n - 1))
+		--n;
+
+	return n;
+}
+
+struct bset_tree *bch2_bkey_to_bset(struct btree *b, struct bkey_packed *k)
+{
+	return bch2_bkey_to_bset_inlined(b, k);
+}
+
+/*
+ * There are never duplicate live keys in the btree - but including keys that
+ * have been flagged as deleted (and will be cleaned up later) we _will_ see
+ * duplicates.
+ *
+ * Thus the sort order is: usual key comparison first, but for keys that compare
+ * equal the deleted key(s) come first, and the (at most one) live version comes
+ * last.
+ *
+ * The main reason for this is insertion: to handle overwrites, we first iterate
+ * over keys that compare equal to our insert key, and then insert immediately
+ * prior to the first key greater than the key we're inserting - our insert
+ * position will be after all keys that compare equal to our insert key, which
+ * by the time we actually do the insert will all be deleted.
+ */
+
+void bch2_dump_bset(struct bch_fs *c, struct btree *b,
+		    struct bset *i, unsigned set)
+{
+	struct bkey_packed *_k, *_n;
+	struct bkey uk, n;
+	struct bkey_s_c k;
+	struct printbuf buf = PRINTBUF;
+
+	if (!i->u64s)
+		return;
+
+	for (_k = i->start;
+	     _k < vstruct_last(i);
+	     _k = _n) {
+		_n = bkey_p_next(_k);
+
+		k = bkey_disassemble(b, _k, &uk);
+
+		printbuf_reset(&buf);
+		if (c)
+			bch2_bkey_val_to_text(&buf, c, k);
+		else
+			bch2_bkey_to_text(&buf, k.k);
+		printk(KERN_ERR "block %u key %5zu: %s\n", set,
+		       _k->_data - i->_data, buf.buf);
+
+		if (_n == vstruct_last(i))
+			continue;
+
+		n = bkey_unpack_key(b, _n);
+
+		if (bpos_lt(n.p, k.k->p)) {
+			printk(KERN_ERR "Key skipped backwards\n");
+			continue;
+		}
+
+		if (!bkey_deleted(k.k) && bpos_eq(n.p, k.k->p))
+			printk(KERN_ERR "Duplicate keys\n");
+	}
+
+	printbuf_exit(&buf);
+}
+
+void bch2_dump_btree_node(struct bch_fs *c, struct btree *b)
+{
+	struct bset_tree *t;
+
+	console_lock();
+	for_each_bset(b, t)
+		bch2_dump_bset(c, b, bset(b, t), t - b->set);
+	console_unlock();
+}
+
+void bch2_dump_btree_node_iter(struct btree *b,
+			      struct btree_node_iter *iter)
+{
+	struct btree_node_iter_set *set;
+	struct printbuf buf = PRINTBUF;
+
+	printk(KERN_ERR "btree node iter with %u/%u sets:\n",
+	       __btree_node_iter_used(iter), b->nsets);
+
+	btree_node_iter_for_each(iter, set) {
+		struct bkey_packed *k = __btree_node_offset_to_key(b, set->k);
+		struct bset_tree *t = bch2_bkey_to_bset(b, k);
+		struct bkey uk = bkey_unpack_key(b, k);
+
+		printbuf_reset(&buf);
+		bch2_bkey_to_text(&buf, &uk);
+		printk(KERN_ERR "set %zu key %u: %s\n",
+		       t - b->set, set->k, buf.buf);
+	}
+
+	printbuf_exit(&buf);
+}
+
+#ifdef CONFIG_BCACHEFS_DEBUG
+
+void __bch2_verify_btree_nr_keys(struct btree *b)
+{
+	struct bset_tree *t;
+	struct bkey_packed *k;
+	struct btree_nr_keys nr = { 0 };
+
+	for_each_bset(b, t)
+		bset_tree_for_each_key(b, t, k)
+			if (!bkey_deleted(k))
+				btree_keys_account_key_add(&nr, t - b->set, k);
+
+	BUG_ON(memcmp(&nr, &b->nr, sizeof(nr)));
+}
+
+static void bch2_btree_node_iter_next_check(struct btree_node_iter *_iter,
+					    struct btree *b)
+{
+	struct btree_node_iter iter = *_iter;
+	const struct bkey_packed *k, *n;
+
+	k = bch2_btree_node_iter_peek_all(&iter, b);
+	__bch2_btree_node_iter_advance(&iter, b);
+	n = bch2_btree_node_iter_peek_all(&iter, b);
+
+	bkey_unpack_key(b, k);
+
+	if (n &&
+	    bkey_iter_cmp(b, k, n) > 0) {
+		struct btree_node_iter_set *set;
+		struct bkey ku = bkey_unpack_key(b, k);
+		struct bkey nu = bkey_unpack_key(b, n);
+		struct printbuf buf1 = PRINTBUF;
+		struct printbuf buf2 = PRINTBUF;
+
+		bch2_dump_btree_node(NULL, b);
+		bch2_bkey_to_text(&buf1, &ku);
+		bch2_bkey_to_text(&buf2, &nu);
+		printk(KERN_ERR "out of order/overlapping:\n%s\n%s\n",
+		       buf1.buf, buf2.buf);
+		printk(KERN_ERR "iter was:");
+
+		btree_node_iter_for_each(_iter, set) {
+			struct bkey_packed *k2 = __btree_node_offset_to_key(b, set->k);
+			struct bset_tree *t = bch2_bkey_to_bset(b, k2);
+			printk(" [%zi %zi]", t - b->set,
+			       k2->_data - bset(b, t)->_data);
+		}
+		panic("\n");
+	}
+}
+
+void bch2_btree_node_iter_verify(struct btree_node_iter *iter,
+				 struct btree *b)
+{
+	struct btree_node_iter_set *set, *s2;
+	struct bkey_packed *k, *p;
+	struct bset_tree *t;
+
+	if (bch2_btree_node_iter_end(iter))
+		return;
+
+	/* Verify no duplicates: */
+	btree_node_iter_for_each(iter, set) {
+		BUG_ON(set->k > set->end);
+		btree_node_iter_for_each(iter, s2)
+			BUG_ON(set != s2 && set->end == s2->end);
+	}
+
+	/* Verify that set->end is correct: */
+	btree_node_iter_for_each(iter, set) {
+		for_each_bset(b, t)
+			if (set->end == t->end_offset)
+				goto found;
+		BUG();
+found:
+		BUG_ON(set->k < btree_bkey_first_offset(t) ||
+		       set->k >= t->end_offset);
+	}
+
+	/* Verify iterator is sorted: */
+	btree_node_iter_for_each(iter, set)
+		BUG_ON(set != iter->data &&
+		       btree_node_iter_cmp(b, set[-1], set[0]) > 0);
+
+	k = bch2_btree_node_iter_peek_all(iter, b);
+
+	for_each_bset(b, t) {
+		if (iter->data[0].end == t->end_offset)
+			continue;
+
+		p = bch2_bkey_prev_all(b, t,
+			bch2_btree_node_iter_bset_pos(iter, b, t));
+
+		BUG_ON(p && bkey_iter_cmp(b, k, p) < 0);
+	}
+}
+
+void bch2_verify_insert_pos(struct btree *b, struct bkey_packed *where,
+			    struct bkey_packed *insert, unsigned clobber_u64s)
+{
+	struct bset_tree *t = bch2_bkey_to_bset(b, where);
+	struct bkey_packed *prev = bch2_bkey_prev_all(b, t, where);
+	struct bkey_packed *next = (void *) ((u64 *) where->_data + clobber_u64s);
+	struct printbuf buf1 = PRINTBUF;
+	struct printbuf buf2 = PRINTBUF;
+#if 0
+	BUG_ON(prev &&
+	       bkey_iter_cmp(b, prev, insert) > 0);
+#else
+	if (prev &&
+	    bkey_iter_cmp(b, prev, insert) > 0) {
+		struct bkey k1 = bkey_unpack_key(b, prev);
+		struct bkey k2 = bkey_unpack_key(b, insert);
+
+		bch2_dump_btree_node(NULL, b);
+		bch2_bkey_to_text(&buf1, &k1);
+		bch2_bkey_to_text(&buf2, &k2);
+
+		panic("prev > insert:\n"
+		      "prev    key %s\n"
+		      "insert  key %s\n",
+		      buf1.buf, buf2.buf);
+	}
+#endif
+#if 0
+	BUG_ON(next != btree_bkey_last(b, t) &&
+	       bkey_iter_cmp(b, insert, next) > 0);
+#else
+	if (next != btree_bkey_last(b, t) &&
+	    bkey_iter_cmp(b, insert, next) > 0) {
+		struct bkey k1 = bkey_unpack_key(b, insert);
+		struct bkey k2 = bkey_unpack_key(b, next);
+
+		bch2_dump_btree_node(NULL, b);
+		bch2_bkey_to_text(&buf1, &k1);
+		bch2_bkey_to_text(&buf2, &k2);
+
+		panic("insert > next:\n"
+		      "insert  key %s\n"
+		      "next    key %s\n",
+		      buf1.buf, buf2.buf);
+	}
+#endif
+}
+
+#else
+
+static inline void bch2_btree_node_iter_next_check(struct btree_node_iter *iter,
+						   struct btree *b) {}
+
+#endif
+
+/* Auxiliary search trees */
+
+#define BFLOAT_FAILED_UNPACKED	U8_MAX
+#define BFLOAT_FAILED		U8_MAX
+
+struct bkey_float {
+	u8		exponent;
+	u8		key_offset;
+	u16		mantissa;
+};
+#define BKEY_MANTISSA_BITS	16
+
+static unsigned bkey_float_byte_offset(unsigned idx)
+{
+	return idx * sizeof(struct bkey_float);
+}
+
+struct ro_aux_tree {
+	u8			nothing[0];
+	struct bkey_float	f[];
+};
+
+struct rw_aux_tree {
+	u16		offset;
+	struct bpos	k;
+};
+
+static unsigned bset_aux_tree_buf_end(const struct bset_tree *t)
+{
+	BUG_ON(t->aux_data_offset == U16_MAX);
+
+	switch (bset_aux_tree_type(t)) {
+	case BSET_NO_AUX_TREE:
+		return t->aux_data_offset;
+	case BSET_RO_AUX_TREE:
+		return t->aux_data_offset +
+			DIV_ROUND_UP(t->size * sizeof(struct bkey_float) +
+				     t->size * sizeof(u8), 8);
+	case BSET_RW_AUX_TREE:
+		return t->aux_data_offset +
+			DIV_ROUND_UP(sizeof(struct rw_aux_tree) * t->size, 8);
+	default:
+		BUG();
+	}
+}
+
+static unsigned bset_aux_tree_buf_start(const struct btree *b,
+					const struct bset_tree *t)
+{
+	return t == b->set
+		? DIV_ROUND_UP(b->unpack_fn_len, 8)
+		: bset_aux_tree_buf_end(t - 1);
+}
+
+static void *__aux_tree_base(const struct btree *b,
+			     const struct bset_tree *t)
+{
+	return b->aux_data + t->aux_data_offset * 8;
+}
+
+static struct ro_aux_tree *ro_aux_tree_base(const struct btree *b,
+					    const struct bset_tree *t)
+{
+	EBUG_ON(bset_aux_tree_type(t) != BSET_RO_AUX_TREE);
+
+	return __aux_tree_base(b, t);
+}
+
+static u8 *ro_aux_tree_prev(const struct btree *b,
+			    const struct bset_tree *t)
+{
+	EBUG_ON(bset_aux_tree_type(t) != BSET_RO_AUX_TREE);
+
+	return __aux_tree_base(b, t) + bkey_float_byte_offset(t->size);
+}
+
+static struct bkey_float *bkey_float(const struct btree *b,
+				     const struct bset_tree *t,
+				     unsigned idx)
+{
+	return ro_aux_tree_base(b, t)->f + idx;
+}
+
+static void bset_aux_tree_verify(const struct btree *b)
+{
+#ifdef CONFIG_BCACHEFS_DEBUG
+	const struct bset_tree *t;
+
+	for_each_bset(b, t) {
+		if (t->aux_data_offset == U16_MAX)
+			continue;
+
+		BUG_ON(t != b->set &&
+		       t[-1].aux_data_offset == U16_MAX);
+
+		BUG_ON(t->aux_data_offset < bset_aux_tree_buf_start(b, t));
+		BUG_ON(t->aux_data_offset > btree_aux_data_u64s(b));
+		BUG_ON(bset_aux_tree_buf_end(t) > btree_aux_data_u64s(b));
+	}
+#endif
+}
+
+void bch2_btree_keys_init(struct btree *b)
+{
+	unsigned i;
+
+	b->nsets		= 0;
+	memset(&b->nr, 0, sizeof(b->nr));
+
+	for (i = 0; i < MAX_BSETS; i++)
+		b->set[i].data_offset = U16_MAX;
+
+	bch2_bset_set_no_aux_tree(b, b->set);
+}
+
+/* Binary tree stuff for auxiliary search trees */
+
+/*
+ * Cacheline/offset <-> bkey pointer arithmetic:
+ *
+ * t->tree is a binary search tree in an array; each node corresponds to a key
+ * in one cacheline in t->set (BSET_CACHELINE bytes).
+ *
+ * This means we don't have to store the full index of the key that a node in
+ * the binary tree points to; eytzinger1_to_inorder() gives us the cacheline, and
+ * then bkey_float->m gives us the offset within that cacheline, in units of 8
+ * bytes.
+ *
+ * cacheline_to_bkey() and friends abstract out all the pointer arithmetic to
+ * make this work.
+ *
+ * To construct the bfloat for an arbitrary key we need to know what the key
+ * immediately preceding it is: we have to check if the two keys differ in the
+ * bits we're going to store in bkey_float->mantissa. t->prev[j] stores the size
+ * of the previous key so we can walk backwards to it from t->tree[j]'s key.
+ */
+
+static inline void *bset_cacheline(const struct btree *b,
+				   const struct bset_tree *t,
+				   unsigned cacheline)
+{
+	return (void *) round_down((unsigned long) btree_bkey_first(b, t),
+				   L1_CACHE_BYTES) +
+		cacheline * BSET_CACHELINE;
+}
+
+static struct bkey_packed *cacheline_to_bkey(const struct btree *b,
+					     const struct bset_tree *t,
+					     unsigned cacheline,
+					     unsigned offset)
+{
+	return bset_cacheline(b, t, cacheline) + offset * 8;
+}
+
+static unsigned bkey_to_cacheline(const struct btree *b,
+				  const struct bset_tree *t,
+				  const struct bkey_packed *k)
+{
+	return ((void *) k - bset_cacheline(b, t, 0)) / BSET_CACHELINE;
+}
+
+static ssize_t __bkey_to_cacheline_offset(const struct btree *b,
+					  const struct bset_tree *t,
+					  unsigned cacheline,
+					  const struct bkey_packed *k)
+{
+	return (u64 *) k - (u64 *) bset_cacheline(b, t, cacheline);
+}
+
+static unsigned bkey_to_cacheline_offset(const struct btree *b,
+					 const struct bset_tree *t,
+					 unsigned cacheline,
+					 const struct bkey_packed *k)
+{
+	size_t m = __bkey_to_cacheline_offset(b, t, cacheline, k);
+
+	EBUG_ON(m > U8_MAX);
+	return m;
+}
+
+static inline struct bkey_packed *tree_to_bkey(const struct btree *b,
+					       const struct bset_tree *t,
+					       unsigned j)
+{
+	return cacheline_to_bkey(b, t,
+			__eytzinger1_to_inorder(j, t->size - 1, t->extra),
+			bkey_float(b, t, j)->key_offset);
+}
+
+static struct bkey_packed *tree_to_prev_bkey(const struct btree *b,
+					     const struct bset_tree *t,
+					     unsigned j)
+{
+	unsigned prev_u64s = ro_aux_tree_prev(b, t)[j];
+
+	return (void *) ((u64 *) tree_to_bkey(b, t, j)->_data - prev_u64s);
+}
+
+static struct rw_aux_tree *rw_aux_tree(const struct btree *b,
+				       const struct bset_tree *t)
+{
+	EBUG_ON(bset_aux_tree_type(t) != BSET_RW_AUX_TREE);
+
+	return __aux_tree_base(b, t);
+}
+
+/*
+ * For the write set - the one we're currently inserting keys into - we don't
+ * maintain a full search tree, we just keep a simple lookup table in t->prev.
+ */
+static struct bkey_packed *rw_aux_to_bkey(const struct btree *b,
+					  struct bset_tree *t,
+					  unsigned j)
+{
+	return __btree_node_offset_to_key(b, rw_aux_tree(b, t)[j].offset);
+}
+
+static void rw_aux_tree_set(const struct btree *b, struct bset_tree *t,
+			    unsigned j, struct bkey_packed *k)
+{
+	EBUG_ON(k >= btree_bkey_last(b, t));
+
+	rw_aux_tree(b, t)[j] = (struct rw_aux_tree) {
+		.offset	= __btree_node_key_to_offset(b, k),
+		.k	= bkey_unpack_pos(b, k),
+	};
+}
+
+static void bch2_bset_verify_rw_aux_tree(struct btree *b,
+					struct bset_tree *t)
+{
+	struct bkey_packed *k = btree_bkey_first(b, t);
+	unsigned j = 0;
+
+	if (!bch2_expensive_debug_checks)
+		return;
+
+	BUG_ON(bset_has_ro_aux_tree(t));
+
+	if (!bset_has_rw_aux_tree(t))
+		return;
+
+	BUG_ON(t->size < 1);
+	BUG_ON(rw_aux_to_bkey(b, t, j) != k);
+
+	goto start;
+	while (1) {
+		if (rw_aux_to_bkey(b, t, j) == k) {
+			BUG_ON(!bpos_eq(rw_aux_tree(b, t)[j].k,
+					bkey_unpack_pos(b, k)));
+start:
+			if (++j == t->size)
+				break;
+
+			BUG_ON(rw_aux_tree(b, t)[j].offset <=
+			       rw_aux_tree(b, t)[j - 1].offset);
+		}
+
+		k = bkey_p_next(k);
+		BUG_ON(k >= btree_bkey_last(b, t));
+	}
+}
+
+/* returns idx of first entry >= offset: */
+static unsigned rw_aux_tree_bsearch(struct btree *b,
+				    struct bset_tree *t,
+				    unsigned offset)
+{
+	unsigned bset_offs = offset - btree_bkey_first_offset(t);
+	unsigned bset_u64s = t->end_offset - btree_bkey_first_offset(t);
+	unsigned idx = bset_u64s ? bset_offs * t->size / bset_u64s : 0;
+
+	EBUG_ON(bset_aux_tree_type(t) != BSET_RW_AUX_TREE);
+	EBUG_ON(!t->size);
+	EBUG_ON(idx > t->size);
+
+	while (idx < t->size &&
+	       rw_aux_tree(b, t)[idx].offset < offset)
+		idx++;
+
+	while (idx &&
+	       rw_aux_tree(b, t)[idx - 1].offset >= offset)
+		idx--;
+
+	EBUG_ON(idx < t->size &&
+		rw_aux_tree(b, t)[idx].offset < offset);
+	EBUG_ON(idx && rw_aux_tree(b, t)[idx - 1].offset >= offset);
+	EBUG_ON(idx + 1 < t->size &&
+		rw_aux_tree(b, t)[idx].offset ==
+		rw_aux_tree(b, t)[idx + 1].offset);
+
+	return idx;
+}
+
+static inline unsigned bkey_mantissa(const struct bkey_packed *k,
+				     const struct bkey_float *f,
+				     unsigned idx)
+{
+	u64 v;
+
+	EBUG_ON(!bkey_packed(k));
+
+	v = get_unaligned((u64 *) (((u8 *) k->_data) + (f->exponent >> 3)));
+
+	/*
+	 * In little endian, we're shifting off low bits (and then the bits we
+	 * want are at the low end), in big endian we're shifting off high bits
+	 * (and then the bits we want are at the high end, so we shift them
+	 * back down):
+	 */
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+	v >>= f->exponent & 7;
+#else
+	v >>= 64 - (f->exponent & 7) - BKEY_MANTISSA_BITS;
+#endif
+	return (u16) v;
+}
+
+static __always_inline void make_bfloat(struct btree *b, struct bset_tree *t,
+					unsigned j,
+					struct bkey_packed *min_key,
+					struct bkey_packed *max_key)
+{
+	struct bkey_float *f = bkey_float(b, t, j);
+	struct bkey_packed *m = tree_to_bkey(b, t, j);
+	struct bkey_packed *l = is_power_of_2(j)
+		? min_key
+		: tree_to_prev_bkey(b, t, j >> ffs(j));
+	struct bkey_packed *r = is_power_of_2(j + 1)
+		? max_key
+		: tree_to_bkey(b, t, j >> (ffz(j) + 1));
+	unsigned mantissa;
+	int shift, exponent, high_bit;
+
+	/*
+	 * for failed bfloats, the lookup code falls back to comparing against
+	 * the original key.
+	 */
+
+	if (!bkey_packed(l) || !bkey_packed(r) || !bkey_packed(m) ||
+	    !b->nr_key_bits) {
+		f->exponent = BFLOAT_FAILED_UNPACKED;
+		return;
+	}
+
+	/*
+	 * The greatest differing bit of l and r is the first bit we must
+	 * include in the bfloat mantissa we're creating in order to do
+	 * comparisons - that bit always becomes the high bit of
+	 * bfloat->mantissa, and thus the exponent we're calculating here is
+	 * the position of what will become the low bit in bfloat->mantissa:
+	 *
+	 * Note that this may be negative - we may be running off the low end
+	 * of the key: we handle this later:
+	 */
+	high_bit = max(bch2_bkey_greatest_differing_bit(b, l, r),
+		       min_t(unsigned, BKEY_MANTISSA_BITS, b->nr_key_bits) - 1);
+	exponent = high_bit - (BKEY_MANTISSA_BITS - 1);
+
+	/*
+	 * Then we calculate the actual shift value, from the start of the key
+	 * (k->_data), to get the key bits starting at exponent:
+	 */
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+	shift = (int) (b->format.key_u64s * 64 - b->nr_key_bits) + exponent;
+
+	EBUG_ON(shift + BKEY_MANTISSA_BITS > b->format.key_u64s * 64);
+#else
+	shift = high_bit_offset +
+		b->nr_key_bits -
+		exponent -
+		BKEY_MANTISSA_BITS;
+
+	EBUG_ON(shift < KEY_PACKED_BITS_START);
+#endif
+	EBUG_ON(shift < 0 || shift >= BFLOAT_FAILED);
+
+	f->exponent = shift;
+	mantissa = bkey_mantissa(m, f, j);
+
+	/*
+	 * If we've got garbage bits, set them to all 1s - it's legal for the
+	 * bfloat to compare larger than the original key, but not smaller:
+	 */
+	if (exponent < 0)
+		mantissa |= ~(~0U << -exponent);
+
+	f->mantissa = mantissa;
+}
+
+/* bytes remaining - only valid for last bset: */
+static unsigned __bset_tree_capacity(const struct btree *b, const struct bset_tree *t)
+{
+	bset_aux_tree_verify(b);
+
+	return btree_aux_data_bytes(b) - t->aux_data_offset * sizeof(u64);
+}
+
+static unsigned bset_ro_tree_capacity(const struct btree *b, const struct bset_tree *t)
+{
+	return __bset_tree_capacity(b, t) /
+		(sizeof(struct bkey_float) + sizeof(u8));
+}
+
+static unsigned bset_rw_tree_capacity(const struct btree *b, const struct bset_tree *t)
+{
+	return __bset_tree_capacity(b, t) / sizeof(struct rw_aux_tree);
+}
+
+static noinline void __build_rw_aux_tree(struct btree *b, struct bset_tree *t)
+{
+	struct bkey_packed *k;
+
+	t->size = 1;
+	t->extra = BSET_RW_AUX_TREE_VAL;
+	rw_aux_tree(b, t)[0].offset =
+		__btree_node_key_to_offset(b, btree_bkey_first(b, t));
+
+	bset_tree_for_each_key(b, t, k) {
+		if (t->size == bset_rw_tree_capacity(b, t))
+			break;
+
+		if ((void *) k - (void *) rw_aux_to_bkey(b, t, t->size - 1) >
+		    L1_CACHE_BYTES)
+			rw_aux_tree_set(b, t, t->size++, k);
+	}
+}
+
+static noinline void __build_ro_aux_tree(struct btree *b, struct bset_tree *t)
+{
+	struct bkey_packed *prev = NULL, *k = btree_bkey_first(b, t);
+	struct bkey_i min_key, max_key;
+	unsigned j, cacheline = 1;
+
+	t->size = min(bkey_to_cacheline(b, t, btree_bkey_last(b, t)),
+		      bset_ro_tree_capacity(b, t));
+retry:
+	if (t->size < 2) {
+		t->size = 0;
+		t->extra = BSET_NO_AUX_TREE_VAL;
+		return;
+	}
+
+	t->extra = (t->size - rounddown_pow_of_two(t->size - 1)) << 1;
+
+	/* First we figure out where the first key in each cacheline is */
+	eytzinger1_for_each(j, t->size - 1) {
+		while (bkey_to_cacheline(b, t, k) < cacheline)
+			prev = k, k = bkey_p_next(k);
+
+		if (k >= btree_bkey_last(b, t)) {
+			/* XXX: this path sucks */
+			t->size--;
+			goto retry;
+		}
+
+		ro_aux_tree_prev(b, t)[j] = prev->u64s;
+		bkey_float(b, t, j)->key_offset =
+			bkey_to_cacheline_offset(b, t, cacheline++, k);
+
+		EBUG_ON(tree_to_prev_bkey(b, t, j) != prev);
+		EBUG_ON(tree_to_bkey(b, t, j) != k);
+	}
+
+	while (k != btree_bkey_last(b, t))
+		prev = k, k = bkey_p_next(k);
+
+	if (!bkey_pack_pos(bkey_to_packed(&min_key), b->data->min_key, b)) {
+		bkey_init(&min_key.k);
+		min_key.k.p = b->data->min_key;
+	}
+
+	if (!bkey_pack_pos(bkey_to_packed(&max_key), b->data->max_key, b)) {
+		bkey_init(&max_key.k);
+		max_key.k.p = b->data->max_key;
+	}
+
+	/* Then we build the tree */
+	eytzinger1_for_each(j, t->size - 1)
+		make_bfloat(b, t, j,
+			    bkey_to_packed(&min_key),
+			    bkey_to_packed(&max_key));
+}
+
+static void bset_alloc_tree(struct btree *b, struct bset_tree *t)
+{
+	struct bset_tree *i;
+
+	for (i = b->set; i != t; i++)
+		BUG_ON(bset_has_rw_aux_tree(i));
+
+	bch2_bset_set_no_aux_tree(b, t);
+
+	/* round up to next cacheline: */
+	t->aux_data_offset = round_up(bset_aux_tree_buf_start(b, t),
+				      SMP_CACHE_BYTES / sizeof(u64));
+
+	bset_aux_tree_verify(b);
+}
+
+void bch2_bset_build_aux_tree(struct btree *b, struct bset_tree *t,
+			     bool writeable)
+{
+	if (writeable
+	    ? bset_has_rw_aux_tree(t)
+	    : bset_has_ro_aux_tree(t))
+		return;
+
+	bset_alloc_tree(b, t);
+
+	if (!__bset_tree_capacity(b, t))
+		return;
+
+	if (writeable)
+		__build_rw_aux_tree(b, t);
+	else
+		__build_ro_aux_tree(b, t);
+
+	bset_aux_tree_verify(b);
+}
+
+void bch2_bset_init_first(struct btree *b, struct bset *i)
+{
+	struct bset_tree *t;
+
+	BUG_ON(b->nsets);
+
+	memset(i, 0, sizeof(*i));
+	get_random_bytes(&i->seq, sizeof(i->seq));
+	SET_BSET_BIG_ENDIAN(i, CPU_BIG_ENDIAN);
+
+	t = &b->set[b->nsets++];
+	set_btree_bset(b, t, i);
+}
+
+void bch2_bset_init_next(struct bch_fs *c, struct btree *b,
+			 struct btree_node_entry *bne)
+{
+	struct bset *i = &bne->keys;
+	struct bset_tree *t;
+
+	BUG_ON(bset_byte_offset(b, bne) >= btree_bytes(c));
+	BUG_ON((void *) bne < (void *) btree_bkey_last(b, bset_tree_last(b)));
+	BUG_ON(b->nsets >= MAX_BSETS);
+
+	memset(i, 0, sizeof(*i));
+	i->seq = btree_bset_first(b)->seq;
+	SET_BSET_BIG_ENDIAN(i, CPU_BIG_ENDIAN);
+
+	t = &b->set[b->nsets++];
+	set_btree_bset(b, t, i);
+}
+
+/*
+ * find _some_ key in the same bset as @k that precedes @k - not necessarily the
+ * immediate predecessor:
+ */
+static struct bkey_packed *__bkey_prev(struct btree *b, struct bset_tree *t,
+				       struct bkey_packed *k)
+{
+	struct bkey_packed *p;
+	unsigned offset;
+	int j;
+
+	EBUG_ON(k < btree_bkey_first(b, t) ||
+		k > btree_bkey_last(b, t));
+
+	if (k == btree_bkey_first(b, t))
+		return NULL;
+
+	switch (bset_aux_tree_type(t)) {
+	case BSET_NO_AUX_TREE:
+		p = btree_bkey_first(b, t);
+		break;
+	case BSET_RO_AUX_TREE:
+		j = min_t(unsigned, t->size - 1, bkey_to_cacheline(b, t, k));
+
+		do {
+			p = j ? tree_to_bkey(b, t,
+					__inorder_to_eytzinger1(j--,
+							t->size - 1, t->extra))
+			      : btree_bkey_first(b, t);
+		} while (p >= k);
+		break;
+	case BSET_RW_AUX_TREE:
+		offset = __btree_node_key_to_offset(b, k);
+		j = rw_aux_tree_bsearch(b, t, offset);
+		p = j ? rw_aux_to_bkey(b, t, j - 1)
+		      : btree_bkey_first(b, t);
+		break;
+	}
+
+	return p;
+}
+
+struct bkey_packed *bch2_bkey_prev_filter(struct btree *b,
+					  struct bset_tree *t,
+					  struct bkey_packed *k,
+					  unsigned min_key_type)
+{
+	struct bkey_packed *p, *i, *ret = NULL, *orig_k = k;
+
+	while ((p = __bkey_prev(b, t, k)) && !ret) {
+		for (i = p; i != k; i = bkey_p_next(i))
+			if (i->type >= min_key_type)
+				ret = i;
+
+		k = p;
+	}
+
+	if (bch2_expensive_debug_checks) {
+		BUG_ON(ret >= orig_k);
+
+		for (i = ret
+			? bkey_p_next(ret)
+			: btree_bkey_first(b, t);
+		     i != orig_k;
+		     i = bkey_p_next(i))
+			BUG_ON(i->type >= min_key_type);
+	}
+
+	return ret;
+}
+
+/* Insert */
+
+static void bch2_bset_fix_lookup_table(struct btree *b,
+				       struct bset_tree *t,
+				       struct bkey_packed *_where,
+				       unsigned clobber_u64s,
+				       unsigned new_u64s)
+{
+	int shift = new_u64s - clobber_u64s;
+	unsigned l, j, where = __btree_node_key_to_offset(b, _where);
+
+	EBUG_ON(bset_has_ro_aux_tree(t));
+
+	if (!bset_has_rw_aux_tree(t))
+		return;
+
+	/* returns first entry >= where */
+	l = rw_aux_tree_bsearch(b, t, where);
+
+	if (!l) /* never delete first entry */
+		l++;
+	else if (l < t->size &&
+		 where < t->end_offset &&
+		 rw_aux_tree(b, t)[l].offset == where)
+		rw_aux_tree_set(b, t, l++, _where);
+
+	/* l now > where */
+
+	for (j = l;
+	     j < t->size &&
+	     rw_aux_tree(b, t)[j].offset < where + clobber_u64s;
+	     j++)
+		;
+
+	if (j < t->size &&
+	    rw_aux_tree(b, t)[j].offset + shift ==
+	    rw_aux_tree(b, t)[l - 1].offset)
+		j++;
+
+	memmove(&rw_aux_tree(b, t)[l],
+		&rw_aux_tree(b, t)[j],
+		(void *) &rw_aux_tree(b, t)[t->size] -
+		(void *) &rw_aux_tree(b, t)[j]);
+	t->size -= j - l;
+
+	for (j = l; j < t->size; j++)
+		rw_aux_tree(b, t)[j].offset += shift;
+
+	EBUG_ON(l < t->size &&
+		rw_aux_tree(b, t)[l].offset ==
+		rw_aux_tree(b, t)[l - 1].offset);
+
+	if (t->size < bset_rw_tree_capacity(b, t) &&
+	    (l < t->size
+	     ? rw_aux_tree(b, t)[l].offset
+	     : t->end_offset) -
+	    rw_aux_tree(b, t)[l - 1].offset >
+	    L1_CACHE_BYTES / sizeof(u64)) {
+		struct bkey_packed *start = rw_aux_to_bkey(b, t, l - 1);
+		struct bkey_packed *end = l < t->size
+			? rw_aux_to_bkey(b, t, l)
+			: btree_bkey_last(b, t);
+		struct bkey_packed *k = start;
+
+		while (1) {
+			k = bkey_p_next(k);
+			if (k == end)
+				break;
+
+			if ((void *) k - (void *) start >= L1_CACHE_BYTES) {
+				memmove(&rw_aux_tree(b, t)[l + 1],
+					&rw_aux_tree(b, t)[l],
+					(void *) &rw_aux_tree(b, t)[t->size] -
+					(void *) &rw_aux_tree(b, t)[l]);
+				t->size++;
+				rw_aux_tree_set(b, t, l, k);
+				break;
+			}
+		}
+	}
+
+	bch2_bset_verify_rw_aux_tree(b, t);
+	bset_aux_tree_verify(b);
+}
+
+void bch2_bset_insert(struct btree *b,
+		      struct btree_node_iter *iter,
+		      struct bkey_packed *where,
+		      struct bkey_i *insert,
+		      unsigned clobber_u64s)
+{
+	struct bkey_format *f = &b->format;
+	struct bset_tree *t = bset_tree_last(b);
+	struct bkey_packed packed, *src = bkey_to_packed(insert);
+
+	bch2_bset_verify_rw_aux_tree(b, t);
+	bch2_verify_insert_pos(b, where, bkey_to_packed(insert), clobber_u64s);
+
+	if (bch2_bkey_pack_key(&packed, &insert->k, f))
+		src = &packed;
+
+	if (!bkey_deleted(&insert->k))
+		btree_keys_account_key_add(&b->nr, t - b->set, src);
+
+	if (src->u64s != clobber_u64s) {
+		u64 *src_p = (u64 *) where->_data + clobber_u64s;
+		u64 *dst_p = (u64 *) where->_data + src->u64s;
+
+		EBUG_ON((int) le16_to_cpu(bset(b, t)->u64s) <
+			(int) clobber_u64s - src->u64s);
+
+		memmove_u64s(dst_p, src_p, btree_bkey_last(b, t)->_data - src_p);
+		le16_add_cpu(&bset(b, t)->u64s, src->u64s - clobber_u64s);
+		set_btree_bset_end(b, t);
+	}
+
+	memcpy_u64s_small(where, src,
+		    bkeyp_key_u64s(f, src));
+	memcpy_u64s(bkeyp_val(f, where), &insert->v,
+		    bkeyp_val_u64s(f, src));
+
+	if (src->u64s != clobber_u64s)
+		bch2_bset_fix_lookup_table(b, t, where, clobber_u64s, src->u64s);
+
+	bch2_verify_btree_nr_keys(b);
+}
+
+void bch2_bset_delete(struct btree *b,
+		      struct bkey_packed *where,
+		      unsigned clobber_u64s)
+{
+	struct bset_tree *t = bset_tree_last(b);
+	u64 *src_p = (u64 *) where->_data + clobber_u64s;
+	u64 *dst_p = where->_data;
+
+	bch2_bset_verify_rw_aux_tree(b, t);
+
+	EBUG_ON(le16_to_cpu(bset(b, t)->u64s) < clobber_u64s);
+
+	memmove_u64s_down(dst_p, src_p, btree_bkey_last(b, t)->_data - src_p);
+	le16_add_cpu(&bset(b, t)->u64s, -clobber_u64s);
+	set_btree_bset_end(b, t);
+
+	bch2_bset_fix_lookup_table(b, t, where, clobber_u64s, 0);
+}
+
+/* Lookup */
+
+__flatten
+static struct bkey_packed *bset_search_write_set(const struct btree *b,
+				struct bset_tree *t,
+				struct bpos *search)
+{
+	unsigned l = 0, r = t->size;
+
+	while (l + 1 != r) {
+		unsigned m = (l + r) >> 1;
+
+		if (bpos_lt(rw_aux_tree(b, t)[m].k, *search))
+			l = m;
+		else
+			r = m;
+	}
+
+	return rw_aux_to_bkey(b, t, l);
+}
+
+static inline void prefetch_four_cachelines(void *p)
+{
+#ifdef CONFIG_X86_64
+	asm("prefetcht0 (-127 + 64 * 0)(%0);"
+	    "prefetcht0 (-127 + 64 * 1)(%0);"
+	    "prefetcht0 (-127 + 64 * 2)(%0);"
+	    "prefetcht0 (-127 + 64 * 3)(%0);"
+	    :
+	    : "r" (p + 127));
+#else
+	prefetch(p + L1_CACHE_BYTES * 0);
+	prefetch(p + L1_CACHE_BYTES * 1);
+	prefetch(p + L1_CACHE_BYTES * 2);
+	prefetch(p + L1_CACHE_BYTES * 3);
+#endif
+}
+
+static inline bool bkey_mantissa_bits_dropped(const struct btree *b,
+					      const struct bkey_float *f,
+					      unsigned idx)
+{
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+	unsigned key_bits_start = b->format.key_u64s * 64 - b->nr_key_bits;
+
+	return f->exponent > key_bits_start;
+#else
+	unsigned key_bits_end = high_bit_offset + b->nr_key_bits;
+
+	return f->exponent + BKEY_MANTISSA_BITS < key_bits_end;
+#endif
+}
+
+__flatten
+static struct bkey_packed *bset_search_tree(const struct btree *b,
+				const struct bset_tree *t,
+				const struct bpos *search,
+				const struct bkey_packed *packed_search)
+{
+	struct ro_aux_tree *base = ro_aux_tree_base(b, t);
+	struct bkey_float *f;
+	struct bkey_packed *k;
+	unsigned inorder, n = 1, l, r;
+	int cmp;
+
+	do {
+		if (likely(n << 4 < t->size))
+			prefetch(&base->f[n << 4]);
+
+		f = &base->f[n];
+		if (unlikely(f->exponent >= BFLOAT_FAILED))
+			goto slowpath;
+
+		l = f->mantissa;
+		r = bkey_mantissa(packed_search, f, n);
+
+		if (unlikely(l == r) && bkey_mantissa_bits_dropped(b, f, n))
+			goto slowpath;
+
+		n = n * 2 + (l < r);
+		continue;
+slowpath:
+		k = tree_to_bkey(b, t, n);
+		cmp = bkey_cmp_p_or_unp(b, k, packed_search, search);
+		if (!cmp)
+			return k;
+
+		n = n * 2 + (cmp < 0);
+	} while (n < t->size);
+
+	inorder = __eytzinger1_to_inorder(n >> 1, t->size - 1, t->extra);
+
+	/*
+	 * n would have been the node we recursed to - the low bit tells us if
+	 * we recursed left or recursed right.
+	 */
+	if (likely(!(n & 1))) {
+		--inorder;
+		if (unlikely(!inorder))
+			return btree_bkey_first(b, t);
+
+		f = &base->f[eytzinger1_prev(n >> 1, t->size - 1)];
+	}
+
+	return cacheline_to_bkey(b, t, inorder, f->key_offset);
+}
+
+static __always_inline __flatten
+struct bkey_packed *__bch2_bset_search(struct btree *b,
+				struct bset_tree *t,
+				struct bpos *search,
+				const struct bkey_packed *lossy_packed_search)
+{
+
+	/*
+	 * First, we search for a cacheline, then lastly we do a linear search
+	 * within that cacheline.
+	 *
+	 * To search for the cacheline, there's three different possibilities:
+	 *  * The set is too small to have a search tree, so we just do a linear
+	 *    search over the whole set.
+	 *  * The set is the one we're currently inserting into; keeping a full
+	 *    auxiliary search tree up to date would be too expensive, so we
+	 *    use a much simpler lookup table to do a binary search -
+	 *    bset_search_write_set().
+	 *  * Or we use the auxiliary search tree we constructed earlier -
+	 *    bset_search_tree()
+	 */
+
+	switch (bset_aux_tree_type(t)) {
+	case BSET_NO_AUX_TREE:
+		return btree_bkey_first(b, t);
+	case BSET_RW_AUX_TREE:
+		return bset_search_write_set(b, t, search);
+	case BSET_RO_AUX_TREE:
+		return bset_search_tree(b, t, search, lossy_packed_search);
+	default:
+		BUG();
+	}
+}
+
+static __always_inline __flatten
+struct bkey_packed *bch2_bset_search_linear(struct btree *b,
+				struct bset_tree *t,
+				struct bpos *search,
+				struct bkey_packed *packed_search,
+				const struct bkey_packed *lossy_packed_search,
+				struct bkey_packed *m)
+{
+	if (lossy_packed_search)
+		while (m != btree_bkey_last(b, t) &&
+		       bkey_iter_cmp_p_or_unp(b, m,
+					lossy_packed_search, search) < 0)
+			m = bkey_p_next(m);
+
+	if (!packed_search)
+		while (m != btree_bkey_last(b, t) &&
+		       bkey_iter_pos_cmp(b, m, search) < 0)
+			m = bkey_p_next(m);
+
+	if (bch2_expensive_debug_checks) {
+		struct bkey_packed *prev = bch2_bkey_prev_all(b, t, m);
+
+		BUG_ON(prev &&
+		       bkey_iter_cmp_p_or_unp(b, prev,
+					packed_search, search) >= 0);
+	}
+
+	return m;
+}
+
+/* Btree node iterator */
+
+static inline void __bch2_btree_node_iter_push(struct btree_node_iter *iter,
+			      struct btree *b,
+			      const struct bkey_packed *k,
+			      const struct bkey_packed *end)
+{
+	if (k != end) {
+		struct btree_node_iter_set *pos;
+
+		btree_node_iter_for_each(iter, pos)
+			;
+
+		BUG_ON(pos >= iter->data + ARRAY_SIZE(iter->data));
+		*pos = (struct btree_node_iter_set) {
+			__btree_node_key_to_offset(b, k),
+			__btree_node_key_to_offset(b, end)
+		};
+	}
+}
+
+void bch2_btree_node_iter_push(struct btree_node_iter *iter,
+			       struct btree *b,
+			       const struct bkey_packed *k,
+			       const struct bkey_packed *end)
+{
+	__bch2_btree_node_iter_push(iter, b, k, end);
+	bch2_btree_node_iter_sort(iter, b);
+}
+
+noinline __flatten __cold
+static void btree_node_iter_init_pack_failed(struct btree_node_iter *iter,
+			      struct btree *b, struct bpos *search)
+{
+	struct bkey_packed *k;
+
+	trace_bkey_pack_pos_fail(search);
+
+	bch2_btree_node_iter_init_from_start(iter, b);
+
+	while ((k = bch2_btree_node_iter_peek(iter, b)) &&
+	       bkey_iter_pos_cmp(b, k, search) < 0)
+		bch2_btree_node_iter_advance(iter, b);
+}
+
+/**
+ * bch2_btree_node_iter_init - initialize a btree node iterator, starting from a
+ * given position
+ *
+ * @iter:	iterator to initialize
+ * @b:		btree node to search
+ * @search:	search key
+ *
+ * Main entry point to the lookup code for individual btree nodes:
+ *
+ * NOTE:
+ *
+ * When you don't filter out deleted keys, btree nodes _do_ contain duplicate
+ * keys. This doesn't matter for most code, but it does matter for lookups.
+ *
+ * Some adjacent keys with a string of equal keys:
+ *	i j k k k k l m
+ *
+ * If you search for k, the lookup code isn't guaranteed to return you any
+ * specific k. The lookup code is conceptually doing a binary search and
+ * iterating backwards is very expensive so if the pivot happens to land at the
+ * last k that's what you'll get.
+ *
+ * This works out ok, but it's something to be aware of:
+ *
+ *  - For non extents, we guarantee that the live key comes last - see
+ *    btree_node_iter_cmp(), keys_out_of_order(). So the duplicates you don't
+ *    see will only be deleted keys you don't care about.
+ *
+ *  - For extents, deleted keys sort last (see the comment at the top of this
+ *    file). But when you're searching for extents, you actually want the first
+ *    key strictly greater than your search key - an extent that compares equal
+ *    to the search key is going to have 0 sectors after the search key.
+ *
+ *    But this does mean that we can't just search for
+ *    bpos_successor(start_of_range) to get the first extent that overlaps with
+ *    the range we want - if we're unlucky and there's an extent that ends
+ *    exactly where we searched, then there could be a deleted key at the same
+ *    position and we'd get that when we search instead of the preceding extent
+ *    we needed.
+ *
+ *    So we've got to search for start_of_range, then after the lookup iterate
+ *    past any extents that compare equal to the position we searched for.
+ */
+__flatten
+void bch2_btree_node_iter_init(struct btree_node_iter *iter,
+			       struct btree *b, struct bpos *search)
+{
+	struct bkey_packed p, *packed_search = NULL;
+	struct btree_node_iter_set *pos = iter->data;
+	struct bkey_packed *k[MAX_BSETS];
+	unsigned i;
+
+	EBUG_ON(bpos_lt(*search, b->data->min_key));
+	EBUG_ON(bpos_gt(*search, b->data->max_key));
+	bset_aux_tree_verify(b);
+
+	memset(iter, 0, sizeof(*iter));
+
+	switch (bch2_bkey_pack_pos_lossy(&p, *search, b)) {
+	case BKEY_PACK_POS_EXACT:
+		packed_search = &p;
+		break;
+	case BKEY_PACK_POS_SMALLER:
+		packed_search = NULL;
+		break;
+	case BKEY_PACK_POS_FAIL:
+		btree_node_iter_init_pack_failed(iter, b, search);
+		return;
+	}
+
+	for (i = 0; i < b->nsets; i++) {
+		k[i] = __bch2_bset_search(b, b->set + i, search, &p);
+		prefetch_four_cachelines(k[i]);
+	}
+
+	for (i = 0; i < b->nsets; i++) {
+		struct bset_tree *t = b->set + i;
+		struct bkey_packed *end = btree_bkey_last(b, t);
+
+		k[i] = bch2_bset_search_linear(b, t, search,
+					       packed_search, &p, k[i]);
+		if (k[i] != end)
+			*pos++ = (struct btree_node_iter_set) {
+				__btree_node_key_to_offset(b, k[i]),
+				__btree_node_key_to_offset(b, end)
+			};
+	}
+
+	bch2_btree_node_iter_sort(iter, b);
+}
+
+void bch2_btree_node_iter_init_from_start(struct btree_node_iter *iter,
+					  struct btree *b)
+{
+	struct bset_tree *t;
+
+	memset(iter, 0, sizeof(*iter));
+
+	for_each_bset(b, t)
+		__bch2_btree_node_iter_push(iter, b,
+					   btree_bkey_first(b, t),
+					   btree_bkey_last(b, t));
+	bch2_btree_node_iter_sort(iter, b);
+}
+
+struct bkey_packed *bch2_btree_node_iter_bset_pos(struct btree_node_iter *iter,
+						  struct btree *b,
+						  struct bset_tree *t)
+{
+	struct btree_node_iter_set *set;
+
+	btree_node_iter_for_each(iter, set)
+		if (set->end == t->end_offset)
+			return __btree_node_offset_to_key(b, set->k);
+
+	return btree_bkey_last(b, t);
+}
+
+static inline bool btree_node_iter_sort_two(struct btree_node_iter *iter,
+					    struct btree *b,
+					    unsigned first)
+{
+	bool ret;
+
+	if ((ret = (btree_node_iter_cmp(b,
+					iter->data[first],
+					iter->data[first + 1]) > 0)))
+		swap(iter->data[first], iter->data[first + 1]);
+	return ret;
+}
+
+void bch2_btree_node_iter_sort(struct btree_node_iter *iter,
+			       struct btree *b)
+{
+	/* unrolled bubble sort: */
+
+	if (!__btree_node_iter_set_end(iter, 2)) {
+		btree_node_iter_sort_two(iter, b, 0);
+		btree_node_iter_sort_two(iter, b, 1);
+	}
+
+	if (!__btree_node_iter_set_end(iter, 1))
+		btree_node_iter_sort_two(iter, b, 0);
+}
+
+void bch2_btree_node_iter_set_drop(struct btree_node_iter *iter,
+				   struct btree_node_iter_set *set)
+{
+	struct btree_node_iter_set *last =
+		iter->data + ARRAY_SIZE(iter->data) - 1;
+
+	memmove(&set[0], &set[1], (void *) last - (void *) set);
+	*last = (struct btree_node_iter_set) { 0, 0 };
+}
+
+static inline void __bch2_btree_node_iter_advance(struct btree_node_iter *iter,
+						  struct btree *b)
+{
+	iter->data->k += __bch2_btree_node_iter_peek_all(iter, b)->u64s;
+
+	EBUG_ON(iter->data->k > iter->data->end);
+
+	if (unlikely(__btree_node_iter_set_end(iter, 0))) {
+		/* avoid an expensive memmove call: */
+		iter->data[0] = iter->data[1];
+		iter->data[1] = iter->data[2];
+		iter->data[2] = (struct btree_node_iter_set) { 0, 0 };
+		return;
+	}
+
+	if (__btree_node_iter_set_end(iter, 1))
+		return;
+
+	if (!btree_node_iter_sort_two(iter, b, 0))
+		return;
+
+	if (__btree_node_iter_set_end(iter, 2))
+		return;
+
+	btree_node_iter_sort_two(iter, b, 1);
+}
+
+void bch2_btree_node_iter_advance(struct btree_node_iter *iter,
+				  struct btree *b)
+{
+	if (bch2_expensive_debug_checks) {
+		bch2_btree_node_iter_verify(iter, b);
+		bch2_btree_node_iter_next_check(iter, b);
+	}
+
+	__bch2_btree_node_iter_advance(iter, b);
+}
+
+/*
+ * Expensive:
+ */
+struct bkey_packed *bch2_btree_node_iter_prev_all(struct btree_node_iter *iter,
+						  struct btree *b)
+{
+	struct bkey_packed *k, *prev = NULL;
+	struct btree_node_iter_set *set;
+	struct bset_tree *t;
+	unsigned end = 0;
+
+	if (bch2_expensive_debug_checks)
+		bch2_btree_node_iter_verify(iter, b);
+
+	for_each_bset(b, t) {
+		k = bch2_bkey_prev_all(b, t,
+			bch2_btree_node_iter_bset_pos(iter, b, t));
+		if (k &&
+		    (!prev || bkey_iter_cmp(b, k, prev) > 0)) {
+			prev = k;
+			end = t->end_offset;
+		}
+	}
+
+	if (!prev)
+		return NULL;
+
+	/*
+	 * We're manually memmoving instead of just calling sort() to ensure the
+	 * prev we picked ends up in slot 0 - sort won't necessarily put it
+	 * there because of duplicate deleted keys:
+	 */
+	btree_node_iter_for_each(iter, set)
+		if (set->end == end)
+			goto found;
+
+	BUG_ON(set != &iter->data[__btree_node_iter_used(iter)]);
+found:
+	BUG_ON(set >= iter->data + ARRAY_SIZE(iter->data));
+
+	memmove(&iter->data[1],
+		&iter->data[0],
+		(void *) set - (void *) &iter->data[0]);
+
+	iter->data[0].k = __btree_node_key_to_offset(b, prev);
+	iter->data[0].end = end;
+
+	if (bch2_expensive_debug_checks)
+		bch2_btree_node_iter_verify(iter, b);
+	return prev;
+}
+
+struct bkey_packed *bch2_btree_node_iter_prev(struct btree_node_iter *iter,
+					      struct btree *b)
+{
+	struct bkey_packed *prev;
+
+	do {
+		prev = bch2_btree_node_iter_prev_all(iter, b);
+	} while (prev && bkey_deleted(prev));
+
+	return prev;
+}
+
+struct bkey_s_c bch2_btree_node_iter_peek_unpack(struct btree_node_iter *iter,
+						 struct btree *b,
+						 struct bkey *u)
+{
+	struct bkey_packed *k = bch2_btree_node_iter_peek(iter, b);
+
+	return k ? bkey_disassemble(b, k, u) : bkey_s_c_null;
+}
+
+/* Mergesort */
+
+void bch2_btree_keys_stats(const struct btree *b, struct bset_stats *stats)
+{
+	const struct bset_tree *t;
+
+	for_each_bset(b, t) {
+		enum bset_aux_tree_type type = bset_aux_tree_type(t);
+		size_t j;
+
+		stats->sets[type].nr++;
+		stats->sets[type].bytes += le16_to_cpu(bset(b, t)->u64s) *
+			sizeof(u64);
+
+		if (bset_has_ro_aux_tree(t)) {
+			stats->floats += t->size - 1;
+
+			for (j = 1; j < t->size; j++)
+				stats->failed +=
+					bkey_float(b, t, j)->exponent ==
+					BFLOAT_FAILED;
+		}
+	}
+}
+
+void bch2_bfloat_to_text(struct printbuf *out, struct btree *b,
+			 struct bkey_packed *k)
+{
+	struct bset_tree *t = bch2_bkey_to_bset(b, k);
+	struct bkey uk;
+	unsigned j, inorder;
+
+	if (!bset_has_ro_aux_tree(t))
+		return;
+
+	inorder = bkey_to_cacheline(b, t, k);
+	if (!inorder || inorder >= t->size)
+		return;
+
+	j = __inorder_to_eytzinger1(inorder, t->size - 1, t->extra);
+	if (k != tree_to_bkey(b, t, j))
+		return;
+
+	switch (bkey_float(b, t, j)->exponent) {
+	case BFLOAT_FAILED:
+		uk = bkey_unpack_key(b, k);
+		prt_printf(out,
+		       "    failed unpacked at depth %u\n"
+		       "\t",
+		       ilog2(j));
+		bch2_bpos_to_text(out, uk.p);
+		prt_printf(out, "\n");
+		break;
+	}
+}