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

// 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 "util.h"

#include <asm/unaligned.h>
#include <linux/console.h>
#include <linux/random.h>
#include <linux/prefetch.h>

/* hack.. */
#include "alloc_types.h"
#include <trace/events/bcachefs.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)
{
        unsigned offset = __btree_node_key_to_offset(b, k);
        struct bset_tree *t;

        for_each_bset(b, t)
                if (offset <= t->end_offset) {
                        EBUG_ON(offset < btree_bkey_first_offset(t));
                        return t;
                }

        BUG();
}

/*
 * 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 btree *b, struct bset *i, unsigned set)
{
        struct bkey_packed *_k, *_n;
        struct bkey k, n;
        char buf[120];

        if (!i->u64s)
                return;

        for (_k = i->start, k = bkey_unpack_key(b, _k);
             _k < vstruct_last(i);
             _k = _n, k = n) {
                _n = bkey_next(_k);

                bch2_bkey_to_text(&PBUF(buf), &k);
                printk(KERN_ERR "block %u key %5u: %s\n", set,
                       __btree_node_key_to_offset(b, _k), buf);

                if (_n == vstruct_last(i))
                        continue;

                n = bkey_unpack_key(b, _n);

                if (bkey_cmp(bkey_start_pos(&n), k.p) < 0) {
                        printk(KERN_ERR "Key skipped backwards\n");
                        continue;
                }

                /*
                 * Weird check for duplicate non extent keys: extents are
                 * deleted iff they have 0 size, so if it has zero size and it's
                 * not deleted these aren't extents:
                 */
                if (((!k.size && !bkey_deleted(&k)) ||
                     (!n.size && !bkey_deleted(&n))) &&
                    !bkey_deleted(&k) &&
                    !bkey_cmp(n.p, k.p))
                        printk(KERN_ERR "Duplicate keys\n");
        }
}

void bch2_dump_btree_node(struct btree *b)
{
        struct bset_tree *t;

        console_lock();
        for_each_bset(b, t)
                bch2_dump_bset(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;

        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);
                char buf[100];

                bch2_bkey_to_text(&PBUF(buf), &uk);
                printk(KERN_ERR "set %zu key %u: %s\n",
                       t - b->set, set->k, 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)
                for (k = btree_bkey_first(b, t);
                     k != btree_bkey_last(b, t);
                     k = bkey_next(k))
                        if (!bkey_whiteout(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);
                char buf1[80], buf2[80];

                bch2_dump_btree_node(b);
                bch2_bkey_to_text(&PBUF(buf1), &ku);
                bch2_bkey_to_text(&PBUF(buf2), &nu);
                printk(KERN_ERR "out of order/overlapping:\n%s\n%s\n",
                       buf1, buf2);
                printk(KERN_ERR "iter was:");

                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);
                        printk(" [%zi %zi]", t - b->set,
                               k->_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)
                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 *) (where->_data + clobber_u64s);
#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);
                char buf1[100];
                char buf2[100];

                bch2_dump_btree_node(b);
                bch2_bkey_to_text(&PBUF(buf1), &k1);
                bch2_bkey_to_text(&PBUF(buf2), &k2);

                panic("prev > insert:\n"
                      "prev    key %5u %s\n"
                      "insert  key %5u %s\n",
                       __btree_node_key_to_offset(b, prev), buf1,
                       __btree_node_key_to_offset(b, insert), buf2);
        }
#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);
                char buf1[100];
                char buf2[100];

                bch2_dump_btree_node(b);
                bch2_bkey_to_text(&PBUF(buf1), &k1);
                bch2_bkey_to_text(&PBUF(buf2), &k2);

                panic("insert > next:\n"
                      "insert  key %5u %s\n"
                      "next    key %5u %s\n",
                       __btree_node_key_to_offset(b, insert), buf1,
                       __btree_node_key_to_offset(b, next), buf2);
        }
#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 {
        struct bkey_float       f[0];
};

struct rw_aux_tree {
        u16             offset;
        struct bpos     k;
};

/*
 * BSET_CACHELINE was originally intended to match the hardware cacheline size -
 * it used to be 64, but I realized the lookup code would touch slightly less
 * memory if it was 128.
 *
 * It definites the number of bytes (in struct bset) per struct bkey_float in
 * the auxiliar search tree - when we're done searching the bset_float tree we
 * have this many bytes left that we do a linear search over.
 *
 * Since (after level 5) every level of the bset_tree is on a new cacheline,
 * we're touching one fewer cacheline in the bset tree in exchange for one more
 * cacheline in the linear search - but the linear search might stop before it
 * gets to the second cacheline.
 */

#define BSET_CACHELINE          128

/* Space required for the btree node keys */
static inline size_t btree_keys_bytes(struct btree *b)
{
        return PAGE_SIZE << b->page_order;
}

static inline size_t btree_keys_cachelines(struct btree *b)
{
        return btree_keys_bytes(b) / BSET_CACHELINE;
}

static inline size_t btree_aux_data_bytes(struct btree *b)
{
        return btree_keys_cachelines(b) * 8;
}

static inline size_t btree_aux_data_u64s(struct btree *b)
{
        return btree_aux_data_bytes(b) / sizeof(u64);
}

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(struct btree *b)
{
#ifdef CONFIG_BCACHEFS_DEBUG
        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
}

/* Memory allocation */

void bch2_btree_keys_free(struct btree *b)
{
        vfree(b->aux_data);
        b->aux_data = NULL;
}

#ifndef PAGE_KERNEL_EXEC
# define PAGE_KERNEL_EXEC PAGE_KERNEL
#endif

int bch2_btree_keys_alloc(struct btree *b, unsigned page_order, gfp_t gfp)
{
        b->page_order   = page_order;
        b->aux_data     = __vmalloc(btree_aux_data_bytes(b), gfp,
                                    PAGE_KERNEL_EXEC);
        if (!b->aux_data)
                return -ENOMEM;

        return 0;
}

void bch2_btree_keys_init(struct btree *b, bool *expensive_debug_checks)
{
        unsigned i;

        b->nsets                = 0;
        memset(&b->nr, 0, sizeof(b->nr));
#ifdef CONFIG_BCACHEFS_DEBUG
        b->expensive_debug_checks = expensive_debug_checks;
#endif
        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, 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 *) (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 (!btree_keys_expensive_checks(b))
                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(bkey_cmp(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_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 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, *r;
        unsigned mantissa;
        int shift, exponent, high_bit;

        if (is_power_of_2(j)) {
                l = min_key;

                if (!l->u64s) {
                        if (!bkey_pack_pos(l, b->data->min_key, b)) {
                                struct bkey_i tmp;

                                bkey_init(&tmp.k);
                                tmp.k.p = b->data->min_key;
                                bkey_copy(l, &tmp);
                        }
                }
        } else {
                l = tree_to_prev_bkey(b, t, j >> ffs(j));

                EBUG_ON(m < l);
        }

        if (is_power_of_2(j + 1)) {
                r = max_key;

                if (!r->u64s) {
                        if (!bkey_pack_pos(r, t->max_key, b)) {
                                struct bkey_i tmp;

                                bkey_init(&tmp.k);
                                tmp.k.p = t->max_key;
                                bkey_copy(r, &tmp);
                        }
                }
        } else {
                r = tree_to_bkey(b, t, j >> (ffz(j) + 1));

                EBUG_ON(m > r);
        }

        /*
         * 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(struct btree *b, 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(struct btree *b, struct bset_tree *t)
{
        return __bset_tree_capacity(b, t) /
                (sizeof(struct bkey_float) + sizeof(u8));
}

static unsigned bset_rw_tree_capacity(struct btree *b, struct bset_tree *t)
{
        return __bset_tree_capacity(b, t) / sizeof(struct rw_aux_tree);
}

static 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));

        for (k = btree_bkey_first(b, t);
             k != btree_bkey_last(b, t);
             k = bkey_next(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 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_packed min_key, max_key;
        unsigned j, cacheline = 1;

        /* signal to make_bfloat() that they're uninitialized: */
        min_key.u64s = max_key.u64s = 0;

        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) {
                while (bkey_to_cacheline(b, t, k) < cacheline)
                        prev = k, k = bkey_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 (bkey_next(k) != btree_bkey_last(b, t))
                k = bkey_next(k);

        t->max_key = bkey_unpack_pos(b, k);

        /* Then we build the tree */
        eytzinger1_for_each(j, t->size)
                make_bfloat(b, t, j, &min_key, &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, 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_next(i))
                        if (i->type >= min_key_type)
                                ret = i;

                k = p;
        }

        if (btree_keys_expensive_checks(b)) {
                BUG_ON(ret >= orig_k);

                for (i = ret ? bkey_next(ret) : btree_bkey_first(b, t);
                     i != orig_k;
                     i = bkey_next(i))
                        BUG_ON(i->type >= min_key_type);
        }

        return ret;
}

/* Insert */

static void rw_aux_tree_fix_invalidated_key(struct btree *b,
                                            struct bset_tree *t,
                                            struct bkey_packed *k)
{
        unsigned offset = __btree_node_key_to_offset(b, k);
        unsigned j = rw_aux_tree_bsearch(b, t, offset);

        if (j < t->size &&
            rw_aux_tree(b, t)[j].offset == offset)
                rw_aux_tree_set(b, t, j, k);

        bch2_bset_verify_rw_aux_tree(b, t);
}

static void ro_aux_tree_fix_invalidated_key(struct btree *b,
                                            struct bset_tree *t,
                                            struct bkey_packed *k)
{
        struct bkey_packed min_key, max_key;
        unsigned inorder, j;

        EBUG_ON(bset_aux_tree_type(t) != BSET_RO_AUX_TREE);

        /* signal to make_bfloat() that they're uninitialized: */
        min_key.u64s = max_key.u64s = 0;

        if (bkey_next(k) == btree_bkey_last(b, t)) {
                t->max_key = bkey_unpack_pos(b, k);

                for (j = 1; j < t->size; j = j * 2 + 1)
                        make_bfloat(b, t, j, &min_key, &max_key);
        }

        inorder = bkey_to_cacheline(b, t, k);

        if (inorder &&
            inorder < t->size) {
                j = __inorder_to_eytzinger1(inorder, t->size, t->extra);

                if (k == tree_to_bkey(b, t, j)) {
                        /* Fix the node this key corresponds to */
                        make_bfloat(b, t, j, &min_key, &max_key);

                        /* Children for which this key is the right boundary */
                        for (j = eytzinger1_left_child(j);
                             j < t->size;
                             j = eytzinger1_right_child(j))
                                make_bfloat(b, t, j, &min_key, &max_key);
                }
        }

        if (inorder + 1 < t->size) {
                j = __inorder_to_eytzinger1(inorder + 1, t->size, t->extra);

                if (k == tree_to_prev_bkey(b, t, j)) {
                        make_bfloat(b, t, j, &min_key, &max_key);

                        /* Children for which this key is the left boundary */
                        for (j = eytzinger1_right_child(j);
                             j < t->size;
                             j = eytzinger1_left_child(j))
                                make_bfloat(b, t, j, &min_key, &max_key);
                }
        }
}

/**
 * bch2_bset_fix_invalidated_key() - given an existing  key @k that has been
 * modified, fix any auxiliary search tree by remaking all the nodes in the
 * auxiliary search tree that @k corresponds to
 */
void bch2_bset_fix_invalidated_key(struct btree *b, struct bkey_packed *k)
{
        struct bset_tree *t = bch2_bkey_to_bset(b, k);

        switch (bset_aux_tree_type(t)) {
        case BSET_NO_AUX_TREE:
                break;
        case BSET_RO_AUX_TREE:
                ro_aux_tree_fix_invalidated_key(b, t, k);
                break;
        case BSET_RW_AUX_TREE:
                rw_aux_tree_fix_invalidated_key(b, t, k);
                break;
        }
}

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_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_whiteout(&insert->k))
                btree_keys_account_key_add(&b->nr, t - b->set, src);

        if (src->u64s != clobber_u64s) {
                u64 *src_p = where->_data + clobber_u64s;
                u64 *dst_p = 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(where, src,
                    bkeyp_key_u64s(f, src));
        memcpy_u64s(bkeyp_val(f, where), &insert->v,
                    bkeyp_val_u64s(f, src));

        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 = 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,
                                const struct bkey_packed *packed_search)
{
        unsigned l = 0, r = t->size;

        while (l + 1 != r) {
                unsigned m = (l + r) >> 1;

                if (bkey_cmp(rw_aux_tree(b, t)[m].k, *search) < 0)
                        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(".intel_syntax noprefix;"
            "prefetcht0 [%0 - 127 + 64 * 0];"
            "prefetcht0 [%0 - 127 + 64 * 1];"
            "prefetcht0 [%0 - 127 + 64 * 2];"
            "prefetcht0 [%0 - 127 + 64 * 3];"
            ".att_syntax prefix;"
            :
            : "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,
                                struct bset_tree *t,
                                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(packed_search))
                        goto slowpath;
                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, 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)];
        }

        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, lossy_packed_search);
        case BSET_RO_AUX_TREE:
                /*
                 * Each node in the auxiliary search tree covers a certain range
                 * of bits, and keys above and below the set it covers might
                 * differ outside those bits - so we have to special case the
                 * start and end - handle that here:
                 */

                if (bkey_cmp(*search, t->max_key) > 0)
                        return btree_bkey_last(b, t);

                return bset_search_tree(b, t, search, lossy_packed_search);
        default:
                unreachable();
        }
}

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, search, lossy_packed_search,
                                              m) > 0)
                        m = bkey_next(m);

        if (!packed_search)
                while (m != btree_bkey_last(b, t) &&
                       bkey_iter_pos_cmp(b, search, m) > 0)
                        m = bkey_next(m);

        if (btree_keys_expensive_checks(b)) {
                struct bkey_packed *prev = bch2_bkey_prev_all(b, t, m);

                BUG_ON(prev &&
                       bkey_iter_cmp_p_or_unp(b, search, packed_search,
                                              prev) <= 0);
        }

        return m;
}

/*
 * Returns the first key greater than or equal to @search
 */
static __always_inline __flatten
struct bkey_packed *bch2_bset_search(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 = __bch2_bset_search(b, t, search,
                                                   lossy_packed_search);

        return bch2_bset_search_linear(b, t, search,
                                 packed_search, lossy_packed_search, 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 __attribute__((cold))
static void btree_node_iter_init_pack_failed(struct btree_node_iter *iter,
                              struct btree *b, struct bpos *search)
{
        struct bset_tree *t;

        trace_bkey_pack_pos_fail(search);

        for_each_bset(b, t)
                __bch2_btree_node_iter_push(iter, b,
                        bch2_bset_search(b, t, search, NULL, NULL),
                        btree_bkey_last(b, t));

        bch2_btree_node_iter_sort(iter, b);
}

/**
 * bch_btree_node_iter_init - initialize a btree node iterator, starting from a
 * given position
 *
 * 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
 *    bkey_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(bkey_cmp(*search, b->data->min_key) < 0);
        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))) {
                bch2_btree_node_iter_set_drop(iter, iter->data);
                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 (btree_keys_expensive_checks(b)) {
                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;

        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;

        bch2_btree_node_iter_verify(iter, b);
        return prev;
}

struct bkey_packed *bch2_btree_node_iter_prev_filter(struct btree_node_iter *iter,
                                                     struct btree *b,
                                                     unsigned min_key_type)
{
        struct bkey_packed *prev;

        do {
                prev = bch2_btree_node_iter_prev_all(iter, b);
        } while (prev && prev->type < min_key_type);

        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(struct btree *b, struct bset_stats *stats)
{
        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 (out->pos != out->end)
                *out->pos = '\0';

        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, 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);
                pr_buf(out,
                       "    failed unpacked at depth %u\n"
                       "\t%llu:%llu\n",
                       ilog2(j),
                       uk.p.inode, uk.p.offset);
                break;
        }
}