Linux 3.12.39

[linux/fpc-iii.git] / drivers / md / bcache / bset.c

/*
 * Code for working with individual keys, and sorted sets of keys with in a
 * btree node
 *
 * Copyright 2012 Google, Inc.
 */

#include "bcache.h"
#include "btree.h"
#include "debug.h"

#include <linux/random.h>
#include <linux/prefetch.h>

/* Keylists */

void bch_keylist_copy(struct keylist *dest, struct keylist *src)
{
        *dest = *src;

        if (src->list == src->d) {
                size_t n = (uint64_t *) src->top - src->d;
                dest->top = (struct bkey *) &dest->d[n];
                dest->list = dest->d;
        }
}

int bch_keylist_realloc(struct keylist *l, int nptrs, struct cache_set *c)
{
        unsigned oldsize = (uint64_t *) l->top - l->list;
        unsigned newsize = oldsize + 2 + nptrs;
        uint64_t *new;

        /* The journalling code doesn't handle the case where the keys to insert
         * is bigger than an empty write: If we just return -ENOMEM here,
         * bio_insert() and bio_invalidate() will insert the keys created so far
         * and finish the rest when the keylist is empty.
         */
        if (newsize * sizeof(uint64_t) > block_bytes(c) - sizeof(struct jset))
                return -ENOMEM;

        newsize = roundup_pow_of_two(newsize);

        if (newsize <= KEYLIST_INLINE ||
            roundup_pow_of_two(oldsize) == newsize)
                return 0;

        new = krealloc(l->list == l->d ? NULL : l->list,
                       sizeof(uint64_t) * newsize, GFP_NOIO);

        if (!new)
                return -ENOMEM;

        if (l->list == l->d)
                memcpy(new, l->list, sizeof(uint64_t) * KEYLIST_INLINE);

        l->list = new;
        l->top = (struct bkey *) (&l->list[oldsize]);

        return 0;
}

struct bkey *bch_keylist_pop(struct keylist *l)
{
        struct bkey *k = l->bottom;

        if (k == l->top)
                return NULL;

        while (bkey_next(k) != l->top)
                k = bkey_next(k);

        return l->top = k;
}

/* Pointer validation */

bool __bch_ptr_invalid(struct cache_set *c, int level, const struct bkey *k)
{
        unsigned i;
        char buf[80];

        if (level && (!KEY_PTRS(k) || !KEY_SIZE(k) || KEY_DIRTY(k)))
                goto bad;

        if (!level && KEY_SIZE(k) > KEY_OFFSET(k))
                goto bad;

        if (!KEY_SIZE(k))
                return true;

        for (i = 0; i < KEY_PTRS(k); i++)
                if (ptr_available(c, k, i)) {
                        struct cache *ca = PTR_CACHE(c, k, i);
                        size_t bucket = PTR_BUCKET_NR(c, k, i);
                        size_t r = bucket_remainder(c, PTR_OFFSET(k, i));

                        if (KEY_SIZE(k) + r > c->sb.bucket_size ||
                            bucket <  ca->sb.first_bucket ||
                            bucket >= ca->sb.nbuckets)
                                goto bad;
                }

        return false;
bad:
        bch_bkey_to_text(buf, sizeof(buf), k);
        cache_bug(c, "spotted bad key %s: %s", buf, bch_ptr_status(c, k));
        return true;
}

bool bch_ptr_bad(struct btree *b, const struct bkey *k)
{
        struct bucket *g;
        unsigned i, stale;

        if (!bkey_cmp(k, &ZERO_KEY) ||
            !KEY_PTRS(k) ||
            bch_ptr_invalid(b, k))
                return true;

        if (KEY_PTRS(k) && PTR_DEV(k, 0) == PTR_CHECK_DEV)
                return true;

        for (i = 0; i < KEY_PTRS(k); i++)
                if (ptr_available(b->c, k, i)) {
                        g = PTR_BUCKET(b->c, k, i);
                        stale = ptr_stale(b->c, k, i);

                        btree_bug_on(stale > 96, b,
                                     "key too stale: %i, need_gc %u",
                                     stale, b->c->need_gc);

                        btree_bug_on(stale && KEY_DIRTY(k) && KEY_SIZE(k),
                                     b, "stale dirty pointer");

                        if (stale)
                                return true;

#ifdef CONFIG_BCACHE_EDEBUG
                        if (!mutex_trylock(&b->c->bucket_lock))
                                continue;

                        if (b->level) {
                                if (KEY_DIRTY(k) ||
                                    g->prio != BTREE_PRIO ||
                                    (b->c->gc_mark_valid &&
                                     GC_MARK(g) != GC_MARK_METADATA))
                                        goto bug;

                        } else {
                                if (g->prio == BTREE_PRIO)
                                        goto bug;

                                if (KEY_DIRTY(k) &&
                                    b->c->gc_mark_valid &&
                                    GC_MARK(g) != GC_MARK_DIRTY)
                                        goto bug;
                        }
                        mutex_unlock(&b->c->bucket_lock);
#endif
                }

        return false;
#ifdef CONFIG_BCACHE_EDEBUG
bug:
        mutex_unlock(&b->c->bucket_lock);

        {
                char buf[80];

                bch_bkey_to_text(buf, sizeof(buf), k);
                btree_bug(b,
"inconsistent pointer %s: bucket %zu pin %i prio %i gen %i last_gc %i mark %llu gc_gen %i",
                          buf, PTR_BUCKET_NR(b->c, k, i), atomic_read(&g->pin),
                          g->prio, g->gen, g->last_gc, GC_MARK(g), g->gc_gen);
        }
        return true;
#endif
}

/* Key/pointer manipulation */

void bch_bkey_copy_single_ptr(struct bkey *dest, const struct bkey *src,
                              unsigned i)
{
        BUG_ON(i > KEY_PTRS(src));

        /* Only copy the header, key, and one pointer. */
        memcpy(dest, src, 2 * sizeof(uint64_t));
        dest->ptr[0] = src->ptr[i];
        SET_KEY_PTRS(dest, 1);
        /* We didn't copy the checksum so clear that bit. */
        SET_KEY_CSUM(dest, 0);
}

bool __bch_cut_front(const struct bkey *where, struct bkey *k)
{
        unsigned i, len = 0;

        if (bkey_cmp(where, &START_KEY(k)) <= 0)
                return false;

        if (bkey_cmp(where, k) < 0)
                len = KEY_OFFSET(k) - KEY_OFFSET(where);
        else
                bkey_copy_key(k, where);

        for (i = 0; i < KEY_PTRS(k); i++)
                SET_PTR_OFFSET(k, i, PTR_OFFSET(k, i) + KEY_SIZE(k) - len);

        BUG_ON(len > KEY_SIZE(k));
        SET_KEY_SIZE(k, len);
        return true;
}

bool __bch_cut_back(const struct bkey *where, struct bkey *k)
{
        unsigned len = 0;

        if (bkey_cmp(where, k) >= 0)
                return false;

        BUG_ON(KEY_INODE(where) != KEY_INODE(k));

        if (bkey_cmp(where, &START_KEY(k)) > 0)
                len = KEY_OFFSET(where) - KEY_START(k);

        bkey_copy_key(k, where);

        BUG_ON(len > KEY_SIZE(k));
        SET_KEY_SIZE(k, len);
        return true;
}

static uint64_t merge_chksums(struct bkey *l, struct bkey *r)
{
        return (l->ptr[KEY_PTRS(l)] + r->ptr[KEY_PTRS(r)]) &
                ~((uint64_t)1 << 63);
}

/* Tries to merge l and r: l should be lower than r
 * Returns true if we were able to merge. If we did merge, l will be the merged
 * key, r will be untouched.
 */
bool bch_bkey_try_merge(struct btree *b, struct bkey *l, struct bkey *r)
{
        unsigned i;

        if (key_merging_disabled(b->c))
                return false;

        if (KEY_PTRS(l) != KEY_PTRS(r) ||
            KEY_DIRTY(l) != KEY_DIRTY(r) ||
            bkey_cmp(l, &START_KEY(r)))
                return false;

        for (i = 0; i < KEY_PTRS(l); i++)
                if (l->ptr[i] + PTR(0, KEY_SIZE(l), 0) != r->ptr[i] ||
                    PTR_BUCKET_NR(b->c, l, i) != PTR_BUCKET_NR(b->c, r, i))
                        return false;

        /* Keys with no pointers aren't restricted to one bucket and could
         * overflow KEY_SIZE
         */
        if (KEY_SIZE(l) + KEY_SIZE(r) > USHRT_MAX) {
                SET_KEY_OFFSET(l, KEY_OFFSET(l) + USHRT_MAX - KEY_SIZE(l));
                SET_KEY_SIZE(l, USHRT_MAX);

                bch_cut_front(l, r);
                return false;
        }

        if (KEY_CSUM(l)) {
                if (KEY_CSUM(r))
                        l->ptr[KEY_PTRS(l)] = merge_chksums(l, r);
                else
                        SET_KEY_CSUM(l, 0);
        }

        SET_KEY_OFFSET(l, KEY_OFFSET(l) + KEY_SIZE(r));
        SET_KEY_SIZE(l, KEY_SIZE(l) + KEY_SIZE(r));

        return true;
}

/* Binary tree stuff for auxiliary search trees */

static unsigned inorder_next(unsigned j, unsigned size)
{
        if (j * 2 + 1 < size) {
                j = j * 2 + 1;

                while (j * 2 < size)
                        j *= 2;
        } else
                j >>= ffz(j) + 1;

        return j;
}

static unsigned inorder_prev(unsigned j, unsigned size)
{
        if (j * 2 < size) {
                j = j * 2;

                while (j * 2 + 1 < size)
                        j = j * 2 + 1;
        } else
                j >>= ffs(j);

        return j;
}

/* I have no idea why this code works... and I'm the one who wrote it
 *
 * However, I do know what it does:
 * Given a binary tree constructed in an array (i.e. how you normally implement
 * a heap), it converts a node in the tree - referenced by array index - to the
 * index it would have if you did an inorder traversal.
 *
 * Also tested for every j, size up to size somewhere around 6 million.
 *
 * The binary tree starts at array index 1, not 0
 * extra is a function of size:
 *   extra = (size - rounddown_pow_of_two(size - 1)) << 1;
 */
static unsigned __to_inorder(unsigned j, unsigned size, unsigned extra)
{
        unsigned b = fls(j);
        unsigned shift = fls(size - 1) - b;

        j  ^= 1U << (b - 1);
        j <<= 1;
        j  |= 1;
        j <<= shift;

        if (j > extra)
                j -= (j - extra) >> 1;

        return j;
}

static unsigned to_inorder(unsigned j, struct bset_tree *t)
{
        return __to_inorder(j, t->size, t->extra);
}

static unsigned __inorder_to_tree(unsigned j, unsigned size, unsigned extra)
{
        unsigned shift;

        if (j > extra)
                j += j - extra;

        shift = ffs(j);

        j >>= shift;
        j  |= roundup_pow_of_two(size) >> shift;

        return j;
}

static unsigned inorder_to_tree(unsigned j, struct bset_tree *t)
{
        return __inorder_to_tree(j, t->size, t->extra);
}

#if 0
void inorder_test(void)
{
        unsigned long done = 0;
        ktime_t start = ktime_get();

        for (unsigned size = 2;
             size < 65536000;
             size++) {
                unsigned extra = (size - rounddown_pow_of_two(size - 1)) << 1;
                unsigned i = 1, j = rounddown_pow_of_two(size - 1);

                if (!(size % 4096))
                        printk(KERN_NOTICE "loop %u, %llu per us\n", size,
                               done / ktime_us_delta(ktime_get(), start));

                while (1) {
                        if (__inorder_to_tree(i, size, extra) != j)
                                panic("size %10u j %10u i %10u", size, j, i);

                        if (__to_inorder(j, size, extra) != i)
                                panic("size %10u j %10u i %10u", size, j, i);

                        if (j == rounddown_pow_of_two(size) - 1)
                                break;

                        BUG_ON(inorder_prev(inorder_next(j, size), size) != j);

                        j = inorder_next(j, size);
                        i++;
                }

                done += size - 1;
        }
}
#endif

/*
 * 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; 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 struct bkey *cacheline_to_bkey(struct bset_tree *t, unsigned cacheline,
                                      unsigned offset)
{
        return ((void *) t->data) + cacheline * BSET_CACHELINE + offset * 8;
}

static unsigned bkey_to_cacheline(struct bset_tree *t, struct bkey *k)
{
        return ((void *) k - (void *) t->data) / BSET_CACHELINE;
}

static unsigned bkey_to_cacheline_offset(struct bkey *k)
{
        return ((size_t) k & (BSET_CACHELINE - 1)) / sizeof(uint64_t);
}

static struct bkey *tree_to_bkey(struct bset_tree *t, unsigned j)
{
        return cacheline_to_bkey(t, to_inorder(j, t), t->tree[j].m);
}

static struct bkey *tree_to_prev_bkey(struct bset_tree *t, unsigned j)
{
        return (void *) (((uint64_t *) tree_to_bkey(t, j)) - t->prev[j]);
}

/*
 * 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 *table_to_bkey(struct bset_tree *t, unsigned cacheline)
{
        return cacheline_to_bkey(t, cacheline, t->prev[cacheline]);
}

static inline uint64_t shrd128(uint64_t high, uint64_t low, uint8_t shift)
{
#ifdef CONFIG_X86_64
        asm("shrd %[shift],%[high],%[low]"
            : [low] "+Rm" (low)
            : [high] "R" (high),
            [shift] "ci" (shift)
            : "cc");
#else
        low >>= shift;
        low  |= (high << 1) << (63U - shift);
#endif
        return low;
}

static inline unsigned bfloat_mantissa(const struct bkey *k,
                                       struct bkey_float *f)
{
        const uint64_t *p = &k->low - (f->exponent >> 6);
        return shrd128(p[-1], p[0], f->exponent & 63) & BKEY_MANTISSA_MASK;
}

static void make_bfloat(struct bset_tree *t, unsigned j)
{
        struct bkey_float *f = &t->tree[j];
        struct bkey *m = tree_to_bkey(t, j);
        struct bkey *p = tree_to_prev_bkey(t, j);

        struct bkey *l = is_power_of_2(j)
                ? t->data->start
                : tree_to_prev_bkey(t, j >> ffs(j));

        struct bkey *r = is_power_of_2(j + 1)
                ? node(t->data, t->data->keys - bkey_u64s(&t->end))
                : tree_to_bkey(t, j >> (ffz(j) + 1));

        BUG_ON(m < l || m > r);
        BUG_ON(bkey_next(p) != m);

        if (KEY_INODE(l) != KEY_INODE(r))
                f->exponent = fls64(KEY_INODE(r) ^ KEY_INODE(l)) + 64;
        else
                f->exponent = fls64(r->low ^ l->low);

        f->exponent = max_t(int, f->exponent - BKEY_MANTISSA_BITS, 0);

        /*
         * Setting f->exponent = 127 flags this node as failed, and causes the
         * lookup code to fall back to comparing against the original key.
         */

        if (bfloat_mantissa(m, f) != bfloat_mantissa(p, f))
                f->mantissa = bfloat_mantissa(m, f) - 1;
        else
                f->exponent = 127;
}

static void bset_alloc_tree(struct btree *b, struct bset_tree *t)
{
        if (t != b->sets) {
                unsigned j = roundup(t[-1].size,
                                     64 / sizeof(struct bkey_float));

                t->tree = t[-1].tree + j;
                t->prev = t[-1].prev + j;
        }

        while (t < b->sets + MAX_BSETS)
                t++->size = 0;
}

static void bset_build_unwritten_tree(struct btree *b)
{
        struct bset_tree *t = b->sets + b->nsets;

        bset_alloc_tree(b, t);

        if (t->tree != b->sets->tree + bset_tree_space(b)) {
                t->prev[0] = bkey_to_cacheline_offset(t->data->start);
                t->size = 1;
        }
}

static void bset_build_written_tree(struct btree *b)
{
        struct bset_tree *t = b->sets + b->nsets;
        struct bkey *k = t->data->start;
        unsigned j, cacheline = 1;

        bset_alloc_tree(b, t);

        t->size = min_t(unsigned,
                        bkey_to_cacheline(t, end(t->data)),
                        b->sets->tree + bset_tree_space(b) - t->tree);

        if (t->size < 2) {
                t->size = 0;
                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 */
        for (j = inorder_next(0, t->size);
             j;
             j = inorder_next(j, t->size)) {
                while (bkey_to_cacheline(t, k) != cacheline)
                        k = bkey_next(k);

                t->prev[j] = bkey_u64s(k);
                k = bkey_next(k);
                cacheline++;
                t->tree[j].m = bkey_to_cacheline_offset(k);
        }

        while (bkey_next(k) != end(t->data))
                k = bkey_next(k);

        t->end = *k;

        /* Then we build the tree */
        for (j = inorder_next(0, t->size);
             j;
             j = inorder_next(j, t->size))
                make_bfloat(t, j);
}

void bch_bset_fix_invalidated_key(struct btree *b, struct bkey *k)
{
        struct bset_tree *t;
        unsigned inorder, j = 1;

        for (t = b->sets; t <= &b->sets[b->nsets]; t++)
                if (k < end(t->data))
                        goto found_set;

        BUG();
found_set:
        if (!t->size || !bset_written(b, t))
                return;

        inorder = bkey_to_cacheline(t, k);

        if (k == t->data->start)
                goto fix_left;

        if (bkey_next(k) == end(t->data)) {
                t->end = *k;
                goto fix_right;
        }

        j = inorder_to_tree(inorder, t);

        if (j &&
            j < t->size &&
            k == tree_to_bkey(t, j))
fix_left:       do {
                        make_bfloat(t, j);
                        j = j * 2;
                } while (j < t->size);

        j = inorder_to_tree(inorder + 1, t);

        if (j &&
            j < t->size &&
            k == tree_to_prev_bkey(t, j))
fix_right:      do {
                        make_bfloat(t, j);
                        j = j * 2 + 1;
                } while (j < t->size);
}

void bch_bset_fix_lookup_table(struct btree *b, struct bkey *k)
{
        struct bset_tree *t = &b->sets[b->nsets];
        unsigned shift = bkey_u64s(k);
        unsigned j = bkey_to_cacheline(t, k);

        /* We're getting called from btree_split() or btree_gc, just bail out */
        if (!t->size)
                return;

        /* k is the key we just inserted; we need to find the entry in the
         * lookup table for the first key that is strictly greater than k:
         * it's either k's cacheline or the next one
         */
        if (j < t->size &&
            table_to_bkey(t, j) <= k)
                j++;

        /* Adjust all the lookup table entries, and find a new key for any that
         * have gotten too big
         */
        for (; j < t->size; j++) {
                t->prev[j] += shift;

                if (t->prev[j] > 7) {
                        k = table_to_bkey(t, j - 1);

                        while (k < cacheline_to_bkey(t, j, 0))
                                k = bkey_next(k);

                        t->prev[j] = bkey_to_cacheline_offset(k);
                }
        }

        if (t->size == b->sets->tree + bset_tree_space(b) - t->tree)
                return;

        /* Possibly add a new entry to the end of the lookup table */

        for (k = table_to_bkey(t, t->size - 1);
             k != end(t->data);
             k = bkey_next(k))
                if (t->size == bkey_to_cacheline(t, k)) {
                        t->prev[t->size] = bkey_to_cacheline_offset(k);
                        t->size++;
                }
}

void bch_bset_init_next(struct btree *b)
{
        struct bset *i = write_block(b);

        if (i != b->sets[0].data) {
                b->sets[++b->nsets].data = i;
                i->seq = b->sets[0].data->seq;
        } else
                get_random_bytes(&i->seq, sizeof(uint64_t));

        i->magic        = bset_magic(b->c);
        i->version      = 0;
        i->keys         = 0;

        bset_build_unwritten_tree(b);
}

struct bset_search_iter {
        struct bkey *l, *r;
};

static struct bset_search_iter bset_search_write_set(struct btree *b,
                                                     struct bset_tree *t,
                                                     const struct bkey *search)
{
        unsigned li = 0, ri = t->size;

        BUG_ON(!b->nsets &&
               t->size < bkey_to_cacheline(t, end(t->data)));

        while (li + 1 != ri) {
                unsigned m = (li + ri) >> 1;

                if (bkey_cmp(table_to_bkey(t, m), search) > 0)
                        ri = m;
                else
                        li = m;
        }

        return (struct bset_search_iter) {
                table_to_bkey(t, li),
                ri < t->size ? table_to_bkey(t, ri) : end(t->data)
        };
}

static struct bset_search_iter bset_search_tree(struct btree *b,
                                                struct bset_tree *t,
                                                const struct bkey *search)
{
        struct bkey *l, *r;
        struct bkey_float *f;
        unsigned inorder, j, n = 1;

        do {
                unsigned p = n << 4;
                p &= ((int) (p - t->size)) >> 31;

                prefetch(&t->tree[p]);

                j = n;
                f = &t->tree[j];

                /*
                 * n = (f->mantissa > bfloat_mantissa())
                 *      ? j * 2
                 *      : j * 2 + 1;
                 *
                 * We need to subtract 1 from f->mantissa for the sign bit trick
                 * to work  - that's done in make_bfloat()
                 */
                if (likely(f->exponent != 127))
                        n = j * 2 + (((unsigned)
                                      (f->mantissa -
                                       bfloat_mantissa(search, f))) >> 31);
                else
                        n = (bkey_cmp(tree_to_bkey(t, j), search) > 0)
                                ? j * 2
                                : j * 2 + 1;
        } while (n < t->size);

        inorder = to_inorder(j, t);

        /*
         * n would have been the node we recursed to - the low bit tells us if
         * we recursed left or recursed right.
         */
        if (n & 1) {
                l = cacheline_to_bkey(t, inorder, f->m);

                if (++inorder != t->size) {
                        f = &t->tree[inorder_next(j, t->size)];
                        r = cacheline_to_bkey(t, inorder, f->m);
                } else
                        r = end(t->data);
        } else {
                r = cacheline_to_bkey(t, inorder, f->m);

                if (--inorder) {
                        f = &t->tree[inorder_prev(j, t->size)];
                        l = cacheline_to_bkey(t, inorder, f->m);
                } else
                        l = t->data->start;
        }

        return (struct bset_search_iter) {l, r};
}

struct bkey *__bch_bset_search(struct btree *b, struct bset_tree *t,
                               const struct bkey *search)
{
        struct bset_search_iter i;

        /*
         * 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()
         */

        if (unlikely(!t->size)) {
                i.l = t->data->start;
                i.r = end(t->data);
        } else if (bset_written(b, t)) {
                /*
                 * 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 (unlikely(bkey_cmp(search, &t->end) >= 0))
                        return end(t->data);

                if (unlikely(bkey_cmp(search, t->data->start) < 0))
                        return t->data->start;

                i = bset_search_tree(b, t, search);
        } else
                i = bset_search_write_set(b, t, search);

#ifdef CONFIG_BCACHE_EDEBUG
        BUG_ON(bset_written(b, t) &&
               i.l != t->data->start &&
               bkey_cmp(tree_to_prev_bkey(t,
                  inorder_to_tree(bkey_to_cacheline(t, i.l), t)),
                        search) > 0);

        BUG_ON(i.r != end(t->data) &&
               bkey_cmp(i.r, search) <= 0);
#endif

        while (likely(i.l != i.r) &&
               bkey_cmp(i.l, search) <= 0)
                i.l = bkey_next(i.l);

        return i.l;
}

/* Btree iterator */

static inline bool btree_iter_cmp(struct btree_iter_set l,
                                  struct btree_iter_set r)
{
        int64_t c = bkey_cmp(&START_KEY(l.k), &START_KEY(r.k));

        return c ? c > 0 : l.k < r.k;
}

static inline bool btree_iter_end(struct btree_iter *iter)
{
        return !iter->used;
}

void bch_btree_iter_push(struct btree_iter *iter, struct bkey *k,
                         struct bkey *end)
{
        if (k != end)
                BUG_ON(!heap_add(iter,
                                 ((struct btree_iter_set) { k, end }),
                                 btree_iter_cmp));
}

struct bkey *__bch_btree_iter_init(struct btree *b, struct btree_iter *iter,
                               struct bkey *search, struct bset_tree *start)
{
        struct bkey *ret = NULL;
        iter->size = ARRAY_SIZE(iter->data);
        iter->used = 0;

        for (; start <= &b->sets[b->nsets]; start++) {
                ret = bch_bset_search(b, start, search);
                bch_btree_iter_push(iter, ret, end(start->data));
        }

        return ret;
}

struct bkey *bch_btree_iter_next(struct btree_iter *iter)
{
        struct btree_iter_set unused;
        struct bkey *ret = NULL;

        if (!btree_iter_end(iter)) {
                ret = iter->data->k;
                iter->data->k = bkey_next(iter->data->k);

                if (iter->data->k > iter->data->end) {
                        WARN_ONCE(1, "bset was corrupt!\n");
                        iter->data->k = iter->data->end;
                }

                if (iter->data->k == iter->data->end)
                        heap_pop(iter, unused, btree_iter_cmp);
                else
                        heap_sift(iter, 0, btree_iter_cmp);
        }

        return ret;
}

struct bkey *bch_btree_iter_next_filter(struct btree_iter *iter,
                                        struct btree *b, ptr_filter_fn fn)
{
        struct bkey *ret;

        do {
                ret = bch_btree_iter_next(iter);
        } while (ret && fn(b, ret));

        return ret;
}

struct bkey *bch_next_recurse_key(struct btree *b, struct bkey *search)
{
        struct btree_iter iter;

        bch_btree_iter_init(b, &iter, search);
        return bch_btree_iter_next_filter(&iter, b, bch_ptr_bad);
}

/* Mergesort */

static void sort_key_next(struct btree_iter *iter,
                          struct btree_iter_set *i)
{
        i->k = bkey_next(i->k);

        if (i->k == i->end)
                *i = iter->data[--iter->used];
}

static struct bkey *btree_sort_fixup(struct btree_iter *iter, struct bkey *tmp)
{
        while (iter->used > 1) {
                struct btree_iter_set *top = iter->data, *i = top + 1;

                if (iter->used > 2 &&
                    btree_iter_cmp(i[0], i[1]))
                        i++;

                if (bkey_cmp(top->k, &START_KEY(i->k)) <= 0)
                        break;

                if (!KEY_SIZE(i->k)) {
                        sort_key_next(iter, i);
                        heap_sift(iter, i - top, btree_iter_cmp);
                        continue;
                }

                if (top->k > i->k) {
                        if (bkey_cmp(top->k, i->k) >= 0)
                                sort_key_next(iter, i);
                        else
                                bch_cut_front(top->k, i->k);

                        heap_sift(iter, i - top, btree_iter_cmp);
                } else {
                        /* can't happen because of comparison func */
                        BUG_ON(!bkey_cmp(&START_KEY(top->k), &START_KEY(i->k)));

                        if (bkey_cmp(i->k, top->k) < 0) {
                                bkey_copy(tmp, top->k);

                                bch_cut_back(&START_KEY(i->k), tmp);
                                bch_cut_front(i->k, top->k);
                                heap_sift(iter, 0, btree_iter_cmp);

                                return tmp;
                        } else {
                                bch_cut_back(&START_KEY(i->k), top->k);
                        }
                }
        }

        return NULL;
}

static void btree_mergesort(struct btree *b, struct bset *out,
                            struct btree_iter *iter,
                            bool fixup, bool remove_stale)
{
        struct bkey *k, *last = NULL;
        BKEY_PADDED(k) tmp;
        bool (*bad)(struct btree *, const struct bkey *) = remove_stale
                ? bch_ptr_bad
                : bch_ptr_invalid;

        while (!btree_iter_end(iter)) {
                if (fixup && !b->level)
                        k = btree_sort_fixup(iter, &tmp.k);
                else
                        k = NULL;

                if (!k)
                        k = bch_btree_iter_next(iter);

                if (bad(b, k))
                        continue;

                if (!last) {
                        last = out->start;
                        bkey_copy(last, k);
                } else if (b->level ||
                           !bch_bkey_try_merge(b, last, k)) {
                        last = bkey_next(last);
                        bkey_copy(last, k);
                }
        }

        out->keys = last ? (uint64_t *) bkey_next(last) - out->d : 0;

        pr_debug("sorted %i keys", out->keys);
        bch_check_key_order(b, out);
}

static void __btree_sort(struct btree *b, struct btree_iter *iter,
                         unsigned start, unsigned order, bool fixup)
{
        uint64_t start_time;
        bool remove_stale = !b->written;
        struct bset *out = (void *) __get_free_pages(__GFP_NOWARN|GFP_NOIO,
                                                     order);
        if (!out) {
                mutex_lock(&b->c->sort_lock);
                out = b->c->sort;
                order = ilog2(bucket_pages(b->c));
        }

        start_time = local_clock();

        btree_mergesort(b, out, iter, fixup, remove_stale);
        b->nsets = start;

        if (!fixup && !start && b->written)
                bch_btree_verify(b, out);

        if (!start && order == b->page_order) {
                /*
                 * Our temporary buffer is the same size as the btree node's
                 * buffer, we can just swap buffers instead of doing a big
                 * memcpy()
                 */

                out->magic      = bset_magic(b->c);
                out->seq        = b->sets[0].data->seq;
                out->version    = b->sets[0].data->version;
                swap(out, b->sets[0].data);

                if (b->c->sort == b->sets[0].data)
                        b->c->sort = out;
        } else {
                b->sets[start].data->keys = out->keys;
                memcpy(b->sets[start].data->start, out->start,
                       (void *) end(out) - (void *) out->start);
        }

        if (out == b->c->sort)
                mutex_unlock(&b->c->sort_lock);
        else
                free_pages((unsigned long) out, order);

        if (b->written)
                bset_build_written_tree(b);

        if (!start) {
                spin_lock(&b->c->sort_time_lock);
                bch_time_stats_update(&b->c->sort_time, start_time);
                spin_unlock(&b->c->sort_time_lock);
        }
}

void bch_btree_sort_partial(struct btree *b, unsigned start)
{
        size_t oldsize = 0, order = b->page_order, keys = 0;
        struct btree_iter iter;
        __bch_btree_iter_init(b, &iter, NULL, &b->sets[start]);

        BUG_ON(b->sets[b->nsets].data == write_block(b) &&
               (b->sets[b->nsets].size || b->nsets));

        if (b->written)
                oldsize = bch_count_data(b);

        if (start) {
                unsigned i;

                for (i = start; i <= b->nsets; i++)
                        keys += b->sets[i].data->keys;

                order = roundup_pow_of_two(__set_bytes(b->sets->data,
                                                       keys)) / PAGE_SIZE;
                if (order)
                        order = ilog2(order);
        }

        __btree_sort(b, &iter, start, order, false);

        EBUG_ON(b->written && bch_count_data(b) != oldsize);
}

void bch_btree_sort_and_fix_extents(struct btree *b, struct btree_iter *iter)
{
        BUG_ON(!b->written);
        __btree_sort(b, iter, 0, b->page_order, true);
}

void bch_btree_sort_into(struct btree *b, struct btree *new)
{
        uint64_t start_time = local_clock();

        struct btree_iter iter;
        bch_btree_iter_init(b, &iter, NULL);

        btree_mergesort(b, new->sets->data, &iter, false, true);

        spin_lock(&b->c->sort_time_lock);
        bch_time_stats_update(&b->c->sort_time, start_time);
        spin_unlock(&b->c->sort_time_lock);

        bkey_copy_key(&new->key, &b->key);
        new->sets->size = 0;
}

#define SORT_CRIT       (4096 / sizeof(uint64_t))

void bch_btree_sort_lazy(struct btree *b)
{
        unsigned crit = SORT_CRIT;
        int i;

        /* Don't sort if nothing to do */
        if (!b->nsets)
                goto out;

        /* If not a leaf node, always sort */
        if (b->level) {
                bch_btree_sort(b);
                return;
        }

        for (i = b->nsets - 1; i >= 0; --i) {
                crit *= b->c->sort_crit_factor;

                if (b->sets[i].data->keys < crit) {
                        bch_btree_sort_partial(b, i);
                        return;
                }
        }

        /* Sort if we'd overflow */
        if (b->nsets + 1 == MAX_BSETS) {
                bch_btree_sort(b);
                return;
        }

out:
        bset_build_written_tree(b);
}

/* Sysfs stuff */

struct bset_stats {
        size_t nodes;
        size_t sets_written, sets_unwritten;
        size_t bytes_written, bytes_unwritten;
        size_t floats, failed;
};

static int bch_btree_bset_stats(struct btree *b, struct btree_op *op,
                            struct bset_stats *stats)
{
        struct bkey *k;
        unsigned i;

        stats->nodes++;

        for (i = 0; i <= b->nsets; i++) {
                struct bset_tree *t = &b->sets[i];
                size_t bytes = t->data->keys * sizeof(uint64_t);
                size_t j;

                if (bset_written(b, t)) {
                        stats->sets_written++;
                        stats->bytes_written += bytes;

                        stats->floats += t->size - 1;

                        for (j = 1; j < t->size; j++)
                                if (t->tree[j].exponent == 127)
                                        stats->failed++;
                } else {
                        stats->sets_unwritten++;
                        stats->bytes_unwritten += bytes;
                }
        }

        if (b->level) {
                struct btree_iter iter;

                for_each_key_filter(b, k, &iter, bch_ptr_bad) {
                        int ret = btree(bset_stats, k, b, op, stats);
                        if (ret)
                                return ret;
                }
        }

        return 0;
}

int bch_bset_print_stats(struct cache_set *c, char *buf)
{
        struct btree_op op;
        struct bset_stats t;
        int ret;

        bch_btree_op_init_stack(&op);
        memset(&t, 0, sizeof(struct bset_stats));

        ret = btree_root(bset_stats, c, &op, &t);
        if (ret)
                return ret;

        return snprintf(buf, PAGE_SIZE,
                        "btree nodes:           %zu\n"
                        "written sets:          %zu\n"
                        "unwritten sets:                %zu\n"
                        "written key bytes:     %zu\n"
                        "unwritten key bytes:   %zu\n"
                        "floats:                        %zu\n"
                        "failed:                        %zu\n",
                        t.nodes,
                        t.sets_written, t.sets_unwritten,
                        t.bytes_written, t.bytes_unwritten,
                        t.floats, t.failed);
}