dm-btree.c

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/*
 * Copyright (C) 2011 Red Hat, Inc.
 *
 * This file is released under the GPL.
 */

#include "dm-btree-internal.h"
#include "dm-space-map.h"
#include "dm-transaction-manager.h"

#include <linux/export.h>
#include <linux/device-mapper.h>

#define DM_MSG_PREFIX "btree"

/*----------------------------------------------------------------
 * Array manipulation
 *--------------------------------------------------------------*/
static void memcpy_disk(void *dest, const void *src, size_t len)
    __dm_written_to_disk(src)
{
    memcpy(dest, src, len);
    __dm_unbless_for_disk(src);
}

static void array_insert(void *base, size_t elt_size, unsigned nr_elts,
             unsigned index, void *elt)
    __dm_written_to_disk(elt)
{
    if (index < nr_elts)
        memmove(base + (elt_size * (index + 1)),
            base + (elt_size * index),
            (nr_elts - index) * elt_size);

    memcpy_disk(base + (elt_size * index), elt, elt_size);
}

/*----------------------------------------------------------------*/

/* makes the assumption that no two keys are the same. */
static int bsearch(struct node *n, uint64_t key, int want_hi)
{
    int lo = -1, hi = le32_to_cpu(n->header.nr_entries);

    while (hi - lo > 1) {
        int mid = lo + ((hi - lo) / 2);
        uint64_t mid_key = le64_to_cpu(n->keys[mid]);

        if (mid_key == key)
            return mid;

        if (mid_key < key)
            lo = mid;
        else
            hi = mid;
    }

    return want_hi ? hi : lo;
}

int lower_bound(struct node *n, uint64_t key)
{
    return bsearch(n, key, 0);
}

void inc_children(struct dm_transaction_manager *tm, struct node *n,
          struct dm_btree_value_type *vt)
{
    unsigned i;
    uint32_t nr_entries = le32_to_cpu(n->header.nr_entries);

    if (le32_to_cpu(n->header.flags) & INTERNAL_NODE)
        for (i = 0; i < nr_entries; i++)
            dm_tm_inc(tm, value64(n, i));
    else if (vt->inc)
        for (i = 0; i < nr_entries; i++)
            vt->inc(vt->context, value_ptr(n, i));
}

static int insert_at(size_t value_size, struct node *node, unsigned index,
              uint64_t key, void *value)
              __dm_written_to_disk(value)
{
    uint32_t nr_entries = le32_to_cpu(node->header.nr_entries);
    __le64 key_le = cpu_to_le64(key);

    if (index > nr_entries ||
        index >= le32_to_cpu(node->header.max_entries)) {
        DMERR("too many entries in btree node for insert");
        __dm_unbless_for_disk(value);
        return -ENOMEM;
    }

    __dm_bless_for_disk(&key_le);

    array_insert(node->keys, sizeof(*node->keys), nr_entries, index, &key_le);
    array_insert(value_base(node), value_size, nr_entries, index, value);
    node->header.nr_entries = cpu_to_le32(nr_entries + 1);

    return 0;
}

/*----------------------------------------------------------------*/

/*
 * We want 3n entries (for some n).  This works more nicely for repeated
 * insert remove loops than (2n + 1).
 */
static uint32_t calc_max_entries(size_t value_size, size_t block_size)
{
    uint32_t total, n;
    size_t elt_size = sizeof(uint64_t) + value_size; /* key + value */

    block_size -= sizeof(struct node_header);
    total = block_size / elt_size;
    n = total / 3;      /* rounds down */

    return 3 * n;
}

int dm_btree_empty(struct dm_btree_info *info, dm_block_t *root)
{
    int r;
    struct dm_block *b;
    struct node *n;
    size_t block_size;
    uint32_t max_entries;

    r = new_block(info, &b);
    if (r < 0)
        return r;

    block_size = dm_bm_block_size(dm_tm_get_bm(info->tm));
    max_entries = calc_max_entries(info->value_type.size, block_size);

    n = dm_block_data(b);
    memset(n, 0, block_size);
    n->header.flags = cpu_to_le32(LEAF_NODE);
    n->header.nr_entries = cpu_to_le32(0);
    n->header.max_entries = cpu_to_le32(max_entries);
    n->header.value_size = cpu_to_le32(info->value_type.size);

    *root = dm_block_location(b);
    return unlock_block(info, b);
}
EXPORT_SYMBOL_GPL(dm_btree_empty);

/*----------------------------------------------------------------*/

/*
 * Deletion uses a recursive algorithm, since we have limited stack space
 * we explicitly manage our own stack on the heap.
 */
#define MAX_SPINE_DEPTH 64
struct frame {
    struct dm_block *b;
    struct node *n;
    unsigned level;
    unsigned nr_children;
    unsigned current_child;
};

struct del_stack {
    struct dm_transaction_manager *tm;
    int top;
    struct frame spine[MAX_SPINE_DEPTH];
};

static int top_frame(struct del_stack *s, struct frame **f)
{
    if (s->top < 0) {
        DMERR("btree deletion stack empty");
        return -EINVAL;
    }

    *f = s->spine + s->top;

    return 0;
}

static int unprocessed_frames(struct del_stack *s)
{
    return s->top >= 0;
}

static int push_frame(struct del_stack *s, dm_block_t b, unsigned level)
{
    int r;
    uint32_t ref_count;

    if (s->top >= MAX_SPINE_DEPTH - 1) {
        DMERR("btree deletion stack out of memory");
        return -ENOMEM;
    }

    r = dm_tm_ref(s->tm, b, &ref_count);
    if (r)
        return r;

    if (ref_count > 1)
        /*
         * This is a shared node, so we can just decrement it's
         * reference counter and leave the children.
         */
        dm_tm_dec(s->tm, b);

    else {
        struct frame *f = s->spine + ++s->top;

        r = dm_tm_read_lock(s->tm, b, &btree_node_validator, &f->b);
        if (r) {
            s->top--;
            return r;
        }

        f->n = dm_block_data(f->b);
        f->level = level;
        f->nr_children = le32_to_cpu(f->n->header.nr_entries);
        f->current_child = 0;
    }

    return 0;
}

static void pop_frame(struct del_stack *s)
{
    struct frame *f = s->spine + s->top--;

    dm_tm_dec(s->tm, dm_block_location(f->b));
    dm_tm_unlock(s->tm, f->b);
}

int dm_btree_del(struct dm_btree_info *info, dm_block_t root)
{
    int r;
    struct del_stack *s;

    s = kmalloc(sizeof(*s), GFP_KERNEL);
    if (!s)
        return -ENOMEM;
    s->tm = info->tm;
    s->top = -1;

    r = push_frame(s, root, 1);
    if (r)
        goto out;

    while (unprocessed_frames(s)) {
        uint32_t flags;
        struct frame *f;
        dm_block_t b;

        r = top_frame(s, &f);
        if (r)
            goto out;

        if (f->current_child >= f->nr_children) {
            pop_frame(s);
            continue;
        }

        flags = le32_to_cpu(f->n->header.flags);
        if (flags & INTERNAL_NODE) {
            b = value64(f->n, f->current_child);
            f->current_child++;
            r = push_frame(s, b, f->level);
            if (r)
                goto out;

        } else if (f->level != (info->levels - 1)) {
            b = value64(f->n, f->current_child);
            f->current_child++;
            r = push_frame(s, b, f->level + 1);
            if (r)
                goto out;

        } else {
            if (info->value_type.dec) {
                unsigned i;

                for (i = 0; i < f->nr_children; i++)
                    info->value_type.dec(info->value_type.context,
                                 value_ptr(f->n, i));
            }
            f->current_child = f->nr_children;
        }
    }

out:
    kfree(s);
    return r;
}
EXPORT_SYMBOL_GPL(dm_btree_del);

/*----------------------------------------------------------------*/

static int btree_lookup_raw(struct ro_spine *s, dm_block_t block, uint64_t key,
                int (*search_fn)(struct node *, uint64_t),
                uint64_t *result_key, void *v, size_t value_size)
{
    int i, r;
    uint32_t flags, nr_entries;

    do {
        r = ro_step(s, block);
        if (r < 0)
            return r;

        i = search_fn(ro_node(s), key);

        flags = le32_to_cpu(ro_node(s)->header.flags);
        nr_entries = le32_to_cpu(ro_node(s)->header.nr_entries);
        if (i < 0 || i >= nr_entries)
            return -ENODATA;

        if (flags & INTERNAL_NODE)
            block = value64(ro_node(s), i);

    } while (!(flags & LEAF_NODE));

    *result_key = le64_to_cpu(ro_node(s)->keys[i]);
    memcpy(v, value_ptr(ro_node(s), i), value_size);

    return 0;
}

int dm_btree_lookup(struct dm_btree_info *info, dm_block_t root,
            uint64_t *keys, void *value_le)
{
    unsigned level, last_level = info->levels - 1;
    int r = -ENODATA;
    uint64_t rkey;
    __le64 internal_value_le;
    struct ro_spine spine;

    init_ro_spine(&spine, info);
    for (level = 0; level < info->levels; level++) {
        size_t size;
        void *value_p;

        if (level == last_level) {
            value_p = value_le;
            size = info->value_type.size;

        } else {
            value_p = &internal_value_le;
            size = sizeof(uint64_t);
        }

        r = btree_lookup_raw(&spine, root, keys[level],
                     lower_bound, &rkey,
                     value_p, size);

        if (!r) {
            if (rkey != keys[level]) {
                exit_ro_spine(&spine);
                return -ENODATA;
            }
        } else {
            exit_ro_spine(&spine);
            return r;
        }

        root = le64_to_cpu(internal_value_le);
    }
    exit_ro_spine(&spine);

    return r;
}
EXPORT_SYMBOL_GPL(dm_btree_lookup);

/*
 * Splits a node by creating a sibling node and shifting half the nodes
 * contents across.  Assumes there is a parent node, and it has room for
 * another child.
 *
 * Before:
 *    +--------+
 *    | Parent |
 *    +--------+
 *       |
 *       v
 *  +----------+
 *  | A ++++++ |
 *  +----------+
 *
 *
 * After:
 *      +--------+
 *      | Parent |
 *      +--------+
 *        | |
 *        v +------+
 *      +---------+        |
 *      | A* +++  |        v
 *      +---------+   +-------+
 *            | B +++ |
 *            +-------+
 *
 * Where A* is a shadow of A.
 */
static int btree_split_sibling(struct shadow_spine *s, dm_block_t root,
                   unsigned parent_index, uint64_t key)
{
    int r;
    size_t size;
    unsigned nr_left, nr_right;
    struct dm_block *left, *right, *parent;
    struct node *ln, *rn, *pn;
    __le64 location;

    left = shadow_current(s);

    r = new_block(s->info, &right);
    if (r < 0)
        return r;

    ln = dm_block_data(left);
    rn = dm_block_data(right);

    nr_left = le32_to_cpu(ln->header.nr_entries) / 2;
    nr_right = le32_to_cpu(ln->header.nr_entries) - nr_left;

    ln->header.nr_entries = cpu_to_le32(nr_left);

    rn->header.flags = ln->header.flags;
    rn->header.nr_entries = cpu_to_le32(nr_right);
    rn->header.max_entries = ln->header.max_entries;
    rn->header.value_size = ln->header.value_size;
    memcpy(rn->keys, ln->keys + nr_left, nr_right * sizeof(rn->keys[0]));

    size = le32_to_cpu(ln->header.flags) & INTERNAL_NODE ?
        sizeof(uint64_t) : s->info->value_type.size;
    memcpy(value_ptr(rn, 0), value_ptr(ln, nr_left),
           size * nr_right);

    /*
     * Patch up the parent
     */
    parent = shadow_parent(s);

    pn = dm_block_data(parent);
    location = cpu_to_le64(dm_block_location(left));
    __dm_bless_for_disk(&location);
    memcpy_disk(value_ptr(pn, parent_index),
            &location, sizeof(__le64));

    location = cpu_to_le64(dm_block_location(right));
    __dm_bless_for_disk(&location);

    r = insert_at(sizeof(__le64), pn, parent_index + 1,
              le64_to_cpu(rn->keys[0]), &location);
    if (r)
        return r;

    if (key < le64_to_cpu(rn->keys[0])) {
        unlock_block(s->info, right);
        s->nodes[1] = left;
    } else {
        unlock_block(s->info, left);
        s->nodes[1] = right;
    }

    return 0;
}

/*
 * Splits a node by creating two new children beneath the given node.
 *
 * Before:
 *    +----------+
 *    | A ++++++ |
 *    +----------+
 *
 *
 * After:
 *  +------------+
 *  | A (shadow) |
 *  +------------+
 *      |   |
 *   +------+   +----+
 *   |           |
 *   v           v
 * +-------+     +-------+
 * | B +++ |     | C +++ |
 * +-------+     +-------+
 */
static int btree_split_beneath(struct shadow_spine *s, uint64_t key)
{
    int r;
    size_t size;
    unsigned nr_left, nr_right;
    struct dm_block *left, *right, *new_parent;
    struct node *pn, *ln, *rn;
    __le64 val;

    new_parent = shadow_current(s);

    r = new_block(s->info, &left);
    if (r < 0)
        return r;

    r = new_block(s->info, &right);
    if (r < 0) {
        /* FIXME: put left */
        return r;
    }

    pn = dm_block_data(new_parent);
    ln = dm_block_data(left);
    rn = dm_block_data(right);

    nr_left = le32_to_cpu(pn->header.nr_entries) / 2;
    nr_right = le32_to_cpu(pn->header.nr_entries) - nr_left;

    ln->header.flags = pn->header.flags;
    ln->header.nr_entries = cpu_to_le32(nr_left);
    ln->header.max_entries = pn->header.max_entries;
    ln->header.value_size = pn->header.value_size;

    rn->header.flags = pn->header.flags;
    rn->header.nr_entries = cpu_to_le32(nr_right);
    rn->header.max_entries = pn->header.max_entries;
    rn->header.value_size = pn->header.value_size;

    memcpy(ln->keys, pn->keys, nr_left * sizeof(pn->keys[0]));
    memcpy(rn->keys, pn->keys + nr_left, nr_right * sizeof(pn->keys[0]));

    size = le32_to_cpu(pn->header.flags) & INTERNAL_NODE ?
        sizeof(__le64) : s->info->value_type.size;
    memcpy(value_ptr(ln, 0), value_ptr(pn, 0), nr_left * size);
    memcpy(value_ptr(rn, 0), value_ptr(pn, nr_left),
           nr_right * size);

    /* new_parent should just point to l and r now */
    pn->header.flags = cpu_to_le32(INTERNAL_NODE);
    pn->header.nr_entries = cpu_to_le32(2);
    pn->header.max_entries = cpu_to_le32(
        calc_max_entries(sizeof(__le64),
                 dm_bm_block_size(
                     dm_tm_get_bm(s->info->tm))));
    pn->header.value_size = cpu_to_le32(sizeof(__le64));

    val = cpu_to_le64(dm_block_location(left));
    __dm_bless_for_disk(&val);
    pn->keys[0] = ln->keys[0];
    memcpy_disk(value_ptr(pn, 0), &val, sizeof(__le64));

    val = cpu_to_le64(dm_block_location(right));
    __dm_bless_for_disk(&val);
    pn->keys[1] = rn->keys[0];
    memcpy_disk(value_ptr(pn, 1), &val, sizeof(__le64));

    /*
     * rejig the spine.  This is ugly, since it knows too
     * much about the spine
     */
    if (s->nodes[0] != new_parent) {
        unlock_block(s->info, s->nodes[0]);
        s->nodes[0] = new_parent;
    }
    if (key < le64_to_cpu(rn->keys[0])) {
        unlock_block(s->info, right);
        s->nodes[1] = left;
    } else {
        unlock_block(s->info, left);
        s->nodes[1] = right;
    }
    s->count = 2;

    return 0;
}

static int btree_insert_raw(struct shadow_spine *s, dm_block_t root,
                struct dm_btree_value_type *vt,
                uint64_t key, unsigned *index)
{
    int r, i = *index, top = 1;
    struct node *node;

    for (;;) {
        r = shadow_step(s, root, vt);
        if (r < 0)
            return r;

        node = dm_block_data(shadow_current(s));

        /*
         * We have to patch up the parent node, ugly, but I don't
         * see a way to do this automatically as part of the spine
         * op.
         */
        if (shadow_has_parent(s) && i >= 0) { /* FIXME: second clause unness. */
            __le64 location = cpu_to_le64(dm_block_location(shadow_current(s)));

            __dm_bless_for_disk(&location);
            memcpy_disk(value_ptr(dm_block_data(shadow_parent(s)), i),
                    &location, sizeof(__le64));
        }

        node = dm_block_data(shadow_current(s));

        if (node->header.nr_entries == node->header.max_entries) {
            if (top)
                r = btree_split_beneath(s, key);
            else
                r = btree_split_sibling(s, root, i, key);

            if (r < 0)
                return r;
        }

        node = dm_block_data(shadow_current(s));

        i = lower_bound(node, key);

        if (le32_to_cpu(node->header.flags) & LEAF_NODE)
            break;

        if (i < 0) {
            /* change the bounds on the lowest key */
            node->keys[0] = cpu_to_le64(key);
            i = 0;
        }

        root = value64(node, i);
        top = 0;
    }

    if (i < 0 || le64_to_cpu(node->keys[i]) != key)
        i++;

    *index = i;
    return 0;
}

static int insert(struct dm_btree_info *info, dm_block_t root,
          uint64_t *keys, void *value, dm_block_t *new_root,
          int *inserted)
          __dm_written_to_disk(value)
{
    int r, need_insert;
    unsigned level, index = -1, last_level = info->levels - 1;
    dm_block_t block = root;
    struct shadow_spine spine;
    struct node *n;
    struct dm_btree_value_type le64_type;

    le64_type.context = NULL;
    le64_type.size = sizeof(__le64);
    le64_type.inc = NULL;
    le64_type.dec = NULL;
    le64_type.equal = NULL;

    init_shadow_spine(&spine, info);

    for (level = 0; level < (info->levels - 1); level++) {
        r = btree_insert_raw(&spine, block, &le64_type, keys[level], &index);
        if (r < 0)
            goto bad;

        n = dm_block_data(shadow_current(&spine));
        need_insert = ((index >= le32_to_cpu(n->header.nr_entries)) ||
                   (le64_to_cpu(n->keys[index]) != keys[level]));

        if (need_insert) {
            dm_block_t new_tree;
            __le64 new_le;

            r = dm_btree_empty(info, &new_tree);
            if (r < 0)
                goto bad;

            new_le = cpu_to_le64(new_tree);
            __dm_bless_for_disk(&new_le);

            r = insert_at(sizeof(uint64_t), n, index,
                      keys[level], &new_le);
            if (r)
                goto bad;
        }

        if (level < last_level)
            block = value64(n, index);
    }

    r = btree_insert_raw(&spine, block, &info->value_type,
                 keys[level], &index);
    if (r < 0)
        goto bad;

    n = dm_block_data(shadow_current(&spine));
    need_insert = ((index >= le32_to_cpu(n->header.nr_entries)) ||
               (le64_to_cpu(n->keys[index]) != keys[level]));

    if (need_insert) {
        if (inserted)
            *inserted = 1;

        r = insert_at(info->value_type.size, n, index,
                  keys[level], value);
        if (r)
            goto bad_unblessed;
    } else {
        if (inserted)
            *inserted = 0;

        if (info->value_type.dec &&
            (!info->value_type.equal ||
             !info->value_type.equal(
                 info->value_type.context,
                 value_ptr(n, index),
                 value))) {
            info->value_type.dec(info->value_type.context,
                         value_ptr(n, index));
        }
        memcpy_disk(value_ptr(n, index),
                value, info->value_type.size);
    }

    *new_root = shadow_root(&spine);
    exit_shadow_spine(&spine);

    return 0;

bad:
    __dm_unbless_for_disk(value);
bad_unblessed:
    exit_shadow_spine(&spine);
    return r;
}

int dm_btree_insert(struct dm_btree_info *info, dm_block_t root,
            uint64_t *keys, void *value, dm_block_t *new_root)
            __dm_written_to_disk(value)
{
    return insert(info, root, keys, value, new_root, NULL);
}
EXPORT_SYMBOL_GPL(dm_btree_insert);

int dm_btree_insert_notify(struct dm_btree_info *info, dm_block_t root,
               uint64_t *keys, void *value, dm_block_t *new_root,
               int *inserted)
               __dm_written_to_disk(value)
{
    return insert(info, root, keys, value, new_root, inserted);
}
EXPORT_SYMBOL_GPL(dm_btree_insert_notify);

/*----------------------------------------------------------------*/

static int find_highest_key(struct ro_spine *s, dm_block_t block,
                uint64_t *result_key, dm_block_t *next_block)
{
    int i, r;
    uint32_t flags;

    do {
        r = ro_step(s, block);
        if (r < 0)
            return r;

        flags = le32_to_cpu(ro_node(s)->header.flags);
        i = le32_to_cpu(ro_node(s)->header.nr_entries);
        if (!i)
            return -ENODATA;
        else
            i--;

        *result_key = le64_to_cpu(ro_node(s)->keys[i]);
        if (next_block || flags & INTERNAL_NODE)
            block = value64(ro_node(s), i);

    } while (flags & INTERNAL_NODE);

    if (next_block)
        *next_block = block;
    return 0;
}

int dm_btree_find_highest_key(struct dm_btree_info *info, dm_block_t root,
                  uint64_t *result_keys)
{
    int r = 0, count = 0, level;
    struct ro_spine spine;

    init_ro_spine(&spine, info);
    for (level = 0; level < info->levels; level++) {
        r = find_highest_key(&spine, root, result_keys + level,
                     level == info->levels - 1 ? NULL : &root);
        if (r == -ENODATA) {
            r = 0;
            break;

        } else if (r)
            break;

        count++;
    }
    exit_ro_spine(&spine);

    return r ? r : count;
}
EXPORT_SYMBOL_GPL(dm_btree_find_highest_key);