Archipelago » qemu

/*

 * seek_l2_table

 *

 * seek l2_offset in the l2_cache table

 * if not found, return NULL,

 * if found,

 *   increments the l2 cache hit count of the entry,

 *   if counter overflow, divide by two all counters

 *   return the pointer to the l2 cache entry

 *

 */

static uint64_t *seek_l2_table(BDRVQcowState *s, uint64_t l2_offset)

{

    int i, j;

    for(i = 0; i < L2_CACHE_SIZE; i++) {

        if (l2_offset == s->l2_cache_offsets[i]) {

            /* increment the hit count */

            if (++s->l2_cache_counts[i] == 0xffffffff) {

                for(j = 0; j < L2_CACHE_SIZE; j++) {

                    s->l2_cache_counts[j] >>= 1;

                }

            }

            return s->l2_cache + (i << s->l2_bits);

        }

    }

    return NULL;

}

/*

 * l2_load

 * Loads a L2 table into memory. If the table is in the cache, the cache

 * is used; otherwise the L2 table is loaded from the image file.

 * Returns a pointer to the L2 table on success, or NULL if the read from

 * the image file failed.

 */

static uint64_t *l2_load(BlockDriverState *bs, uint64_t l2_offset)

{

    BDRVQcowState *s = bs->opaque;

    int min_index;

    uint64_t *l2_table;

    /* seek if the table for the given offset is in the cache */

    l2_table = seek_l2_table(s, l2_offset);

    if (l2_table != NULL)

        return l2_table;

    /* not found: load a new entry in the least used one */

    min_index = l2_cache_new_entry(bs);

    l2_table = s->l2_cache + (min_index << s->l2_bits);

    if (bdrv_pread(s->hd, l2_offset, l2_table, s->l2_size * sizeof(uint64_t)) !=

        s->l2_size * sizeof(uint64_t))

        return NULL;

    s->l2_cache_offsets[min_index] = l2_offset;

    s->l2_cache_counts[min_index] = 1;

    return l2_table;

}

/*

 * l2_allocate

 * Allocate a new l2 entry in the file. If l1_index points to an already

 * used entry in the L2 table (i.e. we are doing a copy on write for the L2

 * table) copy the contents of the old L2 table into the newly allocated one.

 * Otherwise the new table is initialized with zeros.

static uint64_t *l2_allocate(BlockDriverState *bs, int l1_index)

{

    BDRVQcowState *s = bs->opaque;

    int min_index;

    uint64_t old_l2_offset, tmp;

    uint64_t *l2_table, l2_offset;

    old_l2_offset = s->l1_table[l1_index];

    /* allocate a new l2 entry */

    l2_offset = alloc_clusters(bs, s->l2_size * sizeof(uint64_t));

    /* update the L1 entry */

    s->l1_table[l1_index] = l2_offset | QCOW_OFLAG_COPIED;

    tmp = cpu_to_be64(l2_offset | QCOW_OFLAG_COPIED);

    if (bdrv_pwrite(s->hd, s->l1_table_offset + l1_index * sizeof(tmp),

                    &tmp, sizeof(tmp)) != sizeof(tmp))

        return NULL;

    /* allocate a new entry in the l2 cache */

    min_index = l2_cache_new_entry(bs);

    l2_table = s->l2_cache + (min_index << s->l2_bits);

    if (old_l2_offset == 0) {

        /* if there was no old l2 table, clear the new table */

        memset(l2_table, 0, s->l2_size * sizeof(uint64_t));

    } else {

        /* if there was an old l2 table, read it from the disk */

        if (bdrv_pread(s->hd, old_l2_offset,

                       l2_table, s->l2_size * sizeof(uint64_t)) !=

            s->l2_size * sizeof(uint64_t))

            return NULL;

    }

    /* write the l2 table to the file */

    if (bdrv_pwrite(s->hd, l2_offset,

                    l2_table, s->l2_size * sizeof(uint64_t)) !=

        s->l2_size * sizeof(uint64_t))

        return NULL;

    /* update the l2 cache entry */

    s->l2_cache_offsets[min_index] = l2_offset;

    s->l2_cache_counts[min_index] = 1;

    return l2_table;

}

    int l1_index, l2_index, ret;

    uint64_t l2_offset, *l2_table, cluster_offset, tmp;

    /* seek the the l2 offset in the l1 table */

        ret = grow_l1_table(bs, l1_index + 1);

        if (ret < 0)

    /* seek the l2 table of the given l2 offset */

        /* the l2 table doesn't exist */

        /* allocate a new l2 table for this offset */

        l2_table = l2_allocate(bs, l1_index);

        if (l2_table == NULL)

        l2_offset = s->l1_table[l1_index] & ~QCOW_OFLAG_COPIED;

        /* the l2 table exists */

        if (!(l2_offset & QCOW_OFLAG_COPIED) && allocate) {

            /* duplicate the l2 table, and free the old table */

            free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t));

            l2_table = l2_allocate(bs, l1_index);

            if (l2_table == NULL)

                return 0;

            l2_offset = s->l1_table[l1_index] & ~QCOW_OFLAG_COPIED;

            /* load the l2 table in memory */

            l2_table = l2_load(bs, l2_offset);

            if (l2_table == NULL)

                return 0;

    /* find the cluster offset for the given disk offset */

        /* cluster doesn't exist */

            return 0;