函数fil_extend_space_to_desired_size

/**********************************************************************//**
Tries to extend a data file so that it would accommodate the number of pages
given. The tablespace must be cached in the memory cache. If the space is big
enough already, does nothing.
@return    TRUE if success */
UNIV_INTERN
ibool
fil_extend_space_to_desired_size(
/*=============================*/
    ulint*    actual_size,    /*!< out: size of the space after extension;
                if we ran out of disk space this may be lower
                than the desired size */
    ulint    space_id,    /*!< in: space id */
    ulint    size_after_extend)/*!< in: desired size in pages after the
                extension; if the current space size is bigger
                than this already, the function does nothing */
{
    fil_node_t*    node;
    fil_space_t*    space;
    byte*        buf2;
    byte*        buf;
    ulint        buf_size;
    ulint        start_page_no;
    ulint        file_start_page_no;
    ulint        offset_high;
    ulint        offset_low;
    ulint        page_size;
    ibool        success        = TRUE;

    fil_mutex_enter_and_prepare_for_io(space_id);

    space = fil_space_get_by_id(space_id);
    ut_a(space);

    if (space->size >= size_after_extend) {
        /* Space already big enough */

        *actual_size = space->size;

        mutex_exit(&fil_system->mutex);

        return(TRUE);
    }

    page_size = dict_table_flags_to_zip_size(space->flags);
    if (!page_size) {
        page_size = UNIV_PAGE_SIZE;
    }

    node = UT_LIST_GET_LAST(space->chain);

    fil_node_prepare_for_io(node, fil_system, space);

    start_page_no = space->size;
    file_start_page_no = space->size - node->size;

    /* Extend at most 64 pages at a time */
    buf_size = ut_min(64, size_after_extend - start_page_no) * page_size;
    buf2 = mem_alloc(buf_size + page_size);
    buf = ut_align(buf2, page_size);

    memset(buf, 0, buf_size);

    while (start_page_no < size_after_extend) {
        ulint    n_pages = ut_min(buf_size / page_size,
                     size_after_extend - start_page_no);

        offset_high = (start_page_no - file_start_page_no)
            / (4096 * ((1024 * 1024) / page_size));
        offset_low  = ((start_page_no - file_start_page_no)
                   % (4096 * ((1024 * 1024) / page_size)))
            * page_size;
#ifdef UNIV_HOTBACKUP
        success = os_file_write(node->name, node->handle, buf,
                    offset_low, offset_high,
                    page_size * n_pages);
#else
        success = os_aio(OS_FILE_WRITE, OS_AIO_SYNC,
                 node->name, node->handle, buf,
                 offset_low, offset_high,
                 page_size * n_pages,
                 NULL, NULL);
#endif
        if (success) {
            node->size += n_pages;
            space->size += n_pages;

            os_has_said_disk_full = FALSE;
        } else {
            /* Let us measure the size of the file to determine
            how much we were able to extend it */

            n_pages = ((ulint)
                   (os_file_get_size_as_iblonglong(
                       node->handle)
                    / page_size)) - node->size;

            node->size += n_pages;
            space->size += n_pages;

            break;
        }

        start_page_no += n_pages;
    }

    mem_free(buf2);

    fil_node_complete_io(node, fil_system, OS_FILE_WRITE);

    *actual_size = space->size;

#ifndef UNIV_HOTBACKUP
    if (space_id == 0) {
        ulint pages_per_mb = (1024 * 1024) / page_size;

        /* Keep the last data file size info up to date, rounded to
        full megabytes */

        srv_data_file_sizes[srv_n_data_files - 1]
            = (node->size / pages_per_mb) * pages_per_mb;
    }
#endif /* !UNIV_HOTBACKUP */

    /*
    printf("Extended %s to %lu, actual size %lu pages\n", space->name,
    size_after_extend, *actual_size); */
    mutex_exit(&fil_system->mutex);

    fil_flush(space_id);

    return(success);
}