函数fsp_alloc_seg_inode

/**********************************************************************//**
Allocates a new file segment inode.
@return    segment inode, or NULL if not enough space */
static
fseg_inode_t*
fsp_alloc_seg_inode(
/*================*/
    fsp_header_t*    space_header,    /*!< in: space header */
    mtr_t*        mtr)        /*!< in: mini-transaction handle */
{
    ulint        page_no;
    buf_block_t*    block;
    page_t*        page;
    fseg_inode_t*    inode;
    ibool        success;
    ulint        zip_size;
    ulint        n;

    ut_ad(page_offset(space_header) == FSP_HEADER_OFFSET);

    if (flst_get_len(space_header + FSP_SEG_INODES_FREE, mtr) == 0) {
        /* Allocate a new segment inode page */

        success = fsp_alloc_seg_inode_page(space_header, mtr);//申请innode page,详见
        if (!success) {
            return(NULL);
        }
    }

    page_no = flst_get_first(space_header + FSP_SEG_INODES_FREE, mtr).page; //详见

    zip_size = dict_table_flags_to_zip_size(mach_read_from_4(FSP_SPACE_FLAGS + space_header));
    
    /**
     *page_align 详见
     *page_get_space_id 详见
     *buf_page_get  详见
     *
     */
    block = buf_page_get(page_get_space_id(page_align(space_header)),zip_size, page_no, RW_X_LATCH, mtr);

    buf_block_dbg_add_level(block, SYNC_FSP_PAGE);

    page = buf_block_get_frame(block);

    n = fsp_seg_inode_page_find_free(page, 0, zip_size, mtr);//详见

    ut_a(n != ULINT_UNDEFINED);

    inode = fsp_seg_inode_page_get_nth_inode(page, n, zip_size, mtr);//得到第N个inode entry

    if (ULINT_UNDEFINED == fsp_seg_inode_page_find_free(page, n + 1,zip_size, mtr)) { //查看是否有空余的seg inode entry 详见
      /* There are no other unused headers left on the page: move it to another list */
        /**
         *#define FSEG_INODE_PAGE_NODE FSEG_PAGE_DATA
         *#define FSEG_PAGE_DATA FIL_PAGE_DATA
         *#define FIL_PAGE_DATA 38
         */
        flst_remove(space_header + FSP_SEG_INODES_FREE,
                page + FSEG_INODE_PAGE_NODE, mtr);

        flst_add_last(space_header + FSP_SEG_INODES_FULL,
                  page + FSEG_INODE_PAGE_NODE, mtr);
    }

    ut_ad(!mach_read_from_8(inode + FSEG_ID)
          || mach_read_from_4(inode + FSEG_MAGIC_N) == FSEG_MAGIC_N_VALUE);
    return(inode);
}