static int part_erase(struct mtd_info *mtd, struct erase_info *instr)
{
    struct mtd_part *part = mtd_to_part(mtd);
    int ret;
    size_t wrlen = 0;
    u8 *erase_buf = NULL;
    u32 erase_buf_ofs = 0;
    bool partial_start = false;

    if (mtd->flags & MTD_ERASE_PARTIAL) {
        size_t readlen = 0;
        u64 mtd_ofs;

        erase_buf = kmalloc(part->parent->erasesize, GFP_ATOMIC);
        if (!erase_buf)
            return -ENOMEM;

        mtd_ofs = part->offset + instr->addr;
        erase_buf_ofs = do_div(mtd_ofs, part->parent->erasesize);

        if (erase_buf_ofs > 0) {
            instr->addr -= erase_buf_ofs;
            ret = mtd_read(part->parent,
                instr->addr + part->offset,
                part->parent->erasesize,
                &readlen, erase_buf);

            instr->len += erase_buf_ofs;
            partial_start = true;
        } else {
            mtd_ofs = part->offset + part->mtd.size;
            erase_buf_ofs = part->parent->erasesize -
                do_div(mtd_ofs, part->parent->erasesize);

            if (erase_buf_ofs > 0) {
                instr->len += erase_buf_ofs;
                ret = mtd_read(part->parent,
                    part->offset + instr->addr +
                    instr->len - part->parent->erasesize,
                    part->parent->erasesize, &readlen,
                    erase_buf);
            } else {
                ret = 0;
            }
        }
        if (ret < 0) {
            kfree(erase_buf);
            return ret;
        }

    }

    instr->addr += part->offset;
    ret = part->parent->_erase(part->parent, instr);
    if (instr->fail_addr != MTD_FAIL_ADDR_UNKNOWN)
        instr->fail_addr -= part->offset;
    instr->addr -= part->offset;

    if (mtd->flags & MTD_ERASE_PARTIAL) {
        if (partial_start) {
            part->parent->_write(part->parent,
                instr->addr, erase_buf_ofs,
                &wrlen, erase_buf);
            instr->addr += erase_buf_ofs;
        } else {
            instr->len -= erase_buf_ofs;
            part->parent->_write(part->parent,
                instr->addr + instr->len,
                erase_buf_ofs, &wrlen,
                erase_buf +
                part->parent->erasesize -
                erase_buf_ofs);
        }
        kfree(erase_buf);
    }

    return ret;
}