question about striped_read

[majianpeng <majianpeng@gmail.com>]

Hi all,
	I met a problem and ask somebody could help me.
In func striped_read()
> if (ret > 0) {
>                int didpages = (page_align + ret) >> PAGE_CACHE_SHIFT;

>                if (read < pos - off) {
>                       dout(" zero gap %llu to %llu\n", off + read, pos);
>                        ceph_zero_page_vector_range(page_align + read,
>                                                    pos - off - read, pages);
>                }   
>                pos += ret;
>               read = pos - off;

At first , pos = off and off don't modify.
Why does it judge 'read < pos -off ' ?
Because the read = pos -off, so the read must equal pos -off.

Thansk!
Jianpeng Ma