Reading tag_array using output of metaArb in DCache

[ksungkeun84]

Hi,
I'm analyzing DCache, especially about how DCacheMetadataReq are formed for 8 requests arbtrated by metaArb.
I started with the tag read for cpu request ( 7th priority in metaArb) and the following is the code snippet to form the DCacheMetadataReq.

 metaArb.io.in(7).valid := io.cpu.req.valid
  metaArb.io.in(7).bits.write := false.B
  metaArb.io.in(7).bits.idx := dataArb.io.in(3).bits.addr(idxMSB, idxLSB)
  metaArb.io.in(7).bits.addr := io.cpu.req.bits.addr
  metaArb.io.in(7).bits.way_en := metaArb.io.in(4).bits.way_en
  metaArb.io.in(7).bits.data := metaArb.io.in(4).bits.data

I have two thing that I don't understand on the above code.

The first is about idx field.
As far as I understand, idx field should be extracted from the current request like io.cpu.req.bits.addr(idxMSG, idxLSB).
However, metaArb.io.in(3).bits.addr(idxMSB, idxLSB) is used which is a field of write request for refill.
This makes me confused my basic background of cache operation.
Can anyone help me understanding this?

The second is about way_en and data fields assigned by metaArb.io.in(4).
To read a section of cache blocks, idx is good enough and these fields are not used.
I just want to know if there is a specific reason to use way_en and data fields of `metaArb.io.in(4)'.
Do you have any idea on this?