Re: LVM + Raid5 + make_request

From: Jan Kara (jack@suse.cz)
Date: Thu Jun 01 2000 - 05:41:29 EST


  Hello.

> I'm trying to get the LVM driver working over a raid5
> under 2.4.0-test1-ac2. There seems to be a problem with the
> LVM and raid5 make_request functions.
>
> "What we have here is a failure to comunnicate."
>
> LVM remaps the blocks by changing bh->b_rsector.
> Raid5 then ignores that field and looks at bh->b_blocknr.
> As a result, LVM LVs on a raid5 are broken. Seems this
> could be fixed one of three ways:
>
> 1) Have LVM change bh->b_blocknr.
> 2) Have Raid5 use bh->b_rsector instead of computing
> the sector from bh->b_blocknr.
  This is the right thing. I think there was some mail
in L-K from Andrea when he was rewriting ll_rw_blk that
this is the way drivers should go.

                                                Honza

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/



This archive was generated by hypermail 2b29 : Wed Jun 07 2000 - 21:00:12 EST