[ewg] Mellanox target workaround in SRP

[David Dillow]

On Mon, 2011-01-10 at 10:49 -0800, Roland Dreier wrote:
> > I think that the patch is specific for srp initiator using Mellanox
>  > FMR. It tried to avoid indirect desc with Mellanox FMR having
>  > first-byte-offset != 0.  Since the low level implementation of
>  > mlx4/mthca_map_phys_fmr() did not create + setup MPT for FMR with
>  > first_byte_offset != 0. The corruption can happen with any target.
> 
> I don't think this could be right -- right now the workaround only
> triggers if the target has a Mellanox OUI, so if what you say is true,
> presumably everyone who is using the SRP initiator with mlx4 would be
> seeing this problem.

Only if they are using less than 4 KB logical blocks it seems, or
perhaps certain sg3-util commands to directly send SCSI commands. We
should be getting page-aligned IO for 4 KB filesystems, so we probably
wouldn't hit this.

-- 
Dave Dillow
National Center for Computational Science
Oak Ridge National Laboratory
(865) 241-6602 office