Re: 2.6.22-rc1-mm1 - s390 vs. md

[Cornelia Huck <cornelia.huck@de.ibm.com>]

On Tue, 15 May 2007 20:19:14 -0700,
Andrew Morton <akpm@linux-foundation.org> wrote:

> ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.22-rc1/2.6.22-rc1-mm1/

Doesn't build on s390 when selecting the md menu:

drivers/built-in.o(.text+0x438ae): In function `async_xor':
: undefined reference to `dma_map_page'
drivers/built-in.o(.text+0x43aac): In function `async_xor':
: undefined reference to `dma_map_page'
drivers/built-in.o(.text+0x43d2e): In function `async_xor_zero_sum':
: undefined reference to `dma_map_page'
drivers/built-in.o(.text+0x43f50): In function `async_memcpy':
: undefined reference to `dma_map_page'
drivers/built-in.o(.text+0x43f90): In function `async_memcpy':
: undefined reference to `dma_map_page'
drivers/built-in.o(.text+0x4423e): more undefined references to
`dma_map_page' follow

This is caused by the following in drivers/md/Kconfig:

menuconfig MD
        bool "Multiple devices driver support (RAID and LVM)"
        depends on BLOCK
        select ASYNC_TX_DMA
        help
          Support multiple physical spindles through a single logical device.
          Required for RAID and logical volume management.

ASYNC_TX_DMA is defined in drivers/dma/Kconfig, which has

menu "DMA Engine support"
        depends on !S390

but unfortunately ASYNC_TX_DMA depends neither on the menu nor
on !S390. (I think it was just an unknown symbol on s390 before
Martin's Kconfig rework, so I could build older -mm kernels.)

Currently, the only md stuff depending on ASYNC_TX_DMA is MD_RAID456
(which means it doesn't work on s390 anymore, which is bad enough).
With the select statement, no md stuff can be build on s390 at all (and
I really don't see why ASYNC_TX_DMA should be forced upon all md
users)...
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