Subject: Re[2]: [PATCH 01/11] async_tx: don't use src_list argument of async_xor() for dma addresses

From: Yuri Tikhonov <[email-masked]>
Date: Tue, 9 Dec 2008 03:41:36 +0300

On Tuesday, December 9, 2008 you wrote:

> On Mon, Dec 8, 2008 at 2:55 PM, Yuri Tikhonov <[email-masked]> wrote:
>> Using src_list argument of async_xor() as a storage for dma addresses
>> implies sizeof(dma_addr_t) <=3D sizeof(struct page *) restriction which =
is
>> not always true (e.g. ppc440spe).
>>

> ppc440spe runs with CONFIG_PHYS_64BIT?

 Yep. It uses 36-bit addressing, so this CONFIG is turned on.

> If we do this then we need to also change md to limit the number of
> allowed disks based on the kernel stack size.  Because with 256 disks
> a 4K stack can be consumed by one call to async_pq ((256 sources in
> raid5.c + 256 sources async_pq.c) * 8 bytes per source on 64-bit).

 On ppc440spe we have 8KB stack, so the things are not worse than on=20
32-bit archs with 4KB stack. Thus, I guess no changes to md are=20
required because of this patch. Right?

 Regards, Yuri

 --
 Yuri Tikhonov, Senior Software Engineer
 Emcraft Systems, www.emcraft.com