From: Andrea Arcangeli <andrea@qumranet.com>
Date: Wed, 2 Apr 2008 07:06:44 +0000 (+0200)
Subject: Fix bounce setting for 64-bit
X-Git-Tag: v2.6.25-rc9~101^2~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=00d61e3e8c12d5f395b167856d2b3c430816afb0;p=pandora-kernel.git

Fix bounce setting for 64-bit

Looking a bit closer into this regression the reason this can't be
right is that dma_addr common default is BLK_BOUNCE_HIGH and most
machines have less than 4G. So if you do:

    if (b_pfn <= (min_t(u64, 0xffffffff, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
	dma = 1

that will translate to:

     if (BLK_BOUNCE_HIGH <= BLK_BOUNCE_HIGH)
     	dma = 1

So for 99% of hardware this will trigger unnecessary GFP_DMA
allocations and isa pooling operations.

Also note how the 32bit code still does b_pfn < blk_max_low_pfn.

I guess this is what you were looking after. I didn't verify but as
far as I can tell, this will stop the regression with isa dma
operations at boot for 99% of blkdev/memory combinations out there and
I guess this fixes the setups with >4G of ram and 32bit pci cards as
well (this also retains symmetry with the 32bit code).

Signed-off-by: Andrea Arcangeli <andrea@qumranet.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
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