Date: Wed, 17 Oct 2007 04:04:14 -0700 (PDT)
Message-Id: <20071017.040414.55507057.davem@davemloft.net>
To: jens.axboe@oracle.com
Cc: fujita.tomonori@lab.ntt.co.jp, linux-kernel@vger.kernel.org,
       linux-scsi@vger.kernel.org
Subject: Re: [PATCH] SPARC64: fix iommu sg chaining
From: David Miller <davem@davemloft.net>
In-Reply-To: <20071017105840.GT5043@kernel.dk>
References: <20071017091629.GK5043@kernel.dk>
	<20071017.035441.74746708.davem@davemloft.net>
	<20071017105840.GT5043@kernel.dk>
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From: Jens Axboe <jens.axboe@oracle.com>
Date: Wed, 17 Oct 2007 12:58:40 +0200

> The problem is that you cannot zero the entire sg entry, because then
> you'd potentially overwrite the chain pointer.
> 
> I'd propose just adding a
> 
>         sg_dma_address(sg) = 0;
>         sg_dma_len(sg) = 0;
> 
> there for now, or provide an arch_clear_sg_entry() helper if we need
> more killed.

The "chain pointer" is indicated by an sg->page with the low
bit set, but we're explicitly initializing it here to a
non-chain page pointer value.

What's the problem?
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