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Date: Sat, 1 Nov 2003 20:45:47 -0800
From: "David S. Miller" <davem@redhat.com>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: axboe@suse.de, linux-kernel@vger.kernel.org
Subject: Re: [BLOCK] phys_contig implies hw_contig
Message-Id: <20031101204547.1c861c42.davem@redhat.com>
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On Sat, 1 Nov 2003 13:31:27 +1100
Herbert Xu <herbert@gondor.apana.org.au> wrote:

> In ll_merge_requests_fn, it is checking blk_hw_contig_segments even if
> blk_phys_contig_segments succeeds.  This means that it may cause two
> physically contiguous segments to be separated because the hw check
> fails.

Your analysis assumes that phys contig implies hw contig, I
believe it does not.  There may be limitations in the VMERGE
mechanism a platform implements that causes this situation to
arise.