Date: Thu, 24 Jul 2008 22:21:52 -0700 (PDT)
Message-Id: <20080724.222152.193709632.davem@davemloft.net>
To: James.Bottomley@HansenPartnership.com
Cc: mpatocka@redhat.com, fujita.tomonori@lab.ntt.co.jp, jens.axboe@oracle.com,
       linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org,
       linux-parisc@vger.kernel.org
Subject: Re: [PATCH] block: fix q->max_segment_size checking in
 blk_recalc_rq_segments about VMERGE
From: David Miller <davem@davemloft.net>
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References: <Pine.LNX.4.64.0807241727320.12036@devserv.devel.redhat.com>
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From: James Bottomley <James.Bottomley@HansenPartnership.com>
Date: Thu, 24 Jul 2008 23:47:50 -0400

> I'm sorry sparc broke, really I am ... but you changed your iommu code
> from one with a working vmerge to one without and failed to turn off
> vmerging.  Partly it wasn't noticed because at 2*PAGE_SIZE you have a
> strange vmerge boundary, so it's harder to notice.   However, I can't
> extrapolate that just because this happened on sparc it will inevitably
> happen on all other architectures.

The vmerge boundary on sparc64 was 8K which is equal to sparc64's base
PAGE_SIZE.  I don't know where you get that 2*PAGE_SIZE from.

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