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From: Roland Dreier <rdreier@cisco.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	<linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	<linux-scsi@vger.kernel.org>, <rmk@arm.linux.org.uk>,
	<davem@davemloft.net>, <james.bottomley@steeleye.com>,
	<ralf@linux-mips.org>
Subject: Re: [PATCH 2/2] scsi: Use new __dma_buffer to align sense buffer in scsi_cmnd
Date: Fri, 21 Dec 2007 08:57:47 -0800	[thread overview]
Message-ID: <adak5n8x9x0.fsf@cisco.com> (raw)
In-Reply-To: <20071221103326.7ce1bc4f@the-village.bc.nu> (Alan Cox's message of "Fri, 21 Dec 2007 10:33:26 +0000")

 > It's also incomplete as a fix because I don't see what guarantees the
 > buffer size will always exceed cache line size

There's a macro trick that adds a pad member after the buffer too, so
that it gets rounded up to the cacheline size:

 > +#define __dma_aligned	  	__attribute__((aligned(ARCH_MIN_DMA_ALIGNMENT)))
 > +#define __dma_buffer		__dma_buffer_line(__LINE__)
 > +#define __dma_buffer_line(line)	__dma_aligned;\
 > +				char __dma_pad_##line[0] __dma_aligned

So that part is OK at least.

 - R.

  parent reply	other threads:[~2007-12-21 16:58 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-12-21  2:30 [PATCH 2/2] scsi: Use new __dma_buffer to align sense buffer in scsi_cmnd Benjamin Herrenschmidt
2007-12-21 10:33 ` Alan Cox
2007-12-21 13:16   ` Matthew Wilcox
2007-12-21 13:30     ` Thomas Bogendoerfer
2007-12-21 14:00       ` Matthew Wilcox
2007-12-21 16:35         ` Thomas Bogendoerfer
2007-12-21 21:29     ` Benjamin Herrenschmidt
2007-12-21 16:57   ` Roland Dreier [this message]
2007-12-21 21:27   ` Benjamin Herrenschmidt
2007-12-23 11:09 ` Boaz Harrosh
2007-12-23 23:04   ` Benjamin Herrenschmidt
2008-01-07  6:53   ` FUJITA Tomonori
2008-01-07 13:25     ` Boaz Harrosh
2008-01-07 23:32       ` FUJITA Tomonori

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