From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [patch for 2.6.33? 1/1] ata: call flush_dcache_page() around PIO data transfers in libata-aff.c Date: Wed, 3 Feb 2010 09:06:31 -0800 Message-ID: <20100203090631.44753f3b.akpm@linux-foundation.org> References: <1265151518.2800.715.camel@mulgrave.site> <20100202150537.0f6a01c0.akpm@linux-foundation.org> <4B68B1E0.4090004@pobox.com> <20100202.152140.216335166.davem@davemloft.net> <1265153568.2800.815.camel@mulgrave.site> <1265192325.1970.28.camel@pc1117.cambridge.arm.com> <1265215254.2873.201.camel@mulgrave.site> <4B69ABCA.1030507@pobox.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:53867 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932599Ab0BCRIz (ORCPT ); Wed, 3 Feb 2010 12:08:55 -0500 In-Reply-To: <4B69ABCA.1030507@pobox.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Jeff Garzik Cc: James Bottomley , Catalin Marinas , David Miller , jeff@garzik.org, linux-ide@vger.kernel.org, stable@kernel.org, tj@kernel.org On Wed, 03 Feb 2010 12:00:58 -0500 Jeff Garzik wrote: > On 02/03/2010 11:40 AM, James Bottomley wrote: > > The fix to libata looks to be just that it should kmap all the time > > rather than trying to fiddle with the page to see if its higmem. For > > kmap on a normal page, we should just return the offset map address and > > do all the flushing. > > libata tests PageHighMem() because it was measurably faster to do things > the current way (which includes local_irq_save/restore, only for > highmem) on boxes where it actually matters. > > It seems more efficient to add a flush where necessary, than > unconditionally punish everyone... kmap_atomic() tests PageHighMem() too - it's pretty lightweight for lowmem pages. Anyway, I'd draw your attention to this claim in the changelog: "This patch allows the ARM boards to use a rootfs on CompactFlash with the PATA platform driver." Immediate-term, we should be looking for a small fix for this issue which is acceptable for 2.6.33 and 2.6.32 and earlier.