From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758159Ab0BXVSK (ORCPT ); Wed, 24 Feb 2010 16:18:10 -0500 Received: from gate.crashing.org ([63.228.1.57]:51916 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758074Ab0BXVSF (ORCPT ); Wed, 24 Feb 2010 16:18:05 -0500 Subject: Re: USB mass storage and ARM cache coherency From: Benjamin Herrenschmidt To: Alan Stern Cc: Catalin Marinas , Matthew Dharm , linux-usb@vger.kernel.org, Russell King - ARM Linux , "Mankad,Maulik Ojas" , Sergei Shtylyov , Ming Lei , Sebastian Siewior , Oliver Neukum , linux-kernel , "Shilimkar,Santosh" , Pavel Machek , Greg KH , linux-arm-kernel , James Bottomley In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Date: Thu, 25 Feb 2010 08:13:56 +1100 Message-ID: <1267046036.23523.1693.camel@pasglop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2010-02-24 at 11:19 -0500, Alan Stern wrote: > > It is but I'm not confident the responsibility for doing that > cleanup > > is at the HCD level. That would impact a lot of HCD activities that > > don't need such flushing since the use of the page is purely > in-kernel. > > That's right. The HCD merely puts data wherever it's told to. It > doesn't know whether the destination is in the page cache, in > userspace, or anywhere else. The same is true for usb-storage. I'm surprised that usb-storage has an issue here. It shouldn't afaik, since it's just a SCSI driver (or not anymore ?) and the BIO or filesystems handle things there no ? I haven't seen a single call to flush_dcache_page() in any of drivers/scsi, drivers/ata or drivers/ide when I looked... Cheers, Ben. From mboxrd@z Thu Jan 1 00:00:00 1970 From: benh@kernel.crashing.org (Benjamin Herrenschmidt) Date: Thu, 25 Feb 2010 08:13:56 +1100 Subject: USB mass storage and ARM cache coherency In-Reply-To: References: Message-ID: <1267046036.23523.1693.camel@pasglop> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, 2010-02-24 at 11:19 -0500, Alan Stern wrote: > > It is but I'm not confident the responsibility for doing that > cleanup > > is at the HCD level. That would impact a lot of HCD activities that > > don't need such flushing since the use of the page is purely > in-kernel. > > That's right. The HCD merely puts data wherever it's told to. It > doesn't know whether the destination is in the page cache, in > userspace, or anywhere else. The same is true for usb-storage. I'm surprised that usb-storage has an issue here. It shouldn't afaik, since it's just a SCSI driver (or not anymore ?) and the BIO or filesystems handle things there no ? I haven't seen a single call to flush_dcache_page() in any of drivers/scsi, drivers/ata or drivers/ide when I looked... Cheers, Ben.