From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Dharm Subject: Re: [patchset 0/5] Refactoring scsi_error to facilitate in synchronous REQUEST_SENSE Date: Mon, 10 Sep 2007 10:03:34 -0700 Message-ID: <20070910170334.GA12369@one-eyed-alien.net> References: <46E5508B.7030108@panasas.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="UlVJffcvxoiEqYs2" Return-path: Received: from adsl-67-113-118-6.dsl.sndg02.pacbell.net ([67.113.118.6]:58456 "EHLO multivac.one-eyed-alien.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756716AbXIJRD4 (ORCPT ); Mon, 10 Sep 2007 13:03:56 -0400 Content-Disposition: inline In-Reply-To: <46E5508B.7030108@panasas.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Boaz Harrosh Cc: James Bottomley , FUJITA Tomonori , linux-scsi , Alan Stern , Greg Kroah-Hartman , Christoph Hellwig --UlVJffcvxoiEqYs2 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Sep 10, 2007 at 05:11:23PM +0300, Boaz Harrosh wrote: >=20 > In motivation to abstract scsi_cmnd members and insulate > drivers/transports from scsi_cmnd internals. The last > place left was the REQUEST_SENSE sequence when done > synchronous, by drivers. This probably isn't serious, but I noticed one thing (beyond what Alan's analysis noted)... I've always assumed that the scatterlist structs passed to an HCD were, themselves, allocated from DMA-able memory. That is, not just the transfer buffers themselves, but the struct scatterlist also. In this implementation, the struct scatterlist used for the single-element transfer of the request sense buffer is part of the struct scsi_eh_save_cmnd_info, which is allocated on the stack (for at least usb-storage). And, stack isn't DMA-able on all arches. It is not a problem for usb-storage, since the struct scatterlists are processed in code into a series of URBs, so nobody actually does DMA the scatterlist structures. However, I don't know enough about the other HCDs to be certain about them. Matt --=20 Matthew Dharm Home: mdharm-usb@one-eyed-alien.= net=20 Maintainer, Linux USB Mass Storage Driver Now payink attention, please. This is mouse. Click-click. Easy to=20 use, da? Now you try... -- Pitr to Miranda User Friendly, 10/11/1998 --UlVJffcvxoiEqYs2 Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (GNU/Linux) iD8DBQFG5XjmHL9iwnUZqnkRArtiAJ9fhLHcvnhqTRsVvIkUYlP/K/U0HACgsK+T 1+PmotIQY0gUeBpw0sl1+QU= =zCQM -----END PGP SIGNATURE----- --UlVJffcvxoiEqYs2--