From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH 1/2] block: move the padding adjustment to blk_rq_map_sg Date: Thu, 10 Apr 2008 10:54:55 +0900 Message-ID: <47FD736F.9020404@gmail.com> References: <47FA2090.4040005@gmail.com> <20080408083526P.fujita.tomonori@lab.ntt.co.jp> <47FACF22.4010104@gmail.com> <20080408113732B.fujita.tomonori@lab.ntt.co.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from wa-out-1112.google.com ([209.85.146.182]:15553 "EHLO wa-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753306AbYDJBzC (ORCPT ); Wed, 9 Apr 2008 21:55:02 -0400 Received: by wa-out-1112.google.com with SMTP id v27so2394321wah.23 for ; Wed, 09 Apr 2008 18:55:02 -0700 (PDT) In-Reply-To: <20080408113732B.fujita.tomonori@lab.ntt.co.jp> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: FUJITA Tomonori Cc: linux-scsi@vger.kernel.org, tomof@acm.org, James.Bottomley@HansenPartnership.com, jens.axboe@oracle.com Hello, FUJITA. FUJITA Tomonori wrote: >>>>> The current code does padding only for requests that we call >>>>> __blk_rq_map_user (bio_copy_user) for. You meant that if we create a >>>>> new flag like REQ_NEED_PADDING and set it in blk_rq_map_user, >>>>> blk_rq_map_sg can do padding only when it was set. >>>> Yeap, that's what I meant. >>> Thanks, I see. Then, I have one question: blk_rq_map_user_iov doesn't >>> padding, thus libata still needs to adjust scatter list, right? >> Yes but it doesn't, so blk_rq_map_user_iov() path is essentially broken >> regarding padding at the moment. :-( > > I see. So we need to use bounce buffers for blk_rq_map_user_iov like > bio_copy_user does for blk_rq_map_user? Yeap. I think so. It would be great if we can do it where all the PC commands pass through so that blk_rq_map_useR_iov() and blk_rq_map_user() don't have to do it separately and as in your earlier patch it's probably best to move sg manipulation close to drain handling. Thanks. -- tejun