From patchwork Mon Jun 26 12:10:03 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming Lei X-Patchwork-Id: 9809477 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 605DA60209 for ; Mon, 26 Jun 2017 12:27:33 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 66390274D1 for ; Mon, 26 Jun 2017 12:27:33 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 5A1F328582; Mon, 26 Jun 2017 12:27:33 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id ECB76274D1 for ; Mon, 26 Jun 2017 12:27:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752020AbdFZM1a (ORCPT ); Mon, 26 Jun 2017 08:27:30 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44420 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752651AbdFZMQK (ORCPT ); Mon, 26 Jun 2017 08:16:10 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 214AB80F7B; Mon, 26 Jun 2017 12:16:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 214AB80F7B Authentication-Results: ext-mx03.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx03.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=ming.lei@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 214AB80F7B Received: from localhost (ovpn-12-86.pek2.redhat.com [10.72.12.86]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4177380F7C; Mon, 26 Jun 2017 12:15:59 +0000 (UTC) From: Ming Lei To: Jens Axboe , Christoph Hellwig , Huang Ying , Andrew Morton , Alexander Viro Cc: linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Ming Lei Subject: [PATCH v2 20/51] block: introduce multipage/single page bvec helpers Date: Mon, 26 Jun 2017 20:10:03 +0800 Message-Id: <20170626121034.3051-21-ming.lei@redhat.com> In-Reply-To: <20170626121034.3051-1-ming.lei@redhat.com> References: <20170626121034.3051-1-ming.lei@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Mon, 26 Jun 2017 12:16:10 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP This patch introduces helpers which are suffixed with _mp and _sp for the multipage bvec/segment support. The helpers with _mp suffix are the interfaces for treating one bvec/segment as real multipage one, for example, .bv_len is the total length of the multipage segment. The helpers with _sp suffix are interfaces for supporting current bvec iterator which is thought as singlepage only by drivers, fs, dm and etc. These _sp helpers are introduced to build singlepage bvec in flight, so users of bio/bvec iterator still can work well and needn't change even though we store multipage into bvec. Signed-off-by: Ming Lei --- include/linux/bvec.h | 56 +++++++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 53 insertions(+), 3 deletions(-) diff --git a/include/linux/bvec.h b/include/linux/bvec.h index 162ca7caf510..f52587e283d4 100644 --- a/include/linux/bvec.h +++ b/include/linux/bvec.h @@ -24,6 +24,42 @@ #include /* + * What is multipage bvecs(segment)? + * + * - bvec stored in bio->bi_io_vec is always multipage style vector + * + * - bvec(struct bio_vec) represents one physically contiguous I/O + * buffer, now the buffer may include more than one pages since + * multipage(mp) bvec is supported, and all these pages represented + * by one bvec is physically contiguous. Before mp support, at most + * one page can be included in one bvec, we call it singlepage(sp) + * bvec. + * + * - .bv_page of th bvec represents the 1st page in the mp segment + * + * - .bv_offset of the bvec represents offset of the buffer in the bvec + * + * The effect on the current drivers/filesystem/dm/bcache/...: + * + * - almost everyone supposes that one bvec only includes one single + * page, so we keep the sp interface not changed, for example, + * bio_for_each_segment() still returns bvec with single page + * + * - bio_for_each_segment_all() will be changed to return singlepage + * bvec too + * + * - during iterating, iterator variable(struct bvec_iter) is always + * updated in multipage bvec style and that means bvec_iter_advance() + * is kept not changed + * + * - returned(copied) singlepage bvec is generated in flight by bvec + * helpers from the stored mp bvec + * + * - In case that some components(such as iov_iter) need to support mp + * segment, we introduce new helpers(suffixed with _mp) for them. + */ + +/* * was unsigned short, but we might as well be ready for > 64kB I/O pages */ struct bio_vec { @@ -49,16 +85,30 @@ struct bvec_iter { */ #define __bvec_iter_bvec(bvec, iter) (&(bvec)[(iter).bi_idx]) -#define bvec_iter_page(bvec, iter) \ +#define bvec_iter_page_mp(bvec, iter) \ (__bvec_iter_bvec((bvec), (iter))->bv_page) -#define bvec_iter_len(bvec, iter) \ +#define bvec_iter_len_mp(bvec, iter) \ min((iter).bi_size, \ __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done) -#define bvec_iter_offset(bvec, iter) \ +#define bvec_iter_offset_mp(bvec, iter) \ (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done) +/* + * of singlepage(sp) segment. + * + * This helpers will be implemented for building sp bvec in flight. + */ +#define bvec_iter_offset_sp(bvec, iter) bvec_iter_offset_mp((bvec), (iter)) +#define bvec_iter_len_sp(bvec, iter) bvec_iter_len_mp((bvec), (iter)) +#define bvec_iter_page_sp(bvec, iter) bvec_iter_page_mp((bvec), (iter)) + +/* current interfaces support sp style at default */ +#define bvec_iter_page(bvec, iter) bvec_iter_page_sp((bvec), (iter)) +#define bvec_iter_len(bvec, iter) bvec_iter_len_sp((bvec), (iter)) +#define bvec_iter_offset(bvec, iter) bvec_iter_offset_sp((bvec), (iter)) + #define bvec_iter_bvec(bvec, iter) \ ((struct bio_vec) { \ .bv_page = bvec_iter_page((bvec), (iter)), \