From patchwork Mon Dec 18 12:22:20 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming Lei X-Patchwork-Id: 10119195 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 BFEDD6057F for ; Mon, 18 Dec 2017 12:28:12 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B210228FBA for ; Mon, 18 Dec 2017 12:28:12 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A6E6828FC4; Mon, 18 Dec 2017 12:28:12 +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=unavailable 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 504AA28FBA for ; Mon, 18 Dec 2017 12:28:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752941AbdLRM15 (ORCPT ); Mon, 18 Dec 2017 07:27:57 -0500 Received: from mx1.redhat.com ([209.132.183.28]:44842 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752743AbdLRM1y (ORCPT ); Mon, 18 Dec 2017 07:27:54 -0500 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 476448210C; Mon, 18 Dec 2017 12:27:54 +0000 (UTC) Received: from localhost (ovpn-12-48.pek2.redhat.com [10.72.12.48]) by smtp.corp.redhat.com (Postfix) with ESMTP id 23C4A7E204; Mon, 18 Dec 2017 12:27:10 +0000 (UTC) From: Ming Lei To: Jens Axboe , Christoph Hellwig , Alexander Viro , Kent Overstreet Cc: Huang Ying , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Theodore Ts'o , "Darrick J . Wong" , Coly Li , Filipe Manana , Ming Lei Subject: [PATCH V4 18/45] block: introduce multipage page bvec helpers Date: Mon, 18 Dec 2017 20:22:20 +0800 Message-Id: <20171218122247.3488-19-ming.lei@redhat.com> In-Reply-To: <20171218122247.3488-1-ming.lei@redhat.com> References: <20171218122247.3488-1-ming.lei@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Mon, 18 Dec 2017 12:27:54 +0000 (UTC) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP This patch introduces helpers of 'bvec_iter_segment_*' for multipage bvec(segment) support. The introduced interfaces treate one bvec as real multipage segment, for example, .bv_len is the total length of the multipage segment. The existed helpers of bvec_iter_* are interfaces for supporting current bvec iterator which is thought as singlepage only by drivers, fs, dm and etc. These helpers will build singlepage bvec in flight, so users of current bio/bvec iterator still can work well and needn't change even though we store real multipage segment into bvec table. Signed-off-by: Ming Lei --- include/linux/bvec.h | 63 +++++++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 60 insertions(+), 3 deletions(-) diff --git a/include/linux/bvec.h b/include/linux/bvec.h index fe7a22dd133b..2433c73fa5ea 100644 --- a/include/linux/bvec.h +++ b/include/linux/bvec.h @@ -23,6 +23,44 @@ #include #include #include +#include + +/* + * What is multipage bvecs(segment)? + * + * - bvec stored in bio->bi_io_vec is always multipage(mp) style + * + * - 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_page() still returns bvec with single page + * + * - bio_for_each_page_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 multipage bvec(segment) + * + * - In case that some components(such as iov_iter) need to support + * multipage segment, we introduce new helpers(bvec_iter_segment_*) for + * them. + */ /* * was unsigned short, but we might as well be ready for > 64kB I/O pages @@ -52,16 +90,35 @@ struct bvec_iter { */ #define __bvec_iter_bvec(bvec, iter) (&(bvec)[(iter).bi_idx]) -#define bvec_iter_page(bvec, iter) \ +#define bvec_iter_segment_page(bvec, iter) \ (__bvec_iter_bvec((bvec), (iter))->bv_page) -#define bvec_iter_len(bvec, iter) \ +#define bvec_iter_segment_len(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_segment_offset(bvec, iter) \ (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done) +#define bvec_iter_page_idx_in_seg(bvec, iter) \ + (bvec_iter_segment_offset((bvec), (iter)) / PAGE_SIZE) + +/* + * of singlepage(sp) segment. + * + * This helpers will be implemented for building sp bvec in flight. + */ +#define bvec_iter_offset(bvec, iter) \ + (bvec_iter_segment_offset((bvec), (iter)) % PAGE_SIZE) + +#define bvec_iter_len(bvec, iter) \ + min_t(unsigned, bvec_iter_segment_len((bvec), (iter)), \ + (PAGE_SIZE - (bvec_iter_offset((bvec), (iter))))) + +#define bvec_iter_page(bvec, iter) \ + nth_page(bvec_iter_segment_page((bvec), (iter)), \ + bvec_iter_page_idx_in_seg((bvec), (iter))) + #define bvec_iter_bvec(bvec, iter) \ ((struct bio_vec) { \ .bv_page = bvec_iter_page((bvec), (iter)), \