From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DE2C8C4338F for ; Mon, 16 Aug 2021 11:41:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B95C76322D for ; Mon, 16 Aug 2021 11:41:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236254AbhHPLll (ORCPT ); Mon, 16 Aug 2021 07:41:41 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:20998 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236189AbhHPLlk (ORCPT ); Mon, 16 Aug 2021 07:41:40 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1629114068; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=zGrBBP0G4Srr7e/YCV954y2P30zJcDLWKXt/AZ5NHSg=; b=h894vgqfLOXhkUJ3hzhUWV8HSGZ+FCkrEpUAJt+3eFkwe8FiT4CT+AU4jRAm62bEGWvLQp tpgwVSsBYzitk2QLxajL/+fgkk8+wtr4EiJ5ifTpgoqzjxZBNldliFQIt42DBpT8EjnS1C fBGobqpSChbzYYVg6U8QrhcY6WdanfU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-224-ajuQk1g8O-qoabvWEmqytg-1; Mon, 16 Aug 2021 07:41:05 -0400 X-MC-Unique: ajuQk1g8O-qoabvWEmqytg-1 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 mimecast-mx01.redhat.com (Postfix) with ESMTPS id 44A6E1082925; Mon, 16 Aug 2021 11:41:04 +0000 (UTC) Received: from T590 (ovpn-8-40.pek2.redhat.com [10.72.8.40]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 51E9B60FB8; Mon, 16 Aug 2021 11:40:54 +0000 (UTC) Date: Mon, 16 Aug 2021 19:40:48 +0800 From: Ming Lei To: Christoph Hellwig Cc: Guoqing Jiang , song@kernel.org, linux-raid@vger.kernel.org, jens@chianterastutte.eu, linux-block@vger.kernel.org Subject: Re: [PATCH] raid1: ensure bio doesn't have more than BIO_MAX_VECS sectors Message-ID: References: <20210813060510.3545109-1-guoqing.jiang@linux.dev> <0eac4589-ffd2-fb1a-43cc-87722731438a@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org On Mon, Aug 16, 2021 at 10:37:54AM +0100, Christoph Hellwig wrote: > On Sat, Aug 14, 2021 at 04:57:06PM +0800, Ming Lei wrote: > > > + if (bitmap) > > > + max_sectors = min_t(int, max_sectors, BIO_MAX_VECS * PAGE_SIZE); > > > > s/PAGE_SIZE/PAGE_SECTORS > > Yeah, max_sectors is in size units, I messed that up. > > > > > > + > > > if (max_sectors < bio_sectors(bio)) { > > > struct bio *split = bio_split(bio, max_sectors, > > > GFP_NOIO, &conf->bio_split); > > > > > > > Here the limit is max single-page vectors, and the above way may not work, > > such as: > > > > 0 ~ 254: each bvec's length is 512 > > 255: bvec's length is 8192 > > > > the total length is just 512*255 + 8192 = 138752 bytes = 271 sectors, but it > > still may need 257 bvecs, which can't be allocated via bio_alloc_bioset(). > > Yes, we still need the rounding magic that alloc_behind_master_bio uses > here. But it is wrong to use max sectors to limit number of bvecs(segments), isn't it? Thanks, Ming