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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by aws-us-west-2-korg-lkml-1.web.codeaurora.org (Postfix) with ESMTP id 14353C004E4 for ; Wed, 13 Jun 2018 14:57:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BD359208B0 for ; Wed, 13 Jun 2018 14:57:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="EIItbh1k" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BD359208B0 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935892AbeFMO5c (ORCPT ); Wed, 13 Jun 2018 10:57:32 -0400 Received: from mail-qt0-f194.google.com ([209.85.216.194]:39381 "EHLO mail-qt0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935694AbeFMO51 (ORCPT ); Wed, 13 Jun 2018 10:57:27 -0400 Received: by mail-qt0-f194.google.com with SMTP id p23-v6so2626510qtn.6; Wed, 13 Jun 2018 07:57:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=JXOqPD9ykRA6j11QZ0bjBZxoKQX7Nu413MAVxDG9n2k=; b=EIItbh1kCEIJid+evZq2cWS9kFb2zmRaTfswwu2/GPJjs9vhUVnjE2Fe9U9tAtF+0Z MVi2c4ZOv+uQvyVnZ9IfO/eKlYNYcaAemfjyXw0n3vG4KCyEA5sHcQNONCo6TH2WbxcD 67OZwGNiY7nhu9B5dww0+SGVFO8rKWvq3i/EAfyNVl0eWNhAxtxXfeugvuwI426aFFUz DWFIS9UNgvkFpFCOtlkAtGCND1dKEDNdcvw1iSzw0m184wRsu3r/bfmlXwKZbI5iclpb MQgaNuVvXQKlrgl7xDjle+Rj6b2Vyyd/QtYx3cdAxE945jK5LgZyHomp/XwvnEr0vDbJ kYIQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=JXOqPD9ykRA6j11QZ0bjBZxoKQX7Nu413MAVxDG9n2k=; b=McUVzC1gW14co5CEZcUZ3VmxoBZsaoTbTKHe1DTCKLiS03Lt0wqAQGeDsBg8IaHWTX lNBarMEvIKLmuEWnGi6yCVOmoaquQ0n3r7gOjKD66RWR6UAXVBXSnAyH3TWJ0mDEYgz7 8xygh3ATIRVRrXI+i+LQxYr3URGAc5/RmUCWHX9uXe8aXtwL7KxwnpSDoP4mjU8HdHtk DwJR0OAFelB5vt5p/grC6wRP91oF05gEB2X9oZS8vX2+2MDB5BIESYNFOZyP9GsUTIm7 OYqC59/XigaR2hhpo4Dxaeq5XBY0vWb2uRrM8Mn8Ti0OELImmxzvl/zVmwkRkfTs/wo+ FpDQ== X-Gm-Message-State: APt69E0+spyYojz2BJCkkMpihg7Y3MTyJ5U8yKxS9ub1LjWkHE5RuPOF tkCLHr0je+9ZrddSKWeXzA== X-Google-Smtp-Source: ADUXVKKsw0OMEr7ndAwicd8e3Ka6BhIzcWkl+eK5vlNakEpNFwBDx49K6pge7heuBeyP9VTsfTdfnA== X-Received: by 2002:a0c:de13:: with SMTP id t19-v6mr4752154qvk.93.1528901846320; Wed, 13 Jun 2018 07:57:26 -0700 (PDT) Received: from kmo-pixel (c-71-234-172-214.hsd1.vt.comcast.net. [71.234.172.214]) by smtp.gmail.com with ESMTPSA id d11-v6sm2051632qto.41.2018.06.13.07.57.24 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 13 Jun 2018 07:57:25 -0700 (PDT) Date: Wed, 13 Jun 2018 10:57:22 -0400 From: Kent Overstreet To: Christoph Hellwig Cc: Ming Lei , Jens Axboe , Alexander Viro , David Sterba , 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 , Randy Dunlap Subject: Re: [PATCH V6 12/30] block: introduce bio_chunks() Message-ID: <20180613145722.GA17340@kmo-pixel> References: <20180609123014.8861-1-ming.lei@redhat.com> <20180609123014.8861-13-ming.lei@redhat.com> <20180613144741.GC4693@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180613144741.GC4693@infradead.org> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 13, 2018 at 07:47:41AM -0700, Christoph Hellwig wrote: > > +static inline unsigned bio_chunks(struct bio *bio) > > +{ > > + unsigned chunks = 0; > > + struct bio_vec bv; > > + struct bvec_iter iter; > > > > - return segs; > > + /* > > + * We special case discard/write same/write zeroes, because they > > + * interpret bi_size differently: > > + */ > > + switch (bio_op(bio)) { > > + case REQ_OP_DISCARD: > > + case REQ_OP_SECURE_ERASE: > > + case REQ_OP_WRITE_ZEROES: > > + return 0; > > + case REQ_OP_WRITE_SAME: > > + return 1; > > + default: > > + bio_for_each_chunk(bv, bio, iter) > > + chunks++; > > + return chunks; > > Shouldn't this just return bio->bi_vcnt? No. bio->bi_vcnt is only for the owner of a bio (the code that originally allocated it and filled it out) to use, and really the only legit use is bio_for_each_segment_all() (iterating over segments without using bi_iter because it's already been iterated to the end), and as a convenience thing for bio_add_page. Code that has a bio submitted to it can _not_ use bio->bi_vcnt, it's perfectly legal for it to be 0 (and it is for e.g. bio splits).