Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S944255AbcJaPgu (ORCPT ); Mon, 31 Oct 2016 11:36:50 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:55500 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S944191AbcJaPgr (ORCPT ); Mon, 31 Oct 2016 11:36:47 -0400 Date: Mon, 31 Oct 2016 08:36:44 -0700 From: Christoph Hellwig To: Ming Lei Cc: Jens Axboe , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, Christoph Hellwig , "Kirill A . Shutemov" , Chris Mason , Josef Bacik , David Sterba , "open list:BTRFS FILE SYSTEM" Subject: Re: [PATCH 26/60] btrfs: set NO_MP for request queues behind BTRFS Message-ID: <20161031153644.GK30919@infradead.org> References: <1477728600-12938-1-git-send-email-tom.leiming@gmail.com> <1477728600-12938-27-git-send-email-tom.leiming@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1477728600-12938-27-git-send-email-tom.leiming@gmail.com> User-Agent: Mutt/1.6.1 (2016-04-27) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 548 Lines: 11 On Sat, Oct 29, 2016 at 04:08:25PM +0800, Ming Lei wrote: > There are lots of direct access to .bi_vcnt & .bi_io_vec > of bio, and it isn't ready to support multipage bvecs > for BTRFS, so set NO_MP for these request queues. For one bio is an I/O submitter, it has absolutely no business changing queue flags - if we need to stick to this limitation it simply needs a version of bio_add_page that doesn't create multi-page bvecs. Second I don't think making it multipage bvec aware is all that hard, and we should aim for doing the proper thing.