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_INVALID,DKIM_SIGNED, 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 6BEB9C33CA9 for ; Mon, 13 Jan 2020 22:10:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3FFC72084D for ; Mon, 13 Jan 2020 22:10:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="V+o4mHVp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728714AbgAMWKs (ORCPT ); Mon, 13 Jan 2020 17:10:48 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:45048 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727382AbgAMWKs (ORCPT ); Mon, 13 Jan 2020 17:10:48 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=iiatjSK+rStDx5yHwZUI6kusSNUrnB2tu8ZxYcMa6Lw=; b=V+o4mHVpSIrVUgND6g6d6216j C/6cpAwvBjIA0PgMlkugnc3UZYigzupLZAfBEQKWwzJAjylcHqfQrab1Hp5yOv9V15mS2Sz/VXK+u nxuY2JiqZGHsPJ/XF5b5tAFrNS5TloZ+6y0sirsXq9QHxShL0/G+IDekM6dhutfrQv4hHzbvBrH1E EBe6Jv0SGbqq4F0S8Qv4/LegR5bXwvDxO7mlzZaGvh+Z849fpOnZ2GJy+hX78sb4XPpOuwX3+fblh YqtKdyRdBgK0FSw3Feb5gN5g738GiphuM1dK0T0yQYVCsolDALtj7D/wPxBuGqiaKBQnF5e6jIDQi PIy6SAHWA==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1ir7v5-0007Xf-TZ; Mon, 13 Jan 2020 22:10:47 +0000 Date: Mon, 13 Jan 2020 14:10:47 -0800 From: Matthew Wilcox To: Jens Axboe Cc: Chris Mason , "linux-xfs@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "jlayton@kernel.org" , "hch@infradead.org" Subject: Re: [RFC 0/8] Replacing the readpages a_op Message-ID: <20200113221047.GB18216@bombadil.infradead.org> References: <20200113153746.26654-1-willy@infradead.org> <6CA4CD96-0812-4261-8FF9-CD28AA2EC38A@fb.com> <20200113174008.GB332@bombadil.infradead.org> <15C84CC9-3196-441D-94DE-F3FD7AC364F0@fb.com> <20200113215811.GA18216@bombadil.infradead.org> <910af281-4e2b-3e5d-5533-b5ceafd59665@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <910af281-4e2b-3e5d-5533-b5ceafd59665@kernel.dk> Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Mon, Jan 13, 2020 at 03:00:40PM -0700, Jens Axboe wrote: > On 1/13/20 2:58 PM, Matthew Wilcox wrote: > > On Mon, Jan 13, 2020 at 06:00:52PM +0000, Chris Mason wrote: > >> This is true, I didn't explain that part well ;) Depending on > >> compression etc we might end up poking the xarray inside the actual IO > >> functions, but the main difference is that btrfs is building a single > >> bio. You're moving the plug so you'll merge into single bio, but I'd > >> rather build 2MB bios than merge them. > > > > Why don't we store a bio pointer inside the plug? You're opencoding that, > > iomap is opencoding that, and I bet there's a dozen other places where > > we pass a bio around. Then blk_finish_plug can submit the bio. > > Plugs aren't necessarily a bio, they can be callbacks too. I'm thinking something as simple as this: @@ -1711,6 +1711,7 @@ void blk_start_plug(struct blk_plug *plug) INIT_LIST_HEAD(&plug->mq_list); INIT_LIST_HEAD(&plug->cb_list); + plug->bio = NULL; plug->rq_count = 0; plug->multiple_queues = false; @@ -1786,6 +1787,8 @@ void blk_finish_plug(struct blk_plug *plug) { if (plug != current->plug) return; + if (plug->bio) + submit_bio(plug->bio); blk_flush_plug_list(plug, false); current->plug = NULL; @@ -1160,6 +1160,7 @@ extern void blk_set_queue_dying(struct request_queue *); struct blk_plug { struct list_head mq_list; /* blk-mq requests */ struct list_head cb_list; /* md requires an unplug callback */ + struct bio *bio; unsigned short rq_count; bool multiple_queues; }; with accessors to 'get_current_bio()' and 'set_current_bio()'.