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=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 F378DC43381 for ; Thu, 4 Mar 2021 15:03:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B139A64F86 for ; Thu, 4 Mar 2021 15:03:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232931AbhCDPCo (ORCPT ); Thu, 4 Mar 2021 10:02:44 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:44398 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232976AbhCDPCe (ORCPT ); Thu, 4 Mar 2021 10:02:34 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1614870068; 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=ejUN3tvqkFllhrARw3o33HWriTSZkp02yrNAR9+FPd0=; b=NwtiX86I7R5ItTqTzw+k47+Mr8comhnvYKAWmGL1LltJIFkwy6K+dlFFPW3GuW9wTj162G 7PhSdliPEKO0OMCyuHUiAincdkEBHOqqLcR1NxrEq0kctcdyuqBdq7v0n96Vk2EjkQUerV TOPof1T0SY+Y+vGoqVBeo2Dr0r+dVdw= 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-181-VzNcRQMZNeS97iJomllj_Q-1; Thu, 04 Mar 2021 10:01:04 -0500 X-MC-Unique: VzNcRQMZNeS97iJomllj_Q-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DBDA21019624; Thu, 4 Mar 2021 15:01:02 +0000 (UTC) Received: from segfault.boston.devel.redhat.com (segfault.boston.devel.redhat.com [10.19.60.26]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 60BBB5D705; Thu, 4 Mar 2021 15:00:58 +0000 (UTC) From: Jeff Moyer To: Mikulas Patocka Cc: JeffleXu , Mike Snitzer , Heinz Mauelshagen , axboe@kernel.dk, caspar@linux.alibaba.com, io-uring@vger.kernel.org, linux-block@vger.kernel.org, joseph.qi@linux.alibaba.com, dm-devel@redhat.com, hch@lst.de Subject: Re: [dm-devel] [PATCH 4/4] dm: support I/O polling References: <20210302190555.201228400@debian-a64.vm> <33fa121a-88a8-5c27-0a43-a7efc9b5b3e3@linux.alibaba.com> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 Date: Thu, 04 Mar 2021 10:01:38 -0500 In-Reply-To: (Mikulas Patocka's message of "Wed, 3 Mar 2021 05:09:18 -0500 (EST)") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org Hi, Mikulas, Mikulas Patocka writes: > On Wed, 3 Mar 2021, JeffleXu wrote: > >> >> >> On 3/3/21 3:05 AM, Mikulas Patocka wrote: >> >> > Support I/O polling if submit_bio_noacct_mq_direct returned non-empty >> > cookie. >> > >> > Signed-off-by: Mikulas Patocka >> > >> > --- >> > drivers/md/dm.c | 5 +++++ >> > 1 file changed, 5 insertions(+) >> > >> > Index: linux-2.6/drivers/md/dm.c >> > =================================================================== >> > --- linux-2.6.orig/drivers/md/dm.c 2021-03-02 19:26:34.000000000 +0100 >> > +++ linux-2.6/drivers/md/dm.c 2021-03-02 19:26:34.000000000 +0100 >> > @@ -1682,6 +1682,11 @@ static void __split_and_process_bio(stru >> > } >> > } >> > >> > + if (ci.poll_cookie != BLK_QC_T_NONE) { >> > + while (atomic_read(&ci.io->io_count) > 1 && >> > + blk_poll(ci.poll_queue, ci.poll_cookie, true)) ; >> > + } >> > + >> > /* drop the extra reference count */ >> > dec_pending(ci.io, errno_to_blk_status(error)); >> > } >> >> It seems that the general idea of your design is to >> 1) submit *one* split bio >> 2) blk_poll(), waiting the previously submitted split bio complets > > No, I submit all the bios and poll for the last one. What happens if the last bio completes first? It looks like you will call blk_poll with a cookie that already completed, and I'm pretty sure that's invalid. Thanks, Jeff