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=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 80740C4320E for ; Fri, 27 Aug 2021 21:50:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5EC5D60FD8 for ; Fri, 27 Aug 2021 21:50:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231947AbhH0Vu4 (ORCPT ); Fri, 27 Aug 2021 17:50:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37480 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231906AbhH0Vuz (ORCPT ); Fri, 27 Aug 2021 17:50:55 -0400 Received: from mail-io1-xd2f.google.com (mail-io1-xd2f.google.com [IPv6:2607:f8b0:4864:20::d2f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 94A7AC0613D9; Fri, 27 Aug 2021 14:50:06 -0700 (PDT) Received: by mail-io1-xd2f.google.com with SMTP id b10so10509807ioq.9; Fri, 27 Aug 2021 14:50:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=+KgsOnOEWi0MydDQEQeoijmzmgKNc1F+KLYNS6ypl+A=; b=pHgixE2ebBEB316+s2X4JrzcqBhs+OqSZbzs5UREnQhRwsvyKxglF5MmqM6cLMPsyA quXyeg1KwG5P0AitBoTnZ43vRU9FRQsboYhDg1N3KINprdkIbzoNRaRvCWP/81pk6hez /Jue7oYOXui1uppyfoo3sECB+Wl/2Lavu0osaiEGXFZmy+6XS+MLKVsanDWZMFAy8GHc YHlx5S6LCHUq292jhfJMONk+Jik3a6uijo8O8bnzApZhNSCG/I4FFZy52l90MgN6ZaBG ULElUfz+NcWN1CXWcsXnBktInckZDFQFg6i2xHxE44qaviMX72kWDQo8YRVWHpebNBJC FnYQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=+KgsOnOEWi0MydDQEQeoijmzmgKNc1F+KLYNS6ypl+A=; b=UIairHg5qpek1FcPju3MT03K7uYJUPFLrqugiIogtH5R0bXulDpyU+bRgQNaW1Y7I5 iIwXLtPvpTYELoXLz2QomHUG/9C1EPBgOz+J1UDJbPSfMIbiPKWGmuU435xuXEF44oSV gtcWkpRc9POyEonP1sRTgWQRKesnbY29crNDRdU+agw+5V9k/ShhOUKKhkpNZp+FP5WR vatVl8xsfIYbx7nC2Ljd7ofE1f+XwRK5a2h1sMLjASsM8qec8oopYK3MLD5+kfJrQ5bc P+TY4EthpysoU5ew5NmUeUfab4ltjck3II894YfZHAuti06ZdJuHUi22PFAAhp06SFz1 zRow== X-Gm-Message-State: AOAM530mK0RLB6FRtV883BlB3NIomFHYmf0rmL7s8w9k8LrZZjz+TqPQ P8m4znb1GZiIBYXccZuCMH+5CGx3sdrpTq2+KzY= X-Google-Smtp-Source: ABdhPJzJRGOyoNLCUh6UJoKqoQ4Dj1Fl+MXsZg1MLQAg7cot2efKXxtZYUDwPF993DcRv83yJHOc/5bL3LKXA7e/b5o= X-Received: by 2002:a02:cf05:: with SMTP id q5mr9936733jar.132.1630101004796; Fri, 27 Aug 2021 14:50:04 -0700 (PDT) MIME-Version: 1.0 References: <20210827164926.1726765-1-agruenba@redhat.com> <20210827164926.1726765-17-agruenba@redhat.com> <20210827183018.GJ12664@magnolia> <20210827213239.GH12597@magnolia> In-Reply-To: <20210827213239.GH12597@magnolia> From: =?UTF-8?Q?Andreas_Gr=C3=BCnbacher?= Date: Fri, 27 Aug 2021 23:49:52 +0200 Message-ID: Subject: Re: [PATCH v7 16/19] iomap: Add done_before argument to iomap_dio_rw To: "Darrick J. Wong" Cc: Andreas Gruenbacher , Linus Torvalds , Alexander Viro , Christoph Hellwig , Jan Kara , Matthew Wilcox , cluster-devel , linux-fsdevel , LKML , ocfs2-devel@oss.oracle.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Am Fr., 27. Aug. 2021 um 23:33 Uhr schrieb Darrick J. Wong : > On Fri, Aug 27, 2021 at 10:15:11PM +0200, Andreas Gruenbacher wrote: > > On Fri, Aug 27, 2021 at 8:30 PM Darrick J. Wong wrote: > > > On Fri, Aug 27, 2021 at 06:49:23PM +0200, Andreas Gruenbacher wrote: > > > > Add a done_before argument to iomap_dio_rw that indicates how much of > > > > the request has already been transferred. When the request succeeds, we > > > > report that done_before additional bytes were tranferred. This is > > > > useful for finishing a request asynchronously when part of the request > > > > has already been completed synchronously. > > > > > > > > We'll use that to allow iomap_dio_rw to be used with page faults > > > > disabled: when a page fault occurs while submitting a request, we > > > > synchronously complete the part of the request that has already been > > > > submitted. The caller can then take care of the page fault and call > > > > iomap_dio_rw again for the rest of the request, passing in the number of > > > > bytes already tranferred. > > > > > > > > Signed-off-by: Andreas Gruenbacher > > > > --- > > > > fs/btrfs/file.c | 5 +++-- > > > > fs/ext4/file.c | 5 +++-- > > > > fs/gfs2/file.c | 4 ++-- > > > > fs/iomap/direct-io.c | 11 ++++++++--- > > > > fs/xfs/xfs_file.c | 6 +++--- > > > > fs/zonefs/super.c | 4 ++-- > > > > include/linux/iomap.h | 4 ++-- > > > > 7 files changed, 23 insertions(+), 16 deletions(-) > > > > > > > > > > > > > > > > > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c > > > > index ba88fe51b77a..dcf9a2b4381f 100644 > > > > --- a/fs/iomap/direct-io.c > > > > +++ b/fs/iomap/direct-io.c > > > > @@ -31,6 +31,7 @@ struct iomap_dio { > > > > atomic_t ref; > > > > unsigned flags; > > > > int error; > > > > + size_t done_before; > > > > bool wait_for_completion; > > > > > > > > union { > > > > @@ -126,6 +127,9 @@ ssize_t iomap_dio_complete(struct iomap_dio *dio) > > > > if (ret > 0 && (dio->flags & IOMAP_DIO_NEED_SYNC)) > > > > ret = generic_write_sync(iocb, ret); > > > > > > > > + if (ret > 0) > > > > + ret += dio->done_before; > > > > > > Pardon my ignorance since this is the first time I've had a crack at > > > this patchset, but why is it necessary to carry the "bytes copied" > > > count from the /previous/ iomap_dio_rw call all the way through to dio > > > completion of the current call? > > > > Consider the following situation: > > > > * A user submits an asynchronous read request. > > > > * The first page of the buffer is in memory, but the following > > pages are not. This isn't uncommon for consecutive reads > > into freshly allocated memory. > > > > * iomap_dio_rw writes into the first page. Then it > > hits the next page which is missing, so it returns a partial > > result, synchronously. > > > > * We then fault in the remaining pages and call iomap_dio_rw > > for the rest of the request. > > > > * The rest of the request completes asynchronously. > > > > Does that answer your question? > > No, because you totally ignored the second question: > > If the directio operation succeeds even partially and the PARTIAL flag > is set, won't that push the iov iter ahead by however many bytes > completed? Yes, exactly as it should. > We already finished the IO for the first page, so the second attempt > should pick up where it left off, i.e. the second page. Yes, so what's the question? Thanks, Andreas