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Date:   Wed, 8 Sep 2021 08:49:58 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Junio C Hamano <gitster@pobox.com>
Cc:     Neeraj Singh <nksingh85@gmail.com>,
        "Neeraj K. Singh via GitGitGadget" <gitgitgadget@gmail.com>,
        Git List <git@vger.kernel.org>,
        Johannes Schindelin <Johannes.Schindelin@gmx.de>,
        Jeff King <peff@peff.net>,
        Jeff Hostetler <jeffhost@microsoft.com>,
        Christoph Hellwig <hch@lst.de>,
        =?iso-8859-1?Q?=C6var_Arnfj=F6r=F0?= Bjarmason <avarab@gmail.com>,
        "Neeraj K. Singh" <neerajsi@microsoft.com>
Subject: Re: [PATCH v2 0/6] Implement a batched fsync option for
 core.fsyncObjectFiles
Message-ID: <20210908064958.GA29073@lst.de>
References: <pull.1076.git.git.1629856292.gitgitgadget@gmail.com> <pull.1076.v2.git.git.1630108177.gitgitgadget@gmail.com> <CANQDOdeEic1ktyGU=dLEPi=FkU84Oqv9hDUEkfAXcS0WTwRJtQ@mail.gmail.com> <CANQDOdeX-SoWnh5DJ9ZdNLfPdAW-wtp_fo99r0Rwe1DQqx4W5Q@mail.gmail.com> <xmqqmton7ehn.fsf@gitster.g>
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On Tue, Sep 07, 2021 at 11:44:52PM -0700, Junio C Hamano wrote:
> I doubt that fsyncObjectFiles is something we can reliably test in
> CI, either with the new batched thing or with the original "when we
> close one, make sure the changes hit the disk platter" approach.  So
> I am not sure what conclusion we should draw from such an experiment,
> other than "ok, it compiles cleanly."  After all, unless we cause
> system crashes, what we thought we have written and close(2) would
> be seen by another process that we spawn after that, with or without
> sync, no?

Basically yes.  XFS on Linux has shutdown ioctls that allow to simulate
that crash by shutting the file system down which really helps debugging
that kind of code.  A bunch of other file systems (ext4, f2fs) have
also picked this up now (grep for {XFS,EXT4,F2FS}_IOC_SHUTDOWN).