From: Dave Chinner <david@fromorbit.com>
To: 焦晓冬 <milestonejxd@gmail.com>
Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
adilger.kernel@dilger.ca, linux-kernel@vger.kernel.org
Subject: Re: metadata operation reordering regards to crash
Date: Sat, 15 Sep 2018 08:23:36 +1000 [thread overview]
Message-ID: <20180914222336.GD16550@dastard> (raw)
In-Reply-To: <CAJDTihzzLV3qwg0tGH_D4xAjCrgMy+oc4H9snpnMC_RC2q7nyw@mail.gmail.com>
On Fri, Sep 14, 2018 at 05:06:44PM +0800, 焦晓冬 wrote:
> Hi, all,
>
> A probably bit of complex question:
> Does nowadays practical filesystems, eg., extX, btfs, preserve metadata
> operation order through a crash/power failure?
Yes.
Behaviour is filesystem dependent, but we have tests in fstests that
specifically exercise order preservation across filesystem failures.
> What I know is modern filesystems ensure metadata consistency
> after crash/power failure. Journal filesystems like extX do that by
> write-ahead logging of metadata operations into transactions. Other
> filesystems do that in various ways as btfs do that by COW.
>
> What I'm not so far clear is whether these filesystems preserve
> metadata operation order after a crash.
>
> For example,
> op 1. rename(A, B)
> op 2. rename(C, D)
>
> As mentioned above, metadata consistency is ensured after a crash.
> Thus, B is either the original B(or not exists) or has been replaced by A.
> The same to D.
>
> Is it possible that, after a crash, D has been replaced by C but B is still
> the original file(or not exists)?
Not for XFS, ext4, btrfs or f2fs. Other filesystems might be
different.
Cheers,
Dave,
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2018-09-14 22:23 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-14 9:06 metadata operation reordering regards to crash 焦晓冬
2018-09-14 22:23 ` Dave Chinner [this message]
2018-09-15 6:58 ` 焦晓冬
2018-09-15 18:04 ` Andreas Dilger
2018-09-16 1:18 ` Qu Wenruo
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