From: Dave Chinner <david@fromorbit.com>
To: Amir Goldstein <amir73il@gmail.com>
Cc: fdmanana@kernel.org, fstests <fstests@vger.kernel.org>,
Linux Btrfs <linux-btrfs@vger.kernel.org>,
Filipe Manana <fdmanana@suse.com>
Subject: Re: [PATCH] generic: add test for fsync after shrinking truncate and rename
Date: Tue, 5 Mar 2019 12:00:31 +1100 [thread overview]
Message-ID: <20190305010031.GB26298@dastard> (raw)
In-Reply-To: <20190305005020.GA26298@dastard>
On Tue, Mar 05, 2019 at 11:50:20AM +1100, Dave Chinner wrote:
> On Mon, Mar 04, 2019 at 05:04:23PM +0200, Amir Goldstein wrote:
> > On Mon, Mar 4, 2019 at 4:44 PM <fdmanana@kernel.org> wrote:
> > >
> > > From: Filipe Manana <fdmanana@suse.com>
> > >
> > > Test that if we truncate a file to reduce its size, rename it and then
> > > fsync it, after a power failure the file has a correct size and name.
> > >
> >
> > I am not sure that ext4/xfs semantics guaranty anything about
> > persisting file name after fsync of file?...
>
> They do. It's that pesky "strictly ordered metadata" thing I keep
> having to explain to people...
https://marc.info/?l=fstests&m=155010885626284&w=2
-Dave.
>
> i.e. if you fsync an inode, then you are persisting all the changes
> needed to reference that file and it's data. And so if there was a
> rename in the history of that file, then that is persisted, too.
> Which means that both the original and the new directory
> modifications are persisted, too.
>
> *POSIX* doesn't require this - it says that if you O_DSYNC data,
> then it also includes all the metadata needed to reference that
> data. So even if the data is there, POSIX doesn't define whether the
> rename is there or noti, just that you can get to the fsync'd data
> via either the old or new name. IOWs, POSIX allows the behaviour to
> be implementation specific.
>
> In this case, file systems with strictly ordered metadata will end
> up making the rename visible because the rename occurred before the
> truncate that the fsync() is persisting...
>
> Cheers,
>
> Dave.
> --
> Dave Chinner
> david@fromorbit.com
>
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2019-03-05 1:00 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-04 14:06 [PATCH] generic: add test for fsync after shrinking truncate and rename fdmanana
2019-03-04 15:04 ` Amir Goldstein
2019-03-04 15:23 ` Filipe Manana
2019-03-04 17:59 ` Amir Goldstein
2019-03-04 22:30 ` Filipe Manana
2019-03-05 5:59 ` Amir Goldstein
2019-03-05 9:26 ` Filipe Manana
2019-03-05 10:51 ` Amir Goldstein
2019-03-05 0:50 ` Dave Chinner
2019-03-05 1:00 ` Dave Chinner [this message]
2019-03-05 1:08 ` Vijay Chidambaram
2019-03-05 5:39 ` Amir Goldstein
2019-03-05 22:33 ` Dave Chinner
2019-03-06 7:51 ` Amir Goldstein
2019-03-06 21:48 ` Dave Chinner
2019-03-07 7:52 ` Amir Goldstein
2019-03-07 23:19 ` Jayashree Mohan
2019-03-08 4:35 ` Dave Chinner
2019-03-08 15:11 ` Vijay Chidambaram
2019-03-19 1:13 ` Dave Chinner
2019-03-08 3:46 ` Dave Chinner
2019-03-05 9:26 ` [PATCH v2] " fdmanana
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