linux-ext4 - Re: [PATCH] vfs: freeze filesystems just prior to reboot

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Message-ID: <20170805154528.GI24087@magnolia>
Date:   Sat, 5 Aug 2017 08:45:28 -0700
From:   "Darrick J. Wong" <darrick.wong@...cle.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Colin Walters <walters@...bum.org>,
        xfs <linux-xfs@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] vfs: freeze filesystems just prior to reboot

On Sat, Aug 05, 2017 at 07:16:21AM -0700, Christoph Hellwig wrote:
> > Any objections to something like an ioctl (fd, FIFREEZETHAW, 0) ?
> 
> It's going to be completely trivial, which argues for it.  The only
> points left woul be bikeshedding over the name, and how to describe
> its semantics.

FSCHECKPOINT?  Since that's your requirement anyway...

"Ensures that all filesystem metadata (which may be in a journal
somewhere) has been checkpointed back to disk." ?

--D

> > in the end probably the real fix is probably something like storing
> > multiple copies of the bootloader config with checksums that grub
> > can verify.  Basically teach grub to try really hard to extract known-good
> > data from the FS.  For file-level consistency that'd be pretty easy,
> > we could have e.g. 
> 
> The real answer is to have a filesystem that does the above for you
> for the boot partition, e.g. one where the kernel and grub have
> a common consistency protocol for.
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