linux-ext4 - Re: Atomic file data replace API

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Date:	Tue, 28 Dec 2010 23:58:21 +0100
From:	Olaf van der Spek <olafvdspek@...il.com>
To:	Ric Wheeler <rwheeler@...hat.com>
Cc:	"Ted Ts'o" <tytso@....edu>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-ext4@...r.kernel.org
Subject: Re: Atomic file data replace API

On Tue, Dec 28, 2010 at 11:36 PM, Ric Wheeler <rwheeler@...hat.com> wrote:
> I think that various developers have answered this for you several times.

Not really, unfortunately. Haven't seen a single link to code that
shows how to do it properly.
Temp file, fsync, rename is often mentioned but that skips the
preserving meta-data part and this part, which you also skipped:
One use case would be updating a file in a safe way when you have
write access to that file but not to anything else.

> As a suggestion, if you are not a kernel developer, show us specifically a
> bit of application code that demonstrates something that you want to have
> work differently.

I will.

> Test it with power failure (buy an external e-sata or USB disk and pull
> power while running your app).

The current code?
I think I'll use a VM instead of an external disk. ;)

Olaf
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