From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marco Stornelli <marco.stornelli@gmail.com>
Subject: Re: [PATCH 00/14] Pramfs: Persistent and protected ram filesystem
Date: Thu, 25 Jun 2009 08:32:08 +0200
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To: Jamie Lokier <jamie@shareable.org>
Cc: Pavel Machek <pavel@ucw.cz>, Tim Bird <tim.bird@am.sony.com>, Linux Embedded <linux-embedded@vger.kernel.org>, Linux Kernel <linux-kernel@vger.kernel.org>, Linux FS Devel <linux-fsdevel@vger.kernel.org>, Daniel Walker <dwalker@soe.ucsc.edu>

2009/6/24 Jamie Lokier <jamie@shareable.org>:
> Pavel Machek wrote:
>> On Tue 2009-06-23 20:07:23, Marco wrote:
>> > You are talked about journaling. This schema works well for a disk=
, but
>> > what about a piece of ram? What about a crazy kernel that write in=
 that
>> > area for a bug? Do you remember for example the e1000e bug? It's n=
ot
>>
>> I believe you need both journaling *and* write protection. How do yo=
u
>> handle power fault while writing data?
>
> I think this is basically right.
>
> write protection for the crazy kernels, and journalling for
> powerfail/crash during updates.
>
> Journalling can be extremely simple. =A0It can be just one memory blo=
ck
> at a fixed location, double-buffering all writes.
>
> Pramfs already has checksums, which makes that easier. =A0You just wr=
ite
> to the buffer area first, with checksum, then write to the final area=
=2E
> Mount looks at the buffer area, and if the checksum is fine, copies
> the contents to the destination block.
>
> That's all it takes to be resistant against power failures and crashe=
s
> during writes. =A0Probably <100 lines of code.
>
> -- Jamie
>

It seems a reasonable request.

Marco
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