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Message-ID: <4A36881E.8010009@gmail.com>
Date: Mon, 15 Jun 2009 19:42:54 +0200
From: Marco <marco.stornelli@...il.com>
To: Bryan Henderson <hbryan@...ibm.com>
CC: Artem Bityutskiy <dedekind1@...il.com>,
Daniel Walker <dwalker@....ucsc.edu>,
Jamie Lokier <jamie@...reable.org>,
Linux Embedded <linux-embedded@...r.kernel.org>,
Linux FS Devel <linux-fsdevel@...r.kernel.org>,
Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 00/14] Pramfs: Persistent and protected ram filesystem
Bryan Henderson wrote:
>> Marco wrote:
>>> To enable direct
>>> I/O at all times for all regular files requires either that
>>> applications be modified to include the O_DIRECT flag on all file
>>> opens, or that a new filesystem be used that always performs direct
>>> I/O by default."
>> This could be done as well by just introducing a "direct_io_only"
>> mount option to a file-system which would need this feature.
>
> But it's possible that there's just no advantage to having a block device
> in the stack here. When unix block devices were invented, their main
> purpose was that they could reorder reads and writes and do buffering and
> caching -- all things essential for disk drives. We don't want to stretch
> the concept too far.
>
Yes I agree, we can't in this case talk about read and write reordering,
buffering and caching because we're talking about something completely
different from a classic disk. The issues of this kind of fs are more
similar to the tmpfs issues.
Marco
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