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Date: Thu, 9 Apr 2009 19:07:24 +0100
From: Jamie Lokier <jamie@shareable.org>
To: Doug Graham <dgraham@nortel.com>
Subject: Re: mtdblock caching and syncing
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Cc: Josh Boyer <jwboyer@gmail.com>, linux-mtd@lists.infradead.org
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Doug Graham wrote:
> > The device in question isn't the flash.  It's the mtdblock device.  So
> > fsync semantics are preserved.  This is the same as writing to a file
> > on a hard drive, calling fsync, and having it sit in the hard drive's
> > cache.
> 
> That's a good point, and one I've wondered about before.  I don't know
> much about how hard drives manage their cache, but I would assume that
> they don't leave dirty data in their cache for an unbounded period
> of time.  I'd guess that data is written to the actual disk within a
> few 10s of milliseconds after being sent to the device.

Ideally, fsync() should flush data from a hard drive's cache too.

-- Jamie