linux-kernel - How does ext2 implement sparse files?

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Message-ID: <20080131152823.GA29422@lars.home.noschinski.de>
Date:	Thu, 31 Jan 2008 16:28:23 +0100
From:	Lars Noschinski <lklml@...noschinski.de>
To:	linux-kernel@...r.kernel.org
Subject: How does ext2 implement sparse files?

Hello!

For an university project, we had to write a toy filesystem (ext2-like),
for which I would like to implement sparse file support. For this, I
digged through the ext2 source code; but I could not find the point,
where ext2 detects holes.

As far as I can see from fs/buffer.c, an hole is a buffer_head which is
not mapped, but uptodate. But I cannot find a relevant source line,
where ext2 makes usage of this information.

Any hints would be greatly appreciated,
     Lars.

[Please CC me on answers, I'm not subscribed]
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