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Date: Wed, 14 Dec 2005 17:00:53 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: Error reported dd'ing close of end of block device with skip
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On Dec 13 19:05, Loh, Joe wrote:
> We downloaded cygwin-inst-20051213.tar.bz2 and implemented the solution
> recommended below.  So far, our cursory testing indicates that we are
> able to do unbuffered read.  However, we are not seeing any "bug" that
> was referenced here.  What is the "bug" that is being referenced here?

The RDIOCDOP/RDSETBLK was incorrectly implemented when a request was
made to set the buffer size to 0 or 1 (aka "non-buffered").  But since
that's fixed in the above snapshot, you can't trip over it.

Btw., I just applied a patch which implements O_DIRECT, which will be
available in the next snapshot.  The same restriction as on Linux
applies, which is, the buffers used in read/write operations must be
sector-aligned.  Note that using O_DIRECT requires to rebuild the
application, so you'll be unable to experiment with this using the
current versions of dd(1).


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat, Inc.

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