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From: Matthew Wilcox <matthew@wil.cx>
Subject: Re: Read/write counts
Date: Mon, 4 Jun 2007 11:02:23 -0600
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Cc: Andreas Dilger <adilger@clusterfs.com>,
	"David H. Lynch Jr." <dhlii@comcast.net>,
	linux-fsdevel@vger.kernel.org
To: Bryan Henderson <hbryan@us.ibm.com>
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On Mon, Jun 04, 2007 at 09:56:07AM -0700, Bryan Henderson wrote:
> Programs that assume a full transfer are fairly common, but are 
> universally regarded as either broken or just lazy, and when it does cause 
> a problem, it is far more common to fix the application than the kernel.

Linus has explicitly forbidden short reads from being returned.  The
original poster may get away with it for a specialised case, but for
example, signals may not cause a return to userspace with a short read
for exactly this reason.