linux-kernel - Re: [PATCH 6/19] UML

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Message-ID: <alpine.LFD.1.00.0804291604380.2548@localhost.localdomain>
Date:	Tue, 29 Apr 2008 16:04:56 +0800 (CST)
From:	WANG Cong <xiyou.wangcong@...il.com>
To:	Jeff Dike <jdike@...toit.com>
cc:	WANG Cong <xiyou.wangcong@...il.com>, akpm@...l.org,
	linux-kernel@...r.kernel.org,
	user-mode-linux-devel@...ts.sourceforge.net
Subject: Re: [PATCH 6/19] UML - hppfs fixes

On Mon, 28 Apr 2008, Jeff Dike wrote:

> On Sat, Apr 26, 2008 at 04:31:32PM +0800, WANG Cong wrote:
>> > +		rem = copy_to_user(buf, &data->contents[off], count);
>> > +		*ppos += count - rem;
>> > +		if (rem > 0)
>> > +			return -EFAULT;
>> 
>> Could you please explain why check 'rem' after using it here?
>
> Actually, this isn't as wrong as it looks. copy_to_user returns what
> hasn't been copied (rem == remaining).  So, I think the mistake is to
> return -EFAULT here.  Returning the short count would be right, unless
> rem == count, in which case we return -EFAULT.

Yes, thanks.

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