linux-kernel - Re: [PATCH 1/3] ocfs2: When zero extending, do it by page.

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Date:	Thu, 8 Jul 2010 02:51:56 -0700
From:	Joel Becker <Joel.Becker@...cle.com>
To:	Tao Ma <tao.ma@...cle.com>
Cc:	Dave Chinner <david@...morbit.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	ocfs2-devel@....oracle.com, Dave Chinner <dchinner@...hat.com>,
	Christoph Hellwig <hch@....de>, Mark Fasheh <mfasheh@...e.com>
Subject: Re: [PATCH 1/3] ocfs2: When zero extending, do it by page.

On Thu, Jul 08, 2010 at 11:44:59AM +0800, Tao Ma wrote:
> On 07/07/2010 07:16 PM, Joel Becker wrote:
> >+	BUG_ON(abs_to>  ((index + 1)<<  PAGE_CACHE_SHIFT));
> Sorry for not noticing this yesterday night. This can't work and
> will overflow and bug out. I met with a similar bug in reflink test.
> See commit d622b89.

	Good catch.  It's obvious, now that you mention it.

> >+	/* We know that zero_from is block aligned */
> >+	for (block_start = zero_from;
> >+	     (block_start<  PAGE_CACHE_SIZE)&&  (block_start<  zero_to);
> >+	     block_start = block_end) {
> Do we really need to check block_start < PAGE_CACHE_SIZE? I think
> just check block_start < zero_to is enough since you have limit
> zero_to with PAGE_CACHE_SIZE. What's more, it looks more natural(see
> below), does it?
> 
> 	for (block_start = zero_form; block_start < zero_to; block_start =
> block_end) {

	Yup.  The code looked different halfway through, so I didn't
realize I was checking the same thing twice.

Joel

-- 

"Depend on the rabbit's foot if you will, but remember, it didn't
 help the rabbit."
	- R. E. Shay

Joel Becker
Consulting Software Developer
Oracle
E-mail: joel.becker@...cle.com
Phone: (650) 506-8127
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