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From: Theodore Tso <tytso@mit.edu>
To: Bill Davidsen <davidsen@tmr.com>
Cc: roel kluin <roel.kluin@gmail.com>,
	adilger@sun.com, linux-ext4@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] ext3, ext4: do_split() fix loop, with obvious unsigned wrap
Date: Tue, 2 Dec 2008 16:57:58 -0500	[thread overview]
Message-ID: <20081202215758.GE20858@mit.edu> (raw)
In-Reply-To: <49356B96.7070900@tmr.com>

On Tue, Dec 02, 2008 at 12:08:38PM -0500, Bill Davidsen wrote:
> Sorry, you are reading it wrong, the i values inside the loop are  
> identical to those in the original. The value of i starts at count, and  
> the test comes *before* the value is used inside the loop. The values of  
> i inside the loop start at count-1 and go to zero, just as it did in the  
> original. That's why the "i--" is there, the test is on the  
> unincremented value range count to one, but the value inside the loop is  
> correct (or at least is the same as the original patch).

You're right; my bad.  But with something like this:

>>> +	for (i = count; i--; ) {

...where there is no third part of the for loop, and a decrement in
the second part of the loop, just for clarity's sake, it's much better
to write it as a while loop.

						- Ted

  parent reply	other threads:[~2008-12-02 21:58 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-12-01 19:28 [PATCH v2] ext3, ext4: do_split() fix loop, with obvious unsigned wrap roel kluin
2008-12-02 13:24 ` Theodore Tso
2008-12-02 17:08   ` Bill Davidsen
2008-12-02 19:47     ` Roel Kluin
2008-12-02 21:57     ` Theodore Tso [this message]
2008-12-02 23:17       ` Bill Davidsen
2008-12-03 14:25         ` Bill Davidsen
2008-12-03  6:05 ` Andrew Morton
2008-12-03 14:32   ` Bill Davidsen

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