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From: Cesar Eduardo Barros <cesarb@cesarb.net>
To: Wu Fengguang <fengguang.wu@intel.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] radix-tree: fix radix_tree_prev_hole underflow case
Date: Thu, 13 May 2010 23:28:50 -0300	[thread overview]
Message-ID: <4BECB562.2080200@cesarb.net> (raw)
In-Reply-To: <20100514021508.GA7810@localhost>

Em 13-05-2010 23:15, Wu Fengguang escreveu:
> On Fri, May 14, 2010 at 10:05:24AM +0800, Cesar Eduardo Barros wrote:
>> radix_tree_prev_hole() used LONG_MAX to detect underflow; however,
>> ULONG_MAX is clearly what was intended, both here and by its only user
>> (count_history_pages at mm/readahead.c).
>
> Good catch, thanks! I actually have a more smart
> radix_tree_prev_hole() that uses ULONG_MAX.

I saw it already ([PATCH 14/16] radixtree: speed up the search for 
hole), but it misses the LONG_MAX in the documentation comment.

> Andrew, fortunately this bug has little impact on readahead.

I agree, if I read it correctly it should only have any impact either 
when very near LONG_MAX or in the unlikely case that there is no hole at 
ULONG_MAX. And even then, the impact should be limited.

-- 
Cesar Eduardo Barros
cesarb@cesarb.net
cesar.barros@gmail.com

WARNING: multiple messages have this Message-ID (diff)
From: Cesar Eduardo Barros <cesarb@cesarb.net>
To: Wu Fengguang <fengguang.wu@intel.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] radix-tree: fix radix_tree_prev_hole underflow case
Date: Thu, 13 May 2010 23:28:50 -0300	[thread overview]
Message-ID: <4BECB562.2080200@cesarb.net> (raw)
In-Reply-To: <20100514021508.GA7810@localhost>

Em 13-05-2010 23:15, Wu Fengguang escreveu:
> On Fri, May 14, 2010 at 10:05:24AM +0800, Cesar Eduardo Barros wrote:
>> radix_tree_prev_hole() used LONG_MAX to detect underflow; however,
>> ULONG_MAX is clearly what was intended, both here and by its only user
>> (count_history_pages at mm/readahead.c).
>
> Good catch, thanks! I actually have a more smart
> radix_tree_prev_hole() that uses ULONG_MAX.

I saw it already ([PATCH 14/16] radixtree: speed up the search for 
hole), but it misses the LONG_MAX in the documentation comment.

> Andrew, fortunately this bug has little impact on readahead.

I agree, if I read it correctly it should only have any impact either 
when very near LONG_MAX or in the unlikely case that there is no hole at 
ULONG_MAX. And even then, the impact should be limited.

-- 
Cesar Eduardo Barros
cesarb@cesarb.net
cesar.barros@gmail.com

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  reply	other threads:[~2010-05-14  2:28 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-05-14  2:05 [PATCH] radix-tree: fix radix_tree_prev_hole underflow case Cesar Eduardo Barros
2010-05-14  2:05 ` Cesar Eduardo Barros
2010-05-14  2:15 ` Wu Fengguang
2010-05-14  2:15   ` Wu Fengguang
2010-05-14  2:28   ` Cesar Eduardo Barros [this message]
2010-05-14  2:28     ` Cesar Eduardo Barros
2010-05-14  2:37     ` Wu Fengguang
2010-05-14  2:37       ` Wu Fengguang

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