linux-kernel - Re: [PATCH 3/6] ext2 balloc: fix off-by-one against rsv

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Message-Id: <1164742936.3769.42.camel@dyn9047017103.beaverton.ibm.com>
Date:	Tue, 28 Nov 2006 11:42:16 -0800
From:	Mingming Cao <cmm@...ibm.com>
To:	Hugh Dickins <hugh@...itas.com>
Cc:	Andrew Morton <akpm@...l.org>, Mel Gorman <mel@...net.ie>,
	"Martin J. Bligh" <mbligh@...igh.org>,
	linux-kernel@...r.kernel.org,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 3/6] ext2 balloc: fix off-by-one against rsv_end

On Tue, 2006-11-28 at 17:41 +0000, Hugh Dickins wrote:
> rsv_end is the last block within the reservation,
> so alloc_new_reservation should accept start_block == rsv_end as success.
> 
> Signed-off-by: Hugh Dickins <hugh@...itas.com>
> ---
> 

Thanks, Acked.

This is not a problem for now, as the default window size is 8 blocks,
and we never shrink the window size.  But it could be a issue in the
future, if the reservation window could be dynamically shrink, when it
keep failing to create a new(large) reservation window, or we keep throw
away a just-allocated-window as the application is doing very seeky
random write.


>  fs/ext2/balloc.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- 2.6.19-rc6-mm2/fs/ext2/balloc.c	2006-11-24 08:18:02.000000000 +0000
> +++ linux/fs/ext2/balloc.c	2006-11-27 19:28:41.000000000 +0000
> @@ -950,7 +950,7 @@ retry:
>  	 * check if the first free block is within the
>  	 * free space we just reserved
>  	 */
> -	if (start_block >= my_rsv->rsv_start && start_block < my_rsv->rsv_end)
> +	if (start_block >= my_rsv->rsv_start && start_block <= my_rsv->rsv_end)
>  		return 0;		/* success */
>  	/*
>  	 * if the first free bit we found is out of the reservable space

-
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