linux-kernel - Re: [PATCH] Update atime from future.

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Date:	Mon, 03 Jan 2011 10:27:48 +0000
From:	Steven Whitehouse <swhiteho@...hat.com>
To:	yangsheng <sickamd@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org
Subject: Re: [PATCH] Update atime from future.

Hi,

On Wed, 2010-12-29 at 21:58 +0800, yangsheng wrote:
> Signed-off-by: sickamd@...il.com
> ---
>  fs/inode.c |    8 +++++++-
>  1 files changed, 7 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/inode.c b/fs/inode.c
> index da85e56..6c8effd 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -1469,7 +1469,13 @@ static int relatime_need_update(struct vfsmount *mnt, struct inode *inode,
>  		return 1;
>  
>  	/*
> -	 * Is the previous atime value older than a day? If yes,
> +	 * Is the previous atime value in future? If yes,
> +	 * update atime:
> +	 */
> +	if ((long)(now.tv_sec - inode->i_atime.tv_sec) < 0)
> +		return 1;
> +	/*
> +	 * Is the previous atime value old than a day? If yes,
>  	 * update atime:
>  	 */
>  	if ((long)(now.tv_sec - inode->i_atime.tv_sec) >= 24*60*60)

I don't think this is a good plan for cluster filesystems, since if the
times on the nodes are not exactly synchronised (we do highly recommend
people run ntp or similar) then this might lead to excessive atime
updating. The current behaviour is to ignore atimes which are in the
future for exactly this reason,

Steve.


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