Re: [PATCH] Update atime from future.

From: Zach Brown <zab@zabbo.net>
To: yangsheng <sickamd@gmail.com>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	adilger@dilger.ca
Subject: Re: [PATCH] Update atime from future.
Date: Tue, 4 Dec 2012 11:41:06 -0800	[thread overview]
Message-ID: <20121204194106.GA2200@lenny.home.zabbo.net> (raw)
In-Reply-To: <1354557399-6202-1-git-send-email-sickamd@gmail.com>

On Tue, Dec 04, 2012 at 01:56:39AM +0800, yangsheng wrote:
> Relatime should update the inode atime if it is more than a day in the
> future.  The original problem seen was a tarball that had a bad atime,
> but could also happen if someone fat-fingers a "touch".  The future
> atime will never be fixed.  Before the relatime patch, the future atime
> would be updated back to the current time on the next access.

I guess.

>  	/*
> +	 * Is the previous atime value in future? If yes,
> +	 * update atime:
> +	 */
> +	if ((long)(now.tv_sec - inode->i_atime.tv_sec) < -RELATIME_MARGIN)
> +		return 1;

But this is confusing to read.  "If atime is less than a negative day in
the past.. wait, what?"

It seems like we should combine the two RELATIME_MARGIN tests.

	/*
	 * Update atime if it's older than a day or more than a day
	 * in the future, which we assume is corrupt.
	 */
	if (abs(inode->i_atime.tv_sec - now.tv_sec)) >= RELATIME_MARGIN)
		return 1;

(I don't know if you'd still need the (long) cast in there, given the
type tests in abs()).

- z