Re: [PATCH] Update atime from future.

[YangSheng]

On 01/03/2011 06:27 PM, Steven Whitehouse wrote:
> Hi,
>
> On Wed, 2010-12-29 at 21:58 +0800, yangsheng wrote:
>    
> > Signed-off-by: sickamd@xxxxxxxxx
> > ---
> >   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,
>    
I agreed in theory.  Anyway, a two-way update may cause shake in some 
case. Like a cluster environment with time gap between cluster members. 
But future atime also is a trouble things i think. Of course, I hope a 
clever patch to fix them all.

Thanks
yangsheng
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