Why is relatime immune to remount?

[Kevin Fenzi]

On Mon, 07 Jul 2008 11:12:18 +0200
mail at robertoragusa.it (Roberto Ragusa) wrote:

> Hi,
> 
> my root filesystem is mounted with the option relatime for
> some reason (I just have defaults in /etc/fstab).
> 
> Any attempt to temporarily disable the option fails,
> even with norelatime, which appears to be a valid option.
> Is this expected or a bug?
> 
> (fedora 9 with 2.6.25.3-18)
> 
> [root at thinkpad ~]# cat /proc/mounts |grep /dev/root
> /dev/root / reiserfs rw,relatime 0 0
> [root at thinkpad ~]# mount / -o remount,norelatime
> [root at thinkpad ~]# cat /proc/mounts |grep /dev/root
> /dev/root / reiserfs rw,relatime 0 0
> [root at thinkpad ~]# mount / -o remount,atime
> [root at thinkpad ~]# cat /proc/mounts |grep /dev/root
> /dev/root / reiserfs rw,relatime 0 0
> [root at thinkpad ~]# mount / -o remount,noatime
> [root at thinkpad ~]# cat /proc/mounts |grep /dev/root
> /dev/root / reiserfs rw,noatime,relatime 0 0
> [root at thinkpad ~]# mount / -o remount,atime
> [root at thinkpad ~]# cat /proc/mounts |grep /dev/root
> /dev/root / reiserfs rw,relatime 0 0
> [root at thinkpad ~]# mount / -o remount,nonononononorelatime
> mount: / not mounted already, or bad option
> 

Yeah, confusingly that doesn't work. 

You have to: 

echo 0 > /proc/sys/fs/default_relatime

and then mount/remount with 'atime' and it should work. 

Even the patch in the kernel src.rpm has incorrect docs on it. 

kevin
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