Re: ext4 lazytime: ctime of some files changed

[Theodore Ts'o <tytso@mit.edu>]

On Wed, May 13, 2015 at 11:35:31AM +0200, Jörg-Volker Peetz wrote:
> 
> on my laptop with ext4 fs (on SSD) I started to try the lazytime mount option
> using a self compiled kernel 4.0.2 on a debian system with mount version 2.26.2.
> Before that, I've used the noatime mount option.
> 
> After restarting the system with an adapted /etc/fstab file and the kernel
> parameter "rootflags=lazytime", the relatime mount option was also set. I
> changed that by commanding "mount -o remount,strictatime /", etc.

The lazytime flag is independent of strictatime/relatime/noatime.  And
the default is relatime.  So when you replaced noatime with lazytime,
it's not surprising that you saw the relatime mount option being set.

> By accident, I noticed that some files had a modified ctime and mtime although
> they were not changed or modified.
> 
> Has anybody else experienced that? Do I miss a patch?

I haven't seen this myself.

> Mount options in fstab: nobarrier,lazytime,errors=remount-ro
> The filesystems are ext4 on a primary partition of the SSD with default mount
> option journal_data_writeback. I created them in Feb 2011.
> 
> By the way, the command "mount -o remount,lazytime /" does not do the switch to
> lazytime.


# grep sda3 /proc/mounts
/dev/sda3 / ext4 rw,relatime,errors=remount-ro,data=ordered 0 0
# mount -o remount,lazytime /
# grep sda3 /proc/mounts
/dev/sda3 / ext4 rw,lazytime,relatime,errors=remount-ro,data=ordered 0 0
# uname -a
Linux closure 4.1.0-rc2-11633-gef8a5d0 #125 SMP Tue May 5 21:21:08 EDT 2015 x86_64 GNU/Linux

      	      			       	    	- Ted
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