ext4 lazytime: ctime of some files changed

ext4 lazytime: ctime of some files changed

[Jörg-Volker Peetz]

Dear Ted,

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.
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?

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.

And thanks for your tireless work on Linux.
-- 
Regards,
jvp.

Re: ext4 lazytime: ctime of some files changed

[Jörg-Volker Peetz]

Jörg-Volker Peetz wrote on 05/13/2015 11:35:
> Dear Ted,
> 
> 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.
> 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?
> 
> 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.
> 
> And thanks for your tireless work on Linux.
> 

After writing the above, I encountered another accident regarding two files of
the emacs24 package of which the mtime got changed.

I tried to repair this by using versions of the two files with the correct mtime
in the /tmp directory and commanded

> touch -r /tmp/debian-ispell.elc
/usr/share/emacs24/site-lisp/dictionaries-common/debian-ispell.elc
> touch -r /tmp/ess-noweb-font-lock-mode.elc
/usr/share/emacs24/site-lisp/ess/ess-noweb-font-lock-mode.elc

A few hours later I unpacked and tested a tar archive by commanding s.t. like

> tar xf linux-4.0.tar.xz
> sync
> echo 3 >/proc/sys/vm/drop_caches
> tar df linux-4.0.tar.xz

Thereafter, the two emacs package files again had a wrong mtime (which by the
way shows when I start emacs).

Could this be due to the lazytime mount option?
-- 
Regards,
jvp.


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Re: ext4 lazytime: ctime of some files changed

[Theodore Ts'o]

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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Re: ext4 lazytime: ctime of some files changed

[Jörg-Volker Peetz]

Theodore Ts'o wrote on 05/14/2015 04:17:
> On Wed, May 13, 2015 at 11:35:31AM +0200, Jörg-Volker Peetz wrote:
>>
>> 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

# uname -a
Linux fehu 4.0.2 #1 SMP Thu May 7 00:09:53 CEST 2015 x86_64 GNU/Linux
# grep sda2 /proc/mounts
/dev/sda2 /home ext4 rw,noatime,nobarrier,errors=remount-ro 0 0
# mount -o remount,lazytime /home
# grep sda2 /proc/mounts
/dev/sda2 /home ext4 rw,noatime,nobarrier,errors=remount-ro 0 0
# mount --version
mount from util-linux 2.26.2 (libmount 2.26.0: selinux, assert, debug)

Also switching to relatime does not work with the mount command. Could it be a
problem with the mount package of debian?
-- 
Regards,
jvp.


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Re: ext4 lazytime: ctime of some files changed

[Jörg-Volker Peetz]

[forgot to Cc to you]
Theodore Ts'o wrote on 05/14/2015 04:17:
> On Wed, May 13, 2015 at 11:35:31AM +0200, Jörg-Volker Peetz wrote:
>>
>> 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

# uname -a
Linux fehu 4.0.2 #1 SMP Thu May 7 00:09:53 CEST 2015 x86_64 GNU/Linux
# grep sda2 /proc/mounts
/dev/sda2 /home ext4 rw,noatime,nobarrier,errors=remount-ro 0 0
# mount -o remount,lazytime /home
# grep sda2 /proc/mounts
/dev/sda2 /home ext4 rw,noatime,nobarrier,errors=remount-ro 0 0
# mount --version
mount from util-linux 2.26.2 (libmount 2.26.0: selinux, assert, debug)

Also switching to relatime does not work with the mount command. Could it be a
problem with the mount package of debian?
-- 
Regards,
jvp.


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Re: ext4 lazytime: ctime of some files changed

[Theodore Ts'o]

On Thu, May 14, 2015 at 10:27:58AM +0200, Jörg-Volker Peetz wrote:
> 
> Also switching to relatime does not work with the mount command. Could it be a
> problem with the mount package of debian?

I'm using Debian Jessie:

ii  mount                2.25.2-6        amd64           Tools for mounting and manipulating filesystem

The other difference might be what you and I have in our /etc/fstab?
I have:

LABEL=closure-root	/               ext4    errors=remount-ro 0       1

Can you also try something like this?

# strace -o /tmp/st mount -o remount,nolazytime /
# grep ^mount /tmp/st
mount("/dev/sda3", "/", 0x1f21250, MS_MGC_VAL|MS_REMOUNT, "errors=remount-ro,lazytime") = 0

Cheers,

						- Ted
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Re: ext4 lazytime: ctime of some files changed

[Jörg-Volker Peetz]

Theodore Ts'o wrote on 05/14/2015 14:38:
> On Thu, May 14, 2015 at 10:27:58AM +0200, Jörg-Volker Peetz wrote:
>>
>> Also switching to relatime does not work with the mount command. Could it be a
>> problem with the mount package of debian?
> 
> I'm using Debian Jessie:
> 
I'm using a mixture of testing and sid with mount, util-linux, etc. version
2.26.2-2.

> ii  mount                2.25.2-6        amd64           Tools for mounting and manipulating filesystem
> 
> The other difference might be what you and I have in our /etc/fstab?
> I have:
> 
> LABEL=closure-root	/               ext4    errors=remount-ro 0       1
> 
Here:
  UUID=7e13aca5-...   /  ext4  nobarrier,noatime,errors=remount-ro  0  2

> Can you also try something like this?
> 
> # strace -o /tmp/st mount -o remount,nolazytime /
> # grep ^mount /tmp/st
> mount("/dev/sda3", "/", 0x1f21250, MS_MGC_VAL|MS_REMOUNT, "errors=remount-ro,lazytime") = 0
> 
mount("/dev/sda1", "/", 0x1488780, MS_MGC_VAL|MS_REMOUNT|MS_NOATIME,
"nobarrier,errors=remount-ro") = 0

> Cheers,
> 
> 						- Ted
Thank you for your support.
-- 
Jörg.



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Re: ext4 lazytime: ctime of some files changed

[Jörg-Volker Peetz]

Jörg-Volker Peetz wrote on 05/14/2015 14:58:
> Theodore Ts'o wrote on 05/14/2015 14:38:
>> On Thu, May 14, 2015 at 10:27:58AM +0200, Jörg-Volker Peetz wrote:
>>>
>>> Also switching to relatime does not work with the mount command. Could it be a
>>> problem with the mount package of debian?
>>
>> I'm using Debian Jessie:
>>
> I'm using a mixture of testing and sid with mount, util-linux, etc. version
> 2.26.2-2.
> 
>> ii  mount                2.25.2-6        amd64           Tools for mounting and manipulating filesystem
>>
>> The other difference might be what you and I have in our /etc/fstab?
>> I have:
>>
>> LABEL=closure-root	/               ext4    errors=remount-ro 0       1
>>
> Here:
>   UUID=7e13aca5-...   /  ext4  nobarrier,noatime,errors=remount-ro  0  2
> 
Typo here, is actually
  UUID=7e13aca5-...   /  ext4  nobarrier,noatime,errors=remount-ro  0  1

>> Can you also try something like this?
>>
>> # strace -o /tmp/st mount -o remount,nolazytime /
>> # grep ^mount /tmp/st
>> mount("/dev/sda3", "/", 0x1f21250, MS_MGC_VAL|MS_REMOUNT, "errors=remount-ro,lazytime") = 0
>>
> mount("/dev/sda1", "/", 0x1488780, MS_MGC_VAL|MS_REMOUNT|MS_NOATIME,
> "nobarrier,errors=remount-ro") = 0
> 
>> Cheers,
>>
>> 						- Ted
> Thank you for your support.
> 


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Re: ext4 lazytime: ctime of some files changed

[Jörg-Volker Peetz]

Jörg-Volker Peetz wrote on 05/14/2015 14:58:
> Theodore Ts'o wrote on 05/14/2015 14:38:
>> On Thu, May 14, 2015 at 10:27:58AM +0200, Jörg-Volker Peetz wrote:
>>>
>>> Also switching to relatime does not work with the mount command. Could it be a
>>> problem with the mount package of debian?
>>
>> I'm using Debian Jessie:
>>
> I'm using a mixture of testing and sid with mount, util-linux, etc. version
> 2.26.2-2.
> 
>> ii  mount                2.25.2-6        amd64           Tools for mounting and manipulating filesystem
>>
>> The other difference might be what you and I have in our /etc/fstab?
>> I have:
>>
>> LABEL=closure-root	/               ext4    errors=remount-ro 0       1
>>
> Here:
>   UUID=7e13aca5-...   /  ext4  nobarrier,noatime,errors=remount-ro  0  2
> 
>> Can you also try something like this?
>>
>> # strace -o /tmp/st mount -o remount,nolazytime /
>> # grep ^mount /tmp/st
>> mount("/dev/sda3", "/", 0x1f21250, MS_MGC_VAL|MS_REMOUNT, "errors=remount-ro,lazytime") = 0
>>
> mount("/dev/sda1", "/", 0x1488780, MS_MGC_VAL|MS_REMOUNT|MS_NOATIME,
> "nobarrier,errors=remount-ro") = 0
> 
After re-reading it again, I should clarify that I meanwhile rebooted with
noatime. Maybe then, it is more helpful to show the output of

# strace -o /tmp/st mount -o remount,lazytime /
# grep ^mount /tmp/st
mount("/dev/sda1", "/", 0x10a0780, MS_REMOUNT|MS_NOATIME|0x2000000,
"nobarrier,errors=remount-ro") = 0

-- 
Regards,
Jörg.


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Re: ext4 lazytime: ctime of some files changed

[Holger Hoffstätte]

On Wed, 13 May 2015 11:35:31 +0200, Jörg-Volker Peetz wrote:

> By the way, the command "mount -o remount,lazytime /" does not do the switch to
> lazytime.

Had the same problem, found the regression:

http://article.gmane.org/gmane.comp.file-systems.ext4/48663

Solution: downgrade to util-linux-2.25.2.

cheers
Holger

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