XFS ignores all atime related mount options, noatime is always in effect, documentation misses this information

XFS ignores all atime related mount options, noatime is always in effect, documentation misses this information

[Roland Eggner]

On my linux box I tried to achieve regular atime behaviour, tried mount with
no atime related option at all, tried mount options atime, sync,
osyncisosync, .. XFS on plain partitions, on loop devices .. I tried another
kernel (sidux image with kernel 2.6.25-9) ..

My result:
It seems impossible to switch off "noatime" mount option.
atime updates happen only in core, never on disk unless coinciding with other
inode modifications, regardless of specified mount options.

$  uname -a
Linux roland 2.6.23.12roland2 #2 Tue Apr 15 17:10:52 CEST 2008 i686 GNU/Linux

$  zgrep XFS /proc/config.gz
CONFIG_XFS_FS=m
# CONFIG_XFS_QUOTA is not set
CONFIG_XFS_SECURITY=y
CONFIG_XFS_POSIX_ACL=y
CONFIG_XFS_RT=y
# CONFIG_VXFS_FS is not set

In mailing list archive I found
http://oss.sgi.com/archives/xfs/2007-10/msg00168.html
It seems, that 3 years ago an unconditional noatime enforcement has been
introduced.

(1)  If this is true, please update documentation accordingly.
Users, who need a filesystem with regular atime behaviour, will no more waste
their time to try XFS, when in fact it is unusable for their particular
requirements.

(2)  If I missed a possibility to achieve regular atime behaviour, please
document it in Documentation/filesystems/xfs.txt and in man 8 mount.

Thanks!

-- 
Roland Eggner

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Re: XFS ignores all atime related mount options, noatime is always in effect, documentation misses this information

[Martin Steigerwald]

Am Donnerstag 18 Dezember 2008 schrieb Roland Eggner:
> On my linux box I tried to achieve regular atime behaviour, tried mount
> with no atime related option at all, tried mount options atime, sync,
> osyncisosync, .. XFS on plain partitions, on loop devices .. I tried
> another kernel (sidux image with kernel 2.6.25-9) ..
>
> My result:
> It seems impossible to switch off "noatime" mount option.
> atime updates happen only in core, never on disk unless coinciding with
> other inode modifications, regardless of specified mount options.
>
> $  uname -a
> Linux roland 2.6.23.12roland2 #2 Tue Apr 15 17:10:52 CEST 2008 i686
> GNU/Linux

I can't reproduce this on 2.6.27.7:

martin@shambhala:~/Zeit> grep /home /proc/mounts
/dev/sda5 /home xfs 
rw,relatime,attr2,nobarrier,logbufs=8,logbsize=256k,noquota 0 0
martin@shambhala:~/Zeit> echo "hallo" >hallo.txt
martin@shambhala:~/Zeit> ls -l --time=atime hallo.txt
-rw-r--r-- 1 martin martin 6 19. Dez 13:56 hallo.txt
martin@shambhala:~/Zeit> cat hallo.txt ; ls -l --time=atime hallo.txt
hallo
-rw-r--r-- 1 martin martin 6 19. Dez 13:57 hallo.txt

How did you test it? A reproducable test case would be fine.

> $  zgrep XFS /proc/config.gz
> CONFIG_XFS_FS=m
> # CONFIG_XFS_QUOTA is not set
> CONFIG_XFS_SECURITY=y
> CONFIG_XFS_POSIX_ACL=y
> CONFIG_XFS_RT=y
> # CONFIG_VXFS_FS is not set

martin@shambhala:~> zgrep XFS /proc/config.gz
CONFIG_XFS_FS=y
CONFIG_XFS_QUOTA=y
CONFIG_XFS_POSIX_ACL=y
CONFIG_XFS_RT=y
# CONFIG_XFS_DEBUG is not set
# CONFIG_VXFS_FS is not set

> In mailing list archive I found
> http://oss.sgi.com/archives/xfs/2007-10/msg00168.html
> It seems, that 3 years ago an unconditional noatime enforcement has
> been introduced.

Did you look within the same mount or did you unmount and remount first? I 
remember there has been some issue with inode updates and unmounting, but 
I do not remember the details.

> (2)  If I missed a possibility to achieve regular atime behaviour,
> please document it in Documentation/filesystems/xfs.txt and in man 8
> mount.

Its either atime, relatime or noatime as mount option.

Ciao,
-- 
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA  B82F 991B EAAC A599 84C7

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