linux-ext4 - Re: Lazytime undone by/not working with remount?

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Message-ID: <555A02CF.1000506@redhat.com>
Date:	Mon, 18 May 2015 10:18:39 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Karel Zak <kzak@...hat.com>,
	Holger Hoffstätte 
	<holger.hoffstaette@...glemail.com>
CC:	linux-ext4@...r.kernel.org, "Theodore Ts'o" <tytso@....edu>
Subject: Re: Lazytime undone by/not working with remount?

On 5/18/15 3:21 AM, Karel Zak wrote:
> On Sat, May 16, 2015 at 04:26:33PM +0200, Holger Hoffstätte wrote:
>>> playing with lazytime on 4.0.4-rc1 + yesterday's fencepost patch) I noticed
>>> something odd. Mounting secondary (non-root) partitions with lazytime works
>>> fine, but / does not seem to retain the value from fstab - apparently because
>>> it is remounted rw during boot, and lazytime gets swallowed/undone.
>>>
>>> Same effect when trying to remount manually with lazytime:
>>>
>>> tux>findmnt /
>>> TARGET SOURCE    FSTYPE OPTIONS
>>> /      /dev/sda1 ext4   rw,noatime
>>>
>>> tux>mount -o lazytime,remount / 
>>>
>>> tux>dmesg 
>>> [ 5208.482505] EXT4-fs (sda1): re-mounted. Opts: (null)
>>>
>>> tux>findmnt /                  
>>> TARGET SOURCE    FSTYPE OPTIONS
>>> /      /dev/sda1 ext4   rw,noatime
>>>
>>> tux>mount --version
>>> mount from util-linux 2.26.2 (libmount 2.26.0: assert, debug)

And what does /proc/mounts say?  That'll tell you what is actually set
on the superblock.  Works here, on 4.1.0-rc2:

# mount /dev/sdb1 /mnt/test
# mount -o remount,lazytime /mnt/test
# grep sdb1 /proc/mounts 
/dev/sdb1 /mnt/test ext4 rw,lazytime,seclabel,relatime,data=ordered 0 0

# dmesg | tail -n 2
[516203.450943] EXT4-fs (sdb1): mounted filesystem with ordered data mode. Opts: (null)
[516211.222020] EXT4-fs (sdb1): re-mounted. Opts: lazytime

-Eric


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