linux-ext4 - Re: Problem with data=ordered ext4 mount option in linux-next

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Date:   Fri, 17 Dec 2021 18:02:22 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Lukas Czerner <lczerner@...hat.com>
Cc:     linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: Problem with data=ordered ext4 mount option in linux-next

On 17.12.2021 16:34, Heiner Kallweit wrote:
> On 17.12.2021 16:24, Lukas Czerner wrote:
>> On Fri, Dec 17, 2021 at 04:11:32PM +0100, Heiner Kallweit wrote:
>>> On linux-next systemd-remount-fs complains about an invalid mount option
>>> here, resulting in a r/o root fs. After playing with the mount options
>>> it turned out that data=ordered causes the problem. linux-next from Dec
>>> 1st was ok, so it seems to be related to the new mount API patches.
>>>
>>> At a first glance I saw no obvious problem, the following looks good.
>>> Maybe you have an idea where to look ..
>>>
>>> static const struct constant_table ext4_param_data[] = {
>>> 	{"journal",	EXT4_MOUNT_JOURNAL_DATA},
>>> 	{"ordered",	EXT4_MOUNT_ORDERED_DATA},
>>> 	{"writeback",	EXT4_MOUNT_WRITEBACK_DATA},
>>> 	{}
>>> };
>>>
>>> 	fsparam_enum	("data",		Opt_data, ext4_param_data),
>>>
>>
>> Thank you for the report!
>>
>> The ext4 mount has been reworked to use the new mount api and the work
>> has been applied to linux-next couple of days ago so I definitelly
>> assume there is a bug in there that I've missed. I will be looking into
>> it.
>>
>> Can you be a little bit more specific about how to reproduce the problem
>> as well as the error it generates in the logs ? Any other mount options
>> used simultaneously, non-default file system features, or mount options
>> stored within the superblock ?
>>
>> Can you reproduce it outside of the systemd unit, say a script ?
>>
> Yes:
> 
> [root@...ac ~]# mount -o remount,data=ordered /
> mount: /: mount point not mounted or bad option.
> [root@...ac ~]# mount -o remount,discard /
> [root@...ac ~]#
> 
> "systemctl status systemd-remount-fs" shows the same error.
> 
> Following options I had in my fstab (ext4 fs):
> rw,relatime,data=ordered,discard
> 
> No non-default system features.
> 
>> Thanks!
>> -Lukas
>>
> Heiner

Sorry, should have looked at dmesg earlier. There I see:
EXT4-fs: Cannot change data mode on remount
Message seems to be triggered from ext4_check_opt_consistency().
Not sure why this error doesn't occur with old mount API.
And actually I don't change the data mode.