linux-ext4 - Re: ext4 confusion

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Date:   Mon, 5 Mar 2018 20:42:04 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Eric Sandeen <sandeen@...hat.com>, linux-ext4@...r.kernel.org,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>
Subject: Re: ext4 confusion

On 03/05/2018 08:40 PM, Eric Sandeen wrote:
> On 3/5/18 10:38 PM, Randy Dunlap wrote:
>> On 03/05/2018 08:34 PM, Eric Sandeen wrote:
>>> On 3/5/18 10:17 PM, Randy Dunlap wrote:
>>>> Hi,
>>>>
>>>> With the following kernel config entries on Linux 4.16-rc3:
>>>>
>>>> CONFIG_EXT2_FS=m
>>>> # CONFIG_EXT2_FS_XATTR is not set
>>>> CONFIG_EXT3_FS=m
>>>> # CONFIG_EXT3_FS_POSIX_ACL is not set
>>>> # CONFIG_EXT3_FS_SECURITY is not set
>>>> CONFIG_EXT4_FS=y
>>>> CONFIG_EXT4_FS_POSIX_ACL=y
>>>> CONFIG_EXT4_FS_SECURITY=y
>>>> # CONFIG_EXT4_ENCRYPTION is not set
>>>> # CONFIG_EXT4_DEBUG is not set
>>>> CONFIG_JBD2=y
>>>> # CONFIG_JBD2_DEBUG is not set
>>>>
>>>> ext4_fill_super() tells me:
>>>>
>>>> [    3.033174] EXT4-fs (sda5): couldn't mount as ext3 due to feature incompatibilities
>>>> [    3.100186] EXT4-fs (sda5): mounted filesystem with ordered data mode. Opts: (null)
>>>> [    3.102683] VFS: Mounted root (ext4 filesystem) readonly on device 8:5.
>>>>
>>>>
>>>> This is a new install, new filesystem. It has never been ext2 or ext3.
>>>>
>>>> After bootup and before I do anything else, I can remount /dev/sda5 on / as
>>>> rw and everything is OK.
>>>>
>>>> What am I doing wrong?
>>>
>>> Hm you're the second person to report this in a week.  
>>> (see EXT4-fs (mmcblk0p1): couldn't mount as ext3 due to feature incompatibilities)
>>>
>>> It sounds like filesystem probing behavior; it tried to mount as ext3 and failed
>>> (as it should fail) then moved on to ext4 and succeeded.
>>
>> Mostly succeeded, but why did it leave the filesystem as read-only?
> 
> oh it left it there?  Root usually mounts readonly then transitions to RW.
> That didn't eventually happen?

Nope, I had to do that manually and then everything was OK.

>>
>>> I sent:
>>>
>>> [PATCH V2] ext4: don't complain about incorrect features when probing
>>>
>>> which should fix it, but I really wonder why this is just now showing up for 
>>> people; it could be a combination of /etc/filesystems, fstab entries, blkid
>>> handling in mount, etc...
>>>
>>> Is this a new OS/installer release where this is showing up, or did a simple
>>> kernel upgrade trigger it?  If the latter, what kernel version didn't have
>>> the above kernel message?
>>
>> It's a new OS/installer.  OpenSUSE Tumbleweed, which is their bleeding edge
>> rolling updates release.
> 
> Hrmph.  A lot of things go into this behavior, it may not be a kernel change at
> all that has made it show up now...

Yes, it could be that wonderful systemd or something else.

-- 
~Randy