linux-ext4 - Re: ext4 confusion

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Message-ID: <42504c61-393b-6c34-7a01-b82dd0d9064f@infradead.org>
Date:   Mon, 5 Mar 2018 20:38:33 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     sandeen@...hat.com, linux-ext4@...r.kernel.org,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>
Subject: Re: ext4 confusion

On 03/05/2018 08:34 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?

> 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.

thanks,
-- 
~Randy