linux-kernel - Re: EXT4: new warnings from 4.3.0-rc2

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Date:	Mon, 21 Sep 2015 15:55:05 +0100
From:	Chris Clayton <chris2553@...glemail.com>
To:	Ortwin Glück <odi@....ch>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: EXT4: new warnings from 4.3.0-rc2

Thanks Ortwin.

On 09/21/15 14:27, Ortwin GlÃ¼ck wrote:
>> [    2.481399] EXT4-fs (sda2): couldn't mount as ext3 due to feature incompatibilities
>> [    2.482426] EXT4-fs (sda2): couldn't mount as ext2 due to feature incompatibilities
> 
> As the kernel doesn't know which FS your root is, it tries the whole list of filesystems (init/do_mounts.c
> mount_block_root()). Since the removal of ext3, now the ext4 code is responsbile for mounting ext3. Since your FS is
> ext4 and not ext3, the probe for ext3 fails. That's what the message tells you. You get these even in previous kernels
> if you say N to ext3 during config.
> 
No, I do not get the messages from 4.2.0 even though it is configured the same as 4.3.0-rc3 as far as EXT{2,3,4} is
concerned:

# CONFIG_EXT2_FS is not set
# CONFIG_EXT3_FS is not set
CONFIG_EXT4_FS=y
CONFIG_EXT4_USE_FOR_EXT2=y
# CONFIG_EXT4_FS_POSIX_ACL is not set
# CONFIG_EXT4_FS_SECURITY is not set
# CONFIG_EXT4_ENCRYPTION is not set
# CONFIG_EXT4_DEBUG is not set
[chris:~/kernel/linux]$ cd ../linux-4.2.0/
[chris:~/kernel/linux-4.2.0]$ grep EXT[234] .config
# CONFIG_EXT2_FS is not set
# CONFIG_EXT3_FS is not set
CONFIG_EXT4_FS=y
CONFIG_EXT4_USE_FOR_EXT23=y
# CONFIG_EXT4_FS_POSIX_ACL is not set
# CONFIG_EXT4_FS_SECURITY is not set
# CONFIG_EXT4_ENCRYPTION is not set
# CONFIG_EXT4_DEBUG is not set

That's why I said they are new messages.

I've just booted 4.1.7 and I get the messages from that kernel too. I wonder if there's a recent fix that has made it
into 4.1.7, but not into 4.2.0. I'll apply Greg's 4.2.1-rc1 patch and see what I get with that.

Chris


> If it bugs you, you can add a hint to your kernel command line: rootfstype=ext4
> 
> Ortwin
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