linux-kernel - Re: [PATCH] ext4: clarify error messages for mounting fs w/o journal /w journal options

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Date:	Fri, 12 Feb 2016 18:32:47 +0100
From:	Georg Altmann <george@...rge-net.de>
To:	unlisted-recipients:; (no To-header on input)
Cc:	adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ext4: clarify error messages for mounting fs w/o journal
 /w journal options



Am 12.02.2016 um 18:03 schrieb Theodore Ts'o:
> On Fri, Feb 12, 2016 at 02:31:49PM +0100, Georg Altmann wrote:
>> Previous message was hard to understand: When mounting a ext4 fs without a
>> journal, but a mount option that controls journaling is used, clearly state
>> that the fs cannot be mounted with this option because it has no journal.
> 
> Well, technically it's possible for the file system to have a journal,
> but for journalling not to be enabled.  For example:
> 
> root@...-xfstests:~# dmesg -n 7
> root@...-xfstests:~# mke2fs -t ext4 -Fq /dev/vdc
> /dev/vdc contains a ext4 file system
> 	created on Fri Feb 12 11:59:10 2016
> root@...-xfstests:~# dumpe2fs /dev/vdc | grep features
> dumpe2fs 1.43-WIP (18-May-2015)
> Filesystem features:      has_journal ext_attr resize_inode dir_index filetype extent 64bit flex_bg sparse_super large_file huge_file dir_nlink extra_isize metadata_csum
> Journal features:         (none)
> root@...-xfstests:~# mount -o noload,commit=1 /dev/vdc /vdc 2> /dev/null
> [  313.867505] EXT4-fs (vdc): can't mount with commit=1, fs mounted w/o journal
> 
> So saying "fs has no journal" isn't necessarily going to be correct.
> Maybe "Can't mount with data=xxx, journalling not enabled" would be
> less confusing to users?

Yes.

I do not understand the error checking logic here enough:
it could be either fs without journal or journal not enabled, right?
So how about
"can't mount with data=xxx, journalling not enabled or no journal"
?

Or, if this can be justified in regard of code complexity, handle both
cases separately. Even nicer diagnostics for the user...

Should I send a new patch?

Regards,
Georg


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