Re: Bug In ext4 in kernels > 2.6.39 - Not mounting with arguments/options I specify in fstab on root remount

[Matt Parnell <mparnell@gmail.com>]

On 11/07/2011 07:47 AM, Ted Ts'o wrote:
> On Sun, Nov 06, 2011 at 09:26:57PM -0800, Matt Parnell wrote:
>> I figured it out. data=writeback isn't needed and is done by default
>> if there's no journal, as per commit
>> 373cd5c53d5ea6622c319ecd84e29e2737d488bd http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=373cd5c53d5ea6622c319ecd84e29e2737d488bd
>>
>> ...sorry about throwing you guys through loops over this, although
>> I'm guessing there's still a bug in that the kernel should just warn
>> the user about the option when it's used and otherwise ignore it
>> instead of breaking if there's no journal.
> Ah, OK.  It wasn't clear to me that you were running without a year.
> You're right, we shouldn't complain in that case, since we ignore the
> messages when mounting the file system.  Actually, we parse the
> options when we are mounting the file system, but then we zero them
> out when we discover that there's no journal; but in any case, we
> should similarly ignore the pointless data=* mount options (for a file
> system w/o a journal) on the remount operation as well.
>
>       	     	      	     	     	       	  - Ted
>
> commit eb513689c97e3e73bb9b4459d490a8e894b4a546
> Author: Theodore Ts'o<tytso@mit.edu>
> Date:   Mon Nov 7 10:47:42 2011 -0500
>
>      ext4: ignore journalled data options on remount if fs has no journal
>
>      This avoids a confusing failure in the init scripts when the
>      /etc/fstab has data=writeback or data=journal but the file system does
>      not have a journal.  So check for this case explicitly, and warn the
>      user that we are ignoring the (pointless, since they have no journal)
>      data=* mount option.
>
>      Signed-off-by: "Theodore Ts'o"<tytso@mit.edu>
>
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 9953d80..0435013 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1683,7 +1683,9 @@ static int parse_options(char *options, struct super_block *sb,
>   			data_opt = EXT4_MOUNT_WRITEBACK_DATA;
>   		datacheck:
>   			if (is_remount) {
> -				if (test_opt(sb, DATA_FLAGS) != data_opt) {
> +				if (!sbi->s_journal)
> +					ext4_msg(sb, KERN_WARNING, "Remounting file system with no journal so ignoring journalled data option");
> +				else if (test_opt(sb, DATA_FLAGS) != data_opt) {
>   					ext4_msg(sb, KERN_ERR,
>   						"Cannot change data mode on remount");
>   					return 0;
Great! I'm glad we managed to track this one down. I'm not using the 
flags anymore, but I'll be glad when your patch there makes it into ext4 
for other users.