linux-ext4 - Re: RFC PATCH: ext4 no journal corruption with locale-gen

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Date:	Mon, 6 Jul 2009 09:21:25 -0700
From:	Xiang Wang <xiangw@...gle.com>
To:	Theodore Tso <tytso@....edu>
Cc:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Curt Wohlgemuth <curtw@...gle.com>,
	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: RFC PATCH: ext4 no journal corruption with locale-gen

On Sun, Jul 5, 2009 at 8:41 PM, Theodore Tso<tytso@....edu> wrote:
> On Thu, Jul 02, 2009 at 12:01:30AM +0530, Aneesh Kumar K.V wrote:
>>
>> I looked at the patch in detail and  I guess we should instead force
>> a data=writeback mode if the filesystem is created without a journal.
>> I am not sure what whould be the meaning of data=ordered/data=journal
>> without a journal. So if we find that file system doesn't have a journal
>> then either we should update the default mount option in the filesystem
>> to be of data=writeback.
>
> Here's a patch which takes your approach to solving the problem.  What
> do you think?
>
> I haven't messed with dealing with the data= mount options in
> fs/ext4/super.c.  That's important from a UI point of view, but we
> needed to fix ext4_jbd2.h since it was unconditionally returning 0 if
> there was no journal for all of the ext4_should_*_data() functions.
>
> I believe this should DTRT with the -o nobh mount option, but I'd
> appreciate another pair of eyes taking a look at this.

This patch looks good to us.

In the long run, we still think adding the data=nojournal mount option
is useful and we are working on this patch.

Thanks,
Xiang

>
>                                         - Ted
>
> commit 2a73eff8ba80095a871a6b402dfd24bc454e5bdc
> Author: Theodore Ts'o <tytso@....edu>
> Date:   Sun Jul 5 23:37:13 2009 -0400
>
>    ext4: fix no journal corruption with locale-gen
>
>    If there is no journal, ext4_should_writeback_data() should return
>    TRUE.  This will fix ext4_set_aops() to set ext4_da_ops in the case of
>    delayed allocation; otherwise ext4_journaled_aops gets used by
>    default, which doesn't handle delayed allocation properly.
>
>    The advantage of using ext4_should_writeback_data() approach is that
>    it should handle nobh better as well.
>
>    Thanks to Curt Wohlgemuth for investigating this problem, and Aneesh
>    Kumar for suggesting this approach.
>
>    Signed-off-by: "Theodore Ts'o" <tytso@....edu>
>
> diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h
> index be2f426..f800134 100644
> --- a/fs/ext4/ext4_jbd2.h
> +++ b/fs/ext4/ext4_jbd2.h
> @@ -282,7 +282,7 @@ static inline int ext4_should_order_data(struct inode *inode)
>  static inline int ext4_should_writeback_data(struct inode *inode)
>  {
>        if (EXT4_JOURNAL(inode) == NULL)
> -               return 0;
> +               return 1;
>        if (!S_ISREG(inode->i_mode))
>                return 0;
>        if (EXT4_I(inode)->i_flags & EXT4_JOURNAL_DATA_FL)
> --
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