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SubjectRe: [PATCH, RFC] ext3: Update Kconfig description of EXT3_DEFAULTS_TO_ORDERED
On 08/10/2009 04:03 PM, Theodore Ts'o wrote:
> The old description for this configuration option was perhaps not
> completely balanced in terms of describing the tradeoffs of using a
> default of data=writeback vs. data=ordered. Despite the fact that old
> description very strongly recomended disabling this feature, all of
> the major distributions have elected to preserve the existing 'legacy'
> default, which is a strong hint that it perhaps wasn't telling the
> whole story.
>
> This revised description has been vetted by a number of ext3
> developers as being better at informing the user about the tradeoffs
> of enabling or disabling this configuration feature.
>
> Signed-off-by: "Theodore Ts'o"<tytso@mit.edu>
> Cc: linux-ext4@vger.kernel.org
>

Thanks Ted - this is much more informative and will allow for a more
informed trade off to be made,

Ric

> ---
> fs/ext3/Kconfig | 32 +++++++++++++++++---------------
> 1 files changed, 17 insertions(+), 15 deletions(-)
>
> diff --git a/fs/ext3/Kconfig b/fs/ext3/Kconfig
> index fb3c1a2..522b154 100644
> --- a/fs/ext3/Kconfig
> +++ b/fs/ext3/Kconfig
> @@ -29,23 +29,25 @@ config EXT3_FS
> module will be called ext3.
>
> config EXT3_DEFAULTS_TO_ORDERED
> - bool "Default to 'data=ordered' in ext3 (legacy option)"
> + bool "Default to 'data=ordered' in ext3"
> depends on EXT3_FS
> help
> - If a filesystem does not explicitly specify a data ordering
> - mode, and the journal capability allowed it, ext3 used to
> - historically default to 'data=ordered'.
> -
> - That was a rather unfortunate choice, because it leads to all
> - kinds of latency problems, and the 'data=writeback' mode is more
> - appropriate these days.
> -
> - You should probably always answer 'n' here, and if you really
> - want to use 'data=ordered' mode, set it in the filesystem itself
> - with 'tune2fs -o journal_data_ordered'.
> -
> - But if you really want to enable the legacy default, you can do
> - so by answering 'y' to this question.
> + The journal mode options for ext3 have different tradeoffs
> + between when data is guaranteed to be on disk and
> + performance. The use of "data=writeback" can cause
> + unwritten data to appear in files after an system crash or
> + power failure, which can be a security issue. However,
> + "data=ordered" mode can also result in major performance
> + problems, including seconds-long delays before an fsync()
> + call returns. For details, see:
> +
> + http://ext4.wiki.kernel.org/index.php/Ext3_data_mode_tradeoffs
> +
> + If you have been historically happy with ext3's performance,
> + data=ordered mode will be a safe choice and you should
> + answer 'y' here. If you understand the reliability and data
> + privacy issues of data=writeback and are willing to make
> + that trade off, answer 'n'.
>
> config EXT3_FS_XATTR
> bool "Ext3 extended attributes"
>



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