[PATCH] ext3: Update Kconfig description of EXT3_DEFAULTS_TO_ORDERED

From: Jan Kara
Date: Mon Aug 24 2009 - 10:58:46 EST

From: Theodore Ts'o <tytso@xxxxxxx>

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.

Cc: linux-ext4@xxxxxxxxxxxxxxx
Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
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.

- bool "Default to 'data=ordered' in ext3 (legacy option)"
+ bool "Default to 'data=ordered' in ext3"
depends on EXT3_FS
- 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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