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ext3: Update Kconfig description of EXT3_DEFAULTS_TO_ORDERED 

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@vger.kernel.org
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Theodore Ts'o 2009-08-10 16:03:43 -04:00 committed by Jan Kara
parent f4b9a98868
commit 6d41807614
1 changed files with 15 additions and 13 deletions
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fs/ext3/Kconfig
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@ -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'.
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:
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.
http://ext4.wiki.kernel.org/index.php/Ext3_data_mode_tradeoffs
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.
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"