Commit 6d418076 authored by Theodore Ts'o's avatar Theodore Ts'o Committed by Jan Kara
Browse files

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: default avatar"Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent f4b9a988

fs/ext3/Kconfig

+17 −15
Original line number Diff line number Diff line
@@ -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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