ext3: make default data ordering mode configurable
This makes the defautl ext3 data ordering mode (when no explicit
ordering is set) configurable, so as to allow people to default to
'data=writeback' and get the resulting latency improvements.
This is a non-issue if a filesystem has been explicitly set to some
ordering (with 'tune2fs').
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/ext3/Kconfig b/fs/ext3/Kconfig
index 8e0cfe4..fb3c1a2 100644
--- a/fs/ext3/Kconfig
+++ b/fs/ext3/Kconfig
@@ -28,6 +28,25 @@
To compile this file system support as a module, choose M here: the
module will be called ext3.
+config EXT3_DEFAULTS_TO_ORDERED
+ bool "Default to 'data=ordered' in ext3 (legacy option)"
+ 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.
+
config EXT3_FS_XATTR
bool "Ext3 extended attributes"
depends on EXT3_FS
diff --git a/fs/ext3/super.c b/fs/ext3/super.c
index 9e5b8e3..599dbfe 100644
--- a/fs/ext3/super.c
+++ b/fs/ext3/super.c
@@ -44,6 +44,12 @@
#include "acl.h"
#include "namei.h"
+#ifdef CONFIG_EXT3_DEFAULTS_TO_ORDERED
+ #define EXT3_MOUNT_DEFAULT_DATA_MODE EXT3_MOUNT_ORDERED_DATA
+#else
+ #define EXT3_MOUNT_DEFAULT_DATA_MODE EXT3_MOUNT_WRITEBACK_DATA
+#endif
+
static int ext3_load_journal(struct super_block *, struct ext3_super_block *,
unsigned long journal_devnum);
static int ext3_create_journal(struct super_block *, struct ext3_super_block *,
@@ -1919,7 +1925,7 @@
cope, else JOURNAL_DATA */
if (journal_check_available_features
(sbi->s_journal, 0, 0, JFS_FEATURE_INCOMPAT_REVOKE))
- set_opt(sbi->s_mount_opt, ORDERED_DATA);
+ set_opt(sbi->s_mount_opt, DEFAULT_DATA_MODE);
else
set_opt(sbi->s_mount_opt, JOURNAL_DATA);
break;