On 08/12/2011 09:16 AM, Lukas Czerner wrote:
On Thu, 11 Aug 2011, Andreas Dilger wrote:
On 2011-08-11, at 9:01 AM, Lukas Czerner wrote:
On Tue, 28 Jun 2011, Lukas Czerner wrote:
Data journalling mode (data=journal) is known to be neglected by
developers and only minority of people is actually using it. This
mode is also less tested than the other two modes by the developers.
This creates a dangerous combination, because the option which seems
*safer* is actually less safe the others. So this commit adds a warning
message in case that data=journal mode is used, so the user is informed
that the mode might be removed in the future.
Any comments on this ? Is that feasible to remove is someday ?
I'm less in favour of removing data=journal. Jan made some fixes to
data=journal mode in the last few weeks, which means that people are
still using this.
I think that Jan was actually the one who was in favour of this change
IIRC. But you're right that there are still some (very little possibly?)
users of this. But this change does not remove it, but just let the
users know that it might be removed someday, hence discouraging them from
using it.
Also we were discussing that several times, so I think that letting
users know that we are considering it is a good thing.
Thanks!
-Lukas
I think that this will be very useful to have - users should definitely chime in
when they see this warning if they are using data journal mode.
The only work load that I know that benefits from a performance point of view is
one which involves an fsync() heavy, small file creation workload. Any workload
with larger files tends to lose roughly 50% of the write bandwidth under
streaming writes since we end up writing everything twice.
Regards,
Ric
Signed-off-by: Lukas Czerner<lczerner@xxxxxxxxxx>
---
fs/ext4/super.c | 5 +++++
1 files changed, 5 insertions(+), 0 deletions(-)
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 9ea71aa..9d189cf 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1631,6 +1631,11 @@ static int parse_options(char *options, struct super_block *sb,
sbi->s_min_batch_time = option;
break;
case Opt_data_journal:
+ ext4_msg(sb, KERN_WARNING,
+ "Using data=journal may be removed in the "
+ "future. Please, contact "
+ "linux-ext4@xxxxxxxxxxxxxxx if you are "
+ "using this feature.");
data_opt = EXT4_MOUNT_JOURNAL_DATA;
goto datacheck;
case Opt_data_ordered:
--
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Cheers, Andreas
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