On 01/15/2010 02:30 PM, Theodore Ts'o wrote:
I've worked with Jiaying to ready this patch for submission.
It's currently a mount option for maximum safety, but after we do some
benchmarking to make sure it doesn't degrade performance for buffered
writes, we may want to make this the default. Once really nice side
effect of this patch is that it effectively gives us "guarded mode" by
default, since the blocks are marked as uninitialized and only converted
to be initialized when the I/O has completed for both buffered and
direct I/O writes now. This means that we could possibly change the
default mode to be data=writeback if the extents feature is enabled,
since data=ordered would only needed for safety when writing new
old-style indirect blocks.
The plan is to merge this for 2.6.34. I've looked this over pretty
carefully, but another pair of eyes would be appreciated, especially if
we make this the default. Beyond the advantages of being able to use
data=writeback, I believe this should be a major win for database
workloads.
- Ted
I would be really cautious about turning this on unless we are 100%
certain that we have not introduced data integrity issues. Performance
testing is great, but we need to work hard on the power failure testing,
etc as well....
What ever did happen to guarded mode? Is it still lurking out there?
ric
Theodore Ts'o (3):
ext4: mechanical change on dio get_block code in prepare for it to be
used by buffer write
ext4: use ext4_get_block_write in buffer write
ext4: Use direct_IO_no_locking in ext4 dio read.
fs/ext4/ext4.h | 28 +++++---
fs/ext4/ext4_jbd2.h | 24 +++++++
fs/ext4/extents.c | 36 +++++-----
fs/ext4/fsync.c | 2 +-
fs/ext4/inode.c | 192 +++++++++++++++++++++++++++++++++-----------------
fs/ext4/super.c | 32 +++++++--
6 files changed, 217 insertions(+), 97 deletions(-)
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