On 01/18/2018 11:27 AM, Christoph Hellwig wrote:
[adding Chris to the Cc list - this is about the awful ext3 data=ordered
behavior of syncing the whole file system data and metadata on each
fsync]
On Wed, Jan 17, 2018 at 03:57:53PM -0800, Linus Torvalds wrote:
On Wed, Jan 17, 2018 at 3:52 PM, Theodore Ts'o <tytso@xxxxxxx> wrote:
Well, let's be fair; this is something *ext3* got wrong, and it was
the default file system back them.
I'm pretty sure reiserfs and btrfs did too..
I'm pretty sure btrfs never did, and reiserfs at least looks like
it currently doesn't but I'd have to dig into history to check if
it ever did.
Christoph has this right, btrfs only fsyncs the one file that you've
asked for, and unrelated data/metadata won't be included.
We've seen big fsync stalls on ext4 caused by data=ordered, so it's
still possible to trigger on ext4, but much better than ext3.
I do share Ted's concern about the perf impact of the fsyncs on tons of
loose files, but the defaults should be safety first.
-chris
