Jamie Lokier wrote:

Theodore Tso wrote:

quoted

On Fri, May 16, 2008 at 02:09:56PM -0500, Eric Sandeen wrote:

quoted

To ensure that bits are truly on-disk after an fsync,
we should call blkdev_issue_flush if barriers are supported.

This patch isn't necessary, and in fact will cause a double flush.
When you call fsync(), it calls ext4_force_commit(), and we do a the
equivalent of a blkdev_issue_flush() today (which is what happenes
when you do a submit_bh(WRITE_BARRIER, bh), which is what setting
set_ordered_mode(bh) ends up causing.

ISTR fsync() on ext3 did not always force a commit, if in-place data
writes did not change any metadata.

I think that might still be true, but I'm still looking through it (in
the background...)

I tried blktrace to see what was going on but I'm not sure what an "NB"
in the RWBS field means, anyone know?

-Eric