[Nbd] Status of FLUSH and FUA stuff

[Alex Bligh <alex@...872...>]

Somewhat surprisingly, the kernel patch worked first time, though (as per
last email) the server needed a minor bug fixing.

I now have nbd running dbench happily with flush and fua support (and
rotational for good measure), with ext3 mounted with data=journal,barrier=1.
I have checked through strace it is doing sensible sync_file_range and
fsync(). It all appears to be working.

I would suggest this is good to go live if marked "experimental" (or
may be good to go live unmarked).

User space commits can be seen at
   http://git.alex.org.uk/nbd.git
I think you want all commits since
   2246d3c69694ee6a4963bc7b0a3e6a9784dd608a

Kernel patch is at:
   http://www.alex.org.uk/nbd-kernel-fua.patch

I have a version of nbd which can be built as a standalone module
(useful for debugging) at
   http://git.alex.org.uk/nbd-module.git

--
Alex Bligh