Re: Plan: journalling fixes for WAPBL

[Thor Lancelot Simon <tls%panix.com@localhost>]

On Fri, Sep 23, 2016 at 07:45:00PM +0200, Manuel Bouyer wrote:
> On Fri, Sep 23, 2016 at 05:15:16PM +0000, Eric Haszlakiewicz wrote:
> > On September 23, 2016 10:51:30 AM EDT, Warner Losh <imp%bsdimp.com@localhost> wrote:
> > >All NCQ gives you is the ability to schedule multiple requests and
> > >to get notification of their completion (perhaps out of order). There's
> > >no coherency features are all in NCQ.
> > 
> > This seems like the key thing needed to avoid FUA: to implement fsync() you just wait for notifications of completion to be received, and once you have those for all requests pending when fsync was called, or started as part of the fsync, then you're done.
> 
> *if you have the write cache disabled*

*Running with the write cache enabled is a bad idea*