geli and BIO_FLUSH and/or BIO_ORDERED issue?

[Pawel Jakub Dawidek]

On Tue, Sep 18, 2012 at 09:04:30PM -0700, John-Mark Gurney wrote:
> I was looking at geli and I'm not sure if it's implementing BIO_FLUSH
> and/or BIO_ORDERED properly...
> 
> >From my understanding is the BIO_ORDERED is suppose to wait for the
> previous _WRITES to complete before returning so that you can ensure
> that data is on disk, i.e. _ORDERED is set on a BIO_FLUSH...
> 
> BIO_ORDERED is handled by diskq_* code such that when you add an _ORDERED
> command, all commands are put after it, but there doesn't appear to
> be any code to ensure that an _ORDERED command waits for prevoius
> pending commands to complete..
> 
> This is extra obvious in eli in that a _FLUSH is immediately dispatched,
> even when there may be _WRITEs that haven't been finished encrypting and
> sent down to the disk to get _FLUSHed...
> 
> Any comments about this?

Hmm, BIO_ORDERED was introduced pretty recently and GEOM classes were
not updated to honour it, but it also seems to be to complex to handle
in GEOM classes. I wonder if we could hold off new writes and wait for
the in-progress writes in GEOM if we spot BIO_ORDERED request without
the need to implement this logic in GEOM classes.

-- 
Pawel Jakub Dawidek                       http://www.wheelsystems.com
FreeBSD committer                         http://www.FreeBSD.org
Am I Evil? Yes, I Am!                     http://tupytaj.pl
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