RFC: Pass TRIM through GELI

[Matthew D. Fuller]

On Sun, Mar 08, 2015 at 11:05:29PM +0000 I heard the voice of
Steven Hartland, and lo! it spake thus:
> 
> IIRC ufs doesn't support TRIM by default, it needs to be manually
> enabled.

But if you `newfs -t` it, and then mount on a stack that doesn't
support TRIM, it notices and doesn't send any BIO_DELETE's.


> GELI is kind of different though given is use, I'm sure users of it
> would expect delete to leave no trace of the data which was there,
> which is what I was under the impression it does, correct me if I'm
> wrong?

Oh, I see where you're coming from.  No, there's a comment suggesting
it could shred the data, but that's never been implemented.  The
current code just falls through to the default case of the switch and
denies it:


.   case BIO_DELETE:
.   .   /*
.   .    * We could eventually support BIO_DELETE request.
.   .    * It could be done by overwritting requested sector with
.   .    * random data g_eli_overwrites number of times.
.   .    */
.   default:
.   .   g_io_deliver(bp, EOPNOTSUPP);
.   .   return;



-- 
Matthew Fuller     (MF4839)   |  fullermd at over-yonder.net
Systems/Network Administrator |  http://www.over-yonder.net/~fullermd/
           On the Internet, nobody can hear you scream.