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Re: scsipi mid-layer, tagged queueing, and ciss(4)

On Mon, 30 Aug 2010, Manuel Bouyer wrote:

I had thought about mentioning that as another option, since I had
actually tried that first, if I remember correctly.  That resulted
in a number of invalid command errors, with useless information.

  I switched back to patching the inquiry data, and didn't see any ciss(4)
messages during my initial testing unless I specifically ran scsictl or
dkctl to flush/sync the cache. When I finally got to the point of mounting a wapbl filesystem rw, I started getting a number of them. What I've done currently is supress that ciss(4) message for the SCSI_SYNCHRONIZE_CACHE_10 command. That's the patch I'm going with for now.

There's a comment in the code about emulating the SYNCHRONIZE_CACHE that came from the OpenBSD driver. Looking through the FreeBSD driver, they originally were issuing a controller flush command, but it has been disabled with a commit message about it hanging the controller. That command isn't in any documentation that I have found, and I don't quite understand the way OpenBSD driver is using it. The cissreg.h file shows a CISS_FLUSH_ENABLE and CISS_FLUSH_DISABLE code passed by the command, and the OpenBSD/NetBSD driver is setting the CISS_FLUSH_DISABLE code when it does a shutdown. From what I can tell with the FreeBSD and Linux drivers, they are using CISS_FLUSH_ENABLE when shutting down. So I'm not sure if we are getting the controller cache flushed properly on shutdown at the moment.

Michael L. Hitch              
Computer Consultant
Information Technology Center
Montana State University        Bozeman, MT     USA

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