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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                        mhitch%montana.edu@localhost
Computer Consultant
Information Technology Center
Montana State University        Bozeman, MT     USA


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