Re: kern/51037

[mlelstv%serpens.de@localhost (Michael van Elst)]

The following reply was made to PR kern/51037; it has been noted by GNATS.

From: mlelstv%serpens.de@localhost (Michael van Elst)
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: kern/51037
Date: Mon, 15 Aug 2016 09:19:35 +0000 (UTC)

 agrier%poofygoof.com@localhost ("Aaron J. Grier") writes:
 
 > from https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=209700:
 > > It [FreeBSD target] supports tagged queueing of commands marked as
 > > tagged.  For some reason the NetBSD initiator sets the "flags" field
 > > of SCSI Command PDU to Untagged (0).  Not sure what the SCSI spec
 > > says, to be honest, but it might it be an initiator error?
 > 
 > turned on #define ISCSI_DEBUG 10 to see if I could get any clues, but
 > nothing obvious is sticking out, maybe another set of eyes?
 
 You see that on the iSCSI layer multiple commands are sent to
 the target, but (what you cannot see) the commands are marked
 as untagged and therefore should be executed in-order, so no
 overlap should be possible.
 
 In -current I did some signficant changes to the iSCSI initiator
 including how tagging is handled.
 
 The first attempt was to mark all requests as tagged and simply
 ordered but I ignored the actual tag values, this stopped the
 'illegal request' errors immediately.
 
 Now it passes tags from scsipi to the iSCSI layer which is probably
 the right thing to do if you support taggging.
 
 IMHO the FreeBSD target has an issue in how it handles untagged
 requests, but I haven't found anything suspicious when looking
 at the FreeBSD code.
 
 -- 
 -- 
                                 Michael van Elst
 Internet: mlelstv%serpens.de@localhost
                                 "A potential Snark may lurk in every tree."