kern/51037: iscsi initiator fails sporadically with "illegal request" error with FreeBSD-10.2 ctl target

[agrier%pythagoras.poofy.goof.com@localhost]

>Number:         51037
>Category:       kern
>Synopsis:       iscsi initiator fails sporadically with "illegal request" error with FreeBSD-10.2 ctl target
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Apr 02 06:55:00 +0000 2016
>Originator:     agrier%pythagoras.poofy.goof.com@localhost
>Release:        NetBSD 7.0_STABLE
>Organization:
  Aaron J. Grier | "Not your ordinary poofy goof." | agrier%poofygoof.com@localhost
>Environment:
	
	
System: NetBSD pythagoras.poofy.goof.com 7.0_STABLE NetBSD 7.0_STABLE (X2200M2_DOM0) #0: Tue Nov 17 22:49:19 PST 2015 agrier%arignote.poofy.goof.com@localhost:/var/obj/7.0_STABLE/X2200M2_DOM0 amd64
X2200M2_DOM0 is XEN3_DOM0 with pseudo-device iscsi enabled, and limited
matching of bge device to avoid clobbering out-of-band management port.
FreeBSD target is 10.2-RELEASE.
Architecture: x86_64
Machine: amd64
>Description:
NetBSD-7 in-kernel initiator (iscsid) is able to connect to a FreeBSD
10.2 ctl-provided target, but receives write errors when attempting to
newfs a slice:

# scsictl sd1 identify
/dev/rsd1d: scsibus1 target 0 lun 0 <FREEBSD, CTLDISK, 0001>
# gpt show sd1
      start       size  index  contents
          0          1         PMBR
          1          1         Pri GPT header
          2         32         Pri GPT table
         34          6
         40   83884026      1  GPT part - NetBSD FFSv1/FFSv2
   83884066    4196276      2  GPT part - NetBSD swap
   88080342  184549385      3  GPT part - NetBSD FFSv1/FFSv2
  272629727         32         Sec GPT table
  272629759          1         Sec GPT header
# dkctl sd1 listwedges
/dev/rsd1d: 3 wedges:
dk0: 7c2a809e-fba9-4d45-867c-d7544833743c, 83884026 blocks at 40, type: ffs
dk1: 76c19470-cd40-4ef6-885f-ad3ede7873e0, 4196276 blocks at 83884066, type: swap
dk2: 3789d038-600c-45c6-b48c-e8639473948a, 184549385 blocks at 88080342, type: ffs
# newfs dk2
/dev/rdk2: 90112.0MB (184549384 sectors) block size 16384, fragment size 2048
        using 489 cylinder groups of 184.28MB, 11794 blks, 23296 inodes.
super-block backups (for fsck_ffs -b #) at:
32, 377440, 754848, 1132256, 1509664, 1887072, 2264480, 2641888, 3019296,
.wtfs: write error for sector 7930336: Invalid argument
# dmesg | tail -1
sd1(iscsi0:0:0:0): illegal request, data = 00 00 00 00 4e 00

this happens both in the dom0 and a domU which has the iscsi target exported
as an xbd.
>How-To-Repeat:
create ZFS block device (zfs create -V130G tank/foo)
export as iscsi lun target in FreeBSD (edit /etc/ctl.conf, start ctld)
attach to NetBSD initiator (start iscsid, iscsctl {add_send_target,
  refresh_targets, login})
GPT partition device (gpt create sd1, gpt add -s xxx -t ffs sd1)
add slices (dkctl ...)
format a slice (newfs dk2)
>Fix:
	

>Unformatted: