geom_multipath and zfs doesn't work

[Nagy, Attila]

Hi,

Running stable/10 at r273159 on FC disks (through isp) I can't create a zfs 
pool.

What I have is a simple device, accessible on /dev/multipath/sas0, 
backed by da0 and da4:
# gmultipath status
            Name   Status  Components
  multipath/sas0  OPTIMAL  da0 (ACTIVE)
                           da4 (READ)

When I issue a
zpool create data /dev/multipath/sas0
command, zpool starts to eat 100% CPU:
# procstat -k 3924
   PID    TID COMM             TDNAME KSTACK
  3924 100128 zpool            - <running>

gstat shows that there is one uncompleted read IO on multipath/sas0 and 
the queue length constantly grows on da0:
# gstat -b
dT: 1.030s  w: 1.000s
  L(q)  ops/s    r/s   kBps   ms/r    w/s   kBps   ms/w %busy Name
  124402    146      0      0    0.0      0      0    0.0 100.5  da0
     0      0      0      0    0.0      0      0    0.0 0.0  da1
     0      0      0      0    0.0      0      0    0.0 0.0  da2
     0      0      0      0    0.0      0      0    0.0 0.0  da3
     1      0      0      0    0.0      0      0    0.0 0.0  multipath/sas0
     0      0      0      0    0.0      0      0    0.0 0.0  da4
     0      0      0      0    0.0      0      0    0.0 0.0  da5
     0      0      0      0    0.0      0      0    0.0 0.0  da6
     0      0      0      0    0.0      0      0    0.0 0.0  da7
     0      0      0      0    0.0      0      0    0.0 0.0  da8
     0      0      0      0    0.0      0      0    0.0 0.0  da9
     0      0      0      0    0.0      0      0    0.0 0.0  multipath/sas1
     0      0      0      0    0.0      0      0    0.0 0.0  multipath/sata0
     0      0      0      0    0.0      0      0    0.0 0.0  multipath/sata1
     0      0      0      0    0.0      0      0    0.0 0.0  md0
     0      0      0      0    0.0      0      0    0.0 0.0  md1

I can use these devices finely with dd.

What's going on here?