ZFS panic on zvol resize

[Kristof Provost]

Hi,

On current r268263 (and also on stable-10 r268263) I can reliably panic
the machine by simply attempting to resize a zvol:

# zfs create tank/zvol
# zfs set mountpoint=none tank/zvol
# zfs create -V100G tank/zvol/disk0
# zfs set volsize=200G tank/zvol/disk0

It produces the following panic:

panic: solaris assert: !rrw_held(&dp->dp_config_rwlock, RW_READER), file: /usr/src/sys/modules/zfs/../../cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_pool.c, line: 1120
cpuid = 1
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe01217d54b0
kdb_backtrace() at kdb_backtrace+0x39/frame 0xfffffe01217d5560
vpanic() at vpanic+0x126/frame 0xfffffe01217d55a0
panic() at panic+0x43/frame 0xfffffe01217d5600
assfail() at assfail+0x1d/frame 0xfffffe01217d5610
dsl_pool_hold() at dsl_pool_hold+0x67/frame 0xfffffe01217d5650
dmu_objset_hold() at dmu_objset_hold+0x21/frame 0xfffffe01217d5690
dsl_prop_get_integer() at dsl_prop_get_integer+0x28/frame 0xfffffe01217d56d0
zvol_set_volsize() at zvol_set_volsize+0x126/frame 0xfffffe01217d5760
zfs_prop_set_special() at zfs_prop_set_special+0x2e2/frame 0xfffffe01217d57f0
zfs_set_prop_nvlist() at zfs_set_prop_nvlist+0x23f/frame 0xfffffe01217d5880
zfs_ioc_set_prop() at zfs_ioc_set_prop+0x106/frame 0xfffffe01217d58e0
zfsdev_ioctl() at zfsdev_ioctl+0x6ee/frame 0xfffffe01217d5990
devfs_ioctl_f() at devfs_ioctl_f+0xfb/frame 0xfffffe01217d59f0
kern_ioctl() at kern_ioctl+0x22b/frame 0xfffffe01217d5a50
sys_ioctl() at sys_ioctl+0x13c/frame 0xfffffe01217d5aa0
amd64_syscall() at amd64_syscall+0x25a/frame 0xfffffe01217d5bb0
Xfast_syscall() at Xfast_syscall+0xfb/frame 0xfffffe01217d5bb0
--- syscall (54, FreeBSD ELF64, sys_ioctl), rip = 0x8019e89ba, rsp = 0x7fffffffb8c8, rbp = 0x7fffffffb940 ---
Uptime: 2m18s
Automatic reboot in 15 seconds - press a key on the console to abort

Please let me know if there's any other information which could be
helpful, or any patch I could test.

Regards,
Kristof