MFC r246631,246651,246666,246675,246678,246688:
Merge various ZFS bugfixes
MFC r246631:
Import vendor bugfixes
Illumos ZFS issues:
3422 zpool create/syseventd race yield non-importable pool
3425 first write to a new zvol can fail with EFBIG
MFC r246651:
Import minor type change in refcount.h header from vendor (illumos).
MFC r246666:
Import vendor ZFS bugfix fixing a problem in arc_read().
Illumos ZFS issues:
3498 panic in arc_read(): !refcount_is_zero(&pbuf->b_hdr->b_refcnt)
MFC r246675:
Add tunable to allow block allocation on degraded vdevs.
Illumos ZFS issues:
3507 Tunable to allow block allocation even on degraded vdevs
MFC r246678:
Import vendor bugfixes regarding SA rounding, header size and layout.
This was already partially fixed by avg.
Illumos ZFS issues:
3512 rounding discrepancy in sa_find_sizes()
3513 mismatch between SA header size and layout
MFC r246688 [1]:
Merge zfs_ioctl.c code that should have been merged together with ZFS v28.
Fixes several problems if working with read-only pools.
Changed code originaly introduced in onnv-gate 13061:
bda0decf867b
Contains changes up to illumos-gate 13700:
4bc0783f6064
PR: kern/175897 [1]
Suggested by: avg [1]
git-svn-id: svn://svn.freebsd.org/base/stable/8@247407
ccf9f872-aa2e-dd11-9fc8-
001c23d0bc1f