NFS server and PF_FSTRANS

[behlendorf]

Related to #3225. @dweeezil can you please take a look at #3293, it implements the same fix for NFS server operations as we applied to the ZPL.

mutex_lock+0x1a/0x2c
zfs_znode_dmu_fini+0x10/0x1d [zfs]
zfs_zinactive+0x43/0x139 [zfs]
zfs_inactive+0x14a/0x186 [zfs]
zpl_evict_inode+0x37/0x46 [zfs]
evict+0x9a/0x14e
dispose_list+0x35/0x3f
prune_icache_sb+0x2ca/0x2d9
prune_super+0xde/0x14f
shrink_slab+0x1a3/0x266
do_try_to_free_pages+0x32c/0x4c9
try_to_free_pages+0xa9/0xe9
__alloc_pages_nodemask+0x4ef/0x799
kmem_getpages+0x4b/0x107
fallback_alloc+0x15c/0x1f6
kmem_cache_alloc+0x7f/0xf0
spl_kmem_cache_alloc+0xa9/0x7a7 [spl]
dbuf_fill_done+0x8d/0x8d [zfs]
arc_get_data_buf+0x2c3/0x3d4 [zfs]
arc_read+0x536/0x8da [zfs]
zio_null+0x58/0x5d [zfs]
dbuf_read+0x425/0x5bf [zfs]
dnode_hold_impl+0x12f/0x416 [zfs]
dmu_bonus_hold+0x1c/0x171 [zfs]
mutex_lock+0xd/0x2c
zfs_zget+0x65/0x2a6 [zfs]
tcp_recvmsg+0x73c/0x82b
mutex_lock+0xd/0x2c
fh_compose+0x335/0x335 [nfsd]
zfs_vget+0x223/0x2ee [zfs]
zpl_fh_to_dentry+0x2f/0x51 [zfs]
exportfs_decode_fh+0x5a/0x226
fh_verify+0x283/0x485 [nfsd]
svcauth_unix_set_client+0x21a/0x28f [sunrpc]
nfsd3_proc_getattr+0x56/0x8c [nfsd]
nfsd_dispatch+0xd9/0x1bb [nfsd]
svc_process_common+0x2d0/0x4ca [sunrpc]
try_to_wake_up+0x191/0x191
nfsd_svc+0x17f/0x17f [nfsd]
svc_process+0x10d/0x12c [sunrpc]
nfsd+0xe3/0x127 [nfsd]
kthread+0x7a/0x82

[behlendorf]

This was address by 7fad629.