This patch fixes two problems:

1. A system can panic with a kernel memory fault in 
   _OtsMove if threads are performing AdvFS directIO 
   read operations.

2. Fix NFS ability to grow a file using the truncate call.
   This problem usually appears as a kernel memory fault with the
   panicing thread having the following stack trace segment:

   [...]
   5 _OtsZero
   6 fs_setattr
   [...]

 

For Problem #1:
   4 panic                src/kernel/bsd/subr_prf.c : 1378
   5 trap                 src/kernel/arch/alpha/trap.c : 2285
   6 _XentMM              src/kernel/arch/alpha/locore.s : 2219
   7 _OtsMove             src/kernel/arch/alpha/ots_move_alpha.s : 1592
   8 uiomove              src/kernel/bsd/kern_subr.c : 196
   9 uiomove_frag         src/kernel/msfs/fs/fs_read_write.c : 5480
  10 fs_read              src/kernel/msfs/fs/fs_read_write.c : 4645
  11 msfs_read            src/kernel/msfs/osf/msfs_vnops.c : 3446
  12 vn_pread             src/kernel/vfs/vfs_vnops.c : 1149
  13 msfs_strategy        src/kernel/msfs/osf/msfs_vnops.c : 6302
  14 aio_rw               src/kernel/bsd/kern_aio.c : 3225
  15 syscall              src/kernel/arch/alpha/syscall_trap.c : 725
  16 _Xsyscall            src/kernel/arch/alpha/locore.s : 1864

