mempolicy: don't call mpol_set_nodemask() when no_context

mempolicy: don't call mpol_set_nodemask() when no_context

No need to call mpol_set_nodemask() when we have no context for the
mempolicy.  This can occur when we're parsing a tmpfs 'mpol' mount option.
 Just save the raw nodemask in the mempolicy's w.user_nodemask member for
use when a tmpfs/shmem file is created.  mpol_shared_policy_init() will
"contextualize" the policy for the new file based on the creating task's
context.

Signed-off-by: Lee Schermerhorn <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Ravikiran Thirumalai <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: David Rientjes <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>