behind cache for PTE table allocations in the
mm struct.

This logic triggers only on allocations.  For example, we don't try to
keep track of free'd up page table blocks in the style that the s390 port
does.

There were only two slightly annoying aspects to this change:

1) Changing pgtable_t to be a "pte_t *".  There's all of this special
   logic in the TLB free paths that needed adjustments, as did the
   PMD populate interfaces.

2) init_new_context() needs to zap the pointer, since the mm struct
   just gets copied from the parent on fork.

Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
*éÒM–Tx