This patch optimizes tlb flushing in a couple of ways to reduce the number
of system calls made to the host in order to update an address space.

Operations are collected, and adjacent ones which can be merged, are.  This
includes consecutive munmaps, mprotects with the same permissions, and mmaps
with the same backing file and permissions and linear in the file.

Second, the munmaps that always preceded mmaps are now done instead of mmap if
necessary.
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>