[IA64] Use bitmaps for efficient context allocation/free

Corrects the very inefficent method of finding free context_ids in
get_mmu_context().  Instead of walking the task_list of all processes,
2 bitmaps are used to efficently store and lookup state, inuse and
needs flushing. The entire rid address space is now used before calling
wrap_mmu_context and global tlb flushing.

Special thanks to Ken and Rohit for their review and modifications in
using a bit flushmap.

Signed-off-by: Peter Keilty <peter.keilty@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
diff --git a/include/asm-ia64/tlbflush.h b/include/asm-ia64/tlbflush.h
index b65c627..a35b323 100644
--- a/include/asm-ia64/tlbflush.h
+++ b/include/asm-ia64/tlbflush.h
@@ -51,6 +51,7 @@
 	if (!mm)
 		return;
 
+	set_bit(mm->context, ia64_ctx.flushmap);
 	mm->context = 0;
 
 	if (atomic_read(&mm->mm_users) == 0)