x86/mm: Unify remote INVLPG code

There are currently three paths through the remote flush code:

1. full invalidation
2. single page invalidation using invlpg
3. ranged invalidation using invlpg

This takes 2 and 3 and combines them in to a single path by
making the single-page one just be the start and end be start
plus a single page.  This makes placement of our tracepoint easier.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: http://lkml.kernel.org/r/20140731154058.E0F90408@viggo.jf.intel.com
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/mm/tlb.c

@@ -102,13 +102,13 @@ static void flush_tlb_func(void *info)
 
 	if (f->flush_mm != this_cpu_read(cpu_tlbstate.active_mm))
 		return;
+	if (!f->flush_end)
+		f->flush_end = f->flush_start + PAGE_SIZE;
 
 	count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
 	if (this_cpu_read(cpu_tlbstate.state) == TLBSTATE_OK) {
 		if (f->flush_end == TLB_FLUSH_ALL)
 			local_flush_tlb();
-		else if (!f->flush_end)
-			__flush_tlb_single(f->flush_start);
 		else {
 			unsigned long addr;
 			addr = f->flush_start;