mm/vmacache: inline vmacache_valid_mm()

This function incurs in very hot paths and merely does a few loads for
validity check.  Lets inline it, such that we can save the function call
overhead.

(akpm: this is cosmetic - the compiler already inlines vmacache_valid_mm())
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/vmacache.c

@@ -52,7 +52,7 @@ void vmacache_flush_all(struct mm_struct *mm)
  * Also handle the case where a kernel thread has adopted this mm via use_mm().
  * That kernel thread's vmacache is not applicable to this mm.
  */
-static bool vmacache_valid_mm(struct mm_struct *mm)
+static inline bool vmacache_valid_mm(struct mm_struct *mm)
 {
 	return current->mm == mm && !(current->flags & PF_KTHREAD);
 }