mm: export mmu notifier invalidates

We at SGI have a need to address some very high physical address ranges
with our GRU (global reference unit), sometimes across partitioned
machine boundaries and sometimes with larger addresses than the cpu
supports.  We do this with the aid of our own 'extended vma' module
which mimics the vma.  When something (either unmap or exit) frees an
'extended vma' we use the mmu notifiers to clean them up.

We had been able to mimic the functions
__mmu_notifier_invalidate_range_start() and
__mmu_notifier_invalidate_range_end() by locking the per-mm lock and
walking the per-mm notifier list.  But with the change to a global srcu
lock (static in mmu_notifier.c) we can no longer do that.  Our module has
no access to that lock.

So we request that these two functions be exported.

Signed-off-by: Cliff Wickman <[email protected]>
Acked-by: Robin Holt <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/mmu_notifier.c

@@ -172,6 +172,7 @@ void __mmu_notifier_invalidate_range_start(struct mm_struct *mm,
 	}
 	srcu_read_unlock(&srcu, id);
 }
+EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_start);
 
 void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
 				  unsigned long start, unsigned long end)
@@ -187,6 +188,7 @@ void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
 	}
 	srcu_read_unlock(&srcu, id);
 }
+EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_end);
 
 static int do_mmu_notifier_register(struct mmu_notifier *mn,
 				    struct mm_struct *mm,