mm/memory.c: share the i_mmap_rwsem

The unmap_mapping_range family of functions do the unmapping of user pages
(ultimately via zap_page_range_single) without touching the actual
interval tree, thus share the lock.

Signed-off-by: Davidlohr Bueso <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Acked-by: Hugh Dickins <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Peter Zijlstra (Intel) <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Srikar Dronamraju <[email protected]>
Acked-by: Mel Gorman <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: Davidlohr Bueso

mm/memory.c

@@ -2377,12 +2377,12 @@ void unmap_mapping_range(struct address_space *mapping,
 		details.last_index = ULONG_MAX;
 
 
-	i_mmap_lock_write(mapping);
+	i_mmap_lock_read(mapping);
 	if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap)))
 		unmap_mapping_range_tree(&mapping->i_mmap, &details);
 	if (unlikely(!list_empty(&mapping->i_mmap_nonlinear)))
 		unmap_mapping_range_list(&mapping->i_mmap_nonlinear, &details);
-	i_mmap_unlock_write(mapping);
+	i_mmap_unlock_read(mapping);
 }
 EXPORT_SYMBOL(unmap_mapping_range);