mm: fix comments for invalidate_inode_pages2()

invalidate_inode_pages2() returns -EBUSY *NOT* -EIO if any pages could not be
invalidated.
Signed-off-by: Peng Tao <bergwolf@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

mm/truncate.c

@@ -490,7 +490,7 @@ EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
  * Any pages which are found to be mapped into pagetables are unmapped prior to
  * invalidation.
  *
- * Returns -EIO if any pages could not be invalidated.
+ * Returns -EBUSY if any pages could not be invalidated.
  */
 int invalidate_inode_pages2(struct address_space *mapping)
 {