+/*
+ * Order of operations is important: flush the pagevec when it's already
+ * full, not when adding the last page, to make sure that last page is
+ * not added to the LRU directly when passed to this function. Because
+ * mark_page_accessed() (called after this when writing) only activates
+ * pages that are on the LRU, linear writes in subpage chunks would see
+ * every PAGEVEC_SIZE page activated, which is unexpected.
+ */