On Sat, 23 Mar 2024 06:04:54 +0900 Soma Nakata <soma.nakata01@xxxxxxxxx> wrote: > Functions such as __filemap_get_folio() check the truncation of > folios based on the mapping field. Therefore setting this field to NULL > earlier prevents unnecessary operations on already removed folios. > > ... > > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -139,11 +139,12 @@ static void page_cache_delete(struct address_space *mapping, > > VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); > > + folio->mapping = NULL; > + /* Leave page->index set: truncation lookup relies upon it */ > + > xas_store(&xas, shadow); > xas_init_marks(&xas); > > - folio->mapping = NULL; > - /* Leave page->index set: truncation lookup relies upon it */ > mapping->nrpages -= nr; > } Seems at least harmless, but I wonder if it can really make any difference. Don't readers of folio->mapping lock the folio first?
