On Mon, Feb 14, 2022 at 08:00:11PM +0000, Matthew Wilcox (Oracle) wrote: > folio_mapped() is expensive because it has to check each page's mapcount > field. A cheaper check is whether there are any extra references to > the page, other than the one we own and the ones held by the page cache. > The call to remove_mapping() will fail in any case if it cannot freeze > the refcount, but failing here avoids cycling the i_pages spinlock. This is the patch that's causing ltp's readahead02 test to break. Haven't dug into why yet, but it happens without large folios, so I got something wrong. > diff --git a/mm/truncate.c b/mm/truncate.c > index b73c30c95cd0..d67fa8871b75 100644 > --- a/mm/truncate.c > +++ b/mm/truncate.c > @@ -287,7 +287,7 @@ int invalidate_inode_page(struct page *page) > return 0; > if (folio_test_dirty(folio) || folio_test_writeback(folio)) > return 0; > - if (page_mapped(page)) > + if (folio_ref_count(folio) > folio_nr_pages(folio) + 1) > return 0; > if (folio_has_private(folio) && !filemap_release_folio(folio, 0)) > return 0; > -- > 2.34.1 >
