From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> Subject: mm/rmap: fix assumptions of THP size Ask the page what size it is instead of assuming it's PMD size. Do this for anon pages as well as file pages for when someone decides to support that. Leave the assumption alone for pages which are PMD mapped; we don't currently grow THPs beyond PMD size, so we don't need to change this code yet. Link: https://lkml.kernel.org/r/20200908195539.25896-9-willy@xxxxxxxxxxxxx Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Reviewed-by: SeongJae Park <sjpark@xxxxxxxxx> Cc: Huang Ying <ying.huang@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/rmap.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) --- a/mm/rmap.c~mm-rmap-fix-assumptions-of-thp-size +++ a/mm/rmap.c @@ -1205,7 +1205,7 @@ void page_add_file_rmap(struct page *pag VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page); lock_page_memcg(page); if (compound && PageTransHuge(page)) { - for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) { + for (i = 0, nr = 0; i < thp_nr_pages(page); i++) { if (atomic_inc_and_test(&page[i]._mapcount)) nr++; } @@ -1246,7 +1246,7 @@ static void page_remove_file_rmap(struct /* page still mapped by someone else? */ if (compound && PageTransHuge(page)) { - for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) { + for (i = 0, nr = 0; i < thp_nr_pages(page); i++) { if (atomic_add_negative(-1, &page[i]._mapcount)) nr++; } @@ -1293,7 +1293,7 @@ static void page_remove_anon_compound_rm * Subpages can be mapped with PTEs too. Check how many of * them are still mapped. */ - for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) { + for (i = 0, nr = 0; i < thp_nr_pages(page); i++) { if (atomic_add_negative(-1, &page[i]._mapcount)) nr++; } @@ -1303,10 +1303,10 @@ static void page_remove_anon_compound_rm * page of the compound page is unmapped, but at least one * small page is still mapped. */ - if (nr && nr < HPAGE_PMD_NR) + if (nr && nr < thp_nr_pages(page)) deferred_split_huge_page(page); } else { - nr = HPAGE_PMD_NR; + nr = thp_nr_pages(page); } if (unlikely(PageMlocked(page))) _
