[026/156] mm/rmap: fix assumptions of THP size

Commit Message

Andrew Morton Oct. 16, 2020, 2:42 a.m. UTC

From: "Matthew Wilcox (Oracle)" <[e-mail]>
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/[e-mail]
Signed-off-by: Matthew Wilcox (Oracle) <[e-mail]>
Acked-by: Kirill A. Shutemov <[e-mail]>
Reviewed-by: SeongJae Park <[e-mail]>
Cc: Huang Ying <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/rmap.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

Patch

--- 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)))