mm: avoid endless recursion in dump_page()

dump_page() uses page_mapcount() to get mapcount of the page. page_mapcount() has VM_BUG_ON_PAGE(PageSlab(page)) as mapcount doesn't make sense for slab pages and the field in struct page used for other information. It leads to recursion if dump_page() called for slub page and DEBUG_VM is enabled: dump_page() -> page_mapcount() -> VM_BUG_ON_PAGE() -> dump_page -> ... Let's avoid calling page_mapcount() for slab pages in dump_page(). Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Kirill A. Shutemov <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
cluon · Sep 19, 2016 · 4d35427 · 4d35427
1 parent 982785c
commit 4d35427
Showing 1 changed file with 4 additions and 2 deletions.
diff --git a/mm/debug.c b/mm/debug.c
@@ -42,9 +42,11 @@ const struct trace_print_flags vmaflag_names[] = {
 
 void __dump_page(struct page *page, const char *reason)
 {
+	int mapcount = PageSlab(page) ? 0 : page_mapcount(page);
+
 	pr_emerg("page:%p count:%d mapcount:%d mapping:%p index:%#lx",
-		  page, page_ref_count(page), page_mapcount(page),
-		  page->mapping, page->index);
+		  page, page_ref_count(page), mapcount,
+		  page->mapping, page_to_pgoff(page));
 	if (PageCompound(page))
 		pr_cont(" compound_mapcount: %d", compound_mapcount(page));
 	pr_cont("\n");