From 4d35427ad7641cba08ea0deffae1a78147ad41c0 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Mon, 19 Sep 2016 14:44:07 -0700 Subject: [PATCH] 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/20160908082137.131076-1-kirill.shutemov@linux.intel.com Signed-off-by: Kirill A. Shutemov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/debug.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/mm/debug.c b/mm/debug.c index 8865bfb41b0b..74c7cae4f683 100644 --- 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");