From: Gavin Shan Date: Fri, 21 Mar 2025 12:02:22 +0000 (+1000) Subject: mm/debug: fix parameter passed to page_mapcount_is_type() X-Git-Tag: v6.16-rc1~92^2~220 X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=79049bb48a76333646d076e29d4f99fedefdaf0d;p=linux-block.git mm/debug: fix parameter passed to page_mapcount_is_type() As the comments of page_mapcount_is_type() indicate, the parameter passed to the function should be one more than page->_mapcount. However, page->_mapcount is passed to the function by commit 4ffca5a96678 ("mm: support only one page_type per page") where page_type_has_type() is replaced by page_mapcount_is_type(), but the parameter isn't adjusted. Fix the parameter for page_mapcount_is_type() to be (page->__mapcount + 1). Note that the issue doesn't cause any visible impacts due to the safety gap introduced by PGTY_mapcount_underflow limit. [akpm@linux-foundation.org: simplify __dump_folio(), per David] Link: https://lkml.kernel.org/r/20250321120222.1456770-3-gshan@redhat.com Fixes: 4ffca5a96678 ("mm: support only one page_type per page") Signed-off-by: Gavin Shan Acked-by: David Hildenbrand Acked-by: Vlastimil Babka Cc: gehao Cc: Matthew Wilcox (Oracle) Cc: Miaohe Lin Signed-off-by: Andrew Morton --- diff --git a/mm/debug.c b/mm/debug.c index db83e381a8ae..907382257062 100644 --- a/mm/debug.c +++ b/mm/debug.c @@ -71,10 +71,12 @@ static void __dump_folio(struct folio *folio, struct page *page, unsigned long pfn, unsigned long idx) { struct address_space *mapping = folio_mapping(folio); - int mapcount = atomic_read(&page->_mapcount); + int mapcount = atomic_read(&page->_mapcount) + 1; char *type = ""; - mapcount = page_mapcount_is_type(mapcount) ? 0 : mapcount + 1; + if (page_mapcount_is_type(mapcount)) + mapcount = 0; + pr_warn("page: refcount:%d mapcount:%d mapping:%p index:%#lx pfn:%#lx\n", folio_ref_count(folio), mapcount, mapping, folio->index + idx, pfn);