[PATCH v1 17/18] mm/debug: print only page mapcount (excluding folio entire mapcount) in __dump_folio()

[David Hildenbrand <david@redhat.com>]

Let's simplify and only print the page mapcount: we already print the
large folio mapcount and the entire folio mapcount for large folios
separately; that should be sufficient to figure out what's happening.

While at it, print the page mapcount also if it had an underflow,
filtering out only typed pages.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 mm/debug.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/mm/debug.c b/mm/debug.c
index d064db42af54..69e524c3e601 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -55,15 +55,10 @@ 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) + 1;
+	int mapcount = atomic_read(&page->_mapcount);
 	char *type = "";
 
-	/* Open-code page_mapcount() to avoid looking up a stale folio */
-	if (mapcount < 0)
-		mapcount = 0;
-	if (folio_test_large(folio))
-		mapcount += folio_entire_mapcount(folio);
-
+	mapcount = page_type_has_type(mapcount) ? 0 : mapcount + 1;
 	pr_warn("page: refcount:%d mapcount:%d mapping:%p index:%#lx pfn:%#lx\n",
 			folio_ref_count(folio), mapcount, mapping,
 			folio->index + idx, pfn);
-- 
2.44.0