[merged mm-stable] mm-debug-fix-parameter-passed-to-page_mapcount_is_type.patch removed from -mm tree

[merged mm-stable] mm-debug-fix-parameter-passed-to-page_mapcount_is_type.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm/debug: fix parameter passed to page_mapcount_is_type()
has been removed from the -mm tree.  Its filename was
     mm-debug-fix-parameter-passed-to-page_mapcount_is_type.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Gavin Shan <gshan@redhat.com>
Subject: mm/debug: fix parameter passed to page_mapcount_is_type()
Date: Fri, 21 Mar 2025 22:02:22 +1000

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 <gshan@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: gehao <gehao@kylinos.cn>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/debug.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/mm/debug.c~mm-debug-fix-parameter-passed-to-page_mapcount_is_type
+++ a/mm/debug.c
@@ -71,10 +71,12 @@ static void __dump_folio(struct folio *f
 		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);
_

Patches currently in -mm which might be from gshan@redhat.com are