From 42f02ccb216fac75b3a4ba47c49c5682fbf6c8bb Mon Sep 17 00:00:00 2001 From: Suren Baghdasaryan Date: Tue, 9 Sep 2025 16:34:09 -0700 Subject: [PATCH] alloc_tag: avoid warnings when freeing non-compound "tail" pages When freeing "tail" pages of a non-compount high-order page, we properly subtract the allocation tag counters, however later when these pages are released, alloc_tag_sub() will issue warnings because tags for these pages are NULL. This issue was originally anticipated by Vlastimil in his review [1] and then recently reported by David. Prevent warnings by marking the tags empty. Link: https://lkml.kernel.org/r/20250909233409.1013367-4-surenb@google.com Link: https://lore.kernel.org/all/6db0f0c8-81cb-4d04-9560-ba73d63db4b8@suse.cz/ [1] Signed-off-by: Suren Baghdasaryan Suggested-by: David Wang <00107082@163.com> Acked-by: Shakeel Butt Cc: Brendan Jackman Cc: Johannes Weiner Cc: Kent Overstreet Cc: Michal Hocko Cc: Pasha Tatashin Cc: Sourav Panda Cc: Usama Arif Cc: Vlastimil Babka Cc: Zi Yan Signed-off-by: Andrew Morton --- mm/page_alloc.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 6ff9f17d5f4ec..cf38d499e0459 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5240,9 +5240,16 @@ static void ___free_pages(struct page *page, unsigned int order, __free_frozen_pages(page, order, fpi_flags); else if (!head) { pgalloc_tag_sub_pages(tag, (1 << order) - 1); - while (order-- > 0) + while (order-- > 0) { + /* + * The "tail" pages of this non-compound high-order + * page will have no code tags, so to avoid warnings + * mark them as empty. + */ + clear_page_tag_ref(page + (1 << order)); __free_frozen_pages(page + (1 << order), order, fpi_flags); + } } } -- 2.51.0