Re: [PATCH v1 04/29] mm/page_alloc: let page freeing clear any set page type
From: Lorenzo Stoakes <hidden>
Date: 2025-06-30 15:34:31
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On Mon, Jun 30, 2025 at 02:59:45PM +0200, David Hildenbrand wrote:
Currently, any user of page types must clear that type before freeing a page back to the buddy, otherwise we'll run into mapcount related sanity checks (because the page type currently overlays the page mapcount). Let's allow for not clearing the page type by page type users by letting the buddy handle it instead. We'll focus on having a page type set on the first page of a larger allocation only. With this change, we can reliably identify typed folios even though they might be in the process of getting freed, which will come in handy in migration code (at least in the transition phase). In the future we might want to warn on some page types. Instead of having an "allow list", let's rather wait until we know about once that should go on such a "disallow list".
Is the idea here to get this to show up on folio dumps or?
quoted hunk ↗ jump to hunk
Reviewed-by: Zi Yan <ziy@nvidia.com> Acked-by: Harry Yoo <redacted> Signed-off-by: David Hildenbrand <redacted> --- mm/page_alloc.c | 3 +++ 1 file changed, 3 insertions(+)diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 858bc17653af9..44e56d31cfeb1 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c@@ -1380,6 +1380,9 @@ __always_inline bool free_pages_prepare(struct page *page, mod_mthp_stat(order, MTHP_STAT_NR_ANON, -1); page->mapping = NULL; } + if (unlikely(page_has_type(page))) + page->page_type = UINT_MAX;
Feels like this could do with a comment!
+
if (is_check_pages_enabled()) {
if (free_page_is_bad(page))
bad++;
--
2.49.0