Commit 7ffc923e authored by Suren Baghdasaryan's avatar Suren Baghdasaryan Committed by Andrew Morton
Browse files

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/20250915212756.3998938-4-surenb@google.com
Link: https://lore.kernel.org/all/6db0f0c8-81cb-4d04-9560-ba73d63db4b8@suse.cz/

 [1]
Signed-off-by: default avatarSuren Baghdasaryan <surenb@google.com>
Suggested-by: default avatarDavid Wang <00107082@163.com>
Acked-by: default avatarShakeel Butt <shakeel.butt@linux.dev>
Acked-by: default avatarUsama Arif <usamaarif642@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Sourav Panda <souravpanda@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 9e8a0bbb

mm/page_alloc.c

+8 −1
Original line number Diff line number Diff line
@@ -5240,11 +5240,18 @@ 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);

		}

	}

}



/**

 * __free_pages - Free pages allocated with alloc_pages().