[merged mm-hotfixes-stable] mm-page_alloc-mark-pages-freed-by-__free_pages_core-as-not-tagged.patch removed from -mm tree

[Andrew Morton <akpm@linux-foundation.org>]

The quilt patch titled
     Subject: mm/page_alloc: mark pages freed by __free_pages_core() as not tagged
has been removed from the -mm tree.  Its filename was
     mm-page_alloc-mark-pages-freed-by-__free_pages_core-as-not-tagged.patch

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

------------------------------------------------------
From: "Zenghui Yu (Huawei)" <zenghui.yu@linux.dev>
Subject: mm/page_alloc: mark pages freed by __free_pages_core() as not tagged
Date: Thu, 22 Oct 2026 20:27:52 +0800

Onlining hotplugged memory (e.g., a dev_dax device bound to kmem) with
CONFIG_MEM_ALLOC_PROFILING_DEBUG triggers:

  alloc_tag was not set
  WARNING: ./include/linux/alloc_tag.h:166 at __pgalloc_tag_sub+0x1fc/0x254
  Call trace:
   __pgalloc_tag_sub+0x1fc/0x254 (P)
   __free_pages_ok+0x14c/0x6ac
   __free_pages_core+0xa8/0x188
   generic_online_page+0x14/0x20
   online_pages+0x220/0x3b0
   memory_subsys_online+0xfc/0x198
   device_online+0x58/0xe0
   state_store+0xf0/0xf8

Pages entering the buddy through __free_pages_core() have never been
allocated, so their allocation tag references are NULL.  The free path,
__free_pages_prepare() -> pgalloc_tag_sub(), expects a valid tag or a
CODETAG_EMPTY mark and warns otherwise.  Paths feeding never-allocated
pages into the buddy are therefore expected to mark them with
clear_page_tag_ref() first, like init_cma_reserved_pageblock() and
free_reserved_pages() do; of __free_pages_core()'s callers only
memblock_free_pages() clears the tag ref itself, and the hotplug
onlining path was missed.

Since all __free_pages_core() callers free never-allocated pages, mark the
head page as not tagged in __free_pages_core() itself instead of relying on
each caller, and drop the now-redundant clearing from
memblock_free_pages().

Link: https://lore.kernel.org/20261022122752.74774-1-zenghui.yu@linux.dev
Fixes: dcfe378c81f7 ("lib: introduce support for page allocation tagging")
Signed-off-by: Zenghui Yu (Huawei) <zenghui.yu@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Brendan Jackman <brendan.jackman@linux.dev>
Cc: Zi Yan <ziy@nvidia.com>
Cc: <stable@vger.kernel.org>
---

 mm/mm_init.c    |    2 --
 mm/page_alloc.c |    3 +++
 2 files changed, 3 insertions(+), 2 deletions(-)

--- a/mm/mm_init.c~mm-page_alloc-mark-pages-freed-by-__free_pages_core-as-not-tagged
+++ a/mm/mm_init.c
@@ -2478,8 +2478,6 @@ void __init memblock_free_pages(unsigned
 		return;
 	}
 
-	/* pages were reserved and not allocated */
-	clear_page_tag_ref(page);
 	__free_pages_core(page, order, MEMINIT_EARLY);
 }
 
--- a/mm/page_alloc.c~mm-page_alloc-mark-pages-freed-by-__free_pages_core-as-not-tagged
+++ a/mm/page_alloc.c
@@ -1616,6 +1616,9 @@ void __meminit __free_pages_core(struct
 		atomic_long_add(nr_pages, &page_zone(page)->managed_pages);
 	}
 
+	/* pages were never allocated */
+	clear_page_tag_ref(page);
+
 	if (page_contains_unaccepted(page, order)) {
 		if (order == MAX_PAGE_ORDER && __free_unaccepted(page))
 			return;
_

Patches currently in -mm which might be from zenghui.yu@linux.dev are

selftests-mm-skip-collapse_compound_extreme-on-thp-allocation-failure.patch
mm-page_alloc-remove-unneeded-forward-declaration-of-__free_pages_ok.patch