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mm/page_alloc: mark pages freed by __free_pages_core() as not tagged

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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: dcfe378c81 ("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>
This commit is contained in:
Zenghui Yu (Huawei) 2026-10-22 20:27:52 +08:00 committed by Andrew Morton
parent 92daa8652f
commit b6732c6d43
2 changed files with 3 additions and 2 deletions
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2
mm/mm_init.c
View File

@ -2478,8 +2478,6 @@ void __init memblock_free_pages(unsigned long pfn, unsigned int order)
return;
}
/* pages were reserved and not allocated */
clear_page_tag_ref(page);
__free_pages_core(page, order, MEMINIT_EARLY);
}

3
mm/page_alloc.c
View File

@ -1616,6 +1616,9 @@ void __meminit __free_pages_core(struct page *page, unsigned int order,
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;