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alloc_tag: avoid warnings when freeing non-compound "tail" pages

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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: Suren Baghdasaryan <surenb@google.com>
Suggested-by: David Wang <00107082@163.com>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Usama 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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Suren Baghdasaryan
2025-09-15 14:27:56 -07:00
committed by Andrew Morton
parent 9e8a0bbb12
commit 7ffc923e25
1 changed files with 8 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files
mm/page_alloc.c
+8 -1
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@@ -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);
}
}
}