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mm/hugetlb: copy the CMA flag when demoting

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Since commit d2d7867140 ("mm/hugetlb: enable bootmem allocation from CMA
areas"), a flag is used to mark hugetlb folios as allocated from CMA. 
This flag is also used to decide if it should be freed to CMA.

However, the flag isn't copied to the smaller folios when a hugetlb folio
is broken up for demotion, which would cause it to be freed incorrectly.

Fix this by copying the flag to the smaller order hugetlb pages created
from the original one.

Link: https://lkml.kernel.org/r/20250501044325.20365-1-fvdl@google.com
Fixes: d2d7867140 ("mm/hugetlb: enable bootmem allocation from CMA areas")
Signed-off-by: Frank van der Linden <fvdl@google.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Jane Chu <Jane.Chu@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Frank van der Linden
2025-05-01 04:43:24 +00:00
committed by Andrew Morton
parent 9a9794a81a
commit dac2a4f663
1 changed files with 6 additions and 0 deletions
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mm/hugetlb.c
+6
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@@ -4034,10 +4034,13 @@ static long demote_free_hugetlb_folios(struct hstate *src, struct hstate *dst,
list_for_each_entry_safe(folio, next, src_list, lru) {
int i;
bool cma;
if (folio_test_hugetlb_vmemmap_optimized(folio))
continue;
cma = folio_test_hugetlb_cma(folio);
list_del(&folio->lru);
split_page_owner(&folio->page, huge_page_order(src), huge_page_order(dst));
@@ -4053,6 +4056,9 @@ static long demote_free_hugetlb_folios(struct hstate *src, struct hstate *dst,
new_folio->mapping = NULL;
init_new_hugetlb_folio(dst, new_folio);
/* Copy the CMA flag so that it is freed correctly */
if (cma)
folio_set_hugetlb_cma(new_folio);
list_add(&new_folio->lru, &dst_list);
}
}