The patch titled
Subject: mm: clarify folio_set_compound_order() zero support
has been added to the -mm mm-unstable branch. Its filename is
mm-add-folio-dtor-and-order-setter-functions-fix.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-add-folio-dtor-and-order-setter-functions-fix.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>
Subject: mm: clarify folio_set_compound_order() zero support
Date: Wed, 7 Dec 2022 14:37:31 -0800
Document hugetlb's use of a zero compound order so support for zero
orders is not removed from folio_set_compound_order().
Link: https://lkml.kernel.org/r/20221207223731.32784-1-sidhartha.kumar@xxxxxxxxxx
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>
Suggested-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Suggested-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/include/linux/mm.h~mm-add-folio-dtor-and-order-setter-functions-fix
+++ a/include/linux/mm.h
@@ -1019,9 +1019,16 @@ static inline void set_compound_order(st
#endif
}
+/*
+ * folio_set_compound_order is generally passed a non-zero order to
+ * initialize a large folio. However, hugetlb code abuses this by
+ * passing in zero when 'dissolving' a large folio.
+ */
static inline void folio_set_compound_order(struct folio *folio,
unsigned int order)
{
+ VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
+
folio->_folio_order = order;
#ifdef CONFIG_64BIT
folio->_folio_nr_pages = order ? 1U << order : 0;
_
Patches currently in -mm which might be from sidhartha.kumar@xxxxxxxxxx are
mm-add-folio-dtor-and-order-setter-functions.patch
mm-add-folio-dtor-and-order-setter-functions-fix.patch
mm-hugetlb-convert-destroy_compound_gigantic_page-to-folios.patch
mm-hugetlb-convert-dissolve_free_huge_page-to-folios.patch
mm-hugetlb-convert-remove_hugetlb_page-to-folios.patch
mm-hugetlb-convert-update_and_free_page-to-folios.patch
mm-hugetlb-convert-add_hugetlb_page-to-folios-and-add-hugetlb_cma_folio.patch
mm-hugetlb-convert-enqueue_huge_page-to-folios.patch
mm-hugetlb-convert-free_gigantic_page-to-folios.patch
mm-hugetlb-convert-hugetlb-prep-functions-to-folios.patch
mm-hugetlb-change-hugetlb-allocation-functions-to-return-a-folio.patch
mm-hugetlb-change-hugetlb-allocation-functions-to-return-a-folio-fix.patch
