On 07.07.25 16:23, Pankaj Raghav (Samsung) wrote:
From: Pankaj Raghav <p.raghav@xxxxxxxxxxx>
Add largest_zero_folio() routine so that huge_zero_folio can be
used without the need to pass any mm struct. This will return ZERO_PAGE
folio if CONFIG_STATIC_PMD_ZERO_PAGE is disabled or if we failed to
allocate a PMD page from memblock.
This routine can also be called even if THP is disabled.
Signed-off-by: Pankaj Raghav <p.raghav@xxxxxxxxxxx>
---
include/linux/mm.h | 28 ++++++++++++++++++++++++++--
1 file changed, 26 insertions(+), 2 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 428fe6d36b3c..d5543cf7b8e9 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -4018,17 +4018,41 @@ static inline bool vma_is_special_huge(const struct vm_area_struct *vma)
#endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */
+extern struct folio *huge_zero_folio;
+extern unsigned long huge_zero_pfn;
No need for "extern".
+
#ifdef CONFIG_STATIC_PMD_ZERO_PAGE
extern void __init static_pmd_zero_init(void);
+
+/*
+ * largest_zero_folio - Get the largest zero size folio available
+ *
+ * This function will return a PMD sized zero folio if CONFIG_STATIC_PMD_ZERO_PAGE
+ * is enabled. Otherwise, a ZERO_PAGE folio is returned.
+ *
+ * Deduce the size of the folio with folio_size instead of assuming the
+ * folio size.
+ */
+static inline struct folio *largest_zero_folio(void)
+{
+ if(!huge_zero_folio)
Nit: if (!huge_zero_folio), but see below
I assume this check is only in place to handle whether static allocation
failed, correct?
+ return page_folio(ZERO_PAGE(0));
+
+ return READ_ONCE(huge_zero_folio);
READ_ONCE should not be required if it cannot get freed.
+}
+
#else
static inline void __init static_pmd_zero_init(void)
{
return;
}
+
+static inline struct folio *largest_zero_folio(void)
+{
+ return page_folio(ZERO_PAGE(0));
+}
#endif
Could we do:
static inline struct folio *largest_zero_folio(void)
{
if (IS_ENABLED(CONFIG_STATIC_PMD_ZERO_PAGE) &&
likely(huge_zero_folio))
return huge_zero_folio;
return page_folio(ZERO_PAGE(0));
}
--
Cheers,
David / dhildenb
