linux-kernel - [PATCH 4/5] mm: add mm_get_static_huge_zero

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Message-ID: <20250612105100.59144-5-p.raghav@samsung.com>
Date: Thu, 12 Jun 2025 12:50:59 +0200
From: Pankaj Raghav <p.raghav@...sung.com>
To: Suren Baghdasaryan <surenb@...gle.com>,
	Ryan Roberts <ryan.roberts@....com>,
	Mike Rapoport <rppt@...nel.org>,
	Michal Hocko <mhocko@...e.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Nico Pache <npache@...hat.com>,
	Dev Jain <dev.jain@....com>,
	Baolin Wang <baolin.wang@...ux.alibaba.com>,
	Borislav Petkov <bp@...en8.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Zi Yan <ziy@...dia.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	David Hildenbrand <david@...hat.com>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Liam R . Howlett" <Liam.Howlett@...cle.com>,
	Jens Axboe <axboe@...nel.dk>
Cc: linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	willy@...radead.org,
	x86@...nel.org,
	linux-block@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	"Darrick J . Wong" <djwong@...nel.org>,
	mcgrof@...nel.org,
	gost.dev@...sung.com,
	kernel@...kajraghav.com,
	hch@....de,
	Pankaj Raghav <p.raghav@...sung.com>
Subject: [PATCH 4/5] mm: add mm_get_static_huge_zero_folio() routine

Add mm_get_static_huge_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.

This routine can also be called even if THP is disabled.

Signed-off-by: Pankaj Raghav <p.raghav@...sung.com>
---
 include/linux/mm.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index b20d60d68b3c..c8805480ff21 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -4021,6 +4021,22 @@ static inline bool vma_is_special_huge(const struct vm_area_struct *vma)
 extern struct folio *huge_zero_folio;
 extern unsigned long huge_zero_pfn;
 
+/*
+ * mm_get_static_huge_zero_folio - Get a PMD sized zero folio
+ *
+ * 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 *mm_get_static_huge_zero_folio(void)
+{
+	if(IS_ENABLED(CONFIG_STATIC_PMD_ZERO_PAGE))
+		return READ_ONCE(huge_zero_folio);
+	return page_folio(ZERO_PAGE(0));
+}
+
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 static inline bool is_huge_zero_folio(const struct folio *folio)
 {
-- 
2.49.0