linux-kernel - [PATCHv2 12/14] mm/hugetlb: Remove hugetlb_optimize_vmemmap

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Message-ID: <20251218150949.721480-13-kas@kernel.org>
Date: Thu, 18 Dec 2025 15:09:43 +0000
From: Kiryl Shutsemau <kas@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>,
	Muchun Song <muchun.song@...ux.dev>,
	David Hildenbrand <david@...nel.org>,
	Matthew Wilcox <willy@...radead.org>,
	Usama Arif <usamaarif642@...il.com>,
	Frank van der Linden <fvdl@...gle.com>
Cc: Oscar Salvador <osalvador@...e.de>,
	Mike Rapoport <rppt@...nel.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Zi Yan <ziy@...dia.com>,
	Baoquan He <bhe@...hat.com>,
	Michal Hocko <mhocko@...e.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Jonathan Corbet <corbet@....net>,
	kernel-team@...a.com,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org,
	Kiryl Shutsemau <kas@...nel.org>
Subject: [PATCHv2 12/14] mm/hugetlb: Remove hugetlb_optimize_vmemmap_key static key

The hugetlb_optimize_vmemmap_key static key was used to guard fake head
detection in compound_head() and related functions. It allowed skipping
the fake head checks entirely when HVO was not in use.

With fake heads eliminated and the detection code removed, the static
key serves no purpose. Remove its definition and all increment/decrement
calls.

Signed-off-by: Kiryl Shutsemau <kas@...nel.org>
---
 include/linux/page-flags.h |  2 --
 mm/hugetlb_vmemmap.c       | 14 ++------------
 2 files changed, 2 insertions(+), 14 deletions(-)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 9d89beed9df6..2255e7e6759c 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -198,8 +198,6 @@ enum pageflags {
 
 #ifndef __GENERATING_BOUNDS_H
 
-DECLARE_STATIC_KEY_FALSE(hugetlb_optimize_vmemmap_key);
-
 static __always_inline unsigned long _compound_head(const struct page *page)
 {
 	unsigned long info = READ_ONCE(page->compound_info);
diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index cc0fcf847810..f68ed7ebf873 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -399,9 +399,6 @@ static int vmemmap_remap_alloc(unsigned long start, unsigned long end,
 	return vmemmap_remap_range(start, end, &walk);
 }
 
-DEFINE_STATIC_KEY_FALSE(hugetlb_optimize_vmemmap_key);
-EXPORT_SYMBOL(hugetlb_optimize_vmemmap_key);
-
 static bool vmemmap_optimize_enabled = IS_ENABLED(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON);
 static int __init hugetlb_vmemmap_optimize_param(char *buf)
 {
@@ -431,10 +428,8 @@ static int __hugetlb_vmemmap_restore_folio(const struct hstate *h,
 	 * discarded vmemmap pages must be allocated and remapping.
 	 */
 	ret = vmemmap_remap_alloc(vmemmap_start, vmemmap_end, flags);
-	if (!ret) {
+	if (!ret)
 		folio_clear_hugetlb_vmemmap_optimized(folio);
-		static_branch_dec(&hugetlb_optimize_vmemmap_key);
-	}
 
 	return ret;
 }
@@ -566,8 +561,6 @@ static int __hugetlb_vmemmap_optimize_folio(const struct hstate *h,
 	if (!vmemmap_tail)
 		return -ENOMEM;
 
-	static_branch_inc(&hugetlb_optimize_vmemmap_key);
-
 	/*
 	 * Very Subtle
 	 * If VMEMMAP_REMAP_NO_TLB_FLUSH is set, TLB flushing is not performed
@@ -604,10 +597,8 @@ static int __hugetlb_vmemmap_optimize_folio(const struct hstate *h,
 				 vmemmap_head, vmemmap_tail,
 				 vmemmap_pages, flags);
 out:
-	if (ret) {
-		static_branch_dec(&hugetlb_optimize_vmemmap_key);
+	if (ret)
 		folio_clear_hugetlb_vmemmap_optimized(folio);
-	}
 
 	return ret;
 }
@@ -673,7 +664,6 @@ static void __hugetlb_vmemmap_optimize_folios(struct hstate *h,
 			register_page_bootmem_memmap(pfn_to_section_nr(spfn),
 					&folio->page,
 					HUGETLB_VMEMMAP_RESERVE_SIZE);
-			static_branch_inc(&hugetlb_optimize_vmemmap_key);
 			continue;
 		}
 
-- 
2.51.2