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.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Kiryl Shutsemau <[email protected]>
Reviewed-by: Muchun Song <[email protected]>
Acked-by: David Hildenbrand (Arm) <[email protected]>
Cc: Albert Ou <[email protected]>
Cc: Alexandre Ghiti <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Frank van der Linden <[email protected]>
Cc: Harry Yoo <[email protected]>
Cc: Huacai Chen <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Oscar Salvador <[email protected]>
Cc: Palmer Dabbelt <[email protected]>
Cc: Paul Walmsley <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Usama Arif <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: WANG Xuerui <[email protected]>
Cc: Zi Yan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

include/linux/page-flags.h

@@ -221,8 +221,6 @@ static __always_inline bool compound_info_has_mask(void)
 	return is_power_of_2(sizeof(struct page));
 }
 
-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);

mm/hugetlb_vmemmap.c

@@ -385,9 +385,6 @@ 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)
 {
@@ -419,10 +416,8 @@ 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;
 }
@@ -544,8 +539,6 @@ 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
@@ -581,10 +574,8 @@ 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;
 }
@@ -650,7 +641,6 @@ 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;
 		}