mm/mglru: remove CONFIG_TRANSPARENT_HUGEPAGE

Improve code readability by removing CONFIG_TRANSPARENT_HUGEPAGE,
since the compiler should be able to automatically optimize out the
code that promotes THPs during page table walks.

No functional changes.

Link: https://lkml.kernel.org/r/20231227141205.2200125-6-kinseyho@google.comSigned-off-by: Kinsey Ho <kinseyho@google.com>
Co-developed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Tested-by: Donet Tom <donettom@linux.vnet.ibm.com>
Acked-by: Yu Zhao <yuzhao@google.com>
Cc: kernel test robot <lkp@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/vmscan.c

@@ -3273,7 +3273,6 @@ static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned
 	return pfn;
 }
 
-#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG)
 static unsigned long get_pmd_pfn(pmd_t pmd, struct vm_area_struct *vma, unsigned long addr)
 {
 	unsigned long pfn = pmd_pfn(pmd);
@@ -3291,7 +3290,6 @@ static unsigned long get_pmd_pfn(pmd_t pmd, struct vm_area_struct *vma, unsigned
 
 	return pfn;
 }
-#endif
 
 static struct folio *get_pfn_folio(unsigned long pfn, struct mem_cgroup *memcg,
 				   struct pglist_data *pgdat, bool can_swap)
@@ -3394,7 +3392,6 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end,
 	return suitable_to_scan(total, young);
 }
 
-#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG)
 static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm_area_struct *vma,
 				  struct mm_walk *args, unsigned long *bitmap, unsigned long *first)
 {
@@ -3472,12 +3469,6 @@ static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm_area
 done:
 	*first = -1;
 }
-#else
-static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm_area_struct *vma,
-				  struct mm_walk *args, unsigned long *bitmap, unsigned long *first)
-{
-}
-#endif
 
 static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end,
 			   struct mm_walk *args)
@@ -3513,7 +3504,6 @@ static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end,
 			continue;
 		}
 
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 		if (pmd_trans_huge(val)) {
 			unsigned long pfn = pmd_pfn(val);
 			struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
@@ -3532,7 +3522,7 @@ static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end,
 			walk_pmd_range_locked(pud, addr, vma, args, bitmap, &first);
 			continue;
 		}
-#endif
+
 		walk->mm_stats[MM_NONLEAF_TOTAL]++;
 
 		if (should_clear_pmd_young()) {