mm: make HPAGE_PXD_* macros even if !THP

These macros can be helpful when we plan to merge hugetlb code into
generic code.  Move them out and define them as long as
PGTABLE_HAS_HUGE_LEAVES is selected, because there are systems that only
define HUGETLB_PAGE not THP.

One note here is HPAGE_PMD_SHIFT must be defined even if PMD_SHIFT is not
defined (e.g.  !CONFIG_MMU case); it (or in other forms, like
HPAGE_PMD_NR) is already used in lots of common codes without ifdef
guards.  Use the old trick to let complations work.

Here we only need to differenciate HPAGE_PXD_SHIFT definitions.  All the
rest macros will be defined based on it.  When at it, move HPAGE_PMD_NR /
HPAGE_PMD_ORDER over together.

Link: https://lkml.kernel.org/r/20240327152332.950956-4-peterx@redhat.comSigned-off-by: Peter Xu <peterx@redhat.com>
Tested-by: Ryan Roberts <ryan.roberts@arm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andrew Jones <andrew.jones@linux.dev>
Cc: Aneesh Kumar K.V (IBM) <aneesh.kumar@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Mike Rapoport (IBM)" <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/huge_mm.h

@@ -64,9 +64,6 @@ ssize_t single_hugepage_flag_show(struct kobject *kobj,
 				  enum transparent_hugepage_flag flag);
 extern struct kobj_attribute shmem_enabled_attr;
 
-#define HPAGE_PMD_ORDER (HPAGE_PMD_SHIFT-PAGE_SHIFT)
-#define HPAGE_PMD_NR (1<<HPAGE_PMD_ORDER)
-
 /*
  * Mask of all large folio orders supported for anonymous THP; all orders up to
  * and including PMD_ORDER, except order-0 (which is not "huge") and order-1
@@ -87,14 +84,25 @@ extern struct kobj_attribute shmem_enabled_attr;
 #define thp_vma_allowable_order(vma, vm_flags, smaps, in_pf, enforce_sysfs, order) \
 	(!!thp_vma_allowable_orders(vma, vm_flags, smaps, in_pf, enforce_sysfs, BIT(order)))
 
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+#ifdef CONFIG_PGTABLE_HAS_HUGE_LEAVES
 #define HPAGE_PMD_SHIFT PMD_SHIFT
-#define HPAGE_PMD_SIZE	((1UL) << HPAGE_PMD_SHIFT)
+#define HPAGE_PUD_SHIFT PUD_SHIFT
+#else
+#define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
+#define HPAGE_PUD_SHIFT ({ BUILD_BUG(); 0; })
+#endif
+
+#define HPAGE_PMD_ORDER (HPAGE_PMD_SHIFT-PAGE_SHIFT)
+#define HPAGE_PMD_NR (1<<HPAGE_PMD_ORDER)
 #define HPAGE_PMD_MASK	(~(HPAGE_PMD_SIZE - 1))
+#define HPAGE_PMD_SIZE	((1UL) << HPAGE_PMD_SHIFT)
 
-#define HPAGE_PUD_SHIFT PUD_SHIFT
-#define HPAGE_PUD_SIZE	((1UL) << HPAGE_PUD_SHIFT)
+#define HPAGE_PUD_ORDER (HPAGE_PUD_SHIFT-PAGE_SHIFT)
+#define HPAGE_PUD_NR (1<<HPAGE_PUD_ORDER)
 #define HPAGE_PUD_MASK	(~(HPAGE_PUD_SIZE - 1))
+#define HPAGE_PUD_SIZE	((1UL) << HPAGE_PUD_SHIFT)
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 
 extern unsigned long transparent_hugepage_flags;
 extern unsigned long huge_anon_orders_always;
@@ -377,13 +385,6 @@ static inline bool thp_migration_supported(void)
 }
 
 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
-#define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
-#define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; })
-#define HPAGE_PMD_SIZE ({ BUILD_BUG(); 0; })
-
-#define HPAGE_PUD_SHIFT ({ BUILD_BUG(); 0; })
-#define HPAGE_PUD_MASK ({ BUILD_BUG(); 0; })
-#define HPAGE_PUD_SIZE ({ BUILD_BUG(); 0; })
 
 static inline bool folio_test_pmd_mappable(struct folio *folio)
 {