mm: add pmd_folio()

Convert directly from a pmd to a folio without going through another
representation first.  For now this is just a slightly shorter way to
write it, but it might end up being more efficient later.

Link: https://lkml.kernel.org/r/20240326202833.523759-4-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/pgtable.h

@@ -50,6 +50,8 @@
 #define pmd_pgtable(pmd) pmd_page(pmd)
 #endif
 
+#define pmd_folio(pmd) page_folio(pmd_page(pmd))
+
 /*
  * A page table page can be thought of an array like this: pXd_t[PTRS_PER_PxD]
  *

mm/huge_memory.c

@@ -1816,7 +1816,7 @@ bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 		goto out;
 	}
 
-	folio = pfn_folio(pmd_pfn(orig_pmd));
+	folio = pmd_folio(orig_pmd);
 	/*
 	 * If other processes are mapping this folio, we couldn't discard
 	 * the folio unless they all do MADV_FREE so let's skip the folio.
@@ -2086,7 +2086,7 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 		if (pmd_protnone(*pmd))
 			goto unlock;
 
-		folio = page_folio(pmd_page(*pmd));
+		folio = pmd_folio(*pmd);
 		toptier = node_is_toptier(folio_nid(folio));
 		/*
 		 * Skip scanning top tier node if normal numa
@@ -2663,7 +2663,7 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 		 * It's safe to call pmd_page when folio is set because it's
 		 * guaranteed that pmd is present.
 		 */
-		if (folio && folio != page_folio(pmd_page(*pmd)))
+		if (folio && folio != pmd_folio(*pmd))
 			goto out;
 		__split_huge_pmd_locked(vma, pmd, range.start, freeze);
 	}

mm/madvise.c

@@ -363,7 +363,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
 			goto huge_unlock;
 		}
 
-		folio = pfn_folio(pmd_pfn(orig_pmd));
+		folio = pmd_folio(orig_pmd);
 
 		/* Do not interfere with other mappings of this folio */
 		if (folio_likely_mapped_shared(folio))

mm/mempolicy.c

@@ -509,7 +509,7 @@ static void queue_folios_pmd(pmd_t *pmd, struct mm_walk *walk)
 		qp->nr_failed++;
 		return;
 	}
-	folio = pfn_folio(pmd_pfn(*pmd));
+	folio = pmd_folio(*pmd);
 	if (is_huge_zero_folio(folio)) {
 		walk->action = ACTION_CONTINUE;
 		return;

mm/mlock.c

@@ -378,7 +378,7 @@ static int mlock_pte_range(pmd_t *pmd, unsigned long addr,
 			goto out;
 		if (is_huge_zero_pmd(*pmd))
 			goto out;
-		folio = page_folio(pmd_page(*pmd));
+		folio = pmd_folio(*pmd);
 		if (vma->vm_flags & VM_LOCKED)
 			mlock_folio(folio);
 		else

mm/userfaultfd.c

@@ -1662,7 +1662,7 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start,
 			/* Check if we can move the pmd without splitting it. */
 			if (move_splits_huge_pmd(dst_addr, src_addr, src_start + len) ||
 			    !pmd_none(dst_pmdval)) {
-				struct folio *folio = pfn_folio(pmd_pfn(*src_pmd));
+				struct folio *folio = pmd_folio(*src_pmd);
 
 				if (!folio || (!is_huge_zero_folio(folio) &&
 					       !PageAnonExclusive(&folio->page))) {