mm: convert collapse_huge_page() to use a folio

Replace three calls to compound_head() with one.

Link: https://lkml.kernel.org/r/20231211162214.2146080-9-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>

mm/khugepaged.c

@@ -1090,6 +1090,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
 	pmd_t *pmd, _pmd;
 	pte_t *pte;
 	pgtable_t pgtable;
+	struct folio *folio;
 	struct page *hpage;
 	spinlock_t *pmd_ptl, *pte_ptl;
 	int result = SCAN_FAIL;
@@ -1212,13 +1213,13 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
 	if (unlikely(result != SCAN_SUCCEED))
 		goto out_up_write;
 
+	folio = page_folio(hpage);
 	/*
-	 * spin_lock() below is not the equivalent of smp_wmb(), but
-	 * the smp_wmb() inside __SetPageUptodate() can be reused to
-	 * avoid the copy_huge_page writes to become visible after
-	 * the set_pmd_at() write.
+	 * The smp_wmb() inside __folio_mark_uptodate() ensures the
+	 * copy_huge_page writes become visible before the set_pmd_at()
+	 * write.
 	 */
-	__SetPageUptodate(hpage);
+	__folio_mark_uptodate(folio);
 	pgtable = pmd_pgtable(_pmd);
 
 	_pmd = mk_huge_pmd(hpage, vma->vm_page_prot);
@@ -1226,8 +1227,8 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
 
 	spin_lock(pmd_ptl);
 	BUG_ON(!pmd_none(*pmd));
-	page_add_new_anon_rmap(hpage, vma, address);
-	lru_cache_add_inactive_or_unevictable(hpage, vma);
+	folio_add_new_anon_rmap(folio, vma, address);
+	folio_add_lru_vma(folio, vma);
 	pgtable_trans_huge_deposit(mm, pmd, pgtable);
 	set_pmd_at(mm, address, pmd, _pmd);
 	update_mmu_cache_pmd(vma, address, pmd);