mm: return a folio from read_swap_cache_async()

The only two callers simply call put_page() on the page returned, so
they're happier calling folio_put().  Saves two calls to compound_head().

Link: https://lkml.kernel.org/r/20231213215842.671461-13-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/madvise.c

@@ -180,7 +180,7 @@ static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,
 	for (addr = start; addr < end; addr += PAGE_SIZE) {
 		pte_t pte;
 		swp_entry_t entry;
-		struct page *page;
+		struct folio *folio;
 
 		if (!ptep++) {
 			ptep = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
@@ -198,10 +198,10 @@ static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,
 		pte_unmap_unlock(ptep, ptl);
 		ptep = NULL;
 
-		page = read_swap_cache_async(entry, GFP_HIGHUSER_MOVABLE,
+		folio = read_swap_cache_async(entry, GFP_HIGHUSER_MOVABLE,
 					     vma, addr, &splug);
-		if (page)
-			put_page(page);
+		if (folio)
+			folio_put(folio);
 	}
 
 	if (ptep)
@@ -223,17 +223,17 @@ static void shmem_swapin_range(struct vm_area_struct *vma,
 {
 	XA_STATE(xas, &mapping->i_pages, linear_page_index(vma, start));
 	pgoff_t end_index = linear_page_index(vma, end) - 1;
-	struct page *page;
+	struct folio *folio;
 	struct swap_iocb *splug = NULL;
 
 	rcu_read_lock();
-	xas_for_each(&xas, page, end_index) {
+	xas_for_each(&xas, folio, end_index) {
 		unsigned long addr;
 		swp_entry_t entry;
 
-		if (!xa_is_value(page))
+		if (!xa_is_value(folio))
 			continue;
-		entry = radix_to_swp_entry(page);
+		entry = radix_to_swp_entry(folio);
 		/* There might be swapin error entries in shmem mapping. */
 		if (non_swap_entry(entry))
 			continue;
@@ -243,10 +243,10 @@ static void shmem_swapin_range(struct vm_area_struct *vma,
 		xas_pause(&xas);
 		rcu_read_unlock();
 
-		page = read_swap_cache_async(entry, mapping_gfp_mask(mapping),
+		folio = read_swap_cache_async(entry, mapping_gfp_mask(mapping),
 					     vma, addr, &splug);
-		if (page)
-			put_page(page);
+		if (folio)
+			folio_put(folio);
 
 		rcu_read_lock();
 	}

mm/swap.h

@@ -46,10 +46,9 @@ struct folio *swap_cache_get_folio(swp_entry_t entry,
 struct folio *filemap_get_incore_folio(struct address_space *mapping,
 		pgoff_t index);
 
-struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
-				   struct vm_area_struct *vma,
-				   unsigned long addr,
-				   struct swap_iocb **plug);
+struct folio *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
+		struct vm_area_struct *vma, unsigned long addr,
+		struct swap_iocb **plug);
 struct folio *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_flags,
 		struct mempolicy *mpol, pgoff_t ilx, bool *new_page_allocated,
 		bool skip_if_exists);

mm/swap_state.c

@@ -533,9 +533,9 @@ struct folio *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
  * __read_swap_cache_async() call them and swap_read_folio() holds the
  * swap cache folio lock.
  */
-struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
-				   struct vm_area_struct *vma,
-				   unsigned long addr, struct swap_iocb **plug)
+struct folio *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
+		struct vm_area_struct *vma, unsigned long addr,
+		struct swap_iocb **plug)
 {
 	bool page_allocated;
 	struct mempolicy *mpol;
@@ -549,7 +549,7 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
 
 	if (page_allocated)
 		swap_read_folio(folio, false, plug);
-	return folio_file_page(folio, swp_offset(entry));
+	return folio;
 }
 
 static unsigned int __swapin_nr_pages(unsigned long prev_offset,