[RFC PATCH 03/10] mm/swap: convert swapin_readahead to return a folio

[Kairui Song <ryncsn@xxxxxxxxx>]

From: Kairui Song <kasong@xxxxxxxxxxx>

Simplify the caller code logic.

Signed-off-by: Kairui Song <kasong@xxxxxxxxxxx>
---
 mm/memory.c     | 8 +++-----
 mm/swap.h       | 4 ++--
 mm/swap_state.c | 6 ++----
 mm/swapfile.c   | 5 +----
 4 files changed, 8 insertions(+), 15 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index e42fadc25268..dfdb620a9123 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4005,12 +4005,8 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 			if (PTR_ERR(folio) == -EBUSY)
 				goto out;
 			need_clear_cache = true;
-			page = &folio->page;
 		} else {
-			page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE,
-						vmf);
-			if (page)
-				folio = page_folio(page);
+			folio = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE, vmf);
 			swapcache = folio;
 		}
 
@@ -4027,6 +4023,8 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 			goto unlock;
 		}
 
+		page = folio_file_page(folio, swp_offset(entry));
+
 		/* Had to read the page from swap area: Major fault */
 		ret = VM_FAULT_MAJOR;
 		count_vm_event(PGMAJFAULT);
diff --git a/mm/swap.h b/mm/swap.h
index 40e902812cc5..aee134907a70 100644
--- a/mm/swap.h
+++ b/mm/swap.h
@@ -57,7 +57,7 @@ struct folio *swap_cluster_readahead(swp_entry_t entry, gfp_t flag,
 		struct mempolicy *mpol, pgoff_t ilx);
 struct folio *swapin_direct(swp_entry_t entry, gfp_t flag,
 			    struct vm_fault *vmf);
-struct page *swapin_readahead(swp_entry_t entry, gfp_t flag,
+struct folio *swapin_readahead(swp_entry_t entry, gfp_t flag,
 			      struct vm_fault *vmf);
 
 static inline unsigned int folio_swap_flags(struct folio *folio)
@@ -95,7 +95,7 @@ static inline struct folio *swapin_direct(swp_entry_t entry, gfp_t flag,
 	return NULL;
 }
 
-static inline struct page *swapin_readahead(swp_entry_t swp, gfp_t gfp_mask,
+static inline struct folio *swapin_readahead(swp_entry_t swp, gfp_t gfp_mask,
 			struct vm_fault *vmf)
 {
 	return NULL;
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 0a3fa48b3893..2a9c6bdff5ea 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -951,7 +951,7 @@ struct folio *swapin_direct(swp_entry_t entry, gfp_t gfp_mask,
  * it will read ahead blocks by cluster-based(ie, physical disk based)
  * or vma-based(ie, virtual address based on faulty address) readahead.
  */
-struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
+struct folio *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
 				struct vm_fault *vmf)
 {
 	struct mempolicy *mpol;
@@ -964,9 +964,7 @@ struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
 		swap_cluster_readahead(entry, gfp_mask, mpol, ilx);
 	mpol_cond_put(mpol);
 
-	if (!folio)
-		return NULL;
-	return folio_file_page(folio, swp_offset(entry));
+	return folio;
 }
 
 #ifdef CONFIG_SYSFS
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 4919423cce76..4dd894395a0f 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1883,7 +1883,6 @@ static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 
 		folio = swap_cache_get_folio(entry, vma, addr);
 		if (!folio) {
-			struct page *page;
 			struct vm_fault vmf = {
 				.vma = vma,
 				.address = addr,
@@ -1891,10 +1890,8 @@ static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 				.pmd = pmd,
 			};
 
-			page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE,
+			folio = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE,
 						&vmf);
-			if (page)
-				folio = page_folio(page);
 		}
 		if (!folio) {
 			swp_count = READ_ONCE(si->swap_map[offset]);
-- 
2.43.0