shmem: Add shmem_writeout()

This will be the replacement for shmem_writepage().

Signed-off-by: "Matthew Wilcox (Oracle)" <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Baolin Wang <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>

Author: Matthew Wilcox (Oracle)

include/linux/shmem_fs.h

@@ -104,10 +104,11 @@ static inline bool shmem_mapping(struct address_space *mapping)
 	return false;
 }
 #endif /* CONFIG_SHMEM */
-extern void shmem_unlock_mapping(struct address_space *mapping);
-extern struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
+void shmem_unlock_mapping(struct address_space *mapping);
+struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
 					pgoff_t index, gfp_t gfp_mask);
-extern void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end);
+int shmem_writeout(struct folio *folio, struct writeback_control *wbc);
+void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end);
 int shmem_unuse(unsigned int type);
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE

mm/shmem.c

@@ -1536,12 +1536,20 @@ int shmem_unuse(unsigned int type)
 	return error;
 }
 
-/*
- * Move the page from the page cache to the swap cache.
- */
 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 {
-	struct folio *folio = page_folio(page);
+	return shmem_writeout(page_folio(page), wbc);
+}
+
+/**
+ * shmem_writeout - Write the folio to swap
+ * @folio: The folio to write
+ * @wbc: How writeback is to be done
+ *
+ * Move the folio from the page cache to the swap cache.
+ */
+int shmem_writeout(struct folio *folio, struct writeback_control *wbc)
+{
 	struct address_space *mapping = folio->mapping;
 	struct inode *inode = mapping->host;
 	struct shmem_inode_info *info = SHMEM_I(inode);
@@ -1586,9 +1594,8 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 try_split:
 		/* Ensure the subpages are still dirty */
 		folio_test_set_dirty(folio);
-		if (split_huge_page_to_list_to_order(page, wbc->list, 0))
+		if (split_folio_to_list(folio, wbc->list))
 			goto redirty;
-		folio = page_folio(page);
 		folio_clear_dirty(folio);
 	}
 
@@ -1660,6 +1667,7 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 	folio_unlock(folio);
 	return 0;
 }
+EXPORT_SYMBOL_GPL(shmem_writeout);
 
 #if defined(CONFIG_NUMA) && defined(CONFIG_TMPFS)
 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)