NFS: Add a helper nfs_wb_folio()

...and use it in nfs_launder_folio().
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/file.c

@@ -469,7 +469,7 @@ static int nfs_launder_folio(struct folio *folio)
 		inode->i_ino, folio_pos(folio));
 
 	folio_wait_fscache(folio);
-	return nfs_wb_page(inode, &folio->page);
+	return nfs_wb_folio(inode, folio);
 }
 
 static int nfs_swap_activate(struct swap_info_struct *sis, struct file *file,

fs/nfs/write.c

@@ -2106,6 +2106,19 @@ int nfs_wb_page(struct inode *inode, struct page *page)
 	return ret;
 }
 
+/**
+ * nfs_wb_folio - Write back all requests on one page
+ * @inode: pointer to page
+ * @folio: pointer to folio
+ *
+ * Assumes that the folio has been locked by the caller, and will
+ * not unlock it.
+ */
+int nfs_wb_folio(struct inode *inode, struct folio *folio)
+{
+	return nfs_wb_page(inode, &folio->page);
+}
+
 #ifdef CONFIG_MIGRATION
 int nfs_migrate_folio(struct address_space *mapping, struct folio *dst,
 		struct folio *src, enum migrate_mode mode)

include/linux/nfs_fs.h

@@ -578,6 +578,7 @@ extern int  nfs_updatepage(struct file *, struct page *, unsigned int, unsigned
  */
 extern int nfs_sync_inode(struct inode *inode);
 extern int nfs_wb_all(struct inode *inode);
+extern int nfs_wb_folio(struct inode *inode, struct folio *folio);
 extern int nfs_wb_page(struct inode *inode, struct page *page);
 int nfs_wb_folio_cancel(struct inode *inode, struct folio *folio);
 extern int  nfs_commit_inode(struct inode *, int);