[RFC PATCH v2 6/8] ovl: implement overlayfs' ->write_inode operation

[Chengguang Xu <cgxu519@mykernel.net>]

Implement overlayfs' ->write_inode to sync dirty data
and redirty overlayfs' inode if necessary.

Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
---
 fs/overlayfs/super.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 5d7e12b8bd1f..960e79e7a8b5 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -15,6 +15,7 @@
 #include <linux/seq_file.h>
 #include <linux/posix_acl_xattr.h>
 #include <linux/exportfs.h>
+#include <linux/writeback.h>
 #include "overlayfs.h"
 
 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
@@ -396,11 +397,36 @@ static void ovl_evict_inode (struct inode *inode)
 	clear_inode(inode);
 }
 
+static int ovl_write_inode(struct inode *inode,
+			   struct writeback_control *wbc)
+{
+	struct inode *upper = ovl_inode_upper(inode);
+	unsigned long iflag = 0;
+	int ret = 0;
+
+	if (!upper)
+		return 0;
+
+	if (upper->i_sb->s_op->write_inode)
+		ret = upper->i_sb->s_op->write_inode(inode, wbc);
+
+	iflag |= upper->i_state & I_DIRTY_ALL;
+	if (mapping_writably_mapped(upper->i_mapping) ||
+	    mapping_tagged(upper->i_mapping, PAGECACHE_TAG_WRITEBACK))
+		iflag |= I_DIRTY_PAGES;
+
+	if (iflag)
+		ovl_mark_inode_dirty(inode);
+
+	return ret;
+}
+
 static const struct super_operations ovl_super_operations = {
 	.alloc_inode	= ovl_alloc_inode,
 	.free_inode	= ovl_free_inode,
 	.destroy_inode	= ovl_destroy_inode,
 	.drop_inode	= generic_delete_inode,
+	.write_inode	= ovl_write_inode,
 	.evict_inode	= ovl_evict_inode,
 	.put_super	= ovl_put_super,
 	.sync_fs	= ovl_sync_fs,
-- 
2.26.2