[RFC PATCH v2 4/8] ovl: mark overlayfs' inode dirty on modification

[Chengguang Xu <cgxu519@mykernel.net>]

Mark overlayfs' inode dirty on modification so that
we can recognize target inodes during syncfs.

Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
---
 fs/overlayfs/inode.c     |  1 +
 fs/overlayfs/overlayfs.h |  4 ++++
 fs/overlayfs/util.c      | 14 ++++++++++++++
 3 files changed, 19 insertions(+)

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index f27fc5be34df..426f70ca5d5e 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -468,6 +468,7 @@ int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags)
 		if (upperpath.dentry) {
 			touch_atime(&upperpath);
 			inode->i_atime = d_inode(upperpath.dentry)->i_atime;
+			ovl_mark_inode_dirty(inode);
 		}
 	}
 	return 0;
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index f8880aa2ba0e..eaf1d5b05d8e 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -247,6 +247,7 @@ static inline bool ovl_open_flags_need_copy_up(int flags)
 }
 
 /* util.c */
+void ovl_mark_inode_dirty(struct inode *inode);
 int ovl_want_write(struct dentry *dentry);
 void ovl_drop_write(struct dentry *dentry);
 struct dentry *ovl_workdir(struct dentry *dentry);
@@ -472,6 +473,9 @@ static inline void ovl_copyattr(struct inode *from, struct inode *to)
 	to->i_mtime = from->i_mtime;
 	to->i_ctime = from->i_ctime;
 	i_size_write(to, i_size_read(from));
+
+	if (ovl_inode_upper(to) && from->i_state & I_DIRTY_ALL)
+		ovl_mark_inode_dirty(to);
 }
 
 static inline void ovl_copyflags(struct inode *from, struct inode *to)
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 23f475627d07..a6f59df744ae 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -950,3 +950,17 @@ char *ovl_get_redirect_xattr(struct ovl_fs *ofs, struct dentry *dentry,
 	kfree(buf);
 	return ERR_PTR(res);
 }
+
+/*
+ * We intentionally add I_DIRTY_SYNC flag regardless dirty flag
+ * of upper inode so that we have chance to invoke ->write_inode
+ * to re-dirty overlayfs' inode during writeback process.
+ */
+void ovl_mark_inode_dirty(struct inode *inode)
+{
+	struct inode *upper = ovl_inode_upper(inode);
+	unsigned long iflag = I_DIRTY_SYNC;
+
+	iflag |= upper->i_state & I_DIRTY_ALL;
+	__mark_inode_dirty(inode, iflag);
+}
-- 
2.26.2