[PATCH] overlay: Plumb through flush method

[Sargun Dhillon <sargun@sargun.me>]

Filesystems can implement their own flush method that release
resources, or manipulate caches. Currently if one of these
filesystems is used with overlayfs, the flush method is not called.

Signed-off-by: Sargun Dhillon <sargun@sargun.me>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-unionfs@vger.kernel.org
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Amir Goldstein <amir73il@gmail.com>
---
 fs/overlayfs/file.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index efccb7c1f9bc..802259f33c28 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -787,6 +787,16 @@ static loff_t ovl_remap_file_range(struct file *file_in, loff_t pos_in,
 			    remap_flags, op);
 }
 
+static int ovl_flush(struct file *file, fl_owner_t id)
+{
+	struct file *realfile = file->private_data;
+
+	if (realfile->f_op->flush)
+		return realfile->f_op->flush(realfile, id);
+
+	return 0;
+}
+
 const struct file_operations ovl_file_operations = {
 	.open		= ovl_open,
 	.release	= ovl_release,
@@ -798,6 +808,7 @@ const struct file_operations ovl_file_operations = {
 	.fallocate	= ovl_fallocate,
 	.fadvise	= ovl_fadvise,
 	.unlocked_ioctl	= ovl_ioctl,
+	.flush		= ovl_flush,
 #ifdef CONFIG_COMPAT
 	.compat_ioctl	= ovl_compat_ioctl,
 #endif
-- 
2.25.1