[PATCH 03/10] ovl: use correct seek function for directories.

[NeilBrown <neilb@suse.de>]

It is incorrect to call generic_llseek_file on a file from a different
filesystem.  For that we must use the seek function that the
filesystem defines, which is called by vfs_llseek.

Also, we only want to seek the realfile when is_real is true.
Otherwise we just want to update our own f_pos pointer, so use
generic_llseek_file for that.

Signed-off-by: NeilBrown <neilb@suse.de>
---
 fs/overlayfs/overlayfs.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/overlayfs/overlayfs.c b/fs/overlayfs/overlayfs.c
index 4e032e8..306de45 100644
--- a/fs/overlayfs/overlayfs.c
+++ b/fs/overlayfs/overlayfs.c
@@ -307,8 +307,11 @@ static loff_t ovl_dir_llseek(struct file *file, loff_t offset, int origin)
 	loff_t res;
 	struct ovl_dir_file *od = file->private_data;
 
-	res = generic_file_llseek(od->realfile, offset, origin);
-	file->f_pos = od->realfile->f_pos;
+	if (od->is_real) {
+		res = vfs_llseek(od->realfile, offset, origin);
+		file->f_pos = od->realfile->f_pos;
+	} else
+		res = generic_file_llseek(file, offset, origin);
 
 	return res;
 }