[PATCH][SRU][Disco] UBUNTU: SAUCE: shiftfs: use separate llseek method for directories

[Christian Brauner]

BugLink: https://bugs.launchpad.net/bugs/1824812

Give shiftfs it's own proper llseek method for directories.

Before this commit we used to rely on an llseek method that was targeted
for regular files for both directories and regular files. Give
directories their own llseek operation.
This is required to have AppArmor function correctly with shiftfs.

Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>
---
 fs/shiftfs.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/fs/shiftfs.c b/fs/shiftfs.c
index 4c8a6ec2a617..9771165d1ce0 100644
--- a/fs/shiftfs.c
+++ b/fs/shiftfs.c
@@ -1144,7 +1144,15 @@ static int shiftfs_release(struct inode *inode, struct file *file)
 	return 0;
 }
 
-static loff_t shiftfs_llseek(struct file *file, loff_t offset, int whence)
+static loff_t shiftfs_dir_llseek(struct file *file, loff_t offset, int whence)
+{
+	struct shiftfs_file_info *file_info = file->private_data;
+	struct file *realfile = file_info->realfile;
+
+	return vfs_llseek(realfile, offset, whence);
+}
+
+static loff_t shiftfs_file_llseek(struct file *file, loff_t offset, int whence)
 {
 	struct inode *realinode = file_inode(file)->i_private;
 
@@ -1653,7 +1661,7 @@ static int shiftfs_iterate_shared(struct file *file, struct dir_context *ctx)
 const struct file_operations shiftfs_file_operations = {
 	.open			= shiftfs_open,
 	.release		= shiftfs_release,
-	.llseek			= shiftfs_llseek,
+	.llseek			= shiftfs_file_llseek,
 	.read_iter		= shiftfs_read_iter,
 	.write_iter		= shiftfs_write_iter,
 	.fsync			= shiftfs_fsync,
@@ -1670,7 +1678,7 @@ const struct file_operations shiftfs_dir_operations = {
 	.compat_ioctl		= shiftfs_compat_ioctl,
 	.fsync			= shiftfs_fsync,
 	.iterate_shared		= shiftfs_iterate_shared,
-	.llseek			= shiftfs_llseek,
+	.llseek			= shiftfs_dir_llseek,
 	.open			= shiftfs_open,
 	.read			= generic_read_dir,
 	.release		= shiftfs_release,
-- 
2.21.0