[SRU][FOCAL][PATCH 2/2] Revert "UBUNTU: SAUCE: overlayfs: use shiftfs hacks only with shiftfs as underlay"

[Kleber Sacilotto de Souza]

BugLink: https://bugs.launchpad.net/bugs/1879690

This reverts commit 6f18a8434050333afc80b5bfce2e0e994c86b790.

The change applied for LP: #1857257 and its followup fix LP: #1876645
introduced a regression on overlayfs. Revert these commits for now.

Signed-off-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>
---
 fs/overlayfs/file.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index a2faa086ee4b..1a1c1746bf83 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -3,7 +3,6 @@
  * Copyright (C) 2017 Red Hat, Inc.
  */
 
-#include <uapi/linux/magic.h>
 #include <linux/cred.h>
 #include <linux/file.h>
 #include <linux/mount.h>
@@ -32,12 +31,9 @@ static struct file *ovl_open_realfile(const struct file *file,
 	int flags = file->f_flags | O_NOATIME | FMODE_NONOTIFY;
 
 	old_cred = ovl_override_creds(inode->i_sb);
-	if (realpath.dentry->d_sb->s_magic == SHIFTFS_MAGIC)
-		realfile = open_with_fake_path(&realpath, flags, realinode,
-					       current_cred());
-	else
-		realfile = open_with_fake_path(&file->f_path, flags, realinode,
-					       current_cred());
+	ovl_path_real(file->f_path.dentry, &realpath);
+	realfile = open_with_fake_path(&realpath, flags, realinode,
+				       current_cred());
 	revert_creds(old_cred);
 
 	pr_debug("open(%p[%pD2/%c], 0%o) -> (%p, 0%o)\n",
-- 
2.20.1