From: Aurelien Aptel <aaptel@suse.com>
Date: Tue, 2 Apr 2019 13:00:33 +0200
Subject: [PATCH] CIFS: check CIFS_MOUNT_NO_DFS when trying to reuse existing
 sb
Git-commit: d070f9dd625a68d8ed4fc1de685af06a489e6f8b
Patch-mainline: v5.2-rc1
References: bsc#1144333

if we mount A then mount A again with nodfs, we shouldn't reuse the
superblock. document the purpose of the defines as well.

there are most likely more flags that needs to be added to this mask,
in fact the logic to find them should be which flag should
be *ignored* when trying to reuse an existing sb.

Signed-off-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Acked-by: Paulo Alcantara <palcantara@suse.de>
---
 fs/cifs/cifsglob.h |   11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -596,6 +596,10 @@ struct smb_vol {
 	unsigned int max_credits; /* smb3 max_credits 10 < credits < 60000 */
 };
 
+/**
+ * CIFS superblock mount flags (mnt_cifs_flags) to consider when
+ * trying to reuse existing superblock for a new mount
+ */
 #define CIFS_MOUNT_MASK (CIFS_MOUNT_NO_PERM | CIFS_MOUNT_SET_UID | \
 			 CIFS_MOUNT_SERVER_INUM | CIFS_MOUNT_DIRECT_IO | \
 			 CIFS_MOUNT_NO_XATTR | CIFS_MOUNT_MAP_SPECIAL_CHR | \
@@ -606,8 +610,13 @@ struct smb_vol {
 			 CIFS_MOUNT_NOPOSIXBRL | CIFS_MOUNT_NOSSYNC | \
 			 CIFS_MOUNT_FSCACHE | CIFS_MOUNT_MF_SYMLINKS | \
 			 CIFS_MOUNT_MULTIUSER | CIFS_MOUNT_STRICT_IO | \
-			 CIFS_MOUNT_CIFS_BACKUPUID | CIFS_MOUNT_CIFS_BACKUPGID)
+			 CIFS_MOUNT_CIFS_BACKUPUID | CIFS_MOUNT_CIFS_BACKUPGID | \
+			 CIFS_MOUNT_NO_DFS)
 
+/**
+ * Generic VFS superblock mount flags (s_flags) to consider when
+ * trying to reuse existing superblock for a new mount
+ */
 #define CIFS_MS_MASK (MS_RDONLY | MS_MANDLOCK | MS_NOEXEC | MS_NOSUID | \
 		      MS_NODEV | MS_SYNCHRONOUS)