CIFS: make 'nodfs' mount opt a superblock flag

tcon->Flags is only used by SMB1 code and changing it is not permanent
(you lose the setting on tcon reconnect).

* Move the setting to superblock flags (per mount-points).
* Make automount callback exit early when flag present
* Make dfs resolving happening in mount syscall exit early if flag present

Signed-off-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Acked-by: Pavel Shilovsky <pshilov@microsoft.com>

4 files changed, 14 insertions, 5 deletions

diff --git a/fs/cifs/cifs_dfs_ref.c b/fs/cifs/cifs_dfs_ref.c
index 6b61df117fd4..b97c74efd04a 100644
--- a/fs/cifs/cifs_dfs_ref.c
+++ b/fs/cifs/cifs_dfs_ref.c
@@ -304,12 +304,17 @@ static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
          */
         mnt = ERR_PTR(-ENOMEM);
 
+        cifs_sb = CIFS_SB(mntpt->d_sb);
+        if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS) {
+                mnt = ERR_PTR(-EREMOTE);
+                goto cdda_exit;
+        }
+
         /* always use tree name prefix */
         full_path = build_path_from_dentry_optional_prefix(mntpt, true);
         if (full_path == NULL)
                 goto cdda_exit;
 
-        cifs_sb = CIFS_SB(mntpt->d_sb);
         tlink = cifs_sb_tlink(cifs_sb);
         if (IS_ERR(tlink)) {
                 mnt = ERR_CAST(tlink);
diff --git a/fs/cifs/cifs_fs_sb.h b/fs/cifs/cifs_fs_sb.h
index 9731d0d891e7..63d7530f2e1d 100644
--- a/fs/cifs/cifs_fs_sb.h
+++ b/fs/cifs/cifs_fs_sb.h
@@ -51,6 +51,7 @@
                                               */
 #define CIFS_MOUNT_UID_FROM_ACL 0x2000000 /* try to get UID via special SID */
 #define CIFS_MOUNT_NO_HANDLE_CACHE 0x4000000 /* disable caching dir handles */
+#define CIFS_MOUNT_NO_DFS 0x8000000 /* disable DFS resolving */
 
 struct cifs_sb_info {
         struct rb_root tlink_tree;
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index ba0054604f85..d2f9bc48ffac 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -500,6 +500,8 @@ cifs_show_options(struct seq_file *s, struct dentry *root)
                 seq_puts(s, ",unix");
         else
                 seq_puts(s, ",nounix");
+        if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS)
+                seq_puts(s, ",nodfs");
         if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS)
                 seq_puts(s, ",posixpaths");
         if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_SET_UID)
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 106d3a85f77b..6221aef45ff5 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -3086,10 +3086,6 @@ cifs_get_tcon(struct cifs_ses *ses, struct smb_vol *volume_info)
         if (rc)
                 goto out_fail;
 
-        if (volume_info->nodfs) {
-                tcon->Flags &= ~SMB_SHARE_IS_IN_DFS;
-                cifs_dbg(FYI, "DFS disabled (%d)\n", tcon->Flags);
-        }
         tcon->use_persistent = false;
         /* check if SMB2 or later, CIFS does not support persistent handles */
         if (volume_info->persistent) {
@@ -3664,6 +3660,8 @@ int cifs_setup_cifs_sb(struct smb_vol *pvolume_info,
         cifs_sb->actimeo = pvolume_info->actimeo;
         cifs_sb->local_nls = pvolume_info->local_nls;
 
+        if (pvolume_info->nodfs)
+                cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_NO_DFS;
         if (pvolume_info->noperm)
                 cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_NO_PERM;
         if (pvolume_info->setuids)
@@ -3820,6 +3818,9 @@ expand_dfs_referral(const unsigned int xid, struct cifs_ses *ses,
         struct dfs_info3_param *referrals = NULL;
         char *full_path = NULL, *ref_path = NULL, *mdata = NULL;
 
+        if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS)
+                return -EREMOTE;
+
         full_path = build_unc_path_to_root(volume_info, cifs_sb);
         if (IS_ERR(full_path))
                 return PTR_ERR(full_path);