cifs: share dfs connections and supers

When matching DFS superblocks we can't rely on either the server's
address or tcon's UNC name from mount(2) as the existing servers and
tcons might be connected to somewhere else.  Instead, check if
superblock is dfs, and if so, match its original source pathname with
the new mount's source pathname.

For DFS connections, instead of checking server's address, match its
referral path as it could be connected to different targets.

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: Paulo Alcantara

fs/cifs/cifs_debug.c

@@ -372,6 +372,14 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v)
 		seq_printf(m, "\nIn Send: %d In MaxReq Wait: %d",
 				atomic_read(&server->in_send),
 				atomic_read(&server->num_waiters));
+		if (IS_ENABLED(CONFIG_CIFS_DFS_UPCALL)) {
+			if (server->origin_fullpath)
+				seq_printf(m, "\nDFS origin full path: %s",
+					   server->origin_fullpath);
+			if (server->leaf_fullpath)
+				seq_printf(m, "\nDFS leaf full path:   %s",
+					   server->leaf_fullpath);
+		}
 
 		seq_printf(m, "\n\n\tSessions: ");
 		i = 0;

fs/cifs/cifsglob.h

@@ -738,8 +738,6 @@ struct TCP_Server_Info {
 	bool use_swn_dstaddr;
 	struct sockaddr_storage swn_dstaddr;
 #endif
-#ifdef CONFIG_CIFS_DFS_UPCALL
-	bool is_dfs_conn; /* if a dfs connection */
 	struct mutex refpath_lock; /* protects leaf_fullpath */
 	/*
 	 * Canonical DFS full paths that were used to chase referrals in mount and reconnect.
@@ -753,7 +751,6 @@ struct TCP_Server_Info {
 	 * format: \\HOST\SHARE\[OPTIONAL PATH]
 	 */
 	char *origin_fullpath, *leaf_fullpath, *current_fullpath;
-#endif
 };
 
 static inline bool is_smb1(struct TCP_Server_Info *server)
@@ -1767,11 +1764,9 @@ struct cifs_mount_ctx {
 	struct TCP_Server_Info *server;
 	struct cifs_ses *ses;
 	struct cifs_tcon *tcon;
-#ifdef CONFIG_CIFS_DFS_UPCALL
 	struct cifs_ses *root_ses;
 	uuid_t mount_id;
 	char *origin_fullpath, *leaf_fullpath;
-#endif
 };
 
 static inline void free_dfs_info_param(struct dfs_info3_param *param)

fs/cifs/cifsproto.h

@@ -242,7 +242,9 @@ extern int cifs_read_page_from_socket(struct TCP_Server_Info *server,
 					unsigned int page_offset,
 					unsigned int to_read);
 extern int cifs_setup_cifs_sb(struct cifs_sb_info *cifs_sb);
+void cifs_mount_put_conns(struct cifs_mount_ctx *mnt_ctx);
 int cifs_mount_get_session(struct cifs_mount_ctx *mnt_ctx);
+int cifs_is_path_remote(struct cifs_mount_ctx *mnt_ctx);
 int cifs_mount_get_tcon(struct cifs_mount_ctx *mnt_ctx);
 extern int cifs_match_super(struct super_block *, void *);
 extern int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb3_fs_context *ctx);