cifs: support nested dfs links over reconnect

Mounting a dfs link that has nested links was already supported at
mount(2), so make it work over reconnect as well.

Make the following case work:

* mount //root/dfs/link /mnt -o ...
  - final share: /server/share

* in server settings
  - change target folder of /root/dfs/link3 to /server/share2
  - change target folder of /root/dfs/link2 to /root/dfs/link3
  - change target folder of /root/dfs/link to /root/dfs/link2

* mount -o remount,... /mnt
 - refresh all dfs referrals
 - mark current connection for failover
 - cifs_reconnect() reconnects to root server
 - tree_connect()
   * checks that /root/dfs/link2 is a link, then chase it
   * checks that root/dfs/link3 is a link, then chase it
   * finally tree connect to /server/share2

If the mounted share is no longer accessible and a reconnect had been
triggered, the client will retry it from both last referral
path (/root/dfs/link3) and original referral path (/root/dfs/link).

Any new referral paths found while chasing dfs links over reconnect,
it will be updated to TCP_Server_Info::leaf_fullpath, accordingly.

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

9 files changed, 660 insertions, 693 deletions

diff --git a/fs/cifs/cifs_dfs_ref.c b/fs/cifs/cifs_dfs_ref.c
index 007427ba75e5..b0864da9ef43 100644
--- a/fs/cifs/cifs_dfs_ref.c
+++ b/fs/cifs/cifs_dfs_ref.c
@@ -307,12 +307,8 @@ static struct vfsmount *cifs_dfs_do_mount(struct dentry *mntpt,
 static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
 {
 	struct cifs_sb_info *cifs_sb;
-	struct cifs_ses *ses;
-	struct cifs_tcon *tcon;
 	void *page;
-	char *full_path, *root_path;
-	unsigned int xid;
-	int rc;
+	char *full_path;
 	struct vfsmount *mnt;
 
 	cifs_dbg(FYI, "in %s\n", __func__);
@@ -324,8 +320,6 @@ static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
 	 * the double backslashes usually used in the UNC. This function
 	 * gives us the latter, so we must adjust the result.
 	 */
-	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);
@@ -341,60 +335,11 @@ static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
 	}
 
 	convert_delimiter(full_path, '\\');
-
 	cifs_dbg(FYI, "%s: full_path: %s\n", __func__, full_path);
 
-	if (!cifs_sb_master_tlink(cifs_sb)) {
-		cifs_dbg(FYI, "%s: master tlink is NULL\n", __func__);
-		goto free_full_path;
-	}
-
-	tcon = cifs_sb_master_tcon(cifs_sb);
-	if (!tcon) {
-		cifs_dbg(FYI, "%s: master tcon is NULL\n", __func__);
-		goto free_full_path;
-	}
-
-	root_path = kstrdup(tcon->treeName, GFP_KERNEL);
-	if (!root_path) {
-		mnt = ERR_PTR(-ENOMEM);
-		goto free_full_path;
-	}
-	cifs_dbg(FYI, "%s: root path: %s\n", __func__, root_path);
-
-	ses = tcon->ses;
-	xid = get_xid();
-
-	/*
-	 * If DFS root has been expired, then unconditionally fetch it again to
-	 * refresh DFS referral cache.
-	 */
-	rc = dfs_cache_find(xid, ses, cifs_sb->local_nls, cifs_remap(cifs_sb),
-			    root_path + 1, NULL, NULL);
-	if (!rc) {
-		rc = dfs_cache_find(xid, ses, cifs_sb->local_nls,
-				    cifs_remap(cifs_sb), full_path + 1,
-				    NULL, NULL);
-	}
-
-	free_xid(xid);
-
-	if (rc) {
-		mnt = ERR_PTR(rc);
-		goto free_root_path;
-	}
-	/*
-	 * OK - we were able to get and cache a referral for @full_path.
-	 *
-	 * Now, pass it down to cifs_mount() and it will retry every available
-	 * node server in case of failures - no need to do it here.
-	 */
 	mnt = cifs_dfs_do_mount(mntpt, cifs_sb, full_path);
-	cifs_dbg(FYI, "%s: cifs_dfs_do_mount:%s , mnt:%p\n", __func__,
-		 full_path + 1, mnt);
+	cifs_dbg(FYI, "%s: cifs_dfs_do_mount:%s , mnt:%p\n", __func__, full_path + 1, mnt);
 
-free_root_path:
-	kfree(root_path);
 free_full_path:
 	free_dentry_path(page);
 cdda_exit:
diff --git a/fs/cifs/cifs_fs_sb.h b/fs/cifs/cifs_fs_sb.h
index f97407520ea1..013a4bd65280 100644
--- a/fs/cifs/cifs_fs_sb.h
+++ b/fs/cifs/cifs_fs_sb.h
@@ -61,11 +61,6 @@ struct cifs_sb_info {
 	/* only used when CIFS_MOUNT_USE_PREFIX_PATH is set */
 	char *prepath;
 
-	/*
-	 * Canonical DFS path initially provided by the mount call. We might connect to something
-	 * different via DFS but we want to keep it to do failover properly.
-	 */
-	char *origin_fullpath; /* \\HOST\SHARE\[OPTIONAL PATH] */
 	/* randomly generated 128-bit number for indexing dfs mount groups in referral cache */
 	uuid_t dfs_mount_id;
 	/*
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 102a4a2b734d..673ecbfe6d9a 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -697,6 +697,19 @@ struct TCP_Server_Info {
 #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.
+	 *
+	 * origin_fullpath: first or original referral path
+	 * leaf_fullpath: last referral path (might be changed due to nested links in reconnect)
+	 *
+	 * current_fullpath: pointer to either origin_fullpath or leaf_fullpath
+	 * NOTE: cannot be accessed outside cifs_reconnect() and smb2_reconnect()
+	 *
+	 * format: \\HOST\SHARE\[OPTIONAL PATH]
+	 */
+	char *origin_fullpath, *leaf_fullpath, *current_fullpath;
 #endif
 };
 
@@ -1097,7 +1110,6 @@ struct cifs_tcon {
 	struct cached_fid crfid; /* Cached root fid */
 	/* BB add field for back pointer to sb struct(s)? */
 #ifdef CONFIG_CIFS_DFS_UPCALL
-	char *dfs_path; /* canonical DFS path */
 	struct list_head ulist; /* cache update list */
 #endif
 };
@@ -1948,4 +1960,14 @@ static inline bool is_tcon_dfs(struct cifs_tcon *tcon)
 		tcon->share_flags & (SHI1005_FLAGS_DFS | SHI1005_FLAGS_DFS_ROOT);
 }
 
+static inline bool cifs_is_referral_server(struct cifs_tcon *tcon,
+					   const struct dfs_info3_param *ref)
+{
+	/*
+	 * Check if all targets are capable of handling DFS referrals as per
+	 * MS-DFSC 2.2.4 RESP_GET_DFS_REFERRAL.
+	 */
+	return is_tcon_dfs(tcon) || (ref && (ref->flags & DFSREF_REFERRAL_SERVER));
+}
+
 #endif	/* _CIFS_GLOB_H */
diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index d0f85b666662..b2697356b5e7 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -607,7 +607,7 @@ int smb2_parse_query_directory(struct cifs_tcon *tcon, struct kvec *rsp_iov,
 
 struct super_block *cifs_get_tcp_super(struct TCP_Server_Info *server);
 void cifs_put_tcp_super(struct super_block *sb);
-int update_super_prepath(struct cifs_tcon *tcon, char *prefix);
+int cifs_update_super_prepath(struct cifs_sb_info *cifs_sb, char *prefix);
 char *extract_hostname(const char *unc);
 char *extract_sharename(const char *unc);
 
@@ -634,4 +634,7 @@ static inline int cifs_create_options(struct cifs_sb_info *cifs_sb, int options)
 		return options;
 }
 
+struct super_block *cifs_get_tcon_super(struct cifs_tcon *tcon);
+void cifs_put_tcon_super(struct super_block *sb);
+
 #endif			/* _CIFSPROTO_H */
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 6278a90cb027..1ace46e3f16f 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -61,6 +61,20 @@ extern bool disable_legacy_dialects;
 /* Drop the connection to not overload the server */
 #define NUM_STATUS_IO_TIMEOUT   5
 
+struct mount_ctx {
+	struct cifs_sb_info *cifs_sb;
+	struct smb3_fs_context *fs_ctx;
+	unsigned int xid;
+	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 int ip_connect(struct TCP_Server_Info *server);
 static int generic_ip_connect(struct TCP_Server_Info *server);
 static void tlink_rb_insert(struct rb_root *root, struct tcon_link *new_tlink);
@@ -297,14 +311,68 @@ static int __cifs_reconnect(struct TCP_Server_Info *server)
 }
 
 #ifdef CONFIG_CIFS_DFS_UPCALL
-static int reconnect_dfs_server(struct TCP_Server_Info *server, struct cifs_sb_info *cifs_sb)
+static int __reconnect_target_unlocked(struct TCP_Server_Info *server, const char *target)
+{
+	int rc;
+	char *hostname;
+
+	if (!cifs_swn_set_server_dstaddr(server)) {
+		if (server->hostname != target) {
+			hostname = extract_hostname(target);
+			if (!IS_ERR(hostname)) {
+				kfree(server->hostname);
+				server->hostname = hostname;
+			} else {
+				cifs_dbg(FYI, "%s: couldn't extract hostname or address from dfs target: %ld\n",
+					 __func__, PTR_ERR(hostname));
+				cifs_dbg(FYI, "%s: default to last target server: %s\n", __func__,
+					 server->hostname);
+			}
+		}
+		/* resolve the hostname again to make sure that IP address is up-to-date. */
+		rc = reconn_set_ipaddr_from_hostname(server);
+		cifs_dbg(FYI, "%s: reconn_set_ipaddr_from_hostname: rc=%d\n", __func__, rc);
+	}
+	/* Reconnect the socket */
+	if (cifs_rdma_enabled(server))
+		rc = smbd_reconnect(server);
+	else
+		rc = generic_ip_connect(server);
+
+	return rc;
+}
+
+static int reconnect_target_unlocked(struct TCP_Server_Info *server, struct dfs_cache_tgt_list *tl,
+				     struct dfs_cache_tgt_iterator **target_hint)
+{
+	int rc;
+	struct dfs_cache_tgt_iterator *tit;
+
+	*target_hint = NULL;
+
+	/* If dfs target list is empty, then reconnect to last server */
+	tit = dfs_cache_get_tgt_iterator(tl);
+	if (!tit)
+		return __reconnect_target_unlocked(server, server->hostname);
+
+	/* Otherwise, try every dfs target in @tl */
+	for (; tit; tit = dfs_cache_get_next_tgt(tl, tit)) {
+		rc = __reconnect_target_unlocked(server, dfs_cache_get_tgt_name(tit));
+		if (!rc) {
+			*target_hint = tit;
+			break;
+		}
+	}
+	return rc;
+}
+
+static int reconnect_dfs_server(struct TCP_Server_Info *server)
 {
 	int rc = 0;
-	const char *refpath = cifs_sb->origin_fullpath + 1;
+	const char *refpath = server->current_fullpath + 1;
 	struct dfs_cache_tgt_list tl = DFS_CACHE_TGT_LIST_INIT(tl);
-	struct dfs_cache_tgt_iterator *tit = NULL;
-	int num_targets = 1;
-	char *hostname;
+	struct dfs_cache_tgt_iterator *target_hint = NULL;
+	int num_targets = 0;
 
 	/*
 	 * Determine the number of dfs targets the referral path in @cifs_sb resolves to.
@@ -314,11 +382,10 @@ static int reconnect_dfs_server(struct TCP_Server_Info *server, struct cifs_sb_i
 	 * through /proc/fs/cifs/dfscache or the target list is empty due to server settings after
 	 * refreshing the referral, so, in this case, default it to 1.
 	 */
-	if (!dfs_cache_noreq_find(refpath, NULL, &tl)) {
+	if (!dfs_cache_noreq_find(refpath, NULL, &tl))
 		num_targets = dfs_cache_get_nr_tgts(&tl);
-		if (!num_targets)
-			num_targets = 1;
-	}
+	if (!num_targets)
+		num_targets = 1;
 
 	if (!cifs_tcp_ses_needs_reconnect(server, num_targets))
 		return 0;
@@ -326,51 +393,17 @@ static int reconnect_dfs_server(struct TCP_Server_Info *server, struct cifs_sb_i
 	cifs_mark_tcp_ses_conns_for_reconnect(server);
 
 	do {
-		/* Get next dfs target from target list (if any) */
-		if (!tit)
-			tit = dfs_cache_get_tgt_iterator(&tl);
-		else
-			tit = dfs_cache_get_next_tgt(&tl, tit);
-
 		try_to_freeze();
 		mutex_lock(&server->srv_mutex);
 
-		if (!cifs_swn_set_server_dstaddr(server)) {
-			/*
-			 * If any dfs target was selected, then update @server with either a
-			 * hostname or an address.
-			 */
-			if (tit) {
-				hostname = extract_hostname(dfs_cache_get_tgt_name(tit));
-				if (!IS_ERR(hostname)) {
-					kfree(server->hostname);
-					server->hostname = hostname;
-				} else {
-					cifs_dbg(FYI, "%s: couldn't extract hostname or address from dfs target: %ld\n",
-						 __func__, PTR_ERR(hostname));
-					cifs_dbg(FYI, "%s: default to last target server: %s\n",
-						 __func__, server->hostname);
-				}
-			}
-			/* resolve the hostname again to make sure that IP address is up-to-date. */
-			rc = reconn_set_ipaddr_from_hostname(server);
-			cifs_dbg(FYI, "%s: reconn_set_ipaddr_from_hostname: rc=%d\n", __func__, rc);
-		}
-
-		/* Reconnect the socket */
-		if (cifs_rdma_enabled(server))
-			rc = smbd_reconnect(server);
-		else
-			rc = generic_ip_connect(server);
-
+		rc = reconnect_target_unlocked(server, &tl, &target_hint);
 		if (rc) {
-			/* Failed to reconnect socket.  Retry next dfs target. */
+			/* Failed to reconnect socket */
 			mutex_unlock(&server->srv_mutex);
 			cifs_dbg(FYI, "%s: reconnect error %d\n", __func__, rc);
 			msleep(3000);
 			continue;
 		}
-
 		/*
 		 * Socket was created.  Update tcp session status to CifsNeedNegotiate so that a
 		 * process waiting for reconnect will know it needs to re-establish session and tcon
@@ -386,8 +419,8 @@ static int reconnect_dfs_server(struct TCP_Server_Info *server, struct cifs_sb_i
 		mutex_unlock(&server->srv_mutex);
 	} while (server->tcpStatus == CifsNeedReconnect);
 
-	if (tit)
-		dfs_cache_noreq_update_tgthint(refpath, tit);
+	if (target_hint)
+		dfs_cache_noreq_update_tgthint(refpath, target_hint);
 
 	dfs_cache_free_tgts(&tl);
 
@@ -401,38 +434,15 @@ static int reconnect_dfs_server(struct TCP_Server_Info *server, struct cifs_sb_i
 
 int cifs_reconnect(struct TCP_Server_Info *server)
 {
-	int rc;
-	struct super_block *sb;
-	struct cifs_sb_info *cifs_sb;
-
-	/*
-	 * If tcp session is not an dfs connection or it is a channel, then reconnect to last target
-	 * server.
-	 */
+	/* If tcp session is not an dfs connection, then reconnect to last target server */
 	spin_lock(&cifs_tcp_ses_lock);
-	if (!server->is_dfs_conn || server->is_channel) {
+	if (!server->is_dfs_conn || !server->origin_fullpath || !server->leaf_fullpath) {
 		spin_unlock(&cifs_tcp_ses_lock);
 		return __cifs_reconnect(server);
 	}
 	spin_unlock(&cifs_tcp_ses_lock);
 
-	/* If no superblock, then it might be an ipc connection */
-	sb = cifs_get_tcp_super(server);
-	if (IS_ERR(sb))
-		return __cifs_reconnect(server);
-
-	/*
-	 * Check for a referral path to look up in superblock.  If unset, then simply reconnect to
-	 * last target server.
-	 */
-	cifs_sb = CIFS_SB(sb);
-	if (!cifs_sb->origin_fullpath || !cifs_sb->origin_fullpath[0])
-		rc = __cifs_reconnect(server);
-	else
-		rc = reconnect_dfs_server(server, cifs_sb);
-
-	cifs_put_tcp_super(sb);
-	return rc;
+	return reconnect_dfs_server(server);
 }
 #else
 int cifs_reconnect(struct TCP_Server_Info *server)
@@ -828,6 +838,10 @@ static void clean_demultiplex_info(struct TCP_Server_Info *server)
 		 */
 	}
 
+#ifdef CONFIG_CIFS_DFS_UPCALL
+	kfree(server->origin_fullpath);
+	kfree(server->leaf_fullpath);
+#endif
 	kfree(server);
 
 	length = atomic_dec_return(&tcpSesAllocCount);
@@ -1443,6 +1457,9 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx)
 	INIT_DELAYED_WORK(&tcp_ses->resolve, cifs_resolve_server);
 	INIT_DELAYED_WORK(&tcp_ses->reconnect, smb2_reconnect_server);
 	mutex_init(&tcp_ses->reconnect_mutex);
+#ifdef CONFIG_CIFS_DFS_UPCALL
+	mutex_init(&tcp_ses->refpath_lock);
+#endif
 	memcpy(&tcp_ses->srcaddr, &ctx->srcaddr,
 	       sizeof(tcp_ses->srcaddr));
 	memcpy(&tcp_ses->dstaddr, &ctx->dstaddr,
@@ -2895,73 +2912,64 @@ int cifs_setup_cifs_sb(struct cifs_sb_info *cifs_sb)
 }
 
 /* Release all succeed connections */
-static inline void mount_put_conns(struct cifs_sb_info *cifs_sb,
-				   unsigned int xid,
-				   struct TCP_Server_Info *server,
-				   struct cifs_ses *ses, struct cifs_tcon *tcon)
+static inline void mount_put_conns(struct mount_ctx *mnt_ctx)
 {
 	int rc = 0;
 
-	if (tcon)
-		cifs_put_tcon(tcon);
-	else if (ses)
-		cifs_put_smb_ses(ses);
-	else if (server)
-		cifs_put_tcp_session(server, 0);
-	cifs_sb->mnt_cifs_flags &= ~CIFS_MOUNT_POSIX_PATHS;
-	free_xid(xid);
+	if (mnt_ctx->tcon)
+		cifs_put_tcon(mnt_ctx->tcon);
+	else if (mnt_ctx->ses)
+		cifs_put_smb_ses(mnt_ctx->ses);
+	else if (mnt_ctx->server)
+		cifs_put_tcp_session(mnt_ctx->server, 0);
+	mnt_ctx->cifs_sb->mnt_cifs_flags &= ~CIFS_MOUNT_POSIX_PATHS;
+	free_xid(mnt_ctx->xid);
 }
 
 /* Get connections for tcp, ses and tcon */
-static int mount_get_conns(struct smb3_fs_context *ctx, struct cifs_sb_info *cifs_sb,
-			   unsigned int *xid,
-			   struct TCP_Server_Info **nserver,
-			   struct cifs_ses **nses, struct cifs_tcon **ntcon)
+static int mount_get_conns(struct mount_ctx *mnt_ctx)
 {
 	int rc = 0;
-	struct TCP_Server_Info *server;
-	struct cifs_ses *ses;
-	struct cifs_tcon *tcon;
-
-	*nserver = NULL;
-	*nses = NULL;
-	*ntcon = NULL;
+	struct TCP_Server_Info *server = NULL;
+	struct cifs_ses *ses = NULL;
+	struct cifs_tcon *tcon = NULL;
+	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
+	struct cifs_sb_info *cifs_sb = mnt_ctx->cifs_sb;
+	unsigned int xid;
 
-	*xid = get_xid();
+	xid = get_xid();
 
 	/* get a reference to a tcp session */
 	server = cifs_get_tcp_session(ctx);
 	if (IS_ERR(server)) {
 		rc = PTR_ERR(server);
-		return rc;
+		server = NULL;
+		goto out;
 	}
 
-	*nserver = server;
-
 	/* get a reference to a SMB session */
 	ses = cifs_get_smb_ses(server, ctx);
 	if (IS_ERR(ses)) {
 		rc = PTR_ERR(ses);
-		return rc;
+		ses = NULL;
+		goto out;
 	}
 
-	*nses = ses;
-
 	if ((ctx->persistent == true) && (!(ses->server->capabilities &
 					    SMB2_GLOBAL_CAP_PERSISTENT_HANDLES))) {
 		cifs_server_dbg(VFS, "persistent handles not supported by server\n");
-		return -EOPNOTSUPP;
+		rc = -EOPNOTSUPP;
+		goto out;
 	}
 
 	/* search for existing tcon to this server share */
 	tcon = cifs_get_tcon(ses, ctx);
 	if (IS_ERR(tcon)) {
 		rc = PTR_ERR(tcon);
-		return rc;
+		tcon = NULL;
+		goto out;
 	}
 
-	*ntcon = tcon;
-
 	/* if new SMB3.11 POSIX extensions are supported do not remap / and \ */
 	if (tcon->posix_extensions)
 		cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_POSIX_PATHS;
@@ -2972,17 +2980,19 @@ static int mount_get_conns(struct smb3_fs_context *ctx, struct cifs_sb_info *cif
 		 * reset of caps checks mount to see if unix extensions disabled
 		 * for just this mount.
 		 */
-		reset_cifs_unix_caps(*xid, tcon, cifs_sb, ctx);
+		reset_cifs_unix_caps(xid, tcon, cifs_sb, ctx);
 		if ((tcon->ses->server->tcpStatus == CifsNeedReconnect) &&
 		    (le64_to_cpu(tcon->fsUnixInfo.Capability) &
-		     CIFS_UNIX_TRANSPORT_ENCRYPTION_MANDATORY_CAP))
-			return -EACCES;
+		     CIFS_UNIX_TRANSPORT_ENCRYPTION_MANDATORY_CAP)) {
+			rc = -EACCES;
+			goto out;
+		}
 	} else
 		tcon->unix_ext = 0; /* server does not support them */
 
 	/* do not care if a following call succeed - informational */
 	if (!tcon->pipe && server->ops->qfs_tcon) {
-		server->ops->qfs_tcon(*xid, tcon, cifs_sb);
+		server->ops->qfs_tcon(xid, tcon, cifs_sb);
 		if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_RO_CACHE) {
 			if (tcon->fsDevInfo.DeviceCharacteristics &
 			    cpu_to_le32(FILE_READ_ONLY_DEVICE))
@@ -3006,7 +3016,13 @@ static int mount_get_conns(struct smb3_fs_context *ctx, struct cifs_sb_info *cif
 	    (cifs_sb->ctx->rsize > server->ops->negotiate_rsize(tcon, ctx)))
 		cifs_sb->ctx->rsize = server->ops->negotiate_rsize(tcon, ctx);
 
-	return 0;
+out:
+	mnt_ctx->server = server;
+	mnt_ctx->ses = ses;
+	mnt_ctx->tcon = tcon;
+	mnt_ctx->xid = xid;
+
+	return rc;
 }
 
 static int mount_setup_tlink(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses,
@@ -3036,18 +3052,17 @@ static int mount_setup_tlink(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses,
 }
 
 #ifdef CONFIG_CIFS_DFS_UPCALL
-static int mount_get_dfs_conns(struct smb3_fs_context *ctx, struct cifs_sb_info *cifs_sb,
-			       unsigned int *xid, struct TCP_Server_Info **nserver,
-			       struct cifs_ses **nses, struct cifs_tcon **ntcon)
+/* Get unique dfs connections */
+static int mount_get_dfs_conns(struct mount_ctx *mnt_ctx)
 {
 	int rc;
 
-	ctx->nosharesock = true;
-	rc = mount_get_conns(ctx, cifs_sb, xid, nserver, nses, ntcon);
-	if (*nserver) {
+	mnt_ctx->fs_ctx->nosharesock = true;
+	rc = mount_get_conns(mnt_ctx);
+	if (mnt_ctx->server) {
 		cifs_dbg(FYI, "%s: marking tcp session as a dfs connection\n", __func__);
 		spin_lock(&cifs_tcp_ses_lock);
-		(*nserver)->is_dfs_conn = true;
+		mnt_ctx->server->is_dfs_conn = true;
 		spin_unlock(&cifs_tcp_ses_lock);
 	}
 	return rc;
@@ -3089,190 +3104,38 @@ build_unc_path_to_root(const struct smb3_fs_context *ctx,
 }
 
 /*
- * expand_dfs_referral - Perform a dfs referral query and update the cifs_sb
+ * expand_dfs_referral - Update cifs_sb from dfs referral path
  *
- * If a referral is found, cifs_sb->ctx->mount_options will be (re-)allocated
- * to a string containing updated options for the submount.  Otherwise it
- * will be left untouched.
- *
- * Returns the rc from get_dfs_path to the caller, which can be used to
- * determine whether there were referrals.
+ * cifs_sb->ctx->mount_options will be (re-)allocated to a string containing updated options for the
+ * submount.  Otherwise it will be left untouched.
  */
-static int
-expand_dfs_referral(const unsigned int xid, struct cifs_ses *ses,
-		    struct smb3_fs_context *ctx, struct cifs_sb_info *cifs_sb,
-		    char *ref_path)
+static int expand_dfs_referral(struct mount_ctx *mnt_ctx, const char *full_path,
+			       struct dfs_info3_param *referral)
 {
 	int rc;
-	struct dfs_info3_param referral = {0};
-	char *full_path = NULL, *mdata = NULL;
-
-	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS)
-		return -EREMOTE;
-
-	full_path = build_unc_path_to_root(ctx, cifs_sb, true);
-	if (IS_ERR(full_path))
-		return PTR_ERR(full_path);
-
-	rc = dfs_cache_find(xid, ses, cifs_sb->local_nls, cifs_remap(cifs_sb),
-			    ref_path, &referral, NULL);
-	if (!rc) {
-		char *fake_devname = NULL;
-
-		mdata = cifs_compose_mount_options(cifs_sb->ctx->mount_options,
-						   full_path + 1, &referral,
-						   &fake_devname);
-		free_dfs_info_param(&referral);
-
-		if (IS_ERR(mdata)) {
-			rc = PTR_ERR(mdata);
-			mdata = NULL;
-		} else {
-			/*
-			 * We can not clear out the whole structure since we
-			 * no longer have an explicit function to parse
-			 * a mount-string. Instead we need to clear out the
-			 * individual fields that are no longer valid.
-			 */
-			kfree(ctx->prepath);
-			ctx->prepath = NULL;
-			rc = cifs_setup_volume_info(ctx, mdata, fake_devname);
-		}
-		kfree(fake_devname);
-		kfree(cifs_sb->ctx->mount_options);
-		cifs_sb->ctx->mount_options = mdata;
-	}
-	kfree(full_path);
-	return rc;
-}
-
-static int get_next_dfs_tgt(struct dfs_cache_tgt_list *tgt_list,
-			    struct dfs_cache_tgt_iterator **tgt_it)
-{
-	if (!*tgt_it)
-		*tgt_it = dfs_cache_get_tgt_iterator(tgt_list);
-	else
-		*tgt_it = dfs_cache_get_next_tgt(tgt_list, *tgt_it);
-	return !*tgt_it ? -EHOSTDOWN : 0;
-}
-
-static int update_vol_info(const struct dfs_cache_tgt_iterator *tgt_it,
-			   struct smb3_fs_context *fake_ctx, struct smb3_fs_context *ctx)
-{
-	const char *tgt = dfs_cache_get_tgt_name(tgt_it);
-	int len = strlen(tgt) + 2;
-	char *new_unc;
-
-	new_unc = kmalloc(len, GFP_KERNEL);
-	if (!new_unc)
-		return -ENOMEM;
-	scnprintf(new_unc, len, "\\%s", tgt);
-
-	kfree(ctx->UNC);
-	ctx->UNC = new_unc;
-
-	if (fake_ctx->prepath) {
-		kfree(ctx->prepath);
-		ctx->prepath = fake_ctx->prepath;
-		fake_ctx->prepath = NULL;
-	}
-	memcpy(&ctx->dstaddr, &fake_ctx->dstaddr, sizeof(ctx->dstaddr));
-
-	return 0;
-}
-
-static int do_dfs_failover(const char *path, const char *full_path, struct cifs_sb_info *cifs_sb,
-			   struct smb3_fs_context *ctx, struct cifs_ses *root_ses,
-			   unsigned int *xid, struct TCP_Server_Info **server,
-			   struct cifs_ses **ses, struct cifs_tcon **tcon)
-{
-	int rc;
-	char *npath = NULL;
-	struct dfs_cache_tgt_list tgt_list = DFS_CACHE_TGT_LIST_INIT(tgt_list);
-	struct dfs_cache_tgt_iterator *tgt_it = NULL;
-	struct smb3_fs_context tmp_ctx = {NULL};
-
-	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS)
-		return -EOPNOTSUPP;
-
-	npath = dfs_cache_canonical_path(path, cifs_sb->local_nls, cifs_remap(cifs_sb));
-	if (IS_ERR(npath))
-		return PTR_ERR(npath);
-
-	cifs_dbg(FYI, "%s: path=%s full_path=%s\n", __func__, npath, full_path);
-
-	rc = dfs_cache_noreq_find(npath, NULL, &tgt_list);
-	if (rc)
-		goto out;
-	/*
-	 * We use a 'tmp_ctx' here because we need pass it down to the mount_{get,put} functions to
-	 * test connection against new DFS targets.
-	 */
-	rc = smb3_fs_context_dup(&tmp_ctx, ctx);
-	if (rc)
-		goto out;
-
-	for (;;) {
-		struct dfs_info3_param ref = {0};
-		char *fake_devname = NULL, *mdata = NULL;
-
-		/* Get next DFS target server - if any */
-		rc = get_next_dfs_tgt(&tgt_list, &tgt_it);
-		if (rc)
-			break;
-
-		rc = dfs_cache_get_tgt_referral(npath, tgt_it, &ref);
-		if (rc)
-			break;
-
-		cifs_dbg(FYI, "%s: old ctx: UNC=%s prepath=%s\n", __func__, tmp_ctx.UNC,
-			 tmp_ctx.prepath);
-
-		mdata = cifs_compose_mount_options(cifs_sb->ctx->mount_options, full_path + 1, &ref,
-						   &fake_devname);
-		free_dfs_info_param(&ref);
-
-		if (IS_ERR(mdata)) {
-			rc = PTR_ERR(mdata);
-			mdata = NULL;
-		} else
-			rc = cifs_setup_volume_info(&tmp_ctx, mdata, fake_devname);
-
-		kfree(mdata);
-		kfree(fake_devname);
-
-		if (rc)
-			break;
-
-		cifs_dbg(FYI, "%s: new ctx: UNC=%s prepath=%s\n", __func__, tmp_ctx.UNC,
-			 tmp_ctx.prepath);
-
-		mount_put_conns(cifs_sb, *xid, *server, *ses, *tcon);
-		rc = mount_get_dfs_conns(&tmp_ctx, cifs_sb, xid, server, ses, tcon);
-		if (!rc || (*server && *ses)) {
-			/*
-			 * We were able to connect to new target server. Update current context with
-			 * new target server.
-			 */
-			rc = update_vol_info(tgt_it, &tmp_ctx, ctx);
-			break;
-		}
-	}
-	if (!rc) {
-		cifs_dbg(FYI, "%s: final ctx: UNC=%s prepath=%s\n", __func__, tmp_ctx.UNC,
-			 tmp_ctx.prepath);
+	struct cifs_sb_info *cifs_sb = mnt_ctx->cifs_sb;
+	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
+	char *fake_devname = NULL, *mdata = NULL;
+
+	mdata = cifs_compose_mount_options(cifs_sb->ctx->mount_options, full_path + 1, referral,
+					   &fake_devname);
+	if (IS_ERR(mdata)) {
+		rc = PTR_ERR(mdata);
+		mdata = NULL;
+	} else {
 		/*
-		 * Update DFS target hint in DFS referral cache with the target server we
-		 * successfully reconnected to.
+		 * We can not clear out the whole structure since we no longer have an explicit
+		 * function to parse a mount-string. Instead we need to clear out the individual
+		 * fields that are no longer valid.
 		 */
-		rc = dfs_cache_update_tgthint(*xid, root_ses ? root_ses : *ses, cifs_sb->local_nls,
-					      cifs_remap(cifs_sb), path, tgt_it);
+		kfree(ctx->prepath);
+		ctx->prepath = NULL;
+		rc = cifs_setup_volume_info(ctx, mdata, fake_devname);
 	}
+	kfree(fake_devname);
+	kfree(cifs_sb->ctx->mount_options);
+	cifs_sb->ctx->mount_options = mdata;
 
-out:
-	kfree(npath);
-	smb3_cleanup_fs_context_contents(&tmp_ctx);
-	dfs_cache_free_tgts(&tgt_list);
 	return rc;
 }
 #endif
@@ -3379,12 +3242,14 @@ cifs_are_all_path_components_accessible(struct TCP_Server_Info *server,
  * Check if path is remote (e.g. a DFS share). Return -EREMOTE if it is,
  * otherwise 0.
  */
-static int is_path_remote(struct cifs_sb_info *cifs_sb, struct smb3_fs_context *ctx,
-			  const unsigned int xid,
-			  struct TCP_Server_Info *server,
-			  struct cifs_tcon *tcon)
+static int is_path_remote(struct mount_ctx *mnt_ctx)
 {
 	int rc;
+	struct cifs_sb_info *cifs_sb = mnt_ctx->cifs_sb;
+	struct TCP_Server_Info *server = mnt_ctx->server;
+	unsigned int xid = mnt_ctx->xid;
+	struct cifs_tcon *tcon = mnt_ctx->tcon;
+	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
 	char *full_path;
 
 	if (!server->ops->is_path_accessible)
@@ -3422,280 +3287,289 @@ static int is_path_remote(struct cifs_sb_info *cifs_sb, struct smb3_fs_context *
 }
 
 #ifdef CONFIG_CIFS_DFS_UPCALL
-static void set_root_ses(struct cifs_sb_info *cifs_sb, const uuid_t *mount_id, struct cifs_ses *ses,
-			 struct cifs_ses **root_ses)
+static void set_root_ses(struct mount_ctx *mnt_ctx)
 {
-	if (ses) {
+	if (mnt_ctx->ses) {
 		spin_lock(&cifs_tcp_ses_lock);
-		ses->ses_count++;
+		mnt_ctx->ses->ses_count++;
 		spin_unlock(&cifs_tcp_ses_lock);
-		dfs_cache_add_refsrv_session(mount_id, ses);
+		dfs_cache_add_refsrv_session(&mnt_ctx->mount_id, mnt_ctx->ses);
 	}
-	*root_ses = ses;
+	mnt_ctx->root_ses = mnt_ctx->ses;
 }
 
-/* Set up next dfs prefix path in @dfs_path */
-static int next_dfs_prepath(struct cifs_sb_info *cifs_sb, struct smb3_fs_context *ctx,
-			    const unsigned int xid, struct TCP_Server_Info *server,
-			    struct cifs_tcon *tcon, char **dfs_path)
+static int is_dfs_mount(struct mount_ctx *mnt_ctx, bool *isdfs, struct dfs_cache_tgt_list *root_tl)
 {
-	char *path, *npath;
-	int added_treename = is_tcon_dfs(tcon);
 	int rc;
+	struct cifs_sb_info *cifs_sb = mnt_ctx->cifs_sb;
+	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
 
-	path = cifs_build_path_to_root(ctx, cifs_sb, tcon, added_treename);
-	if (!path)
-		return -ENOMEM;
+	*isdfs = true;
 
-	rc = is_path_remote(cifs_sb, ctx, xid, server, tcon);
-	if (rc == -EREMOTE) {
-		struct smb3_fs_context v = {NULL};
-		/* if @path contains a tree name, skip it in the prefix path */
-		if (added_treename) {
-			rc = smb3_parse_devname(path, &v);
-			if (rc)
-				goto out;
-			npath = build_unc_path_to_root(&v, cifs_sb, true);
-			smb3_cleanup_fs_context_contents(&v);
-		} else {
-			v.UNC = ctx->UNC;
-			v.prepath = path + 1;
-			npath = build_unc_path_to_root(&v, cifs_sb, true);
-		}
+	rc = mount_get_conns(mnt_ctx);
+	/*
+	 * If called with 'nodfs' mount option, then skip DFS resolving.  Otherwise unconditionally
+	 * try to get an DFS referral (even cached) to determine whether it is an DFS mount.
+	 *
+	 * Skip prefix path to provide support for DFS referrals from w2k8 servers which don't seem
+	 * to respond with PATH_NOT_COVERED to requests that include the prefix.
+	 */
+	if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS) ||
+	    dfs_cache_find(mnt_ctx->xid, mnt_ctx->ses, cifs_sb->local_nls, cifs_remap(cifs_sb),
+			   ctx->UNC + 1, NULL, root_tl)) {
+		if (rc)
+			return rc;
+		/* Check if it is fully accessible and then mount it */
+		rc = is_path_remote(mnt_ctx);
+		if (!rc)
+			*isdfs = false;
+		else if (rc != -EREMOTE)
+			return rc;
+	}
+	return 0;
+}
 
-		if (IS_ERR(npath)) {
-			rc = PTR_ERR(npath);
-			goto out;
-		}
+static int connect_dfs_target(struct mount_ctx *mnt_ctx, const char *full_path,
+			      const char *ref_path, struct dfs_cache_tgt_iterator *tit)
+{
+	int rc;
+	struct dfs_info3_param ref = {};
+	struct cifs_sb_info *cifs_sb = mnt_ctx->cifs_sb;
+	char *oldmnt = cifs_sb->ctx->mount_options;
 
-		kfree(*dfs_path);
-		*dfs_path = npath;
-		rc = -EREMOTE;
+	rc = dfs_cache_get_tgt_referral(ref_path, tit, &ref);
+	if (rc)
+		goto out;
+
+	rc = expand_dfs_referral(mnt_ctx, full_path, &ref);
+	if (rc)
+		goto out;
+
+	/* Connect to new target only if we were redirected (e.g. mount options changed) */
+	if (oldmnt != cifs_sb->ctx->mount_options) {
+		mount_put_conns(mnt_ctx);
+		rc = mount_get_dfs_conns(mnt_ctx);
+	}
+	if (!rc) {
+		if (cifs_is_referral_server(mnt_ctx->tcon, &ref))
+			set_root_ses(mnt_ctx);
+		rc = dfs_cache_update_tgthint(mnt_ctx->xid, mnt_ctx->root_ses, cifs_sb->local_nls,
+					      cifs_remap(cifs_sb), ref_path, tit);
 	}
 
 out:
-	kfree(path);
+	free_dfs_info_param(&ref);
 	return rc;
 }
 
-/* Check if resolved targets can handle any DFS referrals */
-static int is_referral_server(const char *ref_path, struct cifs_sb_info *cifs_sb,
-			      struct cifs_tcon *tcon, bool *ref_server)
+static int connect_dfs_root(struct mount_ctx *mnt_ctx, struct dfs_cache_tgt_list *root_tl)
 {
 	int rc;
-	struct dfs_info3_param ref = {0};
+	char *full_path;
+	struct cifs_sb_info *cifs_sb = mnt_ctx->cifs_sb;
+	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;