cifs: disable sharing session and tcon and add new TCP sharing code

The code that allows these structs to be shared is extremely racy.
Disable the sharing of SMB and tcon structs for now until we can
come up with a way to do this that's race free.

We want to continue to share TCP sessions, however since they are
required for multiuser mounts. For that, implement a new (hopefully
race-free) scheme. Add a new global list of TCP sessions, and take
care to get a reference to it whenever we're dealing with one.

Signed-off-by: Jeff Layton <[e-mail]>
Signed-off-by: Steve French <[e-mail]>

fs/cifs/cifs_debug.c

···
 			seq_printf(m, "TCP status: %d\n\tLocal Users To "
 				    "Server: %d SecMode: 0x%x Req On Wire: %d",
 				ses->server->tcpStatus,
-				atomic_read(&ses->server->socketUseCount),
+				ses->server->srv_count,
 				ses->server->secMode,
 				atomic_read(&ses->server->inFlight));
 

fs/cifs/cifsfs.c

···
 {
 	int rc = 0;
 	cifs_proc_init();
-	INIT_LIST_HEAD(&global_cifs_sock_list);
+	INIT_LIST_HEAD(&cifs_tcp_ses_list);
 	INIT_LIST_HEAD(&GlobalSMBSessionList); /* BB to be removed by jl */
 	INIT_LIST_HEAD(&GlobalTreeConnectionList); /* BB to be removed by jl */
 	INIT_LIST_HEAD(&GlobalOplock_Q);
···
 	GlobalMaxActiveXid = 0;
 	memset(Local_System_Name, 0, 15);
 	rwlock_init(&GlobalSMBSeslock);
+	rwlock_init(&cifs_tcp_ses_lock);
 	spin_lock_init(&GlobalMid_Lock);
 
 	if (cifs_max_pending < 2) {

fs/cifs/cifsglob.h

···
 struct TCP_Server_Info {
 	struct list_head tcp_ses_list;
 	struct list_head smb_ses_list;
+	int srv_count; /* reference counter */
 	/* 15 character server name + 0x20 16th byte indicating type = srv */
 	char server_RFC1001_name[SERVER_NAME_LEN_WITH_NULL];
 	char unicode_server_Name[SERVER_NAME_LEN_WITH_NULL * 2];
···
 	bool svlocal:1;			/* local server or remote */
 	bool noblocksnd;		/* use blocking sendmsg */
 	bool noautotune;		/* do not autotune send buf sizes */
-	atomic_t socketUseCount; /* number of open cifs sessions on socket */
 	atomic_t inFlight;  /* number of requests on the wire to server */
 #ifdef CONFIG_CIFS_STATS2
 	atomic_t inSend; /* requests trying to send */
···
 #define GLOBAL_EXTERN extern
 #endif
 
-
-/* the list of TCP_Server_Info structures, ie each of the sockets
+/*
+ * the list of TCP_Server_Info structures, ie each of the sockets
  * connecting our client to a distinct server (ip address), is
- * chained together by global_cifs_sock_list. The list of all our SMB
+ * chained together by cifs_tcp_ses_list. The list of all our SMB
  * sessions (and from that the tree connections) can be found
- * by iterating over global_cifs_sock_list */
-GLOBAL_EXTERN struct list_head global_cifs_sock_list;
+ * by iterating over cifs_tcp_ses_list
+ */
+GLOBAL_EXTERN struct list_head		cifs_tcp_ses_list;
+
+/* protects cifs_tcp_ses_list and srv_count for each tcp session */
+GLOBAL_EXTERN rwlock_t		cifs_tcp_ses_lock;
+
 GLOBAL_EXTERN struct list_head GlobalSMBSessionList; /* BB to be removed by jl*/
 GLOBAL_EXTERN struct list_head GlobalTreeConnectionList; /* BB to be removed */
 GLOBAL_EXTERN rwlock_t GlobalSMBSeslock;  /* protects list inserts on 3 above */

fs/cifs/cifsproto.h

···
 			    const __u16 *pfid);
 extern int mode_to_acl(struct inode *inode, const char *path, __u64);
 
+extern void cifs_put_tcp_session(struct TCP_Server_Info *server);
 extern int cifs_mount(struct super_block *, struct cifs_sb_info *, char *,
 			const char *);
 extern int cifs_umount(struct super_block *, struct cifs_sb_info *);

fs/cifs/cifssmb.c

···
 			rc = -EIO;
 			goto neg_err_exit;
 		}
-
-		if (server->socketUseCount.counter > 1) {
+		read_lock(&cifs_tcp_ses_lock);
+		if (server->srv_count > 1) {
+			read_unlock(&cifs_tcp_ses_lock);
 			if (memcmp(server->server_GUID,
 				   pSMBr->u.extended_response.
 				   GUID, 16) != 0) {
···
 					pSMBr->u.extended_response.GUID,
 					16);
 			}
-		} else
+		} else {
+			read_unlock(&cifs_tcp_ses_lock);
 			memcpy(server->server_GUID,
 			       pSMBr->u.extended_response.GUID, 16);
+		}
 
 		if (count == 16) {
 			server->secType = RawNTLMSSP;
···
 	pSMB->AndXCommand = 0xFF;
 	rc = SendReceiveNoRsp(xid, ses, (struct smb_hdr *) pSMB, 0);
 session_already_dead:
-	atomic_dec(&ses->server->socketUseCount);
-	if (atomic_read(&ses->server->socketUseCount) == 0) {
-		spin_lock(&GlobalMid_Lock);
-		ses->server->tcpStatus = CifsExiting;
-		spin_unlock(&GlobalMid_Lock);
-		rc = -ESHUTDOWN;
+	if (ses->server) {
+		cifs_put_tcp_session(ses->server);
+		rc = 0;
 	}
 	up(&ses->sesSem);
 

fs/cifs/connect.c

···
 		}
 	} /* end while !EXITING */
 
+	/* take it off the list, if it's not already */
+	write_lock(&cifs_tcp_ses_lock);
+	list_del_init(&server->tcp_ses_list);
+	write_unlock(&cifs_tcp_ses_lock);
+
 	spin_lock(&GlobalMid_Lock);
 	server->tcpStatus = CifsExiting;
 	spin_unlock(&GlobalMid_Lock);
···
 	return 0;
 }
 
-static struct cifsSesInfo *
-cifs_find_tcp_session(struct in_addr *target_ip_addr,
-		      struct in6_addr *target_ip6_addr,
-		      char *userName, struct TCP_Server_Info **psrvTcp)
+static struct TCP_Server_Info *
+cifs_find_tcp_session(struct sockaddr *addr)
 {
 	struct list_head *tmp;
-	struct cifsSesInfo *ses;
+	struct TCP_Server_Info *server;
+	struct sockaddr_in *addr4 = (struct sockaddr_in *) addr;
+	struct sockaddr_in6 *addr6 = (struct sockaddr_in6 *) addr;
 
-	*psrvTcp = NULL;
+	write_lock(&cifs_tcp_ses_lock);
+	list_for_each(tmp, &cifs_tcp_ses_list) {
+		server = list_entry(tmp, struct TCP_Server_Info,
+				    tcp_ses_list);
 
-	read_lock(&GlobalSMBSeslock);
-	list_for_each(tmp, &GlobalSMBSessionList) {
-		ses = list_entry(tmp, struct cifsSesInfo, cifsSessionList);
-		if (!ses->server)
+		/*
+		 * the demux thread can exit on its own while still in CifsNew
+		 * so don't accept any sockets in that state. Since the
+		 * tcpStatus never changes back to CifsNew it's safe to check
+		 * for this without a lock.
+		 */
+		if (server->tcpStatus == CifsNew)
 			continue;
 
-		if (target_ip_addr &&
-		    ses->server->addr.sockAddr.sin_addr.s_addr != target_ip_addr->s_addr)
-				continue;
-		else if (target_ip6_addr &&
-			 memcmp(&ses->server->addr.sockAddr6.sin6_addr,
-				target_ip6_addr, sizeof(*target_ip6_addr)))
-				continue;
-		/* BB lock server and tcp session; increment use count here?? */
+		if (addr->sa_family == AF_INET &&
+		    (addr4->sin_addr.s_addr !=
+		     server->addr.sockAddr.sin_addr.s_addr))
+			continue;
+		else if (addr->sa_family == AF_INET6 &&
+			 memcmp(&server->addr.sockAddr6.sin6_addr,
+				&addr6->sin6_addr, sizeof(addr6->sin6_addr)))
+			continue;
 
-		/* found a match on the TCP session */
-		*psrvTcp = ses->server;
-
-		/* BB check if reconnection needed */
-		if (strncmp(ses->userName, userName, MAX_USERNAME_SIZE) == 0) {
-			read_unlock(&GlobalSMBSeslock);
-			/* Found exact match on both TCP and
-			   SMB sessions */
-			return ses;
-		}
-		/* else tcp and smb sessions need reconnection */
+		++server->srv_count;
+		write_unlock(&cifs_tcp_ses_lock);
+		return server;
 	}
-	read_unlock(&GlobalSMBSeslock);
-
+	write_unlock(&cifs_tcp_ses_lock);
 	return NULL;
 }
 
-static struct cifsTconInfo *
-find_unc(__be32 new_target_ip_addr, char *uncName, char *userName)
+void
+cifs_put_tcp_session(struct TCP_Server_Info *server)
 {
-	struct list_head *tmp;
-	struct cifsTconInfo *tcon;
-	__be32 old_ip;
+	struct task_struct *task;
 
-	read_lock(&GlobalSMBSeslock);
-
-	list_for_each(tmp, &GlobalTreeConnectionList) {
-		cFYI(1, ("Next tcon"));
-		tcon = list_entry(tmp, struct cifsTconInfo, cifsConnectionList);
-		if (!tcon->ses || !tcon->ses->server)
-			continue;
-
-		old_ip = tcon->ses->server->addr.sockAddr.sin_addr.s_addr;
-		cFYI(1, ("old ip addr: %x == new ip %x ?",
-			old_ip, new_target_ip_addr));
-
-		if (old_ip != new_target_ip_addr)
-			continue;
-
-		/* BB lock tcon, server, tcp session and increment use count? */
-		/* found a match on the TCP session */
-		/* BB check if reconnection needed */
-		cFYI(1, ("IP match, old UNC: %s new: %s",
-			tcon->treeName, uncName));
-
-		if (strncmp(tcon->treeName, uncName, MAX_TREE_SIZE))
-			continue;
-
-		cFYI(1, ("and old usr: %s new: %s",
-			tcon->treeName, uncName));
-
-		if (strncmp(tcon->ses->userName, userName, MAX_USERNAME_SIZE))
-			continue;
-
-		/* matched smb session (user name) */
-		read_unlock(&GlobalSMBSeslock);
-		return tcon;
+	write_lock(&cifs_tcp_ses_lock);
+	if (--server->srv_count > 0) {
+		write_unlock(&cifs_tcp_ses_lock);
+		return;
 	}
 
-	read_unlock(&GlobalSMBSeslock);
-	return NULL;
+	list_del_init(&server->tcp_ses_list);
+	write_unlock(&cifs_tcp_ses_lock);
+
+	spin_lock(&GlobalMid_Lock);
+	server->tcpStatus = CifsExiting;
+	spin_unlock(&GlobalMid_Lock);
+
+	task = xchg(&server->tsk, NULL);
+	if (task)
+		force_sig(SIGKILL, task);
 }
 
 int
···
 	}
 }
 
-static void
-kill_cifsd(struct TCP_Server_Info *server)
-{
-	struct task_struct *task;
-
-	task = xchg(&server->tsk, NULL);
-	if (task)
-		force_sig(SIGKILL, task);
-}
-
 static void setup_cifs_sb(struct smb_vol *pvolume_info,
 			  struct cifs_sb_info *cifs_sb)
 {
···
 		}
 	}
 
-	if (addr.sa_family == AF_INET)
-		existingCifsSes = cifs_find_tcp_session(&sin_server->sin_addr,
-			NULL /* no ipv6 addr */,
-			volume_info.username, &srvTcp);
-	else if (addr.sa_family == AF_INET6) {
-		cFYI(1, ("looking for ipv6 address"));
-		existingCifsSes = cifs_find_tcp_session(NULL /* no ipv4 addr */,
-			&sin_server6->sin6_addr,
-			volume_info.username, &srvTcp);
-	} else {
-		rc = -EINVAL;
-		goto out;
-	}
-
-	if (!srvTcp) {
+	srvTcp = cifs_find_tcp_session(&addr);
+	if (srvTcp) {
+		cFYI(1, ("Existing tcp session with server found"));
+	} else {	/* create socket */
 		if (addr.sa_family == AF_INET6) {
 			cFYI(1, ("attempting ipv6 connect"));
 			/* BB should we allow ipv6 on port 139? */
···
 			memcpy(srvTcp->server_RFC1001_name,
 				volume_info.target_rfc1001_name, 16);
 			srvTcp->sequence_number = 0;
+			INIT_LIST_HEAD(&srvTcp->tcp_ses_list);
+			++srvTcp->srv_count;
+			write_lock(&cifs_tcp_ses_lock);
+			list_add(&srvTcp->tcp_ses_list,
+				 &cifs_tcp_ses_list);
+			write_unlock(&cifs_tcp_ses_lock);
 		}
 	}
 
···
 			rc = cifs_setup_session(xid, pSesInfo,
 						cifs_sb->local_nls);
 			up(&pSesInfo->sesSem);
-			if (!rc)
-				atomic_inc(&srvTcp->socketUseCount);
 		}
 	}
 
···
 	if (!rc) {
 		setup_cifs_sb(&volume_info, cifs_sb);
 
-		tcon =
-		    find_unc(sin_server->sin_addr.s_addr, volume_info.UNC,
-			     volume_info.username);
 		if (tcon) {
 			cFYI(1, ("Found match on UNC path"));
 			if (tcon->seal != volume_info.seal)
···
 /* on error free sesinfo and tcon struct if needed */
 mount_fail_check:
 	if (rc) {
-		/* if session setup failed, use count is zero but
-		we still need to free cifsd thread */
-		if (atomic_read(&srvTcp->socketUseCount) == 0) {
-			spin_lock(&GlobalMid_Lock);
-			srvTcp->tcpStatus = CifsExiting;
-			spin_unlock(&GlobalMid_Lock);
-			kill_cifsd(srvTcp);
-		}
-		 /* If find_unc succeeded then rc == 0 so we can not end */
-		if (tcon)  /* up accidently freeing someone elses tcon struct */
+		/* If find_unc succeeded then rc == 0 so we can not end */
+		/* up accidently freeing someone elses tcon struct */
+		if (tcon)
 			tconInfoFree(tcon);
+
 		if (existingCifsSes == NULL) {
 			if (pSesInfo) {
 				if ((pSesInfo->server) &&
-				    (pSesInfo->status == CifsGood)) {
-					int temp_rc;
-					temp_rc = CIFSSMBLogoff(xid, pSesInfo);
-					/* if the socketUseCount is now zero */
-					if ((temp_rc == -ESHUTDOWN) &&
-					    (pSesInfo->server))
-						kill_cifsd(pSesInfo->server);
-				} else {
+				    (pSesInfo->status == CifsGood))
+					CIFSSMBLogoff(xid, pSesInfo);
+				else {
 					cFYI(1, ("No session or bad tcon"));
-					if (pSesInfo->server) {
-						spin_lock(&GlobalMid_Lock);
-						srvTcp->tcpStatus = CifsExiting;
-						spin_unlock(&GlobalMid_Lock);
-						kill_cifsd(pSesInfo->server);
-					}
+					if (pSesInfo->server)
+						cifs_put_tcp_session(
+							pSesInfo->server);
 				}
 				sesInfoFree(pSesInfo);
 				/* pSesInfo = NULL; */
···
 			if (rc == -EBUSY) {
 				FreeXid(xid);
 				return 0;
-			} else if (rc == -ESHUTDOWN) {
-				cFYI(1, ("Waking up socket by sending signal"));
-				if (ses->server)
-					kill_cifsd(ses->server);
-				rc = 0;
-			} /* else - we have an smb session
-				left on this socket do not kill cifsd */
+			}
 		} else
 			cFYI(1, ("No session or bad tcon"));
 	}