Date:	Wed, 22 Oct 2008 10:14:00 -0400
From:	Jeff Layton <jlayton@...hat.com>
To:	smfrench@...il.com
Cc:	linux-cifs-client@...ts.samba.org, linux-kernel@...r.kernel.org,
	smfrench@...tin.rr.com
Subject: [PATCH 3/4] 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 <jlayton@...hat.com>
---
 fs/cifs/cifs_debug.c |    2 +-
 fs/cifs/cifsfs.c     |    8 ++
 fs/cifs/cifsglob.h   |    5 +-
 fs/cifs/cifsproto.h  |    1 +
 fs/cifs/cifssmb.c    |   14 ++---
 fs/cifs/connect.c    |  192 ++++++++++++++++----------------------------------
 6 files changed, 81 insertions(+), 141 deletions(-)

diff --git a/fs/cifs/cifs_debug.c b/fs/cifs/cifs_debug.c
index 69a12aa..c998751 100644
--- a/fs/cifs/cifs_debug.c
+++ b/fs/cifs/cifs_debug.c
@@ -144,7 +144,7 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v)
 			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->refcount,
 				ses->server->secMode,
 				atomic_read(&ses->server->inFlight));
 
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index c6aad77..306c278 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -91,6 +91,12 @@ extern mempool_t *cifs_mid_poolp;
 
 extern struct kmem_cache *cifs_oplock_cachep;
 
+/* global list of TCP_Server_Info structs */
+struct list_head	cifs_tcp_session_list;
+
+/* protects cifs_tcp_session_list and TCP_Server_Info refcount */
+spinlock_t		cifs_tcp_session_lock;
+
 static int
 cifs_read_super(struct super_block *sb, void *data,
 		const char *devname, int silent)
@@ -1018,6 +1024,7 @@ init_cifs(void)
 	INIT_LIST_HEAD(&GlobalSMBSessionList);
 	INIT_LIST_HEAD(&GlobalTreeConnectionList);
 	INIT_LIST_HEAD(&GlobalOplock_Q);
+	INIT_LIST_HEAD(&cifs_tcp_session_list);
 #ifdef CONFIG_CIFS_EXPERIMENTAL
 	INIT_LIST_HEAD(&GlobalDnotifyReqList);
 	INIT_LIST_HEAD(&GlobalDnotifyRsp_Q);
@@ -1044,6 +1051,7 @@ init_cifs(void)
 	GlobalMaxActiveXid = 0;
 	memset(Local_System_Name, 0, 15);
 	rwlock_init(&GlobalSMBSeslock);
+	spin_lock_init(&cifs_tcp_session_lock);
 	spin_lock_init(&GlobalMid_Lock);
 
 	if (cifs_max_pending < 2) {
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index d45acb5..fdf9fc9 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -115,6 +115,8 @@ struct cifs_cred {
  */
 
 struct TCP_Server_Info {
+	struct list_head tcp_session_list;
+	int refcount; /* 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];
@@ -133,7 +135,6 @@ struct TCP_Server_Info {
 	char versionMajor;
 	char versionMinor;
 	bool svlocal:1;			/* local server or remote */
-	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 */
@@ -592,6 +593,8 @@ GLOBAL_EXTERN struct smbUidInfo *GlobalUidList[UID_HASH];
 GLOBAL_EXTERN struct list_head GlobalSMBSessionList;
 GLOBAL_EXTERN struct list_head GlobalTreeConnectionList;
 GLOBAL_EXTERN rwlock_t GlobalSMBSeslock;  /* protects list inserts on 3 above */
+extern struct list_head		cifs_tcp_session_list;
+extern spinlock_t		cifs_tcp_session_lock;
 
 GLOBAL_EXTERN struct list_head GlobalOplock_Q;
 
diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 0cff7fe..abd4580 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -102,6 +102,7 @@ extern void acl_to_uid_mode(struct inode *inode, const char *path,
 			    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 *);
diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 843a85f..11d3ccc 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -664,8 +664,8 @@ CIFSSMBNegotiate(unsigned int xid, struct cifsSesInfo *ses)
 			rc = -EIO;
 			goto neg_err_exit;
 		}
-
-		if (server->socketUseCount.counter > 1) {
+		spin_lock(&cifs_tcp_session_lock);
+		if (server->refcount > 1) {
 			if (memcmp(server->server_GUID,
 				   pSMBr->u.extended_response.
 				   GUID, 16) != 0) {
@@ -677,6 +677,7 @@ CIFSSMBNegotiate(unsigned int xid, struct cifsSesInfo *ses)
 		} else
 			memcpy(server->server_GUID,
 			       pSMBr->u.extended_response.GUID, 16);
+		spin_unlock(&cifs_tcp_session_lock);
 
 		if (count == 16) {
 			server->secType = RawNTLMSSP;
@@ -825,13 +826,8 @@ CIFSSMBLogoff(const int xid, struct cifsSesInfo *ses)
 	pSMB->AndXCommand = 0xFF;
 	rc = SendReceiveNoRsp(xid, ses, (struct smb_hdr *) pSMB, 0);
 	if (ses->server) {
-		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;
-		}
+		cifs_put_tcp_session(ses->server);
+		rc = 0;
 	}
 	up(&ses->sesSem);
 
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 0b2adef..a1aa90d 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -648,6 +648,11 @@ multi_t2_fnd:
 		}
 	} /* end while !EXITING */
 
+	/* take it off the list, if it's not already */
+	spin_lock(&cifs_tcp_session_lock);
+	list_del_init(&server->tcp_session_list);
+	spin_unlock(&cifs_tcp_session_lock);
+
 	spin_lock(&GlobalMid_Lock);
 	server->tcpStatus = CifsExiting;
 	spin_unlock(&GlobalMid_Lock);
@@ -1338,92 +1343,61 @@ cifs_parse_mount_options(char *options, const char *devname,
 	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;
+	spin_lock(&cifs_tcp_session_lock);
+	list_for_each(tmp, &cifs_tcp_session_list) {
+		server = list_entry(tmp, struct TCP_Server_Info,
+				    tcp_session_list);
 
-	read_lock(&GlobalSMBSeslock);
-	list_for_each(tmp, &GlobalSMBSessionList) {
-		ses = list_entry(tmp, struct cifsSesInfo, cifsSessionList);
-		if (!ses->server)
+		/* Only accept sessions that have done successful negotiate */
+		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?? */
-
-		/* found a match on the TCP session */
-		*psrvTcp = ses->server;
+		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;
 
-		/* 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->refcount;
+		spin_unlock(&cifs_tcp_session_lock);
+		return server;
 	}
-	read_unlock(&GlobalSMBSeslock);
-
+	spin_unlock(&cifs_tcp_session_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;
-
-	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;
+	struct task_struct *task;
 
-		cFYI(1, ("and old usr: %s new: %s",
-			tcon->treeName, uncName));
+	spin_lock(&cifs_tcp_session_lock);
+	if (--server->refcount > 0) {
+		spin_unlock(&cifs_tcp_session_lock);
+		return;
+	}
 
-		if (strncmp(tcon->ses->userName, userName, MAX_USERNAME_SIZE))
-			continue;
+	list_del_init(&server->tcp_session_list);
+	spin_unlock(&cifs_tcp_session_lock);
 
-		/* matched smb session (user name) */
-		read_unlock(&GlobalSMBSeslock);
-		return tcon;
-	}
+	spin_lock(&GlobalMid_Lock);
+	server->tcpStatus = CifsExiting;
+	spin_unlock(&GlobalMid_Lock);
 
-	read_unlock(&GlobalSMBSeslock);
-	return NULL;
+	task = xchg(&server->tsk, NULL);
+	if (task)
+		force_sig(SIGKILL, task);
 }
 
 int
@@ -1852,16 +1826,6 @@ convert_delimiter(char *path, char delim)
 	}
 }
 
-static void
-kill_cifsd(struct TCP_Server_Info *server)
-{
-	struct task_struct *task;
-
-	task = xchg(&server->tsk, NULL);
-	if (task)
-		force_sig(SIGKILL, task);
-}
-
 int
 cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
 	   char *mount_data, const char *devname)
@@ -1953,20 +1917,7 @@ cifs_mount(struct super_block *sb, 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;
-	}
-
+	srvTcp = cifs_find_tcp_session(&addr);
 	if (srvTcp) {
 		cFYI(1, ("Existing tcp session with server found"));
 	} else {	/* create socket */
@@ -2031,6 +1982,12 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
 			memcpy(srvTcp->server_RFC1001_name,
 				volume_info.target_rfc1001_name, 16);
 			srvTcp->sequence_number = 0;
+			INIT_LIST_HEAD(&srvTcp->tcp_session_list);
+			++srvTcp->refcount;
+			spin_lock(&cifs_tcp_session_lock);
+			list_add(&cifs_tcp_session_list,
+						&srvTcp->tcp_session_list);
+			spin_unlock(&cifs_tcp_session_lock);
 		}
 	}
 
@@ -2082,8 +2039,6 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
 			rc = cifs_setup_session(xid, pSesInfo,
 						cifs_sb->local_nls);
 			up(&pSesInfo->sesSem);
-			if (!rc)
-				atomic_inc(&srvTcp->socketUseCount);
 		}
 	}
 
@@ -2171,9 +2126,6 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
 			cERROR(1, ("mount option dynperm ignored if cifsacl "
 				   "mount option supported"));
 
-		tcon =
-		    find_unc(sin_server.sin_addr.s_addr, volume_info.UNC,
-			     volume_info.username);
 		if (tcon) {
 			cFYI(1, ("Found match on UNC path"));
 			/* we can have only one retry value for a connection
@@ -2241,35 +2193,21 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
 
 /* on error free sesinfo and tcon struct if needed */
 	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; */
@@ -3575,13 +3513,7 @@ cifs_umount(struct super_block *sb, struct cifs_sb_info *cifs_sb)
 			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"));
 	}
-- 
1.5.5.1

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