cifs: reinstate sharing of tree connections

Use a similar approach to the SMB session sharing. Add a list of tcons
attached to each SMB session. Move the refcount to non-atomic. Protect
all of the above with the cifs_tcp_ses_lock. Add functions to
properly find and put references to the tcons.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/cifsfs.c

@@ -514,10 +514,11 @@ static void cifs_umount_begin(struct super_block *sb)
 	tcon = cifs_sb->tcon;
 	if (tcon == NULL)
 		return;
-	down(&tcon->tconSem);
-	if (atomic_read(&tcon->useCount) == 1)
+
+	read_lock(&cifs_tcp_ses_lock);
+	if (tcon->tc_count == 1)
 		tcon->tidStatus = CifsExiting;
-	up(&tcon->tconSem);
+	read_unlock(&cifs_tcp_ses_lock);
 
 	/* cancel_brl_requests(tcon); */ /* BB mark all brl mids as exiting */
 	/* cancel_notify_requests(tcon); */
@@ -1060,7 +1061,6 @@ init_cifs(void)
 	int rc = 0;
 	cifs_proc_init();
 	INIT_LIST_HEAD(&cifs_tcp_ses_list);
-	INIT_LIST_HEAD(&GlobalTreeConnectionList); /* BB to be removed by jl */
 	INIT_LIST_HEAD(&GlobalOplock_Q);
 #ifdef CONFIG_CIFS_EXPERIMENTAL
 	INIT_LIST_HEAD(&GlobalDnotifyReqList);

fs/cifs/cifsglob.h

@@ -233,16 +233,15 @@ struct cifsSesInfo {
  * session
  */
 struct cifsTconInfo {
-	struct list_head cifsConnectionList;
+	struct list_head tcon_list;
+	int tc_count;
 	struct list_head openFileList;
-	struct semaphore tconSem;
 	struct cifsSesInfo *ses;	/* pointer to session associated with */
 	char treeName[MAX_TREE_SIZE + 1]; /* UNC name of resource in ASCII */
 	char *nativeFileSystem;
 	__u16 tid;		/* The 2 byte tree id */
 	__u16 Flags;		/* optional support bits */
 	enum statusEnum tidStatus;
-	atomic_t useCount;	/* how many explicit/implicit mounts to share */
 #ifdef CONFIG_CIFS_STATS
 	atomic_t num_smbs_sent;
 	atomic_t num_writes;
@@ -600,9 +599,13 @@ require use of the stronger protocol */
  */
 GLOBAL_EXTERN struct list_head		cifs_tcp_ses_list;
 
-/* protects cifs_tcp_ses_list and srv_count for each tcp session */
+/*
+ * This lock protects the cifs_tcp_ses_list, the list of smb sessions per
+ * tcp session, and the list of tcon's per smb session. It also protects
+ * the reference counters for the server, smb session, and tcon. Finally,
+ * changes to the tcon->tidStatus should be done while holding this lock.
+ */
 GLOBAL_EXTERN rwlock_t		cifs_tcp_ses_lock;
-GLOBAL_EXTERN struct list_head GlobalTreeConnectionList; /* BB to be removed */
 GLOBAL_EXTERN rwlock_t GlobalSMBSeslock;  /* protects list inserts on 3 above */
 
 GLOBAL_EXTERN struct list_head GlobalOplock_Q;

fs/cifs/cifssmb.c

@@ -742,50 +742,31 @@ CIFSSMBTDis(const int xid, struct cifsTconInfo *tcon)
 	int rc = 0;
 
 	cFYI(1, ("In tree disconnect"));
-	/*
-	 *  If last user of the connection and
-	 *  connection alive - disconnect it
-	 *  If this is the last connection on the server session disconnect it
-	 *  (and inside session disconnect we should check if tcp socket needs
-	 *  to be freed and kernel thread woken up).
-	 */
-	if (tcon)
-		down(&tcon->tconSem);
-	else
-		return -EIO;
 
-	atomic_dec(&tcon->useCount);
-	if (atomic_read(&tcon->useCount) > 0) {
-		up(&tcon->tconSem);
-		return -EBUSY;
-	}
+	/* BB: do we need to check this? These should never be NULL. */
+	if ((tcon->ses == NULL) || (tcon->ses->server == NULL))
+		return -EIO;
 
-	/* No need to return error on this operation if tid invalidated and
-	closed on server already e.g. due to tcp session crashing */
-	if (tcon->need_reconnect) {
-		up(&tcon->tconSem);
+	/*
+	 * No need to return error on this operation if tid invalidated and
+	 * closed on server already e.g. due to tcp session crashing. Also,
+	 * the tcon is no longer on the list, so no need to take lock before
+	 * checking this.
+	 */
+	if (tcon->need_reconnect)
 		return 0;
-	}
 
-	if ((tcon->ses == NULL) || (tcon->ses->server == NULL)) {
-		up(&tcon->tconSem);
-		return -EIO;
-	}
 	rc = small_smb_init(SMB_COM_TREE_DISCONNECT, 0, tcon,
 			    (void **)&smb_buffer);
-	if (rc) {
-		up(&tcon->tconSem);
+	if (rc)
 		return rc;
-	}
 
 	rc = SendReceiveNoRsp(xid, tcon->ses, smb_buffer, 0);
 	if (rc)
 		cFYI(1, ("Tree disconnect failed %d", rc));
 
-	up(&tcon->tconSem);
-
 	/* No need to return error on this operation if tid invalidated and
-	closed on server already e.g. due to tcp session crashing */
+	   closed on server already e.g. due to tcp session crashing */
 	if (rc == -EAGAIN)
 		rc = 0;
 

fs/cifs/connect.c

@@ -124,7 +124,7 @@ static int
 cifs_reconnect(struct TCP_Server_Info *server)
 {
 	int rc = 0;
-	struct list_head *tmp;
+	struct list_head *tmp, *tmp2;
 	struct cifsSesInfo *ses;
 	struct cifsTconInfo *tcon;
 	struct mid_q_entry *mid_entry;
@@ -149,13 +149,12 @@ cifs_reconnect(struct TCP_Server_Info *server)
 		ses = list_entry(tmp, struct cifsSesInfo, smb_ses_list);
 		ses->need_reconnect = true;
 		ses->ipc_tid = 0;
-	}
-	read_unlock(&cifs_tcp_ses_lock);
-	list_for_each(tmp, &GlobalTreeConnectionList) {
-		tcon = list_entry(tmp, struct cifsTconInfo, cifsConnectionList);
-		if ((tcon->ses) && (tcon->ses->server == server))
+		list_for_each(tmp2, &ses->tcon_list) {
+			tcon = list_entry(tmp2, struct cifsTconInfo, tcon_list);
 			tcon->need_reconnect = true;
+		}
 	}
+	read_unlock(&cifs_tcp_ses_lock);
 	/* do not want to be sending data on a socket we are freeing */
 	down(&server->tcpSem);
 	if (server->ssocket) {
@@ -1462,6 +1461,52 @@ cifs_put_smb_ses(struct cifsSesInfo *ses)
 	cifs_put_tcp_session(server);
 }
 
+static struct cifsTconInfo *
+cifs_find_tcon(struct cifsSesInfo *ses, const char *unc)
+{
+	struct list_head *tmp;
+	struct cifsTconInfo *tcon;
+
+	write_lock(&cifs_tcp_ses_lock);
+	list_for_each(tmp, &ses->tcon_list) {
+		tcon = list_entry(tmp, struct cifsTconInfo, tcon_list);
+		if (tcon->tidStatus == CifsExiting)
+			continue;
+		if (strncmp(tcon->treeName, unc, MAX_TREE_SIZE))
+			continue;
+
+		++tcon->tc_count;
+		write_unlock(&cifs_tcp_ses_lock);
+		return tcon;
+	}
+	write_unlock(&cifs_tcp_ses_lock);
+	return NULL;
+}
+
+static void
+cifs_put_tcon(struct cifsTconInfo *tcon)
+{
+	int xid;
+	struct cifsSesInfo *ses = tcon->ses;
+
+	write_lock(&cifs_tcp_ses_lock);
+	if (--tcon->tc_count > 0) {
+		write_unlock(&cifs_tcp_ses_lock);
+		return;
+	}
+
+	list_del_init(&tcon->tcon_list);
+	write_unlock(&cifs_tcp_ses_lock);
+
+	xid = GetXid();
+	CIFSSMBTDis(xid, tcon);
+	_FreeXid(xid);
+
+	DeleteTconOplockQEntries(tcon);
+	tconInfoFree(tcon);
+	cifs_put_smb_ses(ses);
+}
+
 int
 get_dfs_path(int xid, struct cifsSesInfo *pSesInfo, const char *old_path,
 	     const struct nls_table *nls_codepage, unsigned int *pnum_referrals,
@@ -2220,11 +2265,11 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
 	if (!rc) {
 		setup_cifs_sb(&volume_info, cifs_sb);
 
+		tcon = cifs_find_tcon(pSesInfo, volume_info.UNC);
 		if (tcon) {
 			cFYI(1, ("Found match on UNC path"));
-			if (tcon->seal != volume_info.seal)
-				cERROR(1, ("transport encryption setting "
-					   "conflicts with existing tid"));
+			/* existing tcon already has a reference */
+			cifs_put_smb_ses(pSesInfo);
 		} else {
 			tcon = tconInfoAlloc();
 			if (tcon == NULL) {
@@ -2257,6 +2302,10 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
 			if (rc)
 				goto mount_fail_check;
 			tcon->seal = volume_info.seal;
+			tcon->ses = pSesInfo;
+			write_lock(&cifs_tcp_ses_lock);
+			list_add(&tcon->tcon_list, &pSesInfo->tcon_list);
+			write_unlock(&cifs_tcp_ses_lock);
 		}
 
 		/* we can have only one retry value for a connection
@@ -2283,18 +2332,14 @@ mount_fail_check:
 		/* If find_unc succeeded then rc == 0 so we can not end */
 		/* up accidently freeing someone elses tcon struct */
 		if (tcon)
-			tconInfoFree(tcon);
-
-		/* should also end up putting our tcp session ref if needed */
-		if (pSesInfo)
+			cifs_put_tcon(tcon);
+		else if (pSesInfo)
 			cifs_put_smb_ses(pSesInfo);
 		else
 			cifs_put_tcp_session(srvTcp);
 		goto out;
 	}
-	atomic_inc(&tcon->useCount);
 	cifs_sb->tcon = tcon;
-	tcon->ses = pSesInfo;
 
 	/* do not care if following two calls succeed - informational */
 	if (!tcon->ipc) {
@@ -3565,23 +3610,10 @@ int
 cifs_umount(struct super_block *sb, struct cifs_sb_info *cifs_sb)
 {
 	int rc = 0;
-	int xid;
-	struct cifsSesInfo *ses = NULL;
 	char *tmp;
 
-	xid = GetXid();
-
-	if (cifs_sb->tcon) {
-		ses = cifs_sb->tcon->ses; /* save ptr to ses before delete tcon!*/
-		rc = CIFSSMBTDis(xid, cifs_sb->tcon);
-		if (rc == -EBUSY) {
-			FreeXid(xid);
-			return 0;
-		}
-		DeleteTconOplockQEntries(cifs_sb->tcon);
-		tconInfoFree(cifs_sb->tcon);
-		cifs_put_smb_ses(ses);
-	}
+	if (cifs_sb->tcon)
+		cifs_put_tcon(cifs_sb->tcon);
 
 	cifs_sb->tcon = NULL;
 	tmp = cifs_sb->prepath;
@@ -3589,7 +3621,6 @@ cifs_umount(struct super_block *sb, struct cifs_sb_info *cifs_sb)
 	cifs_sb->prepath = NULL;
 	kfree(tmp);
 
-	FreeXid(xid);
 	return rc;
 }
 

fs/cifs/misc.c

@@ -79,6 +79,7 @@ sesInfoAlloc(void)
 		ret_buf->status = CifsNew;
 		++ret_buf->ses_count;
 		INIT_LIST_HEAD(&ret_buf->smb_ses_list);
+		INIT_LIST_HEAD(&ret_buf->tcon_list);
 		init_MUTEX(&ret_buf->sesSem);
 	}
 	return ret_buf;
@@ -107,17 +108,14 @@ tconInfoAlloc(void)
 	struct cifsTconInfo *ret_buf;
 	ret_buf = kzalloc(sizeof(struct cifsTconInfo), GFP_KERNEL);
 	if (ret_buf) {
-		write_lock(&GlobalSMBSeslock);
 		atomic_inc(&tconInfoAllocCount);
-		list_add(&ret_buf->cifsConnectionList,
-			 &GlobalTreeConnectionList);
 		ret_buf->tidStatus = CifsNew;
+		++ret_buf->tc_count;
 		INIT_LIST_HEAD(&ret_buf->openFileList);
-		init_MUTEX(&ret_buf->tconSem);
+		INIT_LIST_HEAD(&ret_buf->tcon_list);
 #ifdef CONFIG_CIFS_STATS
 		spin_lock_init(&ret_buf->stat_lock);
 #endif
-		write_unlock(&GlobalSMBSeslock);
 	}
 	return ret_buf;
 }
@@ -129,10 +127,7 @@ tconInfoFree(struct cifsTconInfo *buf_to_free)
 		cFYI(1, ("Null buffer passed to tconInfoFree"));
 		return;
 	}
-	write_lock(&GlobalSMBSeslock);
 	atomic_dec(&tconInfoAllocCount);
-	list_del(&buf_to_free->cifsConnectionList);
-	write_unlock(&GlobalSMBSeslock);
 	kfree(buf_to_free->nativeFileSystem);
 	kfree(buf_to_free);
 }
@@ -493,9 +488,10 @@ bool
 is_valid_oplock_break(struct smb_hdr *buf, struct TCP_Server_Info *srv)
 {
 	struct smb_com_lock_req *pSMB = (struct smb_com_lock_req *)buf;
-	struct list_head *tmp;
-	struct list_head *tmp1;
+	struct list_head *tmp, *tmp1, *tmp2;
+	struct cifsSesInfo *ses;
 	struct cifsTconInfo *tcon;
+	struct cifsInodeInfo *pCifsInode;
 	struct cifsFileInfo *netfile;
 
 	cFYI(1, ("Checking for oplock break or dnotify response"));
@@ -550,42 +546,42 @@ is_valid_oplock_break(struct smb_hdr *buf, struct TCP_Server_Info *srv)
 		return false;
 
 	/* look up tcon based on tid & uid */
-	read_lock(&GlobalSMBSeslock);
-	list_for_each(tmp, &GlobalTreeConnectionList) {
-		tcon = list_entry(tmp, struct cifsTconInfo, cifsConnectionList);
-		if ((tcon->tid == buf->Tid) && (srv == tcon->ses->server)) {
+	read_lock(&cifs_tcp_ses_lock);
+	list_for_each(tmp, &srv->smb_ses_list) {
+		ses = list_entry(tmp, struct cifsSesInfo, smb_ses_list);
+		list_for_each(tmp1, &ses->tcon_list) {
+			tcon = list_entry(tmp1, struct cifsTconInfo, tcon_list);
+			if (tcon->tid != buf->Tid)
+				continue;
+
 			cifs_stats_inc(&tcon->num_oplock_brks);
-			list_for_each(tmp1, &tcon->openFileList) {
-				netfile = list_entry(tmp1, struct cifsFileInfo,
+			list_for_each(tmp2, &tcon->openFileList) {
+				netfile = list_entry(tmp2, struct cifsFileInfo,
 						     tlist);
-				if (pSMB->Fid == netfile->netfid) {
-					struct cifsInodeInfo *pCifsInode;
-					read_unlock(&GlobalSMBSeslock);
-					cFYI(1,
-					    ("file id match, oplock break"));
-					pCifsInode =
-						CIFS_I(netfile->pInode);
-					pCifsInode->clientCanCacheAll = false;
-					if (pSMB->OplockLevel == 0)
-						pCifsInode->clientCanCacheRead
-							= false;
-					pCifsInode->oplockPending = true;
-					AllocOplockQEntry(netfile->pInode,
-							  netfile->netfid,
-							  tcon);
-					cFYI(1,
-					    ("about to wake up oplock thread"));
-					if (oplockThread)
-					    wake_up_process(oplockThread);
-					return true;
-				}
+				if (pSMB->Fid != netfile->netfid)
+					continue;
+
+				read_unlock(&cifs_tcp_ses_lock);
+				cFYI(1, ("file id match, oplock break"));
+				pCifsInode = CIFS_I(netfile->pInode);
+				pCifsInode->clientCanCacheAll = false;
+				if (pSMB->OplockLevel == 0)
+					pCifsInode->clientCanCacheRead = false;
+				pCifsInode->oplockPending = true;
+				AllocOplockQEntry(netfile->pInode,
+						  netfile->netfid, tcon);
+				cFYI(1, ("about to wake up oplock thread"));
+				if (oplockThread)
+					wake_up_process(oplockThread);
+
+				return true;
 			}
-			read_unlock(&GlobalSMBSeslock);
+			read_unlock(&cifs_tcp_ses_lock);
 			cFYI(1, ("No matching file for oplock break"));
 			return true;
 		}
 	}
-	read_unlock(&GlobalSMBSeslock);
+	read_unlock(&cifs_tcp_ses_lock);
 	cFYI(1, ("Can not process oplock break for non-existent connection"));
 	return true;
 }