Avoid smb data corruption under heavy stress

fs/cifs/CHANGES

+
 Version 0.98
 ------------
 Fix hang in commit_write during reconnection of open files under heavy load.
-Fix unload_nls oops in a mount failure path. 
+Fix unload_nls oops in a mount failure path. Serialize writes to same socket
+which also fixes any possible races when cifs signatures are enabled in SMBs
+being sent out of signature sequence number order.    
 
 Version 0.97
 ------------

fs/cifs/connect.c

@@ -990,6 +990,7 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
 			init_waitqueue_head(&srvTcp->response_q);
 			INIT_LIST_HEAD(&srvTcp->pending_mid_q);
 			srvTcp->tcpStatus = CifsGood;
+			init_MUTEX(&srvTcp->tcpSem);
 			kernel_thread((void *)(void *)cifs_demultiplex_thread, srvTcp,
 				      CLONE_FS | CLONE_FILES | CLONE_VM);
 		}

fs/cifs/dir.c

@@ -220,6 +220,7 @@ cifs_create(struct inode *inode, struct dentry *direntry, int mode,
 				pCifsFile->pInode = newinode;
 				pCifsFile->invalidHandle = FALSE;
 				pCifsFile->closePend     = FALSE;
+				init_MUTEX(&pCifsFile->fh_sem);
 				/* pCifsFile->pfile = file; */ /* put in at open time */
 				write_lock(&GlobalSMBSeslock);
 				list_add(&pCifsFile->tlist,&pTcon->openFileList);

fs/cifs/file.c

@@ -142,6 +142,7 @@ cifs_open(struct inode *inode, struct file *file)
 			pCifsFile = (struct cifsFileInfo *) file->private_data;
 			pCifsFile->netfid = netfid;
 			pCifsFile->pid = current->pid;
+			init_MUTEX(&pCifsFile->fh_sem);
 			pCifsFile->pfile = file; /* needed for writepage */
 			pCifsFile->pInode = inode;
 			pCifsFile->invalidHandle = FALSE;
@@ -1390,6 +1391,7 @@ cifs_readdir(struct file *file, void *direntry, filldir_t filldir)
 				    (struct cifsFileInfo *) file->private_data;
 				cifsFile->netfid = searchHandle;
 				cifsFile->invalidHandle = FALSE;
+				init_MUTEX(&cifsFile->fh_sem);
 			} else {
 				rc = -ENOMEM;
 				break;

fs/cifs/transport.c

@@ -192,13 +192,18 @@ SendReceive(const unsigned int xid, struct cifsSesInfo *ses,
 			return -EAGAIN;
 		} /* else ok - we are setting up session */
 	}
-
+	/* make sure that we sign in the same order that we send on this socket 
+		and avoid races inside tcp sendmsg code that could cause corruption
+		of smb data */
+	down(&ses->server->tcpSem); 
 	midQ = AllocMidQEntry(in_buf, ses);
 	if (midQ == NULL) {
+		up(&ses->server->tcpSem);
 		return -EIO;
 	}
 
 	if (in_buf->smb_buf_length > CIFS_MAX_MSGSIZE + MAX_CIFS_HDR_SIZE - 4) {
+		up(&ses->server->tcpSem);
 		cERROR(1,
 		       ("Illegal length, greater than maximum frame, %d ",
 			in_buf->smb_buf_length));
@@ -214,7 +219,7 @@ SendReceive(const unsigned int xid, struct cifsSesInfo *ses,
 	midQ->midState = MID_REQUEST_SUBMITTED;
 	rc = smb_send(ses->server->ssocket, in_buf, in_buf->smb_buf_length,
 		      (struct sockaddr *) &(ses->server->sockAddr));
-
+	up(&ses->server->tcpSem);
 	if (long_op == -1)
 		goto cifs_no_response_exit;
 	if (long_op > 1) /* writes past end of file can take looooong time */