diff --git a/fs/cifs/CHANGES b/fs/cifs/CHANGES
index 72063f5..851388f 100644
--- a/fs/cifs/CHANGES
+++ b/fs/cifs/CHANGES
@@ -1,3 +1,13 @@
+Version 1.57
+------------
+Improve support for multiple security contexts to the same server. We
+used to use the same "vcnumber" for all connections which could cause
+the server to treat subsequent connections, especially those that
+are authenticated as guest, as reconnections, invalidating the earlier
+user's smb session.  This fix allows cifs to mount multiple times to the
+same server with different userids without risking invalidating earlier
+established security contexts.
+
 Version 1.56
 ------------
 Add "forcemandatorylock" mount option to allow user to use mandatory
diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
index 7ac4818..2b1d28a 100644
--- a/fs/cifs/cifsfs.h
+++ b/fs/cifs/cifsfs.h
@@ -100,5 +100,5 @@ extern long cifs_ioctl(struct file *filep, unsigned int cmd, unsigned long arg);
 extern const struct export_operations cifs_export_ops;
 #endif /* EXPERIMENTAL */
 
-#define CIFS_VERSION   "1.56"
+#define CIFS_VERSION   "1.57"
 #endif				/* _CIFSFS_H */
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 94c1ca0..e004f6d 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -164,9 +164,12 @@ struct TCP_Server_Info {
 	/* multiplexed reads or writes */
 	unsigned int maxBuf;	/* maxBuf specifies the maximum */
 	/* message size the server can send or receive for non-raw SMBs */
-	unsigned int maxRw;	/* maxRw specifies the maximum */
+	unsigned int max_rw;	/* maxRw specifies the maximum */
 	/* message size the server can send or receive for */
 	/* SMB_COM_WRITE_RAW or SMB_COM_READ_RAW. */
+	unsigned int max_vcs;	/* maximum number of smb sessions, at least
+				   those that can be specified uniquely with
+				   vcnumbers */
 	char sessid[4];		/* unique token id for this session */
 	/* (returned on Negotiate */
 	int capabilities; /* allow selective disabling of caps by smb sess */
@@ -210,6 +213,7 @@ struct cifsSesInfo {
 	unsigned overrideSecFlg;  /* if non-zero override global sec flags */
 	__u16 ipc_tid;		/* special tid for connection to IPC share */
 	__u16 flags;
+	__u16 vcnum;
 	char *serverOS;		/* name of operating system underlying server */
 	char *serverNOS;	/* name of network operating system of server */
 	char *serverDomain;	/* security realm of server */
diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 552642a..939e2f7 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -528,14 +528,15 @@ CIFSSMBNegotiate(unsigned int xid, struct cifsSesInfo *ses)
 		server->maxReq = le16_to_cpu(rsp->MaxMpxCount);
 		server->maxBuf = min((__u32)le16_to_cpu(rsp->MaxBufSize),
 				(__u32)CIFSMaxBufSize + MAX_CIFS_HDR_SIZE);
+		server->max_vcs = le16_to_cpu(rsp->MaxNumberVcs);
 		GETU32(server->sessid) = le32_to_cpu(rsp->SessionKey);
 		/* even though we do not use raw we might as well set this
 		accurately, in case we ever find a need for it */
 		if ((le16_to_cpu(rsp->RawMode) & RAW_ENABLE) == RAW_ENABLE) {
-			server->maxRw = 0xFF00;
+			server->max_rw = 0xFF00;
 			server->capabilities = CAP_MPX_MODE | CAP_RAW_MODE;
 		} else {
-			server->maxRw = 0;/* we do not need to use raw anyway */
+			server->max_rw = 0;/* do not need to use raw anyway */
 			server->capabilities = CAP_MPX_MODE;
 		}
 		tmp = (__s16)le16_to_cpu(rsp->ServerTimeZone);
@@ -638,7 +639,7 @@ CIFSSMBNegotiate(unsigned int xid, struct cifsSesInfo *ses)
 	/* probably no need to store and check maxvcs */
 	server->maxBuf = min(le32_to_cpu(pSMBr->MaxBufferSize),
 			(__u32) CIFSMaxBufSize + MAX_CIFS_HDR_SIZE);
-	server->maxRw = le32_to_cpu(pSMBr->MaxRawSize);
+	server->max_rw = le32_to_cpu(pSMBr->MaxRawSize);
 	cFYI(DBG2, ("Max buf = %d", ses->server->maxBuf));
 	GETU32(ses->server->sessid) = le32_to_cpu(pSMBr->SessionKey);
 	server->capabilities = le32_to_cpu(pSMBr->Capabilities);
diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
index b234407..5c68b42 100644
--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -34,15 +34,99 @@
 extern void SMBNTencrypt(unsigned char *passwd, unsigned char *c8,
 			 unsigned char *p24);
 
+/* Checks if this is the first smb session to be reconnected after
+   the socket has been reestablished (so we know whether to use vc 0).
+   Called while holding the cifs_tcp_ses_lock, so do not block */
+static bool is_first_ses_reconnect(struct cifsSesInfo *ses)
+{
+	struct list_head *tmp;
+	struct cifsSesInfo *tmp_ses;
+
+	list_for_each(tmp, &ses->server->smb_ses_list) {
+		tmp_ses = list_entry(tmp, struct cifsSesInfo,
+				     smb_ses_list);
+		if (tmp_ses->need_reconnect == false)
+			return false;
+	}
+	/* could not find a session that was already connected,
+	   this must be the first one we are reconnecting */
+	return true;
+}
+
+/*
+ *	vc number 0 is treated specially by some servers, and should be the
+ *      first one we request.  After that we can use vcnumbers up to maxvcs,
+ *	one for each smb session (some Windows versions set maxvcs incorrectly
+ *	so maxvc=1 can be ignored).  If we have too many vcs, we can reuse
+ *	any vc but zero (some servers reset the connection on vcnum zero)
+ *
+ */
+static __le16 get_next_vcnum(struct cifsSesInfo *ses)
+{
+	__u16 vcnum = 0;
+	struct list_head *tmp;
+	struct cifsSesInfo *tmp_ses;
+	__u16 max_vcs = ses->server->max_vcs;
+	__u16 i;
+	int free_vc_found = 0;
+
+	/* Quoting the MS-SMB specification: "Windows-based SMB servers set this
+	field to one but do not enforce this limit, which allows an SMB client
+	to establish more virtual circuits than allowed by this value ... but
+	other server implementations can enforce this limit." */
+	if (max_vcs < 2)
+		max_vcs = 0xFFFF;
+
+	write_lock(&cifs_tcp_ses_lock);
+	if ((ses->need_reconnect) && is_first_ses_reconnect(ses))
+			goto get_vc_num_exit;  /* vcnum will be zero */
+	for (i = ses->server->srv_count - 1; i < max_vcs; i++) {
+		if (i == 0) /* this is the only connection, use vc 0 */
+			break;
+
+		free_vc_found = 1;
+
+		list_for_each(tmp, &ses->server->smb_ses_list) {
+			tmp_ses = list_entry(tmp, struct cifsSesInfo,
+					     smb_ses_list);
+			if (tmp_ses->vcnum == i) {
+				free_vc_found = 0;
+				break; /* found duplicate, try next vcnum */
+			}
+		}
+		if (free_vc_found)
+			break; /* we found a vcnumber that will work - use it */
+	}
+
+	if (i == 0)
+		vcnum = 0; /* for most common case, ie if one smb session, use
+			      vc zero.  Also for case when no free vcnum, zero
+			      is safest to send (some clients only send zero) */
+	else if (free_vc_found == 0)
+		vcnum = 1;  /* we can not reuse vc=0 safely, since some servers
+				reset all uids on that, but 1 is ok. */
+	else
+		vcnum = i;
+	ses->vcnum = vcnum;
+get_vc_num_exit:
+	write_unlock(&cifs_tcp_ses_lock);
+
+	return le16_to_cpu(vcnum);
+}
+
 static __u32 cifs_ssetup_hdr(struct cifsSesInfo *ses, SESSION_SETUP_ANDX *pSMB)
 {
 	__u32 capabilities = 0;
 
 	/* init fields common to all four types of SessSetup */
-	/* note that header is initialized to zero in header_assemble */
+	/* Note that offsets for first seven fields in req struct are same  */
+	/*	in CIFS Specs so does not matter which of 3 forms of struct */
+	/*	that we use in next few lines                               */
+	/* Note that header is initialized to zero in header_assemble */
 	pSMB->req.AndXCommand = 0xFF;
 	pSMB->req.MaxBufferSize = cpu_to_le16(ses->server->maxBuf);
 	pSMB->req.MaxMpxCount = cpu_to_le16(ses->server->maxReq);
+	pSMB->req.VcNumber = get_next_vcnum(ses);
 
 	/* Now no need to set SMBFLG_CASELESS or obsolete CANONICAL PATH */
 
@@ -71,7 +155,6 @@ static __u32 cifs_ssetup_hdr(struct cifsSesInfo *ses, SESSION_SETUP_ANDX *pSMB)
 	if (ses->capabilities & CAP_UNIX)
 		capabilities |= CAP_UNIX;
 
-	/* BB check whether to init vcnum BB */
 	return capabilities;
 }