[CIFS] Fix oops in cifs_create when nfsd server exports cifs mount

nfsd is passing null nameidata (probably the only one doing that)
on call to create - cifs was missing one check for this.

Note that running nfsd over a cifs mount requires specifying fsid on
the nfs exports entry and requires mounting cifs with serverino mount
option.

Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/CHANGES

@@ -1,6 +1,7 @@
 Version 1.50
 ------------
-Fix NTLMv2 signing
+Fix NTLMv2 signing. NFS server mounted over cifs works (if cifs mount is
+done with "serverino" mount option).
 
 Version 1.49
 ------------

fs/cifs/README

@@ -370,7 +370,7 @@ A partial list of the supported mount options follows:
 		Note that this does not affect the normal ACL check on the
 		target machine done by the server software (of the server
 		ACL against the user name provided at mount time).
-  serverino	Use servers inode numbers instead of generating automatically
+  serverino	Use server's inode numbers instead of generating automatically
 		incrementing inode numbers on the client.  Although this will
 		make it easier to spot hardlinked files (as they will have
 		the same inode numbers) and inode numbers may be persistent,
@@ -378,12 +378,11 @@ A partial list of the supported mount options follows:
 		are unique if multiple server side mounts are exported under a
 		single share (since inode numbers on the servers might not
 		be unique if multiple filesystems are mounted under the same
-		shared higher level directory).  Note that this requires that
-		the server support the CIFS Unix Extensions as other servers
-		do not return a unique IndexNumber on SMB FindFirst (most
-		servers return zero as the IndexNumber).  Parameter has no
-		effect to Windows servers and others which do not support the
-		CIFS Unix Extensions.
+		shared higher level directory).  Note that some older
+		(e.g. pre-Windows 2000) do not support returning UniqueIDs
+		or the CIFS Unix Extensions equivalent and for those
+		this mount option will have no effect.  Exporting cifs mounts
+		under nfsd requires this mount option on the cifs mount.
   noserverino   Client generates inode numbers (rather than using the actual one
 		from the server) by default.
   setuids       If the CIFS Unix extensions are negotiated with the server

fs/cifs/cifsfs.c

@@ -114,10 +114,6 @@ cifs_read_super(struct super_block *sb, void *data,
 
 	sb->s_magic = CIFS_MAGIC_NUMBER;
 	sb->s_op = &cifs_super_ops;
-#ifdef CONFIG_CIFS_EXPERIMENTAL
-	if (experimEnabled != 0)
-		sb->s_export_op = &cifs_export_ops;
-#endif /* EXPERIMENTAL */
 /*	if (cifs_sb->tcon->ses->server->maxBuf > MAX_CIFS_HDR_SIZE + 512)
 	    sb->s_blocksize =
 		cifs_sb->tcon->ses->server->maxBuf - MAX_CIFS_HDR_SIZE; */
@@ -140,6 +136,13 @@ cifs_read_super(struct super_block *sb, void *data,
 		goto out_no_root;
 	}
 	
+#ifdef CONFIG_CIFS_EXPERIMENTAL
+	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_SERVER_INUM) {
+		cFYI(1, ("export ops supported"));
+		sb->s_export_op = &cifs_export_ops;
+	}
+#endif /* EXPERIMENTAL */
+
 	return 0;
 
 out_no_root:

fs/cifs/dir.c

@@ -264,7 +264,8 @@ cifs_create(struct inode *inode, struct dentry *direntry, int mode,
 				direntry->d_op = &cifs_dentry_ops;
 			d_instantiate(direntry, newinode);
 		}
-		if ((nd->flags & LOOKUP_OPEN) == FALSE) {
+		if ((nd == NULL /* nfsd case - nfs srv does not set nd */) ||
+			((nd->flags & LOOKUP_OPEN) == FALSE)) {
 			/* mknod case - do not leave file open */
 			CIFSSMBClose(xid, pTcon, fileHandle);
 		} else if (newinode) {

fs/cifs/export.c

@@ -26,15 +26,30 @@
  /*
   * See Documentation/filesystems/Exporting
   * and examples in fs/exportfs
+  *
+  * Since cifs is a network file system, an "fsid" must be included for
+  * any nfs exports file entries which refer to cifs paths.  In addition
+  * the cifs mount must be mounted with the "serverino" option (ie use stable
+  * server inode numbers instead of locally generated temporary ones).
+  * Although cifs inodes do not use generation numbers (have generation number
+  * of zero) - the inode number alone should be good enough for simple cases
+  * in which users want to export cifs shares with NFS. The decode and encode
+  * could be improved by using a new routine which expects 64 bit inode numbers
+  * instead of the default 32 bit routines in fs/exportfs
+  *
   */
 
 #include <linux/fs.h>
+#include "cifsglob.h"
+#include "cifs_debug.h"
+
  
 #ifdef CONFIG_CIFS_EXPERIMENTAL
  
 static struct dentry *cifs_get_parent(struct dentry *dentry)
 {
 	/* BB need to add code here eventually to enable export via NFSD */
+	cFYI(1, ("get parent for %p", dentry));
 	return ERR_PTR(-EACCES);
 }
  

fs/cifs/file.c

@@ -212,7 +212,7 @@ int cifs_open(struct inode *inode, struct file *file)
 		return -ENOMEM;
 	}
 
-	cFYI(1, (" inode = 0x%p file flags are 0x%x for %s",
+	cFYI(1, ("inode = 0x%p file flags are 0x%x for %s",
 		 inode, file->f_flags, full_path));
 	desiredAccess = cifs_convert_flags(file->f_flags);