[CIFS] xattr support for cifs filesystem part 5 of 5, add removexattr capability

Signed-off-by:  Steve French (sfrench@us.ibm.com)

fs/Kconfig

@@ -1652,6 +1652,22 @@ config CIFS_STATS
           Enabling this option will cause statistics for each server share
 	  mounted by the cifs client to be displayed in /proc/fs/cifs/Stats
 
+config CIFS_XATTR
+        bool "CIFS extended attributes (EXPERIMENTAL)"
+        depends on CIFS
+        help
+          Extended attributes are name:value pairs associated with inodes by
+          the kernel or by users (see the attr(5) manual page, or visit
+          <http://acl.bestbits.at/> for details).  CIFS maps the name of
+          extended attributes beginning with the user namespace prefix
+          to SMB/CIFS EAs. EAs are stored on Windows servers without the
+          user namespace prefix, but their names are seen by Linux cifs clients
+          prefaced by the user namespace prefix. The system namespace
+          (used by some filesystems to store ACLs) is not supported at
+          this time.
+                                                                                                    
+          If unsure, say N.
+
 config CIFS_POSIX
         bool "CIFS POSIX Extensions (EXPERIMENTAL)"
         depends on CIFS

fs/cifs/CHANGES

+Version 1.22
+------------
+Add config option to enable XATTR (extended attribute) support, mapping
+xattr names in the "user." namespace space to SMB/CIFS EAs.
+
 Version 1.21
 ------------
 Add new mount parm to control whether mode check (vfs_permission) is done on

fs/cifs/cifssmb.c

@@ -3370,7 +3370,8 @@ CIFSSMBSetEA(const int xid, struct cifsTconInfo *tcon, const char *fileName,
 
 	/*BB add length check that it would fit in negotiated SMB buffer size BB */
 	/* if(ea_value_len > buffer_size - 512 (enough for header)) */
-	memcpy(parm_data->list[0].name+name_len+1,ea_value,ea_value_len);
+	if(ea_value_len)
+		memcpy(parm_data->list[0].name+name_len+1,ea_value,ea_value_len);
 
 	pSMB->TotalDataCount = pSMB->DataCount;
 	pSMB->ParameterCount = cpu_to_le16(pSMB->ParameterCount);

fs/cifs/xattr.c

@@ -34,9 +34,51 @@
 /* also note could add check for security prefix XATTR_SECURITY_PREFIX */ 
 
 
-int cifs_removexattr(struct dentry * direntry, const char * name)
+int cifs_removexattr(struct dentry * direntry, const char * ea_name)
 {
 	int rc = -EOPNOTSUPP;
+#ifdef CONFIG_CIFS_XATTR
+	int xid;
+	struct cifs_sb_info *cifs_sb;
+	struct cifsTconInfo *pTcon;
+	struct super_block * sb;
+	char * full_path;
+                                                                                     
+	if(direntry == NULL)
+		return -EIO;
+	if(direntry->d_inode == NULL)
+		return -EIO;
+	sb = direntry->d_inode->i_sb;
+	if(sb == NULL)
+		return -EIO;
+	xid = GetXid();
+                                                                                     
+	cifs_sb = CIFS_SB(sb);
+	pTcon = cifs_sb->tcon;
+                                                                                     
+	down(&sb->s_vfs_rename_sem);
+	full_path = build_path_from_dentry(direntry);
+	up(&sb->s_vfs_rename_sem);
+	if(full_path == NULL) {
+		FreeXid(xid);
+		return -ENOMEM;
+	}
+	if(ea_name == NULL) {
+		cFYI(1,("Null xattr names not supported"));
+	} else if(strncmp(ea_name,CIFS_XATTR_USER_PREFIX,5)) {
+		cFYI(1,("illegal xattr namespace %s (only user namespace supported)",ea_name));
+		/* BB what if no namespace prefix? */
+		/* Should we just pass them to server, except for
+		system and perhaps security prefixes? */
+	} else {
+		ea_name+=5; /* skip past user. prefix */
+		rc = CIFSSMBSetEA(xid,pTcon,full_path,ea_name,0,
+			(__u16)0, cifs_sb->local_nls);
+	}
+	if (full_path)
+		kfree(full_path);
+	FreeXid(xid);
+#endif
 	return rc;
 }