Added methods in memory library that gets and sets a transparent hugepage values.

GenIOException Base Exception class has been created for all IO related exceptions.
Also adds write_file_or_fail method in genio library which writes
to a file and raises exception when write fails.
Signed-off-by: NSanthosh G <santhog4@linux.vnet.ibm.com>

avocado/utils/genio.py

@@ -29,6 +29,13 @@ _open_log_files = {}
 _log_file_dir = os.environ.get('TMPDIR', '/tmp')
 
 
+class GenIOError(Exception):
+    """
+    Base Exception Class for all IO exceptions
+    """
+    pass
+
+
 def log_line(filename, line):
     """
     Write a line to a file.
@@ -174,3 +181,21 @@ def write_one_line(filename, line):
     :type line: str
     """
     write_file(filename, line.rstrip('\n') + '\n')
+
+
+def write_file_or_fail(filename, data):
+    """
+    Write to a file and raise exception on write failure
+
+    :param filename: Path to file
+    :type filename: str
+    :param data: Data to be written to file
+    :type data: str
+    :raises GenIOError: On write Failure
+    """
+    fd = os.open(filename, os.O_WRONLY)
+    try:
+        ret = os.write(fd, data)
+    except OSError as details:
+        raise GenIOError("The write to %s failed: %s" % (
+                         filename, details))

avocado/utils/memory.py

@@ -17,12 +17,14 @@
 # Authors: Yiqiao Pu <ypu@redhat.com>
 
 
+import os
 import re
 import glob
 import math
 import logging
 
 from . import process
+from . import genio
 
 
 # Returns total memory in kb
@@ -278,3 +280,33 @@ def get_buddy_info(chunk_sizes, nodes="all", zones="all"):
             buddyinfo_dict[chunk_size] += int(chunk_info)
 
     return buddyinfo_dict
+
+
+def set_thp_value(feature, value):
+    """
+    Sets THP feature to a given value
+
+    :param feature: Thp feature to set
+    :type feature: str
+    :param value: Value to be set to feature
+    :type value: str
+    """
+    thp_path = '/sys/kernel/mm/transparent_hugepage/'
+    thp_feature_to_set = os.path.join(thp_path, feature)
+    genio.write_file_or_fail(thp_feature_to_set, value)
+
+
+def get_thp_value(feature):
+    """
+    Gets the value of the thp feature arg passed
+
+    :Param feature: Thp feature to get value
+    :type feature: str
+    """
+    thp_path = '/sys/kernel/mm/transparent_hugepage/'
+    thp_feature_to_get = os.path.join(thp_path, feature)
+    value = genio.read_file(thp_feature_to_get)
+    if feature in ("enabled", "defrag", "shmem_enabled"):
+        return (re.search(r"\[(\w+)\]", value)).group(1)
+    else:
+        return value