Add a switch for using tmpfs storage

Since SSDs are becoming more common, the performance punishment
of moving from RAM to SSD is not very high and the capacity gain
is significant when running a large number of vms.
Signed-off-by: NPlamen Dimitrov <pdimitrov@pevogam.com>

avocado/utils/lv_utils.py

@@ -57,7 +57,8 @@ def get_diskspace(disk):
 
 
 def vg_ramdisk(disk, vg_name, ramdisk_vg_size,
-               ramdisk_basedir, ramdisk_sparse_filename):
+               ramdisk_basedir, ramdisk_sparse_filename,
+               use_tmpfs=True):
     """
     Create vg on top of ram memory to speed up lv performance.
     When disk is specified size of the physical volume is taken from
@@ -91,15 +92,17 @@ def vg_ramdisk(disk, vg_name, ramdisk_vg_size,
                                     ramdisk_sparse_filename)
     # Try to cleanup the ramdisk before defining it
     try:
-        vg_ramdisk_cleanup(ramdisk_filename, vg_ramdisk_dir, vg_name)
+        vg_ramdisk_cleanup(ramdisk_filename, vg_ramdisk_dir,
+                           vg_name, use_tmpfs)
     except LVException:
         pass
     if not os.path.exists(vg_ramdisk_dir):
         os.makedirs(vg_ramdisk_dir)
     try:
-        LOGGER.debug("Mounting tmpfs")
-        process.run("mount -t tmpfs tmpfs %s" % vg_ramdisk_dir,
-                    sudo=True)
+        if use_tmpfs:
+            LOGGER.debug("Mounting tmpfs")
+            process.run("mount -t tmpfs tmpfs %s" % vg_ramdisk_dir,
+                        sudo=True)
 
         LOGGER.debug("Converting and copying /dev/zero")
         if disk:
@@ -114,7 +117,8 @@ def vg_ramdisk(disk, vg_name, ramdisk_vg_size,
             result = process.run("losetup --find", sudo=True)
     except process.CmdError as ex:
         LOGGER.error(ex)
-        vg_ramdisk_cleanup(ramdisk_filename, vg_ramdisk_dir, vg_name)
+        vg_ramdisk_cleanup(ramdisk_filename, vg_ramdisk_dir,
+                           vg_name, use_tmpfs)
         raise LVException("Fail to create vg_ramdisk: %s" % ex)
 
     if not disk:
@@ -134,13 +138,13 @@ def vg_ramdisk(disk, vg_name, ramdisk_vg_size,
     except process.CmdError as ex:
         LOGGER.error(ex)
         vg_ramdisk_cleanup(ramdisk_filename, vg_ramdisk_dir,
-                           vg_name, loop_device)
+                           vg_name, loop_device, use_tmpfs)
         raise LVException("Fail to create vg_ramdisk: %s" % ex)
     return ramdisk_filename, vg_ramdisk_dir, vg_name, loop_device
 
 
 def vg_ramdisk_cleanup(ramdisk_filename=None, vg_ramdisk_dir=None,
-                       vg_name=None, loop_device=None):
+                       vg_name=None, loop_device=None, use_tmpfs=True):
     """
     Inline cleanup function in case of test error.
 
@@ -194,8 +198,8 @@ def vg_ramdisk_cleanup(ramdisk_filename=None, vg_ramdisk_dir=None,
             vg_ramdisk_dir = os.path.dirname(ramdisk_filename)
 
     if vg_ramdisk_dir is not None:
-        if not process.system("mountpoint %s" % vg_ramdisk_dir,
-                              ignore_status=True):
+        if use_tmpfs and not process.system("mountpoint %s" % vg_ramdisk_dir,
+                                            ignore_status=True):
             for _ in range(10):
                 result = process.run("umount %s" % vg_ramdisk_dir,
                                      ignore_status=True, sudo=True)