overlay lib: Secure the creation of the disk image when size is < 130

In case the filesystem for which the disk img is going to be created
has very small amount of free space (under 130 MiBs), it cannot be
formatted by XFS with current params.

This could be hit in several cases:
 * the system partition/volume - in this case, most likely an issue
   will be hit anyway later by DNF speaking about small amount of
   free space if a content is installed inside by RPMs
   as such a small amount of free space is really not expected
   to see at all
 * it's a data mount point (e.g. iso) or a filesystem type that should
   by part of the OVERLAY_DO_NOT_MOUNT set, so enlarging the value
   to 130 MiBs should not affect anything negatively at all
 * in case of /boot, the problem with the free space is covered
   already in a different actor prior we try to create any disk img,
   so we are safe here

Based on arguments above, I am considering setting the 130 MiBs as
minimal value safe for in-place upgrades. Also it will allow to skip
possible problems with specific file systems (like tmpfs, ...) in case
we are still missing some in the OVERLAY_DO_NOT_MOUNT - and kind of
read only storage (such as iso9660, etc..).

Author: pirat89

repos/system_upgrade/common/libraries/overlaygen.py

@@ -367,9 +367,12 @@ def _format_disk_image_ext4(diskimage_path):
         utils.call_with_oserror_handled(cmd=cmd)
     except CalledProcessError as e:
         # FIXME(pstodulk): taken from original, but %s seems to me invalid here
-        api.current_logger().error('Failed to create ext4 filesystem %s', diskimage_path, exc_info=True)
+        api.current_logger().error('Failed to create ext4 filesystem in %s', diskimage_path, exc_info=True)
         raise StopActorExecutionError(
-            message=str(e)
+            message='Cannot create Ext4 filesystem in{}'.format(diskimage_path),
+            details={
+                'error message': str(e),
+            }
         )
 
 
@@ -388,7 +391,10 @@ def _format_disk_image_xfs(diskimage_path):
         # FIXME(pstodulk): taken from original, but %s seems to me invalid here
         api.current_logger().error('Failed to create XFS filesystem %s', diskimage_path, exc_info=True)
         raise StopActorExecutionError(
-            message=str(e)
+            message='Cannot create XFS filesystem in{}'.format(diskimage_path),
+            details={
+                'error message': str(e),
+            }
         )
 
 
@@ -405,15 +411,42 @@ def _create_mount_disk_image(disk_images_directory, path, disk_size):
     and it's supposed to be used for write directories of an overlayfs built
     above it.
 
+    If the disk_size is lower than 130 MiBs, the disk size is automatically
+    set to 130 MiBs to be able to format it correctly.
+
     The disk image is formatted with Ext4 if (envar) `LEAPP_OVL_IMG_FS_EXT4=1`.
 
     :param disk_images_directory: Path to the directory where disk images should be stored.
     :type disk_images_directory: str
     :param path: Path to the mountpoint of the original (host/source) partition/volume
     :type path: str
+    :param disk_size: Apparent size of the disk img in MiBs
+    :type disk_size: int
     :return: Path to the created disk image
     :rtype: str
     """
+    if disk_size < 130:
+        # NOTE(pstodulk): SEATBELT
+        # min. required size for current params to format a disk img with a FS:
+        #   XFS  -> 130 MiB
+        #   EXT4 -> 70  MiB
+        # so let's stick to 130 always. This is expected to happen when:
+        #  * the free space on a system mountpoint is really super small, but if
+        #    such a mounpoint contains a content installed by packages, most
+        #    likely the msg about not enough free space is raised
+        #  * the mountpoint is actually no important at all, could be possibly
+        #    read only (e.g. ISO), or it's an FS type that should be covered by
+        #    OVERLAY_DO_NOT_MOUNT
+        #  * most common case important for us here could be /boot, but that's
+        #    covered already in different actors/checks, so it should not be
+        #    problem either
+        # NOTE(pstodulk): In case the formatting params are modified,
+        # the minimal required size could be different
+        api.current_logger().warning(
+            'The apparent size for the disk image representing {path}'
+            ' is too small ({} MiBs) for a formatting. Setting 130 MiBs instead.'
+        )
+        disk_size = 130
     diskimage_path = os.path.join(disk_images_directory, _mount_name(path))
     cmd = [
         '/bin/dd',