From b749548a9eb43b34cce64f8688107645411abc8c Mon Sep 17 00:00:00 2001
From: Eduardo Otubo <otubo@redhat.com>
Date: Tue, 18 Aug 2020 23:12:02 +0200
Subject: Detect kernel version before swap file creation (#428)

According to man page `man 8 swapon', "Preallocated swap files are
supported on XFS since Linux 4.18". This patch checks for kernel version
before attepting to create swapfile, using dd for XFS only on kernel
versions <= 4.18 or btrfs.

Add new func util.kernel_version which returns a tuple of ints (major, minor)

Signed-off-by: Eduardo Otubo otubo@redhat.com
---
 cloudinit/config/cc_mounts.py | 8 +++++---
 cloudinit/util.py             | 4 ++++
 2 files changed, 9 insertions(+), 3 deletions(-)

(limited to 'cloudinit')

diff --git a/cloudinit/config/cc_mounts.py b/cloudinit/config/cc_mounts.py
index 773b8285..54f2f878 100644
--- a/cloudinit/config/cc_mounts.py
+++ b/cloudinit/config/cc_mounts.py
@@ -65,7 +65,7 @@ swap file is created.
 from string import whitespace
 
 import logging
-import os.path
+import os
 import re
 
 from cloudinit import type_utils
@@ -263,7 +263,8 @@ def create_swapfile(fname: str, size: str) -> None:
 
     fstype = util.get_mount_info(swap_dir)[1]
 
-    if fstype in ("xfs", "btrfs"):
+    if (fstype == "xfs" and
+            util.kernel_version() < (4, 18)) or fstype == "btrfs":
         create_swap(fname, size, "dd")
     else:
         try:
@@ -273,7 +274,8 @@ def create_swapfile(fname: str, size: str) -> None:
             LOG.warning("Will attempt with dd.")
             create_swap(fname, size, "dd")
 
-    util.chmod(fname, 0o600)
+    if os.path.exists(fname):
+        util.chmod(fname, 0o600)
     try:
         subp.subp(['mkswap', fname])
     except subp.ProcessExecutionError:
diff --git a/cloudinit/util.py b/cloudinit/util.py
index 624c560d..edd37039 100644
--- a/cloudinit/util.py
+++ b/cloudinit/util.py
@@ -68,6 +68,10 @@ CONTAINER_TESTS = (['systemd-detect-virt', '--quiet', '--container'],
                    ['lxc-is-container'])
 
 
+def kernel_version():
+    return tuple(map(int, os.uname().release.split('.')[:2]))
+
+
 @lru_cache()
 def get_dpkg_architecture(target=None):
     """Return the sanitized string output by `dpkg --print-architecture`.
-- 
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