cephadm: convert more temporary file writes to use write_new

Some functions are using the pattern:
```
with open(os.open(name + '.new, os.O_CREAT | os.O_WRONLY, 0o600), 'w') as f:
    f.write(...)
    os.rename(name + '.new', name)
```
While it is not entirely clear why this pattern was first used,
it accomplishes the same goal as `write_new` only directly calling
the posix open call. I analyzed the open flags for `write_new` and
these calls using `strace` and noted that the only significant
difference was the lack of O_TRUNC in these cases. Since the ".new"
files should not exist the lack of O_TRUC ought not make any difference.
With this decided we can convert these instances to `write_new`.

Signed-off-by: John Mulligan <jmulligan@redhat.com>

diff --git a/src/cephadm/cephadm.py b/src/cephadm/cephadm.py
index 0434d011c12593da9e920c13269e5b0d77a91e6d..86ac0067a8f8a5e70ae1a399fca2a40790ffb7cc 100755 (executable)
--- a/src/cephadm/cephadm.py
+++ b/src/cephadm/cephadm.py
@@ -4384,9 +4384,8 @@ class MgrListener(Thread):
             for filename in config:
                 if filename in self.agent.required_files:
                     file_path = os.path.join(self.agent.daemon_dir, filename)
-                    with open(os.open(file_path + '.new', os.O_CREAT | os.O_WRONLY, 0o600), 'w') as f:
+                    with write_new(file_path, perms=0o600) as f:
                         f.write(config[filename])
-                        os.rename(file_path + '.new', file_path)
             self.agent.pull_conf_settings()
             self.agent.wakeup()
 
@@ -4447,27 +4446,23 @@ class CephadmAgent():
         for filename in config:
             if filename in self.required_files:
                 file_path = os.path.join(self.daemon_dir, filename)
-                with open(os.open(file_path + '.new', os.O_CREAT | os.O_WRONLY, 0o600), 'w') as f:
+                with write_new(file_path, perms=0o600) as f:
                     f.write(config[filename])
-                    os.rename(file_path + '.new', file_path)
 
         unit_run_path = os.path.join(self.daemon_dir, 'unit.run')
-        with open(os.open(unit_run_path + '.new', os.O_CREAT | os.O_WRONLY, 0o600), 'w') as f:
+        with write_new(unit_run_path, perms=0o600) as f:
             f.write(self.unit_run())
-            os.rename(unit_run_path + '.new', unit_run_path)
 
         meta: Dict[str, Any] = {}
         meta_file_path = os.path.join(self.daemon_dir, 'unit.meta')
         if 'meta_json' in self.ctx and self.ctx.meta_json:
             meta = json.loads(self.ctx.meta_json) or {}
-        with open(os.open(meta_file_path + '.new', os.O_CREAT | os.O_WRONLY, 0o600), 'w') as f:
+        with write_new(meta_file_path, perms=0o600) as f:
             f.write(json.dumps(meta, indent=4) + '\n')
-            os.rename(meta_file_path + '.new', meta_file_path)
 
         unit_file_path = os.path.join(self.ctx.unit_dir, self.unit_name())
-        with open(os.open(unit_file_path + '.new', os.O_CREAT | os.O_WRONLY, 0o600), 'w') as f:
+        with write_new(unit_file_path, perms=0o600) as f:
             f.write(self.unit_file())
-            os.rename(unit_file_path + '.new', unit_file_path)
 
         call_throws(self.ctx, ['systemctl', 'daemon-reload'])
         call(self.ctx, ['systemctl', 'stop', self.unit_name()],