Re: [PATCH proxmox-backup] pbs-key-config: align fsync behavior when storing new/existing key

[Christian Ebner <c.ebner@proxmox.com>]

On 3/24/26 2:16 PM, Fabian Grünbichler wrote:
> On March 24, 2026 11:04 am, Christian Ebner wrote:
>> In case a key is stored by replacing the file contents, the file
>> contents are synced to disk as the corresponding flag is set for
>> proxmox-sys::fs::replace_file(). When creating a new file however,
>> fsync is never called.
>>
>> Align the behaviour by also calling fsync in case of storing the key
>> to a new file.
>>
>> Signed-off-by: Christian Ebner <c.ebner@proxmox.com>
>> ---
>> Noticed while evaluating to reuse this method to store key
>> information to be used by push sync jobs.
>>
>>   pbs-key-config/src/lib.rs | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/pbs-key-config/src/lib.rs b/pbs-key-config/src/lib.rs
>> index 0bcd5338c..71a49dd78 100644
>> --- a/pbs-key-config/src/lib.rs
>> +++ b/pbs-key-config/src/lib.rs
>> @@ -1,5 +1,6 @@
>>   use std::io::Write;
>>   use std::path::Path;
>> +use std::os::fd::AsRawFd;
>>   
>>   use anyhow::{bail, format_err, Context, Error};
>>   use serde::{Deserialize, Serialize};
>> @@ -254,6 +255,7 @@ impl KeyConfig {
>>                       .open(path)?;
>>   
>>                   file.write_all(data.as_bytes())?;
>> +                nix::unistd::fsync(file.as_raw_fd())?;
> 
> LGTM in principle, though we could also switch to
> atomic_open_or_create_file ?

Had a look at that as well, that would however create a tempfile first. 
And since we do already have the open file descriptor here and handle 
failure on per-existing files here as expected (which would require 
adding `OFlag::O_EXCL` in the other case), I did not consider this 
further, simply calling fsync seemed the better option for this 
particular case.