Re: [pbs-devel] [PATCH v2 proxmox{, -backup} 0/2] Move ProcessLocker to tmpfs

[Gabriel Goller <g.goller@proxmox.com>]

On 12/6/23 14:41, Fabian Grünbichler wrote:
>>
>> Gabriel Goller <g.goller@proxmox.com> hat am 06.12.2023 14:28 CET 
>> geschrieben: This moves the `ProcessLocker`'s `.lock` file to 
>> `/run/proxmox-backup/locks` (tmpfs). The first patch only converts 
>> all the `F_SETLK` flags to `F_OFD_SETLK` flags. This changes normal 
>> locks, which are based on the process, to locks based on an open file 
>> descriptor. This actually doesn't change anything, because we use 
>> mutexes, so the lock is already thread-safe. It would be cleaner 
>> though and would safe us from weird quirks like closing the lock-file 
>> which would drop all the locks when using the POSIX `F_SETLK`. See 
>> more here [0].
>>
> this might be moot, since most likely both patches go in at the same 
> time, is this change reload/upgrade-compatible? i.e., if an old 
> proxmox-backup(-proxy) process is (still) running that has the lock 
> open with F_SETLK, and the new one obtains it using F_OFD_SETLK, is 
> the behaviour still correct? (the other direction might be interesting 
> too, but can only happen on an unsupported downgrade)
>
Just spoke with Stefan Sterz about this and we will probably 
apply/release this with a major version bump (kernel update), so that 
the user
is forced to reboot the system (same as with his tmpfs locking series).
I don't think there is another way, because the lockfiles get moved to 
another dir. Although F_SETLK and F_OFD_SETLK should be compatible,
so having one process use F_SETLK and another F_OFD_SETLK *should* still 
work (don't take my word for it though).