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

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

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].

The second patch changes the location of the `.lock` file to the `/run/proxmox-backup/locks`
tmpfs directory. Like this we don't need to lazy-lock anything and we can keep the lockfile
open all the time. Unmounting datastores is now possible as the lock file is not on the
datastore mount anymore.

Another thing is noticed is that datastores that are not available (e.g. have been unmounted)
don't display an error on the ui. That means the only way to see if a datastore is online is
to either start a gc or verify run. An idea for a future patch would be to check if the
datastore exists and (maybe) even automatically set the maintenance mode to `offline` if it
doesn't exist?

[0]: https://man7.org/linux/man-pages/man2/fcntl.2.html

Changes since version 1:
 - create directory path if it doesn't exist. (f.e. on my instance the `locks` directory 
   did not exist yet)



proxmox:

Gabriel Goller (1):
  process_locker: use ofd locking

 proxmox-sys/src/process_locker.rs | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)


proxmox-backup:

Gabriel Goller (1):
  datastore: store datastore lock on tmpfs

 pbs-datastore/src/chunk_store.rs | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)


Summary over all repositories:
  2 files changed, 23 insertions(+), 14 deletions(-)

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