[pbs-devel] [PATCH proxmox-backup v5 0/5] refactor datastore locking to use tmpfs

[Stefan Sterz <s.sterz@proxmox.com>]

The first commit fixes a bug in the `BackupGroup`'s
`relative_group_path()` method. It would return the full path instead
of a path relative to a datastore. Since this function wasn't used
before this series, afaict, this fix should be unproblematic.

The rests of this series refactors the locking mechanism inside the
`DataStore`, `BackupDir` and `BackupGroup traits. In a first step
locking methods are added and the existing code is refactored to use
them.  Commit three uses the fixed `relative_group_path()` method to
derive a lock file name under '/run' for each group/snapshot. It also
adds double stat'ing.

The fourth commit refactors locking for manifests and brings it
in-line with the group/snapshot locks. Finally the fifth commit fixes
a race condition when changing the owner of a datastore.

As far as I can tell, the addition of namespaces did not create a need
for more locking.

changes from v4 (thanks @ Wolfgang Bumiller):
* stop using `to_string_lossy()`
* switch funtion signature of `create_locked_backup_group()` and 
  `create_locked_backup_dir` to use the `Arc` version of a datastore.
* smaller clippy fixes
* rebased on current master

changes from v3:
* moved patch 2 to the front so it can be applied separatelly more
  easily
* rebased on current master

changes from v2:
* different encoding scheme for lock file names
* refactored locking methods to be used by the new BackupDir and
  BackupGroup traits
* adapted lock file names to include namespaces

changes from v1 (thanks @ Wolfgang Bumiller & Thomas Lamprecht):
* split adding locking helpers and move '/run' into two commits
* instead of stat'ing the path of lock file twice, only use the file
  descriptor for one of the stat'ing procedures instead
* several improvements to helper functions and documentation


Stefan Sterz (5):
  fix: datastore: make relative_group_path() return relative path
  fix #3935: datastore/api/backup: add lock helpers to backup dir/group
  fix #3935: datastore/api/backup: move datastore locking to '/run'
  fix #3935: datastore: move manifest locking to new locking method
  fix: api: avoid race condition in set_backup_owner

 pbs-config/src/lib.rs                |   7 ++
 pbs-datastore/src/backup_info.rs     | 154 ++++++++++++++++++++++-----
 pbs-datastore/src/datastore.rs       |  72 +++++--------
 pbs-datastore/src/snapshot_reader.rs |  23 ++--
 src/api2/admin/datastore.rs          |   8 +-
 src/api2/backup/environment.rs       |   5 +-
 src/api2/backup/mod.rs               |   8 +-
 src/api2/reader/mod.rs               |   7 +-
 src/backup/verify.rs                 |  11 +-
 9 files changed, 192 insertions(+), 103 deletions(-)

-- 
2.30.2