[pbs-devel] [PATCH proxmox proxmox-backup 0/9] fix #5892: check atime update is honored

[Christian Ebner]

These patches add a check to phase 1 of garbage collection in order
to detect when the filesystem backing the chunk store does not honor
atime updates. This avoids possible data loss for situations where
garbage collection could otherwise delete chunks still referenced by
a backup snaphost's index file.

The check is performed by inserting a fixed size 4 MiB unencrypted and
compressed chunk of all-zeros. The check is performed by setting the
atime to 1 second in the past followed by setting it to now in order to
test if atime updates are honored immediately. The test is performed
on datastore creation for early detection and before garbage collection
phase 1. The test is enabled by default, but an opt-out option can be
set via the datastore tuning parameters for backwards compatibility.

Further, add a datastore tuning parameter to reduce the wait period for
chunk removal in phase 2 of garbage collection. Make this conditional on
the atime update check being enabled and successful, to avoid possible
data loss.

Most notable changes sice version 1 (thanks Fabian and Thomas for
comments and suggestions):
- Optimize check by using the all zero chunk
- Enable the check by default and fail GC job if not honored, but allow
  to opt-out
- Add GC wait period tuning option

Link to the issue in the bugtracker:
https://bugzilla.proxmox.com/show_bug.cgi?id=5982

proxmox:

Christian Ebner (2):
  pbs api types: add check garbage collection atime updates flag
  pbs api types: add option to set GC chunk cleanup wait period

 pbs-api-types/src/datastore.rs | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

proxmox-backup:

Christian Ebner (7):
  datastore: move utimensat() related constants to module scope
  fix #5982: garbage collection: check atime updates are honored
  ui: expose atime update check flag in datastore tuning options
  docs: mention GC atime update check for tuning options
  datastore: conditionally use custom GC wait period if set
  ui: expose GC wait period in datastore tuning option
  docs: mention gc-wait-period option as datastore tuning parameter

 docs/storage.rst                 | 19 ++++++-
 pbs-datastore/src/chunk_store.rs | 96 +++++++++++++++++++++++++++++---
 pbs-datastore/src/datastore.rs   | 23 ++++++++
 src/api2/config/datastore.rs     |  1 +
 www/Utils.js                     |  9 +++
 www/datastore/OptionView.js      | 17 ++++++
 6 files changed, 153 insertions(+), 12 deletions(-)

-- 
2.39.5