applied: [PATCH 0/2]: client: pxar: make payload-offset handling more robust

[Thomas Lamprecht <t.lamprecht@proxmox.com>]

The strict payload-offset check added in pxar 1.0.1 rejects any
PXAR_PAYLOAD_REF whose offset is not strictly greater than the
encoder's previously recorded one. A producer-side bug in pre-1.0.1
clients let archives be written that violate that invariant: when a
cache-range discontinuity opens between two flushes and the previous
flush held its last chunk back for continuation, dedup against the
next range's first chunk could collapse the held chunk away without
ever injecting its bytes. payload_write_position then trails the
previous_payload_offset recorded in the same flush, and the next
add_payload_ref produces a backwards offset.

With such an archive on disk, every later metadata-mode incremental
backup aborts on the strict check until the chain is cycled out via
--change-detection-mode=data.

Patch 1 fixes the producer site: a held chunk is now injected explicitly
when a cache-range discontinuity is detected, before update_range, so
no held chunk can survive across a hole.

Patch 2 lets existing affected archives "self-heal" on next backup: the
Archiver tracks the highest previously-recorded payload offset globally
and treats prev-archive entries with a smaller-or-equal offset as
non-reusable, so they are re-encoded. A per-file warning makes the
fall-back visible. Tracking is intentionally global so inversions that
span cache ranges are caught too.

Healthy archives written on or after pxar 1.0.1 cannot trigger the
fall-back since the encoder already enforces strict monotonicity.

tldr: avoids creating new backups that break our invariant and tries
best to recover setups (new) backups, which should address some reports
in the forum [0].

[0]: https://forum.proxmox.com/threads/183043/

Thomas Lamprecht (2):
  client: pxar: inject held chunk on cache-range discontinuity
  client: pxar: re-encode files with non-monotonic previous offsets

 pbs-client/src/pxar/create.rs | 123 ++++++++++++++++++++++++++++++++++
 1 file changed, 123 insertions(+)

-- 
2.47.3