cache: sentinel to invalidate the chunk index during fragment deletion#9908
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mr-raj12 wants to merge 3 commits into
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cache: sentinel to invalidate the chunk index during fragment deletion#9908mr-raj12 wants to merge 3 commits into
mr-raj12 wants to merge 3 commits into
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…ex fragments (borgbackup#9904) An interrupted fragment deletion could leave a subset that build_chunkindex_from_repo trusts as a complete index; the sentinel now forces a rebuild from packs instead.
Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## master #9908 +/- ##
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+ Coverage 85.13% 85.27% +0.14%
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Files 93 93
Lines 15899 15932 +33
Branches 2428 2435 +7
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+ Hits 13535 13586 +51
+ Misses 1654 1636 -18
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ThomasWaldmann
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Jul 14, 2026
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in a future PR, we will also need to refactor these functions into a class dealing with index management.
…pace Store the marker as config/chunkindex-invalid instead of an all-zeros index/ fragment name, so it can never collide with a real fragment; detect it via a config listing.
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What
Deleting chunk index fragments is not crash safe: if the delete is interrupted partway, the leftover fragments look like a complete index and borg trusts them, so the index ends up missing entries or keeping stale ones.
This writes an "index invalid" marker before the first fragment delete and removes it after the last. While the marker is present, the index is rebuilt from packs on next load.
The marker lives out of band as a
config/chunkindex-invalidobject, not in theindex/namespace, so it can never collide with a realindex/<sha256>fragment. Its presence is detected with aconfig/listing, which bypasses the store cache.The marker only guards non-superset rewrites (full replacements and the invalidate-all path). Repack does not need it, since the fragments it writes already contain the entries it deletes.
Closes #9904