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ChunkerFixed: do not take a short read for EOF (1.4-maint) - #10563
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ThomasWaldmann merged 2 commits intoOct 29, 2026
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blockify() stopped reading the whole input as soon as a read returned less than the requested block size. A short read is not EOF though, e.g. when reading from a pipe: "borg create --read-special" with the fixed chunker archived only the first 64 KiB of a FIFO's content (seen on macOS) and silently dropped the rest. Now keep reading until the block is complete or a read returns nothing. Filling the block also keeps the chunk boundaries at fixed offsets. master is not affected any more, see borgbackup#10166. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## 1.4-maint #10563 +/- ##
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- Coverage 82.11% 82.09% -0.02%
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Files 38 38
Lines 11480 11485 +5
Branches 1808 1810 +2
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+ Hits 9427 9429 +2
- Misses 1467 1469 +2
- Partials 586 587 +1 ☔ View full report in Codecov by Harness. |
Same behaviour and same read calls, just one loop instead of a first read followed by a loop for the rest of the block. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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chunkify() stopped reading the whole input as soon as a read returned less than the requested block size. A short read is not EOF though, e.g. when reading from a pipe: "borg create --read-special" with the fixed chunker archived only the first 64 KiB of a FIFO's content (seen on macOS) and silently dropped the rest. Now keep reading until the block is complete or a read returns nothing. Filling the block also keeps the chunk boundaries at fixed offsets. Port of #10563 from 1.4-maint. master is not affected any more, see #10166. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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ChunkerFixed.chunkify()took any short read (got < wanted) for EOF and stopped. Reads from a pipe or FIFO often return less than requested, soborg create --read-special --chunker-params fixed,...could silently archive only a truncated part of a FIFO's content. On macOS, 3 MiB written into a pipe came out as only 64 KiB of chunks.After a short read, the chunker now keeps reading until the block is full or a read returns no data (real EOF). Filling the block also keeps the chunk boundaries at fixed offsets, so dedup is not affected.
Master fixed this as part of #10166 (in
chunkers/reader.pyx). That code was rewritten on master, so this is a separate fix for 1.4-maint, not a cherry-pick.Tests: the new
test_chunkify_short_readsuses a file object that returns at most 100 bytes per read, with and without a header block. It fails without the fix and passes with it.Note: the
posix_fadvise()/ESPIPEfix for the same scenario is not part of this PR (it was pushed after the merge), see #10569.🤖 Generated with Claude Code