dedupe: stop instead of spinning when a round makes no progress (#396/#407) - #408
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dedupe: stop instead of spinning when a round makes no progress (#396/#407)#408martinus wants to merge 1 commit into
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…fasheh#396/markfasheh#407) The dedupe ioctl loop requeues any request the kernel didn't finish. If a round deduped zero bytes but returned no error (status 0), every request was requeued unchanged and the next identical ioctl returned the same zero - an infinite loop at 100% CPU, reported as hangs on 0.15. Break out when a full round moves no bytes and requests are still queued, splicing them to completed (accounted as not-deduped) rather than looping forever. Productive dedupe always advances >0 bytes per round - a large extent progresses in fs-block chunks - so this never cuts real work short. Fixes: markfasheh#396 Fixes: markfasheh#407 Co-Authored-By: Claude Opus 4.8 <[email protected]>
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What this fixes
The dedupe ioctl loop requeues any request the kernel didn't fully finish. If a round deduped zero bytes but returned no error (
info[i].status == 0), every still-queued request was requeued unchanged — and the next identicalFIDEDUPERANGEreturns the same zero. That's an infinite loop.What happens without the fix
duperemovehangs, pinning a CPU core at 100% and never completing the run. It's been reported as hangs on 0.15.x (#396, #407).The fix
After each round, sum the bytes deduped. If a full round moved no bytes while requests are still queued, stop: splice the stuck requests onto the completed list (accounted as not-deduped) instead of reissuing the same no-op ioctl forever.
Productive dedupe always advances >0 bytes per round — a large extent progresses in fs-block chunks — so this never cuts real work short. Verified a 256 MB extent (8 rounds) still fully shares, and the guard never fired across the integration suite.
Fixes: #396
Fixes: #407