Store v2: Wait for fsyncs submitted by other operations before completing a sync #107

koolkhel · 2026-10-26T21:02:33+03:00

koolkhel commented

2026-10-26 21:02:33 +03:00

Description

do_sync() returned at once when nothing was left unsynced, but these counters are reset when an fsync is submitted, not when it completes. So a stabilize or rollback whose metadata block was written before another operation submitted its fsync completed before that fsync did, and a power outage could undo it: test_blockstore_chaos --seed 105267292 sees a rolled back version come back.

Wait until everything completed is fsynced instead. A waiting sync still counts as unfinished, so that the next one doesn't overtake it and have its pending fsyncs reset.

Tested:

test_blockstore: new test_rollback_waits_for_inflight_fsync (fails on master, the rollback completes while the fsync is held)
test_blockstore_chaos --seed 105267292 passes
test_blockstore_chaos: the default 200-seed sweep, and earlier 1200 seeds (--seeds 1-48 --random 1152), all pass

Contributor Name

Yury Luneff (MIND Software LLC, https://mindsw.io)

CLA

I accept Vitastor CLA agreement: https://git.yourcmc.ru/vitalif/vitastor/src/branch/master/CLA-en.md

### Description `do_sync()` returned at once when nothing was left unsynced, but these counters are reset when an fsync is submitted, not when it completes. So a stabilize or rollback whose metadata block was written before another operation submitted its fsync completed before that fsync did, and a power outage could undo it: `test_blockstore_chaos --seed 105267292` sees a rolled back version come back. Wait until everything completed is fsynced instead. A waiting sync still counts as unfinished, so that the next one doesn't overtake it and have its pending fsyncs reset. Tested: - `test_blockstore`: new `test_rollback_waits_for_inflight_fsync` (fails on master, the rollback completes while the fsync is held) - `test_blockstore_chaos --seed 105267292` passes - `test_blockstore_chaos`: the default 200-seed sweep, and earlier 1200 seeds (`--seeds 1-48 --random 1152`), all pass ### Contributor Name Yury Luneff (MIND Software LLC, https://mindsw.io) ### CLA - [x] I accept Vitastor CLA agreement: https://git.yourcmc.ru/vitalif/vitastor/src/branch/master/CLA-en.md

koolkhel added 1 commit 2026-10-26 21:02:34 +03:00

Store v2: Wait for fsyncs submitted by other operations before completing a sync 933f2302df

do_sync() returned at once when nothing was left unsynced, but these
counters are reset when an fsync is submitted, not when it completes. So
a stabilize or rollback whose metadata block was written before another
operation submitted its fsync completed before that fsync did, and a
power outage could undo it: test_blockstore_chaos --seed 105267292 sees
a rolled back version come back.

Wait until everything completed is fsynced instead. A waiting sync still
counts as unfinished, so that the next one doesn't overtake it and have
its pending fsyncs reset.

vitalif reviewed 2026-10-27 00:30:40 +03:00

src/blockstore/blockstore_sync.cpp

						
				@@ -107,6 +107,16 @@ int blockstore_impl_t::do_sync(blockstore_op_t *op, int base_state)

				    }

				    if (!has_unsynced())

				    {

				        if ((!dsk.disable_meta_fsync || !dsk.disable_journal_fsync) &&

vitalif commented

2026-10-27 00:30:40 +03:00

тут точно обе правки нужны? выглядит как будто то ли два разных кейса поправлено, то ли один, но двумя способами. верхней правки не хватит ли?

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Reference: vitalif/vitastor#107

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