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Put get_trim_pos into the "critical section". Fixes rare journal corruption issue

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The consequence of this issue was that in some very rare cases (only reproduced
under load in CI when running 4+ tests in parallel) small write data written to
journal could overwrite journal entries.

Also add an assert-type safety check to be able to catch this issue in the
future again in case of a regression.
This commit is contained in:
Vitaliy Filippov
2023-06-17 00:06:42 +03:00
parent bdd48e4cf1
commit 86b4682975
3 changed files with 73 additions and 46 deletions
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src/blockstore_flush.cpp
+42 -37
View File
@@ -675,53 +675,58 @@ resume_1:
return false;
}
flusher->trimming = true;
// First update journal "superblock" and only then update <used_start> in memory
await_sqe(12);
*((journal_entry_start*)flusher->journal_superblock) = {
.crc32 = 0,
.magic = JOURNAL_MAGIC,
.type = JE_START,
.size = sizeof(journal_entry_start),
.reserved = 0,
.journal_start = new_trim_pos,
.version = JOURNAL_VERSION,
};
((journal_entry_start*)flusher->journal_superblock)->crc32 = je_crc32((journal_entry*)flusher->journal_superblock);
data->iov = (struct iovec){ flusher->journal_superblock, bs->dsk.journal_block_size };
data->callback = simple_callback_w;
my_uring_prep_writev(sqe, bs->dsk.journal_fd, &data->iov, 1, bs->journal.offset);
wait_count++;
resume_13:
if (wait_count > 0)
// Recheck the position with the "lock" taken
new_trim_pos = bs->journal.get_trim_pos();
if (new_trim_pos != bs->journal.used_start)
{
wait_state = 13;
return false;
}
if (!bs->disable_journal_fsync)
{
await_sqe(20);
my_uring_prep_fsync(sqe, bs->dsk.journal_fd, IORING_FSYNC_DATASYNC);
data->iov = { 0 };
// First update journal "superblock" and only then update <used_start> in memory
await_sqe(12);
*((journal_entry_start*)flusher->journal_superblock) = {
.crc32 = 0,
.magic = JOURNAL_MAGIC,
.type = JE_START,
.size = sizeof(journal_entry_start),
.reserved = 0,
.journal_start = new_trim_pos,
.version = JOURNAL_VERSION,
};
((journal_entry_start*)flusher->journal_superblock)->crc32 = je_crc32((journal_entry*)flusher->journal_superblock);
data->iov = (struct iovec){ flusher->journal_superblock, bs->dsk.journal_block_size };
data->callback = simple_callback_w;
resume_21:
my_uring_prep_writev(sqe, bs->dsk.journal_fd, &data->iov, 1, bs->journal.offset);
wait_count++;
resume_13:
if (wait_count > 0)
{
wait_state = 21;
wait_state = 13;
return false;
}
}
bs->journal.used_start = new_trim_pos;
if (!bs->disable_journal_fsync)
{
await_sqe(20);
my_uring_prep_fsync(sqe, bs->dsk.journal_fd, IORING_FSYNC_DATASYNC);
data->iov = { 0 };
data->callback = simple_callback_w;
resume_21:
if (wait_count > 0)
{
wait_state = 21;
return false;
}
}
bs->journal.used_start = new_trim_pos;
#ifdef BLOCKSTORE_DEBUG
printf("Journal trimmed to %08lx (next_free=%08lx)\n", bs->journal.used_start, bs->journal.next_free);
printf("Journal trimmed to %08lx (next_free=%08lx)\n", bs->journal.used_start, bs->journal.next_free);
#endif
if (bs->journal.flush_journal && !flusher->flush_queue.size())
{
assert(bs->journal.used_start == bs->journal.next_free);
printf("Journal flushed\n");
exit(0);
}
}
flusher->trimming = false;
}
if (bs->journal.flush_journal && !flusher->flush_queue.size())
{
assert(bs->journal.used_start == bs->journal.next_free);
printf("Journal flushed\n");
exit(0);
}
}
// All done
flusher->active_flushers--;