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Fix journal trimming

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1) Update journal's used_start in memory only after updating journal superblock.
Doing the opposite is incorrect because part of the journal will be lost if writers
overwrite its old beginning.

2) Sync journal device after updating the superblock.

3) Do not trim in rollback and init because trimming there would also require
updating the superblock. And the only reason to trim in both those places was
to unblock writers. And a guaranteed unblocking method will follow in the next
commit :)
This commit is contained in:
Vitaliy Filippov
2020-10-24 01:08:33 +03:00
parent 99c45bb5ed
commit 5fbe36198a
6 changed files with 50 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files
blockstore_flush.cpp
+39 -4
View File
@@ -8,10 +8,12 @@ journal_flusher_t::journal_flusher_t(int flusher_count, blockstore_impl_t *bs)
this->bs = bs;
this->flusher_count = flusher_count;
dequeuing = false;
trimming = false;
active_flushers = 0;
syncing_flushers = 0;
// FIXME: allow to configure flusher_start_threshold and journal_trim_interval
flusher_start_threshold = bs->journal_block_size / sizeof(journal_entry_stable);
journal_trim_interval = flusher_start_threshold;
journal_trim_interval = 512;
journal_trim_counter = 0;
journal_superblock = bs->journal.inmemory ? bs->journal.buffer : memalign_or_die(MEM_ALIGNMENT, bs->journal_block_size);
co = new journal_flusher_co[flusher_count];
@@ -172,6 +174,12 @@ bool journal_flusher_co::loop()
goto resume_17;
else if (wait_state == 18)
goto resume_18;
else if (wait_state == 19)
goto resume_19;
else if (wait_state == 20)
goto resume_20;
else if (wait_state == 21)
goto resume_21;
resume_0:
if (!flusher->flush_queue.size() || !flusher->dequeuing)
{
@@ -484,9 +492,18 @@ resume_1:
if (!((++flusher->journal_trim_counter) % flusher->journal_trim_interval) || flusher->trim_wanted > 0)
{
flusher->journal_trim_counter = 0;
if (bs->journal.trim())
new_trim_pos = bs->journal.get_trim_pos();
if (new_trim_pos != bs->journal.used_start)
{
// Update journal "superblock"
resume_19:
// Wait for other coroutines trimming the journal, if any
if (flusher->trimming)
{
wait_state = 19;
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,
@@ -494,7 +511,7 @@ resume_1:
.type = JE_START,
.size = sizeof(journal_entry_start),
.reserved = 0,
.journal_start = bs->journal.used_start,
.journal_start = new_trim_pos,
};
((journal_entry_start*)flusher->journal_superblock)->crc32 = je_crc32((journal_entry*)flusher->journal_superblock);
data->iov = (struct iovec){ flusher->journal_superblock, bs->journal_block_size };
@@ -507,6 +524,24 @@ resume_1:
wait_state = 13;
return false;
}
if (!bs->disable_journal_fsync)
{
await_sqe(20);
my_uring_prep_fsync(sqe, bs->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);
#endif
flusher->trimming = false;
}
}
// All done