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tromcho.net/blockstore_sync.cpp
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Vitaliy Filippov 571be0f380 Make deletions instantly stable 
"2-phase" (write->stabilize) process is pointless for deletions because it
doesn't protect us from incomplete objects. This happens because it removes
the version information from metadata after stabilization. Deletions require
"3-phase" process with a potentially very long 3rd phase.

So, deletions will be allowed to generate degraded and incomplete objects,
and for it to not affect users' ability to delete something, the cluster
will allow to delete whole inodes while storing a list of them in etcd.
Proper TRIM will be impossible until the implementation of the aforementioned
"3-phase" process, though.

By the way, this change also fixes a possible write stall after rebalancing
which was caused by the lack of "stabilize delete" operations.
2020-06-02 23:45:22 +03:00

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#include "blockstore_impl.h"
#define SYNC_HAS_SMALL 1
#define SYNC_HAS_BIG 2
#define SYNC_DATA_SYNC_SENT 3
#define SYNC_DATA_SYNC_DONE 4
#define SYNC_JOURNAL_WRITE_SENT 5
#define SYNC_JOURNAL_WRITE_DONE 6
#define SYNC_JOURNAL_SYNC_SENT 7
#define SYNC_DONE 8
int blockstore_impl_t::dequeue_sync(blockstore_op_t *op)
{
if (PRIV(op)->op_state == 0)
{
stop_sync_submitted = false;
PRIV(op)->sync_big_writes.swap(unsynced_big_writes);
PRIV(op)->sync_small_writes.swap(unsynced_small_writes);
PRIV(op)->sync_small_checked = 0;
PRIV(op)->sync_big_checked = 0;
unsynced_big_writes.clear();
unsynced_small_writes.clear();
if (PRIV(op)->sync_big_writes.size() > 0)
PRIV(op)->op_state = SYNC_HAS_BIG;
else if (PRIV(op)->sync_small_writes.size() > 0)
PRIV(op)->op_state = SYNC_HAS_SMALL;
else
PRIV(op)->op_state = SYNC_DONE;
// Always add sync to in_progress_syncs because we clear unsynced_big_writes and unsynced_small_writes
PRIV(op)->prev_sync_count = in_progress_syncs.size();
PRIV(op)->in_progress_ptr = in_progress_syncs.insert(in_progress_syncs.end(), op);
}
continue_sync(op);
// Always dequeue because we always add syncs to in_progress_syncs
return 1;
}
int blockstore_impl_t::continue_sync(blockstore_op_t *op)
{
auto cb = [this, op](ring_data_t *data) { handle_sync_event(data, op); };
if (PRIV(op)->op_state == SYNC_HAS_SMALL)
{
// No big writes, just fsync the journal
for (; PRIV(op)->sync_small_checked < PRIV(op)->sync_small_writes.size(); PRIV(op)->sync_small_checked++)
{
if (IS_IN_FLIGHT(dirty_db[PRIV(op)->sync_small_writes[PRIV(op)->sync_small_checked]].state))
{
// Wait for small inflight writes to complete
return 0;
}
}
if (journal.sector_info[journal.cur_sector].dirty)
{
// Write out the last journal sector if it happens to be dirty
BS_SUBMIT_GET_ONLY_SQE(sqe);
prepare_journal_sector_write(journal, journal.cur_sector, sqe, cb);
PRIV(op)->min_flushed_journal_sector = PRIV(op)->max_flushed_journal_sector = 1 + journal.cur_sector;
PRIV(op)->pending_ops = 1;
PRIV(op)->op_state = SYNC_JOURNAL_WRITE_SENT;
return 1;
}
else
{
PRIV(op)->op_state = SYNC_JOURNAL_WRITE_DONE;
}
}
if (PRIV(op)->op_state == SYNC_HAS_BIG)
{
for (; PRIV(op)->sync_big_checked < PRIV(op)->sync_big_writes.size(); PRIV(op)->sync_big_checked++)
{
if (IS_IN_FLIGHT(dirty_db[PRIV(op)->sync_big_writes[PRIV(op)->sync_big_checked]].state))
{
// Wait for big inflight writes to complete
return 0;
}
}
// 1st step: fsync data
if (!disable_data_fsync)
{
BS_SUBMIT_GET_SQE(sqe, data);
my_uring_prep_fsync(sqe, data_fd, IORING_FSYNC_DATASYNC);
data->iov = { 0 };
data->callback = cb;
PRIV(op)->min_flushed_journal_sector = PRIV(op)->max_flushed_journal_sector = 0;
PRIV(op)->pending_ops = 1;
PRIV(op)->op_state = SYNC_DATA_SYNC_SENT;
return 1;
}
else
{
PRIV(op)->op_state = SYNC_DATA_SYNC_DONE;
}
}
if (PRIV(op)->op_state == SYNC_DATA_SYNC_DONE)
{
for (; PRIV(op)->sync_small_checked < PRIV(op)->sync_small_writes.size(); PRIV(op)->sync_small_checked++)
{
if (IS_IN_FLIGHT(dirty_db[PRIV(op)->sync_small_writes[PRIV(op)->sync_small_checked]].state))
{
// Wait for small inflight writes to complete
return 0;
}
}
// 2nd step: Data device is synced, prepare & write journal entries
// Check space in the journal and journal memory buffers
blockstore_journal_check_t space_check(this);
if (!space_check.check_available(op, PRIV(op)->sync_big_writes.size(), sizeof(journal_entry_big_write), 0))
{
return 0;
}
// Get SQEs. Don't bother about merging, submit each journal sector as a separate request
struct io_uring_sqe *sqe[space_check.sectors_required];
for (int i = 0; i < space_check.sectors_required; i++)
{
BS_SUBMIT_GET_SQE_DECL(sqe[i]);
}
// Prepare and submit journal entries
auto it = PRIV(op)->sync_big_writes.begin();
int s = 0, cur_sector = -1;
if ((journal_block_size - journal.in_sector_pos) < sizeof(journal_entry_big_write) &&
journal.sector_info[journal.cur_sector].dirty)
{
if (cur_sector == -1)
PRIV(op)->min_flushed_journal_sector = 1 + journal.cur_sector;
cur_sector = journal.cur_sector;
prepare_journal_sector_write(journal, cur_sector, sqe[s++], cb);
}
while (it != PRIV(op)->sync_big_writes.end())
{
journal_entry_big_write *je = (journal_entry_big_write*)
prefill_single_journal_entry(journal, JE_BIG_WRITE, sizeof(journal_entry_big_write));
dirty_db[*it].journal_sector = journal.sector_info[journal.cur_sector].offset;
journal.sector_info[journal.cur_sector].dirty = false;
journal.used_sectors[journal.sector_info[journal.cur_sector].offset]++;
#ifdef BLOCKSTORE_DEBUG
printf(
"journal offset %08lx is used by %lu:%lu v%lu (%lu refs)\n",
dirty_db[*it].journal_sector, it->oid.inode, it->oid.stripe, it->version,
journal.used_sectors[journal.sector_info[journal.cur_sector].offset]
);
#endif
je->oid = it->oid;
je->version = it->version;
je->offset = dirty_db[*it].offset;
je->len = dirty_db[*it].len;
je->location = dirty_db[*it].location;
je->crc32 = je_crc32((journal_entry*)je);
journal.crc32_last = je->crc32;
it++;
if (cur_sector != journal.cur_sector)
{
if (cur_sector == -1)
PRIV(op)->min_flushed_journal_sector = 1 + journal.cur_sector;
cur_sector = journal.cur_sector;
prepare_journal_sector_write(journal, cur_sector, sqe[s++], cb);
}
}
PRIV(op)->max_flushed_journal_sector = 1 + journal.cur_sector;
PRIV(op)->pending_ops = s;
PRIV(op)->op_state = SYNC_JOURNAL_WRITE_SENT;
return 1;
}
if (PRIV(op)->op_state == SYNC_JOURNAL_WRITE_DONE)
{
if (!disable_journal_fsync)
{
BS_SUBMIT_GET_SQE(sqe, data);
my_uring_prep_fsync(sqe, journal.fd, IORING_FSYNC_DATASYNC);
data->iov = { 0 };
data->callback = cb;
PRIV(op)->pending_ops = 1;
PRIV(op)->op_state = SYNC_JOURNAL_SYNC_SENT;
return 1;
}
else
{
PRIV(op)->op_state = SYNC_DONE;
}
}
if (PRIV(op)->op_state == SYNC_DONE)
{
return ack_sync(op);
}
return 1;
}
void blockstore_impl_t::handle_sync_event(ring_data_t *data, blockstore_op_t *op)
{
live = true;
if (data->res != data->iov.iov_len)
{
throw std::runtime_error(
"write operation failed ("+std::to_string(data->res)+" != "+std::to_string(data->iov.iov_len)+
"). in-memory state is corrupted. AAAAAAAaaaaaaaaa!!!111"
);
}
PRIV(op)->pending_ops--;
if (PRIV(op)->pending_ops == 0)
{
// Release used journal sectors
release_journal_sectors(op);
// Handle states
if (PRIV(op)->op_state == SYNC_DATA_SYNC_SENT)
{
PRIV(op)->op_state = SYNC_DATA_SYNC_DONE;
}
else if (PRIV(op)->op_state == SYNC_JOURNAL_WRITE_SENT)
{
PRIV(op)->op_state = SYNC_JOURNAL_WRITE_DONE;
}
else if (PRIV(op)->op_state == SYNC_JOURNAL_SYNC_SENT)
{
PRIV(op)->op_state = SYNC_DONE;
ack_sync(op);
}
else
{
throw std::runtime_error("BUG: unexpected sync op state");
}
}
}
int blockstore_impl_t::ack_sync(blockstore_op_t *op)
{
if (PRIV(op)->op_state == SYNC_DONE && PRIV(op)->prev_sync_count == 0)
{
// Remove dependency of subsequent syncs
auto it = PRIV(op)->in_progress_ptr;
int done_syncs = 1;
++it;
// Acknowledge sync
ack_one_sync(op);
while (it != in_progress_syncs.end())
{
auto & next_sync = *it++;
PRIV(next_sync)->prev_sync_count -= done_syncs;
if (PRIV(next_sync)->prev_sync_count == 0 && PRIV(next_sync)->op_state == SYNC_DONE)
{
done_syncs++;
// Acknowledge next_sync
ack_one_sync(next_sync);
}
}
return 2;
}
return 0;
}
void blockstore_impl_t::ack_one_sync(blockstore_op_t *op)
{
// Handle states
for (auto it = PRIV(op)->sync_big_writes.begin(); it != PRIV(op)->sync_big_writes.end(); it++)
{
#ifdef BLOCKSTORE_DEBUG
printf("Ack sync big %lu:%lu v%lu\n", it->oid.inode, it->oid.stripe, it->version);
#endif
auto & unstab = unstable_writes[it->oid];
unstab = unstab < it->version ? it->version : unstab;
auto dirty_it = dirty_db.find(*it);
dirty_it->second.state = ST_D_SYNCED;
dirty_it++;
while (dirty_it != dirty_db.end() && dirty_it->first.oid == it->oid)
{
if (dirty_it->second.state == ST_J_WAIT_BIG)
{
dirty_it->second.state = ST_J_IN_FLIGHT;
}
dirty_it++;
}
}
for (auto it = PRIV(op)->sync_small_writes.begin(); it != PRIV(op)->sync_small_writes.end(); it++)
{
#ifdef BLOCKSTORE_DEBUG
printf("Ack sync small %lu:%lu v%lu\n", it->oid.inode, it->oid.stripe, it->version);
#endif
auto & unstab = unstable_writes[it->oid];
unstab = unstab < it->version ? it->version : unstab;
if (dirty_db[*it].state == ST_DEL_WRITTEN)
{
dirty_db[*it].state = ST_DEL_SYNCED;
// Deletions are treated as immediately stable
mark_stable(*it);
}
else /* == ST_J_WRITTEN */
{
dirty_db[*it].state = ST_J_SYNCED;
}
}
in_progress_syncs.erase(PRIV(op)->in_progress_ptr);
op->retval = 0;
FINISH_OP(op);
}
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