133 lines
4.3 KiB
C++
133 lines
4.3 KiB
C++
#include "blockstore.h"
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// Stabilize small write:
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// 1) Copy data from the journal to the data device
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// Sync it before writing metadata if we want to keep metadata consistent
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// Overall it's optional because it can be replayed from the journal until
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// it's cleared, and reads are also fulfilled from the journal
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// 2) Increase version on the metadata device and sync it
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// 3) Advance clean_db entry's version, clear previous journal entries
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//
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// This makes 1 4K small write+sync look like:
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// 512b+4K (journal) + sync + 512b (journal) + sync + 4K (data) [+ sync?] + 512b (metadata) + sync.
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// WA = 2.375. It's not the best, SSD FTL-like redirect-write with defragmentation
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// could probably be lower even with defragmentation. But it's fixed and it's still
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// better than in Ceph. :)
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// Stabilize big write:
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// 1) Copy metadata from the journal to the metadata device
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// 2) Move dirty_db entry to clean_db and clear previous journal entries
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//
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// This makes 1 128K big write+sync look like:
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// 128K (data) + sync + 512b (journal) + sync + 512b (journal) + sync + 512b (metadata) + sync.
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// WA = 1.012. Very good :)
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// AND We must do it in batches, for the sake of reduced fsync call count
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int blockstore::dequeue_stable(blockstore_operation *op)
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{
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auto dirty_it = dirty_db.find((obj_ver_id){
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.oid = op->oid,
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.version = op->version,
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});
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if (dirty_it == dirty_db.end())
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{
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auto clean_it = clean_db.find(op->oid);
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if (clean_it == clean_db.end() || clean_it->second.version < op->version)
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{
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// No such object version
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op->retval = EINVAL;
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}
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else
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{
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// Already stable
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op->retval = 0;
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}
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op->callback(op);
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return 1;
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}
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else if (IS_UNSYNCED(dirty_it->second.state))
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{
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// Object not synced yet. Caller must sync it first
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op->retval = EAGAIN;
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op->callback(op);
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return 1;
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}
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else if (IS_STABLE(dirty_it->second.state))
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{
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// Already stable
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op->retval = 0;
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op->callback(op);
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return 1;
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}
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// Check journal space
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blockstore_journal_check_t space_check(this);
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if (!space_check.check_available(op, 1, sizeof(journal_entry_stable), 0))
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{
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return 0;
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}
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// There is sufficient space. Get SQE
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BS_SUBMIT_GET_SQE(sqe, data);
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// Got SQE. Prepare journal sector write
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journal_entry_stable *je = (journal_entry_stable*)prefill_single_journal_entry(journal, JE_STABLE, sizeof(struct journal_entry_stable));
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je->oid = op->oid;
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je->version = op->version;
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je->crc32 = je_crc32((journal_entry*)je);
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journal.crc32_last = je->crc32;
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data->iov = (struct iovec){ journal.sector_buf + 512*journal.cur_sector, 512 };
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data->op = op;
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io_uring_prep_writev(
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sqe, journal.fd, &data->iov, 1, journal.offset + journal.sector_info[journal.cur_sector].offset
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);
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journal.sector_info[journal.cur_sector].usage_count++;
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op->pending_ops = 1;
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op->min_used_journal_sector = op->max_used_journal_sector = 1 + journal.cur_sector;
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return 1;
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}
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int blockstore::continue_stable(blockstore_operation *op)
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{
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return 0;
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}
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void blockstore::handle_stable_event(ring_data_t *data, blockstore_operation *op)
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{
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if (data->res < 0)
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{
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// sync error
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// FIXME: our state becomes corrupted after a write error. maybe do something better than just die
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throw new std::runtime_error("write operation failed. in-memory state is corrupted. AAAAAAAaaaaaaaaa!!!111");
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}
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op->pending_ops--;
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if (op->pending_ops == 0)
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{
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// Mark all dirty_db entries up to op->version as stable
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auto dirty_it = dirty_db.find((obj_ver_id){
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.oid = op->oid,
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.version = op->version,
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});
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if (dirty_it->second.state == ST_J_SYNCED)
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{
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dirty_it->second.state = ST_J_STABLE;
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// Acknowledge op
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op->retval = 0;
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op->callback(op);
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}
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else if (dirty_it->second.state == ST_D_META_SYNCED)
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{
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dirty_it->second.state = ST_D_STABLE;
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// Acknowledge op
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op->retval = 0;
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op->callback(op);
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}
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else if (dirty_it->second.state == ST_J_STABLE)
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{
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}
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else if (dirty_it->second.state == ST_D_STABLE)
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{
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}
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}
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}
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