317 lines
11 KiB
C++
317 lines
11 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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// AND We must know what we stabilize. Basic workflow is like:
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// 1) primary OSD receives sync request
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// 2) it determines his own unsynced writes from blockstore's information
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// just before submitting fsync
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// 3) it submits syncs to blockstore and peers
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// 4) after everyone acks sync it takes the object list and sends stabilize requests to everyone
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int blockstore::dequeue_stable(blockstore_operation *op)
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{
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obj_ver_id* v;
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int i, todo = 0;
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for (i = 0, v = (obj_ver_id*)op->buf; i < op->len; i++, v++)
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{
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auto dirty_it = dirty_db.find(*v);
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if (dirty_it == dirty_db.end())
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{
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auto clean_it = clean_db.find(v->oid);
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if (clean_it == clean_db.end() || clean_it->second.version < v->version)
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{
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// No such object version
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op->retval = EINVAL;
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op->callback(op);
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return 1;
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}
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else
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{
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// Already stable
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}
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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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todo++;
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}
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}
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if (!todo)
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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, todo, 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 SQEs
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struct io_uring_sqe *sqe[space_check.sectors_required];
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for (i = 0; i < space_check.sectors_required; i++)
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{
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BS_SUBMIT_GET_SQE_DECL(sqe[i]);
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}
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// Prepare and submit journal entries
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int s = 0, cur_sector = -1;
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for (i = 0, v = (obj_ver_id*)op->buf; i < op->len; i++, v++)
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{
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journal_entry_stable *je = (journal_entry_stable*)
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prefill_single_journal_entry(journal, JE_STABLE, sizeof(journal_entry_stable));
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je->oid = v->oid;
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je->version = v->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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if (cur_sector != journal.cur_sector)
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{
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if (cur_sector == -1)
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op->min_used_journal_sector = 1 + journal.cur_sector;
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cur_sector = journal.cur_sector;
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prepare_journal_sector_write(op, journal, sqe[s++]);
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}
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}
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op->max_used_journal_sector = 1 + journal.cur_sector;
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op->pending_ops = s;
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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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// First step: mark dirty_db entries as stable, acknowledge op completion
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obj_ver_id* v;
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int i;
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for (i = 0, v = (obj_ver_id*)op->buf; i < op->len; i++, v++)
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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(*v);
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if (dirty_it != dirty_db.end())
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{
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do
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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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}
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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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}
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else if (IS_STABLE(dirty_it->second.state))
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{
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break;
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}
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dirty_it--;
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} while (dirty_it != dirty_db.begin() && dirty_it->first.oid == v->oid);
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flusher.flush_queue.push_back(*v);
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}
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}
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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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}
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struct copy_buffer_t
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{
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uint64_t offset, len;
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void *buf;
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};
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class journal_flusher_t
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{
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blockstore *bs;
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int wait_state, wait_count;
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struct io_uring_sqe *sqe;
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struct ring_data_t *data;
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bool skip_copy;
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obj_ver_id cur;
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std::map<obj_ver_id, dirty_entry>::iterator dirty_it;
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std::vector<copy_buffer_t> v;
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std::vector<copy_buffer_t>::iterator it;
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uint64_t offset, len, submit_len, clean_loc;
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public:
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journal_flusher_t(int flush_count);
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std::deque<obj_ver_id> flush_queue;
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void loop();
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};
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journal_flusher_t::journal_flusher_t(int flusher_count)
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{
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}
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void journal_flusher_t::loop()
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{
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// This is much better than implementing the whole function as an FSM
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// Maybe I should consider a coroutine library like https://github.com/hnes/libaco ...
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if (wait_state == 1)
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goto resume_1;
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else if (wait_state == 3)
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goto resume_3;
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else if (wait_state == 4)
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goto resume_4;
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else if (wait_state == 5)
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goto resume_5;
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if (!flush_queue.size())
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return;
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cur = flush_queue.front();
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flush_queue.pop_front();
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dirty_it = bs->dirty_db.find(cur);
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if (dirty_it != bs->dirty_db.end())
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{
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v.clear();
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wait_count = 0;
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clean_loc = UINT64_MAX;
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skip_copy = false;
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do
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{
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if (dirty_it->second.state == ST_J_STABLE)
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{
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// First we submit all reads
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offset = dirty_it->second.offset;
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len = dirty_it->second.size;
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it = v.begin();
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while (1)
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{
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for (; it != v.end(); it++)
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if (it->offset >= offset)
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break;
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if (it == v.end() || it->offset > offset)
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{
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submit_len = it->offset >= offset+len ? len : it->offset-offset;
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resume_1:
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sqe = bs->get_sqe();
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if (!sqe)
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{
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// Can't submit read, ring is full
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wait_state = 1;
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return;
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}
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v.insert(it, (copy_buffer_t){ .offset = offset, .len = submit_len, .buf = memalign(512, submit_len) });
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data = ((ring_data_t*)sqe->user_data);
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data->iov = (struct iovec){ v.end()->buf, (size_t)submit_len };
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data->op = this;
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io_uring_prep_readv(
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sqe, bs->journal.fd, &data->iov, 1, bs->journal.offset + dirty_it->second.location + offset
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);
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wait_count++;
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}
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if (it == v.end() || it->offset+it->len >= offset+len)
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{
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break;
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}
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}
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// So subsequent stabilizers don't flush the entry again
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dirty_it->second.state = ST_J_MOVE_READ_SUBMITTED;
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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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// Copy last STABLE entry metadata
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if (!skip_copy)
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{
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clean_loc = dirty_it->second.location;
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}
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skip_copy = true;
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}
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else if (IS_STABLE(dirty_it->second.state))
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{
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break;
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}
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dirty_it--;
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} while (dirty_it != bs->dirty_db.begin() && dirty_it->first.oid == cur.oid);
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if (clean_loc == UINT64_MAX)
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{
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// Find it in clean_db
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auto clean_it = bs->clean_db.find(cur.oid);
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if (clean_it == bs->clean_db.end())
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{
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// Object not present at all. This is a bug.
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throw new std::runtime_error("BUG: Object we are trying to flush not allocated on the data device");
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}
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else
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clean_loc = clean_it->second.location;
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}
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wait_state = 3;
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resume_3:
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// After reads complete we submit writes
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if (wait_count == 0)
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{
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for (it = v.begin(); it != v.end(); it++)
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{
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resume_4:
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sqe = bs->get_sqe();
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if (!sqe)
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{
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// Can't submit a write, ring is full
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wait_state = 4;
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return;
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}
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data = ((ring_data_t*)sqe->user_data);
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data->iov = (struct iovec){ it->buf, (size_t)it->len };
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data->op = this;
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io_uring_prep_writev(
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sqe, bs->data_fd, &data->iov, 1, bs->data_offset + clean_loc + it->offset
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);
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wait_count++;
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}
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wait_state = 5;
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resume_5:
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// Done, free all buffers
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if (wait_count == 0)
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{
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for (it = v.begin(); it != v.end(); it++)
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{
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free(it->buf);
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}
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v.clear();
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wait_state = 0;
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}
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}
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}
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}
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