Simplified distributed block storage with strong consistency, like in Ceph
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// Copyright (c) Vitaliy Filippov, 2019+
// License: VNPL-1.0 (see README.md for details)
#pragma once
#include "crc32c.h"
#define MIN_JOURNAL_SIZE 4*1024*1024
#define JOURNAL_MAGIC 0x4A33
#define JOURNAL_BUFFER_SIZE 4*1024*1024
// We reserve some extra space for future stabilize requests during writes
#define JOURNAL_STABILIZE_RESERVATION 65536
// Journal entries
// Journal entries are linked to each other by their crc32 value
// The journal is almost a blockchain, because object versions constantly increase
#define JE_MIN 0x01
#define JE_START 0x01
#define JE_SMALL_WRITE 0x02
#define JE_BIG_WRITE 0x03
#define JE_STABLE 0x04
#define JE_DELETE 0x05
#define JE_ROLLBACK 0x06
#define JE_SMALL_WRITE_INSTANT 0x07
#define JE_BIG_WRITE_INSTANT 0x08
#define JE_MAX 0x08
// crc32c comes first to ease calculation and is equal to crc32()
struct __attribute__((__packed__)) journal_entry_start
{
uint32_t crc32;
uint16_t magic;
uint16_t type;
uint32_t size;
uint32_t reserved;
uint64_t journal_start;
};
struct __attribute__((__packed__)) journal_entry_small_write
{
uint32_t crc32;
uint16_t magic;
uint16_t type;
uint32_t size;
uint32_t crc32_prev;
object_id oid;
uint64_t version;
uint32_t offset;
uint32_t len;
// small_write entries contain <len> bytes of data which is stored in next sectors
// data_offset is its offset within journal
uint64_t data_offset;
uint32_t crc32_data;
};
struct __attribute__((__packed__)) journal_entry_big_write
{
uint32_t crc32;
uint16_t magic;
uint16_t type;
uint32_t size;
uint32_t crc32_prev;
object_id oid;
uint64_t version;
uint32_t offset;
uint32_t len;
uint64_t location;
};
struct __attribute__((__packed__)) journal_entry_stable
{
uint32_t crc32;
uint16_t magic;
uint16_t type;
uint32_t size;
uint32_t crc32_prev;
object_id oid;
uint64_t version;
};
struct __attribute__((__packed__)) journal_entry_rollback
{
uint32_t crc32;
uint16_t magic;
uint16_t type;
uint32_t size;
uint32_t crc32_prev;
object_id oid;
uint64_t version;
};
struct __attribute__((__packed__)) journal_entry_del
{
uint32_t crc32;
uint16_t magic;
uint16_t type;
uint32_t size;
uint32_t crc32_prev;
object_id oid;
uint64_t version;
};
struct __attribute__((__packed__)) journal_entry
{
union
{
struct __attribute__((__packed__))
{
uint32_t crc32;
uint16_t magic;
uint16_t type;
uint32_t size;
uint32_t crc32_prev;
};
journal_entry_start start;
journal_entry_small_write small_write;
journal_entry_big_write big_write;
journal_entry_stable stable;
journal_entry_rollback rollback;
journal_entry_del del;
};
};
inline uint32_t je_crc32(journal_entry *je)
{
// 0x48674bc7 = crc32(4 zero bytes)
return crc32c(0x48674bc7, ((uint8_t*)je)+4, je->size-4);
}
struct journal_sector_info_t
{
uint64_t offset;
uint64_t usage_count;
bool written;
bool dirty;
};
struct journal_t
{
int fd;
uint64_t device_size;
bool inmemory = false;
void *buffer = NULL;
uint64_t block_size;
uint64_t offset, len;
// Next free block offset
uint64_t next_free = 0;
// First occupied block offset
uint64_t used_start = 0;
// End of the last block not used for writing anymore
uint64_t dirty_start = 0;
uint32_t crc32_last = 0;
// Current sector(s) used for writing
void *sector_buf = NULL;
journal_sector_info_t *sector_info = NULL;
uint64_t sector_count;
bool no_same_sector_overwrites = false;
int cur_sector = 0;
int in_sector_pos = 0;
// Used sector map
// May use ~ 80 MB per 1 GB of used journal space in the worst case
std::map<uint64_t, uint64_t> used_sectors;
~journal_t();
bool trim();
};
struct blockstore_journal_check_t
{
blockstore_impl_t *bs;
uint64_t next_pos, next_sector, next_in_pos;
int sectors_required, first_sector;
bool right_dir; // writing to the end or the beginning of the ring buffer
blockstore_journal_check_t(blockstore_impl_t *bs);
int check_available(blockstore_op_t *op, int required, int size, int data_after);
};
journal_entry* prefill_single_journal_entry(journal_t & journal, uint16_t type, uint32_t size);
void prepare_journal_sector_write(journal_t & journal, int sector, io_uring_sqe *sqe, std::function<void(ring_data_t*)> cb);