Simplified distributed block storage with strong consistency, like in Ceph
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// Copyright (c) Vitaliy Filippov, 2019+
// License: VNPL-1.1 (see README.md for details)
#pragma once
#include "blockstore.h"
#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <time.h>
#include <unistd.h>
#include <linux/fs.h>
#include <vector>
#include <list>
#include <deque>
#include <new>
#include "cpp-btree/btree_map.h"
#include "malloc_or_die.h"
#include "allocator.h"
//#define BLOCKSTORE_DEBUG
// States are not stored on disk. Instead, they're deduced from the journal
#define BS_ST_SMALL_WRITE 0x01
#define BS_ST_BIG_WRITE 0x02
#define BS_ST_DELETE 0x03
#define BS_ST_WAIT_DEL 0x10
#define BS_ST_WAIT_BIG 0x20
#define BS_ST_IN_FLIGHT 0x30
#define BS_ST_SUBMITTED 0x40
#define BS_ST_WRITTEN 0x50
#define BS_ST_SYNCED 0x60
#define BS_ST_STABLE 0x70
#define BS_ST_INSTANT 0x100
#define IMMEDIATE_NONE 0
#define IMMEDIATE_SMALL 1
#define IMMEDIATE_ALL 2
#define BS_ST_TYPE_MASK 0x0F
#define BS_ST_WORKFLOW_MASK 0xF0
#define IS_IN_FLIGHT(st) (((st) & 0xF0) <= BS_ST_SUBMITTED)
#define IS_STABLE(st) (((st) & 0xF0) == BS_ST_STABLE)
#define IS_SYNCED(st) (((st) & 0xF0) >= BS_ST_SYNCED)
#define IS_JOURNAL(st) (((st) & 0x0F) == BS_ST_SMALL_WRITE)
#define IS_BIG_WRITE(st) (((st) & 0x0F) == BS_ST_BIG_WRITE)
#define IS_DELETE(st) (((st) & 0x0F) == BS_ST_DELETE)
#define BS_SUBMIT_GET_SQE(sqe, data) \
BS_SUBMIT_GET_ONLY_SQE(sqe); \
struct ring_data_t *data = ((ring_data_t*)sqe->user_data)
#define BS_SUBMIT_GET_ONLY_SQE(sqe) \
struct io_uring_sqe *sqe = get_sqe();\
if (!sqe)\
{\
/* Pause until there are more requests available */\
PRIV(op)->wait_for = WAIT_SQE;\
return 0;\
}
#define BS_SUBMIT_GET_SQE_DECL(sqe) \
sqe = get_sqe();\
if (!sqe)\
{\
/* Pause until there are more requests available */\
PRIV(op)->wait_for = WAIT_SQE;\
return 0;\
}
#include "blockstore_journal.h"
// "VITAstor"
#define BLOCKSTORE_META_MAGIC 0x726F747341544956l
#define BLOCKSTORE_META_VERSION 1
// metadata header (superblock)
// FIXME: After adding the OSD superblock, add a key to metadata
// and journal headers to check if they belong to the same OSD
struct __attribute__((__packed__)) blockstore_meta_header_t
{
uint64_t zero;
uint64_t magic;
uint64_t version;
uint32_t meta_block_size;
uint32_t data_block_size;
uint32_t bitmap_granularity;
};
// 32 bytes = 24 bytes + block bitmap (4 bytes by default) + external attributes (also bitmap, 4 bytes by default)
// per "clean" entry on disk with fixed metadata tables
// FIXME: maybe add crc32's to metadata
struct __attribute__((__packed__)) clean_disk_entry
{
object_id oid;
uint64_t version;
uint8_t bitmap[];
};
// 32 = 16 + 16 bytes per "clean" entry in memory (object_id => clean_entry)
struct __attribute__((__packed__)) clean_entry
{
uint64_t version;
uint64_t location;
};
// 64 = 24 + 40 bytes per dirty entry in memory (obj_ver_id => dirty_entry)
struct __attribute__((__packed__)) dirty_entry
{
uint32_t state;
uint32_t flags; // unneeded, but present for alignment
uint64_t location; // location in either journal or data -> in BYTES
uint32_t offset; // data offset within object (stripe)
uint32_t len; // data length
uint64_t journal_sector; // journal sector used for this entry
void* bitmap; // either external bitmap itself when it fits, or a pointer to it when it doesn't
};
// - Sync must be submitted after previous writes/deletes (not before!)
// - Reads to the same object must be submitted after previous writes/deletes
// are written (not necessarily synced) in their location. This is because we
// rely on read-modify-write for erasure coding and we must return new data
// to calculate parity for subsequent writes
// - Writes may be submitted in any order, because they don't overlap. Each write
// goes into a new location - either on the journal device or on the data device
// - Stable (stabilize) must be submitted after sync of that object is completed
// It's even OK to return an error to the caller if that object is not synced yet
// - Journal trim may be processed only after all versions are moved to
// the main storage AND after all read operations for older versions complete
// - If an operation can not be submitted because the ring is full
// we should stop submission of other operations. Otherwise some "scatter" reads
// may end up blocked for a long time.
// Otherwise, the submit order is free, that is all operations may be submitted immediately
// In fact, adding a write operation must immediately result in dirty_db being populated
// Suspend operation until there are more free SQEs
#define WAIT_SQE 1
// Suspend operation until there are <wait_detail> bytes of free space in the journal on disk
#define WAIT_JOURNAL 3
// Suspend operation until the next journal sector buffer is free
#define WAIT_JOURNAL_BUFFER 4
// Suspend operation until there is some free space on the data device
#define WAIT_FREE 5
struct fulfill_read_t
{
uint64_t offset, len;
};
#define PRIV(op) ((blockstore_op_private_t*)(op)->private_data)
#define FINISH_OP(op) PRIV(op)->~blockstore_op_private_t(); std::function<void (blockstore_op_t*)>(op->callback)(op)
struct blockstore_op_private_t
{
// Wait status
int wait_for;
uint64_t wait_detail;
int pending_ops;
int op_state;
// Read
std::vector<fulfill_read_t> read_vec;
// Sync, write
uint64_t min_flushed_journal_sector, max_flushed_journal_sector;
// Write
struct iovec iov_zerofill[3];
// Warning: must not have a default value here because it's written to before calling constructor in blockstore_write.cpp O_o
uint64_t real_version;
timespec tv_begin;
// Sync
std::vector<obj_ver_id> sync_big_writes, sync_small_writes;
int sync_small_checked, sync_big_checked;
};
// https://github.com/algorithm-ninja/cpp-btree
// https://github.com/greg7mdp/sparsepp/ was used previously, but it was TERRIBLY slow after resizing
// with sparsepp, random reads dropped to ~700 iops very fast with just as much as ~32k objects in the DB
typedef btree::btree_map<object_id, clean_entry> blockstore_clean_db_t;
typedef std::map<obj_ver_id, dirty_entry> blockstore_dirty_db_t;
#include "blockstore_init.h"
#include "blockstore_flush.h"
class blockstore_impl_t
{
/******* OPTIONS *******/
std::string data_device, meta_device, journal_device;
uint32_t block_size;
uint64_t meta_offset;
uint64_t data_offset;
uint64_t cfg_journal_size, cfg_data_size;
// Required write alignment and journal/metadata/data areas' location alignment
uint32_t disk_alignment = 4096;
// Journal block size - minimum_io_size of the journal device is the best choice
uint64_t journal_block_size = 4096;
// Metadata block size - minimum_io_size of the metadata device is the best choice
uint64_t meta_block_size = 4096;
// Sparse write tracking granularity. 4 KB is a good choice. Must be a multiple of disk_alignment
uint64_t bitmap_granularity = 4096;
bool readonly = false;
// By default, Blockstore locks all opened devices exclusively. This option can be used to disable locking
bool disable_flock = false;
// It is safe to disable fsync() if drive write cache is writethrough
bool disable_data_fsync = false, disable_meta_fsync = false, disable_journal_fsync = false;
// Enable if you want every operation to be executed with an "implicit fsync"
// Suitable only for server SSDs with capacitors, requires disabled data and journal fsyncs
int immediate_commit = IMMEDIATE_NONE;
bool inmemory_meta = false;
// Maximum and minimum flusher count
unsigned max_flusher_count, min_flusher_count;
// Maximum queue depth
unsigned max_write_iodepth = 128;
// Enable small (journaled) write throttling, useful for the SSD+HDD case
bool throttle_small_writes = false;
// Target data device iops, bandwidth and parallelism for throttling (100/100/1 is the default for HDD)
int throttle_target_iops = 100;
int throttle_target_mbs = 100;
int throttle_target_parallelism = 1;
// Minimum difference in microseconds between target and real execution times to throttle the response
int throttle_threshold_us = 50;
/******* END OF OPTIONS *******/
struct ring_consumer_t ring_consumer;
blockstore_clean_db_t clean_db;
uint8_t *clean_bitmap = NULL;
blockstore_dirty_db_t dirty_db;
std::vector<blockstore_op_t*> submit_queue;
std::vector<obj_ver_id> unsynced_big_writes, unsynced_small_writes;
int unsynced_big_write_count = 0;
allocator *data_alloc = NULL;
uint8_t *zero_object;
uint32_t block_order;
uint64_t block_count;
uint32_t clean_entry_bitmap_size = 0, clean_entry_size = 0;
int meta_fd;
int data_fd;
uint64_t meta_size, meta_area, meta_len;
uint64_t data_size, data_len;
void *metadata_buffer = NULL;
struct journal_t journal;
journal_flusher_t *flusher;
int write_iodepth = 0;
bool live = false, queue_stall = false;
ring_loop_t *ringloop;
timerfd_manager_t *tfd;
bool stop_sync_submitted;
inline struct io_uring_sqe* get_sqe()
{
return ringloop->get_sqe();
}
friend class blockstore_init_meta;
friend class blockstore_init_journal;
friend class blockstore_journal_check_t;
friend class journal_flusher_t;
friend class journal_flusher_co;
void parse_config(blockstore_config_t & config);
void calc_lengths();
void open_data();
void open_meta();
void open_journal();
uint8_t* get_clean_entry_bitmap(uint64_t block_loc, int offset);
// Asynchronous init
int initialized;
int metadata_buf_size;
blockstore_init_meta* metadata_init_reader;
blockstore_init_journal* journal_init_reader;
void check_wait(blockstore_op_t *op);
// Read
int dequeue_read(blockstore_op_t *read_op);
int fulfill_read(blockstore_op_t *read_op, uint64_t &fulfilled, uint32_t item_start, uint32_t item_end,
uint32_t item_state, uint64_t item_version, uint64_t item_location);
int fulfill_read_push(blockstore_op_t *op, void *buf, uint64_t offset, uint64_t len,
uint32_t item_state, uint64_t item_version);
void handle_read_event(ring_data_t *data, blockstore_op_t *op);
// Write
bool enqueue_write(blockstore_op_t *op);
void cancel_all_writes(blockstore_op_t *op, blockstore_dirty_db_t::iterator dirty_it, int retval);
int dequeue_write(blockstore_op_t *op);
int dequeue_del(blockstore_op_t *op);
int continue_write(blockstore_op_t *op);
void release_journal_sectors(blockstore_op_t *op);
void handle_write_event(ring_data_t *data, blockstore_op_t *op);
// Sync
int continue_sync(blockstore_op_t *op, bool queue_has_in_progress_sync);
void handle_sync_event(ring_data_t *data, blockstore_op_t *op);
void ack_sync(blockstore_op_t *op);
// Stabilize
int dequeue_stable(blockstore_op_t *op);
int continue_stable(blockstore_op_t *op);
void mark_stable(const obj_ver_id & ov, bool forget_dirty = false);
void handle_stable_event(ring_data_t *data, blockstore_op_t *op);
void stabilize_object(object_id oid, uint64_t max_ver);
// Rollback
int dequeue_rollback(blockstore_op_t *op);
int continue_rollback(blockstore_op_t *op);
void mark_rolled_back(const obj_ver_id & ov);
void handle_rollback_event(ring_data_t *data, blockstore_op_t *op);
void erase_dirty(blockstore_dirty_db_t::iterator dirty_start, blockstore_dirty_db_t::iterator dirty_end, uint64_t clean_loc);
// List
void process_list(blockstore_op_t *op);
public:
blockstore_impl_t(blockstore_config_t & config, ring_loop_t *ringloop, timerfd_manager_t *tfd);
~blockstore_impl_t();
// Event loop
void loop();
// Returns true when blockstore is ready to process operations
// (Although you're free to enqueue them before that)
bool is_started();
// Returns true when it's safe to destroy the instance. If destroying the instance
// requires to purge some queues, starts that process. Should be called in the event
// loop until it returns true.
bool is_safe_to_stop();
// Returns true if stalled
bool is_stalled();
// Submission
void enqueue_op(blockstore_op_t *op);
// Simplified synchronous operation: get object bitmap & current version
int read_bitmap(object_id oid, uint64_t target_version, void *bitmap, uint64_t *result_version = NULL);
// Unstable writes are added here (map of object_id -> version)
std::unordered_map<object_id, uint64_t> unstable_writes;
// Space usage statistics
std::map<uint64_t, uint64_t> inode_space_stats;
inline uint32_t get_block_size() { return block_size; }
inline uint64_t get_block_count() { return block_count; }
inline uint64_t get_free_block_count() { return data_alloc->get_free_count(); }
inline uint32_t get_bitmap_granularity() { return disk_alignment; }
};