Simplified distributed block storage with strong consistency, like in Ceph
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// Copyright (c) Vitaliy Filippov, 2019+
// License: VNPL-1.0 (see for details)
#pragma once
#include <stdint.h>
#include <string>
#include <map>
#include <unordered_map>
#include <functional>
#include "object_id.h"
#include "ringloop.h"
// Memory alignment for direct I/O (usually 512 bytes)
// All other alignments must be a multiple of this one
#define MEM_ALIGNMENT 512
// Default block size is 128 KB, current allowed range is 4K - 128M
#define DEFAULT_ORDER 17
#define MIN_BLOCK_SIZE 4*1024
#define MAX_BLOCK_SIZE 128*1024*1024
#define BS_OP_MIN 1
#define BS_OP_READ 1
#define BS_OP_WRITE 2
#define BS_OP_SYNC 4
#define BS_OP_STABLE 5
#define BS_OP_DELETE 6
#define BS_OP_LIST 7
#define BS_OP_ROLLBACK 8
#define BS_OP_MAX 9
Blockstore opcode documentation:
Read or write object data. WRITE_STABLE writes a version that doesn't require marking as stable.
- oid = requested object
- version = requested version.
For reads:
- version == 0: read the last stable version,
- version == UINT64_MAX: read the last version,
- otherwise: read the newest version that is <= the specified version
- reads aren't guaranteed to return data from previous unfinished writes
For writes:
- if version == 0, a new version is assigned automatically
- if version != 0, it is assigned for the new write if possible, otherwise -EINVAL is returned
- offset, len = offset and length within object. length may be zero, in that case
read operation only returns the version / write operation only bumps the version
- buf = pre-allocated buffer for data (read) / with data (write). may be NULL if len == 0.
- retval = number of bytes actually read/written or negative error number (-EINVAL or -ENOSPC)
- version = the version actually read or written
Delete an object.
- oid = requested object
- version = requested version. Treated the same as with BS_OP_WRITE
- retval = 0 or negative error number (-EINVAL)
- version = the version actually written (delete is initially written as an object version)
Make sure all previously issued modifications reach physical media.
Input: Nothing except opcode
- retval = 0 or negative error number (-EINVAL)
Mark objects as stable / rollback previous unstable writes.
- len = count of obj_ver_id's to stabilize or rollback
- stabilize: all object versions up to the requested version of each object are marked as stable
- rollback: all objects are rolled back to the requested stable versions
- buf = pre-allocated obj_ver_id array <len> units long
- retval = 0 or negative error number (-EINVAL, -ENOENT if no such version or -EBUSY if not synced)
ONLY FOR TESTS! Sync and mark all unstable object versions as stable, at once.
Input: Nothing except opcode
- retval = 0 or negative error number (-EINVAL)
Get a list of all objects in this Blockstore.
- oid.stripe = PG alignment
- len = PG count or 0 to list all objects
- offset = PG number
- oid.inode = min inode number or 0 to list all inodes
- version = max inode number or 0 to list all inodes
- retval = total obj_ver_id count
- version = stable obj_ver_id count
- buf = obj_ver_id array allocated by the blockstore. Stable versions come first.
You must free it yourself after usage with free().
Output includes all objects for which (((inode + stripe / <PG alignment>) % <PG count>) == <PG number>).
struct blockstore_op_t
// operation
uint64_t opcode;
// finish callback
std::function<void (blockstore_op_t*)> callback;
object_id oid;
uint64_t version;
uint32_t offset;
uint32_t len;
void *buf;
int retval;
uint8_t private_data[BS_OP_PRIVATE_DATA_SIZE];
typedef std::unordered_map<std::string, std::string> blockstore_config_t;
class blockstore_impl_t;
class blockstore_t
blockstore_impl_t *impl;
blockstore_t(blockstore_config_t & config, ring_loop_t *ringloop);
// 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 blockstore is stalled
bool is_stalled();
// 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();
// Submission
void enqueue_op(blockstore_op_t *op);
// Insert operation into the beginning of the queue
// Intended for the OSD syncer "thread" to be able to stabilize something when the journal is full
void enqueue_op_first(blockstore_op_t *op);
// Unstable writes are added here (map of object_id -> version)
std::unordered_map<object_id, uint64_t> & get_unstable_writes();
// FIXME rename to object_size
uint32_t get_block_size();
uint64_t get_block_count();
uint64_t get_free_block_count();
uint32_t get_disk_alignment();