Simplified distributed block storage with strong consistency, like in Ceph
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// Copyright (c) Vitaliy Filippov, 2019+
// License: VNPL-1.0 or GNU GPL-2.0+ (see README.md for details)
// Similar to qemu-nbd, but sets timeout and uses io_uring
#include <linux/nbd.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <arpa/inet.h>
#include <sys/un.h>
#include <unistd.h>
#include <fcntl.h>
#include <signal.h>
#include "epoll_manager.h"
#include "cluster_client.h"
class nbd_proxy
{
protected:
uint64_t inode = 0;
ring_loop_t *ringloop = NULL;
epoll_manager_t *epmgr = NULL;
cluster_client_t *cli = NULL;
ring_consumer_t consumer;
std::vector<iovec> send_list, next_send_list;
std::vector<void*> to_free;
int nbd_fd = -1;
void *recv_buf = NULL;
int receive_buffer_size = 9000;
nbd_request cur_req;
cluster_op_t *cur_op = NULL;
void *cur_buf = NULL;
int cur_left = 0;
int read_state = 0;
int read_ready = 0;
msghdr read_msg = { 0 }, send_msg = { 0 };
iovec read_iov = { 0 };
public:
int start(json11::Json cfg)
{
// Parse options
if (cfg["etcd_address"].string_value() == "")
{
fprintf(stderr, "etcd_address is missing\n");
exit(1);
}
if (!cfg["size"].uint64_value())
{
fprintf(stderr, "device size is missing\n");
exit(1);
}
inode = cfg["inode"].uint64_value();
uint64_t pool = cfg["pool"].uint64_value();
if (pool)
{
inode = (inode & ((1l << (64-POOL_ID_BITS)) - 1)) | (pool << (64-POOL_ID_BITS));
}
if (!(inode >> (64-POOL_ID_BITS)))
{
fprintf(stderr, "pool is missing\n");
exit(1);
}
// Initialize NBD
int sockfd[2];
if (socketpair(AF_UNIX, SOCK_STREAM, 0, sockfd) < 0)
{
perror("socketpair");
exit(1);
}
fcntl(sockfd[0], F_SETFL, fcntl(sockfd[0], F_GETFL, 0) | O_NONBLOCK);
nbd_fd = sockfd[0];
if (run_nbd(sockfd, cfg["dev_num"].int64_value(), cfg["size"].uint64_value(), NBD_FLAG_SEND_FLUSH, 30) < 0)
{
perror("run_nbd");
exit(1);
}
// Create client
ringloop = new ring_loop_t(512);
epmgr = new epoll_manager_t(ringloop);
cli = new cluster_client_t(ringloop, epmgr->tfd, cfg);
// Initialize read state
read_state = CL_READ_HDR;
recv_buf = malloc_or_die(receive_buffer_size);
cur_buf = &cur_req;
cur_left = sizeof(nbd_request);
consumer.loop = [this]()
{
submit_read();
submit_send();
ringloop->submit();
};
ringloop->register_consumer(&consumer);
// Add FD to epoll
epmgr->tfd->set_fd_handler(sockfd[0], false, [this](int peer_fd, int epoll_events)
{
read_ready++;
submit_read();
});
while (1)
{
ringloop->loop();
ringloop->wait();
}
}
protected:
int run_nbd(int sockfd[2], int dev_num, uint64_t size, uint64_t flags, unsigned timeout)
{
// Check handle size
assert(sizeof(cur_req.handle) == 8);
char path[64] = { 0 };
sprintf(path, "/dev/nbd%d", dev_num);
int r, nbd = open(path, O_RDWR), qd_fd;
if (nbd < 0)
{
return -1;
}
r = ioctl(nbd, NBD_CLEAR_SOCK);
if (r < 0)
{
goto end_close;
}
r = ioctl(nbd, NBD_SET_SOCK, sockfd[1]);
if (r < 0)
{
goto end_close;
}
r = ioctl(nbd, NBD_SET_BLKSIZE, 4096);
if (r < 0)
{
goto end_close;
}
r = ioctl(nbd, NBD_SET_SIZE, size);
if (r < 0)
{
goto end_close;
}
ioctl(nbd, NBD_SET_FLAGS, flags);
if (timeout >= 0)
{
r = ioctl(nbd, NBD_SET_TIMEOUT, (unsigned long)timeout);
if (r < 0)
{
goto end_close;
}
}
// Configure request size
sprintf(path, "/sys/block/nbd%d/queue/max_sectors_kb", dev_num);
qd_fd = open(path, O_WRONLY);
if (qd_fd < 0)
{
goto end_close;
}
write(qd_fd, "32768", 5);
close(qd_fd);
if (!fork())
{
// Run in child
close(sockfd[0]);
r = ioctl(nbd, NBD_DO_IT);
if (r < 0)
{
fprintf(stderr, "NBD device terminated with error: %s\n", strerror(errno));
kill(getppid(), SIGTERM);
}
close(sockfd[1]);
ioctl(nbd, NBD_CLEAR_QUE);
ioctl(nbd, NBD_CLEAR_SOCK);
exit(0);
}
close(sockfd[1]);
close(nbd);
return 0;
end_close:
int err = errno;
ioctl(nbd, NBD_CLEAR_SOCK);
close(nbd);
errno = err;
return -1;
}
void submit_send()
{
if (!send_list.size() || send_msg.msg_iovlen > 0)
{
return;
}
io_uring_sqe* sqe = ringloop->get_sqe();
if (!sqe)
{
return;
}
ring_data_t* data = ((ring_data_t*)sqe->user_data);
data->callback = [this](ring_data_t *data) { handle_send(data->res); };
send_msg.msg_iov = send_list.data();
send_msg.msg_iovlen = send_list.size();
my_uring_prep_sendmsg(sqe, nbd_fd, &send_msg, MSG_ZEROCOPY);
}
void handle_send(int result)
{
send_msg.msg_iovlen = 0;
if (result < 0 && result != -EAGAIN)
{
fprintf(stderr, "Socket disconnected: %s\n", strerror(-result));
exit(1);
}
int to_eat = 0;
while (result > 0 && to_eat < send_list.size())
{
if (result >= send_list[to_eat].iov_len)
{
free(to_free[to_eat]);
result -= send_list[to_eat].iov_len;
to_eat++;
}
else
{
send_list[to_eat].iov_base += result;
send_list[to_eat].iov_len -= result;
break;
}
}
if (to_eat > 0)
{
send_list.erase(send_list.begin(), send_list.begin() + to_eat);
to_free.erase(to_free.begin(), to_free.begin() + to_eat);
}
for (int i = 0; i < next_send_list.size(); i++)
{
send_list.push_back(next_send_list[i]);
}
next_send_list.clear();
if (send_list.size() > 0)
{
ringloop->wakeup();
}
}
void submit_read()
{
if (!read_ready || read_msg.msg_iovlen > 0)
{
return;
}
io_uring_sqe* sqe = ringloop->get_sqe();
if (!sqe)
{
return;
}
ring_data_t* data = ((ring_data_t*)sqe->user_data);
data->callback = [this](ring_data_t *data) { handle_read(data->res); };
if (cur_left < receive_buffer_size)
{
read_iov.iov_base = recv_buf;
read_iov.iov_len = receive_buffer_size;
}
else
{
read_iov.iov_base = cur_buf;
read_iov.iov_len = cur_left;
}
read_msg.msg_iov = &read_iov;
read_msg.msg_iovlen = 1;
my_uring_prep_recvmsg(sqe, nbd_fd, &read_msg, 0);
}
void handle_read(int result)
{
read_msg.msg_iovlen = 0;
if (result < 0 && result != -EAGAIN)
{
fprintf(stderr, "Socket disconnected: %s\n", strerror(-result));
exit(1);
}
if (result == -EAGAIN || result < read_iov.iov_len)
{
read_ready--;
}
if (read_ready > 0)
{
ringloop->wakeup();
}
void *b = recv_buf;
while (result > 0)
{
if (read_iov.iov_base == recv_buf)
{
int inc = result >= cur_left ? cur_left : result;
memcpy(cur_buf, b, inc);
cur_left -= inc;
result -= inc;
cur_buf += inc;
b += inc;
}
else
{
assert(result <= cur_left);
cur_left -= result;
result = 0;
}
if (cur_left <= 0)
{
handle_finished_read();
}
}
}
void handle_finished_read()
{
if (read_state == CL_READ_HDR)
{
int req_type = be32toh(cur_req.type);
if (be32toh(cur_req.magic) != NBD_REQUEST_MAGIC ||
req_type != NBD_CMD_READ && req_type != NBD_CMD_WRITE && req_type != NBD_CMD_FLUSH)
{
printf("Unexpected request: magic=%x type=%x, terminating\n", cur_req.magic, req_type);
exit(1);
}
uint64_t handle = *((uint64_t*)cur_req.handle);
#ifdef DEBUG
printf("request %lx +%x %lx\n", be64toh(cur_req.from), be32toh(cur_req.len), handle);
#endif
void *buf = NULL;
cluster_op_t *op = new cluster_op_t;
if (req_type == NBD_CMD_READ || req_type == NBD_CMD_WRITE)
{
op->opcode = req_type == NBD_CMD_READ ? OSD_OP_READ : OSD_OP_WRITE;
op->inode = inode;
op->offset = be64toh(cur_req.from);
op->len = be32toh(cur_req.len);
buf = malloc_or_die(sizeof(nbd_reply) + op->len);
op->iov.push_back(buf + sizeof(nbd_reply), op->len);
}
else if (req_type == NBD_CMD_FLUSH)
{
op->opcode = OSD_OP_SYNC;
buf = malloc_or_die(sizeof(nbd_reply));
}
op->callback = [this, buf, handle](cluster_op_t *op)
{
#ifdef DEBUG
printf("reply %lx e=%d\n", handle, op->retval);
#endif
nbd_reply *reply = (nbd_reply*)buf;
reply->magic = htobe32(NBD_REPLY_MAGIC);
memcpy(reply->handle, &handle, 8);
reply->error = htobe32(op->retval < 0 ? -op->retval : 0);
auto & to_list = send_msg.msg_iovlen > 0 ? next_send_list : send_list;
if (op->retval < 0 || op->opcode != OSD_OP_READ)
to_list.push_back({ .iov_base = buf, .iov_len = sizeof(nbd_reply) });
else
to_list.push_back({ .iov_base = buf, .iov_len = sizeof(nbd_reply) + op->len });
to_free.push_back(buf);
delete op;
ringloop->wakeup();
};
if (req_type == NBD_CMD_WRITE)
{
cur_op = op;
cur_buf = buf + sizeof(nbd_reply);
cur_left = op->len;
read_state = CL_READ_DATA;
}
else
{
cur_op = NULL;
cur_buf = &cur_req;
cur_left = sizeof(nbd_request);
read_state = CL_READ_HDR;
cli->execute(op);
}
}
else
{
cli->execute(cur_op);
cur_op = NULL;
cur_buf = &cur_req;
cur_left = sizeof(nbd_request);
read_state = CL_READ_HDR;
}
}
};
int main(int narg, char *args[])
{
setvbuf(stdout, NULL, _IONBF, 0);
setvbuf(stderr, NULL, _IONBF, 0);
json11::Json::object cfg;
for (int i = 1; i < narg; i++)
{
if (args[i][0] == '-' && args[i][1] == '-' && i < narg-1)
{
char *opt = args[i]+2;
cfg[opt] = args[++i];
}
}
nbd_proxy *p = new nbd_proxy();
p->start(cfg);
return 0;
}