/* * QEMU Block driver for NBD * * Copyright (C) 2008 Bull S.A.S. * Author: Laurent Vivier <Laurent.Vivier@bull.net> * * Some parts: * Copyright (C) 2007 Anthony Liguori <anthony@codemonkey.ws> * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. */ #include "qemu-common.h" #include "nbd.h" #include "block_int.h" #include "module.h" #include "qemu_socket.h" #include <sys/types.h> #include <unistd.h> #define EN_OPTSTR ":exportname=" /* #define DEBUG_NBD */ #if defined(DEBUG_NBD) #define logout(fmt, ...) \ fprintf(stderr, "nbd\t%-24s" fmt, __func__, ##__VA_ARGS__) #else #define logout(fmt, ...) ((void)0) #endif #define MAX_NBD_REQUESTS 16 #define HANDLE_TO_INDEX(bs, handle) ((handle) ^ ((uint64_t)(intptr_t)bs)) #define INDEX_TO_HANDLE(bs, index) ((index) ^ ((uint64_t)(intptr_t)bs)) typedef struct BDRVNBDState { int sock; uint32_t nbdflags; off_t size; size_t blocksize; char *export_name; /* An NBD server may export several devices */ CoMutex send_mutex; CoMutex free_sema; Coroutine *send_coroutine; int in_flight; Coroutine *recv_coroutine[MAX_NBD_REQUESTS]; struct nbd_reply reply; /* If it begins with '/', this is a UNIX domain socket. Otherwise, * it's a string of the form <hostname|ip4|\[ip6\]>:port */ char *host_spec; } BDRVNBDState; static int nbd_config(BDRVNBDState *s, const char *filename, int flags) { char *file; char *export_name; const char *host_spec; const char *unixpath; int err = -EINVAL; file = g_strdup(filename); export_name = strstr(file, EN_OPTSTR); if (export_name) { if (export_name[strlen(EN_OPTSTR)] == 0) { goto out; } export_name[0] = 0; /* truncate 'file' */ export_name += strlen(EN_OPTSTR); s->export_name = g_strdup(export_name); } /* extract the host_spec - fail if it's not nbd:... */ if (!strstart(file, "nbd:", &host_spec)) { goto out; } /* are we a UNIX or TCP socket? */ if (strstart(host_spec, "unix:", &unixpath)) { if (unixpath[0] != '/') { /* We demand an absolute path*/ goto out; } s->host_spec = g_strdup(unixpath); } else { s->host_spec = g_strdup(host_spec); } err = 0; out: g_free(file); if (err != 0) { g_free(s->export_name); g_free(s->host_spec); } return err; } static void nbd_coroutine_start(BDRVNBDState *s, struct nbd_request *request) { int i; /* Poor man semaphore. The free_sema is locked when no other request * can be accepted, and unlocked after receiving one reply. */ if (s->in_flight >= MAX_NBD_REQUESTS - 1) { qemu_co_mutex_lock(&s->free_sema); assert(s->in_flight < MAX_NBD_REQUESTS); } s->in_flight++; for (i = 0; i < MAX_NBD_REQUESTS; i++) { if (s->recv_coroutine[i] == NULL) { s->recv_coroutine[i] = qemu_coroutine_self(); break; } } assert(i < MAX_NBD_REQUESTS); request->handle = INDEX_TO_HANDLE(s, i); } static int nbd_have_request(void *opaque) { BDRVNBDState *s = opaque; return s->in_flight > 0; } static void nbd_reply_ready(void *opaque) { BDRVNBDState *s = opaque; uint64_t i; int ret; if (s->reply.handle == 0) { /* No reply already in flight. Fetch a header. It is possible * that another thread has done the same thing in parallel, so * the socket is not readable anymore. */ ret = nbd_receive_reply(s->sock, &s->reply); if (ret == -EAGAIN) { return; } if (ret < 0) { s->reply.handle = 0; goto fail; } } /* There's no need for a mutex on the receive side, because the * handler acts as a synchronization point and ensures that only * one coroutine is called until the reply finishes. */ i = HANDLE_TO_INDEX(s, s->reply.handle); if (i >= MAX_NBD_REQUESTS) { goto fail; } if (s->recv_coroutine[i]) { qemu_coroutine_enter(s->recv_coroutine[i], NULL); return; } fail: for (i = 0; i < MAX_NBD_REQUESTS; i++) { if (s->recv_coroutine[i]) { qemu_coroutine_enter(s->recv_coroutine[i], NULL); } } } static void nbd_restart_write(void *opaque) { BDRVNBDState *s = opaque; qemu_coroutine_enter(s->send_coroutine, NULL); } static int nbd_co_send_request(BDRVNBDState *s, struct nbd_request *request, QEMUIOVector *qiov, int offset) { int rc, ret; qemu_co_mutex_lock(&s->send_mutex); s->send_coroutine = qemu_coroutine_self(); qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, nbd_restart_write, nbd_have_request, s); rc = nbd_send_request(s->sock, request); if (rc >= 0 && qiov) { ret = qemu_co_sendv(s->sock, qiov->iov, qiov->niov, offset, request->len); if (ret != request->len) { return -EIO; } } qemu_aio_set_fd_handler(s->sock, nbd_reply_ready, NULL, nbd_have_request, s); s->send_coroutine = NULL; qemu_co_mutex_unlock(&s->send_mutex); return rc; } static void nbd_co_receive_reply(BDRVNBDState *s, struct nbd_request *request, struct nbd_reply *reply, QEMUIOVector *qiov, int offset) { int ret; /* Wait until we're woken up by the read handler. TODO: perhaps * peek at the next reply and avoid yielding if it's ours? */ qemu_coroutine_yield(); *reply = s->reply; if (reply->handle != request->handle) { reply->error = EIO; } else { if (qiov && reply->error == 0) { ret = qemu_co_recvv(s->sock, qiov->iov, qiov->niov, offset, request->len); if (ret != request->len) { reply->error = EIO; } } /* Tell the read handler to read another header. */ s->reply.handle = 0; } } static void nbd_coroutine_end(BDRVNBDState *s, struct nbd_request *request) { int i = HANDLE_TO_INDEX(s, request->handle); s->recv_coroutine[i] = NULL; if (s->in_flight-- == MAX_NBD_REQUESTS) { qemu_co_mutex_unlock(&s->free_sema); } } static int nbd_establish_connection(BlockDriverState *bs) { BDRVNBDState *s = bs->opaque; int sock; int ret; off_t size; size_t blocksize; if (s->host_spec[0] == '/') { sock = unix_socket_outgoing(s->host_spec); } else { sock = tcp_socket_outgoing_spec(s->host_spec); } /* Failed to establish connection */ if (sock < 0) { logout("Failed to establish connection to NBD server\n"); return -errno; } /* NBD handshake */ ret = nbd_receive_negotiate(sock, s->export_name, &s->nbdflags, &size, &blocksize); if (ret < 0) { logout("Failed to negotiate with the NBD server\n"); closesocket(sock); return ret; } /* Now that we're connected, set the socket to be non-blocking and * kick the reply mechanism. */ socket_set_nonblock(sock); qemu_aio_set_fd_handler(sock, nbd_reply_ready, NULL, nbd_have_request, s); s->sock = sock; s->size = size; s->blocksize = blocksize; logout("Established connection with NBD server\n"); return 0; } static void nbd_teardown_connection(BlockDriverState *bs) { BDRVNBDState *s = bs->opaque; struct nbd_request request; request.type = NBD_CMD_DISC; request.from = 0; request.len = 0; nbd_send_request(s->sock, &request); qemu_aio_set_fd_handler(s->sock, NULL, NULL, NULL, NULL); closesocket(s->sock); } static int nbd_open(BlockDriverState *bs, const char* filename, int flags) { BDRVNBDState *s = bs->opaque; int result; qemu_co_mutex_init(&s->send_mutex); qemu_co_mutex_init(&s->free_sema); /* Pop the config into our state object. Exit if invalid. */ result = nbd_config(s, filename, flags); if (result != 0) { return result; } /* establish TCP connection, return error if it fails * TODO: Configurable retry-until-timeout behaviour. */ result = nbd_establish_connection(bs); return result; } static int nbd_co_readv_1(BlockDriverState *bs, int64_t sector_num, int nb_sectors, QEMUIOVector *qiov, int offset) { BDRVNBDState *s = bs->opaque; struct nbd_request request; struct nbd_reply reply; ssize_t ret; request.type = NBD_CMD_READ; request.from = sector_num * 512; request.len = nb_sectors * 512; nbd_coroutine_start(s, &request); ret = nbd_co_send_request(s, &request, NULL, 0); if (ret < 0) { reply.error = -ret; } else { nbd_co_receive_reply(s, &request, &reply, qiov, offset); } nbd_coroutine_end(s, &request); return -reply.error; } static int nbd_co_writev_1(BlockDriverState *bs, int64_t sector_num, int nb_sectors, QEMUIOVector *qiov, int offset) { BDRVNBDState *s = bs->opaque; struct nbd_request request; struct nbd_reply reply; ssize_t ret; request.type = NBD_CMD_WRITE; if (!bdrv_enable_write_cache(bs) && (s->nbdflags & NBD_FLAG_SEND_FUA)) { request.type |= NBD_CMD_FLAG_FUA; } request.from = sector_num * 512; request.len = nb_sectors * 512; nbd_coroutine_start(s, &request); ret = nbd_co_send_request(s, &request, qiov, offset); if (ret < 0) { reply.error = -ret; } else { nbd_co_receive_reply(s, &request, &reply, NULL, 0); } nbd_coroutine_end(s, &request); return -reply.error; } /* qemu-nbd has a limit of slightly less than 1M per request. Try to * remain aligned to 4K. */ #define NBD_MAX_SECTORS 2040 static int nbd_co_readv(BlockDriverState *bs, int64_t sector_num, int nb_sectors, QEMUIOVector *qiov) { int offset = 0; int ret; while (nb_sectors > NBD_MAX_SECTORS) { ret = nbd_co_readv_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset); if (ret < 0) { return ret; } offset += NBD_MAX_SECTORS * 512; sector_num += NBD_MAX_SECTORS; nb_sectors -= NBD_MAX_SECTORS; } return nbd_co_readv_1(bs, sector_num, nb_sectors, qiov, offset); } static int nbd_co_writev(BlockDriverState *bs, int64_t sector_num, int nb_sectors, QEMUIOVector *qiov) { int offset = 0; int ret; while (nb_sectors > NBD_MAX_SECTORS) { ret = nbd_co_writev_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset); if (ret < 0) { return ret; } offset += NBD_MAX_SECTORS * 512; sector_num += NBD_MAX_SECTORS; nb_sectors -= NBD_MAX_SECTORS; } return nbd_co_writev_1(bs, sector_num, nb_sectors, qiov, offset); } static int nbd_co_flush(BlockDriverState *bs) { BDRVNBDState *s = bs->opaque; struct nbd_request request; struct nbd_reply reply; ssize_t ret; if (!(s->nbdflags & NBD_FLAG_SEND_FLUSH)) { return 0; } request.type = NBD_CMD_FLUSH; if (s->nbdflags & NBD_FLAG_SEND_FUA) { request.type |= NBD_CMD_FLAG_FUA; } request.from = 0; request.len = 0; nbd_coroutine_start(s, &request); ret = nbd_co_send_request(s, &request, NULL, 0); if (ret < 0) { reply.error = -ret; } else { nbd_co_receive_reply(s, &request, &reply, NULL, 0); } nbd_coroutine_end(s, &request); return -reply.error; } static int nbd_co_discard(BlockDriverState *bs, int64_t sector_num, int nb_sectors) { BDRVNBDState *s = bs->opaque; struct nbd_request request; struct nbd_reply reply; ssize_t ret; if (!(s->nbdflags & NBD_FLAG_SEND_TRIM)) { return 0; } request.type = NBD_CMD_TRIM; request.from = sector_num * 512;; request.len = nb_sectors * 512; nbd_coroutine_start(s, &request); ret = nbd_co_send_request(s, &request, NULL, 0); if (ret < 0) { reply.error = -ret; } else { nbd_co_receive_reply(s, &request, &reply, NULL, 0); } nbd_coroutine_end(s, &request); return -reply.error; } static void nbd_close(BlockDriverState *bs) { BDRVNBDState *s = bs->opaque; g_free(s->export_name); g_free(s->host_spec); nbd_teardown_connection(bs); } static int64_t nbd_getlength(BlockDriverState *bs) { BDRVNBDState *s = bs->opaque; return s->size; } static BlockDriver bdrv_nbd = { .format_name = "nbd", .instance_size = sizeof(BDRVNBDState), .bdrv_file_open = nbd_open, .bdrv_co_readv = nbd_co_readv, .bdrv_co_writev = nbd_co_writev, .bdrv_close = nbd_close, .bdrv_co_flush_to_os = nbd_co_flush, .bdrv_co_discard = nbd_co_discard, .bdrv_getlength = nbd_getlength, .protocol_name = "nbd", }; static void bdrv_nbd_init(void) { bdrv_register(&bdrv_nbd); } block_init(bdrv_nbd_init);