1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * An implementation of the host initiated guest snapshot for Hyper-V. 4 * 5 * Copyright (C) 2013, Microsoft, Inc. 6 * Author : K. Y. Srinivasan <kys@microsoft.com> 7 */ 8 9 10 #include <sys/types.h> 11 #include <sys/poll.h> 12 #include <sys/ioctl.h> 13 #include <sys/stat.h> 14 #include <sys/sysmacros.h> 15 #include <fcntl.h> 16 #include <stdio.h> 17 #include <mntent.h> 18 #include <stdlib.h> 19 #include <unistd.h> 20 #include <string.h> 21 #include <ctype.h> 22 #include <errno.h> 23 #include <linux/fs.h> 24 #include <linux/major.h> 25 #include <linux/hyperv.h> 26 #include <syslog.h> 27 #include <getopt.h> 28 #include <stdbool.h> 29 #include <dirent.h> 30 31 /* Don't use syslog() in the function since that can cause write to disk */ 32 static int vss_do_freeze(char *dir, unsigned int cmd) 33 { 34 int ret, fd = open(dir, O_RDONLY); 35 36 if (fd < 0) 37 return 1; 38 39 ret = ioctl(fd, cmd, 0); 40 41 /* 42 * If a partition is mounted more than once, only the first 43 * FREEZE/THAW can succeed and the later ones will get 44 * EBUSY/EINVAL respectively: there could be 2 cases: 45 * 1) a user may mount the same partition to different directories 46 * by mistake or on purpose; 47 * 2) The subvolume of btrfs appears to have the same partition 48 * mounted more than once. 49 */ 50 if (ret) { 51 if ((cmd == FIFREEZE && errno == EBUSY) || 52 (cmd == FITHAW && errno == EINVAL)) { 53 close(fd); 54 return 0; 55 } 56 } 57 58 close(fd); 59 return !!ret; 60 } 61 62 static bool is_dev_loop(const char *blkname) 63 { 64 char *buffer; 65 DIR *dir; 66 struct dirent *entry; 67 bool ret = false; 68 69 buffer = malloc(PATH_MAX); 70 if (!buffer) { 71 syslog(LOG_ERR, "Can't allocate memory!"); 72 exit(1); 73 } 74 75 snprintf(buffer, PATH_MAX, "%s/loop", blkname); 76 if (!access(buffer, R_OK | X_OK)) { 77 ret = true; 78 goto free_buffer; 79 } else if (errno != ENOENT) { 80 syslog(LOG_ERR, "Can't access: %s; error:%d %s!", 81 buffer, errno, strerror(errno)); 82 } 83 84 snprintf(buffer, PATH_MAX, "%s/slaves", blkname); 85 dir = opendir(buffer); 86 if (!dir) { 87 if (errno != ENOENT) 88 syslog(LOG_ERR, "Can't opendir: %s; error:%d %s!", 89 buffer, errno, strerror(errno)); 90 goto free_buffer; 91 } 92 93 while ((entry = readdir(dir)) != NULL) { 94 if (strcmp(entry->d_name, ".") == 0 || 95 strcmp(entry->d_name, "..") == 0) 96 continue; 97 98 snprintf(buffer, PATH_MAX, "%s/slaves/%s", blkname, 99 entry->d_name); 100 if (is_dev_loop(buffer)) { 101 ret = true; 102 break; 103 } 104 } 105 closedir(dir); 106 free_buffer: 107 free(buffer); 108 return ret; 109 } 110 111 static int vss_operate(int operation) 112 { 113 char match[] = "/dev/"; 114 FILE *mounts; 115 struct mntent *ent; 116 struct stat sb; 117 char errdir[1024] = {0}; 118 char blkdir[23]; /* /sys/dev/block/XXX:XXX */ 119 unsigned int cmd; 120 int error = 0, root_seen = 0, save_errno = 0; 121 122 switch (operation) { 123 case VSS_OP_FREEZE: 124 cmd = FIFREEZE; 125 break; 126 case VSS_OP_THAW: 127 cmd = FITHAW; 128 break; 129 default: 130 return -1; 131 } 132 133 mounts = setmntent("/proc/mounts", "r"); 134 if (mounts == NULL) 135 return -1; 136 137 while ((ent = getmntent(mounts))) { 138 if (strncmp(ent->mnt_fsname, match, strlen(match))) 139 continue; 140 if (stat(ent->mnt_fsname, &sb)) { 141 syslog(LOG_ERR, "Can't stat: %s; error:%d %s!", 142 ent->mnt_fsname, errno, strerror(errno)); 143 } else { 144 sprintf(blkdir, "/sys/dev/block/%d:%d", 145 major(sb.st_rdev), minor(sb.st_rdev)); 146 if (is_dev_loop(blkdir)) 147 continue; 148 } 149 if (hasmntopt(ent, MNTOPT_RO) != NULL) 150 continue; 151 if (strcmp(ent->mnt_type, "vfat") == 0) 152 continue; 153 if (strcmp(ent->mnt_dir, "/") == 0) { 154 root_seen = 1; 155 continue; 156 } 157 error |= vss_do_freeze(ent->mnt_dir, cmd); 158 if (error && operation == VSS_OP_FREEZE) 159 goto err; 160 } 161 162 endmntent(mounts); 163 164 if (root_seen) { 165 error |= vss_do_freeze("/", cmd); 166 if (error && operation == VSS_OP_FREEZE) 167 goto err; 168 } 169 170 goto out; 171 err: 172 save_errno = errno; 173 if (ent) { 174 strncpy(errdir, ent->mnt_dir, sizeof(errdir)-1); 175 endmntent(mounts); 176 } 177 vss_operate(VSS_OP_THAW); 178 /* Call syslog after we thaw all filesystems */ 179 if (ent) 180 syslog(LOG_ERR, "FREEZE of %s failed; error:%d %s", 181 errdir, save_errno, strerror(save_errno)); 182 else 183 syslog(LOG_ERR, "FREEZE of / failed; error:%d %s", save_errno, 184 strerror(save_errno)); 185 out: 186 return error; 187 } 188 189 void print_usage(char *argv[]) 190 { 191 fprintf(stderr, "Usage: %s [options]\n" 192 "Options are:\n" 193 " -n, --no-daemon stay in foreground, don't daemonize\n" 194 " -h, --help print this help\n", argv[0]); 195 } 196 197 int main(int argc, char *argv[]) 198 { 199 int vss_fd, len; 200 int error; 201 struct pollfd pfd; 202 int op; 203 struct hv_vss_msg vss_msg[1]; 204 int daemonize = 1, long_index = 0, opt; 205 int in_handshake = 1; 206 __u32 kernel_modver; 207 208 static struct option long_options[] = { 209 {"help", no_argument, 0, 'h' }, 210 {"no-daemon", no_argument, 0, 'n' }, 211 {0, 0, 0, 0 } 212 }; 213 214 while ((opt = getopt_long(argc, argv, "hn", long_options, 215 &long_index)) != -1) { 216 switch (opt) { 217 case 'n': 218 daemonize = 0; 219 break; 220 case 'h': 221 print_usage(argv); 222 exit(0); 223 default: 224 print_usage(argv); 225 exit(EXIT_FAILURE); 226 } 227 } 228 229 if (daemonize && daemon(1, 0)) 230 return 1; 231 232 openlog("Hyper-V VSS", 0, LOG_USER); 233 syslog(LOG_INFO, "VSS starting; pid is:%d", getpid()); 234 235 vss_fd = open("/dev/vmbus/hv_vss", O_RDWR); 236 if (vss_fd < 0) { 237 syslog(LOG_ERR, "open /dev/vmbus/hv_vss failed; error: %d %s", 238 errno, strerror(errno)); 239 exit(EXIT_FAILURE); 240 } 241 /* 242 * Register ourselves with the kernel. 243 */ 244 vss_msg->vss_hdr.operation = VSS_OP_REGISTER1; 245 246 len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg)); 247 if (len < 0) { 248 syslog(LOG_ERR, "registration to kernel failed; error: %d %s", 249 errno, strerror(errno)); 250 close(vss_fd); 251 exit(EXIT_FAILURE); 252 } 253 254 pfd.fd = vss_fd; 255 256 while (1) { 257 pfd.events = POLLIN; 258 pfd.revents = 0; 259 260 if (poll(&pfd, 1, -1) < 0) { 261 syslog(LOG_ERR, "poll failed; error:%d %s", errno, strerror(errno)); 262 if (errno == EINVAL) { 263 close(vss_fd); 264 exit(EXIT_FAILURE); 265 } 266 else 267 continue; 268 } 269 270 len = read(vss_fd, vss_msg, sizeof(struct hv_vss_msg)); 271 272 if (in_handshake) { 273 if (len != sizeof(kernel_modver)) { 274 syslog(LOG_ERR, "invalid version negotiation"); 275 exit(EXIT_FAILURE); 276 } 277 kernel_modver = *(__u32 *)vss_msg; 278 in_handshake = 0; 279 syslog(LOG_INFO, "VSS: kernel module version: %d", 280 kernel_modver); 281 continue; 282 } 283 284 if (len != sizeof(struct hv_vss_msg)) { 285 syslog(LOG_ERR, "read failed; error:%d %s", 286 errno, strerror(errno)); 287 close(vss_fd); 288 return EXIT_FAILURE; 289 } 290 291 op = vss_msg->vss_hdr.operation; 292 error = HV_S_OK; 293 294 switch (op) { 295 case VSS_OP_FREEZE: 296 case VSS_OP_THAW: 297 error = vss_operate(op); 298 syslog(LOG_INFO, "VSS: op=%s: %s\n", 299 op == VSS_OP_FREEZE ? "FREEZE" : "THAW", 300 error ? "failed" : "succeeded"); 301 302 if (error) { 303 error = HV_E_FAIL; 304 syslog(LOG_ERR, "op=%d failed!", op); 305 syslog(LOG_ERR, "report it with these files:"); 306 syslog(LOG_ERR, "/etc/fstab and /proc/mounts"); 307 } 308 break; 309 case VSS_OP_HOT_BACKUP: 310 syslog(LOG_INFO, "VSS: op=CHECK HOT BACKUP\n"); 311 break; 312 default: 313 syslog(LOG_ERR, "Illegal op:%d\n", op); 314 } 315 vss_msg->error = error; 316 len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg)); 317 if (len != sizeof(struct hv_vss_msg)) { 318 syslog(LOG_ERR, "write failed; error: %d %s", errno, 319 strerror(errno)); 320 321 if (op == VSS_OP_FREEZE) 322 vss_operate(VSS_OP_THAW); 323 } 324 } 325 326 close(vss_fd); 327 exit(0); 328 } 329