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1// SPDX-License-Identifier: GPL-2.0-only2/*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 31static bool fs_frozen;32 33/* Don't use syslog() in the function since that can cause write to disk */34static int vss_do_freeze(char *dir, unsigned int cmd)35{36 int ret, fd = open(dir, O_RDONLY);37 38 if (fd < 0)39 return 1;40 41 ret = ioctl(fd, cmd, 0);42 43 /*44 * If a partition is mounted more than once, only the first45 * FREEZE/THAW can succeed and the later ones will get46 * EBUSY/EINVAL respectively: there could be 2 cases:47 * 1) a user may mount the same partition to different directories48 * by mistake or on purpose;49 * 2) The subvolume of btrfs appears to have the same partition50 * mounted more than once.51 */52 if (ret) {53 if ((cmd == FIFREEZE && errno == EBUSY) ||54 (cmd == FITHAW && errno == EINVAL)) {55 close(fd);56 return 0;57 }58 }59 60 close(fd);61 return !!ret;62}63 64static bool is_dev_loop(const char *blkname)65{66 char *buffer;67 DIR *dir;68 struct dirent *entry;69 bool ret = false;70 71 buffer = malloc(PATH_MAX);72 if (!buffer) {73 syslog(LOG_ERR, "Can't allocate memory!");74 exit(1);75 }76 77 snprintf(buffer, PATH_MAX, "%s/loop", blkname);78 if (!access(buffer, R_OK | X_OK)) {79 ret = true;80 goto free_buffer;81 } else if (errno != ENOENT) {82 syslog(LOG_ERR, "Can't access: %s; error:%d %s!",83 buffer, errno, strerror(errno));84 }85 86 snprintf(buffer, PATH_MAX, "%s/slaves", blkname);87 dir = opendir(buffer);88 if (!dir) {89 if (errno != ENOENT)90 syslog(LOG_ERR, "Can't opendir: %s; error:%d %s!",91 buffer, errno, strerror(errno));92 goto free_buffer;93 }94 95 while ((entry = readdir(dir)) != NULL) {96 if (strcmp(entry->d_name, ".") == 0 ||97 strcmp(entry->d_name, "..") == 0)98 continue;99 100 snprintf(buffer, PATH_MAX, "%s/slaves/%s", blkname,101 entry->d_name);102 if (is_dev_loop(buffer)) {103 ret = true;104 break;105 }106 }107 closedir(dir);108free_buffer:109 free(buffer);110 return ret;111}112 113static int vss_operate(int operation)114{115 char match[] = "/dev/";116 FILE *mounts;117 struct mntent *ent;118 struct stat sb;119 char errdir[1024] = {0};120 char blkdir[23]; /* /sys/dev/block/XXX:XXX */121 unsigned int cmd;122 int error = 0, root_seen = 0, save_errno = 0;123 124 switch (operation) {125 case VSS_OP_FREEZE:126 cmd = FIFREEZE;127 break;128 case VSS_OP_THAW:129 cmd = FITHAW;130 break;131 default:132 return -1;133 }134 135 mounts = setmntent("/proc/mounts", "r");136 if (mounts == NULL)137 return -1;138 139 while ((ent = getmntent(mounts))) {140 if (strncmp(ent->mnt_fsname, match, strlen(match)))141 continue;142 if (stat(ent->mnt_fsname, &sb)) {143 syslog(LOG_ERR, "Can't stat: %s; error:%d %s!",144 ent->mnt_fsname, errno, strerror(errno));145 } else {146 sprintf(blkdir, "/sys/dev/block/%d:%d",147 major(sb.st_rdev), minor(sb.st_rdev));148 if (is_dev_loop(blkdir))149 continue;150 }151 if (hasmntopt(ent, MNTOPT_RO) != NULL)152 continue;153 if (strcmp(ent->mnt_type, "vfat") == 0)154 continue;155 if (strcmp(ent->mnt_dir, "/") == 0) {156 root_seen = 1;157 continue;158 }159 error |= vss_do_freeze(ent->mnt_dir, cmd);160 if (operation == VSS_OP_FREEZE) {161 if (error)162 goto err;163 fs_frozen = true;164 }165 }166 167 endmntent(mounts);168 169 if (root_seen) {170 error |= vss_do_freeze("/", cmd);171 if (operation == VSS_OP_FREEZE) {172 if (error)173 goto err;174 fs_frozen = true;175 }176 }177 178 if (operation == VSS_OP_THAW && !error)179 fs_frozen = false;180 181 goto out;182err:183 save_errno = errno;184 if (ent) {185 strncpy(errdir, ent->mnt_dir, sizeof(errdir)-1);186 endmntent(mounts);187 }188 vss_operate(VSS_OP_THAW);189 fs_frozen = false;190 /* Call syslog after we thaw all filesystems */191 if (ent)192 syslog(LOG_ERR, "FREEZE of %s failed; error:%d %s",193 errdir, save_errno, strerror(save_errno));194 else195 syslog(LOG_ERR, "FREEZE of / failed; error:%d %s", save_errno,196 strerror(save_errno));197out:198 return error;199}200 201void print_usage(char *argv[])202{203 fprintf(stderr, "Usage: %s [options]\n"204 "Options are:\n"205 " -n, --no-daemon stay in foreground, don't daemonize\n"206 " -h, --help print this help\n", argv[0]);207}208 209int main(int argc, char *argv[])210{211 int vss_fd = -1, len;212 int error;213 struct pollfd pfd;214 int op;215 struct hv_vss_msg vss_msg[1];216 int daemonize = 1, long_index = 0, opt;217 int in_handshake;218 __u32 kernel_modver;219 220 static struct option long_options[] = {221 {"help", no_argument, 0, 'h' },222 {"no-daemon", no_argument, 0, 'n' },223 {0, 0, 0, 0 }224 };225 226 while ((opt = getopt_long(argc, argv, "hn", long_options,227 &long_index)) != -1) {228 switch (opt) {229 case 'n':230 daemonize = 0;231 break;232 case 'h':233 print_usage(argv);234 exit(0);235 default:236 print_usage(argv);237 exit(EXIT_FAILURE);238 }239 }240 241 if (daemonize && daemon(1, 0))242 return 1;243 244 openlog("Hyper-V VSS", 0, LOG_USER);245 syslog(LOG_INFO, "VSS starting; pid is:%d", getpid());246 247reopen_vss_fd:248 if (vss_fd != -1)249 close(vss_fd);250 if (fs_frozen) {251 if (vss_operate(VSS_OP_THAW) || fs_frozen) {252 syslog(LOG_ERR, "failed to thaw file system: err=%d",253 errno);254 exit(EXIT_FAILURE);255 }256 }257 258 in_handshake = 1;259 vss_fd = open("/dev/vmbus/hv_vss", O_RDWR);260 if (vss_fd < 0) {261 syslog(LOG_ERR, "open /dev/vmbus/hv_vss failed; error: %d %s",262 errno, strerror(errno));263 exit(EXIT_FAILURE);264 }265 /*266 * Register ourselves with the kernel.267 */268 vss_msg->vss_hdr.operation = VSS_OP_REGISTER1;269 270 len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg));271 if (len < 0) {272 syslog(LOG_ERR, "registration to kernel failed; error: %d %s",273 errno, strerror(errno));274 close(vss_fd);275 exit(EXIT_FAILURE);276 }277 278 pfd.fd = vss_fd;279 280 while (1) {281 pfd.events = POLLIN;282 pfd.revents = 0;283 284 if (poll(&pfd, 1, -1) < 0) {285 syslog(LOG_ERR, "poll failed; error:%d %s", errno, strerror(errno));286 if (errno == EINVAL) {287 close(vss_fd);288 exit(EXIT_FAILURE);289 }290 else291 continue;292 }293 294 len = read(vss_fd, vss_msg, sizeof(struct hv_vss_msg));295 296 if (in_handshake) {297 if (len != sizeof(kernel_modver)) {298 syslog(LOG_ERR, "invalid version negotiation");299 exit(EXIT_FAILURE);300 }301 kernel_modver = *(__u32 *)vss_msg;302 in_handshake = 0;303 syslog(LOG_INFO, "VSS: kernel module version: %d",304 kernel_modver);305 continue;306 }307 308 if (len != sizeof(struct hv_vss_msg)) {309 syslog(LOG_ERR, "read failed; error:%d %s",310 errno, strerror(errno));311 goto reopen_vss_fd;312 }313 314 op = vss_msg->vss_hdr.operation;315 error = HV_S_OK;316 317 switch (op) {318 case VSS_OP_FREEZE:319 case VSS_OP_THAW:320 error = vss_operate(op);321 syslog(LOG_INFO, "VSS: op=%s: %s\n",322 op == VSS_OP_FREEZE ? "FREEZE" : "THAW",323 error ? "failed" : "succeeded");324 325 if (error) {326 error = HV_E_FAIL;327 syslog(LOG_ERR, "op=%d failed!", op);328 syslog(LOG_ERR, "report it with these files:");329 syslog(LOG_ERR, "/etc/fstab and /proc/mounts");330 }331 break;332 case VSS_OP_HOT_BACKUP:333 syslog(LOG_INFO, "VSS: op=CHECK HOT BACKUP\n");334 break;335 default:336 syslog(LOG_ERR, "Illegal op:%d\n", op);337 }338 339 /*340 * The write() may return an error due to the faked VSS_OP_THAW341 * message upon hibernation. Ignore the error by resetting the342 * dev file, i.e. closing and re-opening it.343 */344 vss_msg->error = error;345 len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg));346 if (len != sizeof(struct hv_vss_msg)) {347 syslog(LOG_ERR, "write failed; error: %d %s", errno,348 strerror(errno));349 goto reopen_vss_fd;350 }351 }352 353 close(vss_fd);354 exit(0);355}356