tools/hv/hv_vss_daemon.c

   1 /*
   2  * An implementation of the host initiated guest snapshot for Hyper-V.
   3  *
   4  *
   5  * Copyright (C) 2013, Microsoft, Inc.
   6  * Author : K. Y. Srinivasan <kys@microsoft.com>
   7  *
   8  * This program is free software; you can redistribute it and/or modify it
   9  * under the terms of the GNU General Public License version 2 as published
  10  * by the Free Software Foundation.
  11  *
  12  * This program is distributed in the hope that it will be useful, but
  13  * WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
  15  * NON INFRINGEMENT.  See the GNU General Public License for more
  16  * details.
  17  *
  18  */
  19
  20
  21 #include <sys/types.h>
  22 #include <sys/poll.h>
  23 #include <sys/ioctl.h>
  24 #include <sys/stat.h>
  25 #include <sys/sysmacros.h>
  26 #include <fcntl.h>
  27 #include <stdio.h>
  28 #include <mntent.h>
  29 #include <stdlib.h>
  30 #include <unistd.h>
  31 #include <string.h>
  32 #include <ctype.h>
  33 #include <errno.h>
  34 #include <linux/fs.h>
  35 #include <linux/major.h>
  36 #include <linux/hyperv.h>
  37 #include <syslog.h>
  38 #include <getopt.h>
  39 #include <stdbool.h>
  40 #include <dirent.h>
  41
  42 /* Don't use syslog() in the function since that can cause write to disk */
  43 static int vss_do_freeze(char *dir, unsigned int cmd)
  44 {
  45         int ret, fd = open(dir, O_RDONLY);
  46
  47         if (fd < 0)
  48                 return 1;
  49
  50         ret = ioctl(fd, cmd, 0);
  51
  52         /*
  53          * If a partition is mounted more than once, only the first
  54          * FREEZE/THAW can succeed and the later ones will get
  55          * EBUSY/EINVAL respectively: there could be 2 cases:
  56          * 1) a user may mount the same partition to differnt directories
  57          *  by mistake or on purpose;
  58          * 2) The subvolume of btrfs appears to have the same partition
  59          * mounted more than once.
  60          */
  61         if (ret) {
  62                 if ((cmd == FIFREEZE && errno == EBUSY) ||
  63                     (cmd == FITHAW && errno == EINVAL)) {
  64                         close(fd);
  65                         return 0;
  66                 }
  67         }
  68
  69         close(fd);
  70         return !!ret;
  71 }
  72
  73 static bool is_dev_loop(const char *blkname)
  74 {
  75         char *buffer;
  76         DIR *dir;
  77         struct dirent *entry;
  78         bool ret = false;
  79
  80         buffer = malloc(PATH_MAX);
  81         if (!buffer) {
  82                 syslog(LOG_ERR, "Can't allocate memory!");
  83                 exit(1);
  84         }
  85
  86         snprintf(buffer, PATH_MAX, "%s/loop", blkname);
  87         if (!access(buffer, R_OK | X_OK)) {
  88                 ret = true;
  89                 goto free_buffer;
  90         } else if (errno != ENOENT) {
  91                 syslog(LOG_ERR, "Can't access: %s; error:%d %s!",
  92                        buffer, errno, strerror(errno));
  93         }
  94
  95         snprintf(buffer, PATH_MAX, "%s/slaves", blkname);
  96         dir = opendir(buffer);
  97         if (!dir) {
  98                 if (errno != ENOENT)
  99                         syslog(LOG_ERR, "Can't opendir: %s; error:%d %s!",
 100                                buffer, errno, strerror(errno));
 101                 goto free_buffer;
 102         }
 103
 104         while ((entry = readdir(dir)) != NULL) {
 105                 if (strcmp(entry->d_name, ".") == 0 ||
 106                     strcmp(entry->d_name, "..") == 0)
 107                         continue;
 108
 109                 snprintf(buffer, PATH_MAX, "%s/slaves/%s", blkname,
 110                          entry->d_name);
 111                 if (is_dev_loop(buffer)) {
 112                         ret = true;
 113                         break;
 114                 }
 115         }
 116         closedir(dir);
 117 free_buffer:
 118         free(buffer);
 119         return ret;
 120 }
 121
 122 static int vss_operate(int operation)
 123 {
 124         char match[] = "/dev/";
 125         FILE *mounts;
 126         struct mntent *ent;
 127         struct stat sb;
 128         char errdir[1024] = {0};
 129         char blkdir[23]; /* /sys/dev/block/XXX:XXX */
 130         unsigned int cmd;
 131         int error = 0, root_seen = 0, save_errno = 0;
 132
 133         switch (operation) {
 134         case VSS_OP_FREEZE:
 135                 cmd = FIFREEZE;
 136                 break;
 137         case VSS_OP_THAW:
 138                 cmd = FITHAW;
 139                 break;
 140         default:
 141                 return -1;
 142         }
 143
 144         mounts = setmntent("/proc/mounts", "r");
 145         if (mounts == NULL)
 146                 return -1;
 147
 148         while ((ent = getmntent(mounts))) {
 149                 if (strncmp(ent->mnt_fsname, match, strlen(match)))
 150                         continue;
 151                 if (stat(ent->mnt_fsname, &sb)) {
 152                         syslog(LOG_ERR, "Can't stat: %s; error:%d %s!",
 153                                ent->mnt_fsname, errno, strerror(errno));
 154                 } else {
 155                         sprintf(blkdir, "/sys/dev/block/%d:%d",
 156                                 major(sb.st_rdev), minor(sb.st_rdev));
 157                         if (is_dev_loop(blkdir))
 158                                 continue;
 159                 }
 160                 if (hasmntopt(ent, MNTOPT_RO) != NULL)
 161                         continue;
 162                 if (strcmp(ent->mnt_type, "vfat") == 0)
 163                         continue;
 164                 if (strcmp(ent->mnt_dir, "/") == 0) {
 165                         root_seen = 1;
 166                         continue;
 167                 }
 168                 error |= vss_do_freeze(ent->mnt_dir, cmd);
 169                 if (error && operation == VSS_OP_FREEZE)
 170                         goto err;
 171         }
 172
 173         endmntent(mounts);
 174
 175         if (root_seen) {
 176                 error |= vss_do_freeze("/", cmd);
 177                 if (error && operation == VSS_OP_FREEZE)
 178                         goto err;
 179         }
 180
 181         goto out;
 182 err:
 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         /* Call syslog after we thaw all filesystems */
 190         if (ent)
 191                 syslog(LOG_ERR, "FREEZE of %s failed; error:%d %s",
 192                        errdir, save_errno, strerror(save_errno));
 193         else
 194                 syslog(LOG_ERR, "FREEZE of / failed; error:%d %s", save_errno,
 195                        strerror(save_errno));
 196 out:
 197         return error;
 198 }
 199
 200 void print_usage(char *argv[])
 201 {
 202         fprintf(stderr, "Usage: %s [options]\n"
 203                 "Options are:\n"
 204                 "  -n, --no-daemon        stay in foreground, don't daemonize\n"
 205                 "  -h, --help             print this help\n", argv[0]);
 206 }
 207
 208 int main(int argc, char *argv[])
 209 {
 210         int vss_fd, len;
 211         int error;
 212         struct pollfd pfd;
 213         int     op;
 214         struct hv_vss_msg vss_msg[1];
 215         int daemonize = 1, long_index = 0, opt;
 216         int in_handshake = 1;
 217         __u32 kernel_modver;
 218
 219         static struct option long_options[] = {
 220                 {"help",        no_argument,       0,  'h' },
 221                 {"no-daemon",   no_argument,       0,  'n' },
 222                 {0,             0,                 0,  0   }
 223         };
 224
 225         while ((opt = getopt_long(argc, argv, "hn", long_options,
 226                                   &long_index)) != -1) {
 227                 switch (opt) {
 228                 case 'n':
 229                         daemonize = 0;
 230                         break;
 231                 case 'h':
 232                 default:
 233                         print_usage(argv);
 234                         exit(EXIT_FAILURE);
 235                 }
 236         }
 237
 238         if (daemonize && daemon(1, 0))
 239                 return 1;
 240
 241         openlog("Hyper-V VSS", 0, LOG_USER);
 242         syslog(LOG_INFO, "VSS starting; pid is:%d", getpid());
 243
 244         vss_fd = open("/dev/vmbus/hv_vss", O_RDWR);
 245         if (vss_fd < 0) {
 246                 syslog(LOG_ERR, "open /dev/vmbus/hv_vss failed; error: %d %s",
 247                        errno, strerror(errno));
 248                 exit(EXIT_FAILURE);
 249         }
 250         /*
 251          * Register ourselves with the kernel.
 252          */
 253         vss_msg->vss_hdr.operation = VSS_OP_REGISTER1;
 254
 255         len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
 256         if (len < 0) {
 257                 syslog(LOG_ERR, "registration to kernel failed; error: %d %s",
 258                        errno, strerror(errno));
 259                 close(vss_fd);
 260                 exit(EXIT_FAILURE);
 261         }
 262
 263         pfd.fd = vss_fd;
 264
 265         while (1) {
 266                 pfd.events = POLLIN;
 267                 pfd.revents = 0;
 268
 269                 if (poll(&pfd, 1, -1) < 0) {
 270                         syslog(LOG_ERR, "poll failed; error:%d %s", errno, strerror(errno));
 271                         if (errno == EINVAL) {
 272                                 close(vss_fd);
 273                                 exit(EXIT_FAILURE);
 274                         }
 275                         else
 276                                 continue;
 277                 }
 278
 279                 len = read(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
 280
 281                 if (in_handshake) {
 282                         if (len != sizeof(kernel_modver)) {
 283                                 syslog(LOG_ERR, "invalid version negotiation");
 284                                 exit(EXIT_FAILURE);
 285                         }
 286                         kernel_modver = *(__u32 *)vss_msg;
 287                         in_handshake = 0;
 288                         syslog(LOG_INFO, "VSS: kernel module version: %d",
 289                                kernel_modver);
 290                         continue;
 291                 }
 292
 293                 if (len != sizeof(struct hv_vss_msg)) {
 294                         syslog(LOG_ERR, "read failed; error:%d %s",
 295                                errno, strerror(errno));
 296                         close(vss_fd);
 297                         return EXIT_FAILURE;
 298                 }
 299
 300                 op = vss_msg->vss_hdr.operation;
 301                 error =  HV_S_OK;
 302
 303                 switch (op) {
 304                 case VSS_OP_FREEZE:
 305                 case VSS_OP_THAW:
 306                         error = vss_operate(op);
 307                         syslog(LOG_INFO, "VSS: op=%s: %s\n",
 308                                 op == VSS_OP_FREEZE ? "FREEZE" : "THAW",
 309                                 error ? "failed" : "succeeded");
 310
 311                         if (error) {
 312                                 error = HV_E_FAIL;
 313                                 syslog(LOG_ERR, "op=%d failed!", op);
 314                                 syslog(LOG_ERR, "report it with these files:");
 315                                 syslog(LOG_ERR, "/etc/fstab and /proc/mounts");
 316                         }
 317                         break;
 318                 case VSS_OP_HOT_BACKUP:
 319                         syslog(LOG_INFO, "VSS: op=CHECK HOT BACKUP\n");
 320                         break;
 321                 default:
 322                         syslog(LOG_ERR, "Illegal op:%d\n", op);
 323                 }
 324                 vss_msg->error = error;
 325                 len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
 326                 if (len != sizeof(struct hv_vss_msg)) {
 327                         syslog(LOG_ERR, "write failed; error: %d %s", errno,
 328                                strerror(errno));
 329
 330                         if (op == VSS_OP_FREEZE)
 331                                 vss_operate(VSS_OP_THAW);
 332                 }
 333         }
 334
 335         close(vss_fd);
 336         exit(0);
 337 }