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 <fcntl.h>
  26 #include <stdio.h>
  27 #include <mntent.h>
  28 #include <stdlib.h>
  29 #include <unistd.h>
  30 #include <string.h>
  31 #include <ctype.h>
  32 #include <errno.h>
  33 #include <linux/fs.h>
  34 #include <linux/major.h>
  35 #include <linux/hyperv.h>
  36 #include <syslog.h>
  37 #include <getopt.h>
  38
  39 /* Don't use syslog() in the function since that can cause write to disk */
  40 static int vss_do_freeze(char *dir, unsigned int cmd)
  41 {
  42         int ret, fd = open(dir, O_RDONLY);
  43
  44         if (fd < 0)
  45                 return 1;
  46
  47         ret = ioctl(fd, cmd, 0);
  48
  49         /*
  50          * If a partition is mounted more than once, only the first
  51          * FREEZE/THAW can succeed and the later ones will get
  52          * EBUSY/EINVAL respectively: there could be 2 cases:
  53          * 1) a user may mount the same partition to differnt directories
  54          *  by mistake or on purpose;
  55          * 2) The subvolume of btrfs appears to have the same partition
  56          * mounted more than once.
  57          */
  58         if (ret) {
  59                 if ((cmd == FIFREEZE && errno == EBUSY) ||
  60                     (cmd == FITHAW && errno == EINVAL)) {
  61                         close(fd);
  62                         return 0;
  63                 }
  64         }
  65
  66         close(fd);
  67         return !!ret;
  68 }
  69
  70 static int vss_operate(int operation)
  71 {
  72         char match[] = "/dev/";
  73         FILE *mounts;
  74         struct mntent *ent;
  75         struct stat sb;
  76         char errdir[1024] = {0};
  77         unsigned int cmd;
  78         int error = 0, root_seen = 0, save_errno = 0;
  79
  80         switch (operation) {
  81         case VSS_OP_FREEZE:
  82                 cmd = FIFREEZE;
  83                 break;
  84         case VSS_OP_THAW:
  85                 cmd = FITHAW;
  86                 break;
  87         default:
  88                 return -1;
  89         }
  90
  91         mounts = setmntent("/proc/mounts", "r");
  92         if (mounts == NULL)
  93                 return -1;
  94
  95         while ((ent = getmntent(mounts))) {
  96                 if (strncmp(ent->mnt_fsname, match, strlen(match)))
  97                         continue;
  98                 if (stat(ent->mnt_fsname, &sb) == -1)
  99                         continue;
 100                 if (S_ISBLK(sb.st_mode) && major(sb.st_rdev) == LOOP_MAJOR)
 101                         continue;
 102                 if (hasmntopt(ent, MNTOPT_RO) != NULL)
 103                         continue;
 104                 if (strcmp(ent->mnt_type, "vfat") == 0)
 105                         continue;
 106                 if (strcmp(ent->mnt_dir, "/") == 0) {
 107                         root_seen = 1;
 108                         continue;
 109                 }
 110                 error |= vss_do_freeze(ent->mnt_dir, cmd);
 111                 if (error && operation == VSS_OP_FREEZE)
 112                         goto err;
 113         }
 114
 115         endmntent(mounts);
 116
 117         if (root_seen) {
 118                 error |= vss_do_freeze("/", cmd);
 119                 if (error && operation == VSS_OP_FREEZE)
 120                         goto err;
 121         }
 122
 123         goto out;
 124 err:
 125         save_errno = errno;
 126         if (ent) {
 127                 strncpy(errdir, ent->mnt_dir, sizeof(errdir)-1);
 128                 endmntent(mounts);
 129         }
 130         vss_operate(VSS_OP_THAW);
 131         /* Call syslog after we thaw all filesystems */
 132         if (ent)
 133                 syslog(LOG_ERR, "FREEZE of %s failed; error:%d %s",
 134                        errdir, save_errno, strerror(save_errno));
 135         else
 136                 syslog(LOG_ERR, "FREEZE of / failed; error:%d %s", save_errno,
 137                        strerror(save_errno));
 138 out:
 139         return error;
 140 }
 141
 142 void print_usage(char *argv[])
 143 {
 144         fprintf(stderr, "Usage: %s [options]\n"
 145                 "Options are:\n"
 146                 "  -n, --no-daemon        stay in foreground, don't daemonize\n"
 147                 "  -h, --help             print this help\n", argv[0]);
 148 }
 149
 150 int main(int argc, char *argv[])
 151 {
 152         int vss_fd, len;
 153         int error;
 154         struct pollfd pfd;
 155         int     op;
 156         struct hv_vss_msg vss_msg[1];
 157         int daemonize = 1, long_index = 0, opt;
 158         int in_handshake = 1;
 159         __u32 kernel_modver;
 160
 161         static struct option long_options[] = {
 162                 {"help",        no_argument,       0,  'h' },
 163                 {"no-daemon",   no_argument,       0,  'n' },
 164                 {0,             0,                 0,  0   }
 165         };
 166
 167         while ((opt = getopt_long(argc, argv, "hn", long_options,
 168                                   &long_index)) != -1) {
 169                 switch (opt) {
 170                 case 'n':
 171                         daemonize = 0;
 172                         break;
 173                 case 'h':
 174                 default:
 175                         print_usage(argv);
 176                         exit(EXIT_FAILURE);
 177                 }
 178         }
 179
 180         if (daemonize && daemon(1, 0))
 181                 return 1;
 182
 183         openlog("Hyper-V VSS", 0, LOG_USER);
 184         syslog(LOG_INFO, "VSS starting; pid is:%d", getpid());
 185
 186         vss_fd = open("/dev/vmbus/hv_vss", O_RDWR);
 187         if (vss_fd < 0) {
 188                 syslog(LOG_ERR, "open /dev/vmbus/hv_vss failed; error: %d %s",
 189                        errno, strerror(errno));
 190                 exit(EXIT_FAILURE);
 191         }
 192         /*
 193          * Register ourselves with the kernel.
 194          */
 195         vss_msg->vss_hdr.operation = VSS_OP_REGISTER1;
 196
 197         len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
 198         if (len < 0) {
 199                 syslog(LOG_ERR, "registration to kernel failed; error: %d %s",
 200                        errno, strerror(errno));
 201                 close(vss_fd);
 202                 exit(EXIT_FAILURE);
 203         }
 204
 205         pfd.fd = vss_fd;
 206
 207         while (1) {
 208                 pfd.events = POLLIN;
 209                 pfd.revents = 0;
 210
 211                 if (poll(&pfd, 1, -1) < 0) {
 212                         syslog(LOG_ERR, "poll failed; error:%d %s", errno, strerror(errno));
 213                         if (errno == EINVAL) {
 214                                 close(vss_fd);
 215                                 exit(EXIT_FAILURE);
 216                         }
 217                         else
 218                                 continue;
 219                 }
 220
 221                 len = read(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
 222
 223                 if (in_handshake) {
 224                         if (len != sizeof(kernel_modver)) {
 225                                 syslog(LOG_ERR, "invalid version negotiation");
 226                                 exit(EXIT_FAILURE);
 227                         }
 228                         kernel_modver = *(__u32 *)vss_msg;
 229                         in_handshake = 0;
 230                         syslog(LOG_INFO, "VSS: kernel module version: %d",
 231                                kernel_modver);
 232                         continue;
 233                 }
 234
 235                 if (len != sizeof(struct hv_vss_msg)) {
 236                         syslog(LOG_ERR, "read failed; error:%d %s",
 237                                errno, strerror(errno));
 238                         close(vss_fd);
 239                         return EXIT_FAILURE;
 240                 }
 241
 242                 op = vss_msg->vss_hdr.operation;
 243                 error =  HV_S_OK;
 244
 245                 switch (op) {
 246                 case VSS_OP_FREEZE:
 247                 case VSS_OP_THAW:
 248                         error = vss_operate(op);
 249                         syslog(LOG_INFO, "VSS: op=%s: %s\n",
 250                                 op == VSS_OP_FREEZE ? "FREEZE" : "THAW",
 251                                 error ? "failed" : "succeeded");
 252
 253                         if (error) {
 254                                 error = HV_E_FAIL;
 255                                 syslog(LOG_ERR, "op=%d failed!", op);
 256                                 syslog(LOG_ERR, "report it with these files:");
 257                                 syslog(LOG_ERR, "/etc/fstab and /proc/mounts");
 258                         }
 259                         break;
 260                 case VSS_OP_HOT_BACKUP:
 261                         syslog(LOG_INFO, "VSS: op=CHECK HOT BACKUP\n");
 262                         break;
 263                 default:
 264                         syslog(LOG_ERR, "Illegal op:%d\n", op);
 265                 }
 266                 vss_msg->error = error;
 267                 len = write(vss_fd, vss_msg, sizeof(struct hv_vss_msg));
 268                 if (len != sizeof(struct hv_vss_msg)) {
 269                         syslog(LOG_ERR, "write failed; error: %d %s", errno,
 270                                strerror(errno));
 271
 272                         if (op == VSS_OP_FREEZE)
 273                                 vss_operate(VSS_OP_THAW);
 274                 }
 275         }
 276
 277         close(vss_fd);
 278         exit(0);
 279 }