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Linux/tools/hv/hv_vss_daemon.c

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  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 

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