src/lxc/storage/nbd.c

   1 /*
   2  * lxc: linux Container library
   3  *
   4  * (C) Copyright IBM Corp. 2007, 2008
   5  *
   6  * Authors:
   7  * Daniel Lezcano <daniel.lezcano at free.fr>
   8  *
   9  * This library is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public
  11  * License as published by the Free Software Foundation; either
  12  * version 2.1 of the License, or (at your option) any later version.
  13  *
  14  * This library is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  * Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public
  20  * License along with this library; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  22  */
  23
  24 #define _GNU_SOURCE
  25 #include <errno.h>
  26 #include <stdbool.h>
  27 #include <stdint.h>
  28 #include <stdio.h>
  29 #include <stdlib.h>
  30 #include <string.h>
  31 #include <sys/prctl.h>
  32 #include <sys/wait.h>
  33
  34 #include "log.h"
  35 #include "nbd.h"
  36 #include "storage.h"
  37 #include "storage_utils.h"
  38 #include "utils.h"
  39
  40 lxc_log_define(nbd, lxc);
  41
  42 struct nbd_attach_data {
  43         const char *nbd;
  44         const char *path;
  45 };
  46
  47 static bool clone_attach_nbd(const char *nbd, const char *path);
  48 static int do_attach_nbd(void *d);
  49 static bool nbd_busy(int idx);
  50 static void nbd_detach(const char *path);
  51 static int nbd_get_partition(const char *src);
  52 static bool wait_for_partition(const char *path);
  53
  54 bool attach_nbd(char *src, struct lxc_conf *conf)
  55 {
  56         char *orig = alloca(strlen(src)+1), *p, path[50];
  57         int i = 0;
  58
  59         strcpy(orig, src);
  60         /* if path is followed by a partition, drop that for now */
  61         p = strchr(orig, ':');
  62         if (p)
  63                 *p = '\0';
  64         while (1) {
  65                 sprintf(path, "/dev/nbd%d", i);
  66                 if (!file_exists(path))
  67                         return false;
  68                 if (nbd_busy(i)) {
  69                         i++;
  70                         continue;
  71                 }
  72                 if (!clone_attach_nbd(path, orig))
  73                         return false;
  74                 conf->nbd_idx = i;
  75                 return true;
  76         }
  77 }
  78
  79 void detach_nbd_idx(int idx)
  80 {
  81         int ret;
  82         char path[50];
  83
  84         ret = snprintf(path, 50, "/dev/nbd%d", idx);
  85         if (ret < 0 || ret >= 50)
  86                 return;
  87
  88         nbd_detach(path);
  89 }
  90
  91 int nbd_clonepaths(struct lxc_storage *orig, struct lxc_storage *new,
  92                    const char *oldname, const char *cname, const char *oldpath,
  93                    const char *lxcpath, int snap, uint64_t newsize,
  94                    struct lxc_conf *conf)
  95 {
  96         return -ENOSYS;
  97 }
  98
  99 int nbd_create(struct lxc_storage *bdev, const char *dest, const char *n,
 100                struct bdev_specs *specs)
 101 {
 102         return -ENOSYS;
 103 }
 104
 105 int nbd_destroy(struct lxc_storage *orig)
 106 {
 107         return -ENOSYS;
 108 }
 109
 110 bool nbd_detect(const char *path)
 111 {
 112         if (!strncmp(path, "nbd:", 4))
 113                 return true;
 114
 115         return false;
 116 }
 117
 118 int nbd_mount(struct lxc_storage *bdev)
 119 {
 120         int ret = -1, partition;
 121         char *src;
 122         char path[50];
 123
 124         if (strcmp(bdev->type, "nbd"))
 125                 return -22;
 126
 127         if (!bdev->src || !bdev->dest)
 128                 return -22;
 129
 130         /* nbd_idx should have been copied by bdev_init from the lxc_conf */
 131         if (bdev->nbd_idx < 0)
 132                 return -22;
 133
 134         src = lxc_storage_get_path(bdev->src, bdev->type);
 135         partition = nbd_get_partition(src);
 136         if (partition)
 137                 ret = snprintf(path, 50, "/dev/nbd%dp%d", bdev->nbd_idx,
 138                                 partition);
 139         else
 140                 ret = snprintf(path, 50, "/dev/nbd%d", bdev->nbd_idx);
 141         if (ret < 0 || ret >= 50) {
 142                 ERROR("Error setting up nbd device path");
 143                 return ret;
 144         }
 145
 146         /* It might take awhile for the partition files to show up */
 147         if (partition) {
 148                 if (!wait_for_partition(path))
 149                         return -2;
 150         }
 151         ret = mount_unknown_fs(path, bdev->dest, bdev->mntopts);
 152         if (ret < 0)
 153                 ERROR("Error mounting %s", bdev->src);
 154
 155         return ret;
 156 }
 157
 158 int nbd_umount(struct lxc_storage *bdev)
 159 {
 160         if (strcmp(bdev->type, "nbd"))
 161                 return -22;
 162
 163         if (!bdev->src || !bdev->dest)
 164                 return -22;
 165
 166         return umount(bdev->dest);
 167 }
 168
 169 bool requires_nbd(const char *path)
 170 {
 171         if (strncmp(path, "nbd:", 4) == 0)
 172                 return true;
 173         return false;
 174 }
 175
 176 static int do_attach_nbd(void *d)
 177 {
 178         struct nbd_attach_data *data = d;
 179         const char *nbd, *path;
 180         pid_t pid;
 181         sigset_t mask;
 182         int sfd;
 183         ssize_t s;
 184         struct signalfd_siginfo fdsi;
 185
 186         sigemptyset(&mask);
 187         sigaddset(&mask, SIGHUP);
 188         sigaddset(&mask, SIGCHLD);
 189
 190         nbd = data->nbd;
 191         path = data->path;
 192
 193         if (sigprocmask(SIG_BLOCK, &mask, NULL) == -1) {
 194                 SYSERROR("Error blocking signals for nbd watcher");
 195                 exit(1);
 196         }
 197
 198         sfd = signalfd(-1, &mask, 0);
 199         if (sfd == -1) {
 200                 SYSERROR("Error opening signalfd for nbd task");
 201                 exit(1);
 202         }
 203
 204         if (prctl(PR_SET_PDEATHSIG, SIGHUP, 0, 0, 0) < 0)
 205                 SYSERROR("Error setting parent death signal for nbd watcher");
 206
 207         pid = fork();
 208         if (pid) {
 209                 for (;;) {
 210                         s = read(sfd, &fdsi, sizeof(struct signalfd_siginfo));
 211                         if (s != sizeof(struct signalfd_siginfo))
 212                                 SYSERROR("Error reading from signalfd");
 213
 214                         if (fdsi.ssi_signo == SIGHUP) {
 215                                 /* container has exited */
 216                                 nbd_detach(nbd);
 217                                 exit(0);
 218                         } else if (fdsi.ssi_signo == SIGCHLD) {
 219                                 int status;
 220                                 /* If qemu-nbd fails, or is killed by a signal,
 221                                  * then exit */
 222                                 while (waitpid(-1, &status, WNOHANG) > 0) {
 223                                         if ((WIFEXITED(status) && WEXITSTATUS(status) != 0) ||
 224                                                         WIFSIGNALED(status)) {
 225                                                 nbd_detach(nbd);
 226                                                 exit(1);
 227                                         }
 228                                 }
 229                         }
 230                 }
 231         }
 232
 233         close(sfd);
 234         if (sigprocmask(SIG_UNBLOCK, &mask, NULL) == -1)
 235                 WARN("Warning: unblocking signals for nbd watcher");
 236
 237         execlp("qemu-nbd", "qemu-nbd", "-c", nbd, path, (char *)NULL);
 238         SYSERROR("Error executing qemu-nbd");
 239         exit(1);
 240 }
 241
 242 static bool clone_attach_nbd(const char *nbd, const char *path)
 243 {
 244         pid_t pid;
 245         struct nbd_attach_data data;
 246
 247         data.nbd = nbd;
 248         data.path = path;
 249
 250         pid = lxc_clone(do_attach_nbd, &data, CLONE_NEWPID);
 251         if (pid < 0)
 252                 return false;
 253         return true;
 254 }
 255
 256 static bool nbd_busy(int idx)
 257 {
 258         char path[100];
 259         int ret;
 260
 261         ret = snprintf(path, 100, "/sys/block/nbd%d/pid", idx);
 262         if (ret < 0 || ret >= 100)
 263                 return true;
 264         return file_exists(path);
 265 }
 266
 267 static void nbd_detach(const char *path)
 268 {
 269         int ret;
 270         pid_t pid = fork();
 271
 272         if (pid < 0) {
 273                 SYSERROR("Error forking to detach nbd");
 274                 return;
 275         }
 276         if (pid) {
 277                 ret = wait_for_pid(pid);
 278                 if (ret < 0)
 279                         ERROR("nbd disconnect returned an error");
 280                 return;
 281         }
 282         execlp("qemu-nbd", "qemu-nbd", "-d", path, (char *)NULL);
 283         SYSERROR("Error executing qemu-nbd");
 284         exit(1);
 285 }
 286
 287 /*
 288  * Pick the partition # off the end of a nbd:file:p
 289  * description.  Return 1-9 for the partition id, or 0
 290  * for no partition.
 291  */
 292 static int nbd_get_partition(const char *src)
 293 {
 294         char *p = strchr(src, ':');
 295         if (!p)
 296                 return 0;
 297         p = strchr(p+1, ':');
 298         if (!p)
 299                 return 0;
 300         p++;
 301         if (*p < '1' || *p > '9')
 302                 return 0;
 303         return *p - '0';
 304 }
 305
 306 static bool wait_for_partition(const char *path)
 307 {
 308         int count = 0;
 309         while (count < 5) {
 310                 if (file_exists(path))
 311                         return true;
 312                 sleep(1);
 313                 count++;
 314         }
 315         ERROR("Device %s did not show up after 5 seconds", path);
 316         return false;
 317 }