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 #ifndef HAVE_STRLCPY
  41 #include "include/strlcpy.h"
  42 #endif
  43
  44 lxc_log_define(nbd, lxc);
  45
  46 struct nbd_attach_data {
  47         const char *nbd;
  48         const char *path;
  49 };
  50
  51 static bool clone_attach_nbd(const char *nbd, const char *path);
  52 static int do_attach_nbd(void *d);
  53 static bool nbd_busy(int idx);
  54 static void nbd_detach(const char *path);
  55 static int nbd_get_partition(const char *src);
  56 static bool wait_for_partition(const char *path);
  57
  58 bool attach_nbd(char *src, struct lxc_conf *conf)
  59 {
  60         char *orig, *p, path[50];
  61         int i = 0;
  62         size_t len;
  63
  64         len = strlen(src);
  65         orig = alloca(len + 1);
  66         (void)strlcpy(orig, src, len + 1);
  67
  68         /* if path is followed by a partition, drop that for now */
  69         p = strchr(orig, ':');
  70         if (p)
  71                 *p = '\0';
  72         while (1) {
  73                 sprintf(path, "/dev/nbd%d", i);
  74                 if (!file_exists(path))
  75                         return false;
  76                 if (nbd_busy(i)) {
  77                         i++;
  78                         continue;
  79                 }
  80                 if (!clone_attach_nbd(path, orig))
  81                         return false;
  82                 conf->nbd_idx = i;
  83                 return true;
  84         }
  85 }
  86
  87 void detach_nbd_idx(int idx)
  88 {
  89         int ret;
  90         char path[50];
  91
  92         ret = snprintf(path, 50, "/dev/nbd%d", idx);
  93         if (ret < 0 || ret >= 50)
  94                 return;
  95
  96         nbd_detach(path);
  97 }
  98
  99 int nbd_clonepaths(struct lxc_storage *orig, struct lxc_storage *new,
 100                    const char *oldname, const char *cname, const char *oldpath,
 101                    const char *lxcpath, int snap, uint64_t newsize,
 102                    struct lxc_conf *conf)
 103 {
 104         return -ENOSYS;
 105 }
 106
 107 int nbd_create(struct lxc_storage *bdev, const char *dest, const char *n,
 108                struct bdev_specs *specs)
 109 {
 110         return -ENOSYS;
 111 }
 112
 113 int nbd_destroy(struct lxc_storage *orig)
 114 {
 115         return -ENOSYS;
 116 }
 117
 118 bool nbd_detect(const char *path)
 119 {
 120         if (!strncmp(path, "nbd:", 4))
 121                 return true;
 122
 123         return false;
 124 }
 125
 126 int nbd_mount(struct lxc_storage *bdev)
 127 {
 128         int ret = -1, partition;
 129         const char *src;
 130         char path[50];
 131
 132         if (strcmp(bdev->type, "nbd"))
 133                 return -22;
 134
 135         if (!bdev->src || !bdev->dest)
 136                 return -22;
 137
 138         /* nbd_idx should have been copied by bdev_init from the lxc_conf */
 139         if (bdev->nbd_idx < 0)
 140                 return -22;
 141
 142         src = lxc_storage_get_path(bdev->src, bdev->type);
 143         partition = nbd_get_partition(src);
 144         if (partition)
 145                 ret = snprintf(path, 50, "/dev/nbd%dp%d", bdev->nbd_idx,
 146                                 partition);
 147         else
 148                 ret = snprintf(path, 50, "/dev/nbd%d", bdev->nbd_idx);
 149         if (ret < 0 || ret >= 50) {
 150                 ERROR("Error setting up nbd device path");
 151                 return ret;
 152         }
 153
 154         /* It might take awhile for the partition files to show up */
 155         if (partition) {
 156                 if (!wait_for_partition(path))
 157                         return -2;
 158         }
 159         ret = mount_unknown_fs(path, bdev->dest, bdev->mntopts);
 160         if (ret < 0)
 161                 ERROR("Error mounting %s", bdev->src);
 162
 163         return ret;
 164 }
 165
 166 int nbd_umount(struct lxc_storage *bdev)
 167 {
 168         if (strcmp(bdev->type, "nbd"))
 169                 return -22;
 170
 171         if (!bdev->src || !bdev->dest)
 172                 return -22;
 173
 174         return umount(bdev->dest);
 175 }
 176
 177 bool requires_nbd(const char *path)
 178 {
 179         if (strncmp(path, "nbd:", 4) == 0)
 180                 return true;
 181         return false;
 182 }
 183
 184 static int do_attach_nbd(void *d)
 185 {
 186         struct nbd_attach_data *data = d;
 187         const char *nbd, *path;
 188         pid_t pid;
 189         sigset_t mask;
 190         int sfd;
 191         ssize_t s;
 192         struct signalfd_siginfo fdsi;
 193
 194         sigemptyset(&mask);
 195         sigaddset(&mask, SIGHUP);
 196         sigaddset(&mask, SIGCHLD);
 197
 198         nbd = data->nbd;
 199         path = data->path;
 200
 201         if (sigprocmask(SIG_BLOCK, &mask, NULL) == -1) {
 202                 SYSERROR("Error blocking signals for nbd watcher");
 203                 exit(1);
 204         }
 205
 206         sfd = signalfd(-1, &mask, 0);
 207         if (sfd == -1) {
 208                 SYSERROR("Error opening signalfd for nbd task");
 209                 exit(1);
 210         }
 211
 212         if (prctl(PR_SET_PDEATHSIG, prctl_arg(SIGHUP), prctl_arg(0),
 213                   prctl_arg(0), prctl_arg(0)) < 0)
 214                 SYSERROR("Error setting parent death signal for nbd watcher");
 215
 216         pid = fork();
 217         if (pid) {
 218                 for (;;) {
 219                         s = read(sfd, &fdsi, sizeof(struct signalfd_siginfo));
 220                         if (s != sizeof(struct signalfd_siginfo))
 221                                 SYSERROR("Error reading from signalfd");
 222
 223                         if (fdsi.ssi_signo == SIGHUP) {
 224                                 /* container has exited */
 225                                 nbd_detach(nbd);
 226                                 exit(0);
 227                         } else if (fdsi.ssi_signo == SIGCHLD) {
 228                                 int status;
 229                                 /* If qemu-nbd fails, or is killed by a signal,
 230                                  * then exit */
 231                                 while (waitpid(-1, &status, WNOHANG) > 0) {
 232                                         if ((WIFEXITED(status) && WEXITSTATUS(status) != 0) ||
 233                                                         WIFSIGNALED(status)) {
 234                                                 nbd_detach(nbd);
 235                                                 exit(1);
 236                                         }
 237                                 }
 238                         }
 239                 }
 240         }
 241
 242         close(sfd);
 243         if (sigprocmask(SIG_UNBLOCK, &mask, NULL) == -1)
 244                 WARN("Warning: unblocking signals for nbd watcher");
 245
 246         execlp("qemu-nbd", "qemu-nbd", "-c", nbd, path, (char *)NULL);
 247         SYSERROR("Error executing qemu-nbd");
 248         exit(1);
 249 }
 250
 251 static bool clone_attach_nbd(const char *nbd, const char *path)
 252 {
 253         pid_t pid;
 254         struct nbd_attach_data data;
 255
 256         data.nbd = nbd;
 257         data.path = path;
 258
 259         pid = lxc_clone(do_attach_nbd, &data, CLONE_NEWPID);
 260         if (pid < 0)
 261                 return false;
 262         return true;
 263 }
 264
 265 static bool nbd_busy(int idx)
 266 {
 267         char path[100];
 268         int ret;
 269
 270         ret = snprintf(path, 100, "/sys/block/nbd%d/pid", idx);
 271         if (ret < 0 || ret >= 100)
 272                 return true;
 273         return file_exists(path);
 274 }
 275
 276 static void nbd_detach(const char *path)
 277 {
 278         int ret;
 279         pid_t pid = fork();
 280
 281         if (pid < 0) {
 282                 SYSERROR("Error forking to detach nbd");
 283                 return;
 284         }
 285         if (pid) {
 286                 ret = wait_for_pid(pid);
 287                 if (ret < 0)
 288                         ERROR("nbd disconnect returned an error");
 289                 return;
 290         }
 291         execlp("qemu-nbd", "qemu-nbd", "-d", path, (char *)NULL);
 292         SYSERROR("Error executing qemu-nbd");
 293         exit(1);
 294 }
 295
 296 /*
 297  * Pick the partition # off the end of a nbd:file:p
 298  * description.  Return 1-9 for the partition id, or 0
 299  * for no partition.
 300  */
 301 static int nbd_get_partition(const char *src)
 302 {
 303         char *p = strchr(src, ':');
 304         if (!p)
 305                 return 0;
 306         p = strchr(p+1, ':');
 307         if (!p)
 308                 return 0;
 309         p++;
 310         if (*p < '1' || *p > '9')
 311                 return 0;
 312         return *p - '0';
 313 }
 314
 315 static bool wait_for_partition(const char *path)
 316 {
 317         int count = 0;
 318         while (count < 5) {
 319                 if (file_exists(path))
 320                         return true;
 321                 sleep(1);
 322                 count++;
 323         }
 324         ERROR("Device %s did not show up after 5 seconds", path);
 325         return false;
 326 }